Single photon detection technology has become an important development direction in the field of 3D imaging because of its high sensitivity and high time resolution. APD single photon detection data is 0-1 data representing photon pulse events, which usually needs to be accumulated many times to achieve 3D imaging of the target. While the rotating object cannot be directly accumulated due to its motion. In order to solve the problem of three-dimensional reconstruction of rotating objects, a single photon 3D reconstruction method based on the definition of maximum intensity map was proposed. Firstly, the 3D reconstruction model of rotating objects was established, and then the likelihood estimation model of rotation velocity was established. Finally, the maximum definition of intensity map was taken as the cost function to solve the rotation velocity and reconstruct it. The computer simulation simulated the single photon 3D imaging detection data of the rotating cross object, the 3D reconstruction algorithm was used to achieve the high precision 3D reconstruction of the rotating object, and the simulation verification at different speeds was performed. The simulation results show that the speed estimation error is better than 5% and the depth reconstruction error is better than 0.1 m at different speeds, which verifies the correctness of the reconstruction algorithm.

Structured light technology is a non-contact three-dimensional optical imaging technology, which can restore the three-dimensional feature information of the object by measuring the deformation of the projection pattern on the surface of the object. However, the existing structured light system designing scheme has the problems of complex algorithm and low frame rate. In order to solve these problems, a temporal coded structured light system based on event-based camera sensor was proposed. The digital light projector (DLP) was used to project the temporal alternating light and dark coding patterns, and the event-based camera sensor was used for the high-speed acquisition. By encoding the time series of the projected speckle patterns, the speckle search method could be used instead of the complex spatial matching, thereby reducing the algorithm complexity of the structured light system. By analyzing the correspondence of scattered spots, the three-dimensional information of the surface of the space object was finally restored. After experimental verification, it is show that the acquisition frame rate of the proposed system can reach 66.7 frame/s. Compared with other traditional schemes, the complexity of the algorithm is significantly reduced, and the measurement accuracy can reach the millimeter level. Experimental results show that the designed temporal coded structured light system can perform three-dimensional reconstruction of actual scenes with high speed and low computation cost.

In order to obtain wide-field and clear image of the epidural space, the disposable epidural space endoscopic optical system was designed using Q-type aspherical surface. The operating band was visible light, the field of view was 90°, the F-number was 4, and the receiver was a 1/18 inch CMOS sensor. The system was composed of three plastic lenses and one cover glass, and the third lens adopted Q-type aspherical surface. Therefore, the structure was simple, compact and low cost. The image quality evaluation results show that the modulation transfer function of each field of view is greater than 0.27 at the Nyquist frequency of 200 lp/mm, which is close to the diffraction limit. The root-mean-square radius of each field is less than the pixel size of 2.5 μm, and all are within the Airy spot range. The maximum residual distortion is less than 20%, which meets the requirement of high image quality. Finally, the ghost image of the system was analyzed and evaded. It is shown that the energy of the spot formed by the pupil ghost image is diffused, which has little influence on the uniformity of image illuminance. The spot size of the focal ghost image is much larger than the spot diagram of the main image, which has little impact on the imaging quality and meets the imaging requirements.

To realize high efficiency absorption of ultra-wide optical spectrum radiation from ultraviolet to infrared, it was designed that 0.2 μm~20 μm optical metamaterial absorption structure with high efficiency absorption. It was designed by the method of ultra-wide band partition set, 5 separate layers optimal design and non uniform sampling to get the parameters of equivalent resonant circuit of 3 scale 5 separate layers metamaterial absorption structure, and the structure parameters of each layer was obtained and the absorption property was analyzed and discussed. Simulation experimental results show that, the total thickness of metamaterial absorption structure is about 3.14 μm, the absorption efficiency is better than 89% in 0.2 μm~20 μm wavelength range, and the absorption bandwidth ratio is near 100%, which can satisfy the constrain requirement of frequency range and absorption efficiency. This method can realize coherent and continuous absorption structure design in ultra-wide band frequency range, with absorption band expanding 45.26% in each partition and with total absorption band expanding 81.57% more than expected, the absorption bandwidth ratio is about 85.11%, that absorption efficiency is better than 80%. It can be applied in ultra-wide spectrum detection and confrontation stealth.

In order to meet the actual needs of minimally invasive medical surgery, the Zemax software was used to design a medical endoscope for the treatment of urinary system diseases, which could not only solved the problem of the excessive diameter of traditional ureteroscopes, but also retained the high resolution of the visual system. The light wedge was used to convert the light, and passed through the fiber transmission beam in a rigid endoscope. The final designed endoscope system has an F number of 4.5, a system object field of view of 80°, a viewing angle of 6°, a circle diameter of fiber transmission beam of 0.85 mm, an optical lens diameter of less than 1mm, a working distance of 6 mm, and a working length of 430 mm. The modulation transfer function (MTF) is greater than 0.2 at 120 lp/mm, and the imaging quality meets the visual requirement.

In the process of laser heat fusion sealing of a single glass tube, the quality of processing is inextricably linked to the temperature distribution inside the tube. Under the consideration of surface heat radiation, internal heat conduction of material and air heat convection, the finite element simulation software, which called COMSOL Multiphysics was adopted to carry out simulation of the temperature field of high borosilicate glass tube under the action of CO2 laser, the change rule of the temperature field distribution with time was analyzed, and the effects of laser power, laser spot radius and rotation speed on the temperature distribution of the glass tube were compared. Simulation results show that the higher the laser power, the smaller the spot radius, the lower the rotational speed of the glass tube, and the higher the temperature of the glass tube. According to the simulation results, the process requirements of laser processing of high borosilicate glass tube can be achieved by selecting suitable processing parameters. This study provides an important theoretical basis for the selection of process parameters of subsequent glass tube laser hot fusion sealing.

Autonomous reconnaissance is an automatic and intelligent reconnaissance mode of UAV-borne photoelectric payload. Parameter calculation is the premise of autonomous reconnaissance application. The autonomous reconnaissance mode of UAV-borne photoelectric payload was first introduced, then the flight speed and altitude of autonomous UAV cruise, the sensor field angle of view, pitch angle, scan speed and scan angle of photoelectric payload were calculated, the physical meaning and relationship of each parameter were analyzed, and the influence of each parameter on target recognition rate and recon time was analyzed. Finally, simulation calculation and analysis were carried out with examples, and the existing problems in practical application were pointed out, which provided a theoretical basis for practical application of this mode.

Considering the difficulty in obtaining real paired training data for low-light image enhancement and existing methods rarely consider both upstream and downstream visual tasks when developing algorithms, a progressive unsupervised image enhancement method focusing on value aware was designed, which employed a joint loss function with multiple constraints to get rid of paired datasets during the training stage. With the help of the proposed value aware parameter estimation network, the feature extraction could be achieved with only 0.035 M parameters. To enhance the nonlinear adjustment capability and reduce the number of iterations, a high-order nonlinear mapping curve was designed. To verify the effectiveness of the proposed method, the qualitative and quantitative experiments were conducted on an authoritative dataset widely used in the field of image enhancement, indicating that the proposed method outperformed the existing solutions. In addition, the UAV nighttime object tracking was evaluated as a typical downstream visual perception task. The results on the authoritative evaluation benchmark demonstrate the proposed method can significantly improve the performance of the existing tracker in the night scene, with accuracy and success rate gains of 21.50% and 32.23%, respectively. Extensive experiments show that the proposed method can significantly improve the visual effects of low-light images while also effectively alleviate the performance degradation of downstream vision algorithms caused by insufficient illumination in night scenarios.

When actually applying the detection model, due to the difference between the real scene and the training data set, the effect of the detection algorithm is greatly affected. In order to obtain the better detection effect in the target scene, it is usually necessary to collect and label data and then train, which is not only costly but also complicated. The proposed global-instance domain adaptation detection algorithm and system based on the attention mechanism only needed to collect part of the real scene data to perform transfer learning, realizing rapid model training and remote deployment of edge-cloud integration. In this domain adaptation detection algorithm, the global feature adversarial learning algorithm based on the attention mechanism could reduce the negative effect of background features in transfer learning; the instance-level feature alignment method based on dictionary learning could align instance-level features with high precision. After experimental comparison, the proposed method reached a level close to SOTA(state-of-the-art), and the ablation experiment was quantitatively proved the improvement of the domain adaptation detection effect of this method. The proposed domain adaptation detection technology is combined with an edge system with data transmission links, improving the detection effect by nearly 10 points in actual scenarios.

For the problem of low spatial resolution of light field images captured by light field cameras, a super-resolution method for light field images based on sub-pixel and gradient guide was proposed. A multiple sub-pixel information extraction module was designed, which divided the sub-aperture images into four image stacks: horizontal, vertical, diagonal and anti-diagonal, and extracted the sub-pixel information of each image stack separately. Meanwhile, considering that the gradient prior could provide effective clues for predicting high-frequency details, the gradient multiple sub-pixel information of the sub-aperture images was fused in the reconstruction process. Experimental results on five publicly available databases show that the proposed method not only generally outperforms the existing methods in terms of objective indexes, but also has better performance in the subjective visual effect, which the edge texture details are clearer.

Phase-coding method has been widely used for absolute phase retrieval in fringe projection profilometry (FPP). However, the robustness and the accuracy is severely affected by the gamma nonlinearity of FPP system. The wrapped phase extracted from distorted fringe patterns will deviate from the actual phase, which cannot be directly employed to retrieve the absolute phase. To address this problem, a robust phase-coding method based on an effective nonlinear correction strategy was proposed. First, the distorted wrapped phase could be adjusted by the phase histogram equalization (PHE) method to obtain the corrected wrapped phase. Theoretical studies demonstrated that the frequency of the nonlinear phase error is thrice that of the ideal phase. Therefore, the nonlinear phase error was further reduced by shifted-phase histogram equalization (SHE) method. Then, the continuous function was fitted by the Hermite interpolation algorithm, which could reduce the discretization error introduced by the SHE method. Both the simulation and experimental results show that the proposed method is more robust than the traditional method under gamma nonlinearity.

To solve the low accuracy of target detection caused by low contrast, insufficient features, and unclear details in complex infrared scenes, an improved infrared dim target detection method based on YOLOv5s model was proposed by creating a two-way convolution and Concat (TCC) module and introducing the Huawei Ghost module. Firstly, combining the low-level semantic features of infrared images, a TCC module was created using two convolution and multi-scale thought, which improved the comprehensiveness of feature extraction. Then, to simplify the network structure and reduce the number of parameters, a lightweight Ghost module was introduced to improve the SPP pooling layer and CSP2 convolutional network. Finally, using unmanned aerial vehicles (UAVs) as experimental objects, a dataset of infrared dim targets was constructed under various meteorological conditions during day and night, verifying validity of the improved algorithm. The results show that the detection accuracy of the improved YOLOv5s model is increased by 1.34%, and the mean average precision (mAP) is increased by 2.26%, which is superior to YOLOv4-tiny and YOLOv7-tiny models. It has the same accuracy as YOLOv8s model, but the number of model parameters is only 53% of the YOLOv8s model, which fully meets the needs of embedded device deployment.

Point cloud segmentation is crucial for key tasks, including intelligent driving, object recognition and detection, as well as reverse engineering. PointNet represents a direct point cloud data processing approach widely utilized in point cloud segmentation tasks. Nevertheless, it is associated with low segmentation accuracy and the computational cost of PointNet++ is high. Aiming at the above problems, an algorithm combining DenseNet and PointNet was proposed for the segmentation of point clouds. A three-branch hybrid attention mechanism was introduced to enhance PointNet capability to extract local features. DenseNet-STN and DenseNet-MLP structures were proposed to substitute spatial transformation networks (STNs) and multi-layer perceptrons (MLPs) in PointNet, in line with the dense connected convolutional networks (DenseNet) concept. At the same time, the add connection in DenseBlock, rather than the Concat connection, to enhance the accuracy of point feature correlation, without imposing significant complexity to the model. DenseNet-PointNet demonstrates effective generalization ability for complex classification problems and facilitates better function approximation, thereby improving the precision of point cloud segmentation. The findings of the effectiveness and ablation experiments show that the proposed algorithm performs well. The results of the point cloud segmentation experiments indicate that the intersection and concatenation ratio (IoU) of DenseNet-PointNet is superior to that of PointNet in most categories, and also higher than that of PointNet++ in some categories. DenseNet-PointNet achieves this with only 47.6% of the parameters of PointNet++, and 49.1% of the floating point operations (FLOPs). Therefore, these experimental results confirm the feasibility and availability of DenseNet-PointNet.

Electron bombarded active pixel sensor (EBAPS) is a new type of vacuum solid hybrid low light night vision device, and the modulation transfer function (MTF), as one of the performance parameters of EBAPS, can reflect the transmission ability of imaging systems to different frequency components. However, there is currently a lack of corresponding testing methods in China. Therefore, in order to characterize and evaluate the imaging quality of EBAPS, a MTF testing system for EBAPS was designed and built based on the principle of image intensifier slit method for testing MTF. By driving the EBAPS device and using a USB interface to transmit the collected data to the upper computer for image analysis, the slit image was processed to obtain the line spread function (LSF), and the corresponding modulation transfer function curve was obtained through discrete Fourier transform. When the illumination at the slit target was 2×10?2 lx, within a certain range, as the voltage increased, the MTF of EBAPS first increased and then decreased, and reached its maximum value when ?1 000 V was applied. In the light imaging mode, by fine-tuning the relative position between the slit and the sensor imaging surface, the standard deviation of MTF values for several important frequency points obtained from 5 consecutive tests was less than 0.01, indicating good stability.

Medical fiber endoscopes have been applied in various medical fields, and the overall light effect level of fiber endoscopes can affect the quality of the received images, leading to medical staff being unable to accurately judge the condition of the lesion. To quickly and effectively evaluate the comprehensive mirror body light effect of fiber endoscopes in clinical use, an automatic detection method based on image processing was proposed. The high reflectivity standard whiteboard was illuminated by the endoscope light source, and the endoscope images collected by the CCD camera were processed. The ratio of the gray values at 90% of the field of view to the center of the field of view was extracted as the comprehensive body light effect of each edge point, and the overall comprehensive body light effect of the endoscope was further calculated. According to the design method, 10 sets of repeated experiments were conducted on 2 fiber endoscopes, and compared with trademark values of the manufacturer. At the same time, the uncertainty was calculated and the source of error was analyzed, verifying the feasibility of the designed method.

Fused deposition modeling (FDM) is a hot working process, the research on temperature and motion accuracy in the printing process are independent directions, and the shape of the high temperature filament in the infrared image is usually not concerned, making it impossible to detect the operating status and temperature of the printer at the same time. An FDM printing trajectory measurement and quality evaluation method based on infrared imaging was proposed. The method adopted infrared camera to continuously monitor the FDM printing process, and established the pose solution model of the printer coordinate system and the camera world coordinate system, as well as the global camera motion pose solution model matching the infrared features between dynamic frames. The real time measurement of the running position of the end nozzle was realized, and the accurate print trajectory information was obtained. On this basis, the object image mapping relationship between the spatial print trajectory and the high temperature filament in the infrared image was established, and the quality of the printing process and typical defects were evaluated in the image domain. The average time of image processing was 25.9 ms, and the reprojection error of infrared camera posture measurement was 0.7 pixel. Under normal printing conditions, the average IoU between the ideal print trajectory calculated by the system and the high temperature region in the infrared image is 0.61. The experimental results show that the proposed method can accurately identify the typical problems such as model dislocation and abnormal extruding in the printing process, which provides a new solution for the related research of online print quality evaluation.

In order to reduce the influence of vibration on phase-shifting interferometry, the spectrum analysis of the vibration signal was carried out to separate the spectrum signal that contributed to the low-frequency vibration, which verified the fact that the phase-shifting interferometry (PSI) algorithm was more sensitive to vibration at 2 times the phase-shifting frequency. According to the standard PSI measurement steps and Newton's generalized binomial theorem, the multi-frequency vibration influence factor γ was derived. The phase error calculated by the standard PSI algorithm and the phase error after the multi-frequency vibration influence factor γ processing were simulated by Matlab software, and the experiment was carried out to verify it. The results show that the RMS value and phase error of the wavefront processed by the γ influence factor are lower than those of the PSI algorithm. The RMS value can be reduced by 22 times and the phase error can be reduced by 20 times.

In the development and application of aeroengine, the research on temperature measurement technology is of great significance. Due to its harsh working environment and narrow installation space, the accurate, efficient and high temperature resistant test methods are very limited, and new temperature measurement technologies are urgently needed. In recent years, sapphire fiber is the mainstream material for high temperature testing. Therefore, several temperature measurement technologies based on sapphire fiber were introduced from temperature test requirements. Including fiber grating temperature measurement technology, fiber Fabry-Perot temperature measurement technology, blackbody radiation temperature measurement technology, and fiber ultrasonic temperature measurement technology. The testing principles, systems, advantages and disadvantages of these technologies were emphasized, and the feasibility of application in aeroengines was analyzed. Finally, the future research direction of sapphire fiber temperature measurement technology was prospected, which laid a foundation for subsequent research and application.

Aluminum mirrors are widely used in aerospace and space remote sensing satellites. In order to improve the lightweight rate of aluminum mirrors and reduce the launch cost of commercial remote sensing satellites, a lightweight aluminum mirror with open back, triangular hole structure and three-point support was designed. Based on this structure, firstly, with the minimum mass as the optimization objective, the thickness and layout of the stiffener on the back of the mirror as the optimization object, and the minimum flexibility as the response constraint, the finite element method was used to optimize the size of the thickness of the stiffener on the back of the mirror and the topology optimization of the layout of the stiffener, and the lightweight rate of the aluminum mirror exceeded 63%. Then, the fixture was designed to carry out the single point diamond turning test. Finally, the surface shape accuracy of the mirror was measured by laser interferometer. The results show that the surface shape value of the mirror is PV(peak to valley) 1.48 μm, which can meet the requirements of commercial remote sensing satellites.

In order to broaden the wavelength range of the standards, the glass doped with praseodymium and neodymium rare earth elements with stable physical and chemical properties was used as the raw material of the visible wavelength reference material. At the same time, the polystyrene sheet (thickness of 1 mm) with stable physical and chemical properties was used as the raw material of the near-infrared wavelength reference material. The visible and near-infrared wavelength reference material was developed by using the characteristics that the two did not affect each other, and the superposition of the two would expand the band range. The uniformity of the sample was tested by F test method, and the stability of the sample was investigated by linear fitting method. The traceability was solved by tracing to the national standard. The band range of standard material was determined to be 430 nm~2 550 nm, and the uncertainty was 0.1 nm~1.0 nm, which made up for the defect that the wave range coverage in the current reference material is too narrow.

The preparation of high surface shape accuracy bandpass filter by double-sided coating method was studied, and the HWB900 substrate high surface shape accuracy bandpass filter film with outer diameter of Φ 25 mm and diameter-thickness ratio of 10:1 was prepared by dual-deposition. On one side the bandpass filter film was deposited and the matching layer was then coated to eliminate the stress-induced deformation on the other side. The results show that the mean transmittance τˉ is greater than or equal to 92% in the passband between 1 215 nm~1 265 nm, the transmittance τˉmax is less than 1% in the rejection band between 900 nm~1 135 nm and 1 345 nm~1 700 nm, and the root-mean-square (RMS) values of both side are superior than λ/20. Following a comprehensive analysis of the deformation law in both side, the thickness of the matching layer and the use characteristics of this method were determined. The described method has high practicality, and the prepared optical devices have excellent optical performance and high surface accuracy, which has important reference value and guiding significance for the preparation of optical devices with high surface shape accuracy.

The analytical study of the laser damage process can assist in the study of laser protection materials and also provide suggestions for laser processing. Therefore, a two-dimensional multi-physics field model based on COMSOL was developed for the laser ablation process of materials coated with high-reflectivity metals. Simplifying the problem of laser action on matter by using surface heat sources, the displacement field, temperature field and stress field of the destructive process were established and solved by the method of backward difference to obtain the ablation shape of the material under laser irradiation and the distribution characteristics of the temperature field and stress field. Comparing the simulation results with and without coating protection, the high reflectivity coating protection can reduce the laser ablation depth of the material by about 95% and the radial temperature and stress variation range by about 33% in the same time, which verifies the protective effect of the high reflectivity metal coating. Comparing the simulation results at different moments, the ablation depth and the temperature and stress variation range of the material increased uniformly with time. It provides a reference for the study of the laser damage process and the development of laser protective materials.

In order to optimize the performance and volume of the medium-range laser triangular displacement sensor, a mathematical model was established to optimize the structural parameters with the 200 mm~500 mm range as an example. In the structural design of the sensor, a plane mirror was used to fold the optical path, and the objective function was defined with the working object distance, lens focal length, linear array detector position and mirror position as the optimized parameters, gravitational search algorithm (GSA) was used to optimize the structure of the displacement sensor. After the algorithm iteration, compared with the traditional laser triangle structure with the same width limit, the sensitivity of the optimized structure was increased by 24.29% at 500 mm, and the nonlinear error was reduced from 11.40% to 7.43%. The results show that this structure and optimization algorithm have a positive effect on the performance and volume of the laser triangular displacement sensor.

Compared to the front-illuminated structure, the back-illuminated complementary metal oxide semiconductor (CMOS) image sensor significantly improves the shooting effect in low light environments, and lasers have different interference and damage mechanisms on different sensor structures. To investigate the impact of lasers on back-illuminated CMOS image sensors, experiments were conducted using a 1 064 nm continuous laser to study the interference and damage. In the interference experiment, saturation and over saturation phenomena were observed. When the laser power density exceeded 1.39×10?2 W/cm2, saturation occurred, and when it exceeded 1.03×104 W/cm2, over saturation occurred. In the damage experiment, spot damage, crossline damage, surface damage, and blindness were observed. When the power density exceeded 1.35×106 W/cm2, spot damage occurred, and when it exceeded 1.74×106 W/cm2, crossline damage occurred. When the power density exceeded 1.65×107 W/cm2, surface damage occurred. If the laser power was further increased, the detector ultimately became blind. The back-illuminated structure circuit is deeper than the front-illuminated structure and requires higher laser power for damage, Therefore, it has stronger laser resistance.

The experimental and simulation studies of a wavelength multiplexed mode-locked fiber laser based on Lyot filter effect were demonstrated. An all-fiber Lyot filter and a single-walled carbon nanotube saturated absorber were introduced into a fiber laser to filter the cavity gain spectrum and destroy single transmission mode of the pulse, which multiplexed the pulses at two different center wavelengths for transmission and mode-locking. Finely adjusting the intracavity polarization controller, when the pump power up to 70.4 mW, the dual-wavelength pulses are output with center wavelength of 1 534.2 nm and 1 546.0 nm, wavelength interval of 11.8 nm, repetition rate of 36.64 MHz, and signal-to-noise ratio of about 56.7 dB, respectively. In addition, a numerical simulation model based on the nonlinear Schrdinger equation was established for the numerical study of dual-wavelength mode-locked fiber lasers based on the Lyot filter effect. By the analysis of pulse spectral evolution, it was verified that intracavity gain spectral filtering played an important role in the formation and propagation of dual-wavelength pulses. The study of Lyot filtering effect in wavelength multiplexed fiber lasers could be further extended to realize tunable dual-wavelength generation, which could be applied to multi-scene dual-comb spectral measurement and coherent imaging.

Multi-aperture receiving technology can effectively suppress intensity scintillation in wireless laser communication. However, the effect of the diameter, spacing and number of receiving aperture on improving the performance of wireless laser communication is not clear and complete. Therefore, an optical transmission method based on composite phase screen was proposed, and the characteristics of multi-aperture reception were studied. Firstly, the power spectrum inversion method was combined with Zernike tilt method to generate a composite phase screen, and the mathematical model of optical transmission multi-aperture reception was constructed. Then, the diameter, spacing and number of receiving aperture were changed to calculate the change of intensity scintillation at the receiving end. Finally, the variation of multi-aperture received intensity scintillation was analyzed under the actual optical transmission scenario with different atmospheric refractive index structure constants, wavelengths and transmission distances. The results show that the intensity scintillation of five receiving apertures with diameters of 0.2 m and aperture spacing of 0.4 m decreases from 0.2032 to 0.0524 when the structure constant of atmospheric refractive index decreases from 2.2313×10?16 m?2/3 to 1.5812×10?17 m?2/3. When the wavelength of light wave changes from 532 nm to 1550 nm, the intensity scintillation of five receiving apertures with diameters of 0.2 m and apertures spacing of 0.4 m decreases from 0.2165 to 0.1523. When the propagation distance increases from 7×103 m to 7×105 m, the intensity scintillation of five receiving apertures with diameters of 0.2 m and aperture spacing of 0.4 m increases from 0.0043 to 0.3239. This study summarizes the law of multi-aperture receiving characteristics of wireless laser communication.