2024

• Record 265 of
  
  Title:Thermal resistance investigate of copper-copper interface based on femtosecond laser periodic microstructure
  
  Author Full Names:Ning, Wang(1); Zihan, Liu(1); Hualong, Zhao(1); Xiongtao, Zhao(2); Yupeng, Zhang(2)

  Source Title:Proceedings of SPIE - The International Society for Optical Engineering

  Language:English

  Document Type:Conference article (CA)

  Conference Title:Advanced Laser Processing and Manufacturing VIII 2024

  Conference Date:October 12, 2024 - October 14, 2024

  Conference Location:Nantong, China

  Conference Sponsor:Chinese Optical Society (COS); The Society of Photo-Optical Instrumentation Engineers (SPIE)

  Abstract:With the progress of national defense science and technology, the thermal effect of components in aerospace technology has greatly hindered the operation of devices. In order to solve the problem of high interface thermal resistance between materials, a new method of femtosecond processing combined with thermal interface materials was proposed to reduce interface thermal resistance. By using the high-efficiency positioning response method and the non-material selectivity and low thermal effect of femtosecond laser, the micro-structure with low roughness is precisely machined on the surface of copper based on the laser five-axis machining system, and the internal structural roughness, depth and width of the micro-structure are characterized. Then the surface is covered with thermal interface materials to achieve the purpose of reducing the interface thermal resistance between materials. At the same time, the effect of microstructure on interface thermal resistance is simulated with simulation software. A uniform array structure was obtained on the surface of copper substrate with a roughness less than 0.3μm, and the measured linear roughness of the microstructure was 0.23μm, which was consistent with the surface roughness of copper. Firstly, in order to verify that the surface heat conduction efficiency of the material with a microstructure surface is higher, the heat transfer time of the composite substrate with a microstructure is 0.0073s after simulation, which is faster than that of the composite substrate without a microstructure. Then, the thermal conductivity of the composite substrate with low roughness is 355 W·m-1·K-1, while that of the composite substrate with high roughness is 325 W·m-1·K-1. Through the ultrafine processing, the heat transfer efficiency of the prepared composite substrate is increased by 17%, and the heat transfer efficiency is higher with lower roughness, which provides a research basis for high energy consumption devices. © 2024 SPIE.

  Affiliations:(1) Xi'an Institute of Optics and Precision Mechanics of CAS, Xian; 710000, China; (2) Innovation & Research Institute of HIWING Technology, Academy of CASIC, Beijing; 100074, China

  Publication Year:2024

  Volume:13234

  Article Number:132340X

  DOI Link:10.1117/12.3040482

  数据库ID（收录号）:20245117550512
• Record 266 of
  
  Title:Redundant-Coded Masked Grid Pattern for Full-Sky Star Identification
  
  Author Full Names:Liao, Jiawen(1); Wei, Xin(2); Niu, Axi(3); Zhang, Yanning(3); Kweon, In So(4); Qi, Chun(5)

  Source Title:IEEE Transactions on Aerospace and Electronic Systems

  Language:English

  Document Type:Journal article (JA)

  Abstract:Full-sky autonomous star identification is one of the key technologies in the research on star sensors. As one of the classical pattern-based star identification methods, the grid algorithm has shown promising performance. Na further modified it to improve its robustness to position noise. However, the inherent alignment star mismatch and pattern inconsistency are still not solved. To address these problems, we propose a novel star identification method. Specifically, we design distance-guided redundant-coded patterns for different alignment stars to alleviate the problem of alignment star mismatch. Then, we create a masked grid pattern to address the inconsistency between the sensor pattern and the catalog pattern. The distances of the reference stars to their corresponding alignment stars are adopted to assist in choosing the correct alignment star, as well as reducing the number of catalog patterns that need to be evaluated. Experimental results on both synthesized and night sky images show that the proposed algorithm is quite robust to false stars, position noise, and magnitude noise. The identification accuracy of this algorithm is 98.43% with standard deviations of position noise is 2.0 pixels and 98.52% with standard deviations of magnitude noise is 0.5 Mv. Moreover, the algorithm obtains an average identification accuracy of 99.6% from night sky images. © 1965-2011 IEEE.

  Affiliations:(1) Chinese Academy of Sciences, Department of Xi'an Institute of Optics and Precision Mechanics, Xi'an; 710119, China; (2) Northwest Agricultural and Forestry University, College of Information Engineering, Yangling; 712199, China; (3) Northwestern Polytechnical University, School of Computer Science, Xi'an; 710072, China; (4) Korea Advanced Institute of Science and Technology, School of Electrical Engineering, Daejeon; 34141, Korea, Republic of; (5) Xi'an Jiaotong University, School of Electronics and Information Engineering, Xi'an; 710049, China

  Publication Year:2024

  Volume:60

  Issue:4

  Start Page:4343-4355

  DOI Link:10.1109/TAES.2024.3374714

  数据库ID（收录号）:20241215762514
• Record 267 of
  
  Title:Dual-parameter controlled reconfigurable metasurface for enhanced terahertz beamforming via inverse design method
  
  Author Full Names:Wu, Qi(1,2); Fan, Wen-Hui(1,2,3); Qin, Chong(1,2); Jiang, Xiao-Qiang(1,2)

  Source Title:Physica Scripta

  Language:English

  Document Type:Journal article (JA)

  Abstract:Recently, reconfigurable metasurfaces have emerged as a promising solution for wavefront manipulation in the terahertz (THz) region, providing enhanced beamforming capabilities. However, traditional single-parameter control methods fail to achieve independent phase and amplitude modulation, constraining their modulation capabilities. Meanwhile, forward design methods based on phase matching ignore the structural responses of the non-ideal unit, leading to degraded beamforming performance. Here, we introduce an electrically reconfigurable metasurface composed of bilayer graphene strips based on dual-parameter control. Full-wave simulations demonstrate independent amplitude and phase modulation, achieving the full 360° phase coverage and an adjustable amplitude range from 0 to 0.8 at 2.6 THz. To optimize beamforming performance, particularly for the responses of the non-ideal unit away from the designed frequency, we employed an inverse design method based on a hybrid evolutionary algorithm. This novel approach significantly enhances beam steering, achieving a maximum 60% increase in beam directivity and maintaining over 90% of ideal directivity across a broad frequency range from 1.6 THz to 5 THz. Especially, it achieves a maximum deflection angle of 75°. Meanwhile, the adaptability of the inverse design method is further demonstrated to various optimized objectives. For beam focusing, even with limited phase control (below 210°), this method significantly enhances the focusing quality (up to 150% enhancement) and increases the focusing efficiency from 25% to 40%. Additionally, it effectively mitigates the impact of quantized phase errors on beamforming. This research not only demonstrates potential applications in high-speed THz wireless communication and compact imaging systems but also paves the way for innovative designs in reconfigurable metasurfaces. © 2024 IOP Publishing Ltd.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an; 710119, China; (2) University of Chinese Academy of Sciences, Beijing; 100049, China; (3) Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan; 030006, China

  Publication Year:2024

  Volume:99

  Issue:6

  Article Number:065517

  DOI Link:10.1088/1402-4896/ad43c3

  数据库ID（收录号）:20242016080491
• Record 268 of
  
  Title:Ultrabroadband nonlinear enhancement of mid-infrared frequency upconversion in hyperbolic metamaterials
  
  Author Full Names:Zhang, Congfu(1,3); Wang, Zhaolu(1); Zhang, Changchang(1,3); Shi, Wenjuan(1,3); Li, Wei(1,3); Gao, Ke(1,3); Liu, Hongjun(1,2)

  Source Title:Nanoscale Horizons

  Language:English

  Document Type:Journal article (JA)

  Abstract:Metamaterials have demonstrated significant potential for enhancing nonlinear processes at the nanoscale. The presence of narrowband hot-spots and highly inhomogeneous mode-field distributions often limit the enhancement of nonlinear interactions over larger spatial scales. This has posed a formidable challenge in achieving simultaneous enhancement across a broadband spectral range, significantly constraining the potential of photonic nanostructures in enhancing nonlinear frequency conversion. Here, we propose a broadband resonant mode matching method through near-field examinations that supports the multipole modes and enables the development of an ultrabroadband-enhanced 3-5 μm mid-infrared frequency upconversion technique utilizing a hyperbolic triangular pyramidal metasurface. The gap-plasma mode of the hyperbolic metamaterial multilayer system excites narrowly high-order resonances at near-infrared pump light wavelengths, while the slow-light effect generated by the dipoles achieves ultrabroadband near-field enhancement at mid-infrared wavelengths. The symmetry breaking of the triangular structure localizes these resonant modes at the tips, enabling mode-matched modulation at different wavelengths, and thus boosting the nonlinear frequency conversion process. Our approach provides a promising platform for metasurface-based frequency conversion techniques. © 2024 The Royal Society of Chemistry.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Science, Xi’an; 710119, China; (2) Collabotative Innovation Center of Extreme Optics, Shanxi University, Taiyuan; 030006, China; (3) University of Chinese Academy of Sciences, Beijing; 100084, China

  Publication Year:2024

  Volume:9

  Issue:10

  Start Page:1792-1803

  DOI Link:10.1039/d4nh00240g

  数据库ID（收录号）:20243316882736
• Record 269 of
  
  Title:X-ray compressed ultrafast photography under the constraint of time-integrated-image for X-pinch
  
  Author Full Names:Zhou, Haoyu(1,2); Yao, Zhiming(2); Sheng, Liang(2); Song, Yan(2); Liu, Zhen(2); Han, Changcai(2); Zhu, Zijian(2); Li, Yang(2); Duan, Baojun(2); Ji, Chao(3); Wu, Jian(4); Hei, Dongwei(2); Liu, Yinong(1)

  Source Title:Optics and Lasers in Engineering

  Language:English

  Document Type:Journal article (JA)

  Abstract:This paper presents a time-integrated-image-constrained X-ray compressed ultrafast photography system for comprehensive measurement of the aluminum X-pinch evolution process. The system incorporates a pinhole and a scintillator to convert the X-ray video to fluorescence video. The fluorescence video is recorded by a compressed ultrafast photography channel and a time-integrated imaging channel respectively. By recording the fluorescence video instead of the self-emission visible light video, the long tailing effect can be significantly inhibited, which is more conducive to the image reconstruction of the compressed ultrafast photography channel. In addition, by combining the time-integrated imaging channel, the reconstruction quality is significantly improved. Based on the "Qin-I" pulsed power facility, we recorded the continuous two-dimensional X-ray evolution process of aluminum X-pinch for the first time. Our results contribute to deep insights into the temporal-spatial distribution of the X-pinch imploding plasma. It can also offer direction for the assessing of X-ray backlight photography applications at the X-pinch facility. © 2024 Elsevier Ltd

  Affiliations:(1) Department of Engineering Physics, Tsinghua University, Beijing; 100084, China; (2) National Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an; 710024, China; (3) Key Laboratory of Ultra-fast Photoelectric Diagnostics Technology, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China; (4) State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an; 710049, China

  Publication Year:2024

  Volume:183

  Article Number:108508

  DOI Link:10.1016/j.optlaseng.2024.108508

  数据库ID（收录号）:20243416890078
• Record 270 of
  
  Title:Enhancement of single-photon level signal detection based on phase sensitive amplification strategy
  
  Author Full Names:Zhang, Changchang(1,3); Wang, Zhaolu(1); Liu, Hongjun(1,2); Huang, Nan(1)

  Source Title:New Journal of Physics

  Language:English

  Document Type:Journal article (JA)

  Abstract:We investigate the ability of phase-sensitive amplification (PSA) to noiselessly amplify the preferred quadrature components of single-photon signals that are limited by phase fluctuations relative to the pump. We present a PSA enhancement strategy that is more realistic for possible experimental realization and is expected to significantly improve the detection of weak signals at the single-photon level and obtain more useful information. Our study shows that with a large PSA gain, proper transmissivity allows both direct and balanced homodyne detections to operate optimally simultaneously, and effectively improves the noise figure degradation owing to the internal losses and non-ideal detection efficiency. © 2024 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Science, Xi’an; 710119, China; (2) Collabotative Innovation Center of Extreme Optics, Shanxi University, Taiyuan; 030006, China; (3) University of Chinese Academy of Sciences, Beijing; 100084, China

  Publication Year:2024

  Volume:26

  Issue:10

  Article Number:103032

  DOI Link:10.1088/1367-2630/ad8778

  数据库ID（收录号）:20244517340981
• Record 271 of
  
  Title:Research on the spacecraft ground equivalence test assessment problem: A comprehensive assessment method combining interval-type evaluation and prospect-two-dimensional cloud
  
  Author Full Names:Ding, Wenzhe(1,2,3); Bai, Xiang(1); Wang, Qingwei(1); Yao, Huisheng(1); Liu, Jian(1); Yang, Hong(1,4)

  Source Title:Applied Soft Computing

  Language:English

  Document Type:Journal article (JA)

  Abstract:For the complex dual-attribute qualitative assessment problem of spacecraft ground equivalence tests, the paper proposes a comprehensive assessment method that integrates interval-type evaluation with prospect theory and the two-dimensional cloud model. Firstly, to reduce the difficulty of determining indicator weights, the paper adopts interval-type evaluation and obtains reasonable interval weights of each indicator under dual attributes by interval analytic hierarchy process (IAHP). Secondly, to reduce the uncertainty of assessment and achieve the transformation of interval weights to value weights, the paper combines the prospect theory to obtain the value weight of each indicator that can maximize the personality preference satisfaction of the decision-maker by maximizing the integrated prospect value. During this period, to avoid the construction of a complex score function, the theoretical gain and loss values of indicator evaluation were obtained directly from the theoretical calculation based on the location of interval evaluation results in relation to interval psychological reference points. Again, to judge the validity of the interval evaluation of indicators, the paper theoretically derives an inverse cloud generator for interval-type samples and then realizes the validity analysis of the interval evaluation of indicators based on the 3-sigma principle of clouds. Then, to solve the problem of dual-attribute assessment of equivalence tests, the paper achieves the effective assessment of spacecraft ground equivalence tests through inter-cloud aggregation and similarity calculation of two-dimensional cloud models. Finally, the application of the method in a specific assessment case verifies the feasibility, validity, and practicality of the method in this paper. © 2024 Elsevier B.V.

  Affiliations:(1) Beijing Institute of Tracking and Telecommunications Technology, Beijing; 100096, China; (2) Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China; (3) National Key Laboratory of Space Integrated Information System, Beijing; 100096, China; (4) Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing; 100094, China

  Publication Year:2024

  Volume:166

  Article Number:111882

  DOI Link:10.1016/j.asoc.2024.111882

  数据库ID（收录号）:20243817061887
• Record 272 of
  
  Title:Simulation Analysis of Key Parameters for CH4 Gas Point Source Detection Based on F-P Interferometer
  
  Author Full Names:Zhang, Qiang(1,2); Bai, Caixun(3); Fu, Di(1); Li, Juan(2); Chang, Chenguang(1); Zhao, Hengxiang(1); Wang, Sufeng(1); Feng, Yutao(1)

  Source Title:Guangzi Xuebao/Acta Photonica Sinica

  Language:Chinese

  Document Type:Journal article (JA)

  Abstract:The increase in greenhouse gases carbon dioxide and methane can directly lead to changes in the global climate and cause a significant impact on the economies of countries and human life. Methane，as the second-largest greenhouse gas on Earth，has a global warming potential 30 times higher than CO2 over a 100-year period，and its lifespan is approximately 9.1 years. At present，anthropogenic CH4 emissions primarily originate from numerous point sources. Implementing measures to reduce CH4 emissions can help decrease the rate of global warming. Therefore，it is crucial to conduct research on monitoring technologies for CH4 and investigate key carbon emission sources. Hyperspectral satellite remote sensing for detecting greenhouse gases has become a candidate technology for point source detection. It has advantages such as high viewpoint，wide field of view，the ability to achieve dynamic monitoring，obtain more precise and demand-driven information data. Utilizing remote sensing methods to monitor and provide feedback on point source emissions of greenhouse gases like methane plays a crucial role in effectively addressing climate change. Existing payload technologies in China are geared towards large satellite platforms，enabling wide-area coverage with low spatial resolution monitoring. However，traditional methods such as grating spectrometry，Michelson interferometry，and spatial heterodyne are unable to meet the efficient and high-precision monitoring requirements for small-scale anthropogenic emission sources. They struggle to achieve point source detection. Therefore，it is necessary to conduct research on satellite remote sensing carbon monitoring technologies that offer high accuracy and high spatial resolution. The Fabry-Pérot interferometry technique possesses extremely high spectral resolution，capable of discerning minute wavelength differences in the spectrum. The theoretical basis of this technique is the multi-beam equal-inclination interferometry. By using an interference ring，it is possible to directly obtain the spectral information of target light at different incident angles. By collecting the spectral information corresponding to different wavelengths of the target at different positions from multiple consecutive shots，the target spectral curve is obtained. This technique establishes a relationship between CH4 gas concentration and the depth of spectral curve notches，offering advantages in point source detection with high spectral resolution and high spatial resolution. In CH4 gas detection，the parameters of the Fabry-Pérot interferometer and the optical filter have a significant impact on detection sensitivity. Properly configuring these parameters is crucial for improving detection accuracy. This paper presents a study on a high spatial resolution method for detecting point sources of methane gas based on the principle of multi-beam interferometric spectral imaging. Firstly，the working principle and detection scheme of the methane gas detector are introduced. The system parameters of the Fabry-Pérot interferometer are designed， and a forward model for methane gas detection is established. Subsequently，the correspondence between interference signals and methane concentration，as well as the influence of instrument parameters on detection sensitivity，are analyzed. In the end，iterative optimization is performed to obtain the optimal values of various optical structural parameters. The results indicate that within the methane detection wavelength range of 1 630~1 675 nm，with a free spectral range of 12.5 nm and a spectral resolution of 0.1 nm，the optimal parameters for the Fabry-Pérot interferometer are a cavity length of 0.08 mm and an intra-cavity reflectance of 97.5%. By using a cutoff filter with a range of（1 630±4）nm ~ （1 675±4）nm，the relative change in interference signal corresponding to a 25% concentration variation of the detection source falls within the range of［0.65%，4.30%］，indicating a good detection sensitivity. The research results of this study provide a theoretical basis and technical support for high-precision. © 2024 Chinese Optical Society. All rights reserved.

  Affiliations:(1) Key Laboratory of Spectral Imaging Technology, Xi'an Institute of Optics Precision Mechanic of Chinese Academy of Sciences, Xi'an; 710119, China; (2) University of Chinese Academy of Sciences, Beijing; 100049, China; (3) School of Physics and Optoelectronic Engineering, Shandong University of Technology, Zibo; 255000, China

  Publication Year:2024

  Volume:53

  Issue:1

  Article Number:0130001

  DOI Link:10.3788/gzxb20245301.0130001

  数据库ID（收录号）:20240815582116
• Record 273 of
  
  Title:Wide-angle metalens array with quadratic phase for terahertz polarization detection
  
  Author Full Names:Qin, Chong(1,2); Fan, Wenhui(1,2,3); Wu, Qi(1,2); Jiang, Xiaoqiang(1,2); Yan, Hui(1,2); Ju, Pei(1)

  Source Title:Physica Scripta

  Language:English

  Document Type:Journal article (JA)

  Abstract:With the advances of micro/nano fabrication technology, metasurface has become an alternative to design functional devices for manipulating electromagnetic wave. Metalens is one of the basic electromagnetic functional devices that can be applied in various fields. Currently, polarization measurement based on metalens arrays has been widely investigated, but most of them can only work for normal incident wave due to the limited field-of-view of metalens. Herein, a dielectric wide-angle metalens array (WMA) for the terahertz polarization detection is presented. The WMA is composed of three wide-angle metalenses, each wide-angle metalens is constructed by utilizing quadratic phase profile. The angle tolerance of meta-atoms which constitute the wide-angle metalens is elucidated in detail. The WMA can decompose incident terahertz wave into four channels, and the full Stokes parameters of incident wave is determined by intensities in these four channels. Simulated results show that the WMA proposed here has excellent performance for the polarization detection within incident angle of ±40°. In addition, this WMA can also be used to detect the phase gradient of incident terahertz wave, the detection error is less than 1.1%. This WMA is promising in the fields of terahertz polarization generation, detection and imaging. © 2024 IOP Publishing Ltd.

  Affiliations:(1) State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an; 710119, China; (2) University of Chinese Academy of Sciences, Beijing; 100049, China; (3) Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan; 030006, China

  Publication Year:2024

  Volume:99

  Issue:6

  Article Number:065515

  DOI Link:10.1088/1402-4896/ad3d91

  数据库ID（收录号）:20242016074464
• Record 274 of
  
  Title:Design of Off-axis Three-mirror Optical System Based on Controlled Genetic Algorithm
  
  Author Full Names:Wang, Jiangtao(1,2,3); Wang, Hu(1,2,3); Ma, Zhanpeng(1,3); Xue, Yaoke(1,2,3,4); Wang, Xingyan(1,2,3); Lian, Jin(1,2,3)

  Source Title:Guangzi Xuebao/Acta Photonica Sinica

  Language:Chinese

  Document Type:Journal article (JA)

  Abstract:With the rapid development of optical technology，the application demand of high-performance optical systems in various fields is growing steadily. Especially in the fields of aerospace remote sensing，astronomical observation，scientific exploration and other fields，the performance requirements of optical systems are becoming more and more stringent. These systems are expected to have larger fields of view and broader detection bands. Reflective optical systems，which are free from chromatic aberration and can achieve large apertures while being lightweight，have garnered significant attention in satellite remote sensing. At present，in optical design，it is commonly used to find an initial structure that is similar to the design goal as a starting point for optimal design. The damping least squares method employed by optical design software in the optimization process is more sensitive to the selection of initial values. If the initial values are not selected properly，the optimization process may fail to converge or may converge to a local optimal solution，thereby failing to reach the global optimal solution. The initial structure of the off-axis reflection system is small and it is difficult to find the initial structure. Therefore，it is commonly used to design the coaxial system first and then optimize the off-axis system. To address this problem，this paper proposes a solution that combines traditional optical design with optimization algorithms. This solution makes up for the shortcoming that design software easily falls into local optimal solutions，so that the final optical system not only guarantees the global optimal solution to the greatest extent，but also has strict ray tracing calculations. Firstly，the relationship between system parameters and structural form，main mirror type，and imaging times is analyzed to provide a more reasonable range for parameter selection during the initial structure calculation process，thereby reducing the amount of calculation. Secondly，based on the aberration analysis of the coaxial three-mirror optical system，the initial structure of the system is calculated through a controlled genetic algorithm using the sum of the weighted third-order aberrations as the fitness function. Compared with the traditional Genetic Algorithm，which generally tends to have the characteristics of individuals with better fitness，the Controlled Genetic Algorithm also tends to select individuals with lower fitness values but can increase the diversity of the population，which is more conducive to the entire solution space. Find the optimal initial structure within the range. Compared with the method of directly substituting the constraints into the optimization software，the initial structure obtained by this method is more reasonable and the image quality is better. After the initial structure is determined，the aperture and field of view of the system are off-axis，and the field of view is gradually expanded while ensuring that the light is not blocked. Free-form surfaces are introduced to correct the asymmetric aberrations produced by the off-axis system. Compared with traditional spherical，the freeform surfaces have the characteristics of non-rotational symmetry and can be of any shape. They can correct the asymmetric aberration produced by the non-rotation symmetric optical system in the meridional direction，and ultimately achieve high-quality large field of view imaging. Taking an optical system with a field of view of 30°×20°，a focal length of 110 mm，an F number of 2.2，and an operating band of 3 to 5 μm as an example，the fringe Zernike polynomial is used to describe the free-form surface. Each term of the Zernike polynomial is related to aberrations have a direct correspondence. In the design process，not only can new higher-order terms be added during the optimization process to describe the free-form surface without affecting the coefficients of other terms，but terms with very small contributions can also be found to appropriately delete the design. The results indicate that the Optical Transfer Function（MTF）is near the diffraction limit and exceeds 0.6 at the Nyquist frequency of 25 lp/mm. The maximum Root Mean Square（RMS）spot radius value in the full field of view is about 6.3 μm，and the maximum distortion is less than 10%. Finally，the tolerance analysis was conducted，and under reasonable tolerance conditions，the image quality met the requirements. The effectiveness of this method in the design process of large-field off-axis three-mirror optical systems has been verified，and it has certain reference significance for the design of large-field off-axis optical systems. © 2024 Chinese Optical Society. All rights reserved.

  Affiliations:(1) Space Optics Technology Lab, Xi′an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an; 710119, China; (2) University of Chinese Academy of Sciences, Beijing; 100049, China; (3) Xi'an Space Sensor Optical Technology Engineering Research Center, Xi'an; 710119, China; (4) Youth Innovation Promotion Association, Beijing; 100029, China

  Publication Year:2024

  Volume:53

  Issue:12

  Article Number:1222002

  DOI Link:10.3788/gzxb20245312.1222002

  数据库ID（收录号）:20250317694675
• Record 275 of
  
  Title:Domain Adaptation of Anchor-Free object detection for urban traffic
  
  Author Full Names:Yu, Xiaoyong(1,2); Lu, Xiaoqiang(3)

  Source Title:Neurocomputing

  Language:English

  Document Type:Journal article (JA)

  Abstract:Modern detectors are mostly trained under single and limited conditions. However, object detection faces various complex and open situations in autonomous driving, especially in urban street scenes with dense objects and complex backgrounds. Due to the shift in data distribution, modern detectors cannot perform well in actual urban environments. Using domain adaptation to improve detection performance is one of the key methods to extend object detection from limited situations to open situations. To this end, this article proposes a Domain Adaptation of Anchor-Free object detection (DAAF) for urban traffic. DAAF is a cross-domain object detection method that performs feature alignment including two aspects. On the one hand, we designed a fully convolutional adversarial training method for global feature alignment at the image level. Meanwhile, images can generally be decomposed into structural information and texture information. In urban street scenes, the structural information of images is generally similar. The main difference between the source domain and the target domain is texture information. Therefore, during global feature alignment, this paper proposes a method called texture information limitation (TIL). On the other hand, in order to solve the problem of variable aspect ratios of objects in urban street scenes, this article uses an anchor-free detector as the baseline detector. Since the anchor-free object detector can obtain neither explicit nor implicit instance-level features, we adopt Pixel-Level Adaptation (PLA) to align local features instead of instance-level alignment for local features. The size of the object has the greatest impact on the final detection effect, and the object scale in urban scenes is relatively rich. Guided by the differentiation of attention mechanisms, a multi-level adversarial network is designed to perform feature alignment of the output space at different feature levels called Scale Information Limitation (SIL). We conducted cross-domain detection experiments by using various urban streetscape autonomous driving object detection datasets, including adverse weather conditions, synthetic data to real data, and cross-camera adaptation. The experimental results indicate that the method proposed in this article is effective. © 2024 Elsevier B.V.

  Affiliations:(1) Key Laboratory of Spectral Imaging Technology CAS, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Shaanxi, Xi'an; 710119, China; (2) University of Chinese Academy of Sciences, Beijing; 100049, China; (3) College of Physics and Information Engineering, Fuzhou University, Fuzhou; 350108, China

  Publication Year:2024

  Volume:582

  Article Number:127477

  DOI Link:10.1016/j.neucom.2024.127477

  数据库ID（收录号）:20241215767931
• Record 276 of
  
  Title:Topology optimization design of surface radar absorbing coatings
  
  Author Full Names:Chen, Fei(1); Zhu, Jihong(2); Li, Fu(1); Lu, Di(1); Yu, Jirui(1); Guo, Song(1); Yang, Jianfeng(1); Lv, Baogang(1); Xue, Bin(1)

  Source Title:Engineering Optimization

  Language:English

  Document Type:Article in Press

  Abstract:In this study, a topology optimization method is proposed to design the layout of the radar absorbing coatings (RACs) outside the surface. The radar cross section (RCS) of a structure with RACs is evaluated by the physical optics method. A material interpolation model oriented to the relative permittivity and relative permeability of RACs is established, while the sensitivity of the RCS with respect to the design variables is derived analytically. With the objective of minimizing the RCS at the specified incident angles and the constraint of the material usage, the strategy is implemented based on a gradient-based algorithm and the so-called three-field density method. Additionally, the phenomenon of the RCS increasing in certain regions when RACs are applied is explained in detail. Finally, the effectiveness of the proposed method is demonstrated by two numerical examples. © 2024 Informa UK Limited, trading as Taylor & Francis Group.

  Affiliations:(1) Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xian, China; (2) State IJR Center of Aerospace Design and Additive Manufacturing, Northwestern Polytechnical University, Xian, China

  Publication Year:2024

  DOI Link:10.1080/0305215X.2024.2349108

  数据库ID（收录号）:20243216815510