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Record 145 of
Title:Design and testing of the structure of the eXTP optics
Author(s):Song, Z.Y.(1); Ma, J.(1); Wang, J.(1); Zhang, A.M.(1); Wang, Y.S.(1); Yang, Y.J.(1); Jiang, W.C.(1); Chen, Y.(1); Yu, K.(1); Yang, S.(1); Xu, Y.P.(1); He, H.L.(1); Lu, F.J.(1); Zhang, S.N.(1); Basso, S.(2); Civitani, M.(2); Pareschi, G.(2); Sironi, G.(2); Spiga, D.(2); Cotroneo, V.(2); Tagliaferri, G.(2); Sheng, L.Z.(3); Yan, Y.Q.(3); Qiang, P.F.(3); Zhao, B.S.(3)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12181 Issue: DOI: 10.1117/12.2629781 Published: 2022
Abstract:The abbreviation "eXTP" represents the enhanced X-ray timing and polarimetry, which is a key science mission initiated by the Chinese scientists, designed to study the state of matter under extreme conditions of density, gravity and magnetism [1]. Various payloads would be on board of the satellite. The SFA, namely the Spectroscopy Focusing Array, consisting of 9 identical X-ray telescopes working in the energy range of 0.5-10 keV, will be the focus here [1]. SFA has a field-of-view of 12 arcmin for each and a collecting area of 900 cm2 and 550 cm2 for each at 2 keV and 6 keV respectively [1]. This paper starts with a brief introduction of the general optics, and then goes across some important design aspects. It covers contents from the structural and thermal designs to the CAE analyses as well as the current status. The large diameter and huge focal length of the optics will definitely bring big issues to the robustness of the carrying structure under the severe conditions given by the launcher. According to the current design, the mirror assembly will have 3 feet and 24 spokes. Vibration tests were already performed on a few prototypes by IHEP, and a preliminary evaluation on the feasibility of the design has been achieved. It clearly stated that the current design with only a single spider can probably survive the vibration tests assuming a compromised test condition somewhere. CAE models were adjusted thereafter to match the test results, which could be used for further assessments in a near future. Of course, there are always uncertainties associated with our arguments. More detailed prototypes with mechanically fully representative shells were still under design. Hopefully, highly reliable results could be retrieved soon. ? 2022 SPIE. All rights reserved.
Accession Number: 20224413019080
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Record 146 of
Title:Missing recognition of highway shading board based on deep convolution segmentation and correction
Author(s):Dong, Yuanshuai(1,2,3); Zhang, Yanhong(1,2,3); Hou, Yun(1,2,3); Tong, Xinlong(1,2,3); Wu, Qingquan(4); Zhou, Zuofeng(5); Cao, Yuxuan(1,2,3)
Source: 2022 IEEE Asia-Pacific Conference on Image Processing, Electronics and Computers, IPEC 2022 Volume: Issue: DOI: 10.1109/IPEC54454.2022.9777346 Published: 2022
Abstract:The lack of highway shading panels poses a major hidden danger to driving safety. It is urgent to study a method that can automatically detect the disease of the anti-glare panel and provide help for the maintenance of traffic safety auxiliary facilities. In the method for identifying the absence of shading panels on highways based on deep convolutional image segmentation and correction, the PointRend model based on deep convolutional networks (CNN) is first used to achieve the pixel-level fine segmentation of the shading plate area, and then the multiple images in the same image are segmented. A shading plate area, on the largest outer polygon estimated by the convex hull algorithm, the optimal outer quadrilateral is determined according to the distance between the vertices, and then the shading plate area correction is completed by affine transformation, and finally through the image one-dimensional projection mapping and adjacent shading The distance correlation between the boards realizes the identification and positioning of the missing light-shielding board. The highway shading plate missing recognition method based on deep convolution image segmentation and correction uses the vertex distance to quickly determine the external quadrilateral, which is suitable for estimating the shape of the area in a dynamic scene. After actual testing and verification, it can accurately and efficiently identify the disease of the anti-glare plate. Compared with traditional image segmentation methods, the method using the PointRend target segmentation model has better segmentation quality for target details, and it is more robust when dealing with background interference. ? 2022 IEEE.
Accession Number: 20222412229316
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Record 147 of
Title:Calibration Error Prediction: Ensuring High-Quality Mobile Eye-Tracking
Author(s):Li, Beibin(1,2); Snider, J.C.(3); Wang, Quan(4); Mehta, Sachin(5); Foster, Claire(6); Barney, Erin(3); Shapiro, Linda(1); Ventola, Pamela(7); Shic, Frederick(3,8)
Source: Eye Tracking Research and Applications Symposium (ETRA) Volume: Issue: DOI: 10.1145/3517031.3529634 Published: June 8, 2022
Abstract:Gaze calibration is common in traditional infrared oculographic eye tracking. However, it is not well studied in visible-light mobile/remote eye tracking. We developed a lightweight real-time gaze error estimator and analyzed calibration errors from two perspectives: facial feature-based and Monte Carlo-based. Both methods correlated with gaze estimation errors, but the Monte Carlo method associated more strongly. Facial feature associations with gaze error were interpretable, relating movements of the face to the visibility of the eye. We highlight the degradation of gaze estimation quality in a sample of children with autism spectrum disorder (as compared to typical adults), and note that calibration methods may improve Euclidean error by 10%. ? 2022 Owner/Author.
Accession Number: 20222612267177
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Record 148 of
Title:Multi-Level Alignment Network for Cross-Domain Ship Detection
Author(s):Xu, Chujie(1,2); Zheng, Xiangtao(1); Lu, Xiaoqiang(1)
Source: Remote Sensing Volume: 14 Issue: 10 DOI: 10.3390/rs14102389 Published: May-2 2022
Abstract:Ship detection is an important research topic in the field of remote sensing. Compared with optical detection methods, Synthetic Aperture Radar (SAR) ship detection can penetrate clouds to detect hidden ships in all-day and all-weather. Currently, the state-of-the-art methods exploit convolutional neural networks to train ship detectors, which require a considerable labeled dataset. However, it is difficult to label the SAR images because of expensive labor and well-trained experts. To address the above limitations, this paper explores a cross-domain ship detection task, which adapts the detector from labeled optical images to unlabeled SAR images. There is a significant visual difference between SAR images and optical images. To achieve cross-domain detection, the multi-level alignment network, which includes image-level, convolution-level, and instance-level, is proposed to reduce the large domain shift. First, image-level alignment exploits generative adversarial networks to generate SAR images from the optical images. Then, the generated SAR images and the real SAR images are used to train the detector. To further minimize domain distribution shift, the detector integrates convolution-level alignment and instance-level alignment. Convolution-level alignment trains the domain classifier on each activation of the convolutional features, which minimizes the domain distance to learn domain-invariant features. Instance-level alignment reduces domain distribution shift on the features extracted from the region proposals. The entire multi-level alignment network is trained end-to-end and its effectiveness is proved on multiple cross-domain ship detection datasets. ? 2022 by the authors. Licensee MDPI, Basel, Switzerland. otv.
Accession Number: 20222212170262
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Record 149 of
Title:A Dual-Position Loop LLADRC Control Method Based on Harmonic Gear Drive
Author(s):Cao, Yu(1,2,3,4); Wang, Fan(1,4); Li, Xin(1,4); Su, Xiuqin(1,4); Guo, Shan(1); Han, Junfeng(1,4); Xie, Meilin(1,4); Wang, Lei(1); Feng, Xubin(1,4)
Source: Mathematical Problems in Engineering Volume: 2022 Issue: DOI: 10.1155/2022/9434247 Published: 2022
Abstract:High-resolution imaging has become a development trend and is widely used in military and civil fields. As the carrying equipment of imaging system, the speed stability of tracking turntable is the basis of high-resolution and stable imaging. At present, in the aerospace field, there are high requirements for peak power dissipation and holding torque, so flexible joints such as harmonic gear drive are mostly used to realize the function. The characteristics of flexible load have a great impact on the characteristics of motion control, which is easy to cause mechanical resonance, lead to system instability, and have a great impact on speed stability and position tracking accuracy. Therefore, it is necessary to study the servo system of flexible load. In order to solve the problems of high-precision position control and speed stability at low speed of flexible turntable with uncertain load, on the one hand, we comprehensively consider the advantages and disadvantages of semi-closed-loop and full closed-loop control and design a dual-position loop feedback control system combined with the analysis of dynamic equation to realize speed stability and high-precision position control. On the other hand, according to the requirements of the speed stability at low speed of the turntable, the tracking differentiator (TD) is designed innovatively through the language three-point interpolation subdivision and five-point pre-deduction calculation method. Finally, a dual-position loop LLADRC (language linear active disturbances rejection controller) control method based on harmonic gear drive is studied. By comparing the semi-closed loop, dual-position loop, dual-position loop LADRC (linear active disturbances rejection controller, ADRC), and dual-position loop LLADRC methods through simulation analysis, it can be shown that the double position LLADRC control method is obviously superior to other schemes in terms of rapidity, speed stability at low speed, and position tracking accuracy. The theoretical research is verified by experimental test. When the given speed is 0.1°/s, taking the pitch axis as an example, the pitch speed error is 0.0039°/s (3σ). When the maximum speed of the given curve is 20°/s and the maximum acceleration is 16°/s, the position tracking error is 0.0025° (3σ). This control method solves the problems of system instability and low-speed stability in high-precision control of turntable system based on harmonic gear drive and provides a method for high-precision control of high-resolution imaging turntable. ? 2022 Yu Cao et al.
Accession Number: 20223312565529
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Record 150 of
Title:Theoretical and Experimental Research on Spatial Performances of the Long-slit Streak Tube
Author(s):Tian, Liping(1,2); Shen, Lingbin(1); Xue, Yanhua(2); Chen, Lin(1); Li, Lili(2); Chen, Ping(2); Tian, Jinshou(2); Zhao, Wei(2)
Source: Measurement Science Review Volume: 22 Issue: 2 DOI: 10.2478/msr-2022-0007 Published: April 1, 2022
Abstract:The streak tubes are widely used in National Ignition Facility (NIF), Inertial Confinement Fusion (ICF), and streak tube imaging lidar (STIL) as radiation or imaging detectors. The spatial resolution and effective photocathode area of the streak tube are strongly dependent on its operating and geometry parameters (electron optical structure and applied voltage). Studies about this dependence do not cover the full range of the parameters. In this paper, 3-D models are developed in Computer Simulation Technology Particle Studio (CST-PS) to comprehensively calculate the spatial resolution for various parameters. Monte Carlo Sampling method (M-C method) and spatial modulation transfer function method (SMTF) are employed in our simulation. Simulated results of the optimized spatial resolution are validated by the experimental data. Finally, the radii of the photocathode (Rc) and phosphor screen (Rs) are optimized. Geometry parameters of Rc=60 mm and Rs=80 mm are proposed to optimize the streak tube performances. Simulation and experimental results show that the spatial resolution and effective photocathode area of this streak tube are expected to reach 16 lp/mm and 30 mm-length while the voltage between cathode and grid (Ucg) is 150 V. ? 2022 Liping Tian et al., published by Sciendo.
Accession Number: 20221311841586
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Record 151 of
Title:Ultra-high-linearity integrated lithium niobate electro-optic modulators
Author(s):Feng, Hanke(1); Zhang, Ke(1); Sun, Wenzhao(1); Ren, Yangming(2,3); Zhang, Yiwen(1); Zhang, Wenfu(2,3); Wang, Cheng(1)
Source: Photonics Research Volume: 10 Issue: 10 DOI: 10.1364/PRJ.464650 Published: October 1, 2022
Abstract:Integrated lithium niobate (LN) photonics is a promising platform for future chip-scale microwave photonics systems owing to its unique electro-optic properties, low optical loss, and excellent scalability. A key enabler for such systems is a highly linear electro-optic modulator that could faithfully convert analog electrical signals into optical signals. In this work, we demonstrate a monolithic integrated LN modulator with an ultra-high spuriousfree dynamic range (SFDR) of 120.04 dB · Hz4/5 at 1 GHz, using a ring-assisted Mach-Zehnder interferometer configuration. The excellent synergy between the intrinsically linear electro-optic response of LN and an optimized linearization strategy allows us to fully suppress the cubic terms of third-order intermodulation distortions (IMD3) without active feedback controls, leading to ~20 dB improvement over previous results in the thin-film LN platform. Our ultra-high-linearity LN modulators could become a core building block for future large-scale functional microwave photonic integrated circuits by further integration with other high-performance components like low-loss delay lines, tunable filters, and phase shifters available on the LN platform. ? 2022 Chinese Laser Press.
Accession Number: 20224913207324
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Record 152 of
Title:Quantitative simulating experiment of atmospheric turbulence scintillation for light field imaging
Author(s):Cheng, Zhiyuan(1,2); Ma, Qing(3); Li, Zhiguo(1,2); Xia, Aili(1); Ji, Zhou(4)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12169 Issue: DOI: 10.1117/12.2625847 Published: 2022
Abstract:The laser coherent field imaging system emits multiple beams of laser from earth to space, and the laser scans remote space target by passing through turbulent atmosphere. Turbulent atmosphere is a key factor affecting imaging quality of the coherent field imaging system. Aiming at quantitative simulating of degradation imaging effect caused by atmospheric scintillation, the quantificational simulating experiment platform of atmosphere scintillation is established. Based on the simulating platform, the effect of different intensity turbulence on imaging quality is quantificationally researched. The research draws the conclusion that the greater fluctuation of atmosphere turbulence is, the more serious the degradation of imaging quality is. Thus, in order to improve the imaging quality, the turbulent atmosphere scintillation need to be restrained by signal processing method in the following research. The study provides a achievable quantitative simulating method of turbulent air scintillation for analyzing degradation imaging quality caused by the turbulent atmosphere scintillation. ? 2022 SPIE
Accession Number: 20221611967796
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Record 153 of
Title:Realization of multi-point laser target detection algorithm based on DM6437
Author(s):Bu, Fan(1); Yao, Dalei(1); Wang, Li(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12169 Issue: DOI: 10.1117/12.2622178 Published: 2022
Abstract:In view of the background interference of the current multi-point laser target source positioning detection system, positioning accuracy and real-time performance need to be improved. Based on the DM6437 hardware platform, an embedded multi-point laser target positioning system is designed. The collection of image information is completed by CMOS camera and TVP5158 chip. The DM6437 chip realizes tasks such as algorithm processing and data transmission. Experimental results show that the target location algorithm based on threshold and shape effectively removes the interfering light source in the image background. Therefore, the accuracy of laser target location is greatly improved. The positioning system based on the DSP hardware platform is small in size, stable in operation, and has high application promotion value. ? 2022 SPIE
Accession Number: 20221611967902
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Record 154 of
Title:A new off-axis Gregorian mechanical structure and its alignment method
Author(s):Fu, Xing(1); Lei, Yu(1); Cao, Mingqiang(1); Yin, Yamei(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12166 Issue: DOI: 10.1117/12.2617928 Published: 2022
Abstract:As for the conventional off-axis telescope system structure, the primary and secondary mirror are mostly fixed. The alignment process lacks adjustment mechanism. In addition, the off-axis system has no rotational symmetry which increases the difficulty of alignment and makes the cycle longer. In order to solve the above problems, an off-axis telephoto system structure is designed. The primary mirror has a four degree-of-freedom adjustment mechanism can be fine-tuned manually. The secondary mirror is driven by 6-aixs motion hexapod electrically. At the same time, perturbation analysis is carried out for this optical system. The sensitivity matrix between misalignments of second mirror and aberration coefficients is obtained. Based on the matrix, adjustment strategy is proposed [1-9]. Finally, the effectiveness of the designed structure and adjustment strategy is verified by experiments.The detailed process is described below. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
Accession Number: 20220911734996
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Record 155 of
Title:Facet passivation process of high-power laser diodes by plasma cleaning and ZnO film
Author(s):Lan, Yu(1,2); Yang, Guowen(1,2,3); Zhao, Yuliang(1,2); Liu, Yuxian(1,2); Demir, Abdullah(4)
Source: Applied Surface Science Volume: 596 Issue: DOI: 10.1016/j.apsusc.2022.153506 Published: September 15, 2022
Abstract:Passivation of dangling bonds at the cleaved mirror facet and its durability are fundamental features of semiconductor lasers to obtain reliable operation with a long device lifetime. The high non-radiative recombination activity of the surface states needs to be controlled to prevent the Fermi level pinning before the deposition of mirror coating materials. Here, we report the incorporation of plasma cleaning of the facet and ZnO film as a passivation layer for the fabrication of high-power semiconductor lasers. The Argon plasma cleaning process was investigated to eliminate surface contamination without damaging the cavity surface. The ZnO passivation films were systematically studied by varying the chamber pressure and sputtering power of the radio frequency (RF) sputter coating process. We obtained homogeneous and dense ZnO films with high surface quality and optical absorption coefficient of zero. By incorporating the optimum plasma cleaning and passivation layer parameters, GaAs-based laser devices with significantly improved catastrophic optical mirror damage (COMD) power were achieved. COMD threshold was increased from 11.9 W to 20.7 W. The life test results demonstrate no failure for facet cleaned and passivated devices for more than 500 h, confirming the long-term effectiveness of the process for actual device integration. ? 2022 Elsevier B.V.
Accession Number: 20222112147863
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Record 156 of
Title:48 W Continuous-Wave Output From a High- Efficiency Single Emitter Laser Diode at 915 nm
Author(s):Liu, Yuxian(1,2); Yang, Guowen(1,2,3); Zhao, Yongming(3); Tang, Song(3); Lan, Yu(1,2); Zhao, Yuliang(1,2); Demir, Abdullah(4)
Source: IEEE Photonics Technology Letters Volume: 34 Issue: 22 DOI: 10.1109/LPT.2022.3207786 Published: November 15, 2022
Abstract:Improving the power and efficiency of 9xx-nm broad-area laser diodes has a great help in reducing the cost of laser systems and expanding applications. This letter presents an optimized epitaxial structure with high power and conversion efficiency. Laser diodes with 230 $\mu \text{m}$ emitter width and 5 mm cavity length deliver continuous-wave output power up to 48.5 W at 48 A, 30 °C, the highest power reported for 9xx-nm single emitter lasers so far. The slope efficiency is as high as 1.23 W/A due to a low internal optical loss of 0.31 cm-1 and a high internal efficiency of 96%. The maximum power conversion efficiency reaches 72.6% at 15.3 W and 67.3% at the operating power of 30 W under a heatsink temperature of 25 °C. Life test results show no failure in 1000 hours for 55 laser diodes. ? 1989-2012 IEEE.
Accession Number: 20224112870223
