Overview: This paper is devoted to the research of synthetic aperture radar (SAR) real-time imaging processor. As the number of SAR imaging channels increases, the number of SAR imaging channels also presents new challenges. The optical processor not only has strong parallel processing ability, but also has the advantages of low power consumption, small volume, fast processing speed and programmability. Therefore, this paper designs and analyzes the SAR real-time imaging optical processor from the perspective of optical mechanical system design. Firstly, the system scheme principle of optical processor based on 4f optical structure is proposed, and the filtering algorithm is described in detail according to the principle. Secondly, according to the algorithm requirements, the relevant Fourier transform lens design is completed, and the compactness of 4f optical system is further strengthened. Then, the flexible design of the lens base is carried out, and the optimal parameter model is found by using the integrated optimization method. At the same time, it meets the modular design idea, completes the corresponding optical mechanical structure design, and obtains the optical mechanical system model of the overall scheme. The specific design results obtained based on the above research methods are as follows: in the optical design process, a Fourier transform lens with an entry pupil diameter of 21 mm, a field angle of 7°, and a focal length of 172 mm is obtained, and its MTF is better than 0.57 at 55 lp/mm. And the 4f optical system whose imaging quality tends to the diffraction limit meets the Rayleigh criterion. In the process of optical mechanical structure design, the overall size of 4f optical mechanical system is 405 mm×145 mm× 92 mm, with a mass of about 2.94 kg, and its volume and mass are only 30% and 48% of that of the inclined plane optical processor with the same SAR data processing level; At the same time, the RMS value of lens surface under normal temperature 1g gravity condition is less than λ/50(λ= 532 nm), the fundamental frequency of the overall structure is greater than 100 Hz, which can fully meet the expected design goal of the processor optical mechanical system. Finally, the simulation processing of SAR data is carried out on the optical platform. According to the simulation results, it shows that the system can be suitable for airborne or spaceborne real-time processing scenes. To sum up, the 4f optical processor designed in this paper can provide a certain reference value for improving the real-time imaging processing ability of SAR. In order to further improve the real-time imaging processing ability of synthetic aperture radar (SAR) in the face of massive echo data, the optical and mechanical system of SAR real-time imaging optical processor is designed and analyzed based on 4f optical structure. Firstly, a Fourier transform lens with an entrance pupil diameter of 21 mm, a field angle of 7°, and a focal length of 172 mm is designed for the filtering algorithm, and a compact design is adopted for the 4f optical system. Then, the flexible mirror base in 4f optical mechanical structure is optimized by using the integrated optimization method, and the overall structure is modularized designed and analyzed. The results show that the imaging quality of 4f optical system tends to the diffraction limit, and the MTF of Fourier transform lens is better than 0.57 at 55 lp/mm. The RMS value of lens surface shape of 4f optical mechanical system under normal temperature 1g gravity condition is less than λ/50. The fundamental frequency of the overall structure is greater than 100 Hz. The overall size of 4f optical processor is 405 mm×145 mm×92 mm, the mass is about 2.94 kg, and its volume and mass are only 30% and 48% of those of oblique plane optical processors with the same SAR data processing level. Through data simulation, it shows that the system design meets the needs of real-time imaging on satellite or airborne.

In order to make the recognition of sea fog with high accuracy and reasonable interpretability, the cloud-aerosol LiDAR with orthogonal polarization (CALIOP), which is capable of penetrating clouds and obtaining atmospheric profiles, was first used to annotate medium and high cloud, low cloud, sea fog, and clear sky sea surface samples. Then, bright temperature features and texture features were extracted for each type of sample in combination with multi-channel data from the Himawari-8 satellite. Finally, according to the needs of sea fog monitoring, the inference decision tree for sea fog monitoring was abstracted and a deep neural decision tree model was built accordingly, which achieves high accuracy for nighttime sea fog monitoring while having strong interpretability. The continuous observation data of Himawari-8 on the night of June 5, 2020 was selected to test the sea fog. The monitoring results can clearly show the dynamic development process of the sea fog events. At the same time, the proposed sea fog monitoring method has an average probability of detection (POD) of 87.32%, an average false alarm ratio (FAR) of 13.19%, and an average critical success index (CSI) of 77.36%, which provides a new method for disaster prevention and mitigation of heavy fog at sea.Remote sensing satellites have the characteristics of wide coverage and continuous observation, and are widely used in research related to the sea fog identification. Firstly, the Cloud-Aerosol LiDAR with Orthogonal Polarization (CALIOP), which is capable of penetrating clouds and obtaining atmospheric profiles, was used to annotate medium and high cloud, low cloud, sea fog, and clear sky sea surface samples. Then, bright temperature features and texture features were extracted from each type of sample in combination with multi-channel data from the Himawari-8 satellite. Finally, according to the needs of sea fog monitoring, the inference decision tree for sea fog monitoring was abstracted and a deep neural decision tree model was built accordingly, which could achieve high accuracy for nighttime sea fog monitoring while having strong interpretability. The continuous observation data of Himawari-8 on the night of June 5, 2020 was selected to test the sea fog. The monitoring results can clearly show the dynamic development process of the sea fog events. At the same time, the sea fog monitoring method in this paper has an average probability of detection (POD) of 87.32%, an average false alarm ratio (FAR) of 13.19%, and an average critical success index (CSI) of 77.36%, which provides a new method for disaster prevention and mitigation of heavy fog at sea.

In summary, the basic principle, sensing scheme, and performance of F-SBS optical fiber sensors are introduced in this paper. With the F-SBS sensor applied in practice, increasing demand for high accuracy, and high spatial resolution emerges, which we believe will be dominant in the research of substance identification sensors in the future.Forward stimulated Brillouin scattering (F-SBS), a 3-order nonlinear effect in optical fibers, has become the hotspot in recent years, due to its great potential in substance identification, and fiber diameter measurement, etc. Through research and analysis of the progress of F-SBS, the main principle and key techniques are generalized in this paper. Distributed sensing schemes based on local light phase recovery, opto-mechanical time-domain reflectometry, and opto-mechanical time-domain analysis are emphatically introduced here. With the gradual practical application of F-SBS, the demand for distributed measurement of F-SBS with high precision and high spatial resolution becomes more and more significant, which will be the main research direction of F-SBS in optical fibers in the future.

This paper is verified on the Apollo data set. The continuous road live screenshots are extracted from the data set to obtain the required set of time-series pictures, and the targets in the images are detected and tracked. Finally, the experiments show that the algorithm in this paper has an obvious effect on solving the occlusion problem. This paper has also been tested on the actual road, and the effect of medium and long-distance vehicle detection is good. The experiment shows that the algorithm can meet the real-time detection requirements under the actual road conditions.In the field of automatic driving target tracking, there is a problem that the target occlusion will cause the loss of feature points, resulting in the loss of tracking targets. In this paper, a multi-target tracking algorithm combining spatial mask prediction and point cloud projection is proposed to reduce the adverse effects of the occlusion. Firstly, the temporal image data is processed by an example segmentation mask extraction model, and the basic mask data is obtained. Secondly, the obtained mask data is input into the tracker, the mask output of subsequent sequence images is obtained through the prediction model, and the verifier is used for a comparative analysis to obtain an accurate target tracking output. Finally, the obtained 2D target tracking data is projected into the corresponding point cloud image to obtain the final 3D target tracking point cloud image. In this paper, simulation experiments are carried out on multiple data sets. The experimental results show that the tracking effect of this algorithm is better than other similar algorithms. In addition, this paper is also tested on the actual road, and the vehicle detection accuracy reaches 81.63%. The results verify that the algorithm can also meet the real-time requirements of target tracking under the actual road conditions.

Overview: With the advent of the 5G communication era, much attention has been paid to free manipulate electromagnetic waves at a subwavelength scale. Meta-surface with subwavelength structural dimensions have shown broad prospects in the field of microelectronic components due to their powerful electromagnetic control capabilities. In this paper, a subwavelength comb-shaped space-filling meta-surface is designed by using metal curves according to the resonator principle. A series of studies on spoof localized surface plasmon resonance characteristics are carried out on this basis. Theoretical analysis and calculation are carried out according to the structural characteristics. Compared with the traditional meta-surface supporting spoof localized surface plasmons, this curved arrangement of continuous metals will form an air waveguide similar to a resonant cavity, allowing for larger waveguide lengths at smaller dimensions, resulting in greatly reduced working frequency band. Under the excitation of the incident electromagnetic wave, spoof localized surface plasmon like Fabry-Perot resonance will be generated. The resonance frequency of the meta-surface can be calculated from the resonance conditions. Using the finite element method to simulate the 2D comb structure with different periods, it is found that the Q-factor of 1.7×105 can be obtained when the structure compression ratio (λ/L) is 444 by adjusting the structure period. In the study of the higher-order eigenmodes of the comb-shaped space-filled meta-structure, it was found that the spoof localized surface plasmons excited by space-filling structures are alternately supported by magnetic and electric multipoles modes, and the scattering cross-section of the eigenmodes of each order are presented at equally spaced frequencies. By changing the distribution type of the space-filling structure, the supported surface plasmon resonance properties are not affected by the arbitrary bending of the structure, and the magnetic field intensity distribution of the eigenmodes only changes with the direction of the air waveguide. Finally, the 3D simulation of the comb-shaped space-filling structure is carried out, from the X-Z section electric field diagram, it can be observed that the spoof localized surface plasmons generated by the structure can bind the energy on the surface of the structure and generate localized field enhancement. The space-filling design in this paper makes full use of the structure space. This highly localized structure can generate a higher Q-factor under the deep subwavelength structure, and the electromagnetic properties are not affected by the arbitrary bending of the metal structure, and have better stability. It provides a new idea for the preparation of nanometer-sized high-efficiency electromagnetic resonators. With the advent of the 5G communication era, much attention has been paid to manipulate electromagnetic waves at subwavelength scale. In this paper, we propose comb-shaped meta-structures based on space-filling curves, and use theoretical analysis and numerical simulation method to study the near-field electromagnetic properties of these meta-surfaces. Finally, the effective excitation of all order eigenmodes of spoof localized surface plasmon resonance can be realized in these meta-structures. Through adjusting the structure period to change the effective length of the air waveguide, high compression ratio between resonant wavelength and device size, and high Q-factor can be simultaneously achieved. Moreover, spoof localized surface plasmons excited by space-filling structures are alternately supported by magnetic dipole and electric dipole modes. As a consequence, changing the distribution form of the space-filling curve with the remaining parameters unchanged, the resonant characteristics of the surface plasmon supported by the structure are not affected by the shape tortuosity, but are only related to the total length of the equivalent waveguide. Thus, the space-filling curvilinear structure can be freely designed. We believe that, our results have great potential in designing the high Q-factor miniaturized electromagnetic resonator devices based on spacing-filling curvilinear meta-structure.

In recent years, slightly off-axis digital holography which combines the advantages of off-axis and on-axis has been vigorously developed. In order to further improve its real-time performance, a synchronous slightly off-axis system based on the field of view (FOV) multiplexing technique has been applied. However, the spatial position of the holograms collected by this technology is unknown, which causes a spatial mismatch problem. In order to ensure the accuracy of the subsequent holographic reconstruction, it is necessary to perform a spatial mismatch calibration. The existing calibration methods can be roughly divided into: intensity-based calibration methods and phase-based calibration methods. Intensity-based calibration methods are susceptible to environmental noise, and phase-based calibration methods only have pixel-level accuracy. At the same time, none of the existing methods take into account the longitudinal position error caused by the sensor tilt.The existing spatial mismatch calibration methods can only achieve pixel-level calibration accuracy due to the limitation of principle, and are easily disturbed by the environmental noise. In this paper, a spatial mismatch calibration method for a sub-pixel-level simultaneous slightly off-axis digital holographic microscope system is proposed. In the modeling, the method not only analyzes the lateral position error caused by the image segmentation, but also further considers the longitudinal position error caused by the sensor tilt, and summarizes the calibration process as a nonlinear multi-variable optimization problem. In this paper, the particle swarm optimization algorithm is used to solve this optimization problem because of its simple structure, high convergence efficiency, and strong global search ability. In the calibration process, a phase-only wavefront based on the phase aberration is established, and the root mean square error of the phase-only wavefront is used as the target function to remove the influence of noise on the calibration accuracy. Simulation results show that the proposed method has sub-pixel accuracy, and experiment demonstrates the effectiveness of the method in the practical systems.