In order to realize the modular design of a cloud camera control system and improve the system integration, a design method for the hardware platform of an on-bit real-time cloud judgement system based on field programmable gate array (FPGA) is proposed. On the basis of the system functional module division, an on-chip dual-core CPU software architecture is established. One CPU independently processes the cloud judgement algorithm to ensure the real-time performance of the proposed algorithm, and the other CPU is used for data interaction with satellites and partial data pre-processing. The timing control of the CCD imaging and peripheral interface is realized by the self-defined intellectual property (IP) core. Taking the CCD image acquisition and storage module as an example, the designs and time sequences of the CCD driving circuit, analog front-end circuit, and data storage circuit are mainly discussed, and the design method of the IP core of the module is analyzed. Finally, the imaging performance parameters of the cloud camera are tested. Experimental results show that the change of the dark current noise of the camera with the integration time in the set integration time is small. The output nonlinearity is 1.29% at the central field of view, and the signal-to-noise ratio is 128.1 when the signal intensity is 80% of the saturated light intensity, which meets the requirements of the cloud camera.

We study the polarization distribution model under wavy water surfaces dominated by skylight, verify the feasibility of using polarization navigation under wavy water surfaces, and discuss the influence of different sun positions and wavy water surfaces on the underwater polarization distribution model. The Cox-Munk sea wave model is used to describe the wavy water surface. The underwater polarization propagation model is built on the basis of the Stokes vector and Mueller matrix, which consider the atmospheric Rayleigh scattering, the air-water interface refraction, and the single Rayleigh scattering of water molecules. The consistency between the simulation result and measurement result proves the accuracy of the proposed model. The results show that the wavy underwater polarization distribution model dominated by skylight is predictable, and it is mainly related to the sun position and the wave condition on the water surface. The proposed model can analyze the polarization characteristics of wavy underwater more accurately and provide a theoretical basis for the application of underwater polarization navigation.

The space-borne synchronous monitoring atmospheric corrector (SMAC) is a sensor that can obtain real-time spatial multispectral polarization information of the atmosphere. In this way, aerosol and water vapor parameters that are then used for the atmospheric correction of high-spatial-resolution images can be provided. A portable multichannel reference light source (PMRLS) was designed to evaluate the optical performance of the SMAC during environmental testing. The multichannel design of this source was consistent with that of the SMAC and had independent luminous components corresponding to each channel. A luminous element was equipped with a semitransparent diffuser plate, thus, enabling the luminous components to produce uniform illumination. To reduce the power consumption, a light-emitting diode and halogen tungsten lamp were chosen as the luminous elements at the visible and near-infrared band and the short-wave infrared band, respectively. The luminous element was driven by a low-noise stable current and cooled by an electric fan and cooling fin so as to improve the temperature stability of the PMRLS. In addition, the position of the PMRLS was limited by design to improve its repeatability. The radiance adjustment and performance testing for the PMRLS were performed using the SMAC. The maximal deviation in the radiance found during the PMRLS's radiance adjustment was within 7%, and the instability and non-repeatability values were less than 0.76% and 1.3%, respectively. Overall, therefore, the performance of the PMRLS meets the requirements for a quick evaluation of the SMAC.

For radiance images on the top of atmosphere obtained by wide field of view (WFV) camera in GaoFen-1 (GF-1) satellite, atmospheric corrections at four bands are made to obtain surface reflectance images based on 6S atmospheric radiation transmission model, aerosol optical depth from Terra in Moderate-Resolution Imaging Spectroradiometer (MODIS) and the parameter products (MCD43A1) of MODIS bi-directional reflection distribution function model. Then the calculation methods of the image definition values are based on Brenner gradient operator and medium frequency discrete cosine transform. The calculation results show that the image definition values after correction are higher than those before correction, so the edge texture information of the image after correction is clearer than that before correction. The signal-to-noise ratio (SNR) is evaluated based on the principle of threshold segmentation. The results show that the SNR of each band before and after correction has an increasing relationship with the radiance. The atmosphere has more influence on the short-wave band than the long-wave band.

A ZnO ultraviolet photodetector with a metal-semiconductor-metal (MSM) structure was successfully prepared by the radio frequency magnetron sputtering technology. The bias voltage dependence of the responsivity and cutoff wavelength of the detector is studied. With the increase of bias voltage, the responsivity of the detector gradually increases and tends to saturate and the response cutoff wavelength of the detector is redshifted by 12 nm. This is attributed to the broadening of the depletion layer and the tilt of the bandgap caused by the field. In this work, an effective method is proposed to control the cutoff wavelength of the detector by an external bias voltage, which is of great significance to the further investigation and application of ultraviolet photodetectors.

The influence of different manufacturing errors on focusing performance of large-scale super-oscillatory lens (SOL) is revealed through a quantitative study for practical use based on rigorous vector angular spectrum theory. Theoretical calculation results show that the influence of the manufacturing errors on focusing performance of amplitude-type SOL (metallic film) and phase-type SOL (dielectric layer) is the same; central position deviation mainly affects the focusing focal length, while the width deviation mainly influences the focal spot distribution; the position and width deviations within the range of ±150 nm are the maximum allowable manufacturing tolerances for each SOL ring belt. Longitudinal etching depth deviation mainly affects the focused intensity of the phase-type SOL. When the relative phase difference introduced by the etching depth is π, the focused intensity reaches its maximum. To maintain a greater focused intensity, phase modulation should be kept within the range of 0.8π--1.2 π.

A vibration sensor based on the reflection-type excessively tilted fiber grating (ExTFG) cantilever is proposed in this work. The bending strain characteristics and vibration sensing principle of ExTFG are theoretically analyzed, and a finite element model is constructed by ANSYS to analyze the modality and resonance characteristic response of the sensor. The dynamic response characteristics of bending vibration of the sensor under the periodic load are studied experimentally. The results show that the vibration sensor based on the reflection-type ExTFG cantilever exhibits a good dynamic response to the acceleration continuous excitation signal. The natural frequency of the sensor can be changed by adjusting its length. The sensor has a good linear response in the range of 1--5g, and its maximum acceleration sensitivity is increased by about 2.5 times compared to the transmission-type ExTFG vibration sensor. The maximum acceleration sensitivity of the transverse electric mode and transverse magnetic mode reaches 0.3 V/g and 0.26 V/g, respectively. In addition, the size of the sensor probe is small enough, and the ExTFG is used as the sensitive unit without additional packaging, so it has potential value in practical applications.

In this paper, we describe the tensile-strength enhancement of optical fibers obtained by controlling the parameters of the fused biconical tapering process used to produce them. Numerical simulations using the finite-element method show that the internal stress in an optical fiber is related to the cooling time after the tapering process. This stress is reduced by increasing the cooling time, although the internal stress at the edge of the heated area remains significantly higher than that of other areas. Experimental studies based on the simulation results show that the tensile strength of a tapered optical fiber is gradually enhanced as the cooling time is increased from 10 s to 600, 1200, and 1500 s.

Time delay and integration charge-coupled devices (TDICCD) and multispectral linear array sensor are usually used as the imaging detector in aerospace remote sensing camera. In order to obtain high-quality aerospace remote sensing images, the charge transfer speed of the TDICCD is required to be equal to the image motion velocity and in the same direction. When the aerospace remote camera is in orbit push-broom imaging, the distortion will cause the mismatch between the image motion direction and the integration direction. In order to reduce the mismatch error between the direction of charge transfer and the image motion direction, the detectors are spliced into a curve to compensate for the image movement caused by distortion. First, a mathematical model of mismatch between the time delay and integration (TDI) direction and the image motion direction is established, and the directions of the pincushion distortion and the barrel distortion curve splicing are given respectively. Second, the calculation formula for the angle between the image shift direction and the TDI direction is derived, and the objective function is established to calculate the curve stitching angle of each detector. Finally, an on-orbit curve splicing experiment is carried out. The results show that the registration accuracy of the edge field of view after curve splicing is improved from 4 pixel to 1 pixel compared to before splicing.

Aiming at the problem that the fused results of low resolution source images are not good for the subsequent target extraction, a multi-band image synchronous super-resolution and fusion method based on Wasserstein generative adversarial network with gradient penalty (WGAN-GP) is proposed. Firstly, the multi-band low-resolution source images are enlarged to the target size respectively based on the bicubic interpolation method. Secondly, the enlarged results are input to a feature extraction (encoding) network to extract features respectively and combine them in a high-level feature space. Then, the initial fused images are reconstructed by decoding network. Finally, a high-resolution fused image is obtained through a dynamic game between the generator and the discriminator. The experimental results show that the proposed method can not only achieve multi-band images super-resolution and fusion simultaneously, but also the information amount, clarity, and visual quality of the fused images are significantly higher than other representative methods.

In order to solve the problem of the sensitivity of the highest singular value bit under geometric attack and the poor anti-geometric attack performance of zero watermark, an image zero watermark technology based on ameliorated singular value and sub-block mapping is proposed. Firstly, the carrier image was Arnold scrambled to eliminate the correlation between pixels, and then Curvelet transformation, partitioning and singular value decomposition were performed to obtain the stable characteristics of the carrier image. At the same time, a seed block mapping mechanism is proposed to divide the original copyright image into different sub-blocks, and by suming the sub-blocks, different characters are used to represent the water imprint block. Finally, the feature of the carrier image and the water imprint block are logically calculated to generate zero watermark by bit. Experimental results show that the proposed zero-watermarking algorithm has strong robustness under geometric attack, non-geometric attack and combined attack, and the generated zero-watermark information is more secure.

Low-resolution (LR) grayscale images with multi-wavelength information are difficult to fully demultiplex. High-resolution (HR) colored images reconstructed from LR images are prone to channel crosstalk. To reconstruct HR colored images that are not prone to channel crosstalk, we propose an HR colored image reconstruction algorithm based on a three-dimensional convolutional neural network (CNN). The principal component analysis method is used to extract structural information from HR monochromatic images and LR colored images, and then the CNN is trained based on the structural information to establish a mapping relationship between the HR monochromatic image and LR colored image. Consequently, a HR colored image is generated. The experimental results show that the proposed algorithm can obtain HR colored images without channel crosstalk and color distortion. The quantitative evaluation indexs show that the root mean square error and structural similarity parameter are less than 0.1 and greater than 0.9, respectively.

The simultaneous imaging polarimeter can obtain the transient polarization characteristics of moving objects, and it has a wide application prospect. However, the polarization detection channels differ in spatial and radiation response, which interferes with the accurate establishment of the instrument Muller matrix. The system error source is analyzed, and the calibration and preprocessing method is proposed for the amplitude divided simultaneous imaging polarimeter. The system error of polarization imaging detection is eliminated by the calibration and correction of non-uniformity of detectors, inconsistency of radiation response, deviation of polarizers oriented angles, and difference of instantaneous field of views. The results show that after the calibration and preprocessing, the CCD non-uniformity of every channel decreases by 2.24% on average, the absolute values of radiation response differences ratio decrease by 17.22% on average, the actual polarizer oriented angles are corrected by 1.71° on average, and the imagery pixel offsets are corrected by 1.87 pixel on average. After correction, the measurement error of polarization degree and polarization angle decrease by 0.47 and 32.84°, respectively. The outdoor scene is measured and tested, the Stokes parameters are calculated correctly after preprocessing, and the physical characteristics of different materials are highlighted after the polarization imaging fusion.

This paper proposes an optimized lighting design method of light-emitting diode (LED) ring array structure for machine vision, which can obtain high-quality images. The proposed method consists of imaging theory and Taguchi method to obtain uniform illumination distribution. The relationship between image contrast and illumination uniformity is derived based on the imaging theory. Furthermore, the main parameters of illumination distribution are acquired, and simulation experiments are designed in a direct intersection table and simulated using TracePro software. Then, the best parameter combination and influence degree of each parameter on uniformity are obtained; the illumination uniformity of the optimized parameter combination is up to 89.31% in the simulation experiments. Finally, a kind of machine vision light source with excellent performance is designed. Relevant experiments show that the lamp can meet the lighting requirements of machine vision (uniformity is 80.35%). The proposed method is an effective strategy to deal with optical design for machine vision.

Starting from heat conduction equation and thermal elastic equation, based on EasyLaser simulation software, the temperature distribution and thermal aberration of laser irradiated Si reflective mirror and SiO2 window mirror are simulated and calculated. The spatio-temporal characteristics of temperature rise and thermal aberration of the two elements under the same absorption are compared. The optical-thermal-mechanical control multi-physical coupling simulation are carried out to compare the thermal effect of the laser-irradiated Si mirror and the SiO2 window mirror on the far-field characteristics of laser transmission and the effect of adaptive optics correction. Simulation results show that due to the poor thermal conductivity of the SiO2 window mirror, the thermal aberration linearly increases with the increase of the laser irradiation time, and its distribution is similar to the spatial distribution of the irradiated laser spot, and it still exists for a long time after the laser irradiation is stopped. The Si reflector has good thermal conductivity. The temperature distribution is homogenized in a short time, resulting in a small temperature gradient. The thermal aberration first increases rapidly and then slowly, and the influence of the thermal effect disappears quickly after the laser irradiation is stopped. The spatial distribution of the experimental spot intensity has different effects on the thermal effects of the two components: for the SiO2 window mirror, the high spatial frequency component of the thermal aberration increases, which seriously affects the far-field transmission of the laser beam and the effect of adaptive optics correction, while the Si mirror is hot. The conductivity is large, and the impact is small.

We have experimentally investigated mid-infrared (MIR) difference-frequency generation (DFG) based on passive all-optical synchronization. Synchronized pulses were obtained by master-slave injection locking between all-polarization-maintaining Yb- and Er-doped fiber lasers, which were amplified by cascaded fiber amplifiers to realize MIR picosecond pulses at 3071 nm within a PPLN crystal. The maximum pump conversion efficiency is 68.3%, and the peak average power reaches 1.36 W. The results show that the synchronous pulse induced DFG can substantially reduce the pump threshold. Additionally, benefiting from the all-polarization-maintaining fiber architecture for the pulse generation, synchronization and amplification, the MIR ultrafast light source exhibits excellent long-term stability with a relative fluctuation of average power as low as 0.2%.

In order to efficiently extract the local geometric structure features of LiDAR point cloud data and realize the registration, detection and recognition of three-dimensional (3D) targets, a local point cloud feature descriptor based on hierarchical Mercator projection (HMec) is proposed in this paper. First, the traditional method is used for feature extraction. Then, the local neighborhood points of 3D point cloud data are projected onto multiple Mercator planes using the Mercator projection with conformal feature. Finally, the local feature descriptors of feature points are obtained by counting the histogram of each Mercator plane. HMec feature descriptor can retain the local geometric structure features of point cloud, so as to improve the discrimination of feature descriptor. The test results on Bologna and 3DMatch datasets show that HMec feature descriptors have stronger discrimination and better noise robustness than the other nine local feature descriptors

In this study, we employed the CALYPSO structure searching method and density functional theory to systematically investigate the structural, electronic and spectral properties of a Ni-doped B20- cluster. The lowest energy structures of B20- and Ni B20- were obtained with the PBE0/6-311+G(d) level. The obtained structure of B20- is consistent with previous experimental and theoretical research reports. The Ni B20- cluster is composed of a nickel atom sandwiched by two B10 monocyclic rings. Furthermore, the natural population analysis, the natural electron configuration and molecular orbitals were studied based on the lowest energy structures. The results show that charges are transferred from Ni to B atoms and strong spd hybridization occurs in the Ni and B atoms. Finally, we simulated the photoelectron spectroscopy, IR, and Raman spectra, and assigned the main vibrational peaks for further experimental investigation. This research presents a powerful reference for future experimental synthesis and characterization of nickel-doped boron-based nanomaterials.

The parallel differential confocal three-dimensional imaging method realizes multi-point parallel detection by dividing the illumination light into multiple isolated beams, which solves the problem of low imaging efficiency caused by point-by-point scanning of traditional differential confocal imaging. It is an ideal fast and high-precision three-dimensional imaging method. However, both non-homogeneous illumination and field curvature of an optical imaging system induce errors in the measurement results during the process of parallel differential confocal detection. The effects of inevitable non-homogeneous illumination and field curvature of an optical system during the wide-field imaging process on the parallel differential confocal axial measurement are analyzed, a wide-field error correction method is proposed, and a theoretical model of wide-field error correction is established for the parallel differential confocal axial measurement. The experimental results show that the proposed method can effectively suppress the influence of non-homogeneous illumination on the measurement results and correct the axial measurement error caused by the field curvature of the optical imaging system. It ensures the universality of parallel differential confocal nanometer-scale axial measurement accuracy in the full field of view. The implementation process of this method is simple and convenient, and it is also applicable to error correction of other parallel confocal detection methods.

The optimization design of an optical-mechanical system has the characteristics of high efficiency and short iteration period, but the optimization of the complex optical-mechanical system has the problem of difficulty in convergence. An approximate optimization algorithm based on the combination of Latin hypercube and radial basis function (RBF) neural network is proposed in this work, and it is applied to the design of main mirror of spliced telescopes with curvature error adjustment mechanism. Simulation results show that the main mirror optimized by the algorithm has reached the design index, which provides a new idea for solving the problem of long iteration time for complex optical-mechanical system.

Because of the current testing methods restricting the application of large-aperture, large-relative aperture concave aspheric mirrors, a large-aperture, large-relative aperture concave aspheric surface testing method based on near-double-lens is proposed. Different from the Offner testing method, the lens in the testing optical path is used as a correcting lens and a self-collimating-lens in the optical path before and after reflection. The initial structure is derived according to the third-order aberration theory. The testing results of using a single lens and a near-double-lens as correcting lens are shown in diagrams respectively and analyzed. The experimental results show that the testing method in which the self-collimating lens is located in front of the conjugate back point can be used for the testing of large-aperture, large-relative-aperture concave aspheric mirrors. The proposed method is simpler and more convenient in terms of processing, assembly and use, and provides a new idea for the testing of concave aspheric surfaces, and lays a foundation for the use of three lenses to test concave aspheric surfaces with larger apertures and relative apertures.

Herein, a Schottky junction UV photodetector based on multilayer PtSe2/TiO2 nanorod (NR) arrays is proposed. The multilayer PtSe2 film and TiO2 NRs are synthesized using chemical vapor deposition and hydrothermal methods, respectively. The wet transfer method is used to fabricate the multilayer PtSe2/TiO2 NRs Schottky junction device with upper and lower structures. Photoelectric measurement results show that the designed device exhibits a high sensitivity to 365-nm UV light. The switch ratio of the device can reach as high as 5.5×10 4, the responsivity and specific detectivity are 57 mA/W and 8.36×10 11 Jones, respectively. Moreover, the device shows a good stability and the photocurrent remains nearly unchanged after storage in air for 5 weeks. Finally, the image sensing characteristics of a single device are investigated, which confirm that the PtSe2/TiO2 photodetector can be used as an image sensor to achieve simple UV pattern imaging.

As a structured beam exhibiting a spiral phase and an orbital angular momentum, the Doppler effect of an optical vortex possesses a frequency shift component caused by the relative motion that is perpendicular to the beam cross-section compared with the Doppler effect of the classical plane beam. In this study, a velocity-Poynting vector model and a phase modulation model are established to study the linear and rotational Doppler effects of optical vortex, obtaining the generation law of Doppler frequency shift of the vortex light under compound motion. Moreover, these two models are used to analyze the Doppler frequency shift on the surface of the cylinder, which is a typical spatial moving target. The same results are obtained, proving the correctness of the proposed theoretical analysis method. The distribution law of the frequency shift of the rotating cylinder detected through vortex light is proposed herein, and the influence of different optical vortex radii and cylinder sizes on the detection results is explored.

Marine aerosols are important components of atmospheric aerosols. In order to study their impact on quantum communication, for a given transmission distance we have therefore analyzed the dependence of the link attenuation on the concentration, size-spectrum distribution, and extinction coefficients of the marine aerosol particles. In particular, we have studied and simulated the quantitative relationships of particle concentrations and transmission distance on the link attenuation, channel capacity, channel fidelity, and channel error rate. The simulation results show that when the transmission distance is 8 km and the ocean aerosol particle concentration is 300/m 3 and 500/m 3, the corresponding link attenuation, channel capacity, and channel bit error rate are 0.407 dB/km and 0.679 dB/km, 0.423 bit/s and 0.349 bit/s, 0.027 and 0.092, respectively. When the concentration of ocean aerosol particles is 500/m 3 and the transmission distance is 5 km and 7 km, the corresponding channel fidelity is 0.911 and 0.849, respectively. Ocean aerosols thus have varying degrees of influence on the performance of free-space quantum communication. In actual quantum communication, various performance parameters must therefore be adjusted according to the concentration of the ocean aerosol particles in order to ensure normal communication.

In this paper, the composition and working mode of the on-board calibration component on the visible and near infrared band of GF-5 visible and infrared multispectral imager (VIMI) is introduced. The attenuation of on-board 12-time solar diffuser (SD) bidirectional reflection distribution function (BRDF) on the satellite after VIMI launch is analyzed. Comparing the long-term solar data observed by SD reflectance degradation monitor (SDRDM) shows that the attenuation degree of different monitoring band detectors is different. Among them, the 900 nm monitoring band silicon detector has the largest attenuation, about 4.3%. When the incident angle is close to the observation azimuth, the attenuation factor (H factor) of SD BRDF changes little. According to the physical model of the H factor, the measurement uncertainty of actual monitoring by SDRDM is less than 0.86%, which meets the index requirement of less than 1.5%, and the radiance uncertainty of the output spectrum of the calibration component on the VIMI satellite is less than 3.4% during the lifetime.

To address the problem of wavelength calibration of a Brillouin NIR spectrometer with a maximum resolution of 0.1 pm, a calibration process using the principle of collaborative fusion calibration is proposed. This process is based on the idea of gradually reducing the wavelength error of multiple calibrations. The calibration process is as follows: first, the theoretical wavelength was calculated based on the Brillouin spectral analysis modal and relative parameters, such as the pump signal wavelength, Brillouin frequency shift, and gain in spectrum lineshape; then, the relative wavelength was calibrated using the Fabry-Perot etalon; finally, the absolute wavelength calibration based on the gas chamber was completed. The gas chamber was filled with a mixed gas of HCN, 12CO, and 13CO to achieve absolute wavelength calibration in the C and L bands. A ghost identification and correction algorithm was also presented based on the commensalism of gain and loss spectrum of stimulated Brillouin scattering. Experimental results show that the theoretical wavelength deviation is more than 10 pm, and wavelength uncertainty of ±2.5 pm can be achieved by relative wavelength calibration. Moreover, the wavelength uncertainty of the absolute wavelength calibration is ±0.035 pm.