The application of nanofluids in spectral beam splitting (SBS) hybrid PV/T system can improve its efficiency, in which nanoparticles (NPs) with appropriate size can effectively filter solar radiation outside the spectral response of photovoltaic cells. The optical properties of Au, Ag, Cu, Fe3O4, ZnO and TiO2 NPs were simulated by finite difference time domain (FDTD) method. Moreover, taking spectral response of monocrystalline silicon solar cells as example, the optical absorption properties of six NPs with diameters ranging from 20 nm to 200 nm were studied, and degree of appropriateness (DOA) was used as the evaluation index to optimize the particle size. The results show that the optical properties of NPs are very sensitive to their particle size. By changing the particle size of NPs, the positions of scattering, absorption and extinction peaks can be adjusted in a wide range, and the peaks increase with the increase of particle size. The absorption capacity of metal NPs to solar radiation is better than that of non-metal NPs. The maximum absorption power per unit volume of six NPs are 21.88 GW/m3, 17.95 GW/m3, 20.16 GW/m3, 2.54 GW/m3, 1.02 GW/m3, 0.27 GW/m3, respectively. The DOA index analysis shows that the optimal particle sizes of six NPs suitable for SBS hybrid PV/T system are 20 nm, 50 nm, 20 nm, 170 nm, 110 nm, 20 nm, respectively.

The modulation phase was solved based on the geometric steady-phase method, the Fourier transform was carried out through Fourier lens, and the corresponding flat-top beam was focused at the rear focal plane, so that the circular Gaussian beam was shaped into a square flat-top beam, in which the optical path parameters had a great influence on shaping quality. In the experiment, it was found that the square flat-top beam was affected by the zero-order light and had poor uniformity. Therefore, the causes of the zero-order light were analyzed in detail and effective solutions were proposed. The zero-order light in the experimental results was directly removed by stacking the shining grating. The experimental results show that the energy utilization rate of square flat-top beam is 72.3%, and the beam uniformity is up to 97.2%, which is better than the traditional shaping method. Furthermore, the quality of beam shaping by geometric steady-phase method are further analyzed for three factors: the offset of hologram, out-of-focus and waist radius of incident beam, which provides convenience for the application of beam shaping by geometric steady-phase method.

The characteristics of traditional direct and oblique laser displacement sensor were analyzed. Combined with their advantages, a compact laser displacement sensor based on auto-collimation principle was designed. In the structure, the linear structure was used to replace the optical path layout of the large triangle, and the auto-collimation optical path structure was formed. A beam splitter with a splitting ratio of 50% was introduced and placed at an angle of 45° with the optical axis to combine the focusing lens and imaging lens into one, and made the condenser, beam splitter and photo-detector coaxial, which simplified the system structure and reduced the volume of the instrument. At the same time, the Scheimpflug condition conforming to the auto-collimation principle was derived. The optical design software Zemax was used to simulate the optical system. The system adopts the structure of single lens, the front surface is Forbes aspheric surface, the entrance pupil diameter D is 4 mm, the field angle 2 ω is 4°, the total length L is 20 mm, and the imaging quality and system size are the best. The system has the characteristics of large measurement range, high resolution, small structure size and small light energy loss. Compared with the experiments of Keyence laser displacement sensor, the system can ensure the technical indexes of probe resolution 1 μm and comprehensive detection accuracy ±2 μm.

Using C32 molecule as the skeleton of multipole moments, two types of substitutional co-doped fullerene derivatives C28B2N2 and C28B2P2 were designed with 16 isomers. The electronic properties, linear polarizability α and first hyperpolarizability β were studied by CAM-B3LYP method of density functional theory (DFT). The results show that the HOMO-LUMO gap of the doped molecules becomes smaller, and the values of α and β of C28B2P2 are larger than those of C28B2P2. Additionally, dipole molecules in these molecules have large β, while the octapolar molecules have smaller β. The structure with excellent second-order nonlinear optical (NLO) response characteristics is selected. The calculation results of time-dependent density functional theory (TD-DFT) method show that, compared with C32, the response range of absorption spectra of all doped structures becomes wider, the maximum intensity becomes weaker, and the position of the maximum absorption wavelength may be red-shifted or blue-shifted. Based on the sum-over-states (SOS) method, the two-level or three-level formulas are used to explain the origin of large β in two co-doped structures, and verify the related electronic excitation type is π→π* excitation.

In order to meet the application requirements of high-definition fish eye lens in the information age, a large-aperture glass plastic hybrid fish eye lens optical system matching a 16 mm (1") CCD was designed by using CODE V and ZEMAX optical software. The system provides clear imaging in the spectrum range of 486 nm~656 nm and 850 nm. The field angle is 210°, the F number is 2.0, the focal length is 4.1 mm, the F-Theta distortion is less than 7%, and the edge illumination is more than 68%. At normal temperature, the MTF of 0.707 field of view is greater than 0.5 and the MTF of full field of view is greater than 0.35 at the Nyquist frequency of 91 lp/mm. At ?40 ℃~75 ℃, the MTF of 0.707 field of view is greater than 0.3, and the MTF of full field of view is greater than 0.2, which can meet the requirements of high and low temperature environment. The design adopts a 7-piece glass plastic hybrid structure, which has the characteristics of large field of view angle, large target surface and large aperture. It can be widely used in high-definition camera, security monitoring, industrial production and other fields.

The whispering gallery mode (WGM) microcavity has ultra-high Q factor and an extremely small pattern volume, and has a broad application prospect in the fields of microwave photonic systems, nonlinear optics and quantum optics. By analyzing the loss factors of millimeter-scale magnesium fluoride (MgF2) crystal WGM microcavity, it was confirmed that the main indexes affecting the quality factor of WGM microcavity were material grade and surface roughness. The structure of WGM microcavity was designed with millimeter-scale MgF2 crystal, and the DUV-level MgF2 crystal was used. Assuming the surface roughness of WGM microcavity was less than 0.7 nm, the theoretical calculation value of limit loss was 4.781×10?11 and the corresponding limit Q value was 2.09×1010. Through rough machining, precision turning and precision polishing of WGM microcavity of MgF2 crystal, the microcavity manufacturing with high quality factor was realized. The test results show that the surface roughness of WGM microcavity is 0.669 nm (Ra value), the shape error is 6.767 nm (PV value), and the quality factor is 2.054×109@1 550 nm.

In order to solve the problem of color inconsistency between the projection pictures of various projectors in a multi-channel projection display system, a multi-projection color correction method based on free-form deformation technology was designed. Firstly, the free-form deformation model was established by Bernstein basis function, and the color conversion relationship between the original image of each projector and the image taken by the camera was established. Then, collected the original image set and the projection display picture set taken by the camera to determine the parameters of the free-form deformation technology model. Moreover, through Matlab analysis, it was verified that each color channel of projection image was affected by each other. Finally, the original image was color distorted, and the proposed color correction method was compared with the traditional method for histogram similarity evaluation. The experimental results show that, compared with the generalized color correction method and the color correction method based on B-spline curve, the proposed method reduces the average difference of color intensity of the projected image by 2.50 in the B channel, 2.34 in the G channel, and 3.57 in the R channel. The correlation of histogram is increased by 8.9%, and the Pap distance is reduced by 9.7%.The multi-projection color correction method based on free-form deformation makes the projection images smoothly connected, and brings the user a better immersion experience.

As a medical device for diagnosis and treatment, the distortion of medical rigid endoscopes directly affects the accuracy of the surgeons judgment of the surgical position. Therefore, the measurement of endoscopic relative percent distortion is an urgent problem to be solved. A relative percent distortion detection system based on image processing was designed, and the images of the calibration target plate were acquired by a CCD camera. After vertical calibration of endoscope visual axis and target plate, the distortion target plate was replaced to collect images. The computer filtered the obtained image, extracted the region of interest and carried out the size statistics, and the relative percent distortion was finally obtained. Using a 30° laparoscope as the measurement model, the experiments show that the relative percent distortion value measured by the designed calibration system at 70% of the full field of view of the endoscope to be measured is better than that of the system without vertical calibration by 2.2%. The results show that the system has higher consistency of detection results and higher accuracy than the system without vertical calibration.

The reflective high-resolution optical system is the future development direction of airborne telescope system. When the optical system works on the aviation platform, there will exist offset errors in the optical system, which needs to be corrected in the air due to the influence of temperature change, vibration and impact. The nonlinear function mathematical model between mirror misalignment and Zernike coefficients was established, and the Bhattacharyya coefficient method was used to eliminate the highly correlated misalignment, reduce the complexity of the air alignment and increase the reliability. After correcting a coaxial three-mirror anastigmatic system, the results show that the root-mean-square (RMS) value of wavefront aberration reduces to 0.025 λ, which is 0.014 λ different from the design value, and satisfies the demands of air alignment.

In order to build a re-detection module suitable for long-term tracking, inspired by the GlobalTrack method which improves two-stage detection network, an efficient deep network for end-to-end re-detection of specific template targets was proposed. First, for more efficient fusion of template features on large-scale images, the depth-wise correlation method was improved by constructing a cross-information enhancement module, which encoded the information of search and template features with cross channel-attention information. In addition, the region proposal network (RPN) and region-based convolutional neural networks (RCNN) structure of traditional two-stage detection network were replaced with a dynamic instance interaction module, guiding the classification-and-regression stage of the detection network with template information as well as building an end-to-end sparse re-detection structure. Comparing results on LaSOT and OxUva long-term tracking datasets, the performance of proposed method is improved by 3%, and the real-time frame rate is improved by 173% compared with those of the original method. The experimental results show that the improved method can re-detect template targets more accurately and quickly in the whole image range.

Aiming at the problems of fuzzy details and low contrast in infrared images, an infrared image enhancement algorithm based on secondary guided filtering was proposed. Firstly, the original infrared image was used as the guided image, and the guided filter was used to extract the detail information of the infrared image. Secondly, the obtained detail information was processed by guided filtering again to extract the detail information with lower noise. Finally, the original infrared image and the details of the two parts were weighted and summed to achieve infrared image enhancement. The proposed algorithm can improve the contrast and the details of the infrared images. Experimental results show that, compared with other enhancement algorithms, the average contrast and the average gradient of infrared images enhanced by the proposed algorithm is increased by 123% to 246% and 56% to 101%, respectively. The visual effect is significantly improved, and the details can be highlighted more clearly. Implementing the proposed algorithm based on field programmable gate array (FPGA) has low resource consumption. It takes up to 10.12 ms to process the single-frame infrared image with 640×512 resolution, which can meet the real-time requirements of the infrared detection system and has certain practical values.

Detection transformer (DETR) is a target detection algorithm based on Transformer, which has the advantages of fast detection speed and good detection effect. A measurement system based on DETR and binocular vision principle for people, vehicles, bicycles, signal lights and other targets in road environment was introduced. The principles of binocular ranging, camera calibration, target detection and target matching were analyzed, and the measurement system was constructed on this basis. The target detection algorithm was used to detect the targets in the field of vision, and the principle of binocular vision was used to measure the distance of the detected targets. The source of measurement error in the measurement system was analyzed and the influence on the results was calculated. The algorithm was tested in KITTI data set and real environment. The system baseline is 45 cm, the detection rate of 15 m~80 m specified targets is higher than 90.6%, and the ranging error is less than 5.8%. The proposed algorithm can run in real time on RTX 2080Ti platform.

In view of the low accuracy of the current bridge disease detection algorithm based on convolutional neural network, an improved YOLOX algorithm was proposed to improve the detection accuracy. By using the feature information of the shallow layer of the backbone network, the feature extraction enhancement network was improved, and the feature information of the same layer was added for fusion. An improved coordinate attention mechanism was introduced to combine the position information and the channel information to enhance the network recognition of bridge diseases. At the same time, the localization loss function was improved. The experimental results show that the accuracy of the improved YOLOX network structure for bridge disease detection reaches 92.11%, which is 4.40% higher than the original network.

The detection of concealed targets has always been a focus of military research. With the development of hyperspectral imaging technology, a new solution was provided for this field. By using the high spectral resolution of hyperspectral data, the spectral discrimination of concealed targets and backgrounds could be realized in some wavebands. A hyperspectral concealed target detection technology based on ACE algorithm was proposed, which made full use of the different characteristics of backgrounds and concealed targets in different bands. The spectral rearrangement technology and first-order differential technology were introduced to make the background spectrum oscillate and extract the targets. Compared with other algorithms, the proposed algorithm has higher extraction accuracy and lower false alarm rate, which achieves better detection effect of concealed targets.

Terahertz time-of-flight (THz-TOF) method is a new development direction in the field of thickness measurement, which has the advantages of fast, non-destructive and high precision. However, the water vapor in atmospheric environment has strong absorption of terahertz wave, which limits the application of THz-TOF method in atmospheric environment. The propagation mechanism of terahertz wave in atmospheric environment in THz-TOF method was firstly analyzed, and then a method of water vapor elimination based on absorption model was proposed. Finally, two kinds of plastic plate samples were used as the object of application research. By comparing with the measurement results in dry environment, the results show that the method can effectively eliminate the interference of water vapor and realize the accurate measurement of material thickness and refractive index in atmospheric environment.

Vertical-scanning white light interferometry (VSWLI) is a non-contact three-dimensional surface profile measurement method. As an inherent defect in VSWLI, the batwings are especially significant at the step edge when the step height of the measured sample is smaller than the coherent length of the light source. The phase-shifting interferometry does not suffer from it, but has phase ambiguity problems. A white-light interference demodulation algorithm that combined Carré equal-step phase-shifting algorithm with fast Fourier transform (FFT) coherence-peak-sensing technique was proposed to overcome the above problems. This algorithm was based on successive variational mode decomposition (SVMD) combined with Hausdorff distance (HD) denoising. The continuous step devices at 500 nm and 1 200 nm height and the standard steps at 10 μm height were used as test samples for verification of experimental measurements. The proposed algorithm can effectively suppress the batwings effect at the step edges and remove the phase-ambiguity problems.

Aiming at the problems of unsatisfactory processing effect and long processing time in point target detection algorithm of single-frame infrared image with complex background, a hierarchical convolution filtering detection algorithm was proposed. It was mainly divided into two parts: firstly, according to the characteristics of small infrared targets, a hierarchical convolution filtering operator was designed to filter the image, so as to achieve the effect of efficiency increase and background suppression of small targets in the image. Secondly, the adaptive threshold method based on the maximum value was used to binarize the image to filter the background clutter, and finally extracted the target to be detected. Experiments in a large number of infrared images with different backgrounds show that the performance quantization results of background suppression factor and signal-to-noise ratio gain of the algorithm are better than that of the existing five typical infrared dim and small target detection algorithms, and the average processing time is only 30.42% of Laplacian of Gaussian (LoG) filtering algorithm. Through the experimental comparison, the hierarchical convolution filtering method can effectively solve the problem of small target detection in infrared images under different complex backgrounds.

In order to meet the needs of digital in-situ detection of hole making quality for aerospace large components, a multi-view point cloud registration method based on feature locating plate was proposed, which realized the reconstruction and detection of 3D morphology of integral hole wall. Firstly, the requirements of multi-view detection of hole making were analyzed, and a method of multi-view point cloud registration assisted by feature locating plate was proposed. Then, the design of quadrilateral feature plate with unequal interior angles and the corresponding point cloud segmentation as well as recognition algorithm were introduced. Also, the method of multi-view point cloud registration and parameter extraction based on feature self-localization was described. Finally, combined the mechanical arm to build the experimental platform, the titanium, aluminum and composite materials commonly used in aerospace were tested, and the average error was 0.011 mm, 0.034 mm and 0.041 mm, respectively, which verified the reliability of the system. The robustness of this method was demonstrated by comparing the detection results of traditional single-view method with that of the proposed method.

The traditional interferometry method of large-aperture optical element relies on artificially changing the beam expanding lens and optical path structure according to different test samples. This method inevitably introduces some systematic errors. Therefore, a set of corresponding dual-line control scheme was proposed according to the functional requirements of the dual-optical path interferometer and the simulation experiment. Through the cooperation of bluetooth communication, serial communication and mechanical structure, the optical path could be converted and calibrated for many times, so that the changing position of the optical element after each switch of the measurement diameter was fixed, and the real-time status was displayed in the interactive interface based on microsoft foundation classes (MFC). The results show that under 450 mm measurement diameter, the measurement repeatability of PV10 can reach 0.004 λ, and that of root-mean-square (RMS) can reach 0.000 4 λ. Under 100 mm measurement diameter, the measurement repeatability of PV10 can reach 0.000 8 λ, and that of RMS can reach 0.000 16 λ. Finally, the experimental results show that the system ensures the superior measurement efficiency and repeatability, which provides reference value for the research and development of dual-optical path interferometers.

A set of 1 064 nm and 532 nm automatic measurement device of laser-induced damage threshold (LIDT) of dual-wavelength optical elements was designed and constructed for automatic detection of LIDT of optical elements film. The device was mainly composed of pulsed laser light source, beam parameter diagnosis component, damage online diagnosis component, scanning motion platform for parts to be tested and control system. The whole measuring device and measurement process were automatically controlled by the computer integrated measuring software based on Labview, which could realize the automatic measurement of damage threshold in the range of energy density from 0.1 J/cm2～100 J/cm2, and the device was also used to measure the 1 064 nm antireflection film and aluminum reflection film samples. The results show that the damage thresholds are 27.09 J/cm2 and 3.21 J/cm2, with a relative uncertainty of 3.91% and 5.61%, respectively.

On-site rapid detection of nucleic acid has the advantages of convenience, simple operation, no need for special laboratories, and rapid reporting, which can be detected in various complex environments such as airports, community hospitals, customs and fields. A fluorescence detection system that can be applied to on-site rapid detection instruments of nucleic acid was established, including non-confocal orthogonal optical path and multi-channel detection integrated structure. The former has the characteristics of high signal-to-noise ratio, small and convenient. The latter has high switching efficiency and can meet multiple detection, and its embedded structure greatly reduces the fluorescence crosstalk between channels. The experimental results show that the detection limit of the system is lower than 1.6 μg/mL, the R2 value (coefficient of determination) of fluorescence detection gradient is greater than 0.99, and the coefficient of variance (CV) value of repeatability test does not exceed 1.27%. The inter-channel fluorescence crosstalk test shows that there is no crosstalk between channels, and the accuracy and stability of cytomegalovirus culture medium amplification experiment are good, which indicates that the system can effectively stimulate and collect fluorescence for multiple detection.

Aiming at the problem that transmittance parameters of infrared optical system cannot be accurately measured, the measurement and calibration technology for spectral transmittance of infrared optical system were studied. Based on the analysis of measurement methods such as integrating sphere method and large-area uniform source method, a calibration device for spectral transmittance of infrared optical system based on method of reflection was studied and constructed, and the complete quantity traceability and quantity transmission chain of spectral transmittance were established. The device was used to measure the spectral transmittance in the wavelength range of 2 μm~14 μm, and the uncertainty analysis of the measurement results showed that the result was 2%. Compared with the previous measurement device, the measurement results of the proposed device have higher accuracy and reliability.

Digital low-light-level (LLL) devices, as the core devices of the new generation of LLL night vision equipment, have been paid more attention by mang countries because of their advantages of digital output compared with traditional vacuum LLL devices. The research statuses of low illumination charge-coupled devices (CCD)/complementary metal oxide semiconductor (CMOS), scientific CMOS, image intensified CCD/CMOS, electron multiplying CCD, and electron bombarded active pixel sensor (APS)/CCD digital LLL devices were reviewed, and the application of digital LLL devices was analyzed. Finally, the development trends of LLL technology and digital LLL devices were proposed.

Apparent distance is an important parameter to evaluate the performance of low-level-light (LLL) night vision imaging system. With the development of LLL night vision detection technology, the simulation results of the classical apparent distance model show some deviations from the actual measurement data, especially the simulation results are not ideal under the low illumination of 10-3 lx, which causes great obstacles to the practical application of the LLL night vision system. Aiming at this problem, the classical apparent distance model was modified from three aspects: the first is considering the influence of atmospheric transmittance on the apparent distance of LLL night vision system and modifying the atmospheric transmittance factors in the classical apparent distance model, the second is optimizing the apparent distance model based on noise factors of image intensifier, the third is considering the influence of human visual transmission characteristics on the apparent distance of LLL night vision system, and the simplified human visual system was added into the transfer function model of the system. The improved apparent distance model was derived, and its effectiveness as well as practicability were verified by the field test data, which had certain guiding significance for the design, evaluation and application of LLL night vision system.

The liquid-solid phase transition time characteristics of temperature rise of aluminum layer metal of CCD detector induced by nanosecond pulse laser were studied from the aspect of theoretical simulation calculation. The temperature rise curve of aluminum layer metal material of CCD detector induced by nanosecond laser was simulated by Fourier heat conduction equation, and the variation rules of the starting time and time length of liquid-solid phase transition of aluminum layer metal material with laser pulse peak power and laser incidence angle were obtained. The theoretical calculation results show that the maximum temperature of the aluminum layer surface of CCD detector gradually increases with the increase of the incident laser pulse peak power, the starting time of the liquid-solid phase transition delays, and the time length increases. The maximum temperature of aluminum layer surface gradually decreases with the increase of the laser incidence angle, the starting time of liquid-solid phase transition moves forward continuously, and the time length becomes shorter. The results show that the laser pulse peak power density and the laser incident angle have important effects on the liquid-solid phase transition time characteristics of CCD detector induced by nanosecond pulsed laser, which has important theoretical significance for revealing the thermal damage mechanism of nanosecond laser induced CCD detector.

The three-channel 355 nm optical frequency discriminator is widely used in the frequency discrimination of the backscattered signal of the space-borne wind lidar, which is the core component to discriminate the wind speed Doppler frequency shift in the double-edge method, and its parameters and reliabilities determine the detection accuracy of the system. A 355 nm three-channel etalon module based on piezoelectric transducer (PZT) crystal tuning was developed, with the effective diameter of 35 mm, the peak transmittance of 75%, the free spectral range of 12.5 GHz, and the full width at half maximum of 1.7 GHz. Through the three-channel test system, the parameters including free spectral range, full width at half maximum, peak transmittance, and tuning coefficient were tested. The test results show that when the external driving voltage is 75 V, the peak transmittances of the three channels are 0.859, 0.878, and 0.735, respectively. The full width at half maximum is 1.843 GHz, 1.882 GHz, and 1.611 GHz, respectively. The tuning coefficients are 1.96 GHz/V, 1.93 GHz/V, 1.88 GHz/V, respectively. In view of the inconsistent tuning coefficients of three channels of the PZT crystal of the optical frequency discrimination module, the influence range of the analysis on the wind speed error is ±0.1m/s. Through the test of the closed-loop control system, the system can realize the real-time locking of the 355 nm laser emission frequency, solve the problems caused by the inconsistent initial position of the optical frequency discrimination module in each working state, improve the frequency discrimination of wind speed, and can achieve the stable locking time of more than 30 minutes, which meets the application requirements of space-borne wind lidar. Simulation studies show that when the interval of three-channel optical frequency discrimination module changes by 0.08 nm, the resulting wind speed error is 1 m/s.

The experimental study of beat frequency signal envelope extraction based on single-cavity and dual-comb was carried out. A piece of polarization-maintaining fiber (PMF) with strong birefringence was introduced into a single fiber laser to make the pulses multiplexed and mode-locked in two directions with orthogonal polarization. By finely adjusting intracavity polarization states, the continuous adjustable dual-comb generation was realized in the range of 337 Hz~2.33 kHz. The dual optical frequency combs with extinction ratios of 28.5 dB and 38.2 dB were obtained by laser extra-cavity polarization states regulation and polarization beam splitting. After asynchronous sampling of the dual optical frequency combs, the designed envelope detection circuit was used to extract the envelope of the beat frequency signal. Compared with the results of envelope extraction algorithm based on spline interpolation and Hilbert transform, the extracted peak position of the envelope was basically consistent, which verified the feasibility of the method. The experimental study of dual-comb beat frequency signal envelop extraction can quickly extract envelope shape and envelope peak position in real time, which can be further applied in the fields of envelope signal triggering and precise ranging.

The main oscillation power amplification (MOPA) structure has become one of the mainstream designs of high-power fiber laser due to its good beam quality and adjustable parameters. In order to improve the output performance of high-power ytterbium-doped fiber laser (YDFL) and increase the optical-to-optical conversion efficiency of the system, a MOPA structure all-fiber high-power laser based on 915 nm pump laser and double clad ytterbium-doped fiber (YDF) was reported. The high-power fiber laser was composed of a seed laser pumped by an electrically modulated laser diode (LD) and a ytterbium-doped fiber amplifier (YDFA). In continuous wave (CW) mode, after the laser seed source passing through the YDFA, the laser output with the center wavelength of 1 069.96 nm was realized, and the maximum average output power was up to 945.9 W. The slope efficiency of the MOPA structure laser is as high as 74.12%, which has good robustness. The research scheme has reference significance for the development of high-power MOPA structure fiber laser.