With the rapid development of smart grids, large-scale investment in measurement equipment for monitoring the operation of power grids, the monitoring data such as massive operation images generated by them is difficult to be effectively utilized due to problems such as large scale, high dimension and data redundancy. In order to further improve the analysis and application ability of power big data, this paper proposes a power grid operation image data compression method based on deep learning. Considering the coupling correlation of power grid image monitoring data in time series, the power grid operation image data is compressed through convolutional neural network, effectively reducing the redundancy of power grid operation image data. Compared with other methods, the image data compression model based on convolutional neural network does not rely on manual data feature extraction and engineering experience, and can directly use the grayscale function of the original image data collected from the power grid as the input of the model, and the data The feature extraction and classification are combined into one, to achieve efficient and convenient compression of power grid operation image data. The effectiveness of the method proposed in this paper is verified by simulation. The results show that the proposed method has strong advantages in power grid image compression efficiency and compression accuracy compared with other neural networks.

In order to improve the recognition ability of optical characters in non-cooperative target areas, and enhance the accuracy of information collection such as power nameplates and power grid texts, an optical character recognition system was designed that simultaneously collected polarized images and visible light images and performed image fusion. By setting the polarization angles of 0°, 60° and 120°, the response voltage was periodically modulated to obtain the connectivity range of the effective information region and achieve accurate boundary constraints. By calculating the polarization angle calibration parameters and setting reasonable thresholds of boundary conditions, a range standard was provided for image fusion. The function curves of the response voltage on the polarization angle and the test distance were tested in the experiment, and the results showed that the slope of the periodic change of the polarization angle was 53.1 mV/(°). In the range of 0.5-3.0 m, the maximum value of the response voltage was 241.7 mV, the minimum voltage was 18.5 mV, and the monotonicity of the three response curves was almost the same. The experiment was carried out on the power nameplate target with poor image definition. The results showed that after traditional image filtering and enhancement, the contrast ratio of the blurred original image was increased from 0.34 to 1.56, and the image quality was improved to a certain extent, but there were still some characters that could not be identified. After using this algorithm, the contrast ratio reaches 3.23, and some fuzzy characters can also be effectively recognized. It can be seen that the system is suitable for optical character recognition of non-cooperative targets, and has a good optimization effect on optical character recognition in low-quality images.

Infrared and visible image fusion technology makes full use of the advantages of different sensors, retains the complementary information and redundant information of the original image in the fused image, and improves the image quality. In recent years, with the development of deep learning methods, many researchers have begun to introduce this method into the field of image fusion, and have achieved fruitful results. According to different fusion frameworks, the infrared and visible image fusion methods based on deep learning are classified, analyzed and summarized, the commonly used evaluation indicators and data sets are reviewed. In addition, some representative algorithm models of different categories are selected to fuse different scene images, the advantages and disadvantages of each algorithm are compared and analyzed by evaluation indicators. Finally, the research direction of infrared and visible image fusion technology based on deep learning is prospected, infrared and visible fusion technology is summarized, which is the basis for future research work.

Infrared small target detection plays an important role in applications such as infrared target search and tracking. In this paper, we propose an infrared small target detection algorithm combining two-dimensional empirical modal decomposition and multi-scale patch contrast algorithm. First, the infrared image is decomposed into modal components of different scales using two-dimensional empirical modal decomposition, and then the low-frequency modal components are removed for image reconstruction to achieve the suppression of background clutter. Then, the reconstructed image is used as the input of the multi-scale patch contrast algorithm to generate the target result map. Finally, adaptive threshold segmentation is performed on the target result map to detect the real infrared small targets. The experimental simulation results show that the algorithm can effectively suppress the background interference to the target with high detection rate under different backgrounds compared with the existing algorithms, which verifies the effectiveness and robustness of the algorithm.

To solve the problem of low accuracy of multi-scale rotating face detection under complex conditions such as large-scale pose change and large-angle face rotation-in-plane, a rotating face detection method based on parallel cascade convolution neural network is proposed. Using a coarse-to-fine cascading strategy, multiple shallow convolutional neural networks are cascaded in parallel on multiple feature layers of the main network SSD. Face/non-face detection, face boundary box position update and face RIP angle estimation are gradually completed. Experimental results on Rotate FDDB dataset and Rotate Sub-WIDER FACE dataset show that the proposed method achieves advanced face detection. The detection precision of the method is 87.1% and the speed is 45 FPS when 100 false positives occur in the rotating Sub-WIDER FACE dataset, which proves that the method can achieve accurate rotating face detection with low time loss.

To make intelligent identification of leaked steam in complex industrial field, a temperature field characterization and recognition method using infrared vision technology is proposed. The steam leakage process is simulated to reveal the occurrence and development characteristics of its temperature field, including diffusion characteristics, hammer tail characteristics, dynamic characteristics, and centrality characteristics. The temperature layer of steam temperature field is extracted, the detailed characteristics of temperature distribution are analyzed, and the variable scale gray processing method is proposed to realize the high-definition image representation of steam infrared temperature field. To improve the identification speed and accuracy, the MASK-RCNN model is established to make deep learning and dynamic mining of hammer tail image features of leaked steam. In this way, the recognition accuracy of single hammer tail is about 90.71%, and that of the overall algorithm is up to 99.93%. The algorithm is tested with leaked steam recognition in power plant equipment operation. Results show that time consumed to process 5 consecutive frames is about 0.50 s, and steam leakage of various particle sizes can be identified quickly and accurately.

The research demonstrates that when the temperature changes a lot, the internal components of the large sky area multi-object fiber spectroscopic telescope (LAMOST) spectrographs will produce thermal-induced flexure, which will cause the image blurring of the CCD. Such image blurring reduces the measurement accuracy of astronomical data and greatly increases the difficulty of the daily maintenance of the 16 spectrographs.Therefore, a defocus diagnosis method for multi-object image definition evaluation is proposed based on the calibration lamp spectrum taken by LAMOST. By analyzing the spectrum image under the different defocusing amounts, the half-height full-width (FWHM) and its distribution of spots are obtained to establish the function model between the multi-target image definition and the defocusing amount of the system. It can realize the fast defocus diagnosis of the spectrum image quality of LAMOST and provide a reference for the realization of intelligent active compensation technology of LAMOST spectrograph. In this paper, the principle and structure of the LAMOST spectrograph are introduced, and the demand for the focusing precision of the spectrograph is given. And the measurement principle of FWHM value and the construction method of the multi-object image definition evaluation function are introduced in detail. Compared with the traditional image definition evaluation function, the results show that the proposed method has a higher definition ratio and accuracy. And the defocus diagnosis error of the spectral image is less than 10 μm, which effectively reduces the error caused by artificial diagnosis and improves the consistency of the 16 spectrographs. This method can also improve the daily operation efficiency and long-term stability of the LAMOST spectrographs.

With the continuous development of high-speed aircraft, target detection and recognition, as a key part of precision guidance, requires higher real-time and high-accuracy target positioning and recognition. At present, the need for accurate detection and identification of time-sensitive targets such as armored vehicles and vehicle positions is increasingly urgent. Deep learning algorithms have advantages in feature extraction and classifier design. This paper takes the small-sized infrared vehicle target under a specific complex background as the research object, and develops a lightweight deep learning algorithm based on infrared dim vehicle target detection and recognition to meet the needs of less sample data, limited platform resources, high real-time requirements, and high detection accuracy. The project is light-weight cut based on the YOLOv5 algorithm, reduce the structure of the model and improve the real-time performance; a hybrid domain attention mechanism module EPA is proposed, which enables the algorithm to focus on important channels more quickly and effectively through a local cross-channel interaction strategy without dimensionality reduction. Suppressing invalid channels and combining the channel attention mechanism with the spatial attention mechanism makes the algorithm pay more attention to the pixel information related to the target. The Residual Dense Attention Module (RDAB) is proposed, which is composed of dense residual blocks and attention mechanism EPA. It extracts sufficient local features through dense convolutional layers, and obtains more effective channel and pixel information through attention mechanism, which can make the algorithm obtain better detection effect. Detect and identify the small-size infrared vehicle target data after data augmentation, and compare experiments with a variety of typical algorithms. It can be seen from the experimental results that the detection and recognition effect of the JH-YOLOv5-RDAB network proposed in this paper is better than other networks, and the weight size is only 6.6 MB, which is only half of the weight of the YOLOv5s algorithm model, but the algorithm detection effect is better, and the detection effect of the algorithm is close YOLOv5l whose weight size is 93.7 MB, with mAP50 reaching 95.1%. The experimental results show the superiority and feasibility of this network in infrared dim vehicle target detection.

The active/passive imaging system has two imaging modes, with high integration, low cost, high system operation efficiency and good application prospect. A 64×64 multifunctional infrared focal plane array (FPA) readout integrated circuit (ROIC) was presented. Under the limitation of 30 μm pixel center distance, four imaging functions had been realized on this ROIC: Daylight standard imaging, low light level imaging, asynchronous laser pulse detection and two-dimensional laser ranging. Based on the TSMC 0.35 μm process, the chip design, tape out and test verification of multifunctional ROIC were completed. The layout area was significantly reduced by using circuit reuse design and pixel sharing architecture. The T-switch of CTIA was adopted to effectively reduce the leakage current and to improve the dynamic range of infrared passive imaging circuit, which made the dynamic range up to 60 dB in high gain mode and 68 dB in low gain mode. And the well capacity reached 203 ke- in high gain mode and 1.63 Me- in low gain mode. Three-stage push-pull amplifier and MOS feedback resistor made RTIA have both high gain and small layout area. The test results show that the circuit has active/passive imaging functions and good performances. It can be applied to infrared FPA lidar imaging system.

The p-on-n HgCdTe infrared detector with As ion implantation is an important technology development route for high operating temperature devices, owing to long minority carrier life, low dark current, high R0A, etc. Focus on 640×512, 15 μm pitch mid-wavelength infrared HgCdTe focal plane arrays (FPA) devices prepared by As ion implantation and doping, and analysis the performance and dark current under different temperature. The results indicate that the FPA device shows high uniform responsivity and 99.98% operability under 80 K. The number of bad pixels increase with increasing of operating temperature, and the operability decreases to 99.92% and 99.32% under 150 K and 180 K, respectively. Owing to suppression of diffusion current, the dark currents of this device operating within 160-200 K are better than the Rule-07. In addition, for a 300 K background temperature, when working at 150-180 K, tthe device shows high signal-to-noise ratio, which shows the feasibility of high operating temperature detectors.

In order to meet the requirements of low background, low power consumption of low temperature optical system and high environmental adaptability of infrared detector refrigeration components, the design idea of the Dewar main body (window, window cap and enclosure) maintaining low temperature and flexible adiabatic connection with the cooling surface of the cryocooler expander is proposed. Aiming at the characteristics of the engineering application of the Dewar flexible shell for cryogenic optics, this paper takes a Dewar component of a long-wavelength 12.5 μm 2 000 element infrared detector for cryogenic optics as an example. This paper proposes a bellows as a flexible shell for adiabatic connection. The design of thermal insulation, mechanics and associated heat leakage of Dewar flexible bellows is highlighted. The thermal characteristics of bellows under different thermal load conditions are verified, and the minimum temperature gradient is 37.22 K, the adiabatic thermal resistance is 1142 K/W, and the error is 37%. In order to comprehensively evaluate the performance of the flexible shell structure, the thermal vacuum and qualification-level mechanical tests are carried out for a long-wavelength 12.5 μm 2 000 element detector flexible shell Dewar component for cryogenic optics. The test results show that when the low temperature window works at 200 K, the detector works at 60 K, the heat leakage of the Dewar is 544 mW. Compared with the normal temperature condition, the power consumption of the cryocooler is reduced by 53% when working in low temperature condition,, and the 4 g random mechanical test is passed, which verifies the low temperature optics. It is reasonable and feasible to use the Dewar flexible bellows shell model, which provides an important reference for the subsequent structural engineering application of the Dewar flexible shell for cryogenic optics.

As an infrared standard source, surface blackbody is widely used in infrared temperature measurement, infrared imaging, infrared camera calibration and other fields. The infrared radiation performance of infrared standard source mainly depends on the control of surface blackbody temperature field. In order to meet the development needs of large aperture and large field of view of spaceborne and airborne infrared detectors, the temperature control technology of extra large surface blackbody is studied in this paper. Under the condition of outfield, the difficulty of temperature control increases with the increase of surface blackbody size. The temperature control system adopts the two-phase fluid loop technology to realize the high temperature uniformity and stability temperature control of a 3 m×3 m surface blackbody for the outfield field under different target temperatures. The experiment results show that the surface temperature uniformity control of the black body is better than ±0.60 ℃ and the stability control is better than 0.14 ℃/15 min.

In order to meet the needs of on-orbit radiometric calibration of remote sensors, an infrared channel field radiometer (ICFR) was developed for on-site measurement. The working principle, optical system design and mechanical structure design of ICFR were expounded, and the radiometric calibration and calibration uncertainty analysis of ICFR laboratory were carried out, the results showed that the received radiance of each ICFR channel had a high linear relationship with the response DN value, and the radiometric calibration uncertainty was better than 0.16 K. The ICFR thermal shock resistance and working environment temperature adaptability tests were carried out. The results showed that ICFR had strong thermal shock resistance and could be applied to the working environment of -20-50 ℃. In order to verify the accuracy of ICFR measurement data and the reliability of the instrument, the field comparison experiment of ICFR and CE312 were carried out in the National High-Resolution Remote Sensing Comprehensive Calibration Field. The results showed that the surface brightness temperature measured by the two devices had the same change trend, the average brightness temperature deviation measured by the corresponding channels of the two was less than 0.1 K, and the standard deviation was less than 0.3 K, which verified that ICFR had measurement accuracy and stability similar to CE312, and had important applications in remote sensor thermal infrared band site calibration.

Noise equivalent spectral radiance (NESR) is a significant index representing the ultimate detection capability of infrared remote sensors. NESR calibration of highly sensitive infrared remote sensor requires an infrared radiation source with high stability, high uniformity and full field of view, and the uncertainty of its spectral radiance should be significantly lower than that of NESR of infrared remote sensor. Aiming at a new large aperture cascade integrating sphere NESR calibration system, this paper carried out experimental testing and research on the calibration uncertainty of NESR, and evaluated the influence of 11 uncertainty factors, such as the magnitude traceability of absolute spectral radiance, the uniformity and stability of integrating sphere output. The test results show that the relative uncertainty of the spectral radiance of the primary integrating sphere is better than 0.34% within the specified brightness temperature range of 303-308 K; the NESR calibration uncertainty is better than 0.1-0.0037 μW·cm-2·sr-1·μm-1 within the wavelength range of 6-15 μm, which verifies the feasibility of applying the new calibration system to the NESR calibration of high-performance infrared remote sensor.

Infrared detection technology plays a key role in many important fields, such as satellite reconnaissance, military guidance, astronomical observation, medical detection, and modern communications. Type-II superlattices, as a new generation of infrared detection materials after HgCdTe detectors, have unique advantages in terms of stability, manufacturability, and cost. The barrier-type InAs/InAsSb type-II superlattice infrared detectors are one of the most promising type-II superlattice infrared detectors. Their key performance has been steadily improved in recent years but is still constrained by factors such as low absorption coefficient, difficult heteroepitaxial growth, and large dark current. Herein, this article reviews the development history of III-V type-II superlattices, analyzes the different barrier structures, key properties and development trends of barrier-type InAs/InAsSb type-II superlattice infrared detectors, and points out the potential key problems and future development directions of barrier type InAs/InAsSb type-II superlattice infrared detectors.

A new method to improve the height measurement accuracy of the integrated navigation system of one-dimensional laser Doppler velocimeter (LDV) and single-axis rotation inertial navigation system (INS) is explored in this paper. The attitude output after base tilt compensation of the single-axis rotation INS is used to provide a high-precision attitude reference for the LDV. The height measurement principle of the one-dimensional LDV with dual-beam differential structure is studied, and the base tilt compensation method of single-axis rotation INS is analyzed. On the basis of theoretical analysis, on-vehicle experiments are carried out to verify the effectiveness of the designed height measurement method. Two groups of 35-40 min on-vehicle tests are completed. The maximum error of height measurement in the first group is -2.67 m, and the standard deviation is 1.0094 m; The maximum error of the second group of height measurement is 1.68 m, and the standard deviation is 0.5880 m, reaching the expected target that the continuous dynamic height measurement accuracy is better than 3 m under the vehicle condition. The related research proves the effectiveness of the height measurement method based on integrated navigation system of single-axis rotation INS and one-dimensional LDV.

With higher demand and technological development to promote the working speed of aerial vehicles, the mobility and flexibility of aerial optical imaging have become more prominent, but the technical difficulty of achieving high-quality, high-resolution imaging is also extremely challenging. The complex interaction between aircraft and high-speed airflow produces aero-optical effects, and light waves or beams are subject to strong interference when passing through complex flow fields and optical windows, which has attracted many scientists to carry out multidisciplinary cross-fertilization of related research work, and a large number of research results have been achieved, providing strong support for experimental testing and engineering practice. In this paper, starting from the calculation of aero-optical flow field and optical window, the research progress of aero-optical transmission effect is reviewed in detail, the corresponding calculation methods are summarized, and the thinking and suggestions of aero-optical transmission effect calculation for aerial optical imaging are given based on the current technological development trend.

The optical resonant cavity can not only enhance the interaction between the laser and matter, but also suppress the noise of the laser, which is an important tool for research on precision measurement, quantum optics, etc. Stable locking of laser and optical resonant cavity resonance is the key to its application. However, the locking effect will be affected by factors such as mechanical vibration, temperature changes, etc in the actual environment. The fuzzy algorithm is applied to the PDH (Pound-Drever-Hall) technology, so that the three parameters of the proportional-integral-differential controller can be adjusted according to the changes of the external environment to obtain the optimal parameters in real time, which effectively improves anti-interference ability of optical resonator locking. If outside interference is still so great that the lock is lost, the system can make it re-lock automatically. The system effectively improves the practicality of the optical resonator, and provides a technical basis for the application of the optical resonator in precision measurement and quantum optics experiments.

The laser cleaning has some advantages as non-pollution, safety and controllability, which has significant applications in aerospace, electronic field and transportation. The nanosecond pulsed laser was used to clean TB06-9 coating on the surface of aviation 2A12 aluminum alloy. A novel two-step nondestructive laser cleaning process was developed. Scanning electron microscope, energy dispersive spectrometer, ultra depth of field three-dimensional microscope and universal electronic testing machine are applied to investigate laser cleaning coating. The results show that, the first step is to use a laser cleaning, with the increase of the power, the coating on the sample surface decreases gradually, and the oxide layer and substrate are exposed. When the laser power is 40 W, the oxide layer is well preserved. When the laser power is increased to 45 W, the oxide layer begins to be damaged, with increase of the laser power, the damage of oxide layer gradually increased. The optimization parameters of the first step are the laser frequency of 20 kHz, power of 40 W, scanning speed of 1 040 mm/s and line spacing of 0.052 mm respectively. The second step is to carry out multiple cleaning based on the first step. The second parameters are laser frequency of 1000 kHz, power of 80 W, scanning speed of 690 mm/s, line spacing of 0.034 5 mm respectively. The surface morphology of sample by two-step laser cleanning samples is similar to that of the original samples, and the surface microhardness and tensile strength of the samples remain consistent. The mechanical properties of the material are well maintained.

The effects of water-based and water film assisted methods on the hole quality of femtosecond laser layered-ring trepanning on superalloy was studied. The influence of the laser pulse repetition rate on the hole entrance/exit diameter, taper angle, hole sidewall morphology and hole sidewall roughness under different water assisted methods were compared and analyzed. The results shown that both water-based and water film assistance could improve the quality of femtosecond laser drilling, reduced the hole taper angle and the sidewall roughness, and the improvement effect of water-based assistance was more obvious. When the laser pulse energy was 80 μJ and the pulse repetition rate was 100 kHz, the quality of hole sidewall was better with water-based assistance, and the taper of the hole was reduced by 18.04% compared with that in air. With the increase of laser pulse repetition rate, the hole entrance/exit diameter and taper angle decreased firstly and then increased under the two water-assisted conditions, the changes of hole sidewall roughness were not obvious with water-based assistance, but the hole sidewall roughness with water film assistance increased continuously. The experimental results provided a reference for optimizing the water-assisted femtosecond laser drilling.

The design and fabrication of a fixed-tuned 320-360 GHz sub-harmonic mixer, featuring a newly developed small anode junction anti-parallel pair of planar Schottky diodes chip, are presented. A traditional E-plane split-block waveguide architecture was adopted in the mixer's design: the diodes chip was flip-chipped onto a quartz-based microstrip circuit and suspendedly glued to the bottom half of an equally split waveguide block with silver epoxy. A method of combination of field and circuit was applied to simulate and optimize the performance of the mixing circuit. Every functioning part of the mixing circuit was calculated with field simulating software to create its own S-parameters package, which was then combined with the diodes' barriers to be used by nonlinear circuit simulating software to simulate and optimize the performance of the mixer. The final test indicates that the ndicates that the mixer's double side band (DSB) conversion losses were lower than 9 dB, over 12% of bandwidth (320-360 GHz), with 4-6 mW of local oscillator (LO) power input; and at room temperature a minimum DSB equivalent noise temperature of 780 K was measured for RF frequency between 310 GHz and 340 GHz.

Due to the problem of hardware architecture, the range gating module of the existing mobile satellite laser ranging system has some shortcomings, such as low stability and low reliability. Since it is incompatible with the equipment of the fixed station, it is necessary to develop a new range gating module to improve the operation stability while giving consideration to high integration. Based on the realization principle of range gating and backscattering avoidance, the new range gating module is designed with ARM and FPGA embedded dual core architecture. The module used the ephemeris of lageos1, ajisai and geosynchronous compassi3 satellites to fit the range gating parameters. The test results show that the parameter fitting error of the range gating module is less than 0.01%, and the calculation time of a single expected echo epoch is 34.365 μs at repetition rate of 2 kHz. The average firing frequency loss rate due to the backscattering avoidance is less than 1%. The resolution of range gating is lower than 5 ns at repetition rate of 2 kHz. The output of high frequency gating signal is stable and the module can meet the requirements of repetition frequency applications over 20 kHz. It conforms to the expected results and has practical application value.

FMCW LiDAR is being widely studied for its high accuracy, strong anti-interference capability and simultaneous ranging and speed measurement. The inherent fence effect of FFT will introduce errors in ranging and speed measurement. To solve this problem, firstly, this paper analyzes the law of spectrum amplitude and phase angle, and then combines with the principle of sine function, proposes a modified Rife algorithm that is easy to implement in hardware. When the estimated frequency is close to the FFT quantization frequency point, this method can effectively reduce the error of the Rife algorithm. The simulation and FPGA verification results show that when the SNR is -10 dB, the mean error (ME) and root mean square error (RMSE) of the algorithm are reduced by 69.6% and 50.7%, respectively, compared with the traditional Rife algorithm. The calculation amount is only increased by two multiplications and additions, which is negligible compared to N-point FFT computation. Finally, in order to verify the effectiveness of the algorithm, this paper build an optical test platform to simulate the intermediate frequency echo signal of LiDAR. The results show that the algorithm can achieve simultaneous ranging and speed measurement within 112 m. The ranging error is no more than 5 cm, and the speed measurement error is no more than 0.16 km/h. The algorithm meets the demand of real-time ranging and speed measurement.

Femtosecond laser pulses are widely used in many fields due to their narrow pulse width and high peak power. The dispersion-managed fiber mode-locked laser has higher pulse energy, wider spectrum and narrower pulse due to its unique in-cavity breathing mechanism. The fiber mode-locked laser using chirped Bragg grating for dispersion management can realize the real all-fiber structure and improve the compactness and stability of the laser. Therefore, the fiber mode-locked laser using chirped Bragg grating for dispersion management has more practical significance. The effects of different distribution of single-mode fiber in ytterbium-doped fiber mode-locked laser based on chirped fiber Bragg grating on pulse dynamics and output pulse parameters are studied by numerical simulation. The influence of the distribution of single-mode fiber on the dynamic process of pulse in the cavity is analyzed when the net dispersion is different. The simulation results show that when the net cavity dispersion is negative, the shorter the single-mode fiber between the chirped fiber Bragg grating and the gain fiber, the higher the pumping threshold and the wider the output spectrum of the fiber laser can maintain the stable monopulsing operation, so that the narrow pulse width can be obtained. When the net cavity dispersion is close to zero, the effect of the length of single mode fiber between the chirped fiber Bragg grating and the gain fiber on the output pulse parameters is more significant. When the net cavity dispersion is positive, the influence of the single mode fiber distribution in the cavity on the output pulse gradually weakens, and the performance of the mode-locked laser is not significantly improved by optimizing the single-mode fiber distribution. Finally, an optimization method is proposed to improve the output performance of the laser by changing the distribution of single mode fiber in the cavity.

In recent years, coherent detection lidar is an effective means to measure long-range low-altitude wind shear. 1.6 μm solid-state lasers have become the main light source for coherent radar with the advantages of human eye safety and mature detector devices. Its gain medium Er:YAG crystal had a strong absorption peak in the 1532 nm band, but the absorption spectrum was narrow, so the crystal output efficiency can be effectively improved by resonant pumping using a 1532 nm fiber laser. To this end, an all-fiber 1532 nm laser output was achieved with an Er/Yb double-clad fiber as the gain medium, a 1532 nm fiber grating as the reflective cavity mirror and a 976 nm semiconductor laser as the pumping source. The output laser had a maximum power of 73.44 W, a tunable wavelength range of 1531.35-1532.14 nm, a wavelength spectral width of 0.06 nm, and the beam quality M2 of 1.38 and 1.26 in xand y direction, which was an ideal pumping source for 1.6 μm solid-state lasers. The laser was used to pump Er: YAG nonplanar ring cavity to obtain 1.3 W single frequency laser output, and the slope efficiency was 31.76%.

Ethanol is a macromolecular volatile organic compound (VOC) with broadband absorption characteristics, which is always disturbed by the air background absorption for remote sensing. In this paper, it was proposed that a novel differential absorption spectroscopy for stand-off detection of VOCs with broadband absorption, in which accurately measured the interference spectrum and used as internal standard to correct the possible baseline offset and nonlinearity in the spectrometer. The method has been successfully applied to stand-off detection of gaseous ethanol. An open-air experimental system was constructed with a DFB diode laser under laboratory conditions for the near-infrared characteristic absorption (7180 cm-1) of ethanol. The results showed that the measurement error of ethanol concentration was less than 3.5 ppm, and the detection limit of 2.6 ppm with the integration time 15.1 s by Allan variance evaluation, which was nearly 2 orders of magnitude lower than the lowest detection limit reported at present. The proposed method laid a foundation of highly sensitive miniaturized optical system for VOCs stand-off detection.

Proton injection parameters have a great influence on the position of current confinement aperture and the effect of current isolation of the implantation vertical cavity surface emitting laser (VCSEL). From the influence rule and mechanism of the energy and dose of proton implantation and their interaction on the current confinement aperture of VCSEL, this paper analyzes the influence of implantation parameters on the proton distribution and the resistance value of the implanted region by theoretical simulation firstly. And then proton implantation experimental research were carried out using VCSEL epitaxial wafers on this basis. Both the experimental results and theoretical analysis show that the current isolation effect and proton distribution in the injection region are controlled by injection energy and dose. When the implantation parameters are 320 keV and 8×1014 cm-2, after annealing at 430 ℃ for 30 s, a proton implantation region can be obtained with a junction depth of about 0.7 μm, an average range of about 1.3 μm from the active region and a resistance value of 4.6×107 Ω∙cm2. The VCSEL device was fabricated by using this parameter, and better laser excitation was achieved. It is proved that the proton distribution can not only avoid the damage of VCSEL active region, but also achieve a excellent current isolation effect, meeting the fabrication requirements of the VCSEL current confinement aperture. The results of this study have important guiding significance for the chip structure and process optimization of proton-injected VCSELs.

Raman spectroscopy has been widely used in many fields due to its advantages of multi-component simultaneous detection and molecular fingerprinting characteristics, but its low detection sensitivity severely limits the further development. In order to improve the in-situ analysis capability of powder samples by Raman spectroscopy, a high-sensitivity optical fiber Raman probe based on quartz tube enhancement is proposed. The metal-coated hollow-core fiber is used for optical signal transmission, which effectively reduces the influence of background signal on Raman spectrum. The bottom of the probe is designed with a quartz tube, which increases the sampling volume and collection efficiency, it improves the detection sensitivity of Raman spectrum. Firstly, theoretical analysis of quartz tube Raman spectroscopy can improve the detection sensitivity of powder samples. Secondly, the design and implementation of the probe are introduced in detail. Lastly, the performance of the probe is further evaluated. The results show that the Raman signal intensity (NaHCO3) increased by a factor of 2.92 compared with the spherical lens Raman probe. In order to simulate practical application scenarios, the Raman spectral information of powder samples (Na2SO4 and NaHCO3) at different depths in the container is successfully obtained by using the fiber Raman probe. The quartz tube-enhanced Raman probe designed in this paper has the advantages of small outer diameter (only 2 mm) and high sensitivity. It can detect deep powder samples and provide a new way for in-situ analysis of powder samples on site.

Erbium-ytterbium co-doped phosphate glass planar waveguides have unique advantages in heat dissipation and nonlinear effect suppression. It can be developed as the gain medium of near-infrared 1.5 μm high average power solid lasers, which is of great significance. Erbium-ytterbium co-doped phosphate glass planar waveguides are fabricated by optical contacting and thermal bonding. The effect of pre-bonding step-temperature on bonding quality is studied. At the same time, the influence of bonding temperature and bonding time on the thickness of molecular diffusion layer at bonding interface is obtained by electron probe surface analysis (EPMA). According to Fick's second law, the diffusion mechanism of Yb3+ in core glass under one-dimensional equivalence hypothesis is discussed, and the molecular diffusion model of the solid-solid interface during bonding process is established. Finally, a high-quality sandwich structure planar waveguide with 100 μm core layer and bonding strength of 11.63 MPa is obtained by selecting optimal heat treatment temperature curve.

Remote sensing satellite structures are susceptible to thermal strain during in-orbit service due to extreme temperature changes in space and microgravity environment, which seriously affects the detection accuracy. However, the existing methods are difficult to achieve thermal strain monitoring in orbit. To solve this problem, a thermal strain fiber grating monitoring method with temperature decoupling function is proposed. The thermal strain of the structure is calculated and analyzed by numerical simulation, and the change of temperature and strain fields under overall and local thermal loading are obtained. A thermal strain fiber optic monitoring test system is designed and constructed, thermal loading fiber optic measurement test on satellite antenna structure specimens is conducted, the accuracy of structural thermal strain fiber optic monitoring is tested and analyzed, and the effectiveness of the method is verified. Research results show that in the temperature variation range of -120-120 ℃, the monitoring accuracy of temperature and thermal strain by fiber Bragg grating sensor and temperature decoupling method are 1.02% and 2.45%, respectively. The reconstruction errors of the structural temperature and strain fields are 3.24% and 6.61% under the action of local thermal loading from 30 ℃ to 100 ℃, respectively. The method has the prospect of application in satellite structure in-orbit health monitoring.

Different from the scalar vortex beam (SVB), the vector vortex beam (VVB) has both an anisotropic spatial polarization distribution and a spiral phase distribution, and carries the orbital angular momentum (OAM) related to the phase distribution. Based on the Collins diffraction theory, the OAM density under the paraxial approximation is obtained. The light field of the VVB passing through the aperture-lens system was collected experimentally. The effects of the aperture truncation parameters and the aperture-lens spacing on the light field and the OAM density of the VVB are discussed in detail. The OAM density characteristics of the VVB and the SVB through the aperture are compared. The results show that the OAM has a slower attenuation with the transmission distance after the VVB passes through the aperture-lens system and is less affected by the truncation parameters compared with the SVB. The polarization state of the VVB is not affected by the aperture-lens system. When the truncation parameter is greater than 4.2, the OAM density and light field are not affected by the truncation parameter. The OAM density reaches the maximum value at the focal position of the lens. The research results provide theoretical references for the application of OAM characteristics of VVBs.

Multi-view point cloud registration is one of the key steps in reverse engineering, which has important research significance and engineering application value. As for point cloud data obtained from narrow scenes (such as oral cavity or mechanical structure), the accuracy of the multi-view registration algorithm directly affects the accuracy of the reconstructed results. In order to improve the speed and robustness of multi-view registration for narrow scenes, an incremental multi-view point cloud registration method based on pose optimization is proposed. Firstly, a multi-strategy registration algorithm is proposed based on iterative closest point method (ICP) and feature-based registration method to solve the registration of adjacent point clouds. Then, based on the incremental registration of adjacent point clouds, a loop closure detection method based on distance constraints is proposed, and the pose graph is constructed according to the registration results of adjacent point clouds and loop closure detection results. Finally, the real-time optimization strategy is used to optimize the pose graph to alleviate drift errors and achieve robust multi-view registration. Experimental results show that the proposed multi-strategy registration algorithm and the loop closure detection method with distance constraints are effective. The classical ICP algorithm and the FPFH-based method are invalid in the experiment, but the proposed multi-strategy registration algorithm is valid. The loop closure detection method with distance constraints is more efficient than the conventional loop closure detection method. The multi-view registration algorithm proposed in this paper can achieve accuracy of 0.0357 mm in tooth model data registration. In order to verify the universality of the algorithm, the model point clouds collected continuously in multiple narrow scenes are used for verification. The results show that the proposed algorithm achieves good results, which indicates that the proposed method is an effective multi-view registration method for narrow scenes.

In order to solve the problem of high-precision surface shape detection of Φ2 m plane mirror and improve the reliability of the Ricky-Common detection method, a Φ2 m plane mirror surface shape detection technology based on unit excitation method and inverse complex calculation was studied. The influence of error sources such as airflow disturbance and spherical mirror surface shape on the calculation method of unit excitation surface shape was analyzed. The combination of unit excitation and optical software inverse complex calculation was used to improve the reliability of the Ricky-Commonn detection method. The effect of airflow change on surface shape recovery during the detection of Φ2 m plane mirror was simulated and analyzed. The results show that under the influence of airflow, the stability of surface shape calculation remains at 0.003λ after multiple average calculations. The surface shape calculation the accuracy reaches 0.0079λ under the influence of spherical mirror shape. Using this method, the surface shape processing process of the actual Φ2 m plane mirror was controlled, and the surface shape detection results showed that the RMS of the plane mirror reached 0.0415λ, and the PV was 0.2040λ (λ=632.8 nm). The purpose of this research is to solve the problem of shape detection of large-diameter plane mirrors under the influence of errors, which has important application significance for actual mirror processing and detection.

Banknote which is issued by the government and forced to use. In 2019, the People’s Bank of China issues the fifth set of RMB. The anti-fouling protection coating is used on both sides, which significantly improves the cleanliness of paper currency. In order to control the coating quality more reasonably, it is necessary to detect the coating thickness in the production. The coating thickness of this paper was to investigate, this paper establishes the optical diffuse reflection model of coating thickness with banknote pattern as a complex substrate surface, identifies and quantitatively detects the coated and uncoated banknote by using Fourier near-infrared spectrometer and confocal laser scanning microscopy system. In this paper, one analytical method based on the combination of multivariate scattering correction (MSC) and second-order derivative combination analysis is proposed for the near infrared (NIR) absorption spectrum data of the coating, that could be effectively identified in the NIR spectrum, and 4 346.764 cm-1 is determined as the characteristic wave number. Then, the coating thickness model is decoupled basing on the reflectance and roughness. Finally, the coating thickness changes of coated banknotes are detected by a confocal laser scanning microscopy system, and they are correlated with the decoupling result of the model to obtain the actual coating thickness. The final results show that the minimum is 3.807 μm, the maximum is 12.738 μm. The detection method has an important practical significance for coating quality control in banknote production.

The horizontal optical testing system with large aperture and long focal length is extremely susceptible to the airflow disturbance, which will cause random dynamic changes in time and space of multiple physical quantities in the optical path, such as temperature, velocity and pressure. In particular, the spatial heterogeneity and temporal stability of temperature will directly affect the dynamic change of air refractive index, resulting in the degradation of the point spread function, the tilt of the wavefront and the change of the wavefront over time. In order to suppress the influence of airflow disturbance on the testing optical path and improve the testing accuracy, based on the Computational Fluid Dynamics (CFD), a forced convection method was proposed to improve the uniformity of the indoor temperature field, which can be used to determine the array mode and number of fans. The Peak to Valley (PV) of the temperature was adopted and the concept of maximum optical path differences was introduced to comprehensively evaluate the uniformity of the indoor temperature field. Verified by several groups of experiments, the forced convection scheme reduces the standard deviation of the astigmatism coefficient from $0.146 \lambda $ to $ 0.026\;3 \lambda\;(\lambda=632.8\; \mathrm{nm}) $, which significantly improves the uniformity and stability of the indoor temperature field, greatly reduces the optical testing error, and improves the testing accuracy. It provides a reference for ensuring the optical testing accuracy of the optical testing system with long optical path and large aperture in the future.

The radial motion error is one of the most important errors of rotary axis, which seriously affects the precision and performance of CNC machine tools. Using laser interference with reference rotary axis can achieve measurement of radial motion error. Neither target or reference rotary axis is ideal, there are some restrictions like uneven speed, response delay and unstable tracking. These restrictions cause phase jitter and make the non-linear correction difficult. It will affect the phase calculation accuracy of the interference signal. In order to eliminate the influence of phase jitters, a type of signal processing method is proposed. The paper designs and builds a set of laser interference measuring device for measuring the radial motion error. Compared to the traditional correction method, the proposed method reduces the measurement repeatability from 4.8 μm to 0.2 μm, and the error compared with the standard instrument is decreased from 3.5 μm to 2 μm.

With the deepening of space security and application exploration, the target-detectability of space vehicle in near space has become a core issue of research. For some multi-dimensional information of target, such as shape, spectrum and motion characteristics, can be directly captured by optical imaging detection device, optical detection has become an important means of space imaging and target detection. Under the conditions of atmospheric density, pressure and atmospheric convection in near space, imaging quality and detection range of optical detection device installed in high-speed aircraft could be affected seriously. By using target detection model with three analysis elements (imaging system, atmospheric transmission system and target-background system) and the theory of aero-optical effect, evaluation equation of aero-optical effect for high speed flow field has been established, to analyze imaging performance of typical scenes such as earth and space background. A ground verification test of target detection in high speed flow field has also been designed. The experimental results show that it’s an effective way for detecting plume flow of high-speed space targets by using short wave infrared detector (SWIR: 900-1 700 nm) with quartz window (with thickness of more than 10 mm). Meanwhile, by reducing exposure time of camera, optimizing exposure control strategy and selecting optical filter, stray light in background and aero-optical effect can be effectively suppressed.

Due to the increasingly serious environmental pollution, it is necessary to trace the pollutants. The tracer Rhodamine B is an effective way to trace the source of pollutants. However, in the in-situ pollutant tracking and detection using Rhodamine B fluorescence sensor, the measurement results will be affected by environmental factors such as temperature and turbidity. Therefore, it is important that the accuracy of the in-situ detection of Rhodamine B is improved by compensating and correcting the two main environmental factors, temperature and turbidity. Fluorescence spectra of Rhodamine B with different concentrations were detected by fluorescence spectrophotometer, and partial least squares (PLS) method was used to analyze the spectral data and establish the standard curve. The fluorescence spectra of Rhodamine B were measured and analyzed in the range of temperature from 10 ℃ to 60 ℃ and turbidity from 0 NTU to 55 NTU. The results showed that the fluorescence intensity of Rhodamine B was negatively correlated with temperature and positively correlated with turbidity. Since the rate of change of Rhodamine B concentration difference has a good linear relationship with temperature and turbidity, the rate of change of Rhodamine B concentration difference is used for compensation correction in different environments. After temperature and turbidity compensation correction, the relative errors of concentration detection results were less than 0.48% and 0.34%, respectively, which improved the detection accuracy of Rhodamine B in different environments. What’s more, under the influence of temperature and turbidity, the detection results were analyzed, by doing so, a model of common compensation correction was established. It provides a correction method to suppress the interference of temperature and turbidity in-situ detection of Rhodamine B.

To address the problem that the accuracy of the line scan vision detection system is easily affected by the mechanical structure error and the specific influence mechanism is not clear, a mathematical model of the influence of mechanical error on the system imaging error was established and analyzed. Based on the theories of multi-system kinematics and homogeneous coordinate transformation, a mechanical system error transfer model of the line scan vision detection system was derived, and a system error comprehensive model was established with reference to the line scan imaging characteristics to clarify the correspondence between mechanical errors and system image output errors. The error sensitivity of the model was analyzed based on the complete differential-coefficient theory, and the error sources that had a great impact on the errors of the x andy dimensions of the output image were clarified. An experiment for verifying error sources is carried out and the result shows that the established system error comprehensive model can accurately identify the key error sources that have the greatest influence on the output image. The deviation between the numerical sensitivity prediction by the model and the actual value does not exceed 2.38%, which can achieve the accurate sensitivity prediction of the key error sources.

Brittle materials are usually used as raw materials for optical elements. Subsurface damage (SSD) is easily generated during the processing of brittle materials. SSD causes serious hazard to the manufacturing and application stage of brittle materials. In terms of manufacturing, SSD affects the selection and connection of processes, which is easy to cause problems such as excessive processing and lack of processing, and resulting in low processing efficiency. In terms of application, SSD affects key technical indicators such as imaging quality, stability, and service life of optical components. Comprehensive characterization and accurate measurement of SSD in optical components is critical for efficient, and high-quality removal of SSD. In this paper, the formation mechanism of SSD corresponding to different processing methods and the characterization methods of SSD are introduced firstly. Then the destructive and non-destructive SSD measurement methods are summarized. The principles, applicable materials, applicable processing stages, advantages and disadvantages of different measurement methods are introduced, respectively. The SSD prediction methods based on surface roughness and processing parameters are presented. Finally, the development trend of SSD measurement technology is prospected.

2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexazazoisowoodane (HNIW, CL-20) is a high-energy com- pound with a cage structure, which has broad application prospect in military and civil fields. In order to further understand the physical mechanism of the phase transition of CL-20 crystal, the absorption spectra in the temperature range of 23.0-179.8 ℃ are studied by using the terahertz time-domain spectroscopy (THz-TDS). The significant change of terahertz spectrum under thermal action indicated that the irreversible phase transition of CL-20 begins at 136.8 ℃. Combined with the results of solid-state density functional theory (DFT), the transition is identified as ε→γ-CL-20. Moreover, the analysis of the low-frequency vibration characteristics of CL-20 shows that the vibration modes of the molecular cage skeleton change significantly during the phase transition. The extensive van der Waals interactions between molecules are the source of this change. In addition, the evolution of the rotational vibration of the nitro group outside the framework is closely related to the molecular hydrogen bonding. This study provides a reference for further understanding the complex physical mechanism of CL-20 phase transition and detonation/deflagration under temperature loading. It is of great significance for the design and synthesis of high-quality explosives based on CL-20.

In order to take full advantage of the high electron mobility of the AlGaN/GaN high-electron-mobility transistor (HEMT) terahertz detector array, the detection characteristics of the HEMT terahertz detector array at 77 K are studied. A low temperature system suitable for the focal-plane array (FPA) chip is built based on liquid nitrogen Dewar. Comparison tests of the FPA at room temperature and low temperature is realized. When the temperature is lowered from 300 K to 77 K, the average responsivity of the detector array pixels increase by about 3 times, the average noise increases slightly, and the average noise-equivalent power (NEP) is reduced from 45.1 pW/Hz1/2 to 19.4 pW/Hz1/2 at 340 GHz, i.e., the sensitivity is more than doubled. Compared with the single detector coupled with silicon lens, there is still a lot of room for improving the sensitivity of array pixels. It is mainly due to the inconsistency of the optimal working voltage of each pixel, that leads to a large dispersion of the responsivity and noise between pixels under a given unified working voltage. Possible solutions to the problem of inconsistent optimal working voltage are discussed in this paper.