2022

• Record 277 of
  
  Title:Pointing Calibration Method for Imaging Systems of Photoelectric Theodolites with Multi-Field of View Stitching
  
  Author(s):Zhao, Huaixue(1,3); Liu, Bo(2); Xie, Meilin(2); Tian, Liude(1,3); Zhou, Yan(1)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 42  Issue: 6  DOI: 10.3788/AOS202242.0612002  Published: March 25, 2022  
  Abstract:After analyzing the traditional calibration model for target deviations of photoelectric theodolites and the characteristics of photoelectric theodolites with multi-field of view stitching, we derive a calibration formula for target deviations of photoelectric theodolites with imaging systems that have large collimation errors and zero offsets according to the principle of coordinate transformation. The above calibration formula and target simulator pointing are used to reversely deduce the calculation formula of target deviations of photoelectric theodolites with large collimation errors and zero offsets. The pointing calibration coefficient of the imaging system is solved through its actual target deviation. A verification test shows that the proposed approach breaks through the limitations of the existing distortion correction model and can be applied to pointing calibration of the imaging systems of photoelectric theodolites with multi-field of view stitching. The measurement system with a 2×3 externally stitched array discussed in this paper has a collimation error of 11.26° and a zero offset of 18.08°. Both the horizontal and vertical pointing errors are less than 1/5 pixel after the system is calibrated by the pointing calibration method for photoelectric theodolites with multiple externally stitched imaging modules. © 2022, Chinese Lasers Press. All right reserved.
  Accession Number: 20222812340244
• Record 278 of
  
  Title:Rotation-aware correlation filters for robust visual tracking
  
  Author(s):Liao, Jiawen(1,2,3); Qi, Chun(2); Cao, Jianzhong(1); Wang, Xiaofang(4); Ren, Long(1,2,3); Zhang, Chaoning(5)
  Source: Journal of Visual Communication and Image Representation  Volume: 83  Issue:   DOI: 10.1016/j.jvcir.2021.103422  Published: February 2022  
  Abstract:Recent years have witnessed several modified discriminative correlation filter (DCF) models exhibiting excellent performance in visual tracking. A fundamental drawback to these methods is that rotation of the target is not well addressed which leads to model deterioration. In this paper, we propose a novel rotation-aware correlation filter to address the issue. Specifically, samples used for training of the modified DCF model are rectified when rotation occurs, rotation angle is effectively calculated using phase correlation after transforming the search patch from Cartesian coordinates to the Log-polar coordinates, and an adaptive selection mechanism is further adopted to choose between a rectified target patch and a rectangular patch. Moreover, we extend the proposed approach for robust tracking by introducing a simple yet effective Kalman filter prediction strategy. Extensive experiments on five standard benchmarks show that the proposed method achieves superior performance against state-of-the-art methods while running in real-time on single CPU. © 2022 Elsevier Inc.
  Accession Number: 20220411492416
• Record 279 of
  
  Title:Adaptive acquisition time scanning method for photon counting imaging system
  
  Author(s):Zhu, Wen-Hua(1,2,3); Wang, Shu-Chao(1,2,3); Wang, Kai-Di(1,2); Chen, Song-Mao(1,2,3); Ma, Cai-Wen(1,2); Su, Xiu-Qin(1,3)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 71  Issue: 15  DOI: 10.7498/aps.71.20220173  Published: August 5, 2022  
  Abstract:Photon counting imaging system has recently received a lot of attention in ultra-weak light detection. It has high sensitivity and temporal resolution. The single-point scanning photon counting imaging system typically accumulates a large number of photon events to reconstruct depth image. Acquisition time is redundant or insufficient, which limits imaging efficiency. In this work, a new method called adaptive acquisition time scanning method (AATSM) is proposed to solve this dilemma. Comparing with the fixed acquisition time of every pixel, the method can automatically select the acquisition time of per pixel to reduce total time of data collecting while obtaining depth images. In experiment, we acquire the depth images with the same quality by different scanning methods, showing the feasibility of AATSM. The total time ofcollecting data by the AATSM can be reduced to 11.87%, compared with fixed acquisition time of every pixel. This demonstrates the capability of speed scanning of AATSM, which can be used for the fast imaging of photon counting system. © 2022 Institute of Physics, Chinese Academy of Sciences. All rights reserved.
  Accession Number: 20223412611624
• Record 280 of
  
  Title:Separating and Testing Method for Influencing Factors of Phase Stability ofDoppler Asymmetric Spatial Heterodyne Interferometer for Atmospheric Wind-Field Detection
  
  Author(s):Fu, Di(1,2); Chang, Chenguang(1); Sun, Jian(1); Li, Juan(1); Wu, Kuijun(3); Feng, Yutao(1); Liu, Xuebin(1)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 42  Issue: 18  DOI: 10.3788/AOS202242.1801003  Published: September 25, 2022  
  Abstract:The Doppler asymmetric spatial heterodyne interferometer, a new type of mid- and upper-atmospheric wind-field detection system, can achieve atmospheric wind-field measurement by the inversion of the Doppler shift of observed source spectra after calculating the changes in interferograms. The reference phase is a necessary parameter to determine the Doppler shift of the wind field, and its stability is one of the core indicators to ensure the accuracy of wind speed measurement. This paper investigates three factors that affect the reference phase of an interferometer, namely, the phase drift of asymmetric quantities, phase slope drift, and phase drift of interferograms. Moreover, the theoretical analysis of the thermal phase drift is carried out on the basis of the principle of Doppler asymmetric spatial heterodyne interference. The separating and testing method for the phase-drift quantities of each factor is proposed, and the experimental test is conducted by the near-infrared Doppler asymmetric spatial heterodyne interferometer. Under the ambient temperature fluctuation of 0.27 ℃, the change of phase slope is 670 mrad/m, and the phase-drift fluctuation range of interferograms is 8.9 mrad. Upon the phase-drift correction of interferograms, the phase drift of asymmetric quantities is about 4.7 mrad, and the root mean square is 0.98 mrad, with the equivalent wind speed measurement error of 0.81 m/s. According to the bias experiment on temperature, the rate of phase-drift change of asymmetric quantities with temperature is -493 mrad/℃. © 2022, Chinese Lasers Press. All right reserved.
  Accession Number: 20224012823030
• Record 281 of
  
  Title:High time-resolution detector based on THz pulse accelerating and scanning electron beam
  
  Author(s):Li, Hang(1,2,3); Chen, Ping(1); Tian, Jin-Shou(1); Xue, Yan-Hua(1); Wang, Jun-Feng(1); Gou, Yong-Sheng(1); Zhang, Min-Rui(1); He, Kai(1); Xu, Xiang-Yan(1); Sai, Xiao-Feng(1); Li, Ya-Hui(1); Liu, Bai-Yu(1); Wang, Xiang-Lin(1); Xin, Li-Wei(1); Gao, Gui-Long(1); Wang, Tao(1); Wang, Xing(1); Zhao, Wei(1)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 71  Issue: 2  DOI: 10.7498/aps.71.20210871  Published: January 20, 2022  
  Abstract:Terahertz pulses accelerating and scanning electron beam can break through the limitation of accelerating electric field between cathodes and grids in traditional streak tubes, thus reducing the time dispersion and enhancing the temporal resolution of time-scanning detectors. Based on this new technology, in this paper an ultra-small structured time-resolved detector with no focusing pole is designed. The terahertz pulse coupling/enhancing device suitable for acceleration zone and scanning zone is designed and optimized. The enhanced coefficient of the terahertz pulse electric field in the device reaches 9.39. In the paper, the relationship between time dispersion in acceleration zone and the moment of electrons emission is analyzed theoretically. We also analyze the influence of space charge effect on time dispersion. The electronic trajectory tracking is used to calculate and analyze the time dispersion of this detector, and finally the time resolution is better than 50fs. Copyright © 2022 Acta Physica Sinica. All rights reserved.
  Accession Number: 20220611600356
• Record 282 of
  
  Title:Influence on imaging performance and evaluation of Wolter-I type mandrel fabrication errors
  
  Author(s):Wu, Kaiji(1); Ding, Fei(1); Yang, Yanji(2); Li, Duo(1); Qiao, Zheng(1); Qiang, Pengfei(3); Wang, Bo(1)
  Source: Applied Optics  Volume: 61  Issue: 22  DOI: 10.1364/AO.460960  Published: August 1, 2022  
  Abstract:The electroforming replication process has been widely used in the fabrication of nested x-ray telescopes. The imaging performance of the mirrors is determined largely by the shape accuracy of the mandrels. To predict the imaging performance of mirrors replicated frommandrels with different parameter and fabrication errors, a special Monte Carlo ray tracing model is established and verified by experiments. Then, based on ray tracing numerical calculation, the influence of each major fabrication error is discussed. Furthermore, according to the results obtained by the simulation of slope error, a method for evaluating the relationship between the mandrel full-band errors and imaging quality is proposed and then verified by experiments. The results show that the power spectral density (PSD) reference given by the method can well reflect the quality of the mandrels, and guide the fabrication process. ©2022 Optica Publishing Group.
  Accession Number: 20223412623215
• Record 283 of
  
  Title:Multimode quantum squeezing generation via multiple four-wave mixing processes within a single atomic vapor cell
  
  Author(s):Qin, Wenqiang(1,2,3); Li, Jiawei(1,2,3); Chen, Zhili(1); Liu, Yuliang(1); Wei, Jiajia(1); Bai, Yonglin(2,3); Cai, Yin(1); Zhang, Yanpeng(1)
  Source: Journal of the Optical Society of America B: Optical Physics  Volume: 39  Issue: 10  DOI: 10.1364/JOSAB.465028  Published: October 1, 2022  
  Abstract:Multimode quantum squeezing plays an essential role in the fields of quantum metrology and quantum information. In this paper, we first construct a three- and four-mode energy-level cascaded four-wave mixing system in a single 85Rb vapor, and then analyze the quantum properties of the produced states, including the covariance matrix and the intensity squeezing with 11 possible Hamiltonians. In addition, the dressing field is applied to modulate the nonlinear susceptibility and the multimode quantum states. Our scheme allows active modulation of the quantum states integrated within the generation step, without the need for any post-operation of the optics. The mode number of the states also can be extended using more pump fields and the dressing effect. Our study provides a promising candidate to generate multimode quantum states and multimode quantum squeezing within a quantum device involved in the construction of practical quantum networks. © 2022 Optica Publishing Group.
  Accession Number: 20224513067968
• Record 284 of
  
  Title:Distance and depth modulation of Talbot imaging via specified design of the grating structure
  
  Author(s):Zhang, Zhenghui(1); Lei, Biao(1); Zhao, Guobo(1); Ban, Yaowen(1); Da, Zhengshang(2); Wang, Yishan(2); Ye, Guoyong(3); Chen, Jinju(4); Liu, Hongzhong(1)
  Source: Optics Express  Volume: 30  Issue: 7  DOI: 10.1364/OE.449807  Published: March 28, 2022  
  Abstract:For positioning Talbot encoder and Talbot lithography, etc., properties manipulation of Talbot imaging is highly expected. In this work, an investigation on the distance and depth modulation of Talbot imaging, which employs a specially designed grating structure, is presented. Compared with the current grating structure, the proposed grating structure is characterized by having the phase layers with uneven thicknesses. Such a specific structural design can cause the offset of Talbot image from its nominal position, which in turn generates the spatial distance modulation of self-imaging and imaging depth expansion. Theoretical analysis is performed to explain its operating principle, and simulations and experiments are carried out to demonstrate its effectiveness. © 2022 Optica Publishing Group.
  Accession Number: 20221211827736
• Record 285 of
  
  Title:Variable Curvature Mirror with Variable Thickness and Its Application in Space-Borne Optical Camera
  
  Author(s):Zhao, Hui(1); Xie, Xiaopeng(1); Gao, Limin(2); Fan, Xuewu(1); Xu, Liang(3); Ma, Zhen(3); Pei, Yongle(4)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 42  Issue: 17  DOI: 10.3788/AOS202242.1723002  Published: September 10, 2022  
  Abstract:A variable curvature mirror is a kind of active optical element. By changing its curvature radius, the corresponding wave-front could be dynamically controlled. First of all, the current situation and development trend of variable curvature mirrors are summarized systematically. After that, the physical model of deformation of variable curvature mirrors with variable thickness is established and the capability of this kind of variable curvature mirror in generating large saggitus and maintaining good surface figure accuracy is proven through numerical simulation and experiments. Finally, the application of variable curvature mirrors with variable thickness in space optical cameras is explored from three aspects. In the first place, in order to satisfy the requirement for the super large saggitus variation required by realizing large magnification ratio zoom imaging, a finite element alternating (FEA) based optimization procedure by incorporating high-order spherical deformation is designed, and the mirror with the saggitus variation approaching 1 mm is obtained. In the second place, aiming at the requirements of focusing accuracy and speed in space camera imaging, a high-precision large dynamic focusing method based on sub-mirror variable curvature mirrors is proposed. In the third place, a coding imaging method using a variable curvature secondary mirror to scan quickly along the optical axis during integration time is proposed. © 2022, Chinese Lasers Press. All right reserved.
  Accession Number: 20224012823590
• Record 286 of
  
  Title:Laser Far-Field Focal Spot Measurement Method Based on Multistep Phase Retrieval
  
  Author(s):Xiaoyi, Chen(1,2); Yaxuan, Duan(1); Zhengzhou, Wang(1); Suochao, Yuan(1); Zhengshang, Da(1)
  Source: Zhongguo Jiguang/Chinese Journal of Lasers  Volume: 49  Issue: 7  DOI: 10.3788/CJL202249.0704002  Published: April 10, 2022  
  Abstract:Objective The intensity distribution of the laser far-field focal spot is an essential index for measuring the quality of laser beams. It is also the main parameter that reflects the laser beam' s ability to enter the hole in the inertial confinement fusion system. How to measure the intensity distribution of the laser far-field focal spot with high precision determines the evaluation result of the overall performance of the laser system. It is of great guiding significance in the theoretical design stage, development stage, or final stage of practical operation of the laser device. Direct measurement methods of far-field focal spots include the long-focal-length imaging, array camera, and schlieren methods. The long-focal-length lens imaging method is limited by the linear response range of the detector. The array camera method uses a wedge, which introduces additional optical path difference and wave aberration. The schlieren method measures the main lobe and side lobe of the focal spot separately, which is easily affected by the measured environment and noise. The Shack-Hartmann wavefront measurement is an indirect measurement method and causes the loss of middle and high frequency information due to its frequency response characteristics. To achieve a high-precision measurement of far-field focal spot, this paper proposes a method based on multistep phase retrieval for measuring far-field focal spots. Theoretically, a focal spot reconstruction model based on multistep phase retrieval is derived. Then, the chirp-z transform (CZT) is introduced to solve the problem of under-sampling in calculating focal spots. Compared with the traditional fast Fourier transform (FFT) with zero-padding, using CZT to calculate the focal spot avoids calculation redundancy. The proposed method has a higher measurement accuracy of a focal spot than the traditional long-focal-length lens imaging method. Methods The proposed laser far-field focal spot measurement method based on multistep phase retrieval can be divided into two parts. First, the multistep phase retrieval method is used to obtain the near-field complex amplitude of the object plane. Then, it is substituted into the reconstructed model of the laser far-field focal spot and uses CZT to obtain the intensity distribution of the laser far-field focal spot. Meanwhile, considering that the multistep phase retrieval method will introduce distance errors due to the translation of the detector, the quantum genetic algorithm (QGA) is used to optimize the distance errors. The laser far-field focal spot reconstruction algorithm based on multistep phase retrieval is presented. We use the theoretical simulation to analyze the influence of scanning step size and the number of detection positions on the convergence of the proposed method. Thus, the optimal scanning step size and the number of detection positions are determined. Furthermore, a verification device based on a pure phase liquid crystal spatial light modulator (SLM) is set up experimentally to verify the effectiveness of the proposed method. We also compare the experimental results of the proposed method and traditional long-focal-length lens imaging method. Results and Discussions In the simulation, the laser near-field complex amplitude of the object plane is effectively retrieved. The retrieved and theoretical focal spots have the same distribution of main lobe and side lobe in the focal spot (Fig. 7). Compared with CZT, the focal spot calculated using FFT is under-sampled, and the detailed information in the focal spot is lost (Fig. 7). The power in the bucket (PIB) curves of theoretical and retrieved focal spots are completely coincident in the integral area of the entire bucket radius (Fig. 7). In the experiment, the main lobe distribution between the theoretical and retrieved far-field focal spots is consistent (Fig. 9). However, the optical components introduce small aberrations, and the surfaces of these optical components will interfere with each other, resulting in a small difference between the distribution of side lobes for the theoretical and retrieved far-field focal spots (Fig. 9). In the traditional long-focal-length lens imaging method, the introduction of lens aberrations and insufficient dynamic response range of the CCD lead to larger errors in the main lobe and side lobe of focal spots than those in the theoretical focal spot (Fig. 9). The correlation coefficient between the retrieved focal spot using the proposed method and the theoretical focal spot is 0.9976. However, the correlation coefficient between the measured focal spot using the long-focal-length lens imaging method and the theoretical focal spot is 0. 9477. This also confirms that the measurement accuracy of focal spots using the proposed method is much higher than that of the long-focal-length lens imaging method. Conclusions This paper proposes a laser far-field focal spot measurement method based on multistep phase retrieval. The effectiveness of the method is verified through theoretical simulation and experiments. The theoretical simulation results show that the near-field complex amplitude and far-field focal spot of lasers are effectively retrieved. Additionally, the PIB curves of the theoretical and retrieved focal spots are coincident. Moreover, the experimental results show that the profile of the retrieved phase is consistent with that of the theoretical phase loaded using SLM. Therefore, the retrieved and theoretical focal spots have the same distribution of the main lobe. However, there is a small difference in the side lobes because the optical components introduce small aberrations, and the surfaces of these optical components will interfere with each other. The side lobe information of focal spots using the long-focal-length lens imaging method is lost because of the limited dynamic response range in CCD. Therefore, the proposed method has higher precision of laser far-field focal spot than the traditional long-focal-length lens imaging method. The results show that the proposed method can provide a technical means for the high-precision measurement of laser far-field focal spots. © 2022 Science Press. All rights reserved.
  Accession Number: 20224513069013
• Record 287 of
  
  Title:Telecom-compatible, on-chip generation and processing of complex photon states in time and frequency
  
  Author(s):Chemnitz, Mario(1); Yu, Hao(1,9); Sciara, Stefania(1); Fischer, Bennet(1); Roztocki, Piotr(1); Crockett, Benjamin(1); Reimer, Christian(1,2); Caspani, Lucia(3); Kues, Michael(1,4); Munro, William J.(5); Chu, Sai T.(6); Little, Brent E.(7); Moss, David J.(8); Wang, Zhiming(9); Azana, Jose(1); Morandotti, Roberto(1,9)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12004  Issue:   DOI: 10.1117/12.2607224  Published: 2022  
  Abstract:We review our work on implementing integrated QFC sources based on microring resonators for on-chip generation of two- and multi-photon time-bin entangled states, d-level frequency-entangled photon pairs, and multipartite d-level cluster states. We also present our recent progress on telecom-compatible, scalable, time-entangled two-photon qubits using on-chip Mach-Zehnder interferometers (MZI) in combination with spiral waveguides. Both approaches are highly cost-effective, efficient, and practical, since we coherently manipulate the time and frequency modes through standard fiber-linked components that are compatible with off-the-shelf telecommunications infrastructures. Our work paves the way for robust sources and processors of complex photon states for future quantum technologies. © 2022 SPIE.
  Accession Number: 20222312194141
• Record 288 of
  
  Title:External Attention Based TransUNet and Label Expansion Strategy for Crack Detection
  
  Author(s):Fang, Jie(1,2); Yang, Chen(3); Shi, Yuetian(4,5); Wang, Nan(4,5); Zhao, Yang(6)
  Source: IEEE Transactions on Intelligent Transportation Systems  Volume: 23  Issue: 10  DOI: 10.1109/TITS.2022.3154407  Published: October 1, 2022  
  Abstract:Crack detection is an indispensable premise of road maintenance, which can provide early warning information for many road damages and save repair costs to a large extent. Because of the security and convenience, many image processing technique (IPT) based crack detection methods have been proposed, but their performances often cannot meet the requirements of practical applications because of the complex texture structure and seriously imbalanced categories. To address the aforementioned problem, we present an external attention based TransUNet for crack detection. Specifically, we tackle the TransUNet as the backbone of our detection framework, which can propagate the detailed texture information from shallow layers to corresponding deep layers through skip connections. Besides, the Transformer Block equipped in the second last convolution layer of the encoding component can explicitly model the long-range dependency of different regions in an image, which improves the structural representation ability of the framework and hence alleviates the interference from shadow, noise, and other negative factors. In addition, the External Attention Block equipped in the last convolution layer of the encoding component can effectively exploit the dependency of crack regions among different images, and further enhance the robustness of the framework. Finally, combined with the Focal Loss, the proposed label expansion strategy can further alleviate the category imbalance problem through transforming semantic categories of non-crack pixels distributed in the neighbors of corresponding crack pixels. © 2000-2011 IEEE.
  Accession Number: 20221211832362