Polarization is a crucial factor in shaping and stabilizing mode-locking pulses. We develop an orthogonally polarized numerical modeling of passive mode-locked graphene fiber lasers for generating orthogonally polarized dissipative solitons (DSs). The focus is on analyzing the influence of orthogonal polarization in this net-normal dispersion birefringent cavity caused by the polarization-dependent graphene microfiber saturable absorber. The research results demonstrate that the recovery time of such saturable absorbers significantly affects the characteristics of the orthogonally polarized DSs’ output pulses, including energy, pulse width, time-bandwidth product, and chirps. Results show that its recovery time of 120 fs is optimal, producing two orthogonally polarized narrow dissipative soliton pulses with large chirps of about 7.47 ps and 8.06 ps. This has significant implications for the development of compact, high-power, polarized dissipative soliton fiber laser systems.

The TFT-LCD industry is moving towards high efficiency and low costs. During the manufacturing process, it has been found that various photoresists require different vacuum drying times. To reduce manufacturing time and increase panel yields, clarifying the factors that can influence and reduce the vacuum time is necessary. This paper explored the relationship between pumping time and the properties of photoresist materials. It finds that the thermal stability of the photoresist has a negligible relationship with the pumping time. The compactness and hydrophobicity of the photoresist correlated strongly with the vacuum drying time. High compactness and high hydrophobicity can effectively prevent water vapor intrusion and storage in the photoresist during fabrication and consequently reduce pumping times. Overall, this work could guide the future development of new photoresists for the TFT-LCD industry.

A photoelectrical parameters test system for testing CCD and electron-multiplying charge-coupled device (EMCCD) chips is designed. The test system has automatic and manual modes, and it can test the dark currents, the output amplifier’s responsivity, charge transfer efficiency, charge capacity and other parameters. According to different specifications and structures of CCD/EMCCD devices, we complete the parameter test of wafer or packaged product. The developed system can be used for the testing and sorting for 576 × 288, 640 × 512, 768 × 576, 1024 × 1024, 1280 × 1024 CCD and EMCCD chips.

Broadband absorption performance in resistive metamaterial absorbers (MA) has always been disturbed by its ohmic sheet element. We propose a comprehensive scheme based on integrating resistive MA and plasmonic structure (PS) to enhance the stable absorption performance. Theoretical investigation indicated that the PS can inspire multi-resonance based on dispersion engineering, and that the localized electric field takes effect on the surface of the ohmic sheet accordingly. Simulation and experimental measurement demonstrated that the proposed resistive plasmonic absorbing structures (PAS) can achieve stable and highly efficient absorption within the frequency band from 7.8 to 40.0 GHz with the ohmic sheet ranging from 100 to 250 Ω/sq. In conclusion, the proposed integration of PS and resistive MA provides an efficient pathway to optimize performance for various applications.

An optical fiber magnetic field sensor is proposed and experimentally demonstrated by using a U-shaped cavity based on in-fiber Mach-Zehnder interferometer (MZI) coated with magnetic fluid (MF). The magnetic field sensor is manufactured by splicing a section of single-mode fiber (SMF) between two sections of SMF with designed fiber geometric relationships. As the geometric symmetry MZI is strongly sensitive to the surrounding refractive index (RI) with a high sensitivity up to -13588 nm/RIU and MF’s RI is sensitive to magnetic field, the magnetic field sensing function of the proposed structure is realized. The results show that the magnetic field sensitivity reaches as high as 137 pm/Oe, and the magnetic field range is almost linear from 0 to 250 Oe. The proposed magnetic field sensor has the advantages of small size, low cost, easy to manufacture, robustness, high sensitivity, good repeatability and easy to integrate with fiber optic systems.

Trace gases, as important constituents of the atmosphere, play an important role in the ecology of the planet. In order to realize the requirements of wide-band, hyperspectral and all-weather continuous measurement, a hyperspectral imaging spectrometer operating in occultation detection mode is designed in this paper. The system is a dual-channel structure with a common slit, the UV-visible channel adopts a single concave grating, and the infrared channel adopts a structure combining Littrow and immersion grating, which effectively reduces the volume. The software is used to optimize the optical structure, and the optimization results show that the spectrometer operates in the range of 250-952 nm wavelengths, of which the UV-visible channel operates in the wavelength range of 250-675 nm, the spectral resolution is better than 1 nm, the MTFs are all higher than 0.58 at a Nyquist frequency of 20 lp/mm, and the RMS values at various wavelengths of the full-field-of-view are all less than 21 μm; the infrared channel operates in the wavelength band of 756-952 nm, the spectral resolution is better than 0.2 nm, the MTF is higher than 0.76 at the Nyquist frequency of 20 lp/mm, and the RMS value at each wavelength in the whole field of view is less than 6 μm, all of them meet the design requirements. It can be seen that the hyperspectral imaging spectrometer system can realize the occultation detection of trace gases.

According to the demand for high imaging quality and high chromaticity in color digital cameras, we investigated the optical system design and camera spectral optimization methods of 3CMOS cameras based on Philips prisms. By constructing the model of the optical path of the Philips prism, the structural parameters of the prism were optimized. The volume of the system was reduced while ensuring total internal reflection and exit window size. Based on this method, the Philips prism 3CMOS camera optical system was designed, with a field of view angle of 45 ° and a relative aperture of 1/2.8. The system's MTF was greater than 0.4 in the full field of view and full band at Nyquist sampling frequency of 110 lp/mm. Subsequently, based on the fundamental principles of chromaticity, a vector imaging model for Philips prism cameras was established. The problem of thin film spectral shift caused by changes in light incidence angle was analyzed, and a correction model for spectral shift under wide beam conditions was proposed. Four sets of optical thin films in the camera were designed and optimized using this model. Through optical path simulation experiments and color error analysis, based on the optimized camera spectrum, the average color error of the system was reduced by 15.8%, and the color non-uniformity of the image plane was reduced by 60%. The results indicate that the designed optical system has good imaging quality, and the optimized camera spectrum achieves good color performance and uniformity.

To provide a reliable theoretical basis for the selection, mounting, and error compensation of the polarization device in the synchronous phase-shift transverse shear interference system, based on the Jones matrix principle, we construct an error model reflecting the degree of influence of the errors of quarter-waveplate and polarizer array on the measurement results in the system. Then, we quantitatively analyze how the measurement results are influenced by the following factors: the phase delay error of quarter-waveplate, fast-axis azimuthal angle error, and transmission-axis azimuthal angle error of the polarizer array. The simulation results show that the wavefront measurement errors are 0.00002λ(PV) and 0.000062λ(RMS) when the phase delay error of the quarter-waveplate is within ±1°, 0.0001λ(PV) and 0.00006λ(RMS) when the adjustment accuracy of the quarter-waveplate is within ±2°, and 0.003λ(PV) and 0.001λ(RMS) when the azimuthal angle error of the polarizer array is within ±1°. According to the simulation results, the polarization components in the measurement system were selected. At the same time, two polarization components with different levels of accuracy were chosen for comparison experiments. The experimental results indicate the following conclusions: the deviations of the residual values of the experimental results from the residual values of the simulation results in terms of the PV and the RMS values are less than λ/20, and the validity of the model can be verified to a certain extent. The mathematical model proposed in this paper can provide a reliable theoretical basis for the selection of polarization devices in synchronous phase-shifted transverse shear interference systems.

In order to improve the accuracy and success rate of geographical guidance, according to the structural characteristics of the roll-pitch electro-optical pod, a mathematical model of geographical guidance was developed through three steps: first, establishing the coordinate system; second, solving the target coordinates; and third, calculating the frame angle. Speed forward feed and small domain search modes were introduced on this basis. The frame angle calculation error affected by inertial navigation measurement error and target distance was simulated, and the results show that the longitude, latitude, and heading angle errors had a greater influence on the pitch angle calculation error; nonetheless, the errors of elevation and horizontal attitude angle had a greater influence on the calculation error of the roll angle. Improving the positioning accuracy of inertial navigation can further reduce the frame angle calculation error and improve the geographical guidance accuracy. However, when the heading angle decreases below 0.1 degrees and the horizontal attitude angle decreases below 0.05 degrees, then the influence weight of the attitude angle error also decreases. The improvement in guidance accuracy is no longer evident when attitude angle errors are reduced. Increasing target distance sharply decreases the error of frame angle calculation. Finally, the guidance test with pitch and roll mean square errors of less than 0.12 degrees shows the algorithm's accuracy and the simulation analysis's effectiveness.

In order to study the influence of the gas flow channel structure on the output performance of the flowing-gas diode pumped alkali vapor laser (FDPAL), we established the FDPAL theoretical model based on the gas heat transfer, fluid mechanics, and laser dynamics process in FDPAL using side pumping Rb vapor FDPAL (Rb-FDPAL) as the simulation object. The impacts of the gas flow direction, the cross-sectional area and the shape of the runner on the Rb-FDPAL’s output performance were analyzed. The results show that with the horizontal flow method and by increasing the cross-sectional area of the flow channel and setting a masonry structure as the connection between the gas flow channel and the steam pool, we effectively suppress the vortex in the vapor, increase the gas flow rate, and decrease the thermal effect of the steam pool. Rb-FDPAL's laser output power and slope efficiency are higher, and the simulation results are consistent with the experiment.

To address the problem of limited field of view measurement in traditional monocular vision measurement systems, we propose an omnidirectional spatial monocular vision measurement method based on a two-degree-of-freedom rotary platform. First, the rotating axis parameters of the double-degree-of-freedom rotary platform are calibrated. Then, the pictures of the checkerboard calibration plate fixed with the two-degree-of-freedom rotary platform are captured by using an auxiliary camera. Position coordinates of the checkerboard corner points are extracted and converted to the same camera coordinate system. The direction vector of the rotating axis parameters in the initial position is obtained through PCA (principal component analysis) plane fitting, and the position parameter of the rotating axis parameters in the initial position is determined using the method of spatial least squares circle fitting. The camera data acquired at various angles is transformed into the same coordinate system using the rotation angle of the rotary platform and the Rodrigues formula. This enables measurement of the target in the horizontal and vertical omnidirectional space. Finally, the measurement accuracy of the proposed method is verified using a high-precision laser rangefinder. Additionally, experiments comparing the omnidirectional spatial measurement ability of the proposed method with the binocular vision measurement system and wMPS measurement system are conducted. The results indicate that the method achieves a measurement accuracy comparable to that of a binocular vision system. However, it also surpasses the binocular vision system in term of measurement range, making it applicable for omnidirectional spatial measurements.

The infrared reflection characteristics of the wall are characterized and solved by the bidirectional reflectance distribution function (BRDF). BRDF measurement currently has two problems to be addressed: it requires much experimental data and accuracy is not high enough. By constructing the reflection characteristic test platform of the wall target, an MR170 Fourier infrared spectroradiometer was used to obtain the target radiance at the incident angle and each reflection angle in the 2-15 μm band. For the stealth target, the RBF network was used to fit the radiance at the bands of 3-5 μm and 8-14 μm to eliminate atmospheric interference. Then, the BRDF values of the stealth targets in the above two bands were obtained. To improve the accuracy of the BRDF model, an improved whale optimization algorithm (IWOA) was proposed to invert BRDF model parameters, and a reflectivity-solving method based on BRDF was designed. The IWOA has a good effect on the parameter inversion of the BRDF calculation model. According to the reflection method and applying the obtained BRDF data, the reflectance 0.5496 and the relative error 6.17% are obtained, which meet the engineering requirements.

In order to improve the shafting motion accuracy of two-dimensional turntables such as photoelectric theodolites, we establish a mathematical model considering both the structural error of parts and the coupling amplification effect based on Jacobian-Torsor theory. Aiming at a shafting structure with one fixed end and one swimming, an analysis method of partial parallel structure was proposed. Through numerical simulation analysis, the impact of each part’s structural errors on the motion accuracy of the shafting and the optimal shafting assembly scheme were obtained. The results of assembly and adjustment of a photoelectric theodolite with an optical diameter of 650 mm show that assembly optimization improved the motion accuracy of the shaft system by 32.1%. The precision model and optimization method of shafting motion provide a theoretical basis for the shafting adjustment and tolerance design of two-dimensional turntables such as photoelectric theodolites.

To improve the efficiency of high temperature calibration in the visible light band (0.3 μm~0.9 μm), a simplified method for high-temperature calibration is proposed. Firstly, a high-temperature calibration model in the visible light band with exposure time variable is proposed. Based on a large number of experimental data, it is found that the gray value of each channel of an RGB camera varies linearly not only with the increase of exposure time, but also with the increase of black-body radiation brightness. Thus, a specific form of high-temperature calibration model in the visible light band is determined. To solve the unknowns in the simplified high-temperature calibration model in the visible light band, image data at two different exposure times are collected under two levels of black-body radiation brightness, and then the image data is processed to obtain the high-temperature calibration curve of the RGB camera under any exposure time. Finally, the simplified visible light band high-temperature calibration method proposed in this article is compared to the conventional visible light band high-temperature calibration method based on exposure time. The experimental results show that the maximum relative error between the calculated value of the R channel, G channel, B channel and the calibrated values are 3.38%, 2.56%, -1.14%. Moreover, the relative error between the calculated and the calibrated values for each channel does not exceed 3.50%. The mathematical model proposed in this article can effectively simplify the conventional high-temperature calibration method, resulting in a reduced high-temperature calibration time and improving the calibration efficiency.

3D reconstruction is crucial for digitization of cultural relics, and the accuracy of 3D point cloud registration is a significant metric for evaluating the reconstruction quality. In practice, cultural relics point cloud data includes numerous details, and using conventional downsampling methods may result in the loss of such details, thereby affecting registration accuracy. We propose a point cloud classification downsampling and registering method for cultural relics based on curvature features. First, 3D point clouds data of cultural relics are obtained using linear matrix laser measurement. Next, the curvature values of all points are calculated, and a curvature threshold is set for point cloud classification. Different point sets are carried out downsampling with different weights according to their feature attributes to retain the shape features and details of the point cloud as much as possible. Finally, point cloud registration is achieved through calculating the rigid transformation model. Compared to the traditional global downsampling ICP method, the point cloud data of the downsampling processing before point cloud registration reduces to 1/3 of the original size. The average distance decreases from approximately 0.89 mm to 0.59 mm, while the standard deviation decreases from about 0.29 mm to 0.18 mm. This approach guarantees the accuracy of downsampling and registration and is applicable to various cultural relics point cloud data.

Investigating the impact of water quality, target characteristics, and target distance on underwater laser detection is crucial to assessing the effectiveness of laser detection for weak targets in complex coastal water bodies. We examine the theoretical and practical significance of understanding these factors in underwater laser detection. In this study, a laser detection model for detecting weak underwater targets is established. Monte Carlo simulation is used to verify the detection performance of weak multi-target laser ranging under different turbidities. The laser backscattering echo signals of weak targets at different distances are simulated, and the backscattering echo characteristics of multiple targets with various reflection coefficients are analyzed. Additionally, a smart and portable laser detection system for detecting weak underwater targets has been designed and developed. Laboratory and field lake environment tests were conducted to detect and range for multi-target. In a near-shore lake with a turbidity of 12.87 NTU, the system can effectively detect 3-4 mixed small target groups. These groups have different low reflection coefficients and diameters varying from 80 to 400 μm, all within a range of 10 meters. The average measurement error is ±0.11 m, which is consistent with the theoretical simulation results. The research results serve as a guide for computing links, designing systems, and optimizing parameters for detecting weak underwater multi-targets using blue and green lasers. Furthermore, the results assist in the engineering practice of detecting underwater obstacles in offshore turbid waters.

Aiming at the requirement of polarized light navigation for accurate position information of feature points in the sky, an accurate detection method for the solar position of imaging system based on all sky polarization mode is proposed. Compared with the traditional detection method of the solar position based on spot, we use the inherent polarization information in the atmosphere to complete the accurate measurement of the solar position, which has the characteristics of simple, high accuracy and wide application range. The optical acquisition system consists of three micro large-field-of-view camera modules and polarizers, which makes the structure more compact, smaller and lower in height. Starting from the principle, the algorithm of solving the solar position is simulated first, and then the algorithm is verified in three weather environments (sunny, occluded, and aerosol) using the optical acquisition system. It can be seen that when the weather is clear, the sun is detected at different times of the same day, and the accuracy of the measured sun's altitude and azimuth are 0.024° and 0.03° respectively; when the sun is blocked by high-rise buildings, the accuracy of the measured sun's altitude and azimuth are 0.08° and 0.05°; when the sun is blocked by the branches and leaves of trees, the accuracy of the measured sun's altitude and azimuth are 0.3° and 0.1° respectively. Only when the aerosol concentration exceeds a certain amount will the Rayleigh distribution mode of polarized light be destroyed, which will affect the detection accuracy of solar position. The experimental results show that this new detection method can not only meet the needs of polarized light navigation for the solar position, but also provide a new way of exploration for fans who like to explore the mysteries of the universe.

As aircraft maneuverability increases, multi-frame infrared small target detection methods are becoming insufficient to meet detection requirements. In recent years, significant progress has been achieved in single-frame infrared small-target detection method based on deep learning. However, infrared small targets often lack shape features and have blurred boundaries and backgrounds, obstructing accurate segmentation. According to the problems, an indistinguishable points attention-aware network for infrared small object detection was proposed. First, potential target areas were acquired through a point-based region proposal module while filtering out redundant backgrounds. Then, to achieve high-quality segmentation, the mask boundary refinement module was utilized to identify disordered, non-local indistinguishable points in the coarse mask. Multi-scale features of these difficult points were then fused to perform pixel-wise attention modeling. Finally, A fine segmentation mask was generated through re-predicting the indistinguishable points attention-aware features by point detection head. The mAP of the proposed method reached 87.4 and 63.4 on the publicly available datasets NUDT-SIRST and IRDST, and the F-measure reached 0.8935 and 0.7056, respectively. It can achieve accurate segmentation in multi-detection scenarios and multi-target morphology, suppressing false alarm information while controlling the computational overhead.

Aiming to the problem of the complicated preparation of existing optical fiber fluorescence temperature sensing probes, we propose a simple, cost-effective, and high-performance optical fiber fluorescence temperature sensor based on a capillary liquid core. Firstly, a mixed solution consisting of temperature-sensitive rhodamine B and temperature-insensitive rhodamine 123 was used as the temperature-sensitive material and encapsulated in a stainless-steel capillary to prepare a sensing probe. The ratio of the fluorescence emission peak intensities of the two dyes was utilized for temperature sensing. Subsequently, the sensing probe’s mixed solution concentration and capillary structural parameters were optimized. Then, the performance of the sensor was tested. Finally, the sensor was applied to real-life temperature measurements. The experimental results demonstrate that the sensor has a temperature response range of 30-70 °C and that there is a quadratic correlation between the fluorescence intensity ratio and the temperature, with the fitted correlation coefficient as high as 0.9984. The sensor exhibits excellent accuracy, repeatability, and stability, with more than three months of service time. Moreover, it can be well-utilized to detect temperature in daily life. The optical fiber fluorescence temperature sensor shows significant potential for real-time monitoring and remote detection applications.

To address the issues of low measurement accuracy and insufficient stability in traditional calibration methods for Shack-Hartmann wavefront sensors (SHWFS), we propose a high-precision absolute calibration method using spherical waves generated by sensor. A high-precision calibration method for spherical waves was obtained through theoretical derivation. Combined with the constructed spherical wave calibration experimental device, high-precision calibration was performed on the SHWFS with sub apertures of 128×128. The structural parameters of the SHWFS (f, w, and L0) are calculated precisely. The measurement accuracy of the SHWFS is verified after calibration. The experimental results demonstrate that by using this method to calibrate the SHWFS, its wavefront recovery accuracy reaches a PV of 1.376×10-2λ and an RMS of 4×10-3λ (where λ=625 nm), respectively. Additionally, its repeatability accuracy reaches a PV of 3.2×10-3λ and an RMS of 9.76×10-4λ (where λ=625 nm), respectively. These findings suggest that this method is suitable for enhancing the measurement accuracy of high-precision calibration of SHWFS with large aperture.

The recent advent of miniature head-mounted fluorescence microscopes has revolutionized brain science research, enabling real-time imaging of neural activity in the brains of free-moving animals. However, the pursuit of miniaturization and reduced weight often results in a limited field of view, constraining the number of neurons observable. While larger field-of-view systems exist, their increased weight can impede the natural behaviors of the subjects. Addressing these limitations, a novel design utilizing a metalens schematic is proposed. This approach offers the benefits of being ultra-light, ultra-thin, and capable of high-quality imaging. By deriving the aberration formula specific to hyperbolic phase metalens and using it as a foundation, a design for a miniature fluorescence microscope was developed. This microscope boasts a 4 mm×4 mm field of view and a numerical aperture (NA) of 0.14, effectively correcting seven primary aberrations. The resulting prototype, weighing a mere 4.11 g, achieves a resolution of 7.8 μm across the entire field of view. This performance is sufficient to image neural activity in the brains of freely moving mice with single-cell resolution.

Catastrophic Optical Mirror Damage (COMD) on the cavity surface is the key factor limiting the threshold output power of high-power quantum well semiconductor laser diodes. To improve the output power of the laser diode, the band gap width of the active material in the cavity surface of the semiconductor laser diode can be adjusted by the quantum well intermixing technology to form a non-absorbing window transparent to the output laser. Based on the primary epitaxial wafers of InGaAs/AlGaAs high power quantum well semiconductor laser diode, using the single crystal Si dielectric layer grown by Metal Oxide Chemical Vapor Deposition (MOCVD) as the diffusion source, the research on Si impurity induced quantum well intermixing was carried out by using the Rapid Thermal Annealing (RTA) process. The effects of growth characteristics of Si dielectric layer, the temperature and time of RTA on the intermixing process were investigated. The experimental results show that the epitaxial 50 nm Si dielectric layer at 650 °C combined with 875 °C/90 s RTA treatment can obtain about 57 nm wavelength blue shift while maintaining the photoluminescence spectrum shape and the primary epitaxial wafers. It is found that the diffusion of Si impurities into the waveguide layer on the primary epitaxial wafer is the key to the remarkable effect of quantum well intermixing by the energy spectrum measurement technique.

Orbital-Angular-Momentum (OAM) is one of the most important parameters in high-capacity optical communication or super-resolution imaging. Based on the Huygens-Fresnel principle and the theory of coherent combination, we propose hybridly polarized vortex beam arrays in coherent combinations of radial off-axis Gaussian beamlets with vortex and polarization Topological Charges (TC). The effect of vortex, polarization and addition TC and the number of beamlets on OAM spectra of the proposed beam arrays at input and output plane are both stressed. The results show the number of beamlet and hybrid polarization present joint effect on maximal weight of OAM-modes. An increase of maximal weight value at OAM-mode is accompanied by the growing number of the beamlet, while the hybrid polarization can not significantly increase the maximum weight of OAM spectra. As the number of beamlets increases, hybrid polarization can't significantly improve the maximal weight value in OAM spectra. Furthermore, the maximal mode equals the total TC at central Optical Vortex (OV) and it is irrelevant to the number of beamlets. Whereas for other modes for non-zero weight, their locations are jointly determined by vortex, polarization and addition TCs and the number of beamlets. This work may provide potential applications in the OAM-based communication and polarization imaging technologies.

In order to explore the influence of the number of coupling regions on the output of the ding-shaped microring resonator, the physical model of the ding-shaped microring resonator is established and studied by using the transfer matrix method. On this basis, the influence of the number of different coupling regions on the output of the ding-shaped microring resonator is analyzed. The experimental results show that with the increase of the number of coupling regions, the number of resonance peaks increases in the range of 1.54~1.56 μm working wavelength, the full width at half maximum (FWHM) decreases, the quality factor Q increases, the energy storage performance of the device is better, and the filter function on a specific wavelength can be realized. It can be concluded that the number of coupling regions has a great influence on the performance of the ding-shaped microring resonator. The number of coupling regions is selected according to the actual needs in the design.

Speed synchronization performance and anti-interference are important factors that affect the synchronous operation dynamic response and steady-state accuracy of dual Permanent Magnet Synchronous Motors’ (Dual-PMSMs). By introducing cross-coupling control as the framework, an integral sliding mode speed tracking controller based on an improved bi-power reaching method is proposed to reduce the speed error between two motors. A load torque observer is designed to bring the observed value into the Sliding Mode Control (SMC) reaching method that enhances the anti-disturbance performance of the system. Meanwhile, a synchronous controller is designed using a Fuzzy-Proportional-Integral-Derivative (FPID) control to improve the synchronization of the Dual-PMSMs. The results show that compared with the traditional PI algorithm as the target speed is 800 r/min, the proposed control method can decrease the two motors’ speed synchronization error from 25 r/min to 12 r/min under a no-load startup and reduce the speed synchronization error from 7 r/min to 2.2 r/min with sudden load torque, improving the synchronization and disturbance rejection.

The polarization-multiplexing of a laser based on a medium with a large gain bandwidth and a high thermal conductivity can benefit dual-frequency and dual-comb lasers’ spectral bandwidth and power. This paper presents a demonstration of the polarization-multiplexing of a laser based on a bulk Yb:CALGO crystal. The polarization multiplexing is realized by sandwiching the gain crystal with two birefringent crystals which are cut at 45˚ to their optical axis. This sandwich-configuration creates inside the cavity two orthogonally polarized beams which are spatially separated only in the sandwich-configuration part but collinear in other part. Meanwhile, a single pump beam is also split into two beams automatically, matching the two cavity modes. This configuration also allows the gain crystal to be located in at the waist of cavity modes, which benefits the pumping efficiency. The laser outputs watt-level power with a slope efficiency exceeding 30%. A dual-frequency operation with terahertz frequency separation is realized by inserting an etalon into the cavity.

To meet the requirements of wavefront distortion correction for miniaturized adaptive optics systems, a Deformable Mirror (DM) using micro voice coil actuators was designed based on systematic theoretical analysis. The structural parameters of the micro voice coil actuator were optimized by electromagnetic theory and the finite element method. The DM was optimized with respect to thermal deformation, resonance frequency, coupling coefficient and other parameters. Finally, wavefront fitting and residual calculation were completed according to the influence function. The optimized 69-element Voice Coil Deformable Mirror (VCDM) has a large phase stroke, good thermal stability, and a large first resonance of 2220 Hz. The RMS of the fitting residuals of the VCDM for the first 35 Zernike modes with a PV value of 1 μm are all below 30 nm. For complex random aberrations, the compact VCDM can reduce the wavefront RMS to less than 10%. Compared with a traditional VCDMs, the results of our compact VCDM indicate that it has a higher wavefront fitting precision. The compact VCDM with high performance and low cost has good potential applications in human retinal or airborne imaging systems.

In order to meet the urgent need of developing lightweight and compact space cameras quickly, effectively, and rapidly, a detailed comparative analysis is conducted, including optical system forms and imaging systems. The optical system form of RC+ compensation group is determined, and the imaging system of small F#+micropixel is adopted. Compared with the detailed parameters of the DOVE camera, a lightweight all-aluminum high-resolution camera with a resolution of 3.48 m at an orbital altitude of 500 km is designed. The overall design results of the camera, its optical and optomechanical structures, imaging electronics, and thermal control are described in detail. The optical design results of the RC+ compensation group of F5.6 are obtained. Using RSA-6061 microcrystalline aluminum alloy as the structural material of the mirror, coupled with an integrated high-rigidity hard aluminum alloy structure, the static (gravity and temperature deformation) simulation analysis results meet the optical design tolerance requirements. The dynamic simulation analysis results show that the first order mode is 302.92 Hz, which has a sufficiently high dynamic stiffness and safety redundancy. The imaging electronics using a 3.2 μm large area array 9 K×7 K detector is designed for low noise miniaturization. Thermal control is provided by the satellite platform at a temperature level of 20 °C± 4 °C for the camera. Integration test results show that: (1) The RMS wave aberration of the central field of view is λ/15.6, and the wavefront aberration of the five fields of view is better than λ/12.3, which ensure high-quality imaging near the diffraction limit of the camera. The measured optical transfer function at Nyquist frequency is 0.217; (2) The maximum sinusoidal vibration of the camera in three directions is amplified 1.17 times, and the first-order mode of the camera is 295 Hz, with a deviation of 2.61% from the simulation result. The structural stiffness is high and the mechanical stability is good. Under vacuum environment of 10-4 Pa and three different temperatures of 16 °C, 20 °C and 24 °C, the image is clear and can distinguish the corresponding resolution plate image at Nyquist frequency; (3) The image of 2 km outfield target is good, as well as clear and distinct grayscale image with sharp shadow boundaries. The all-aluminum high-resolution camera is achieved 3.48 m resolution at a track height of 500 km,width of 15 km×15 km and a total weight of 2 kg. The structural rigidity and strength test results meet the requirements of space launch scenarios, and these can provide theoretical guidance and engineering reference for the design of lightweight and higher-resolution space cameras.

Monochromators are widely used in spectral calibration, material analysis and other aspects, so research of high spectral resolution monochromator systems is of great significance. Based on the vector grating equation, the influence of the height of the incident slit on the spectral line bending of a spectrometer is investigated, and the analytical expressions of the spectral line bending at the same wavelength and the slit height are given. An optimization scheme of the spectral resolution of the monochromator based on the suppression of spectral line bending by the slit height is proposed. According to the performance index requirements of a highly sensitive and ultra-fast time response detector, a three-grating monochromator optical system with a spectral resolution of 0.1 nm and a band range of 185-900 nm was designed, and a prototype was built to verify the influence of the slit height on spectral line bending, and to explore the influence of slit height on spectral resolution on the above basis. The experimental results show that the spectral resolution can be improved from 0.32 nm to 0.1 nm by optimizing the slit height when the slit width is fixed.

In order to improve the traditional attitude measurement accuracy of star sensors, interference angle measuring technology can be combined with a traditional star sensor. Based on the centroid positioning technology of traditional star sensors, the light intensity information of star image points is subdivided to break through the accuracy limitation of centroid positioning and obtain a highly precise interferometric star sensor with a large field of view. In this paper, the factors that restrict the angle measurement accuracy of interferometer sensors are deeply studied with particular interest given to the influence of interference fringe segmentation error on angle measurement accuracy. Through research and analysis, we conclude that the asymmetry error is not the main factor affecting the angle measurement accuracy of interferometric sensors. When the mismatch error between the Moire fringe period and the overall optical dimension of the optical wedge array is less than 1%, the single-factor angle measurement error is less than 0.01". For non-orthogonal error between Moire fringe orientation and an optical wedge’s array arrangement direction, the accuracy error of single-factor angle measurement is sure to be less than 0.01" when the fringe rotation angle is less than 0.1°. Therefore, the above two main errors should be suppressed in the production and assembly so that the measurement accuracy of the interferometer sensor is closer to the high-precision theoretical value.

Constructing the radiation characteristics of space targets is of great significance for the development of space situational awareness technology. In this study, we aim to investigate the infrared radiation characteristics of space targets by developing a simulation program based on the finite element method and unstructured tetrahedral mesh. Through vector coordinate transformation, we calculate the orbit external heat flux received by each surface of the target. By combining the surface material properties and Bidirectional Reflection Distribution Function (BRDF), the temperature and infrared radiation characteristics of each target surface were simulated. Furthermore, we analyze the spectral radiation intensity of the target in the ascending and descending orbital arcs under ground-based detection conditions, taking into account the effects of atmospheric attenuation and background radiation. The results show that, for a three-axis stabilized synchronous orbit satellite with solar panels fixed in the flight direction, the temperature variation range of each surface in the sunlight area and the shadow area is small. The detection effect of the long-wave band of 8~14 μm is better than that of the medium-wave band of 3~5 μm, and the maximum radiation intensity is about 770 W/sr. Ground-based infrared spectrum detection is more affected by the atmosphere, and the detection band must be optimally selected.

Narcissus refers to the phenomenon in an infrared system where a cooled imaging sensor can “see” its own reflected image by the reflection of the frontal optical surfaces. Control of narcissus is one of the important requirements in the design of the infrared imaging system. A cooled medium-wave infrared imaging system with Cassegrain reflection structure is designed and analyzed to obtain the optical surfaces with serious narcissus. In addition, the narcissus is reduced by Zemax, and the optimization of the system transfer function MTF is taken into account while the narcissus is controlled. The optimized medium-wave infrared imaging system is compared with the imaging system without narcissus suppression through NARCISSUS macro (narcissus analysis macro), Tracepro modeling software and actual imaging, and it was found that the narcissus induced equivalent temperature difference (NITD) of the detector image surface decrease from 1.0484 K to 0.1576 K. The energy and size of the narcissus spot did not show marked change during the focusing of the system. The optimized optical structure can effectively control the narcissus of the system.

In order to meet the ultra-high temperature stability requirements of the ground weak force measurement system for inertial sensor, the thermal design of the whole system is carried out. Firstly, the structure of ground weak force measurement system of inertial sensor, heat transfer path of sensitive structure and internal heat source are introduced. Secondly, according to the index requirements of the thermal control of the system, a high-precision thermal control method combining the three-stage thermal control structure and Proportional Integral Differential (PID) control algorithm is proposed to reduce the influence of temperature noise on the detection sensitivity of the inertial sensor. Then, UG/NX software is used to establish the finite element model and carry out the thermal analysis calculation under different working conditions, and the temperature change value of the measurement system in the time domain after equilibrium is (1.2-1.6) ×10-5 K. Finally, the temperature distribution of the measurement system in the time domain is described in the frequency domain, and the temperature stability results of sensitive structure of the inertial sensor are obtained. The analysis results show that under the current thermal control measures, the temperature stability of the sensitive structure of the inertial sensor is better than 10-4 K/Hz1/2, meeting the requirements of thermal control indicators, and the thermal design scheme is reasonable and feasible.

The Taiji program is a space gravitational wave detection mission proposed by the Chinese Academy of Sciences, which uses laser differential interference to detect pm-level displacement fluctuations caused by gravitational waves between satellites. In order to eliminate the phase measurement error caused by the desynchronization of the clocks in satellites, the Taiji program intends to use the sideband multiplication transfer scheme to measure and eliminate inter-satellite clock noise. We discuss the requirements, principles, and methods of inter-satellite clock noise transmission of the Taiji program, and design experiments for the principle verification. By building an electronics experiment system, the limit value of the clock noise of the two systems was tested, the relevant parameters of the experiment were determined, and the principle of the sideband multiplication transfer scheme was verified by further optical experiments. The experimental results show that the clock noise cancellation scheme and related parameters proposed in this paper are reasonable and feasible, and are suitable for the needs of the Taiji program. Moreover, in the 0.05 Hz-1 Hz frequency band, the suppression effect of inter-satellite clock noise is better than 2π×10-5 rad/Hz1/2, which meets the noise requirements of the Taiji pathfinder and lays an experimental and theoretical foundation for the design of a clock noise transmission scheme and parameters of the Taiji program in the future.

The Taiji program is a key task for China's space gravitational wave detection, and as an important part of space gravitational wave detection, the telescope's performance will directly affect the accuracy of gravitational wave detection. For the existing typical space gravitational wave telescope structures, due to the high sensitivity of secondary mirror, it is difficult to meet the requirements for manufacturing and adjustment tolerance of larger aperture space gravitational wave telescopes, especially the tolerance requirements for in-orbit stability. In order to solve the above problems, firstly, a new optical system structure of space gravitational wave telescope with intermediate image plane set between three and four mirrors is proposed to reduce the sensitivity of the secondary mirror. Combined with the theoretical method of Gaussian optics, the initial parameters of the structure of the new telescope are theoretically analyzed and calculated. Secondly, through the optimization design, a telescope optical system with a pupil diameter of 400 mm, a magnification of 80 times, a field of view of ± 8 μrad, and a wavefront error RMS value of better than 0.0063λ was obtained. Finally, the sensitivity evaluation tolerance allocation table of the telescope system is established, and the tolerances of the existing telescope structure and the new telescope structure are compared and analyzed. Compared with the existing telescope structure, the sensitivity of the new telescope structure is reduced by 30.4%. The results show that the new telescope structure has the advantage of low sensitivity, which provides an optimal scheme for the design of space gravitational wave telescopes.

The anamorphic optical system has a two-plane symmetry, with different focal lengths in the two symmetry planes. This system can obtain a wider field of view when using sensors with conventional size. We propose a method for designing catadioptric anamorphic optical systems based on their first-order aberration characteristics. A catadioptric anamorphic optical system is designed by using a biconic surface, with a focal length of 500 mm in theXOZ plane and 1000 mm in the YOZ plane. The system’s F-number is 10, and the full field angle is 1°×1°. The mean value of the full field of view MTF of the system is higher than 0.3 at 80 lp/mm. The overall structure of the system is compact, and the imaging quality is excellent.

We present a method for designing a transmissive-reflective combined optical system to generate a focused ring-shaped laser beam. The design aims to achieve a freely adjustable radius for the focused ring-shaped laser beam and ensure uniform beam intensity even after defocusing. Based on the principle of equal energy splitting, the transmissive system establishes mapping functions for the input and output light projection height. It optimizes the lens parameters to shape the incident Gaussian light into a flat-topped circular shape, thus achieving uniformity of beam intensity. On the other hand, the reflective system uses the adjustable diameter range of the focal plane ring-shaped light and working distance parameters. By applying the principle of geometric ray tracing, it calculates the parameters of the conical reflecting mirror, parabolic cylindrical mirror, and dynamic mirror, then the flat-topped circular light is transformed into a ring-shaped light. The experimental results show that when the half-apex angle of the dynamic mirror is 16°, the designed system can achieve a freely adjustable radius for the focused ring-shaped laser beam from 15 mm to 30 mm with a size error not more than 0.05 mm, and the intensity uniformity after defocusing reaches 84%. The design method can achieve both uniformity of intensity and freedom of size adjustment without replacing the system lens. It has good operability and yields higher precision and efficiency in the processing of ring-shaped light.

The concentrating solar simulator can obtain solar radiation spots with high-power convergence, which has important applications in the fields of solar thermal power generation and thermochemical research. To obtain uniform solar radiation spots, a free-form surface condenser design method based on non-imaging optics is proposed, and its design principle and specific method are described. The designed free-form condenser is compared with a non-coaxial ellipsoidal condenser with the same containment angle, and the correctness of its design method is verified by simulation analysis. The simulation results show that when a xenon lamp with a rated power of 6 kW is used as the light source, the single-lamp solar simulator composed of a free-form condenser can produce a spot with an average irradiance of 274.4 kW/m2 in the target region with a diameter of 60 mm. The spot’s unevenness decreases from 18.28% to 5.69% compared with that of a non-coaxial ellipsoidal solar simulator. The seven-lamp solar simulator can produce a spot with an average irradiance of 1.65 MW/m2, with a spot unevenness that decreases from 13.19% to 5.49%.

Current study on photonic neural networks mainly focuses on improving the performance of single-modal networks, while study on multimodal information processing is lacking. Compared with single-modal networks, multimodal learning utilizes complementary information between modalities. Therefore, multimodal learning can make the representation learned by the model more complete. In this paper, we propose a method that combines photonic neural networks and multimodal fusion techniques. First, a heterogeneous photonic neural network is constructed by combining a photonic convolutional neural network and a photonic artificial neural network, and multimodal data are processed by the heterogeneous photonic neural network. Second, the fusion performance is enhanced by introducing attention mechanism in the fusion stage. Ultimately, the accuracy of task classification is improved. In the MNIST dataset of handwritten digits classification task, the classification accuracy of the heterogeneous photonic neural network fused by the splicing method is 95.75%; the heterogeneous photonic neural network fused by introducing the attention mechanism is classified with an accuracy of 98.31%, which is better than many current advanced single-modal photonic neural networks. Compared with the electronic heterogeneous neural network, the training speed of the model is improved by 1.7 times; compared with the single-modality photonic neural network model, the heterogeneous photonic neural network can make the representation learned by the model more complete, thus effectively improving the classification accuracy of MNIST dataset of handwritten digits.

In order to improve the laser wake guidance distance and the detection signal-to-noise ratio, it is of great theoretical and practical value to study the backscattering characteristics of bubble targets with different distances, bubble sizes, bubble number densities, and bubble layer thicknesses. The laser backscattering characteristics of ship wake bubble targets with different distances, scales, numerical densities, and thicknesses are studied using Monte Carlo simulations and indoor experiments. When the bubble density is 102-108 m-3 and the thickness of the bubble layer is greater than 0.05 m, there is always an echo signal for both large- and small-scale bubbles. When the thickness of the bubble layer is less than 0.05 m, no echo signal is detected. At this situation, the thickness of the bubble layer is the greatest impact factor on the backward scattering of bubbles. When the bubble number density is 109 m-3 and the thickness of the bubble layer is below 0.05 m, the pulse width of the large-scale bubble echo signal widens. The number density and scale characteristics of the bubbles have the greatest impact on the backscattering of bubbles. A laser backscattering measurement system at the scale of typical underwater bubbles is built to verify the influence of different ship wake bubble characteristics on the laser backscattering detection system, which can provide support for the ship wake laser detection project.

Underwater polarized light with certain distribution characteristics is formed when sunlight is scattered by the atmosphere and refracted by the surface of the water. The polarization distribution pattern of the underwater polarized light can be used in navigation. In this paper, an air-water model is proposed to calculate the polarization pattern of sky light under varying wave conditions and simulate the underwater polarization distribution pattern under the influence of wave refraction. Distribution images are simulated for underwater polarization degree and polarization angle in conditions with calm water, sinusoidal waves and random waves with different solar altitude angles. The results are verified using underwater experiments. The comparison of the polarization distribution pattern under the waves with that under the calm water show that the proposed model can accurately characterize the characteristics of the polarization distribution pattern under typical wave surfaces, providing a theoretical basis for improving the environmental adaptability of underwater polarization navigation under fluctuating water surface conditions.

To improve the detection efficiency of deep ultraviolet laser for semiconductor detection, it is necessary to develop 257 nm deep ultraviolet picosecond laser with high power and high repetition frequency. In this study, a 257 nm deep ultraviolet laser was experimentally investigated based on photonic fiber amplifier and extra-cavity frequency quadrupling. The seed source uses a fiber laser with a central wavelength of 1030 nm and a pulse width of 50 ps, delivering a power output of 20 mW and a repetition frequency of 19.8 MHz. High power 1030 nm fundamental frequency light was obtained through a two-stage ytterbium-doped double cladding (65 μm/275 μm) photonic crystal fiber rod amplification structure, and 257 nm deep ultraviolet laser was generated using double frequency crystal LBO and quadruple frequency crystal BBO. The seed source uses a two-stage photonic crystal fiber amplifier to get a 1030 nm laser with output power of 86 W. After the laser focusing system and frequency doubling, a second harmonic output power of 47.5 W at 515 nm and a fourth harmonic output power of 5.2 W at 257 nm were obtained.The fourth harmonic conversion efficiency was 6.05%. The experimental results show that this structure can obtain high power 257 nm deep ultraviolet laser output, providing a novel approach to improve the detection efficiency of the lasers for semiconductor detection.

The movement of objects is everywhere in nature. With the rapid development of smart vehicle and 6G mobile communications, the demand for highly Integrated Sensing and Communication (ISAC) devices with communication and motion sensing is increasing. Based on the coexistence of luminescence and detection characteristics of GaN multiple quantum wells, an integrated optoelectronic chip based on the epitaxial GaN multiple quantum wells material on sapphire substrate with sensitive motion detection and visible light communication. The transmitter of the optoelectronic chip transmits a visible light signal in blue band to the moving target object. The visible light signal modulated by the motion of the target object is reflected back to the receiver of the chip to stimulate the changing photocurrent. By analyzing the changing photocurrent, the motion of the target object rotating at different speeds can be detected. The change period of the photocurrent curve is consistent with the rotation period of the target object. We also study the optoelectronic characteristics and the visible light communication performance of the optoelectronic chip. This chip can be used as transceiver terminal of visible light communication system and can also process and transmit the motion detection signals collected by the chip. The optoelectronic chip based on GaN multiple quantum wells materials is a highly integrated ISAC terminal device with application value.

Taking advantage of the high absorption coefficient, excellent photoelectric properties, and high carrier mobility of Single-Walled Carbon NanoTubes (SWCNTs), high-performance, transparent, all-carbon Field-Effect Transistor (FET) photodetector has been constructed with a high transmittance more than 80% in the visible light band, in which semiconducting SWCNT (sc-SWCNT)/fullerene (C60) heterojunctions as the channel materials, patterned metallic SWCNT film as source/drain electrodes, graphene oxide (GO) as the dielectric layer, and Indium Tin Oxide (ITO) as a transparent gate electrode. The electrical test results show that the photodetector exhibits a strong gate-tunable characteristics, and achieves a broadband spectral response from 405 to 1064 nm in the visible-near infrared spectral region. Under 940 nm illumination with a light density of 5 mW/cm2, the maximum photoelectric responsivity of 18.55 A/W and a specific detectivity of 5.35×1011 Jones can be achieved.

A ground-based Doppler Asymmetric Spatial Heterodyne (DASH) interferometer with a high Signal-to-Noise Ratio (SNR) and large etendue (AΩ) with thermal compensation was developed to detect wind field information in the middle atmosphere. The detailed parameters and index of the DASH interferometer were developed for the 557.7 nm oxygen airglow spectral line. The system was designed with an expanded Field Of View (FOV) and thermal compensation. The half-FOV angle reached 2.815°, the etendue was 0.09525 cm2sr, and the system’s SNR was approximately 113.75. Through the thermal compensation design, the final optical path difference with temperature variation (dΔd0/dT) was only 2.224×10-7mm/°C. The optical system was designed and optimized according to the corresponding parameters. Image-side telecentric and bilateral telecentric optical system structures were used in the entrance optics and exit optics, respectively, and parameters such as telecentricity and distortion met the detection requirements. To verify the design results, a ground-based DASH interferometer experimental platform was constructed, and indoor and outdoor ground-based experiments were conducted. In the final experiment, clear interference fringes were obtained, which proves that the system design results of the DASH interferometer are reasonable, and the system’s SNR and etendue meet the detection requirements.

To improve the extinction ratio of a polarization beam splitter, we propose a dual-slot ultra-compact polarization splitter (PBS) consisting of a hybrid plasma Horizontal Slot Waveguide (HSW) and a silicon nitride hybrid Vertical Slot Waveguide (VSW). The coating material is silicon dioxide, which can prevent the oxidation of the mixed plasma and also facilitate integration with other devices. The mode characteristics of the HSW and VSW are simulated by using the Finite Element Method (FEM). At suitable HSW and VSW widths, the TE polarization modes in HSW and VSW are phase-matched, while the TM polarization modes are phase mismatched. Therefore, the TE mode in an HSW waveguide is strongly coupled with a VSW waveguide by adopting a dual-slot, while the TM mode directly passes through the HSW waveguide. The results show that PBS achieves an Extinction Ratio (ER) of 35.1 dB and an Insertion Loss (IL) of 0.34 dB for the TE mode at 1.55 μm. For the TM mode, PBS reached 40.9 dB for ER and 2.65 dB for IL. The proposed PBS is designed with 100 nm bandwidth, high ER, and low IL, which can be suitable for photonic integrated circuits (PICs).

The decoherence of temporal quantum correlation is explored in a voltage-controlled quantum dots molecule coupled to a cavity. The temporal correlation in the optoelectronic hybrid system is studied based on Leggett-Garg inequalities. The inequality violations can be interpreted as the existence of temporal quantum correlation during dynamical evolution. The temporal quantum correlation is enhanced by its electron tunnel’s strength and cavity frequency detuning. It is found that there is no temporal quantum correlation in the regions where the values of spatial quantum correlation are zero and the maximal violations occur in conditions with high values of quantum correlation. In contrast, the spatial quantum coherence can still exsit when the value of temporal quantum correlation is zero. The method of open quantum system dynamic is used to study the effect of reservoir memory on temporal quantum correlation. The temporal quantum correlation can be suppressed due to the spontaneous decay of the quantum dots and cavity leakage. These results are helpful for quantum information processing technology in hybrid quantum systems.

We propose cosh-Pearcey-Gauss beams with uniform polarization, which are mainly modulated by a hyperbolic cosine function (n, Ω) and the angles related to uniform polarization (α, δ). Based on angular spectrum representation and the stationary phase method, the Poynting vector, Spin Angular Momentums (SAM) and Orbital Angular Momentums (OAMs) in the far zone are studied. The results show that a larger n or Ω in the hyperbolic cosine function can partition the longitudinal Poynting vectors, SAMs and OAMs into more multi-lobed parabolic structures. Different polarizations described by (α, δ) can distinguish their Poynting vectors and angular momentums between the TE and TM terms, though this does not affect the patterns of the whole beam. Furthermore, the weight of the left and right sides of longitudinal Poynting vectors, SAMs and OAMs in TE and TM terms can be modulated by left-handed or right-handed elliptical polarization, respectively. The results in this paper may be useful for information storage and polarization imaging.

An all-optical half-adder is designed by combining the nonlinear effect and linear interference effect of photonic crystals. By dividing the light source into two parts equally, the half adder AND gate and XOR gate are designed separately. The nonlinear effect is used to realize the AND gate with high contrast, and the linear interference effect is used to realize the XOR logic, so that the overall response speed of the device is improved. In this design structure, the device only has threshold requirements for the signal light source power. When the signal power is greater than 51.4 mW/μm2, it has stable output and strong anti-interference ability. The designed contrast of the half adder carry output port is 20.69 dB, and the output port contrast is 20.13 dB. The data transfer rate is 0.75 Tbits/s and the occupied area is 623 μm2.

The propagation loss of a waveguide is a key indicator to evaluate the performance of an integrated optical platform. The commonly used cut-back method for measuring propagation loss requires the introduction of the spiral test structure. In order to remove bending loss, the bending radius is usually designed to be larger but this consequently has a larger footprint. In this paper, we suggested a method to simultaneously measure the propagation loss and bending loss of waveguides with a cut-back structure. According to simulations, the bending loss can be exponentially fitted with the bending radius, which can be further simplified as linear fitting between the natural logarithm of the bending loss and bending radius. A genetic algorithm was used to fit the insertion loss curve of the cut-back structure and the propagation losses and bending loss were calculated. With this method, we measured a cut-back structure of lithium niobate waveguide and got a propagation loss of 0.558 dB/cm and a bending loss of 0.698 dB/90° at a radius of 100 μm and wavelength of 1550 nm. Using this method, we can simultaneously measure waveguide propagation loss and bending loss while mitigating the footprint.

To achieve high-precision and stable tracking performance, a novel disturbance observer for the photoelectric platform based on dual velocity loops is designed. This method aims to minimize the impact of internal friction torque, external carrier disturbances and sensor noise, thereby enhancing the dynamic response performance of the system. Firstly, the mathematical model of double speed-loop is established. By analyzing the signal spectrum and response performance of various sensors, we have chosen the circular grating sensor with low noise and short delay to replace the traditional measuring machine for closing the inner speed loop. Moreover, the Fiber Optic Gyro (FOG) is utilized for the feedback device of the outer speed loop. Then, a disturbance observer is designed based on the gyro speed signal to observe the disturbance compensation residual in the inner speed loop and the outer carrier disturbance signal, while the feed-forward compensation is performed. The experimental results demonstrate that the double speed loop observer control method can reduce the system regulation time to 45% of the original. When subjected to sinusoidal disturbance signals with varying amplitudes (0.25° to 2°) and frequencies (0.25 Hz to 2 Hz), this method effectively improves the system's ability to suppress disturbances and increases the isolation degree from the initial 20.9 dB to 30 dB. The disturbance observer with double speed loops meets the system requirements of rapid response, stable tracking, high precision and strong anti-disturbance ability of the photoelectric tracking platform.

To improve the field of view of the near-to-eye display imaging system by using the optical waveguide scheme, we propose a method of multiplexing interference fringes with equal periods and variable inclination angles to expand the angular bandwidth of the volume holographic grating for augmented reality glasses coupling element. With this method, the range of incident angles after the expansion mathes the Bragg condition, and the influence of the periodic change on the diffraction angle of the incident light is eliminated, thereby improving the angular response range of the coupling element volume holographic grating and reducing the stray light introduced by grating diffraction. The rigorous coupled wave analysis theory is used to simulate the volume holographic grating multiplexing three interference fringes with equal period and variable inclination angles. Under the TE and TM polarization states at the wavelength of 530 nm, the angular bandwidth of the multiplexed volume holographic grating is 3.6° and 3.3°, respectively. The angular bandwidth of the multiplexed volume holographic grating is twice as large as that of the volume holographic grating recorded with a single interference fringe. This method is expected to break the limitation of the volume holographic grating material on the angular bandwidth of the grating, and can be used to expand the field of view of the near-to-eye display imaging system to achieve lightweight, high-efficiency, large-field-of-view, and low-stray-light augmented reality glasses.

Wet transferring two-dimension (2D) material to a semiconductor substrate is a common method to prepare a hetero-junction photodetector. When preparing to wet transfer a hetero-junction, different preparation details have significant effects on the properties of the hetero-junction formed by the 2D materials and semiconductors. In this paper, a series of identical Gr/Si hetero-junction devices were prepared by the wet transfer method and the relationship between its preparation technique and the voltage-current characteristics was studied in detail. The experimental results show that the gradient drying process can significantly reduce the dark current of the Gr/Si hetero-junction photodetector, the optimal drying temperature peak is 170 °C, and the leakage current basically no longer changes above 170 °C. The surface impurities and residual water in the inter-layer of Gr/Si van der Waals hetero-junction has a significant effect on the leakage current of the hetero-junction. The selective etching and annealing process of a Gr/Si van der Waals hetero-junction can also greatly reduce the leakage current. Therefore, a suitable drying process, selective etching process and annealing process are each necessary in the preparation of a Gr/Si hetero-junction photodetector. These results can give reference to the fabrication of two-dimensional material hetero-junction devices by the wet transfer method.

For data communication between single wavelength laser communication terminals, good isolation between signal transmission and reception is the key to establishing duplex bidirectional laser communication. In this paper, with respect to the transmission and reception scheme of a single laser wavelength laser communication terminal and its overall communication performance, the influence of the surface roughness and contamination level of key components on the isolation performance of the laser communication terminal is analyzed. The model parameters are derived from Harvey model and ABg model, and the designed scheme is analyzed using TracePro software. When the surface roughness or contamination level of λ/2 wave plate, λ/4 wave plate and optical antenna structure in the signal transmission channel is improved, the backscattering caused by these elements will reduce the isolation performance in the signal transmission channel. At the same time, the measurement result of laser communication terminal isolation is 77.86 dB, which is basically consistent with the software simulation result of 78.35 dB. This can be applied in laser communication system.

Ammonia emission will cause harm to the environment and human health, so it is particularly important that the ammonia concentrations are measured with high precision. Off-Axis Integrating Cavity Output Spectroscopy (OA-ICOS), which has the advantages of high sensitivity and high response speed, is used to design a high-precision ammonia detection device. The gas absorption cell is composed of two high reflection mirrors with a reflectivity of 99.99%, and the base length of the optical resonator is 30 cm. Finally, an optical path of nearly 3000 m was realized. The Distributed Feedback Laser (DFB) with a central wavelength of 1528 nm is tuned to 6548.611 cm-1 and 6548.798 cm-1. The concentration of NH3 is changed from 1×10 -5 to 5×10-5 and is detected under an atmospheric pressure of 18.6 kPa at room temperature. The measurement results show that the linear fit R2 between NH3 concentration and signal amplitude can reach 0.99979. The Allan variance is used to analyze the experimental data, and the minimum detection limit of the system can reach 7×10-9 at 103 s. The experimental results show that the detection device has good stability and high sensitivity, meets the demand for the high-precision detection of ammonia gas, and also provides technical experience for the domestic independent research and development of high-precision detection equipment for trace gases.

Traditional analytical theory design scheme faces problems, such as high computational complexity, limited analytical solution, and high time-consumption. To cambat these issues, based on the design of traditional optical devices, a scheme for designing an optical power splitter with adjustable split ratio according to the reverse design method is proposed. In a compact region of 1.92 μm×1.92 μm, Ge2Sb2Se4Te1(GSST) is introduced to change the refractive index distribution of the device. The direct binary search algorithm is utilized to search the optimal state distribution of GSST in crystalline and amorphous states. A T-shaped optical power splitter with adjustable split ratio is designed and implemented for the same device structure. The initial structure, split ratio, phase change material region state distribution, manufacturing tolerance, and light field distribution of the device are simulated and analyzed. The results show the minimum relative errors of the designed optical power splitters with three splitting ratios of 1∶1, 1.5∶1 and 2∶1 between wavelengths 1530 nm and 1560 nm are 0.004%, 0.14% and 0.22%, respectively. The maximum fluctuations of the transmission curve in the manufacturing tolerance range are 0.95 dB, 1.21 dB and 1.18 dB, respectively. The splitter has a compact structure and great potential for applications in optical communication and information processing.

We develop a fiber Bragg grating accelerometer based on a bearing and flexure hinge for the measurement of medium-high frequency vibration signals. The mathematical model between its natural frequency and sensitivity and structural parameters is derived based on a mechanical model, and the structural design is optimized based on the theoretical analysis results. With these prerequisites, the sensor was fabricated. Ultimately, its dynamic characteristics are validated using a finite element simulation and vibration experiment. The results show that both its operating frequency range and acceleration sensitivity are 10-1200 Hz and 17.25 pm/g. In addition, this proposed sensor has some advantages such as an error of less than 0.3 g, a good linearity of greater than 0.99, a repeatability error of 2.33%, and it is free of temperature.

In order to solve the problem of aberration detection failure caused by double-layer reflected light of the fundus retina in standard animal model mouse during wavefront detection, a mouse eye aberration measurement technique combined with optical mask modulation was proposed to improve the accuracy of wavefront aberration measurement. First, according to the key parameters of mouse retina, we established the optical system model of mouse eye wavefront aberration detection and performed optical simulations. Then, the effects of optical masks with different apertures on the reflection beam of the non-target layer of the retina were analyzed and compared, and then the parameters of the optical mask and the experimental plan were determined. Finally, the wave front aberration detection system of the mouse eye was established, and the wavefront aberration of the mouse eye was measured in vivo. The experimental results show that the optical mask with 0.5 mm aperture can reduce the root mean square error of mouse eye wavefront aberration measurement by 74.9%, which is similar to the shielding effect of non-target layer reflected in 80% of the theoretical simulation. It can effectively block the reflected light from the non-target layer of the mouse retina, improve the detection accuracy of the wavefront aberration of the mouse eye, and lay a foundation for the further realization of high-resolution imaging of the mouse eye.

In the space gravitational wave detection Taiji mission, a heterodyne laser interferometer is used to detect gravitational wave signals in the middle and low frequency bands. In the Taiji mission, the laser interferometry system is composed of multi-channel interferometers, which involves the phase acquisition and readout of multiple sets of the interference signals. Therefore, the multi-channel phase measurement system is one of the key core technologies of the space laser interferometry. In this paper, a multi-channel phase measurement system is proposed, designed and tested based on the requirements of the Taiji mission and its ground-based laser interferometry experiments. First, the hardware and software design of the multi-channel phase measurement system is given, including hardware architecture design, phase measurement algorithm based on digital phase-locked loop and its implementation on FPGA, software architecture design, etc. Second, a time-domain functional tests of the multi-channel phasemeter are performed, which includes the phase accuracy and linearity. The results show that the dynamic and static phase linearity and accuracy of the multi-channel phase measurement system under different working conditions are good. Finally, the frequency domain noise tests of different channels at different frequencies and different amplitudes are carried out. The results show that the phase noise level of the multi-channel phase meter designed in this paper is better than $ 2{\text{π}} {\text{µ}} {\rm{rad}}/\sqrt{{\rm{Hz}}} $ in the frequency band of 0.1 mHz-1 Hz. There is good consistency between different channels, and the phase noise introduced by channel differences or ADC chip differences is negligible in the target frequency band. For any interference signal with a frequency between 5-25 MHz, the phasemeter can meet the requirements within the target frequency band. Therefore, the multi-channel phase measurement system meets the requirements of space gravitational wave detection and ground-based interference experiments. At the same time, the research results of this paper also provide an experimental basis for expanding the phase measurement system with more channels in the future.

In the spaceborne gravitational wave interferometric detection, the problem of stray light has received long-term attention. The laser light emitted by the local interferometer produces backward coherent stray light when passing the telescope while the radiation from space that is incident to the spacecraft produces forward incoherent stray light. Forward incoherent stray light has received less attention at this point, but it is a necessary factor of gravitational-wave telescope design. Therefore, this paper studies stray light produced by space gravitational wave telescopes in orbit. First, the annual solar angle is calculated according to the orbital data of the three-star satellite formation of the Taiji Project, and the solar radiation around the 1064 nm band is evaluated. The baffle shadowing function is derived, which satisfies the requirement for the baffle design. The telescope is then modeled optically and mechanically and scatter measurements are conducted for critical optical components. Finally, the stray light reaching the pupil of the telescope is determined based on the energy of the incident sunlight. The results show that when the angle between the incident light and the optical axis is 60°, the stray radiation at the exit pupil is 3.9×10-12 W, and the corresponding point source transmittance is 8.7×10-9 which meets the requirement for space gravitational waves to detect extremely low levels of stray light.

To solve the high false alarms caused by complex background clutters in infrared small-target detection, a novel detection method based on ${L_{1 - 2}}$ spatial-temporal total variation regularization is proposed. First, the input infrared image sequence is transformed into a Spatial-Temporal Infrared Patch-Tensor (STIPT) structure. This step can associate the spatial and temporal information by using the high dimensional data structures in the tensor domain. Then, weighted Schatten p-norm and ${L_{1 - 2}}$ spatial-temporal total variation regularization are incorporated to recover the low-rank background component to preserve the strong edges and corners, which can improve the accuracy of sparse target component recovery. Finally, the STIPT structure can be transformed into an infrared image sequence by the inverse operator, and an adaptive threshold segmentation is used to obtain the real target. The method is verified using a contrast test with other five methods, and the experimental results show that the false alarm rate by this method decreases to 71.4%, 71.7%, 68.5%, 74.3% and 20.47% compared with the Maxemeidan, Tophat, LIRDNet, DNANet and WSNMSTIPT algorithms. The time cost also decreased to 42.4%, 82.9% and 28.7% of that of the Maxemeidan, DNANet and WSNMSTIPT. The extensive experimental results demonstrate the superiority of this method in detection performance, which can greatly improve the accuracy and efficiency of target detection with complex background clutters.

In order to better preserve high-frequency information in demosaicing multispectral images, we propose a new demosaicing method for multispectral images based on an improved guided filter. Firstly, the strong correlation between adjacent pixels based on the autoregressive model is constructed, gradually estimates the model parameters at each pixel, and the optimal estimation value is obtained by minimizing the estimation error in the local window, interpolates the sampling dense band G, and generates high-quality guide images. The windowed intrinsic variation coefficient is then introduced into the penalty factor to obtain a weighted guide filter with edge sensing ability and to reconstruct the remaining sparse sampling bands. Finally, the CAVE dataset and the TokyoTech dataset are used for simulation. The experimental results show that compared with the mainstream five-band multispectral image demosaicing method, the peak signal-to-noise ratio and structure similarity of the reconstructed image in the CAVE dataset and the TokyoTech dataset are improved by 3.40%, 2.02%, 1.34%, 0.30% and 6.11%, 5.95%, 2.28%, 1.42%, respectively. The local structure and color information of the original image are also better preserved, and the edge artifacts and noise are reduced.

Vehicle infrared image target detection is an important way of road environment perception for autonomous driving. However, existing vehicle infrared image target detection algorithms have defects, such as low memory utilization, complex calculation and low detection accuracy. In order to solve the above problems, an improved YOLOv5s lightweight target detection algorithm is proposed. Firstly, the C3Ghost and Ghost modules are introduced into the YOLOv5s detection network to reduce network complexity. Secondly, the αIoU loss function is introduced to improve the positioning accuracy of the target and the networks training efficiency. Then, the subsampling rate of the network structure is reduced and the KMeans clustering algorithm is used to optimize the prior anchor size to improve the ability to detect of small targets. Finally, coordinate attention and spatial depth convolution modules are respectively introduced into the Backbone and Neck to further optimize the model and improve the feature extraction of the model. The experimental results show that compared with the original YOLOv5s algorithm, the improved algorithm can compress the model size by 78.1%, reduce the number of parameters and Giga Floating-point Operations Per Second by 84.5% and 40.5% respectively, and improve the mean average precision and detection speed by 4.2% and 10.9%, respectively.

The resolution of optical imaging is limited by the diffraction limit, system detector size and many other factors. To obtain images with richer details and clearer textures, a multi-scale feature attention fusion residual network was proposed. Firstly, shallow features of the image were extracted using a layer of convolution and then the multi-scale features were extracted by a cascade of multi-scale feature extraction units. The local channel attention module is introduced in the multi-scale feature extraction unit to adaptively correct the weights of feature channels and improve the attention to high frequency information. The shallow features and the output of each multi-scale feature extraction unit were used as hierarchical features for global feature fusion reconstruction. Finally, the hight-resolution image was reconstructed by introducing shallow features and multi-level image features using the residual branch. Charbonnier loss was adopted to make the training more stable and converge faster. Comparative experiments on the international benchmark datasets show that the model outperforms most state-of-the-art methods on objective metrics. Especially on the Set5 data set, the PSNR index of the 4× reconstruction result is increased by 0.39 dB, and the SSIM index is increased to 0.8992, and the subjective visual effect of the algorithm is better.

In this paper, an image super-resolution reconstruction multi-scale algorithm based on a residual attention network (SMRAN) is proposed to solve the problems caused by low resolutions, less texture information and blurred details in colorectal endoscopic images. Images from the colorectal polyp endoscope image dataset PolypsSet are selected as the raw data for these experiments. A convolutional network is built to extract the shallow features of the low-resolution image and a Res-Sobel block is designed to enhance its edge features. A multi-scale feature fusion block MEB is designed by introducing convolution kernels of different sizes to adaptively extract image features of different scales and obtain effective image information. The Res-Sobel block and multi-scale feature fusion module block MEB are connected through the residual attention network. Finally, a high-resolution image is reconstructed at the sub-pixel convolution layer. When the amplification factor is ×4, the performance of the proposed algorithm on the test set are as follows: the peak signal-to-noise ratio (PSNR) is 34.25 dB and the structural similarity (SSIM) is 0.8675. Compared with the traditional bicubic interpolation algorithm and commonly used deep learning algorithms such as SRCNN and RCAN, the proposed SMRAN algorithm shows better super-resolution reconstruction results on colorectal endoscopic images.

In order to study the coupling and refractive index sensing properties of a metasurface, asymmetric parallel nanorod dimers consisting of two nanorods with different lengths was proposed and designed. In this paper, the finite element method is used to simulate the optical properties and a quasi-static approximation model is used to explain the coupling mechanism of double parallel nanorods. The transmission spectra, electric field at the resonant peak, charge distribution and the influence of structural parameters on the transmission spectra are studied. The electric field distribution is simulated at the resonance wavelength, the electron vibration mode is analyzed, and asymmetric double Fano resonance appears in the transmission spectrum. The results show that the double Fano resonance is generated by the coupling between the nanorods and the substrate, and the double Fano resonance can be regulated by the structural parameters and the refractive index of the surrounding medium. The sensitivity of the refractive index based on the Fano resonance can reach 1.137 μm/RIU. These results provide a theoretical basis for the design of a surface plasmon refractive index sensor.

A filterless Microwave Photonic Phase Shifter (MPPS) with a tunable Frequency Multiplication Factor (FMF) and a full 360-deg tunable range is theoretically analyzed and verified by simulation. In the scheme, two parallel Mach-Zehnder Modulators (MZM), cascaded with two Dual-Parallel integrated Mach-Zehnder Modulators (DPMZM) by a 2×2 Optical Coupler (OC), are used to generate the ±1st- to 4th-order sidebands adjustably, and a Phase Modulator (PM) is used to phase shift one of the two lightwaves. After photodetection, the 2nd- to 8th- order harmonics with a continuously tunable phase shift from 0 to 360-deg can be generated by adjusting the RF driving signal and the DC bias voltage of the DPMZM, and the DC voltage of the PM. Simulation results demonstrate that both 360-deg continuously tunable phase shift and frequency multiplication can be implemented. Large Optical Sideband Suppression Ratio (OSSR) and Electrical Spurious Suppression Ratio (ESSR) of around 20 dB can be obtained. The phase shifter wavelength insensitive performance has been also evaluated by simulation.

In this paper, the coplanar excitation of terahertz Spoof Surface Plasmon (SSP) realized by using a single-layer grating meta-surface coupling method is proposed, which overcomes the disadvantages such as the reflection measurement when applying the medium couplers. The periodic grating and terahertz SSP composite structure are simultaneously constructed on the monolayer metal structure. When the terahertz waves are incident vertically, the wave vector of grating structures and the wave vector of SSPs are matched, and the SSP mode can be excited. The high Q value resonant peaks can be generated in the transmission spectrum, and the Q factor can reach 1923. The effects of the structural parameters on the grating-coupled meta-surface transmission spectrum and dispersion characteristics are also analyzed. In addition, based on the high Q resonant peak in the transmission spectrum of the designed structure, the high sensing sensitivity is about 67 GHz/RIU at the resonant center frequency of 0.22 THz. The structure proposed in this paper, which realizes terahertz SSP excitation and high Q sensing by treating a single-layer meta-surface structure, exhibits great application potential in many practical applications.

An interferometric measurement method is proposed to measure the Total Thickness Variation (TTV) and the Bow and Warp in the deformation of a double-sided polished wafer. Two phase-shifting Fizeau interferometers with reference mirrors are used to measure the topography of the front and back surfaces of the wafer simultaneously, and the measured topography of the front and back surfaces of the wafer are combined with the cavity topography of the two interferometers when the wafer is not placed to obtain the surface parameters of the double-sided polished wafer which are not affected by the reference mirror error. In the combined operation, the mapping error is introduced because the two reference mirrors are not precisely aligned, which affects the measurement results of the relevant parameters. To this end, before wafer measurement, the three-point positioning device is fixed between the two reference mirrors, and the position of the two reference mirrors is continuously adjusted based on the three-point circular theorem, which can make the mapping error extremely small, thereby reducing the influence of the mapping error on the measurement results. The experimental results show that the mapping errors of 50 mm wafer transverse and longitudinal directions are 21.592 μm and 37.480 μm, respectively, and the TTV, Bow and Warp are 0.198 μm, -0.326 μm and 1.423 μm, respectively. In order to further verify the effectiveness of the adjustment method, a single interferometer was used to flip the wafer for measurement, and the TTV, Bow and Warp of wafer are 0.208 μm, -0.326 μm and 1.415 μm, respectively. The proposed interferometric method can be easily and quickly used for the measurement of large quantities of large-sized wafers after adjusting the position of two reference mirrors, which improves wafer inspection efficiency. At the same time, it has a superior measurement accuracy.

In order to effectively suppress the interference of CO2 radiation 4.3 μm on MWiR target signal with wavelength of 3 μm-5 μm, based on the Needle random intercalation optimization algorithm, an accurate inversion correction model for the growth error of multi-layer ultra-thick Ge/Al2O3 films under quartz crystal monitoring is established by the electron beam evaporation method, thus realizing the design, the accurate inversion and the accurate preparation of MWiR notch filter. In order to solve the problem that the surface profile of the MWiR notch filter changes greatly, the preset substrate surface method is used to realize the low surface profile regulation of MWiR notch filter. The results show that the high refractive index Ge film has good deposition stability with the increase of coating time, while the deposition scale factor of low refractive index Al2O3 thin film changes up to 11.9% in a regular gradual trend. For the prepared MWiR notch filter, the average cut-off transmittance is less than 0.3% in the wavelength range of 4.2 μm-4.5 μm, and the average transmittances are more than 95% in the wavelength range of 3.5 μm-4.05 μm and 4.7 μm-5.0 μm. The surface profile of the substrate after coating can be effectively controlled in a small range. The film has good adaptability to complex environment, and has successfully passed the environmental test of firmness, high temperature, low temperature and damp heat specified in GJB 2485-95.

The optical encrypted metasurface based on one-dimensional grating diffraction requires the processing of mask or unit structure one by one, resulting in low efficiency. In addition, the poor uniformity of the structure formed by conventional ablated LIPSS can also affect device performance. Aming at the above problems, an optical metasurfaces processing method is proposed based on modified structures obtained by picosecond laser direct writing phase-change material Ge2Sb2Te5. Firstly, the dispersion properties of the prepared GST-modified gratings are first characterized, and the angle-multiplexed information encryption metasurfaces are designed by combining the polarization dependence of the modified grating, and the metasurface prepared by the proposed method is further demonstrated. In addition, the performance of encryption under natural light conditions and selective decryption reading and dynamic display under strong light conditions has been achieved. Compared to the conventional processing method, the proposed method can generate a series of grating structures in the form of simultaneous printing in a direct writing process, which improves the processing efficiency. At the same time, the grating structure obtained by processing has good uniformity and consistency, which improves the color rendering effect. A modified grating with an orientation angle difference of 16° is used to realize selective information reading without crosstalk resulting in uniform and bright structural colors. The processing strategy proposed in this paper has a profound application prospect in the fields of anti-counterfeiting, information encryption storage and wearable flexible display devices.

In order to realize the real-time measurement of the boresight vibration of the dual line array surveying and mapping camera, a measurement model of the optical axis of the aerospace line array surveying and mapping camera is established. First, by setting up laser transceivers at both ends of the focal plane of the camera, through the central prism correlation, an angle parameter change measurement model for the two cameras is constructed. An optical axis measurement method for multi-line array cameras based on the dual-vector attitude determination principle is proposed. The calculation expression is given and the algorithm error is analyzed, which is verified by simulation. In addition, the residuals of the two algorithms are simulated and the results show that the simplified algorithm is only in good agreement with the dual vector algorithm in a small measurement range but when the detection range is expanded to 2 seconds, the algorithm in this article can be used to obtain 0.1 arc-second. Finally, the algorithm was tested and verified in a thermal vacuum environment, which verified that the calibration accuracy of the internal and external parameters of the camera using this algorithm reached 0.1 arc-second. The results showed that the angle parameters of the two cameras exhibited the periodicity of the orbit, which provided good conditions for the subsequent development of stereo surveying and mapping tasks.

Tacking the research of glass lenses as reference, a statistical data-based index of liquid lens zoom stability and liquid lens repeated zoom accuracy is proposed. An experimental method is presented to optimize the structural parameters and materials of the liquid lens. Firstly, the main factors affecting the accuracy of a liquid lens’ repeat zoom accuracy were obtained through preliminary experimental research, including the polar solution volume, taper and non-polar solution viscosity. Secondly, taking the accuracy of the liquid lens’s repeat zoom accuracy and zoom range as evaluation indicators, it was found that the relationship between the accuracy of the liquid lens’s repeat zoom and the voltage is not monotonic, and that it rises first and then falls. On this basis, through the range analysis and comprehensive balance method, the primary and secondary factors and the optimal combination of parameters is obtained. After that, orthogonal experiments were used to optimize the design parameters. Finally, the effectiveness of this method was verified by experiments. The experimental results show that the repeat zoom accuracy of the optimized liquid lens is 0.2 m-1, and the zoom range is -15.2-5.85 m-1 over the voltage range of 0 to 230 V. It basically meets the requirements of stable and reliable, high precision, and large zoom range for liquid lens zoom.

In order to realize tunable longwave infrared laser, we design a ZGP temperature tuned longwave infrared optical parametric oscillator. A Ho:YAG laser with the center wavelength of 2097 nm is used to pump ZGP crystals with different phase matching angles. The temperature adjustable properties of ZGP-OPO is researched by changing the operating temperature of crystal. The laser with a segment continuously tunable range of 7.53-8.77 μm is realized in the temperature range of 15-30°C, with a total tuning range of 1.24 μm. The output power of ZnGeP2-Optical Parametric Oscillator(ZGP-OPO) is greater than 1.503 W over the entire tuning range. The output power is 1.503 W at the idler wavelength of 8.77 μm, and the corresponding slope efficiency and optical conversion efficiency are 12.19% and 6.53%, respectively. The experimental results show that temperature tuning of ZGP is an effective technical method to obtain continuously tunable long-wave infrared laser. This research has potential application value in the field of engineering of tunable long-wave laser.

Under conditions with large temperature differences, the imaging quality of an infrared optical system will deteriorate due to severe temperature changes. Large field-of-view medium-wave infrared cameras for airborne forest fire monitoring work in drastically changing environments, so the optical system has high requirements for stray radiation. In order to ensure that the optical system performs stably and with good imaging quality in the large field-of-view and the required large temperature range, a cooled medium-wave infrared optical system is designed based on athermalization and the comprehensive evaluation method of stray radiation based on noise equivalent temperature difference. The optical system consists of 6 lenses and 1 filter with working wavelength of 3.7-4.8 μm, F-number 2.5, focal length 62.5 mm, and field of view 14.36°×10.87°, respectively. The pixel resolution of the medium-wave cooled detector is 640×512. By using a combination of silicon and germanium materials and reasonably distributing the optical power, achromatic aberration and athermalization designs are realized. Through cold reflection optimization and cold aperture matching, stray radiation noise in the system is well-suppressed. By a bit of aspheric optimization, higher-order aberrations are corrected based on the requirements. The results show that the imaging quality of the optical system is stable and good in the temperature range of -55~+70 °C.

In order to overcome the adverse effects of near-ground turbulence on the imaging quality of the optical systems at imaging distances of tens to hundreds of meters, an optical imaging system based on a long focal length telescopic objective lens and an integrated adaptive module is designed. With a system center height of 1.9 m and the imaging distance of 50-200 m, the outdoor imaging experiment of a resolution plate is carried out. The experimental results show that the influence of turbulence on imaging quality is obvious at medium and long distances of 50-200 m near the ground. The experimental system can effectively overcome the influence of turbulence at different distances and improve the consistency of image resolution and clarity. As the imaging distance increases, the influence of turbulence increases, and the system’s correction ability and the imaging quality decrease. The imaging resolution of the system can reach 0.5 mm at an imaging distance of 100 m. Cracks on the surface of a concrete model are observed and corrected at a distance of 200 m. The experimental results show that the system can suppress the influence of turbulence and improve the clarity of the image, which verifies the practical application ability of the system.

Multiple sub-aperture interference imaging enables the images formed by the sparse aperture imaging system to have a higher resolution after the cophasing error is corrected. In this paper, the MTF and surface target imaging of the system are analyzed with a Golay3 sparse aperture imaging system as the research object when there are different piston and tilt errors among the sub-apertures. A Golay3 sparse aperture imaging system was developed to carry out an imaging experiment with the USAF1951 resolving power test target as the area target. Three-aperture synthetic imaging is achieved by adjusting the position of the plane mirror in the light beam deflection and the adjustment module to correct the piston and tilt errors of the sub-apertures. The results of a theoretical analysis are then verified. According to calculations, the developed system’s angular resolution of 1.38 μrad is close to the equivalent single-aperture imaging system’s theoretical resolution of 1.18 μrad. The developed Golay3 sparse aperture imaging system can correct the cophasing errors and improve the imaging resolution.

In order to improve the quality value (Q) to enhance the coupling between light and matter. In this paper, a dielectric metamaterial with simple structure, low fabrication requirements was proposed. It can excite symmetric protected bound states in the continuum (BICs). The dielectric metamaterial has a planar nanopore plate composed of tetrameric pores. By changing the position of the nanopores, the symmetrical protection BIC can be transformed into the symmetrical protection quasi BIC(QBIC), and then two high Q value Fano resonances can be induced. Through simulation calculation, the Fano resonance Q value can reach 1×e6 when Δ=3 nm. Then, the far-field radiation of QBIC and Fano resonance is decomposed into the contributions of different multipole components. Based on the scattering power and electric field vector distribution, it can be found that the dielectric metamaterials λ1 Fano resonance with high Q value is mainly due to magnetic quadrupole and toroidal dipole, while λ2 Fano resonance has high Q value is mainly due to the toroidal dipole. Finally, the influence of nanopore side length and nanopore filling material on the two Fano resonances is analyzed and calculated. The research in this paper can provide theoretical guidance for the future research and preparation of high Q value optical response devices.

In this paper, a metamaterial Fano resonance design method based on deep learning is proposed to obtain high-quality factor (high-Q) resonances with desired characteristics, such as linewidth, amplitude, and spectral position.The deep neural network is used to establish the mapping between the structural parameters and the transmission spectrum curve. In the design, the forward network is used to predict the transmission spectrum, and the inverse network is used to achieve the on-demand design of high Q resonance. The low mean square error ( MSE ) is achieved in the design process, and the mean square error of the training set is 0.007. The results indicate that compared with the traditional design process, using deep learning to guide the design can achieve faster, more accurate, and more convenient purposes. The design of Fano resonance can also be extended to the automatic inverse design of other types of metamaterials, significantly improving the feasibility of more complex metamaterial designs.

The machining quality and detection accuracy of aero-engine blades have a very important influence on their service life of blades. To improve the accuracy of blade detection, a high-precision scanning viewpoint planning method based on structured light is proposed in this paper. Firstly, coarse model data was obtained by coarse scanning under the overall size of the blade, and the field of view was determined according to the camera resolution and acquisition accuracy. Secondly, an improved Angle Criterion algorithm was used to extract the boundary, and the boundary segmentation points were determined according to the boundary coordinates and the range of the visual field. The coarse model was sliced by the section line method for a surface, and the internal segmentation points were determined according to the slice results to complete the uniform segmentation of point clouds. Then, a directed bounding box was established for the segmented point cloud data to obtain the coordinates of the center point, and the normal vector was statistically analyzed to determine the orientation of the main normal to generate the viewpoint coordinates for high-precision scanning. Finally, the surface morphology of the blade was tested and verified. The experimental results show that the average standard deviation of the proposed method is reduced by 0.0054 mm and the collected viewpoint is reduced by 1/3 compared with the viewpoint acquisition result of the supervoxel segmentation, which has good application prospects in the machining inspection of thin-walled blades.

In order to realize the non-contact high-precision measurement of high-temperature temperature fields such as the tail flame, combustion and explosion of aerospace engines, a static interferometric high-temperature temperature field imaging and detection method is studied. Firstly, a static interference high-temperature temperature field detection system is designed. On the basis of theoretical analysis of the measurement principle of high-temperature temperature fields, the relationship between the optical path difference and the temperature at the lowest point of high-temperature interference signal intensity is studied. Secondly, according to the response band of the visible light area array detector and the common temperature range, a static interferometric Savart prism is designed, and temperature field imaging is realized by using it for one-dimensional scanning. Finally, the optical system is designed and the corresponding relationship between the minimum optical path difference of the interference and the temperature is obtained by fitting. From this, the linear fitting formula is obtained. Simulations are conducted to verify the interference signal image where the temperature field after passing through the system reaches the area detector. The static interferometric high-temperature temperature field detection method can achieve the high-precision detection of 1000 K-3000 K temperatures. In the linear region, the temperature measurement resolution is 1.4 K and the temperature measurement relative error is better than 0.8%. This research lays the foundation for high-precision high-temperature temperature field imaging in the military and civilian fields.

Flow cytomicrographic analysis is an important development in the automatic identification of planktonic algae in a water column, but the accuracy of this process is affected by the deformation of microscopic images under rapid injection conditions. Based on a microfluidic-microscopic imaging system for planktonic algae, the effects of flow rate on the deformation of microscopic images were investigated by analyzing the deformation of algal cells and image clarity at different injection flow rates. Based on the principle of deformation caused by photographing a moving object using a rolling shutter, a method of image deformation correction with unidirectional offset pixels is proposed and analyzed by comparing its results with images acquired under static conditions of algal cells. The experimental results showed that the average aspect ratio and sharpness of L values for oocystis cell images under static conditions were 1.16 and 116.53, respectively; during the dynamic injection process, the deformation (aspect ratio) of the cell images gradually increased and the sharpness decreased as the flow rate increased; the average values of aspect ratio before and after correction were 1.35 and 1.26 respectively at 95µL/min injection flow rate, and the dispersion of deformation decreased from 0.33 before correction to 0.1. The results are close to that of static cell morphology and the image sharpness is basically same. The results provide a method for improving the accuracy of the automatic identification of planktonic algal cells in a water column.

In the positioning process of aerial cameras with large inclination angles, the influence of height error in the earth ellipsoid model can be effectively solved with the help of a digital elevation model (DEM). This is very important for obtaining accurate ground coordinates, especially elevation. Firstly, the orientation of the line-of-sight angle in the geographic coordinate system is solved by transforming homogeneous coordinates according to the position and attitude information of the carrier aircraft and the frame angle information of the aerial camera, and then the longitude and latitude of the target point are determined by a digital elevation model. To overcome the tedious nature of calculating target elevation and the non-convergence in the imaging process, a fast iterative method is proposed to iterate over the target elevation’s value. The difference between the light elevation of the visual axis and the ground elevation is calculated by halving the target elevation. The median elevation difference is calculated iteratively until it is less than a certain threshold. Finally, Monte Carlo analysis was used to analyze the error terms in the whole imaging process. When the convergence threshold is 1/10 DEM in grid accuracy, the iteration efficiency increases by 45.5% and the convergence speed is greatly improved. Through the calculation of the digital elevation model, when the flight height is 15,409 meters and the camera frame’s angle is greater than 74°, a mountainous area’s target circular error probability is less than 200 m which meets the real engineering needs.

In the Taiji program, laser interferometry is utilized to detect the tiny displacement produced by the gravitational wave signals. Due to the large-scale unequal arm, the laser frequency noise is the largest noise budget in the space interferometer system. To reduce the influence of laser frequency noise, a technology called the Time Delay Interferometry (TDI) is utilized to deal with it. The TDI is a kind of data post-processing method, which forms the new data stream by the method of the time delay to initial data. But the premise of TDI needs to obtain accurate absolute arm length between satellites. Thus, for that requirement, we discuss the ranging system scheme and implement a ground electronics verification experiment. The ranging system is based on Direct Sequence Spread Spectrum (DS/SS) modulation, and it mainly includes three parts, which are the signal structure, a Delay Locked Loop (DLL), and a data processing algorithm. In DS/SS modulation, types of pseudo-random code can make a difference to the quality of correlation and the ranging accuracy. Therefore, to design the optimal pseudo-random code, we compare the correlation and flexibility in choosing lengths of the m sequence, gold sequence, and Weil code. Weil code that has a shift-cutoff combination with the best autocorrelation is chosen as the ranging code. The ground electronics verification experiment is set up for simulating the physical process of signal transmission and verifying system performance. The main device of the experiment is a FPGA card based on the K7 chip from Xilinx, which is used to simulate the function of communication and ranging between satellites. Meanwhile, we change the length of the Radio Frequency (RF) coaxial cable to correspond to different ranges. The experimental process can be summarized as follows. Firstly, 16-bit data at 24.4 kbps and 1024-bit Weil code at 1.5625 Mbps are modulated with Binary Phase Shift Keying (BPSK) in the 50 MHz sampling frequency. Then the signal is transmitted through RF coaxial cables of 10 to 60 m in length. In receiving end, the signal is consolidated by DLL and the ranging information is collected. To measure the range accurately, we use a centroid method to optimize the collected data. The results show that the ranging accuracy is better than 1.6 m within 60 m. In conclusion, this experiment proves the principle of the scheme and its feasibility, laying a technical foundation for optical system verification in the future.

In order to eliminate the uncertainty caused by the inclination of a beam, a dual polarization laser Doppler velocimetry system is established. We use a structure with two beams and two probes to detect the motion of the object. Firstly, the angle between the two beams is obtained by a calibration experiment. For any beam inclination, the scattered beam on the surface of a moving object is collected by a dual-probe device, and the Doppler shift of the two interference signals is obtained by combining the dual polarization optical path structure. Then, the refined framing algorithm is applied to demodulate the two interference signals in real time. The real speed of the object is obtained through the synthesis of the two speed components. The experimental results show that the average deviation between the measured value and the theoretical value can reach 1%-5% when the speed is within the range of 10 mm/min~1500 mm/min. In the process of non-stationary motion, the mean RMSE of the v-t image corrected by the refining frame segmentation algorithm is 1.19 mm/min. The system’s structure meets the requirements of stability and reliability, high precision and strong anti-interference ability in speed measurement.

In order to accurately measure the laser intensity distribution, we propose a method based on tomographic imaging. Firstly, numerical studies were performed to validate the correctness of the imaging model and convergence of the reconstruction algorithm. Reconstruction errors were less than or equal to 7.02% with different laser intensity distribution phantoms employed and less than 8.5% with the addition of different random noise levels under 10%. Additionally, a demonstration experiment was performed with the employment of a customized fiber bundle to realize the measurement from seven views. Seven views are distributed along a semi-circle plane which is perpendicular to the propagation direction of the laser beam. The distance from the laser beam to each view is nearly 160 mm and the angle coverage range of the seven views is about 150°. Laser-induced fluorescence obtained after the laser passed through a rhodamine-ethanol solution was collected by the tomographic imaging system. Then, the laser intensity distribution was obtained through absorption-corrected three-dimensional (3D) reconstruction. The correlation of the projection and re-projection of the one view was used to quantitatively access the accuracy after the other six views were adopted in the reconstruction. The results show the feasibility of the method with a correlation coefficient of 0.9802. It can be predicted that the 3D laser intensity measurement scheme proposed in this work has a broad prospect in the field of laser applications.

We propose a method for improving the computational efficiency of passively mode-locked fiber laser, which is composed by Symmetric Split-step Fourier Method (SSFM) and the Global-Error-Local-Energy (GELE) method for solving propagating equations. Our proposed method relies on the limitation of local energy increment related with global error within a certain value to control the selection of step size. This method has advantage of an automatic step adjustment mechanism. To achieve the same order of computation accuracy, the computational time of our method is 255 s, while SSFM with small constant step size method needs to calculate 3855 s. The computational time of our proposed method is one or two orders of magnitude less than that of the SSFM, which indicates our method can enhance the computational efficiency by a factor up to 10. It could be expanded with high-order algorithms, such as the fourth-order Runge-Kutta in the interaction picture (RK4IP), Adams, predictor–corrector, etc. for improving the accuracy.

To gain better phase measurement results in nonlinear measurement systems, a phase measurement method that uses dual-frequency grating after reducing the nonlinear effect is proposed. Firstly, the nonlinear effect of the phase measurement system is discussed, the basic reason for the existence of high-order spectra components in the frequency domain is analyzed, and the basic method used to reduce the nonlinear effect and separate fundamental frequency information is given. Then, on the basis of reducing the nonlinear effect’s influence on the system, the basic principle of phase measurement for the fringe image of a measured object using the dual-frequency grating method is analyzed. To verify the correctness and effectiveness of the proposed phase measurement method, a computer simulation and a practical experiments were implemented with good results. In the simulation, the error value of this method was 27.97% for the method with nonlinear influence, and 52.51% for that with almost no nonlinear influence. In the experiment, the effect of phase recovery produces the best results. This shows that the proposed phase measurement method is effective with a small error.

A fabric image retrieval algorithm based on fractal coding and Zernike moments under a wavelet transform is proposed, which can quickly and accurately retrieve images from a database that are similar to fabric images submitted for retrieval. Firstly, the low-frequency component is obtained by a wavelet transform, and the transformed low-frequency sub-image is fractally encoded to obtain its coding parameters. Then, the Zernike moment of the low-frequency sub-image is calculated. The fractal coding parameters and Zernike moment under a wavelet transform are combined as the fabric image retrieval characteristic. The algorithm overcomes the problems of low retrieval accuracy and the high time consumption of direct feature extraction under a single feature. Compared with the Basic Fractal Image Compression (BFIC) algorithm, the joint orthogonal fractal parameters with the improved Hu invariant moment and Variable bandwidth Kernel density estimation of Fractal parameters (HVKF) algorithm and the Sparse Fractal Image Compression (SFIC) algorithm, the proposed algorithm ensures the quality and lower encoding time of the reconstructed image. The experiments show that the average precision and average recall of fabric image retrieval are higher than those of existing methods.

We propose a “leaf-type” hybrid metamaterial to realize bandwidth-tunable half-wave plate based on vanadium dioxide (VO2) phase transition. The hybrid metamaterial is regarded as a hollow “leaf-type” metallic structure and act as a dual-band half-wave plate when VO2 film is in the insulating phase. Within 1.01-1.17 THz and 1.47-1.95 THz, it can accomplishy- to x-polarization conversion with a polarization conversion rate over 0.9 and an average relative bandwidth of 26%. The metamaterial becomes a solid core “leaf-type” metallic structure when VO2 is in the metallic phase. Within 1.13-2.80 THz, it can act as a broadband half-wave plate with a relative bandwidth of 85%. The working principle of the bandwidth-tunable half-wave plate is explained by the instantaneous surface current distribution and electric field theory in detail. The proposed “leaf-type” hybrid metamaterial half-wave plate has potential application prospects in THz imaging, sensing and polarization detection.

Aiming at the problem that the optical frequency scanning nonlinearity affects the phase extracting accuracy of the optical Frequency Scanning Interferometry (FSI) signal, and thus reduces the FSI ranging accuracy, a phase-extracting method based on the Complementary Ensemble Empirical Mode Decomposition and Hilbert Transform (CEEMD-HT) algorithm is proposed in this paper. Based on theoretical derivation and simulation analysis of the CEEMD-HT algorithm, the effectiveness of the algorithm in solving the phase of the non-stationary interference signal in scanning-frequency is verified by simulation. Further simulation experiments were implemented by using the real output optical frequency obtained with FSI ranging system as the simulation conditions. The simulation results showed that the CEEMD-HT algorithm significantly improved the phase extracting accuracy of the interference signal and the FSI ranging accuracy. Finally, the proposed interference signal phase-extracting method was verified via the experiment of the FSI ranging system. The results showed that the ranging repeatability of the measurement system based on the CEEMD-HT algorithm was 2.79 μm in the free space measurement range of 2 m. Compared with EMD-HT and direct measurement methods, the ranging repeatability was improved by 5.19 times and 8.28 times, respectively.

This paper focuses on the field of automobile passive safety in my country. By scanning the Hybrid III 50th automobile crash dummy, a finite element simulation model of the dummy chest is constructed. The genetic algorithm is used to optimize the parameters. After optimization, all the indicators of the calibration test meet the requirements of the regulations. The simulation results are consistent with the experimental test results, and the error is less than 5%. Then we put the finite element dummy model containing the chest model into the vehicle system for frontal collision simulation analysis. The results show that the score of chest injury is 80%, and the error of the simulation results is less than 10% compared with the test results. The model has a good degree of simulation and can be used for the study of vehicle crash safety performance.

3D reconstruction technology is one of the most popular research directions in machine vision, and has been widely used in the fields of unmanned driving and digital processing and production. Traditional 3D reconstruction methods include depth cameras and multi-line laser scanners, but the point clouds obtained by depth cameras have incomplete and inaccurate information, and the high cost of multi-line laser scanners hinders their application and research. To solve these problems, a three-dimensional reconstruction method based on a rotating two-dimensional laser scanner was proposed. First, a stepper motor was used to rotate a 2D laser scanner to obtain 3D point cloud data. Then, the position of the laser scanner was calibrated by multi-sensor fusion, and the point cloud data was matched by transforming the coordinate system. Finally, the collected point cloud data were filtered and simplified. The experimental results show that compared with depth camera/IMU data fusion, the reconstruction method’s average error of the proposed method is reduced by 0.93 mm, and it is 4.24 mm, the accuracy has reached the millimeter level, and the error rate is also controlled within 2%. The cost of the whole set of equipment is also greatly reduced compared to the multi-line laser scanner. It basically meets the requirements of high precision and low cost and retaining the shape characteristics of the object.

Three-dimensional reconstruction is a common method for cultural relics information conservation, mainly through point cloud alignment technology to reorganize the spatial point cloud information of cultural relics, and its alignment accuracy has an important impact on cultural relics recovery. To address the problems of low accuracy and poor robustness in the alignment of complex point cloud texture features on the surface of cultural relics, this paper proposes a local point cloud alignment method based on normal vector angle and faceted index features. Firstly, the normal vector angle and covariance matrix thresholds are set according to the point cloud planar characteristics, and the point cloud feature points satisfying both features are extracted; secondly, the point cloud local feature point set is extracted by the K-nearest neighbor search methhod, and the two sets of point cloud center-of-mass positions are overlapped by rigid transformation for coarse alignment; finally, the nearest points are iterated based on ICP for fine alignment. By comparing with the traditional ICP, the point cloud alignment error of the proposed method reduces by 3% and the matching time reduces by 50%, which effectively improves the accuracy and efficiency of alignment and enhances the robustness of point cloud alignment.

In order to improve the performance of lane detection algorithms under complex scenes like obstacles, we proposed a multi-lane detection method based on dual attention mechanism. Firstly, we designed a lane segmentation network based on a spatial and channel attention mechanism. With this, we obtained a binary image which shows lane pixels and the background region. Then, we introduced HNet which can output a perspective transformation matrix and transform the image to a bird’s eye view. Next, we did curve fitting and transformed the result back to the original image. Finally, we defined the region between the two-lane lines near the middle of the image as the ego lane. Our algorithm achieves a 96.63% accuracy with real-time performance of 134 FPS on the Tusimple dataset. In addition, it obtains 77.32% of precision on the CULane dataset. The experiments show that our proposed lane detection algorithm can detect multi-lane lines under different scenarios including obstacles. Our proposed algorithm shows more excellent performance compared with the other traditional lane line detection algorithms.

A white light interferometry micro measurement algorithm based on principal component analysis is proposed to solve the problem of the phase solution in white light interferometry and realize the height measurement of micro morphology. The white light microscopic interference system is used to collect multiple interferograms and reconstruct them into vector form. From a set of interferograms, the background illumination can be estimated by a temporal average, eliminating background light components. Then, the eigenvalues and eigenvectors representing the original data are obtained by a matrix operation. Finally, the phase distribution is calculated by the arctangent function. Experimental results indicate that the measurement result of a standard step height of 956.05 nm by the proposed method is about 953.66 nm and the solution is approximately consistent with the iterative algorithm. In comparison to the iterative algorithm, the processing speed of the proposed method is 2 orders of magnitude faster. The interference fringes with surface roughness of 0.025 μm is analyzed, the mean of the surface roughness calculated by the proposed method is 24.83 nm, and the sample’s standard deviation is 0.3831 nm. The proposed method improves the deficiency of monochromatic interferometry and has the advantages of high speed, low computational requirements and high accuracy.

In order to achieve accurate target ranging of weak or non surface texture features using a monocular camera, an improved defocused image ranging algorithm based on preserving edge spectral information is presented. By comparing two classical defocal ranging theories with Fourier transform and Laplace transform as the foundational principals of calculation, a corresponding definition evaluation function is constructed. We select the method based on the spectrum definition function with better sensitivity, and select the calculation range of the frequency domain by retaining the information on the target edge. To verify the feasibility of the algorithm, 6 sets of different duck egg samples are used to obtain scattered focus images of different apertures and distances, and the improved algorithm was used to solve the distance of the duck eggs from the camera lens. The experimental results show that the improved algorithm based on the edge spectrum preservation has a good ranging effect with a correlation coefficient of 0.986 and Root Mean Square Error (RMSE) of 11.39 mm. It is found that the range ability can be effectively improved after the image rotation processing of the duck egg image taken at an oblique angle, with the RMSE is reduced from 11.39 mm to 8.76 mm, the average relative error is reduced from 2.85% to 2.28% and the correlation coefficient reaches 0.99. The proposed algorithm fundamentally meets the requirements of stability and high accuracy in ranging targets with weak or non surface texture features.

A new method for measuring the flux distribution of a high-magnification convergent radiation spot is proposed. A radiation flux sensor is used to measure the flux density at different positions of the spot, and the calibration curve of the grayscale and flux density at different positions of the spot is fitted by a polynomial, and finally the flux distribution of the radiation spot is obtained and its principle is also elaborated. In order to verify the accuracy and feasibility of the measurement method, a high-magnification convergent radiation spot flux distribution measurement experiment is carried out, and the results are compared with the direct measurement results from the radiant flux sensor. The results show that the measurement results of the proposed method are consistent with the direct measurement results, and the average deviation is less than 0.54%. Through analysis, the measurement uncertainty of this measurement method is 4.35%, and the measurement accuracy is higher than the traditional measurement method. The experimental results indicate that the proposed method can meet the needs of practical applications.

Ammonia gas is an important basic industrial raw material, and realizing its non-contact detection is of great significance for the timely detection of ammonia gas leaks to avoid major safety incidents. Aiming at the shortcoming of conventional ammonia leak detection devices that can only respond when ammonia diffuses to a certain range and makes contact with a sensor, a Shuffling Self-Attention Network (SSANet) model is proposed to realize the infrared non-contact detection of ammonia leaks. Due to the high noise and low contrast of ammonia leakage images obtained by infrared cameras, an infrared detection dataset of ammonia leakage was established through non-local mean denoising and contrast-limited adaptive histogram equalization preprocessing. On the basis of YOLOv5s, the SSANet model uses the K-means algorithm to cluster and analyze the candidate frame suitable for the infrared detection of ammonia gas leakage to preset the model’s parameters. Using the lightweight ShuffleNetv2 network, the depth of 3×3 in the Shuffle Block can be adjusted. The separate convolution kernel is replaced with a 5×5 depth, and the feature extraction network is reconstructed with an SK5 Block containing a new convolution module, which makes the model size, calculation and parameters non-intensive while improving the detection accuracy. The Transformer module is used instead of its original version. The C3 module in the network bottleneck module is replaced by Transformer module to realize the bottom-up fusion of multi-head attention in the leake area, and further improves the detection accuracy. The experimental results show that the size and parameter requirements of the SSANet model are reduced by 76.40% and 78.30%, respectively, to 3.40 M and 1.53 M compared with the basic model of YOLOv5s; the average detection speed of a single image is increased by 1.10% to 3.20 ms; and the average detection accuracy is increased by 3.50% , reaching 96.30%. We provide an effective detection algorithm for the development of a non-contact detection device for ammonia leakage to ensure the safe production and stable operation of ammonia-related enterprises.

Aiming at the problem of sea-sky-line detection in low-contrast infrared images being difficult and easily affected by interference factors such as clouds, strip waves and sea clutter, we propose a method of using polarization difference images for sea-sky-line detection. Firstly, Polarization Difference Imaging (PDI) is used to enhance the local contrast of the sea surface area and the Signal-to-Noise Ratio (SNR) of the sea-sky-line. A large-scale local contrast accumulation method of the polarization difference images is then used to determine the sea-sky-line area. Finally, the accurate detection of a small-scale sea-sky-line is completed by combining the gradient significance and polynomial fitting in the sea-sky-line area. Overall, the methodology integrates multi-dimensional information such as the Degree of Linear Polarization (DOLP) and the Angle of Polarization (AOP) for sea-sky-line detection, and combines large-scale and small-scale detection, which can effectively overcome interference of factors such as clouds, strip waves and sea clutter. The experimental results show that the accuracy of this algorithm for sea-sky-line detection is 98.5%, and the average time consumed is 16 ms. The experimental results indicate that the proposed algorithm can realize fast and accurate sea-sky-line detection so it has wide applicability in different scenes.

Aiming at the urgent demand of high-precision optical alignment systems for a domestic infrared focal plane flip chip bonder, an optical alignment system was designed and verified, and the parallel adjustment, optical alignment and coordinate system error compensation algorithms applied to the system were researched. Firstly, this paper analysed the optical alignment process of a flip chip bonder, then introduced the parallelism adjustment and optical alignment algorithm, and proposed a more reasonable error compensation algorithm according to the test process of the optical alignment system. Finally, based on the above calculation algorithm, the optical alignment system was designed including three parts: a collimation system, a microscopic imaging system and a laser ranging system. The functions of parallel coarse adjustment, feature point recognition and parallel fine adjustment were realized. The experimental results show that the collimation system has a good collimation effect, the microscopic imaging system has high resolution and good imaging quality, and the ranging accuracy of the laser ranging system is 0.084 μm. The designed high-precision optical alignment system solves the urgent need of a domestic infrared focal plane flip chip bonder for high-precision optical alignment systems. It has been applied in a certain types of flip chip bonders, and has very important social significance for improving the independent research and development and production capacity of domestic high-end large-scale integrated circuits.

Airborne ambient temperature varies widely and airborne vibration can be strong. Because there is a difference in the thermal expansion coefficients of an Invar inlay and mirror material, a mirror’s higher coating temperature means that the traditional bonding process will lead to bonding failure and the surface precision of the mirror cannot meet system requirements. Therefore, this paper proposes a new method of bonding the mirror after processing and coating, and designs some important parameters for the adhesive layer. RTV is used as the main binder for the mirror and the inlay, and the effect of RTV curing on the structure is alleviated by favorable elasticity. The thickness of RTV is 1.1 mm, its width is 7.2 mm and the thickness of the epoxy adhesive is 0.022 mm. The simulation results show that the RMS of the mirror shape is 25.91 nm and the first-order frequency of the mirror group mode is 242 Hz when the gravity is 1 g and temperature change are -40 °C (the initial temperature is 20 °C). The final surface detection RMS is 15.8 nm and the resonance frequency is 213 Hz. The experimental results show that the design, structure and bonding layer can meet the wide temperature range and vibration requirements.

In a distance-selected imaging system based on single-photon detection, a short-pulse laser is emitted and synchronization control between the transmitter and receiver is performed, and the detector operates in photon counting mode and integrates in time to complete the imaging. In order to obtain a short pulse laser that meets the system requirements while reducing the system’s size and cost, we propose to apply two types of narrow pulse generation circuits based on RF bipolar transistor and Step Recovery Diode (SRD) to single photon distance selective imaging systems. We introduce the principle and design method of both types and verify the system through simulation, physical fabrication and testing. The characteristics of the pulse generator and factors affecting its pulse width and amplitude are analyzed. The physical test results show that the transistor-based method can generate a narrow pulse with a rise time of 903.5 ps, a fall time of 946.1 ps, a pulse width of 824 ps, and an amplitude of 2.46 V; the SRD-based method can generate a narrow pulse with a rise time of 456.8 ps, a fall time of 458.3 ps, a pulse width of 1.5 ns, and an amplitude of 2.38 V; and the repetition frequency of both can reach 50 MHz. Both design methods can be used with external current-driven laser diodes to achieve excellent short pulse laser output.

In this paper, a dynamic equation of a semiconductor laser with transverse effect is given by modifying the dynamic model, and the influence of the transverse effect on its output characteristics is analyzed. On this basis, the synchronization transmission technology of a semiconductor laser’s output signal with transverse effect is further studied. The results show that the output of the semiconductor laser presents a new spatiotemporal chaotic state after considering the transverse effect, and is very sensitive to the initial value. At the same time, whether the synchronization transmission of single-channel or multi-channel signals is carried out by a semiconductor laser, its transmission performance is very stable. The synchronization technology is very simple and easy to apply in practice.

We focuse on the effects of camera aperture, atmospheric turbulence intensity and satellite orbit height on the tracking and positioning accuracy of high-resolution remote sensing satellites. Firstly, we establish a turbulence model and turbulence simulation method based on Kolmogorov turbulence theory for observation of the Earth. Then, the influence of camera aperture, satellite orbit height and atmospheric coherence length on the positioning accuracy of the satellite is simulated and analyzed, and then a universal formula is deduced to calculate the tilt aberration of turbulence wavefront. Finally, based on this universal formula, a theoretical formula for calculating jitter is derived for Earth observation. This work can provide a theoretical basis of the influence of atmospheric turbulence for the design, analysis and evaluation of high-resolution remote sensing satellites.

In order to reduce influence of background infrared radiation, the temperature of the whole optical system should be below -20 °C for satellite-borne long-wave infrared imagers working in orbit. On the base of the weak heat conduction structure, a Ω type flexible sunshield made of MLI was developed and a cryogenic optical system was achieved through direct radiation cooling. Cage-like three-dimensional heat conduction straps made of copper were developed and an isothermal design for the body tube was realized. The cryogenic optical system applied to space remote sensing was used for the first time in China when it was tested in orbit with SJ-9B satellite. The results showed the temperature of the whole optical system could be maintained at -35 °C~-20 °C all the time, and the temperature difference in the body tube was no more than 4 °C. All flight test data met the temperature requirement of the long-wave infrared imager. This thermal control method is simple and effective, which can provide a reference for the thermal design of similar satellite-borne infrared optical systems.

The integrated detection of the main focus telescope is realized by sensing the curvature wavefront of the telescope. First of all, the curvature sensing process of the main focus telescope and the basic principle of dynamic stability transfer in multiple links are analyzed using Fourier optics theory. Secondly, the error analysis of static correction and dynamic surface shape measurement in the integrated detection of the main focus telescope is carried out. After that, the degree of freedom locking in the adjustment process is analyzed. Finally, the principle of the integrated detection process is realized through experiments. The obtained wavefront detection residual is better than 0.08λ( λ=633 nm). The spatial resolution is 10/m-1, and the temporal resolution is 0.2 Hz. This method can effectively improve the imaging quality of main focus telescope with the large-aperture large-field, and reduce the demand for the stability of the external environment in the integrated detection process by using the non-interference and high robustness characteristics of the curvature sensor, so as to provide assistance for the more detailed time-domain astronomical observation in the future.

In this paper, the effect of the cross-linking agent 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) on the optical properties of graphene quantum dots (GQDs) and the reasons are investigated in detail. GQDs were prepared by a hydrothermal method and reacted with EDC to obtain GQDs/EDC composites. The spectral properties of GQDs and GQDs/EDC were investigated. The effect of pH on the fluorescence of GQDs/EDC and its mechanism were investigated using PBS solution and artificial gastric juice samples. The experimental results show that EDC passives the surface defects of GQDs, making the fluorescence of GQDs increase rapidly in <1 min time and remain stable up to 20 min. Under different EDC contents the fluorescence intensity of GQDs/EDC is significantly enhanced by about 264 times compared to GQDs alone. The pH response experiments shows that GQDs/EDC had a linear response pattern of fluorescence and absorption intensity in the pH range of 1.75-4.01 and 4.01-9.28. Biocompatibility showed that the cell viability of human breast cancer cells was greater than 80% at sample concentrations of 25-300 µg/mL and remained at 74% even at high concentrations of 500 µg/mL; Finally, the detection of artificial gastric pH has high accuracy with relative standard deviation RSD ≤1.10%. The EDC-mediated fluorescence enhancement makes GQDs more advantageous in the fields of detection, sensing and imaging. Besides, the sensitive pH response characteristics of GQDs/EDC provide a good prospect for pH detection applications.

In this paper, a multifunctional metamaterial device based on the phase transition properties of vanadium dioxide (VO2) is proposed. The metamaterial structure consists of a top layer combined with VO2-filled Split Ring Resonator (SRR) and a metal cross, a polyimide (PI) dielectric layer, and a metal substrate. When the VO2 is in the insulating state, the cross-polarization conversion function can be realized, and its Polarization Conversion Rate (PCR) is greater than 90% in the range of 0.48-0.87 THz. When the VO2 is in the metallic state, the device can realize dual-frequency absorption and be applied in high-sensitivity sensing functions. The absorption rates are higher than 88% at the frequencies of 1.64 THz and 2.15 THz. By changing the refractive index of the sample material, the sensing sensitivities at the two related frequencies are about 25.6 GHz/RIU and 159 GHz/RIU, and the Q-factors are 71.34 and 23.12, respectively. The proposed metamaterial multifunctional device exhibits the advantages of a simple structure, a switchable function, and high-efficiency polarization conversion, and provides potential application value in future terahertz communication, imaging and other fields.

Vision-based measurement has good application prospects and far-reaching development significance for advanced manufacturing fields such as aerospace, the military industry and electronic chips. Among them, on-machine 3D vision detection technology based on structured light is one of the hotspots and challenges in the field of precision machining. Based on the on-machine 3D measurement process of structured light, we discuss and summarize the key technologies, including its technical requirements, methods and principles involved, related research status and existing problems in the measurement calibration, phase optimization solution, on-machine 3D point cloud processing and reconstruction of different feature surfaces. Finally, according to the actual needs of relevant technologies in the future, prospects are made with regard to processing field calibration, dynamic real-time 3D reconstruction, sub-micron and nano measurement, and measurement processing integrated data transmission technology, with the corresponding research ideas put forward.

To solve the problems of short illumination distance and narrow spectral range in the current underwater detection technology, an underwater semiconductor white laser imaging system was established. The quality of the images captured by the system under different light sources and different conditions was studied. A white laser with a power of 220 mW and a color temperature of 6469 K synthesized by an RGB semiconductor laser is used as the underwater lighting source, which is respectively compared with three RGB monochromatic lasers and an LED white light source under different conditions. For these images, different algorithms are used to process, analyze and evaluate their quality. The results indicate that when the white laser is used as the underwater light source, the collected image is not only better than that with the LED white light source with respect to information detail and structural integrity, but also better than the monochrome laser in color reproduction of the target and the integrity of the edge feature information. The semiconductor white laser has the advantages of concentrated energy, strong color rendering, and high illuminance, and its light source performance can meet the requirements of underwater low-illumination imaging. With the same imaging system and imaging distance, images with stronger authenticity, better texture and more target feature information can be obtained.

In this paper, we study the coherence of magnetic surface plasmons in one-dimensional metallic nano-slit arrays and propose a double-dip sensing method to improve sensitivity. Different from the conventional way of scanning wavelength at a fixed incident angle, coherence of surface plasmons is investigated by changing the incident angle at a fixed wavelength. Due to the retardation effect, two coherence dips move in opposite directions as the refractive index of the surrounding medium changes. Compared with one dip used for sensing, two oppositely moving dips can efficiently improve the sensitivity. The total sensitivity of two dips can reach 141.6°/RIU while the sensitivities of two single dips are 39.2°/RIU and 102.4°/RIU respectively. Besides, the inconsistency between the refractive index of slit medium and upper medium has few influences on the sensing performance, which will have wide practical applications.

The cavity surface optical film is one of the most crucial components of the fiber bragg grating External Cavity diode Laser (ECL). Although, the Plane Wave Method (PWM) is widely used in the optical film preparation, it is not an ideal design method when applied in ECL preparation. The Finite-Difference Time-Domain (FDTD) method is used to analyze this problem by taking the effect of facet dimensions and structure into account. According to the simulation, PWM suffers from poor reflectivity and deviation of the reflection curve, which significantly affects performance. Therefore, the optical film design is optimized and verified by experiments. Magnetron sputtering is used to fabricate the optical film, which is then applied to ECL. The measurement results show that the reflectivity of Anti-Reflection (AR) film is reduced by 30% after optimization, while the reflectivity of High-Reflection (HR) film increased to 96%. The prepared ECL’s fiber output power exceeds 650 mW. In this paper, the optical film suitable for ECL is designed and fabricated, and provides a reference for optical films in ECLs and other semiconductor optoelectronic devices.

The refractive index measurements based on traditional wave optical methods are mainly depended on intensity and wavelength detection strategies. Interference spectrometers are widely used as the most ideal wavelength detecting devices. Interference spectrometers measure the signal intensity, analyze the change of fringe numbers and the corresponding optical path difference by means of optical power meter, and then calculate the wavelength of signal light. Therefore, its essence is still based on intensity detection. However, the resolution of interference signal in intensity detection is restricted by classical diffraction limit, thus its resolution is difficult to further improve. In order to solve this bottleneck, parity detection which could break through the classical resolution limit and realize super-resolution refractive index measurement is proposed in this paper. According to the quantum detection and estimation theory, the expressions for signals and their corresponding sensitivities of refractive index measurement with parity and intensity detections were derived respectively and their numerical comparison analysis was carried out. In addition, the effects of loss on resolution and sensitivity of the output signal were investigated. Numerical results show that the resolution of parity detection is ${\text{2{\text{π}}}}\sqrt N$ times that of intensity detection, achieving super-resolution refractive index measurement. Moreover, the optimal sensitivity reaches the refractive index measurement shot noise limit ${\lambda \mathord{\left/ {\vphantom {\lambda {\left( {2{\text{π}} l\sqrt N } \right)}}} \right. } {\left( {2{\text{π}} l\sqrt N } \right)}}$. The loss reduces the sensitivity and resolution of the signal. The resolution of the parity detection signal is consistently better than that of intensity detection except for the very large loss and very low photon number. Finally, the physical essence of the super-resolution refractive index measurement is analyzed from the detection means itself.

In the tower solar thermal power plant, the heliostat mirror shape errors have an important impact on the optical efficiency of the heliostat field, so it is necessary to measure the heliostat surface shape error. The heliostat is generally made up of splicing multiple sub-mirrors, the tilt angle error of the sub-mirror is an important part of the heliostat mirror shape errors. This paper proposes a measurement method for the tilt angle errors of the heliostat sub-mirror based on the photogrammetry. That is, under the condition of known the shape size of the heliostat sub-mirror, the spatial position coordinates of the 4 corner points of the heliostat sub-mirror are calculated by using the principle of photographic imaging. Then the normal direction of the sub-mirror is found, and the tilt angle of the sub-mirror is calculated by using the normal line obtained. Finally, the measurement for the tilt angle error of the heliostat sub-mirror is achieved. In this paper, the measurement principle of the method is elaborated, the calculation formula is derived, and relevant verification experiments were carried out using planar mirrors and cameras. By measuring the plane mirror with different tilt angles at different distances, the deviation between the measured tilt angle and the actual tilt angle of the plane mirror is about 0.1°~0.3°, and the experimental results show that the method can accurately measure the tilt angle error of the sub-mirror of heliostat, thus the correctness and feasibility of the method are verified.

In order to effectively avoid high computational complexity when using Maximum Likelihood (ML) detection, a deep learning-based Spatial Pulse Position Modulation (SPPM) multi-classification detector is proposed by combining a Deep Neural Network (DNN) and step detection. In the detector, the DNN is used to establish a non-linear relationship between the received signal and the PPM symbols. Thereafter, the subsequent received PPM symbols are detected according to this relationship, so as to avoid the exhaustive search process of PPM symbol detection. The simulation results show that with the proposed detector, the SPPM system approximately achieves optimal bit error performance on the premise of greatly reducing detection complexity. Meanwhile, it overcomes the error platform effect caused by K-Means Clustering (KMC) step classification detection. When the PPM order is 64, the computational complexity of the proposal is about 95.45% and 33.54% lower than that of ML detectors and linear equalization DNN detectors, respectively.

Aming at the problems of long processing time and low accuracy of the traditional laser spot center positioning algorithm used in a vibrating environment. We proposed a laser spot center positioning method based on a genetic algorithm optimized BP neural network. A BP neural network was applied to predict the spot center position and a genetic algorithm was applied to optimize the neural network. Based on the BP neural network, the gray weighted centroid method, centroid method, Gaussian fitting method were used to obtain the spot center position, and the centroid method was used to obtain the radius of laser spot, on the above basis, we predicted the actual center position of the spot. Genetic algorithms were used to optimize the weights and thresholds of neural networks to improve prediction accuracy. An experimental platform is established to simulate the vibration environment by applying perturbations to the optical system and the data is collected to train neural network and verify the algorithm. The experimental results show that the number of calibration test iterations before and after optimization is 55 and 29, and the average errors are 0.81 pixels and 0.45 pixels, respectively. Under the optimization of the genetic algorithm, the iteration speed and prediction accuracy of the neural network algorithm is improved.

In order to improve the output performance of a high-power Thulium-Doped Fiber Laser (TDFL) and increase the optical-optical conversion efficiency of the system, a high-power TDFL with an all-fiber Main Oscillation Power Amplification (MOPA) structure was developed, which can operate in both Continuous Wave (CW) and Quasi-Continuous Wave (QCW) modes. First, a laser oscillator was built to study the output characteristics of the seed source laser. Then, a thulium-doped fiber amplifier was built and connected to the laser oscillator to study the output characteristics of the MOPA structured fiber laser. Finally, the pulse characteristics of the MOPA structured fiber laser were analyzed under the QCW modulation mode. The laser oscillator achieved a continuous and stable laser output with a central wavelength of 1940 nm, and the highest average output power was 18.56 W. The slope efficiency was 54.84%, and the spectrum was free of Raman components. Using this low-power continuous laser as the seed source through the homemade thulium-doped fiber amplifier, the average output power could reach 66.9 W, and the slope efficiency was 48.48%. When the system operated in the QCW mode, the frequency and duty cycle can be adjusted, and the peak power was calculated to be 80.3 W when the frequency was 75 Hz and the duty cycle was 10%. This research is of referential significance for the development of higher power MOPA lasers in the 2 μm band.

Airborne lidar is an important means to achieve long-range accurate atmospheric monitoring. Its laser wavelength is consistent with the absorption spectrum of most atmospheric pollutants and chemical substances, which makes it an important laser source for airborne lidar. However, it is difficult to design a temperature control system for airborne CO2 lasers to work in the -40 °C-55 °C temperature range under the controlled volume and weight conditions. In this paper, we propose a temperature closed-loop control method, in which the laser characteristic and environment temperature are used as input, and a thermo electric cooler and forced air cooling are combined. According to the structure and heat transfer characteristics of the laser, the thermo-electric cooler and the level of forced air cooling, the finite element model of temperature control method is established to optimize the temperature control performance of the laser. In a high temperature environment of 55 °C, the temperature of the laser is controlled at 40 °C after the temperature control system operates for 25 min. In a low temperature environment of -40 °C, the laser temperature is controlled at 25 °C after the temperature control system operates for 20 minutes, which meets the normal working requirements of the laser. According to the laser and the established temperature control method, the experimental research on the working ability of the laser in high and low temperature environment is carried out, the temperature data of the laser in the experimental process is collected, and the laser output power is measured under high and low temperature conditions. The experimental results show that the experimental measured temperature data is consistent with the finite element simulation results and the error between them is less than 10%. The laser using the proposed temperature control method can work steadily, and the output power of the laser is consistent with that of the laser at room temperature.

Measurement repeatability is the largest uncertainty component of a light pressure based measurement device, which directly affects the accuracy of the measurement results. In order to improve the accuracy of the measurement power in the process of high-power laser measurement, a high-power laser measuring device based on light pressure is built. Quality measurement repeatability and laser power measurement repeatability experiments were carried out, and the results of the two experiments were compared and analyzed. The experimental results show that the measurement repeatability of the light pressure measuring device gradually decreased with the increase of the measured mass and the measured laser power, indicating that the light pressure method has more advantages in measuring high-power lasers. In the laser power measurement repeatability experiment, the influence of eccentric loads and airflow disturbance is avoided, so the laser power measurement repeatability is better than the measurement repeatability calculated according to the equivalent mass. The research results have guiding significance for further improving the measurement accuracy of the light pressure method in the future.

The damage threshold of an interline transfer CCD irradiated by different wavelength nanosecond Raman lasers was studied and an experiment with 496 nm, 574 nm, 630 nm Raman and multispectral Raman laser-irradiated CCD was carried out. The damage threshold interval of dot damage, line damage and total damage were observed and collected by adjusting the energy of each focused Raman laser. By careful fitting, the damage threshold interval and the damage possibility curve of the CCD at different laser energy densities with each Raman laser were estimated. Results showed that the multispectral Raman laser including a residual pump laser is most effective for damaging the CCD than the monochrome Raman laser, and the 630nm Raman laser acts better than 574 nm and the 496 nm Raman laser. The microscopic images of the damaged CCD were reviewed, and the electronic characters of the damaged CCD were also tested to understand the damage and blindness mechanism of a Raman laser pulse-irradiated CCD.

In order to improve the suitability of the fiber hydrophone towing line array, a flexible fiber grating hydrophone array was proposed.The sound pressure sensitivity of three flexible fiber grating hydrophones was calculated according to the mechanical theoretical model, and the influence factors were compared and analyzed. 2-element flexible fiber hydrophone sample arrays with diameters of 10 mm,12 mm and 16 mm were developed through finite element simulation for frequency response analysis. The sensitivity was measured by a vibration liquid column experiment. The experimental results show that the response is flat within the frequency range of 200~800 Hz, and the average sound pressure sensitivities of the hydrophone arrays with different structural parameters are -138.90 dB, -134.71 dB, and -136.12 dB, respectively. The theory and simulation analysis are verified. By further optimizing the material and structure parameters and using weak reflection fiber grating, an integrated flexible hydrophone array with hundreds of elements can be constructed according to the design in this paper.

The large aperture sky survey telescope needs closed-loop error correction based on the feedback of its wavefront sensing system, so as to give it a better conform to its limit detection ability. In this paper, firstly, the basic theoretical expression of sub region curvature sensing is derived. Then, a joint simulation model is established. The process of sub region curvature sensing is simulated and analyzed by using a combination of optical design software and numerical calculation software. Finally, by setting up a desktop experiment, the cross-comparison of single- and multi-target curvature sensors is carried out to verify the correctness of the algorithm. Compared to the traditional active optical technology, the method proposed in this paper can improve the detection signal-to-noise ratio and sampling speed by expanding the available guide stars. For the standard wavefront, compared with the single guide star curvature sensor, the error is 0.02 operating wavelengths (RMS), and the error is less than 10%, which can effectively improve the correction ability of the active optical system.

To investigate the multiple scattering transmission characteristics of polarized light in ellipsoidal fine particles, a simulation and experiment verification system for black carbon aerosol particles was established. The polarization transmission characteristic after multiple scattering of the randomly oriented ellipsoidal fine particles are studied by combining the T-matrix with the Monte Carlo method. A half-real simulation testing environment was established to verify the simulation algorithm, and the ellipsoidal fine particles were prepared by extending ganoderma lucidum spores′ burning time. The size distribution and optical thickness of the ellipsoidal fine particles were measured by Malvern Spraytec and a light power meter, respectively. The simulation results can be proven by combining the experiment with the simulation. The results show that with an increase in the concentration of black carbon ellipsoidal fine particles, the Degree Of Polarization (DOP) of the horizontal, vertical, 45° linearly polarized and the right circularly polarized light all decrease, and the polarization preservation ability of three kinds of linear polarizations are basically consistent. The polarization preservation ability of the circularly polarized light gradually exceeds the linearly polarized light with an increase in concentration. The gap between the linear and circular polarizations becomes larger as it reaches its maximum value at 3.12 optical thickness. When the optical thickness is greater than 3.12, the DOP difference between the circularly and the linearly polarized lights tend to be stable. By calculation, the percent agreement between the simulation and the experiment is better than 70.84%. These results can expand the environmental applicable range of polarization detection and provide theoretical support for studying the polarization detection of atmospheric non-spherical particles.

With the continuous development of digital display technology, display methods have also changed. Pepper’s ghost images that adopt modern display methods require the light environment of the exhibition space not only to ensure the effect but also ensure better visual comfort. In order to explore the influence of the lighting environment on the display effect based on Pepper’s ghost images, a virtual imaging display space is set up to analyze the factors and trends affecting the imaging effect, in which 12 sets of LED lighting conditions with different illuminances and color temperatures are generated. 25 observers are selected to conduct a psychophysical experiment. The experiment shows that color temperature has no significant effect on the evaluation of color authenticity, detail expressiveness and stereoscopic expressiveness for Pepper’s ghost images; illumination has no strong effect on the evaluation of the color authenticity of Pepper’s ghost images, but has a significant effect on their detail expressiveness and stereoscopic expressiveness. Under the lighting environment where the color temperature is 3500 K and the illumination is 10 lx, the detailed expressiveness and stereoscopic expressiveness of the display effect are relatively high and the visual comfort of 2500 K and 10 lx is better.

In order to generate double doughnut-shaped focal spots at adjustable positions along the axial direction, a vortex phase zone plate based on a formula of annular radius derived from vector diffraction integral was designed. The focusing properties of the modulated vortex phase zone plate were further investigated in a tightly focused system. First, integral formulas of linearly and circularly polarized vortex beams were calculated under high NA focusing conditions. Then, the intensity distributions of linearly and circularly polarized vortex beams in a high NA focusing system were simulated by integral formulas with various axial shifting distances and topological charges. Finally, the corresponding experimental results of linearly and circularly polarized light were also given, utilizing a spatial light modulator loaded on double doughnut-shaped phase patterns. The double doughnut-shaped focal spots with a topological charge of 1 and axial distances of ±10 μm and ±15 μm were produced when the incident light was linearly polarized. As well as the double doughnut-shaped focal spots with axial distances of ±20 μm, topological charges of 1-4 were also produced when the incident light was circularly polarized. The simulated and experimental results demonstrated that two doughnut-shape focal spots with controllable axial shifting distances and dark spot sizes could be produced in the tight focusing region of a high NA objective when it is modulated by the vortex phase zone plate. This kind of vortex phase zone plate could be applied in the field of optical micromanipulation, two-beam super-resolution nanolithography, and Stimulated-Emission-Depletion (STED) fluorescence microscopy.

Infrared polarization imaging technology has the advantages of long detection range and high rate of target recognition. However, the polarization characteristics of targets are easily affected by background radiation in complex environments, which significantly reduces the detection capability of infrared polarization equipment. Based on the polarized Bidirectional Reflectance Distribution Function (pBRDF), this paper establishes a calculation model for the target’s Degree of Linear Polarization (DoLP), comprehensively considering the radiation coupling effect between the target and the background. The variation of the target’s DoLP under two conditions - with and without a strong radiation backplate – is then comparatively studied. Additionally, in order to solve problems of land-based and airborne small-angle detection, simulation research is done to find out how the target’s DoLP is influenced by parameters such as the temperatures and the included angle between the target and the backplate. Research results show that the radiation coupling effect significantly reduces the target’s degree of polarization when the temperatures of the target and the backplate are the same, but it does not change the trend of the target’s degree of polarization, which increases with an increase in temperature. When the temperature of the target and the backplate is 30 °C, 40 °C, and 50 °C, the maximum degree of polarization of the target is 63.7%, 44.9%, and 42.2% of those without a strong radiation backplate, respectively. It can be concluded then that the higher the temperature, the stronger the radiation coupling effect between the target and the backplate, and the greater the reduction of the target’s degree of polarization; and that the strength of the radiation coupling effect is not only related to the temperature, but also to the included angle between the target and the backplate. With the increase of the included angle, the target’s DoLP first increases and then decreases, and the maximum value is obtained when the included angle is about 105°. Therefore, the radiation coupling effect changes the target’s DoLP to a certain extent, thereby affecting the detection ability of the infrared polarization equipment. Finally, through building a long-wave infrared polarization imaging system, the established calculation model of the target’s degree of polarization is verified by experiments, whose results are basically consistent with those of the simulation analysis. Overall, the research results in this paper have certain guiding significance for improving the detection and identification capabilities of land-based and airborne infrared polarization equipment.

In order to improve the autonomous detection ability of the airborne optronics pod of a UAV under special working conditions, this paper developed a targeting technology suitable for the airborne optronics pod in an actual engineering project, and realized the functional verification on the embedded GPU (Graphics Processing Unit, Jetson-TX2i platform model). Firstly, we proposed an improved SURF (Speeded Up Robust Features) algorithm and GPU-accelerated digital image processing scheme to detect and match the real-time features of two images acquired at different focal lengths. Secondly, geometric cross-ratio invariance was used to correct the position information of distorted feature points at image edges. Finally, we used the least square method to estimate the depth information of the target and combines the quaternion space model to determine the attitude information of the target to determine its position. Experimental results show that the improved SURF algorithm is superior to the classical SURF algorithm in feature matching accuracy and speed. If the corner characteristic position error is controlled within one pixel, the depth error is no more than 2% and the angle errors of azimuth, pitch and roll angles are less than 4°, 5° and 2°, respectively. This error meets the target positioning accuracy requirements of the airborne optronics pod. In addition, when processing a set of images (two frames) at 1080 P resolution, the processing time can be increased to 74 ms through GPU acceleration, which meets the real-time demand for data processing in the airborne optronics pod.

At present, the simulation research of arc actuators is limited to only obtaining the working characteristics of the plasma generated by the actuator, such as potential, pressure, temperature and velocity, while the plasma state is limited to only diagnosing its electron temperature and electron density by spectrum. The two are separated. This paper attempts to unify the two. Therefore, the arc jet plasma actuator designed here adopts the finite element method to solve the nonlinear multi physical equations. The working characteristics of the arc jet plasma actuator are numerically simulated, and the potential, pressure, temperature and velocity distributions inside the actuator are obtained. On this basis, the electron density is calculated and the simulation calculation model of the plasma state (electron temperature and electron density) of the actuator is obtained from the working condition of the actuator. Then the spectral diagnosis of the jet plasma is carried out by using the emission spectral diagnosis method, and the electron density of plasma is calculated by using the intensity ratio method of discrete spectral lines. The diagnostic experiment of the arc plasma actuator shows that the maximum electron temperature is 10505.8 K and the maximum electron density is 5.75×1022 m-3. For the plasma electron temperature and plasma density under different working conditions, the experimental and simulation results increase with the increase of inlet gas flow and discharge current. It shows that our simulation model of plasma state is reasonable and applicable for our miniaturized arc jet actuator with high jet velocity.

The diffraction effect of microlens array will affect the detection accuracy of Shack-Hartmann wavefront sensor. Based on Huygens-Fresnel diffraction theory, a two-dimensional microlens array diffraction model is established to simulate and analyze the two-dimensional diffraction spot array generated in the focal plane when the ideal parallel light is incident on the microlens array. First, the maximum centroid calculation error is determined by calculating the centroid error in the process of diffraction spot shifting by one pixel. Then the wavefront is reconstructed by using the modal method to obtain the wavefront detection error. The simulation results show that the maximum wavefront error caused by diffraction is 0.125 λ at 0.21 and 0.79 pixels offset, that is, when the wavefront deflection is 0.03° and 0.13°. Finally, an experiment is performed to verify the effectiveness of the error calculation method. This work provides a theoretical basis for the design of shack-Hartmann wavefront detector.

In order to achieve tunable multiple Fano resonance characteristics and design a refractive index sensor with high sensitivity, a nanoring-heptamer metal-dielectric composite nanoantenna structure is proposed, and the influencing factors and variation rules of its Fano resonance characteristics are studied by using the Finite Element Method (FEM). Researches show that Fano resonance characteristics of the hybrid nano-antenna is sensitive to the changes of the height, incident angle and internal gap. In addition, the electric intensity and the Purcell factor (PF) under the excitation of the electric dipole source can reach 134.74 V/m and 3214 respectively, which greatly enhances the electric intensity near the center of the nanoantenna. The hybrid nanoantenna has high Sensitivity (S) (1400 nm/RIU) and Figure of Merit (FOM) (17 RIU-1), respectively, which can be used as two significant performance indices for evaluating the refractive index sensor with high sensitivity. This paper provides a feasible way to realize the tunability of Fano resonance in the composite nanoantenna and a solid theoretical basis for practical applications such as surface-enhanced Raman scattering, quantum emitters, and refractive index sensors.

In order to detect polarized ultraviolet light by visible optical elements, CsPbBr3 nanocrystal/metal wire-grid composited films were prepared. The stability of its fluorescence was improved by depositing Al2O3 passivation layer. The green fluorescence of polarization-sensitive perovskite nanocrystals film was obtained under ultraviolet exciting light. The results show that the crystal structure of the CsPbBr3 nanocrystals obtained by hot-injection method have a cubic crystal system structure with a square shape and an average size of about 39 nm. An obvious green fluorescence at about 530 nm were observed under ultraviolet light excitation of the nanocrystal colloidal solution. The fluorescence intensity of the CsPbBr3 nanocrystal/metal wire-grid composited film obtained by self-assembly changed periodically with the polarization direction of the excited light. The luminous polarization ratio is about 0.54. The fluorescence intensity of this composite film was enhanced when Al2O3 was deposited on its surface by atomic layer deposition technology. The polarization ratio of the passivated film can still reach 0.36. The above results show that the fluorescence stability and polarization of perovskite nanocrystals film can be optimized by the surface passivation and the introduction of metal wire-grids, respectively. The obtained ultraviolet polarization sensitive CsPbBr3 nanocrystals composited film exhibits important application value in the fields of ultraviolet polarization detection and liquid crystal display.

We investigate a family of Cosh-Pearcey-Gaussian Vortex (CPeGV) beams, obtain the general propagation expressions of a CPeGV beam, and study the longitudinal and transverse Poynting vector and Angular Momentum Density (AMD) when the CPeGV beams propagate in uniaxial crystals. The effects of the cosh modulation parameter, topological charge, and propagation distance on the propagation properties of CPeGV beams are discussed. A larger cosh modulation parameter can lead the energy transfer significantly along the transverse Poynting vector direction. Moreover, we also investigate how the cosh modulation parameter and topological charge influence the propagation properties in the far-field. A larger cosh modulation parameter can lead AMD to present four-lobe structures rather than their usual parabolic curve. Our investigation will provide a better understanding of the state of the CPeGV beams propagating in uniaxial crystals and be useful for applications in information transmission.

In the process of dynamic 3D measurement based on phase-shifting and fringe projection, the ideal correspondence between object points, image points and phases in different fringe images is destroyed. On this condition, the application of traditional phase formulas will cause significant measurement errors. In order to reduce the dynamic 3D measurement error, the basic principle of the error is firstly analyzed, and the errors are equivalent to the phase-shifting errors between different fringe images. Then, a dynamic 3D measurement error compensation method is proposed, and this method combines the advanced iterative algorithm based on least squares and the improved Fourier assisted phase-shifting method to realize the high-precision calculation of random step-size phase-shifting and phase. The actual measurement results of a precision ground aluminum plate show that the dynamic 3D measurement error compensation technology can reduce the mean square errors of dynamic 3D measurement by more than one order of magnitude, and the dynamic 3D measurement accuracy after compensation can be better than 0.15mm.

A novel Photonic Quasi-crystal Fiber (PQF) sensor based on Surface Plasmon Resonance (SPR) is designed for simultaneous detection of methane and hydrogen. In the sensor, Pd-WO3 and cryptophane E doped polysiloxane films deposited on silver films are the hydrogen and methane sensing materials, respectively. The PQF-SPR sensor is analyzed numerically by the full-vector finite element method and excellent sensing performance is demonstrated. The maximum and average hydrogen sensitivities are 0.8 nm/% and 0.65 nm/% in the concentration range of 0% to 3.5% and the maximum and average methane sensitivities are 10 nm/% and 8.81 nm/% in the same concentration range. The sensor has the capability of detecting multiple gases and has large potential in device miniaturization and remote monitoring.

In order to solve the challenges of low space utilization and small aperture size for the sub-eye in bionic compound eye systems, a design method for a large aperture compound eye system with a hexagonal band arrangement is proposed in this paper. Using the filling factor theory, taking the traditional curved surface circular arrangement as the control group, it is demonstrated that the hexagonal band arrangement model can effectively improve the space utilization of a large-aperture compound eye system. Aiming at the limited target information acquisition of a single-band compound eye system, an infrared dual-band common optical path imaging form was designed, supplemented by a two-color image sensor, which enhanced the multi-dimensional ability of the compound eye system to obtain information. At the same time, a mathematical model of the sub-aperture positioning of the hexagonal band arrangement is established. The bionic compound eye system is composed of 91 sub-apertures with an entrance pupil diameter of 16 mm, a focal length of 48 mm and a field of view of 9°. The combined total field of view of the sub-apertures is 96°×85°. The focal length of the relay system is 6.14 mm. In a temperature range of -40 °C~+60 °C, the sub-aperture and the relay systems basically have no influence from thermal differences. The cold reflection effect of the detector can be ignored. The simulation results show that the Root Mean Square (RMS) radius of each sub-channel is smaller than the airy spot and the optical distortion value of each sub-channel is less than 0.1%. The Modulation Transfer Function (MTF) of the edge sub-channel in the MWIR/LWIR band is above 0.5 at 17 lp/mm. The system has a compact structure and strong detection ability, and can be used for multi-target detection and recognition in complex environments.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a recently developed laser spectral gas detection technology. Compared with common oxygen sensors such as electrochemical devices and ionic conductive ceramics, TDLAS has the advantages of high selectivity and sensitivity, fast response, on-line measurement and strong anti-background spectral interference ability. Oxygen (O2) is an important gas in habitable environments and is greatly significant to industrial production and human life, and the detection of O2 concentration is also widely used in these fields. Based on this, we adopt TDLAS technology to carry out high sensitivity measurements of O2 in air. Using a semiconductor laser with an output wavelength of 760 nm as the light source, the oxygen concentration in the environment is 20.56% by direct absorption spectroscopy, and the minimum detection limit is 5.53×10-3. In the wavelength modulation spectroscopy method, the laser wavelength modulation depth is optimized to obtain a complete second harmonic waveform, which can be used to calibrate the oxygen concentration. The SNR of the system is 380.74, and the minimum detection limit is about 540×10-6. The system realized in this paper has good oxygen detection ability and can be widely used in various fields of oxygen concentration detection.

In order to implement a solar direct pumping slab high power laser, a linear uniform high-power density pump source is studied. In this paper, we propose a design method of a high-power density uniform linear light source by combining the first-order concentrating system with seven confocal ellipsoids to form a composite ellipsoid cavity. The equal radiation flux segmentation of the circular first focal spot is realized by each ellipsoid. The mirror imaging characteristics do not significantly decrease the peak power density. After decomposition, the mirror spot forms a uniform linear light source at the second point of focus. The mathematical model of equal radiation flux is given by coordinate transform, and the rotation and translation parameters of each ellipsoid are solved by the annealing algorithm. The first-order system is composed of a Fresnel lens with a radius of 30 mm, a focal length of 70 mm and a single ellipsoidal cavity with a of 3.4 mm, cof 3.15 mm, The second-order composite ellipsoidal cavity concentrating system is attached. The line source is realized with effective length of 12 mm, the peak power density of 1.09 × 106 W/m2, and the uniformity of 95.46 %. Compared with the contribution of each ellipsoid parameter to the uniformity, the uniformity effect is significantly improved when the rotation parameter θ of the middle ellipsoid is 1.4°. The change of the edge ellipsoid parameter Δ has a significant influence on the effective length of the linear light source, and its optimal value is 0.53 mm.

An optical switch based on a scanning mirror was designed in this paper. The optical switch is programmable and controlled by an embedded Linux system that switches between the fiber array channels on the UI of the touch display. Meanwhile, the switching sequence and residence time of the optical switch can be preset. In addition, the optical switch can be self-calibrated to obtain the maximum output power of each channel. The principle of the optical switch is analyzed and the performance of the optical switch is tested experimentally. The experimental results show that the average insertion loss is less than 17 dB for the single mode fiber array, the average crosstalk between adjacent channels is more than 30 dB, and the switching time between the adjacent channel is less than 1.3 ms. The average insertion loss is less than 2.4 dB for the multi-mode fiber array. It has the advantages of low loss, low delay, high precision, good stability, high repeatability,low cross-talk between the adjacent channel, and good man-machine interaction for the application of theWavelength Division Multiplexing (WDM) and multi-channel optical waveguide sensors test device.

We propose a design method of a free-form reflector for collimating illumination of integrating spherical light sources to reduce the space occupation on a satellite. By using this method, a square irradiance distribution with large area can be achieved through a integrating sphere with small diameter. Firstly, the mathematical model of off-axis reflection lighting of free-form surface is established through the point light source model, then the free-form surface is discretized by Chebyshev points, and the free-form surface model that satisfies the point light source illumination is solved. Finally, the light source characteristics of the integrating sphere are analyzed. The transformation from the point light source illumination model to the integrating sphere illumination model is achieved by the optimization of the free-form surface energy distribution. The analysis results show that when the illumination area is set as 140 mm×140 mm, the irradiance non-uniformity of the target surface is less than 0.02. This method can meet the requirements of spaceborne calibration for light weight, short light path and simple structure.

In order to realize the efficient and automatic measurement of complex curved surface parts, we propose a viewpoint planning method of surface structured light scanning based on an improved grid method, and apply it to the automatic measurement of automobile parts with complex curved surface. Firstly, aiming at the problem of serious redundancy and poor scanning integrity of the manual teaching viewpoint, a scanning viewpoint planning algorithm for surface structured light based on an improved grid method is proposed. According to the effective measurement range of a surface structured light scanner, the grid size is determined, and the candidate viewpoint generation strategy is improved. The effective measurement range of candidate viewpoints is obtained by the measurement constraint condition of the scanner, and the optimal viewpoint is determined by the viewpoint quality evaluation function. Secondly, in view of the low efficiency of the algorithm and the low accuracy of feature reconstruction in the process of viewpoint planning, the voxel grid method is used to simplify the model. The complex surface model is segmented by the octree algorithm, and the voxel grid size is determined according to the normal vector consistency error. For the models with different geometric characteristics, the influence of the weight coefficient on the scanning quality is analyzed, and the optimal weight coefficient is given. Finally, the scanning viewpoint planning and measurement experiments of automobile sheet metal parts and reducer shell are carried out. The results show that the viewpoint planning of the automobile sheet metal parts takes 21.93 s, the scanning integrity is 99.124%, and the scanning accuracy is 0.025 mm. The viewpoint planning of automobile reducer shell takes 158.29 s, its scanning integrity is 93.231%, and its scanning accuracy is 0.032 mm. This method can quickly complete the viewpoint planning of complex curved surfaces, and the model obtained by planning viewpoint scanning has good integrity and high precision, which can meet the requirements of complex curved surface parts for automatic measurement.

In order to promote the application of Laser-Induced Breakdown Spectroscopy (LIBS) in the nuclear industry, in this paper, a femtosecond LIBS(fs-LIBS) system was used to quantitatively analyze Thorium (Th) in a highly pure graphite matrix. According to the Th concentrations in the Thorium-based fuel, a total of 9 homemade Th2O3-graphite mixture samples with Th concentrations that varied from 0.35% to 35.15% were prepared by the standard addition method. The favorable experimental parameters such as the treatment methods for LIBS detection, laser pulse energy and delay times were studied before the quantitative analysis. The results show that the signal intensity of the fs-LIBS spectrum acquired by the scanning with moving method is significantly higher than that without the moving method. For the Th I 396.21 nm line, the Relative Standard Deviation (RSD) value of multiple measurements for the scanning method was just 5.7%, which was much lower than that of without the moving method (20.4%). The Th spectral lines show obvious saturation due to the self-absorption effect in the higher concentration region, and thus the basic calibration method was no longer applicable. Therefore, an exponential function was used to fit the spectral line intensity and concentration in the whole concentration region, and the concentration saturation threshold values corresponding to the analytical lines Th I 394.42, 396.21, and 766.53 nm were obtained. The basic calibration method has good detection performance when the calibration curves were constructed by using a lower concentration below the saturation threshold. For the peak area and peak intensity of each analytical line, using the internal standard method with the internal standard line (C I 247.85 nm), a good linear relationship can be found between them and the Th concentrations in the whole concentration region, especially for analytical line Th I 766.53 nm with a higher saturation threshold. The internal standard method had good prediction performance for unknown samples with higher concentrations. The above results show that fs-LIBS has the potential to monitor and analyze the thorium concentration in the thorium-based fuel cycle.

To achieve non-contact daily mental stress detection, this paper proposes a image photoplethysmography to detect mental stress. First, a video of the subject's face is recorded by the cell phone camera. Then, the proposed Dynamic Region of Interest (ROI) extraction method based on Face Mesh is used to obtain the weak skin color changes caused by heart rate fluctuations. Next, the Fast Independent Component Analysis (FastICA) algorithm, wavelet transform and narrowband bandpass filtering are combined to extract the signal and heart rate variability information based on image photoplethysmography. Then, stress-induced experiments are conducted on 30 subjects to screen 14 features for mental stress detection by comparing the differences in heart rate variability parameters between normal and stressful states, and to explore the relationship between short-term mental stress and daily mental stress due to stress induction. Finally, an additional 67 subjects are tested for daily mental stress, and a triple classifier for mental stress detection is built using the machine learning algorithm. The experimental results show that the accuracy of the three classifications of mental stress can reach 95.2%. Given that this method does not require long-term measurements and can accurately detect human mental stress levels using only a smartphone, and that the measurement method is simple, and easy to administer, and does not affect the normal psychological and mental state of the subject, it can be used as a valid tool in psychological research.

Aiming at the problems of complex and inaccurate classification of benign and malignant brain tumors, a classification model was proposed based on the fusion of multi-scale and channel features. The model used ResNeXt as the backbone network. First, the multi-scale feature extraction module based on dilated convolution was used to replace the first convolution layer, which can make full use of dilation rates to obtain the image information from different receptive fields, and combine the global features with significant subtle ones. Second, the channel attention mechanism module was added in the network to fuse the feature channel information in order to increase the attention to the tumor, and reduce the attention to redundant information. Finally, the combination optimization strategy, the MultiStepLR strategy of the learning rate, the label smoothing strategy and the transfer learning strategy on medical images were adopted to improve the learning and generalization abilities of the model. The experiments were carried out on BraTS2017 Dataset and BraTS2019 Dataset, and the classification accuracy were 98.11% and 98.72%, respectively. Compared with other advanced methods and classical models, the proposed classification model can effectively reduce the complexity of the classification process and improve the detection accuracy of benign and malignant brain tumors.

Fluorescence emission difference microscopy is a super-resolution imaging technique with strong universality of fluorescent dyes and low phototoxicity. However, due to the limitation of its principle, traditional fluorescence emission difference microscopy has a high system complexity, low stability and limited imaging speed. In order to improve these defects, we design and build a set of multi-color virtual fluorescence difference microscopy system, and it’s imaging method and parameter are analyzed. On the basis of the existing principle of multi-color virtual fluorescence emission difference microscopy, the influence of the signal-to-noise ratio and background is further considered, and a virtual fluorescence emission difference microscopy imaging model that can be verified experimentally is established. The experiments show that the system and method have the characteristics of simple structure, strong background denoising ability, strong universality of fluorescent dyes, and low phototoxicity. Its imaging resolution is 1.9 times higher than that of confocal system, and its imaging speed is doubled compared to the traditional fluorescence emission difference microscopy system. It has obtained good imaging results at three wavelengths, and has been experimentally verified in biological cell imaging.

In this paper, we propose a non-diffraction Light Sheet Fluorescence Microscopy (LSFM) technique, which readily enables multi-scale 3D fluorescence imaging of diverse biological samples with size ranging from microns to centimeters. To solve the problem of heavy sidelobes in conventional non-diffraction Bessel LSFM, we invent a double-ring-modulated approach which can generate non-diffraction light sheets with ~0.4 to ~5 µm tunable thickness and the ratio of the sidelobe was reduced to less than 30%. Then we built a multi-scale LSFM system based on this novel approach. The system showed versatile multi-scale imaging abilities, such as dual-color 3D dynamic imaging of single live cell, 3D super-resolution imaging of expansion cells and high-throughput 3D mapping of entire meso-scale organs. Therefore, we demonstrate that this multi-scale imaging modality can substantially improve the efficiency of LSFM for advancing various biomedical studies, such as cell biology, tissue pathology, and neuroscience.

Terahertz (THz) technology becomes increasingly important nowadays, especially in testing and security applications. Extending the field of view and increasing the imaging quality are both vital challenges for THz imaging. To address these problems, we build a THz light field imaging system based on a single-camera scanning configuration, which utilizes the 4D information of the spatial and angular distribution of THz waves. Based on the 4D plenoptic function and the parameterization method with two parallel planes, the intensity consistency of THz propagation is used for refocusing calculation, then a series of refocused images can be obtained by integrating original light field images corresponding to different imaging distances and views. Compared with the original THz imaging, the field of view and the imaging quality of the THz light field imaging are effectively improved. In our experiment, the field of view was enlarged by a factor of 1.84 and the resolution increased from 1.3 mm to 0.7 mm. Furthermore, information on some obscured targets could also be retrieved by defocusing the obstructions. This method could improve the imaging quality of THz imaging as well as expand its functions, which inspires a new way for THz nondestructive testing (NDT) and security inspection.

The fields of modern biology and biomedicine urgently need wide-field-of-view (FOV), high-resolution microscopic technology and instruments for trans-scale observation of biological samples to meet the requirement of major scientific for research. Limited by the spatial bandwidth product, traditional commercial microscopes cannot meet this demand. Besides, the existing high spatial bandwidth product microscopy systems have problems such as bulky volume and high implementation costs. In this paper, based on the HiLo optical sectioning technology and the self-designed wide-field-of-view and high-resolution objective, a wide-field-of-view and high-resolution HiLo optical sectioning microscopy system was developed. The FOV and imaging resolution of this system were tested. Brightfield imaging experiments were carried out on mouse brain slices by this system and the results were compared with that of OLYMPUS commercial microscope. At the same time, wide-field fluorescence imaging comparison experiments were carried out on wheat seed fluorescent slices. The experiment results show that the FOV of this system reaches 4.8 mm×3.6 mm (the diagonal FOV is 6.0 mm), the lateral resolution reaches 0.74 μm, and the axial resolution reaches 4.16 μm. The comparative experiment proved that this system has the advantages of wide FOV, high resolution and the ability of fast optical sectioning imaging simultaneously. This system can carry out rapid 3D imaging of large-volume biological samples, which will provide strong technical support for researches such as embryonic development, brain imaging, and digital pathology diagnosis.

In order to realize the in-situ detection of large aperture plane mirrors, wavefront detection is achieved by a combination of the Ritchey-Common method and holographic detection through the differential transfer function, combined with the actual Ritchey-Common detection architecture, and through the occlusion code of the pupil. Firstly, the principle of large aperture plane mirror detection based on differential transfer function method is derived, and the existing large aperture wavefront is compared with the reconstructed wavefront. Finally, the detection light path is built by using deformable mirrors. The correlation between the surface shape obtained by this method and the input surface shape is not less than 70%. This paper is of great significance to the fundamental cosmological propositions such as the detection of the "first light" of the universe and the "one black, two dark and three origins".

The modulation Transfer Function (MTF) is an important evaluation index for remote sensing cameras, but at present, the research on the dynamic MTF characteristics of digital domain TDI CMOS cameras is very limited. In order to deeply research its image quality degradation mechanism, combined with the principle of digital domain Time Delay Integration Complementary Metal Oxide Semiconductor (TDI CMOS) imaging, a mathematical model of digital domain TDI imaging MTF degradation caused by pixel, electronic shutters, exposure time and vibration is established. Combined with the derived model, the prediction analysis and experimental verification are carried out. The results show that the regional distribution of effective pixels of the sensor will affect the image MTF with a greater intluence from smaller opening rates, and the rolling shutter of the CMOS sensor will lead to the decrease of the digital domain TDI imaging MTF with a more serious impact for slower rolling shutter speeds. When the rolling shutter speed changes from 6 μs to 10 μs, the corresponding image MTF decreases from 0.191 to 0.177. As the exposure time shortens, the MTF grows higher, especially when there is low-frequency image shift mismatch. When the exposure time is reduced from 180 μs to 100 μs, the MTF increases from 0.126 to 0.155 with some influence on the image signal-to-noise ratio. Therefore, the exposure time should be reasonably controlled in practical applications.

In order to satisfy the urgent needs of on-line real-time monitoring and analysis instrument for industrial pollution emission and sudden safety accidents, a panoramic bispectral infrared imaging interference spectrum measurement inversion instrument is proposed. Through the collaborative design of dual channel interference system, dual spectral imaging system, azimuth and elevation axis system, the measurement of image spectrum information of target scene with large field of view, wide spectral band and high resolution is realized. First, based on Fourier optics theory, the scalar diffraction theoretical model of interference imaging spectrum is established. Then based on broadband sampling and narrowband sampling theory, the sampling design of dual channel interference system is carried out. Based on the analysis of the interference imaging characteristics, the optical design of the dual band imaging system is carried out. Finally, the principle prototype is completed, and the telemetry experiment of the gas plume emitted by the chimney is carried out. The instrument can realize spectral measurement with resolution of 4 cm-1 in large field of view by 360°×60° and wide spectral range from 3~5 μm to 8~12 μm. The instrument can satisfy the application requirements of qualitative identification and quantitative analysis for gas emission monitoring.

The rectangular primary mirror with aperture of 1.8 m×0.5 m is the crucial component of an off-axis Three Mirror Anastigmat (TMA) space optical system. In order to guaranty the structural stability and reliability of the Primary Mirror Assembly (PMA) and the surface figure error (RMS value) of the mirror, a bi-axial flexural support has been proposed for the large-size rectangular mirror. First, based on the principle of kinematic equivalent, the initial structure of the bi-axial flexural support was designed and the analytical formula for stiffness and its characteristic was studied as well. Then the mounting position and the key dimensions of the flexural supports were studied and optimized. Finally, the final optimization design scheme of the PMA was determined. Experimental results indicate that the surface figure error (RMS value) of the PMA under 1 G gravity in X and Y directions are 4.81 nm and 6.09 nm respectively when the optical axis is placed horizontally, which are less than λ/50 (λ=632.8 nm). The first-order natural frequency is 104 Hz, which can satisfy the design requirements. The dynamic tests have shown that the dynamic characteristics of the mirror assembly are good, and the flexural support system is stable and reliable. Now the mirror has been polished to have a surface figure better than λ/30 RMS. Zero Gravity optical testing has been performed under ±1 G respectively, which shows good coincidence with the analytical results.

The semi-active support is based on the semi-active optical technology, and the correction force is converted into a correction torque through a Warping Harness(WH) spring blade to correct the mirror low-order aberration introduced by error sources such as gravity and temperature. Aiming at the defects of traditional empirical design of mirrors, a new optimal design method for a mirror support system is proposed, that is, a comprehensive design optimization method of mirror support system based on structural size optimization combined with empirical design, and a set of semi-active mirror support systems based on WH is established. Firstly, the initial structure of the support system is designed according to the empirical formula; an L-shaped hollow WH spring blade is designed, and the nonlinear analysis and fatigue analysis are carried out to determine that the blade thickness is 2 mm and the service life is 1.2×106 times. Then, the RMS value of the mirror surface in the vertical and horizontal states of the optical axis was reduced from 119 nm and 106 nm to 13.3 nm and 4.8 nm by optimizing the position of the mirror support point, the position of the triangular plate flexure joint, and the key dimension parameters of the support system’s flexible parts; under the state of 1 °C temperature difference, the specular aberration is reduced from 2.8 nm to 1.9 nm; the first-order resonance frequency is increased from 80 Hz to 130 Hz. Finally, this method is used to verify the correction ability of the semi-active support system. The results show that the correction rate of the semi-active support system for mirror defocus, primary astigmatism, primary coma and primary spherical aberration can reach up to 99%. The amplitude of each aberration is less than 1 nm; the correction rate of the RMS value of the mirror’s surface shape can reach up to 46.5% under it′s own weight state at room temperature, and the correction rate is 31.28%.

Aiming at the problems of large parameters and low semantic segmentation accuracy of real-time semantic segmentation networks for true-color microvascular decompression (MVD) images. This paper proposes a U-shaped lightweight fast semantic segmentation network U-MVDNet (U-Shaped Microvascular Decompression Network) for MVD scenarios, which consists of encoder-decoder structure. A Light Asymmetric Bottleneck Module (LABM) is designed in the encoder to encode context features. Feature Fusion Module (FFM) is introduced in the decoder to effectively combine high-level semantic features and underlying spatial details. Experimental results show that for the MVD test set, U-MVDNet achieves 0.66 M parameters, 76.29% mIoU (mean Intersection-over-Union), and 140 frame/s speed on NVIDIA GTX 2080Ti. And when input image size is 640 × 480, the real-time (24 frame/s) semantic segmentation is realized on NVIDIA Jetson AGX Xavier embedded development board. The proposed network has no pretrained model, fewer parameters, and fast inference speed. The semantic segmentation performance is superior to other comparison methods, and a good trade-off between segmentation accuracy and speed is achieved. Furthermore, U-MVDNet can also be easily developed and applied on embedded platform with superior performance and easy deployment.

In this paper, the basic principle and reconstruction method of random filter spectral coding-decoding are discussed. According to the automatic feature extraction mechanism of a deep learning undercomplete autoencoder, a pixel mapping variable-resolution spectral imaging reconstruction network with high reconstruction accuracy and low delay is constructed. The parallel training of a 2×2 and 4×4 pixel array spectral reconstruction network is implemented by transforming the pixel mapping relationship. Finally, the network’s performance is verified by the remote sensing data with 512×616 with 120 bands spectral images. For a 2×2 pixel array with 40 bands, the reconstruction PSNR is 53 dB, the reconstruction MSE is less than 0.002, and the reconstruction time is 0.85 s. For a 4×4 pixel array with 120 bands, the reconstruction PSNR is 64 dB, the reconstruction MSE is less than 10-5, and the reconstruction time is 0.5 s. The experimental results show that the pixel mapping variable-resolution spectral imaging reconstruction network has the dynamic transformation performance of high accuracy and low delay.

In order to realize single mode, narrow linewidth and low magnetism field intensity operation of lasers, Vertical-Cavity Surface-Emitting Lasers (VCSEL) with integrated micro-lens extended cavity was designed and fabricated. First, an epitaxial structure suitable for the micro-lens integration was designed and grown by Metal Organic Chemical Vapor Deposition (MOCVD). The fabrication steps of the micro-lens integrated VCSEL was carried out and the magnetism-free material was used in the electrode deposition. Experimental results indicate that the operating temperature is 90 °C, the laser wavelength is 896.3 nm, the laser power is 1.52 mW, the side mode suppression ratio is as high as 36.3 dB and the operating magnetic field intensity is less than 0.03 nT. A narrow line width and magnetism-free VCSEL suitable for quantum sensing was demonstrated.

Based on the requirement of multichannel detection for hyperspectral resolution imaging spectrometer, we design a hyperspectral resolution ultraviolet dual channel common optical path imaging spectrometer whose telescopic system adopts an off-axis three mirror structure with an off-axis field of view, and whose spectroscopic system applies a modified small and light weight Offner structure. Through the theoretical analysis of Offner spectrometer structures, initial structural parameters of a dual channel common optical path Offner that met the requirements of hyperspectral resolution were achieved. In order to improve the imaging quality of the imaging spectrometer, meniscus lenses were introduced into Offner structure, and the system was gradually optimized. Eventually, a dual channel common optical path imaging spectrometer was obtained with operating bands of 280~300 nm and 370~400 nm. When the Nyquist frequency is 27.8 lp/mm, the modulation transfer function (MTF) of both channels is better than 0.8, the full field mean square root radius (RMS) is less than 9 μm. and the spectral resolution is better than 0.1 nm. The design of this imaging spectrometer has important implications for the miniaturization and integration design of space-based hyperspectral detection imaging spectrometers.

In order to realize the target of light and small, low radiation and large field of view of the long-wave infrared catadioptric optical system for deep-space low-temperature target detection, the local cooling optical system, topology optimization, metal-based mirror design, additive manufacturing, Single Point Diamond Turning (SPDT) for metal mirrors and surface modification are studied. First of all, a compact catadioptric optical system with partially cooled is designed, in which the aperture is 55 millimeters, the focal length is 110 millimeters and the field of view is 4 degrees by 4 degrees. Secondly, the primary mirror assembly, the secondary mirror assembly and the connecting baffle are designed using the topology optimization theory, and the third order mode and fourth order mode reach 1213.7 Hz. Then, the front group optical mirrors assembly are developed by means of additive manufacturing, SPDT, surface modification and surface gold plating. We complete the optical mechanical assembly using the centering assembly method. Finally, the performance of the system after optical mechanical centering is tested. The test results show that the Modulation Transfer Function (MTF) curves of the optical system reach the diffraction limit in the whole field of views, and the weight is only 96.04 grams. Additive manufacturing method can be used as an effective means to improve the performance of optical systems.

In order to realize the stable and safe output of lasers, a control system based on a 515-nm high-power laser is designed. Firstly, the pump drive module of the system is studied. The analog sampling of the module is completed by Field Programmable Gate Array (FPGA) and the calculation output is completed in Digital Signal Processing (DSP). The closed-loop control of the constant current source is completed by using the digital Proportion-Integral-Derivative (PID) algorithm. Secondly, a Thermo Electric Cooler (TEC) is used to achieve the stable temperature control of the frequency doubling crystal module, and the Negative Temperature Coefficient (NTC) is used as the feedback to realize the temperature control. Finally, the human-computer interaction system of the laser is designed, which realizes the real-time monitoring, judgment and storage of the internal state of the laser. In order to verify the effectiveness of the control system, a pump is selected for testing. The experimental results show that the pump drive module can work continuously and stably, and the control system can monitor the internal state of the laser in real time, which is safe and reliable. The laser output center wavelength after frequency doubling is 514.98 nm, the power can reach 170 W, and the optical power stability is ±0.07 dB. All devices and equipment for the control system are made in China, meeting the system design requirements of 515-nm high-power laser.

In order to meet the application requirements of airborne laser differential absorption lidar for small and lightweight light sources, a compact pulsed CO2 laser is developed with automatic wavelength tuning. First, the aperture matching relationship between an RF waveguide intracavity beam and a free space optical chopper beam was studied, and a beam conversion system was designed with real focus on the intracavity. The influence of the chopper aperture on a laser pulse waveform was verified experimentally. Secondly, the wavelength tuning characteristics of CO2 laser were studied, and the diffraction angle difference between adjacent laser spectral lines was analyzed. Tunable operation in the CO2 laser was realized using a high-precision electric turntable and metal blazed grating. Finally, the integration of a compact automatic tuning pulsed CO2 laser was completed using small lightweight modules. Experimental results indicate that the laser operates stably at 1 kHz with a pulse width of 350 ns and a peak power of 3.7 kW. There are 30 lines within 9.2~10.7 μm waveband. The total weight of the laser is 18 kg. It provides a miniaturized detection light source for airborne laser differential absorption lidar.

As the requirements of space astronomy, situational awareness, environmental monitoring and other fields grow higher, space telescopes are developing toward large fields of view and large apertures. Large-scale focal plane stitching technology is the key technology of large-field space telescopes. The allocation method of the main focal plane flatness error (P-V value) is generally a direct assignment method based on experience, which is prone to unreasonable error allocation.In this paper, a method of splicing focal plane error allocation is proposed, which can accurately allocate important parameter errors through optical-structural-thermal integration analysis. Taking 4×4 mechanical direct splicing focal plane with 16 pieces of Complementary Metal Oxide Semiconductor(CMOS) image sensor as an example, an error tree of splicing focal planes is established. The influence of important parameters such as gravity and temperature on the flatness of splicing focal plane is analyzed by the method of optical-structural-thermal integration analysis. The error distribution result is finally given. The analysis shows that the flatness errors caused by gravity under two different attitudes are 0.28 μm and 1.55 μm respectively, and the total flatness error caused by temperature is 5.5 μm. After leaving a 30% margin, the assigned values of the flatness error caused by gravity and temperature are determined to be 2 μm and 7.2 μm, respectively.

In order to control the group velocity of slow light, a graphene plasmon time crystal slow light waveguide was constructed and used for the waveguide to construct the Zigzag topology interface channel for transmission. When the structure is fixed, the external bias voltage of the graphene nano-disk can be dynamically adjusted to obtain the dispersion curves at different times. The corresponding group velocity is studied. First, the graphene plasmon time crystal is obtained by applying the bias voltages periodically varying with time to different regions of the honeycomb arranged graphene nano-disks. When the time translation symmetry of the crystal is destroyed, the crystal band gap will periodically appear and disappear with time, and exhibit the band topology effect. The Zigzag topology interface is constructed to analyze the topological interface state and its slow light mode existing at different moments. Then the corresponding group velocity is calculated according to the dispersion curve. Finally, a slow light waveguide model is established through numerical simulation, and the field enhancement process is detected at the light energy capture point of the waveguide. Simulation results show that the waveguide designed based on the graphene plasmon time crystal can achieve a good slow light transmission effect, and the group velocity of the light can be dynamically adjusted when the waveguide structure is fixed. Under slow light transmission, the light energy capture point realizes the field enhancement effect. The slow light waveguide with simple structure can be dynamically tuned, and has broad application prospects in slow light modulation devices and optical storage devices.

Stimulated Brillouin scattering in As2S3 photonic crystal fibers was investigated at wavelengths of 2 μm to 6 μm by the finite element method. The numerical results indicate that the proposed photonic crystal fiber can maintain single-mode operation when the air filling factor is less than 0.6. The Brillouin frequency shift is mainly influenced by the pump wavelength and fiber structure. The Brillouin frequency shift decreases by 4.16 GHz when the pump wavelength is increased from 2 μm to 6 μm, while the Brillouin frequency shift changes by the order of megahertz when the rate of air filling increases from 0.5 to 0.6. The FWHM of the Brillouin gain spectrum depends on the phonon lifetime, and the FWHM of the Brillouin gain spectrum is nine times wider at a pump wavelength of 2 μm than that at a pump wavelength of 6 μm. The maximum Brillouin gain of the proposed fibers with air filling fractions of 0.5 and 0.6 are 2.413×10-10 m/W and 2.429×10-10 m/W, respectively. The Brillouin threshold is positively correlated with the pump wavelength for the same effective fiber length, and is 27.8% and 19.6% larger at a pump wavelength of 6 μm than that at 2 μm with air fill factors of 0.5 and 0.6, respectively. The numerical results are of great significance for the design and fabrication of optical devices or optical sensors based on the proposed fibers in the mid-infrared band.

Spectral irradiance degradation of a halogen tungsten lamp increases the spectral radiance uncertainty of an on-board lamp-diffuser calibrator that is composed of a lamp and a diffuser reflector. Therefore, it is necessary to investigate the degradation characteristics of the lamp to decrease the spectral radiance uncertainty. A spectral irradiance degradation model of a halogen tungsten lamp with an undetermined order at wavelengths from 400 nm to 1300 nm was proposed according to the blackbody radiation law and Weierstrass theorem. Then, the spectral irradiance degradation curve of the halogen tungsten lamp was experimentally measured, and it was fitted by different order models using the least squares method, respectively. The model order was determined as 2, which is the minimum order to satisfy the reconstruction accuracy required by the spectral radiance of the on-board lamp-diffuser calibrator. The reconstruction accuracy of the spectral irradiance degradation curve was better than 0.25% according to this two-order model, which lays a theoretical foundation to decrease the spectral radiance uncertainty of the on-board lamp-diffuser calibrator.

The mapping relationship between the mode shapes of a plastic landmine’s upper casing and its laser speckle interference signal was studied. The mode shape function of a landmine’s upper casing is established according to the vibration equation of its thin circular plate. Then, based on the principle of laser shearing speckle interference and the time-average method of a CCD camera, we mapped the out-of-plane displacement of the mode shape to the phase of the interference laser. The study shows that the different mode shapes of the landmine correspond to the unique Bessel fringes. Furthermore, the Bessel fringes of two modes are simulated, and the corresponding experiments were carried out. Both the numerical and experimental results confirm the theoretical conclusions, the research in this paper can provide theoretical evidence for realizing the rapid scanning technology of acoustic-optics landmine detection.

In this paper, the drive control circuit using C8051F120 and CPLD single chip microcomputer is optimized and designed based on the performance test of brushless DC motor. By using the minimum torque ripple control method of PWM_ON, both the speed and position closed-loop control of brushless DC motor are realized. The experimental results show that the designed control system has the characteristics of fast response and high station accuracy. The speed fluctuation is less than 7% at low speed of 1°/s, and the accuracy of large angle position step is less than 1 code. The proposed method has realized wide speed range and high precision control of brushless motor and the effectiveness of the drive and algorithm is verified.

Considering that the aperture of a monoblock telescope is limited in size, to build an aperture telescope that is greater than ten meters, the technology of segmented mirrors should be used. Therefore, the co-phasing detection technology of segmented mirrors has become the key technology in the segmented process and in maintaining the mirror quality. To solve the problem that the broadband method demands a long time consuming and the narrowband method has a small range in the most widely accepted broadband and narrowband shack Hartmann method, a new method is proposed combining the incoherent and coherent diffraction patterns of broadband light (400-700 nm) to realize coarse co-phasing of 250 nm precision and fine co-phasing of 10 nm precision. When a segmented mirror is coarse co-phasing, the incoherent diffraction pattern of two hale circular holes is used as a template and white light is used as the light source. The cross-correlation algorithm is used to calculate the value of cross-correlation coefficient, and then it can achieve the unlimited range and a detection precision of 0.25 μm by setting a reasonable threshold value for the cross-correlation coefficient. When segmented mirror is fine co-phasing, a disk pattern of white light instead of multiple coherent diffraction patterns with different piston errors is used as a template to achieve a range of 0.27 μm and a detection precision of 0.01 μm. The theoretical and simulation results show that the detection range is the range of actuator and the measurement accuracy is less than 10 nm. Both the theoretical analysis and simulation show that this method is suitable for the detection of a coarse and fine co-phasing of segmented mirror.

For high-precision refractive index measurements of amorphous fluids, the minimum deviation angle method was used to design a novel thermostatic hollow trigonal prism device. The optical path and thermostatic compenents of the device are precisely designed. The device can be used not only to measure the refractive index of liquids, but also to quantify the measurement results and uncertainties. Firstly, the precise design and machining of the optical plane helps to precisely control the measurement light. Secondly, the tortuous hollow tube inside the thermostatic jacket is designed, which allows temperature fluctuations and uniformity of the liquid to be sufficient for high-precision refractive index measurements. Finally, the device is applied to measure a liquid’s refractive index, and the measurement uncertainty of each influence factor is quantitatively analyzed. The experimental results show that the refractive index measurement of three liquids, namely water, isooctane and tetrachloroethylene, could achieve an accuracy of 10-7 at 10-5 of uncertainty. Thus, the device provides a method for highly-precise measurements of the refractive index of liquids.

In order to meet the requirements of long and highly precise heat flux measurement under laboratory conditions, a new radiative heat flux meter was developed based on the principle of electrical substitution measurement. The radiative heat flux meter can be traced to the International System of Units through self-calibration. Firstly, the system structure of the radiative heat flux meter is briefly described. Combining with the measuring principle of the radiative heat-flux meter, the measurement uncertainty of nine uncertainty components and their combined standard uncertainty in the process of radiative heat-flux meter self-calibration are analyzed and calculated. Then, the uncertainty of a radiometric heat-flux meter is verified by direct comparison with a standard detector calibrated by the National Institute of Metrology of China. Finally, according to the experimental data and analysis results, this paper provides a reference for the optimization design of the heat-flux meter. The experimental results show that the relative standard uncertainty of the radiative heat-flux meter is better than 0.26%, and the normalized error is 0.60, which verifies the validity of the uncertainty evaluation results. The experimental results will guide the development of radiative heat flow meters in the next stage and further improve its performance.

At present, the mobile camera has the ability to obtain imaging information in the space (x-y direction) and depth (z direction) dimensions while the acquisition of spectral information has been stuck in RGB tricolor. Limited by the size of the mobile platform, the traditional imaging spectrometer is difficult to be embedded. Based on the integrated manufacturing technology of multi-channel array filters, micro-lens array imaging and integration, this paper completes the overall design of the system, the design and manufacture of the key components and overall assembly. The spectral imaging is verified experimentally. The overall physical size of the system is less than Φ6 × 6 mm, the spectral resolution is 8nm, and the spectral range is 0.53-0.68μm. The experimental results show that the spectral curves of any part of the object can be obtained by imaging the object with different colors, which verifies the design index of the snapshot spectrometer. With the basic conditions of embedding the technology into mobile phones, the system is expected to promote the integrated applications of imaging spectrometers.

In space gravitational wave detection, the telescope is an important part of the space laser interferometry system. The wavefront error at the exit pupil of the telescope is coupled with the Tilt-To-Length (TTL) noise, which becomes the main source of noise in space gravitational wave detection. Firstly, based on the interference model between a flat-top beam and a Gaussian beam, the Fringe Zernike polynomial is used to characterize the wavefront error at the exit pupil of the telescope, and the LISA Pathfinder (LPF) signal is used to analyze the coupling mechanism of the wavefront error at the exit pupil and the TTL noise. Secondly, the Monte Carlo analysis method is used to study the influence of the proportion of low-order aberrations on the TTL coupling noise under different numerical wavefront errors, and determine the low-order aberration proportions which meets the requirements of TTL coupling noise control at the exit pupil in the design of the telescope optical system under different numerical wavefront errors. Finally, based on the above theoretical analysis results and the aberration control requirements, the optical design of the space gravitational wave detection telescope is completed. The diameter of the entrance pupil of the telescope is 200 mm, and the RMS value of the wavefront error at the exit pupil is 0.01908λ. The proportion of low-order aberrations is not higher than 50%. The analysis results show that the TTL coupling noise does not exceed 8.25 pm/μrad when the beam jitter is within ±300 μrad. Through tolerance analysis, the maximum TTL coupling noise is determined to be 15.50 pm/μrad, which meets the requirements of space gravitational wave detection.

To ensure the imaging quality of the off-axis three-mirror space telescope during the ground adjustment and on-orbit adjustment stages, we reveal the coupling characteristics of the effect of the axial misalignment and the lateral misalignment on aberration based on the Nodal aberration theory from the internal mechanism level. This paper focuses on the compensation relationship generated by the coupling characteristics of two types of misalignments: (1) axial misalignment compensates for lateral misalignment, which reveals a type of working condition where the system image quality may be at a local extreme during the alignment process on the ground; (2) lateral misalignment compensates for axial misalignment. A compensation strategy wherein astigmatisms and comas introduced by in orbit lateral misalignment can compensate for astigmatisms and comas induced by axial misalignment is proposed (defocus cannot be corrected). Taking the off-axis three-mirror system in the laboratory as an example, the accuracy of the analytical relationships can be verified. Simulations and experiments have proven that the imaging quality of the system may reach the diffraction limit (1/14λ), but the system’s image quality is at a local minimum in the presence of both axial and lateral misalignment. When the telescope is misaligned in orbit and the defocus is small, the system image quality can be corrected by properly aligning the lateral misalignment first. The RMS wavefront error after compensation changes less than 0.02λ compared with the design state (the best state of installation and alignment).

As an important parameter of high-precision optical films, thickness uniformity plays a vital role in their performance. Large-size high-precision reflective films have especially high requirements for thickness uniformity. In this paper, the efficiency and accuracy of the uniformity correction of thin films are greatly improved by studying the emission characteristics and film thickness distribution of the evaporation source, combining Mathcad software to establish precise mathematical and physical models, writing automatic programs, and simulating the correcting mask shape. Through this method, an aspherical deep ultraviolet reflector with a diameter of 320 mm is prepared on public autobiographical planetary evaporation deposition equipment. The average reflectance at 240-300 nm ultraviolet waveband is greater than 97.5%, and the uniformity is better than 0.5%. This research provides a theoretical basis and technical support for the uniformity correction of large aperture aspheric films.

The rapid detection and identification of organic macromolecules can be realized by using the unique fringerprint spectrum of the terahertz band, but the measurement of terahertz absorption spectrum of trace analyte is still challenging. We proposed a detection scheme of enhancement of terahertz absorption spectrum for trace organic analyte based on angle multiplexing of the dielectric metasurface. The substrate and the cross-unit structure of metasurface are both high-resistance silicon which has high-Q resonances. The resonance frequency of the metasurface under terahertz incident with different angles can cover 0.50-0.57 THz. When a lactose film with the thickness of 0.5-2.5 μm as analyte is placed on the metasurface, the amplitude of the resonance peak corresponding to each incident angle changes greatly with the absorption spectrum of the analyte. The enhanced absorption spectrum built by the resonance frequencies envelope is 82.59 times larger than that without the cross-unit structure. The simulation results show that the metasurface has great potential to enhance the terahertz absorption spectrum through angle multiplexing, and it can be used to detect trace organic substances with different characteristic peaks after optimized design.

Oxide Vertical Cavity Surface-Emitting Lasers (VCSELs) are widely used in data communication. However, VCSELs are sensitive to ElectroStatic Discharge (ESD), which is one of the main reasons for their failure. It is difficult to identify the root cause of this problem. Therefore, 3 different ESD models including Human Body Model (HBM), Machine Model (MM) and Charge Device Model (CDM) and Electrical OverStress (EOS) shocks were applied to carry out the failure analysis of oxide VCSELs. Among them, voltage shocks of different polarities were used for HBM while reverse I-V, forward L-I-V scan, emission microscopy (EMMI) and Transmission Electron Microscopy (TEM) were used for characterization. The results show that different ESD models show significantly different damage voltage thresholds, and the oxide VCSEL is susceptible to damage in the HBM and MM models but insensitive in the CDM model. Defect characteristics associated with ESD failure were found including increased reverse leakage, degradation of optical output power, and bright spots in the EMMI. TEM was the most direct and effective method where different ESD events showed different defect sizes and locations. These research results are of great significance to confirm whether the failure mode is caused by ESD and to judge the specific ESD models in detail.

This paper aims to meet the new requirements of modern analytical and testing technology development, and to promote the application of Laser-Induced Breakdown Spectroscopy (LIBS) in the field of element analysis, especially for the measurement of rare earth element in soil. A LIBS system combined with calibration curve method was used to quantitatively analyze samarium (Sm) in the soil of Bayan Obo rare earth mining region. Firstly, the samples containing 1%, 5%, 10% and 20% Sm2O3 were prepared by Standard Addition Method (SAM) with the soil of national standard material GBW07402a as the base. Secondly, through analyzing the substrate excited by different laser pulse energy parameters, the influence of laser pulse energy parameters on the spectral line intensity and Signal to Back Ratio (SBR) was researched, an optimum laser pulse energy parameter was finally selected for the next measurement. Thirdly, in order to get and study the linearity of the calibration curve constructed between the peak area and the Sm concentration, the original spectra data were processed with multiple peak Lorentz fitting method without background subtraction (MFM) and Concatenation-based Integration Method (CIM) with background retention, respectively. Finally, according to the calibration curve, the concentration prediction was carried out, and the detection performance of LIBS for Sm in soil samples of rare earth mining area was preliminarily evaluated. The results show that the matrix effect of the soil can significantly broaden the emission lines of Sm element, which makes it impossible to distinguish them from each other. However, the effect of the soil matrix on sodium (Na), potassium (K), Titanium (Ti) and iron (Fe) is much weaker than that on Sm. By comparing the spectral region of interest, the 410 nm-band and 470.44 nm emission lines were identified and selected as the analysis lines, and subsequently used for quantitatively analysis. Results show that calibration curves for Sm element constructed by the peak area and concentration have good linear correlations and most of the linear relationships of the regression coefficients (R2) for the Sm emission lines are better than 0.99. Compared with the results by using MFM, CIM could obtain better linear correlation, and the maximum of was 0.99927 for the 410 nm-band. The better analytical predictive skill of LIBS measurement by using the leave-one-out method with CIM data was found as well, the relative errors of the prediction for both the analysis lines were all within 1% for the 3# sample with the Sm concentration of 4.310%. The achievements of this study demonstrate that the LIBS spectral analysis is capable of monitoring special elements in the rare earth mineral sample, which meets new requirements of modern analysis technology, and provides an experimental basis for the development of portable rare earth element detector as well.

Micro-Electro-Mechanical Systems (MEMS) have the characteristics of miniaturization and high integration. As the high aspect ratio of MEMS increases, the measurement of MEMS feature size faces greater challenges. Through-focus Scanning Optical Microscopy (TSOM) technology is a high-precision and nondestructive optical measurement method. TSOM images are captured along the scanning direction by collecting a set of defocused images and the size information of the structure is extracted from TSOM images by the library matching method. This method is highly sensitive and suitable for nano-scale structure measurements, but it is difficult to build a database for micron-scale features and is susceptible to environmental interference. In this paper, a TSOM optical system is established and traditional optical microscopy is used to collect a set of defocused images. The TSOM’s feature vector set is obtained by the image feature extraction method and is combined with machine learning to establish MEMS groove regression prediction models with different feature sizes. The results show that the above method can achieve nano-scale high precision measurement of a MEMS groove width and the single point repeatability measurement has great performance. The Relative Standard Deviation (RSD) of 2 μm width is about 1%, and the RSD of 10 μm and 30 μm width are respectively lower than 0.2% and 0.35%. This method has very high application prospects for micron MEMS groove structure measurement.

Active optical imaging detection is an important method for seabed topography and environment detection, which is widely used in ocean exploration. However, due to the attenuation effect of light in seawater, the optical images often suffer uneven illumination, color distortion and low contrast. According to the property of underwater active optical imaging, an underwater image enhancement method based on relative radiometric correction is proposed in this paper. The procedure is divided into brightness compensation and color restoration. In brightness compensation, according to the imaging characteristics and radiation attenuation mechanism of a point light source, the relative radiation correction is used to compensate for the channels of underwater images. This stage eliminates the brightness distortion caused by an uneven light source, varying optical paths and so on. In the color restoration, adaptive compensation and rough color balance are performed first on the red channel. Then, the Retinex model is used to restore colors. The real seabed images are used for experiments. The results show that the enhanced images by the proposed method have uniform brightness and natural look. Compared with the other methods, the results of the proposed method are better overall both subjectively and objectively. At the same time, the method proposed in this paper does not need the properties of light source, camera and others. Only the real detection images themselves are used for correction, and achieve better adaptability.

In order to effectively integrate the spectral saliency information of infrared and visible light images and improve the visual contrast of the fused images, a fusion method of infrared and visible light images based on weighted visual saliency and maximum gradient singular value is proposed in this paper. Firstly, the new algorithm uses the rolling guidance shearlet transform as a multi-scale analysis tool to obtain the approximate layer components and multi-directional detail layer components of the image. Secondly, for the approximate layer components that reflect the energy characteristics of the image subject, visual saliency weighted fusion is used as its fusion rule. This method uses the saliency weighted coefficient matrix to guide the effective fusion of spectral saliency information in the image, and improves the visual observation of the fused image. In addition, the principle of maximum gradient singular value is used to guide the fusion of detail layer components. This method can restore the gradient features hidden in the two source images to the fused image to a great extent, so that the fused image has clearer edge details. In order to verify the effectiveness of this algorithm, we have adopted five groups of independent fusion experiments. The final experimental results show that this algorithm has higher contrast and richer edge details. Compared with the existing typical methods, the objective parameters such as AVG, IE, QE, SF, SD and SCD are improved by 16.4%, 3.9%, 11.8%, 17.1%, 21.4% and 10.1%, respectively, so it has better visual effect.

To understand the effects of femtosecond lasers on the optical performance of the photodetectors, the damage characteristics of a CsPbBr3 back-to-back Schottky photodetector irradiated by femtosecond pulses and its photoelectric performance under various laser energy densities were evaluated. A CsPbBr3 microcrystal film on the ITO interdigital electrode was deposited by chemical vapor deposition and a back-to-back Schottky type all-inorganic perovskite photodetector was prepared. The CsPbBr3 photodetector was irradiated by a Ti:Sapphire femtosecond laser with a pulse width of 35 fs. The damage morphology of the CsPbBr3 polycrystalline film under different laser energy densities was observed using a microscope, and the photoelectric performance of the Schottky-structure perovskite photodetector damaged under different energy densities was evaluated. Results suggest that the damage threshold of the self-made all-inorganic metal halide Schottky photodectector is as high as 2.1 W/cm2, and when the sample is slightly damaged, the photoelectric characteristics of the sample are improved to a certain extent and the spectral responsivity is broadened by 50 nm. As part of the film is heated off, the sample still maintains a certain level of detection performance.

In order to make sure a microwave photonic filter both have wide tuning range and high frequency selectivity, a microwave photonic filter with a wide tuning range and narrow filter bandwidth based on a Brillouin oscillator is proposed and verified for the first time. The core of the filter is a Brillouin fiber oscillator with a cavity length of 10 m, and the stimulated Brillouin scattering pump and optical carrier signal are provided by two different tunable lasers. After the Brillouin gain spectrum interacts with the optical modulation sideband, the Brillouin fiber oscillator is used to narrow the spectral linewidth to realize narrowband microwave photonic filtering. By changing the pump wavelength, the filter passband can be tuned stably. The experimental results show that the microwave photonic filter can be stably tuned in the frequency range of 0-20 GHz. The out-of-band rejection ratio is found to be about 20 dB, and its 3-dB bandwidth and maximumQ value are 6.2 kHz and 3.222×106, respectively.To the best of our knowledge, this is the highest value of a high-Q single-passband MPF reported to date. At the same time, the MPF has the advantages of wide tunability, high side mode suppression and a simple structure.

A wide-band and narrow-band switchable bi-functional metamaterial absorber is presented in this paper. The phase change material vanadium dioxide (VO2) is introduced in the structure of the metamaterial absorber, and different functions can be achieved by using only a single switchable metasurface. The mutual conversion of different functions is realized by the reversible phase transition between the VO2 insulating state and the metal state. When VO2 is in metallic state, the designed structure can be regarded as a metamaterial wide-band absorber. The simulation results show that the absorption is over 98% in the frequency range of 1.55 THz to 2.21 THz. When VO2 is in the insulating state, the structure acts as a narrow-band absorber, and the absorption at resonance frequencies of 2.54, 2.93 and 3.34 THz is over 95%. In addition, the effect of geometric parameters on the absorption of metamaterial absorber is discussed. Because of the symmetry of the element structure, the absorber is insensitive to the polarization when the electromagnetic wave is vertically incident, and it can keep good absorption performance with the large incident angle. Therefore, the switchable bi-functional metamaterial absorber proposed in this paper can be widely used in terahertz modulation, thermal emitters and electromagnetic energy acquisition, etc.

With the advantages such as simple structure, simple process and easy interface control, the photoelectric devices based on carbon nanomaterial/bulk semiconductor van der Waals (vdW) heterojunctions can fully realize the ultrahigh carrier mobility of carbon nanomaterials and the excellent photoelectric properties of bulk semiconductors. Especially, the novel mixed-dimensional vdW heterojunctions can be prepared by controlling the diameter/chirality and Fermi level of single-walled carbon nanotubes (SWCNTs) to form atomic-level interfaces and match bandgaps with bulk semiconductors. Here, we reported a self-powered broadband photodetector based on the pn vdW heterojunctions by combining (6, 5)-enriched semiconducting SWCNT film with n-type GaAs, and used graphene to reduce the probability of carrier recombination in SWCNT film and to promote the carrier transport. The experimental results suggest that the self-powered device exhibits high-sensitivity photoelectric response toward the incident photons in the 405~1064 nm range, and that the max photoelectric responsivity of 1.214 A/W and the specific detectivity of 2 × 1012 Jones could be achieved at zero bias.

In this paper, an averaged intensity and spectral shift of Partially Coherent Chirped Optical Coherence Vortex Lattices (PCCOCVLs) in biological tissue turbulence are investigated with emphasis on optical lattice structures in monochromatic optical fields and spectral rapid transitions in polychromatic optical fields. It is found that the beam profile evolves from annular structures with a vortex core into a periodic array of lobes with a dark zone, and finally presents a Gaussian-like pattern in biological tissue. Although lattice parameter modulates beam profile, it cannot affect the spectral behavior in biological tissue turbulence. The analysis of spectral shift also shows that a smaller distance is beneficial to spectral rapid transition where the transverse coordinate decreases with an increase in chirp parameter and a decrease in pulse duration. The accumulated turbulences over a longer distance can suppress not only spectral transition but also spectral shift. The reduction of spectral shift is accompanied by stronger biological tissue turbulence. The results have possible application in image recognition, medical devices and noninvasive optical diagnoses in biological tissue.

When a micro-milling tool has a clamping angle on its spindle, the wear of the tool edge will accelerate and shorten the tool’s lifespan. In order to accurately observe the inclination state of the micro-milling tool on the machine, a three-dimensional pose reconstruction method based on the depth of field of a micro-milling tool is proposed. The laser coaxial digital holographic experimental device is used to obtain the micro-milling tool hologram, and the reconstruction image is obtained through the Fresnel reconstruction algorithm. The tool edge points are extracted as the key points in the reconstruction image, the wavelet transform local variance operator is used to obtain the degree of focus of the key points, and then the axial position corresponding to the milling tool is determined. The least square method is used to fit the key points and correct the reconstruction error, from which the three-dimensional pose reconstruction of the micro-milling tool is realized. The experimental results show that the reconstruction error of the micro-milling tool obtained by the three-dimensional pose reconstruction method is better than 0.1°. This method can accurately measure a three-dimensional pose of a micro-milling tool, which can provide a reference for the subsequent correction of micro-milling tool clamping accuracy.

A visible/near-infrared real-time imaging spectrometer is designed for hyperspectral imaging on the basis of an Acousto-Optic Tunable Filter (AOTF). Its operating band range is 1.3 μm, in which the visible light camera works in the 400-1000 nm band and the near-infrared camera works in 1000-1700 nm band. A Field-Programmable Gate Array (FPGA) is used as the core processing unit of the spectrometer control system. The Cameralink interface is used to collect camera data, the AOTF frequency is controlled by the serial port. Through the combination of AOTF synchronization signal and the trigger signal outside the camera, the one-to-one correspondence between a continuous image and multi-wavelength cyclic acquisition is realized. Finally, the image data is transmitted to the upper computer through the USB3.0 interface for real-time display. The field test shows that the imaging quality of the spectrometer is good and the system works stably. For images with a 1024×1024 resolution, the real-time transmission rate of the image can reach up to 120 frame/s, which meets the design requirements. In practical engineering applications, the control system has a rich interface, high reliability, flexible interface and strong expansibility.

In order to obtain the true optical characteristics of a Digital Micro-mirror Device (DMD), a test method for the stray light distribution of the micro-mirror unit was proposed and an experimental device was built to test the stray light distribution of a micro-mirror unit in the 2×2 array area.First, a stray light test method is proposed. Then, in view of the small size of the micro-mirror unit and the flexible configuration mode, an illumination system with a continuously adjustable convergent spot size and an imaging system that can clearly image the micro-mirror unit was designed. Finally, the stray light distribution of the micro-mirror unit in the 2×2 array area was obtained through experimentation.The test results show that the reflection energy near the center channel of a single micro-mirror unit is strong, while the reflection energy near the edge is relatively weak. In addition, the micro-mirror unit also reflects part of the energy outside the test area. The maximum absolute stray light intensity of the micro-mirror unit in the test area appears near the central channel, and its gray value is 6.86. The maximum absolute stray light intensity of the micro-mirror unit close to the test area also appears near the central channel, and its gray value is 4.01, which indicates that the stray light near the central channel is strong. The relative intensity of stray light in the test area is relatively weak, which increases sharply from the edge of the test area and reaches the value of 293.5% after about two micro-mirror units, and then decreases sharply.

In order to correct the measurement error caused by a glass medium in high-temperature deformation measurement, we take a glass medium as a part of the camera calibration model. Based on photogrammetry technology and digital image correlation, a binocular camera calibration method in a complex environment is proposed and applied to high-temperature deformation measurements. Firstly, aiming at the calibration difficulty caused by the poor image quality in complex environments, the camera imaging model with distortion correction is adopted to achieve binocular camera calibration by bundle adjustment camera calibration method, which improves the success rate and stability of calibration. Secondly, to solve the problem of low calibration accuracy of binocular cameras in complex environments, the influence of lens focal length, ambient light interference and the distance between glass and camera on the calibration results are analyzed, and the optimal calibration parameters are given, so that the calibration reprojection error is reduced from 0.832 pixels to 0.132 pixels. Finally, the measurement error of the calibration method with and without glass is compared by using the measurement environment with a glass medium, which proves that this method can greatly reduce the measurement error. The test results show that this method can effectively reduce the measurement error of a displacement field caused by glass medium in a high-temperature environment. The maximum decrease of measurement error of the displacement field in the X, Y and Z axes is 70.16%, 76.51% and 40.05%, respectively. The method in this paper can achieve high-precision camera calibration in complex environments, and has good calibration stability. It is an effective way of realizing accurate measurement of high-temperature deformation.

In order to realize the high-precision surface measurement of large-diameter elliptical optical flat mirrors and improve the image quality of large-aperture telescope systems, the absolute measurement algorithm for flat elliptical mirrors is studied in this paper. Firstly, the orthogonal polynomials fitting of an elliptical optical flat mirror is studied. Then, the absolute testing algorithm is studied theoretically. The orthogonal absolute testing algorithm can effectively separate the surface error of the reference mirror from the mirror to be measured, which can realize the high-precision surface reconstruction of the elliptical flat mirror to be measured. To verify the actual testing accuracy of the above method, we carried out an absolute testing simulation and experiment on a 250 mm×300 mm mirror. In the simulation, the possibility that the reference surface error is high was considered. In the experiment, a 250 mm×300 mm elliptical testing area was selected in the Zygo300 mm standard flat surface. The above-mentioned elliptical area was tested by the 150 mm Zygo interferometer, and the surface reconstruction was realized based on the above-mentioned orthogonal absolute testing algorithm. The experimental results show that the surface error separation between the reference mirror and the elliptical mirror can be achieved by using the method described in this paper, and the residual RMS (Root-Mean Square) value of the absolute testing result is 0.29 nm, which proves the feasibility and accuracy of the method described in this paper. The high-precision surface reconstruction of the elliptical flat mirror can be achieved using the above method.

The adaptive optical correction technology can effectively improve the beam quality of solid slab lasers, but with the increase of laser output power, the output beam aperture and the system volume increase gradually, which make the design of adaptive optical correction system more difficult. Therefore, under the premise of meeting the requirements of conjugate detection in the adaptive optical correction system, it is of certain research significance to optimize the size parameters of the detection system as a whole, and realize the detection of multiple parameters such as wavefront phase and beam quality evaluation. In this paper, we realized the multi-parameter detection of 160 mm×120 mm rectangular beam emitted by slab laser under the condition that the overall size of the system is 350 mm×180 mm×220 mm (length × width × height). According to the technical requirements of large detection apertures, limitation of tube length and long exit pupil distance, firstly, the dual-Gaussian initial structure was used to eliminate the aberration. Combined with the aspheric surface technology, the design scheme of splitting detection after high-ratio beam compression was adopted to realize the simultaneous detection and evaluation of multiple parameters. Secondly, the initial parameters of the system were determined based on the principles of telephoto imaging and conjugate imaging. Thirdly, the simulation model of the detection system was established to analyze the imaging quality and the tolerance of the system, which were implemented to provide the basis for the construction of the experiment. Finally, the experiments were carried out to verify the design results. Results indicate that the conjugate wavefront detection, light intensity uniformity detection and beam quality evaluation of 160 mm × 120 mm rectangular beam can be realized under the conditions of the object-image conjugation and size constraint conditions. In the experiment, the β factor of the measured beam is 1.24 times the diffraction limit, and the uniformity is 73.8 %, which meet the technical requirements.

The scattering of light by water is an important factor in the deterioration of underwater image quality. In order to quantitatively analyze the influence of water scattering under the irradiation of a specific light source, the scattering model of underwater light transmission is established, and the Fredholm integral equation for solving the distribution of underwater light field is derived. Under conditions where the light energy underwater decays exponentially with an increase in distance and the volume scattering function of the water is constant, the numerical iterative solution method of the integral equation with boundary conditions is given and the high-precision underwater light field distribution can be obtained. Taking the sun, uniform sky brightness, and underwater and overwater point light sources as examples, the calculation results of their underwater light fields when the water surface is calm are given. This method can be extended to solve the distribution of underwater light fields under arbitrary light source configurations and arbitrary boundary conditions, which lays a foundation for strictly deriving a point spread function and modulation transfer function for water bodies.

To improve the accuracy and efficiency of the dynamic speckle metric for non-destructively detecting far-field target hit-spot intensity in a Target-In-the-Loop (TIL) system, a multi-channel cooperative detection system for acquiring speckle signals is established. The theory of dynamic speckles, the simulation model of this system and the spatial-temporal spectral fusion characteristics are also investigated. As a first step, the power spectrum is obtained by filtering, auto-correlating and Fourier transforming the intensity fluctuations of dynamic speckle detected by the point detector. Then, the feasibility of speckle-metric, obtained by multiplying the spectrum with weights, is explored to monitor the target-focused spot. As a second step, the approach of splicing the temporal signals obtained from different spatial locations on the receiving plane is proposed. Moreover, the prerequisites of this approach are listed. Finally, the effectiveness of the proposed speckle metric obtained by fusing the spectrum is verified through simulations and experiments. The results show that the speckle metric decreases with an increase in the hit-spot size, and the four-channel space-averaging metric can improve the accuracy by a factor of 2 when each group of signals is uncorrelated. Moreover, the metric obtained by spatial-temporal fusion spectrum not only guarantees accuracy but also quadruples the system’s bandwidth. Therefore, the multi-channel cooperative acquisition of the speckle metric can monitor the hit-spot change of far-field moving targets more rapidly than current solutions.

Non-contact detection of various physiological parameters has attract great attention. In this paper, a method of estimating physiological parameters based on imaging photoplethysmography from videos of people’s faces recorded by mobile phone is proposed. First, a "wavelet transform-principal component analysis-blind source separation" algorithm is proposed to extract the video’s RGB three-channel pulse wave signal with a high signal-to-noise ratio. Then, the green channel signal is processed separately in the frequency and the time domains to estimate heart and respiratory rates. The pulse wave signals of the red and blue channels are processed, and combined with the oxygen saturation detected by an oximeter to perform data fitting, the best linear equation for estimating the oxygen saturation value from the facial video is found. Finally, the error of the estimation results of various physiological parameters under natural light is compared, and the estimation results of each parameter under three lighting environments are analyzed. The results show that under the three lighting environments, the average error of heart rate detection is 0.5512 time/min, the average error of respiration rate is -0.6321 time/min , and the average error of oxygen saturation is -0.2743%. In summary, the non-contact physiological parameter estimation method proposed in this paper is highly accurate, universally applicable and stable. Its estimation results are highly consistent with the measurement result of standard instruments, which meets the needs of daily physiological parameter measurement.

To improve the high false-alarm rate and poor real-time capability in detecting infrared small dim targets, a novel algorithm based on visual saliency and local entropy is proposed in this paper. This method solves the problem from coarse to fine detecting of small targets. First, a local entropy method is used to obtain the region of interest. Then, an improved visual saliency method is used to calculate local contrast. Finally, a threshold segmentation method is used to extract dim infrared small targets. The method is verified using a contrast test with TOPHAT and LCM, and the results show that the performance of this method precedes the TOPHAT algorithm and LCM algorithm. The false alarm rate by this method decreases to 62.5% and 33.3% compared with the other two algorithms, and the time cost decrease to 38.6% of that of LCM. The method can achieve accurate detection of infrared dim and small targets in a complicated environment, solving the high false alarm rate and poor real-time capability issues to some extent.

When a hypersonic vehicle maneuvers at a high angle of attack, the jet generated by its off-orbit engine interferes strongly with the high-speed thin atmospheric flow, and the flow field is complicated, and the infrared radiation generated by the flow field is also a landmark event in space-based infrared system detection. In this paper, aiming at interference situation of the jet flow of hypersonic flight vehicle engine and thin flow, Navier-Stokes equations are numerically solved to simulate the interference flow field, and the infrared radiation characteristics of gas are obtained by the line-by-line integration method. Combining with the backward Monte Carlo method, the infrared radiation characteristic of exhaust plume are obtained when the aircraft flight′s altitude is 94 kilometers, with no wind, different incoming flow attack angles and different velocities are considered, and the observability of low orbit satellites is evaluated. The simulation results show that for a given observation position, the intensity of infrared radiation in each band is low when there is no wind, and the maximum value is 10-9 W/m2. Under the influence of incoming flow attack angles, the infrared signal intensity of the flow field increases significantly with greater attack angle and velocities and the maximum value reaches 10-6 W/m2. The atmospheric attenuation effect has great influence on the observability of different observation positions. The results can provide reference for infrared warning and anti-missile of hypersonic vehicle.

The Excess Noise Ratio (ENR) of traditional noise sources is usually less than 20 dB due to the limitation of the working frequency and the power of electronic devices. To solve the problem, we propose a technology to generate a millimeter-wave noise source with a high ENR by two incoherent light beams beating. First, two optical filters are used to filter and shape the broadband amplified spontaneous emission light source. Then, the two obtained beams of amplified spontaneous radiation light with different frequencies are coupled to the photodetector for the beat frequency, which can generate electrical noise signals. A theoretical analysis predicts that a noise source with an ENR larger than 50 dB can be obtained by adjusting the optical spectral, linewidth and optical power of the two incoherent light beams filtered from an amplified spontaneous emission source under the current level of photodetector responsivity. A proof-of-concept experiment achieved a millimeter-wave noise source with an ENR higher than 50 dB. This method could also generate millimeter-wave and even terahertz-wave noise with a high ENR if a higher-speed photodetector was used.

With the development of optoelectronic countermeasures and ultrashort pulse laser technology, the study of the interaction between ultrashort pulse laser and monocrystalline silicon has a very important theoretical and practical significance. In order to further clarify the damage mechanism of 532 nm picosecond pulsed laser on monocrystalline silicon, we have conducted an experimental study to measure the damage threshold, clarify the damage mechanism, and discuss the pulse accumulation effect at low flux. Firstly, using a laser with a wavelength of 532 nm, a pulse width of 30 ps and a metallurgical microscope based on the 1-on-1 laser damage test method, the zero damage probability threshold is determined to be 0.52 J/cm2. Secondly, the damage effect of a picosecond laser irradiated on monocrystalline silicon was studied under different laser fluxes, and it was found that the damage of 532 nm picosecond laser to monocrystalline silicon is manifested as heated-effect damage and plasma impact damage. The increase in energy density can be divided into three stages according to the main damage mechanism: thermal effect (0.52~3 J/cm2), thermal ablation (3~50 J/cm2) and plasma effect (>50 J/cm2), and the damaged areas are corresponded to different growth laws with the laser energy density, respectively. Finally, an experiment for the multi-pulse cumulative effect was carried out at a low laser flux and it was found that at a laser energy density of 0.52 J/cm2, the surface was irradiated continuously for 16 shots. The formation of a heat-affected zone confirms that the cumulative effect of multiple pulses can lower the laser damage threshold on monocrystalline silicon.

In order to develop an excellent Au nanostars therapeutic agent for photothermal therapy and optical coherence tomography, we research the preparation of gold nanostars, photothermal properties, photothermal therapy and applications in optical coherence tomography. By adopting the tip structure to enhance the local surface plasmon resonance properties of gold nanomaterials, the multi-branched Au nanostars is prepared by seed mediated method. The multi-tip structure enables the Au nanostars to have obvious photothermal effect, then its effect as a therapeutic agent for photothermal therapy and contrast agent for optical coherence tomography is explored. The experimental results showed that compared with Au nanoparticles, the multi-branched Au nanostars had a higher photothermal conversion efficiency of 42%, and has good biocompatibility. At the concentration of 100 μg/mL, the survival rate of human breast cancer cells is 82%. Human breast cancer cells are effectively killed by laser irradiation at the concentration of 100 μg/mL, and the survival rate is significantly reduced to 37%. At the same time, Au nanostars also has better optical coherence tomography imaging effect, significantly improving the signal intensity and imaging depth. Au nanostars is a promising multifunctional therapeutic agent with both efficient photothermal therapy and excellent optical coherence tomography imaging capability.

In this paper, we introduce a prefabricabed Ag@SiO2 nanostructure directly into tellurite luminescence glass composed of 70TeO2-25ZnO-5La2O3-0.5Er2O3. We find that the maximum enhancement of visible and infrared excitation spectra intensity of (A) Ag (1.6×10-6 mol/L)@SiO2(40 nm) @Er3+ (0.5%): tellurite glass relative to (B) Er3+ (0.5%): tellurite glass is about 149.0% and 161.5%, respectively. Their maximum enhancement of visible and infrared luminescence spectra intensity is 155.2% and 151.6%, respectively. We also find that sample (A) has a larger lifespan compared to sample (B). Because the surface plasmon absorption peak of Ag@SiO2 is located at 546.0 nm, it completely resonates with the luminescence peak of erbium ions which are also at 546.0 nm. Therefore, the resonance enhancement action of Ag@SiO2 on the luminescence of erbium-doped tellurite luminescence glass is significant. Thanks to the advantages of the step-by-step realization of the silver nano core-shell structure and the production of glass, it can successfully and smoothly control the size of Ag@SiO2. It also has the advantage of strong operability in the manufacturing process of Ag@SiO2@Er: telluride luminescence glass. Its costs are also minor. Moreover, it can not only ensure that the silver is not oxidized, but it can also successfully control the distance between the rare earth ion luminescence center and the silver surface plasma. It can also successfully reduce the back energy transfer, which allows the silver surface plasma to more effectively enhance the intensity of photo-luminescence.

As a testing method for large convex aspheric surface, the single optical wedge compensation test has good applicability, robustness and flexibility. However, various errors are coupled with one another during the test process and these errors are difficult to decouple. This affects the accuracy and reliability of the tests. To address this, a method is developed to calibrate the system error of single optical wedge test paths using a Computer Generation Hologram (CGH). We first analysed the source of system error in the optical path of a single optical wedge compensation test as well as the feasibility of using CGH for the calibration of an optical wedge compensation test system. In combination with engineering examples, a CGH was designed for optical wedge compensators with a diameter of 150 mm. Based on the analysis results, the calibration accuracy of the CGH was 1.98 nm RMS, and after calibration the test accuracy of single wedge compensation was 3.43 nm RMS, thereby meeting the high-precision test requirements of large convex aspheric mirrors. This shows that CGH can accurately calibrate the pose of single optical wedge compensators and the test system errors of optical paths. Thus we address the problems affecting error decoupling in test optical paths, and improve the accuracy and reliability of the single optical wedge compensation method. Meanwhile, using CGH calibration, the system errors of the test optical paths, Tap#2 and Tap#3, were 0.023 and 0.011 λ RMS, respectively.

Dual-wavelength retinal imaging adaptive optics systems are suitable for high contrast and resolution imaging of retinal capillaries. The compensation of the Longitudinal Chromatic Aberrations (LCAs) in dual-wavelength adaptive systems is researched. The LCA is measured, the measured wavefronts are analyzed, and the arbitrary wavefront LCA compensation method is given. An adaptive correction experiment is carried out and the experimental results indicate that the root mean square error of the wavefront is reduced to 0.16 λ (λ=589 nm) and the retinal capillary resolution is improved to 6 μm. This work may be used for the clinical applications of retinal imaging.

Aiming at 640×512 long-wavelength infrared cooled detectors, a cooled long-wavelength infrared optical system was designed to track and detect an infrared target. The optical system adopts the secondary imaging structure to ensure 100% cold-shielding efficiency, and adopts a combination of optical material Ge and ZnS to achieve aberration correction and achromatic design. By introducing the high-order aspheric surface, the high aberration of the system is well-corrected, thus the system structure is simplified. The optical system is composed of 6 lenses. The focal length is 400 mm, the working bands are 7.7~9.3 μm, the field of view is 1.37°×1.10°, and the F-number is 2. The design results show that at a spatial frequency of 33 lp/mm, the MTF of off-axis field of view is more than 0.24, which approaches the diffraction limit and has high imaging quality. In the operating temperature range of -35~+55 ℃, the focusing lens is used to ensure the imaging quality under high and low temperature environments, which can be used for infrared tracking detection over a wide range of temperatures.

Ultraviolet detection technology is widely used in various fields of production and human life. It is thus greatly significant to study wide-spectrum ultraviolet (UV) imager systems. Through deducing the theoretical formula of chromatic aberration, a scheme for correcting the chromatic aberration of the optical system of the wide-spectrum UV imager with the lenses made of single material was proposed. Combined with the performance index of a high-sensitivity dynamic UV imaging detector, the optical system of the 210~400 nm wide-spectrum UV imager with only one lens material and all lenses being spherical was designed. The optical design software CODE V was used to optimize the system and evaluate the image quality. The results demonstrate that the Modulation Transfer Function (MTF) in the entire field of view and waveband of the system is better than 0.6 at the Nyquist frequency of 40 lp/mm and RMS<7.8 μm. Thus, the system has good imaging quality. The system does not contain aspheric optical elements, which makes it not only easy to process and assemble, but also reduces its cost and lays a technical foundation for the development of a wide-spectrum UV imaging spectrometer.

In order to further improve the calculation accuracy and reduce the calculation time of the inverse algorithm in the Risley-prism structure, a new algorithm is proposed. It combines the forward iterative method with the equivalent vector model of the Risley-prism to produce an equivalent vector iterative method of calculation. Firstly, the equivalent vector model of the wedge is established according to its deflection. Then, the vector coordinates of the light emitted from the Risley-prism are solved through vector superposition. The equivalent vector model is then substituted into the two-step inverse solution algorithm to calculate the approximate value of the rotation angle of the Risley-prism. Finally, the inverse equivalent vector iteration algorithm is proposed by using forward iteration and gradual approximation, and the rotation angle of Risley-prism is obtained. The experimental results show that the accuracy of the algorithm reaches 10 μm and the calculation time is less than 0.1 ms. The algorithm can effectively improve calculation accuracy, reduce calculation time, and has application prospects in the field of high-precision beam pointing.

Accurate measurement of three-dimensional attitude angle is widely used in aviation, aerospace, national defense and other fields. In order to realize convenient and accurate measurement of three-dimensional attitude angle, an optical system based on a lens array is designed and an analysis model of micro-three-dimensional attitude angle measurement is established in this paper. In the system, the collimated parallel beam passes through four array lenses arranged in a pyramid shape to form regular array spots on a CCD. By analyzing the distance between the spots on the CCD image, the distance between the adjacent aperture on the lens array and the inclination angle between the lens array and CCD, the beam pitch angle and azimuth angle relative to the receiving system can be obtained. By using the angle of the lines of the array spots relative to the horizontal or vertical plane, the roll angle about the Z axis can also be obtained. Compared with the measurement results of the high-precision autocollimator, the measurement accuracy of the proposed method is verified to be RMS≤0.1″. The results show that the proposed method can realize the measurement of three-dimensional attitude angle.

Image with the scene of haze at night has low contrast, non-uniform illumination, color cast and significant noise. These cause nighttime haze removal from single image to be problematic and challenging. In this paper, we put forward a method that can remove nighttime haze from images and improve image quality. The input image is first decomposed into a glow layer and a haze layer with a modified color channel transformation for glow artifacts and color correction. A new light segmentation function is proposed next by using gamma correction of the channel difference and setting the threshold levels as the probability of a pixel belonging to a light source region. Then we estimate the ambient illuminance map by combining the maximum reflectance prior value with the aforementioned probability and computing the atmospheric light in the light and non-light regions. Finally, we establish a novel linear model to build the connection between the image depth map and three image features including luminance, saturation and gradient map for the light source regions while using the dark channel prior for the non-light source regions. The result of the light segmentation is 0.07, and the parameters of the linear depth estimation are 1.0267, -0.5966, 0.6735 and 0.004135. Experimental results show the proposed method is reliable for removing nighttime haze and glow of active light sources, reducing significant noise and improving visibility.

To address the difficulty in measuring the strain limit of pliable composite film forming tests, a measurement method based on binocular stereo vision combined with digital image correlation is proposed. Firstly, to address the image matching problem in large deformations or cracks in thin films, a weak-correlation step-by-step matching method based on adaptive updating of image matching benchmarks is proposed according to the continuity of adjacent state deformation of series images. Then, according to the differences in the surface strain distribution of the film material with that of the steel parts, a strain field is proposed to fit the limit strain curve of the film material. The software and hardware system of visual measurement is built, and the limit strain curve of a Q235 steel specimen is measured and compared to results from the coordinate grid method. The limit strain accuracy can be improved by 0.02%, which proves the feasibility and accuracy of this method. The pliable composite film specimens prepared by PET, Nylon, Al foil, PP were each measured. The method and system successfully completed the measurement of the forming limit curve of the pliable composite film. The comparative experiments show that the proposed method can quickly and accurately measure the surface strain distribution of pliable composite film during forming. Compared with the coordinate grid method, it has obvious advantages and provides a highly reliable and highly precise method for solving the forming limit strain curve of film materials.

The technology of enhancing fluorescence emission can increase the sensitivity of fluorescence detection and the brightness of Light Emitting Diodes (LEDs), and is of great significance in improving the performance of light-emitting devices. Since the metal structure has a good effect in enhancing the local field and fluorescence emission, and the flexible dielectric material has flexible bendability characteristics, on the basis of above, we propose a flexible structure composed of Metal-Dielectric-Metal (MDM) to enhance the fluorescence emission. The influence of the structure on the directional emission enhancement of quantum dots is systematically studied by using the finite difference time domain method. Theoretical calculations show that the local undulations and arcs of the flexible MDM structure can promote fluorescence enhancement and increase the quantum efficiency of the quantum dots located at the center of the structure by about 7 times. They can alao change the refractive index and thickness of the dielectric to achieve the tunability of the target wavelength. At the same time, the experimental results shows that the flexible MDM structure does have a positive effect on the fluorescence enhancement. This discovery is valuable for future display technologies and flexible light-emitting devices. It is of certain guiding significance for the development and application of high-efficiency flexible devices.

Helmholtz-Kohlrausch effect (H-K effect) describes the influence of color purity on the perceived brightness of a colored object. Quantum dots (QD) based backlights can enhance the color quality of Liquid Crystal Display (LCD) with improved perceived brightness due to the well-known H-K effect. However, the H-K effect of QD embedded TVs (also known as QLED TV) has not been fully demonstrated. In this paper, we investigated the H-K effect of QLED TVs through a comparative study between QLED backlights and YAG-LED backlights. By comparing the viewers’ experimental results with the Kaiser and Nayatani model, we demonstrate that a QLED TV shows significant H-K effect. To achieve the same perceived brightness with YAG-LED TV, the physical brightness of QLED TV was greatly decreased to 75% for pure red, 86% for pure green, and 74%-88% for bright colorful images. Moreover, QLED TVs are strongly preferred over YAG-LED TVs even when both QLED TV and YAG-LED TV show the same perceived brightness. The results imply the bright future of QLED TVs toward healthly displays.

Owing to the strong penetrating ability in the atmosphere, 532 nm-wavelength green laser has wide applications including free-space optical communications and laser three-dimensional mapping. A spectral filter, with a half-power bandwidth of less than 100 pm, is an important optical element to suppress the interference of background light. Therefore, an ultra-narrow band-pass filter based on optical interference film is designed and fabricated in this paper. The high and low refractive index film are made of tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2), respectively. The designed optical thin films are deposited on a fused quartz substrate by double-ion-beam sputtering deposition method. The transmission spectra of the filters are measured by a tunable laser and a power meter. The half-power bandwidths of the filters are (60±2) pm, and the transmittance reaches 62.6%.

It is very important to study the propagation characteristics of light beams in ocean turbulence. In order to get closer to the actual situation, we build a device which can control both the salinity and the intensity of underwater turbulence to study the propagation characteristics of vortex beams and a Gaussian beam in underwater turbulence. The results show that compared with the underwater turbulence without sea salt, the light spot will be more diffuse and the light intensity will be weaker in the underwater turbulence with sea salt. When the topological charge m is 2, the scintillation index of the vortex beam in the underwater turbulence with salinity of 4.35‰ is larger than that in the underwater turbulence with salinity of 2.42‰, no matter it is strong turbulence or weak turbulence. When the vortex beam with m=2 propagates to the same distance, the scintillation index increases with the increment of the salinity and the intensity of underwater turbulence. Under different salinity conditions, the radial scintillation index of the vortex beam with m=2 decreases firstly and then increases with the increase of the radial distance. In addition, we set up another experimental device which can transmit a longer distance. The scintillation index of the vortex beam with m=2 is much higher than that of the Gaussian beam in the underwater turbulence within 20 m propagation distance, and the scintillation indices of both the vortex beam with m=2 and the Gaussian beam increase with the increase of the propagation distance.

A high-sensitivity Surface Plasmon Resonance (SPR) sensor comprising of an eccentric core ten-fold Photonic Quasi-crystal Fiber (PQF) with a D-shaped structure and partially coated with Indium Tin Oxide (ITO) is designed and numerically analyzed. The eccentric core D-shaped structure makes the analysis of liquids more convenient and also strengthens the coupling between the core mode and Surface Plasmon Polariton (SPP) mode to improve the sensing sensitivity. The characteristics of the sensor are investigated by the Finite Element Method (FEM). The wavelength sensitivity increases with increasing Refractive Indexes (RIs) and the maximum wavelength sensitivity and resolution are 60000 nm/RIU and 1.67×10-6 RIU, respectively. The sensor delivers excellent performance and has large potential applications in the measurement of liquid refractive indexes.