2019
2019
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Record 373 of
Title:Structural design of zoom system based on linear motor
Author(s):Yang, Xiaofan(1,2); Yang, Hongtao(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11341 Issue: DOI: 10.1117/12.2543277 Published: 2019Abstract:The shooting mode of camera system has evolved from fixed focus to zoom photography. And compared with the fixed-focus photography, the zoom system not only has fast field of view switching function, but also has a strong ability in the pursuit of extreme detail resolution. The newly proposed linear motor-driven zoom technology completely eliminates some inherent drawbacks of the traditional method. Based on this method, this paper focuses on an achievable mechanical structure of linear zoom camera. The relative positions of the four lens components are reasonably arranged, and two stepping motors are selected as the power sources. Modal analysis is used to ensure that the fundamental frequency of optimized system is reasonable. The experimental results show that the fundamental frequency is increased from 310.63 Hz to 544.4 Hz, so the optimized structure can avoid the oscillation frequency of external devices. Considering the harsh engineering environment of zoom camera, the thermal deformation and displacement parameters under the impact of high and low temperature loads need to be tested urgently. According to the total length of this system and deformation of the front and rear fixed groups, we can roughly get the offset value of the optical axis. The final analysis results show that the off-angle of the optical axis in the specified direction does not exceed 50 μrad, and initially meets the design specifications. ? 2019 SPIE.Accession Number: 20200408063349 -
Record 374 of
Title:Auto-focus algorithm based on improved SML evaluation function
Author(s):Ma, Xiaoyu(1,2); Li, Qiaoling(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11338 Issue: DOI: 10.1117/12.2545624 Published: 2019Abstract:The traditional spatial domain sharpness evaluation functions usually have a larger amount of calculation, and the calculation time is relatively longer. Besides, its anti-noise ability is weak, and it is easy to be disturbed by the background factors in the image. The above problems will have an impact on the real-time, sensitivity and reliability of the auto-focus system. In order to overcome these shortcomings, an improved SML sharpness evaluation function combined with threshold is proposed in this paper. This algorithm improve the SML function firstly, and make full use of the edge information of the image. Then a threshold is introduced to distinguish the edge points from non-edge points. So it can not only highlight the edge information while restraining the noise and the flat area in the background of the image, but also can reduce the calculation amount of the evaluation function and improve the real-time performance of the auto-focusing system. Finally verifies the effect of the improved evaluation function based on the simulation experiments. The results show that the algorithm proposed in this paper has better sensitivity and anti-noise ability, and can evaluate the sharpness of defocused images accurately and steadily. ? 2019 copyright SPIE. Downloading of the abstract is permitted for personal use only.Accession Number: 20200308056974 -
Record 375 of
Title:Research on mirror surface shape of space camera fitting based on SVD
Author(s):Huang, Tuo(1,2); Chen, Rong-Li(1); Chu, Chang-Bo(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11341 Issue: DOI: 10.1117/12.2542929 Published: 2019Abstract:Large-aperture optics mirror is one of the high resolution space camera's key components. The mirror surface shape accuracy which is subjected to external loadings can be obtained through fitting mirror surface shape. Zernike polynomials is widely used in fitting mirror surface shape due to the outstanding advantages, such as high precision and good convergence.Two methods of fitting mirror surface shape via Zernike polynomials are introdeced in this paper, namely, mirror surface deformation fitting and mirror surface shape fitting directly. Taking spherical mirror for example, the relation between the number of terms in Zernike polynomials and the fitting precision is investigated. During fitting mirror surface shape, the constructed normal equations are ill-conditioned. Reliable results cannot be obtained via the normal equation method. Singular value decomposition (SVD) method is presented to solve the abnormal equations in this paper. Through calculating the PV value and the RMS value between the fitting mirror surface and the standard spherical mirror surface, the influence of Zernike polynomials terms on the fitting precision is investigated. In the end, a design example is tested to show effectiveness of the proposed method. By fitting a deformed spherical mirror surface shape under the load condition of 1g gravity using 28-term Zernike polynomials, achieving the fitting residual, the PV value is 19.7nm and the RMS value is 3.97nm. ? 2019 SPIE.Accession Number: 20200408063343 -
Record 376 of
Title:The role of transition dipole phase in atomic attosecond transient absorption from the multi-level model
Author(s):Yuan, Guanglu(1); Jiang, Shicheng(1); Wang, Ziwen(1); Hua, Weijie(1); Yu, Chao(1); Jin, Cheng(1,2); Lu, Ruifeng(1,3)Source: Structural Dynamics Volume: 6 Issue: 5 DOI: 10.1063/1.5124441 Published: September 1, 2019Abstract:Based on a multilevel model considering enough bound electronic states of atoms, we theoretically study the role of the transition dipole phase (TDP) in the attosecond transient absorption (ATA) spectrum of helium in intense laser fields. By solving the stationary Schr?dinger equation with B-spline basis sets, we first calculate the transition dipole moments with well-defined phases between the bound states. Using the modified multilevel model, we reveal that the TDP plays an important role in determining the spectral structures if two or more paths populate the excited states from the ground state. Our multilevel model with the accurate TDP is convenient to address the origin of atomic ATA spectral structures by freely removing or adding specific electronic states and has been justified by comparing with the ATA spectra via directly solving the time-dependent Schr?dinger equation. Hopefully, further incorporating macroscopic propagation into the model will provide indepth physical insights into experimental ATA spectra. ? 2019 Author(s).Accession Number: 20201308349043 -
Record 377 of
Title:Mid-Infrared Emission of Transition Metal Co2+-Doped ZnSe Nanocrystals at Room Temperature via Hydrothermal Preparation
Author(s):Chen, Meiling(1,2); Cui, Xiaoxia(1); Xiao, Xusheng(1,2); Xu, Yantao(1,2); Cui, Jian(1,2); Guo, Junjiang(1,2); Liu, Chao(3); Guo, Haitao(1)Source: ACS Applied Nano Materials Volume: 2 Issue: 5 DOI: 10.1021/acsanm.9b00307 Published: May 24, 2019Abstract:A series of Co2+:ZnSe and Co2+:ZnSe/ZnSe nanocrystals emitting mid-infrared (mid-IR) fluorescence centered at around 3.4 and 4.7 μm were successfully synthesized via a simple hydrothermal method. The core/shell structure and post-heat treatment under reducing atmosphere were adopted to decrease the nanocrystal's surface quenching centers and defects and improve the mid-IR photoluminescence. By analysis of the X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, Fourier transform IR, absorption, and mid-IR emission measurements of serial concentrations of Co2+-doped ZnSe nanocrystals, the crystal phase, grain size, core/shell structure, distribution of Co2+ ions, impurities on the surface, and mid-IR emission performance were investigated in detail. By use of optimum Co2+ concentration, core/shell structure construction, and proper post-heat treatment, the mid-IR emission intensities of nanocrystals were enhanced by an order of magnitude, and the nanocrystals showed excellent dispersibility. These high-quality optically active nanomaterials have potential uses in mid-IR devices such as composite fiber amplifiers and hot-pressed ceramic laser materials. ? 2019 American Chemical Society.Accession Number: 20193507364564 -
Record 378 of
Title:The influence of CCD undersampling on the encircled energy of SVOM-VT
Author(s):Xue, Xun(1,2,3); Zhang, Chunmin(1,3); Zhao, Jianke(2); Zhou, Yan(2); Liu, Shangkuo(2); Kewei, E.(2); Li, Kun(2); Wang, Zhengfeng(2); Li, Jing(2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11341 Issue: DOI: 10.1117/12.2539072 Published: 2019Abstract:SVOM-VT has entered the initial phase development stage, and encircled energy is its key performance index. In the development process, it is necessary to determine the encircled energy of the optical lens stage and the system stage. The image recording of a CCD detector includes two imaging processes: one is the pixel integration imaging process, in which the output signal of each pixel is proportional to the area integration of the incident light intensity on the surface of the pixel; the other is the discrete sampling process, in which the continuous graphical object is sampled discretely at the sampling interval of the center distance of the pixel. Based on the data of SVOM-VT, the effect of CCD under-sampling on the encircled energy of detection camera is characterized by simulation and test. Imaging process of CCD pairs of scattered speckles from the lens is a two-dimensional discrete sampling process, as well as the sampling process of discrete signals. This process will lead to low-frequency noise (under-sampling noise) in the sampling of high-frequency signals by CCD detectors, resulting in spectrum aliasing (low-frequency signal distortion) of image signals. Intuitively, the original image is broadened. When the sampling density is increased, this will not be the case. ? 2019 SPIE.Accession Number: 20200408063318 -
Record 379 of
Title:Design of CPA reflective mirror in space laser communication via multi-objective optimization
Author(s):Song, Yang(1); Hu, Yongming(1); Chai, Wenyi(1); Ye, Jing(1,2); Xin, Wei(1); Hu, Bin(1,2); Wang, Chenjie(1,3)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11209 Issue: DOI: 10.1117/12.2542590 Published: 2019Abstract:The research on space laser communication has become a hotspot in recent years. The research trend of it is high speed transferring, networking and integration. Integration design means that the structure should be compact and reliable. CPA (Coarse Pointing Assembly) is an important component in space laser communication system. The paper makes design of CPA reflective mirror. On one hand, it is expected that the reflective mirror is as light as possible with small size. On the other hand, it is expected that the structure is reliable with high stiffness. These two aspects are contradict. And several factors make influence on these two aspects, such as the thickness of mirror, the size of bottom holes, the thickness of ribs and so on. The paper makes sensitivity analysis and chooses proper design variables for further optimization. And then, the paper makes a multi-objective optimal design based on factors mentioned above. In the process of optimization, a special objective function is deduced. At last the optimal design is obtained. The result shows that optimal design scheme has good characteristics. ? 2019 SPIE.Accession Number: 20200508093194 -
Record 380 of
Title:Thermal control design and analysis of a zoom TV optical mechanical system
Author(s):Zhang, Yue(1); Shi, Kui(1); Wang, Huan(1); Zhang, Gaopeng(1,2); Qu, Rui(1,3); Zhang, Zhi(1); Gao, Bo(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11052 Issue: DOI: 10.1117/12.2521772 Published: 2019Abstract:In view of whether the optical system of a focal length 14～360mm continuous zoom TV can obtain high quality and high reliability images in high and low temperature environment, especially in extreme low temperature environment. The thermal design of zoom TV optical-mechanical system using passive thermal control and active thermal control is proposed. The passive thermal control uses polyimide as insulation material to increase the thermal resistance between the camera interior and the outside. Active thermal control uses electric heating film to dynamically heat the key parts of the camera lens. Under the condition of low temperature, the finite element method is used to establish the heat transfer model of the whole lens assembly in the workbench finite element software, and analyze the heat load composition, including the heating power load, the heat convection load and the heat radiation load, and carry on the steady state thermal analysis. Through thermodynamic analysis and experimental verification, the consistency of focal plane of zoom camera optical system is good after taking active thermal control measures at the extreme low temperature of-45°C. The optical transfer function (OTF) of zoom lens at cut-off frequency (100lp/mm) is 0.25 higher than that before thermal design, which can meet the requirements of thermal control design with better transfer function distribution and higher imaging quality. The correctness of the simulation results and the rationality of the optical-mechanical design are verified. ? 2019 SPIE.Accession Number: 20190806535043 -
Record 381 of
Title:Numerical and Experimental Characterization of Radiation Mode of 45° Tilted Fiber Grating
Author(s):Qin, Huabao(1); He, Qinyun(1); Xing, Zhikun(1); Guo, Xi(1); Yan, Zhijun(1); Sun, Qizhen(1); Zhou, Kaiming(2); Wang, Hushan(3); Liu, Deming(1); Zhang, Lin(2)Source: Journal of Lightwave Technology Volume: 37 Issue: 15 DOI: 10.1109/JLT.2019.2920680 Published: August 1, 2019Abstract:In this paper, we have numerically and experimentally investigated the radiation mode of 45° tilted fiber grating (45° TFG). By introducing the axial distributions into the volume current method, we have established a three-dimensional theoretical model to analyze spatial distributions of the radiation mode of 45° TFG, and measured the radiation mode spatial distributions in experiment. Both numerical and experimental results show that the radiation mode of 45° TFG exhibits an exponential reduction along the fiber axial direction, and a quasi-Gaussian profile along the radial direction of fiber. Additionally, we have also measured the detailed polarization-dependent azimuthal intensity distributions of radiation modes of both s-and p-polarized core modes. The degree of polarization of radiation mode is around 99.886%, which is independent of the length and the polarization extinction ratio of the grating. Moreover, for the first time, we have experimentally observed a very weak p-polarized component existing in the radiation mode, which has matched well with the simulation results. ? 1983-2012 IEEE.Accession Number: 20193007234182 -
Record 382 of
Title:Simultaneous Wavelength and Format Conversions Based on the Polarization-Insensitive FWM in Free-Space Optical Communication Network
Author(s):Huang, Xinning(1,2); Suh, Yulong(1); Duan, Tao(1); Hu, Hui(1); Xu, Xin(3); Xie, Xiaoping(1)Source: IEEE Photonics Journal Volume: 11 Issue: 1 DOI: 10.1109/JPHOT.2018.2888621 Published: February 2019Abstract:Free-space optical (FSO) network is an effective way to enhance the interoperability and improve the resource utilization of the FSO communication systems. Since the structure is relatively simple and the nodes are not so many, wavelength conversion-based optical circuit switching (WC-OCS) is an appropriate candidate for the FSO network to solve the blocking problem. Meanwhile, format conversion to lower the data rate is also necessary in case the atmospheric channel deteriorates. In this paper, we construct a 3-node FSO network and experimentally investigate the feasibility of simultaneous WC-OCS and format conversion based on straight-lined single-pump four-wave mixing (FWM) process. The bit-error-ratio (BER) results of the on-off key, binary phase-shift keying (BPSK), and quadrature phase-shift keying (QPSK) signals show that comparing to the corresponding back-to-back (B2B) transmission at the reference BER level of 10-7, power penalties caused by WC-OCS are less than 1-dB for all the three formats. In the format conversion experiment from QPSK to BPSK, the power penalties, comparing to the original BPSK signal after B2B and WC-OCS transmission, are also less than 1 dB at the 10-7 reference BER level. Consequently the feasibility and practicability of the FWM-based optical signal processing at FSO network nodes are experimentally validated. ? 2009-2012 IEEE.Accession Number: 20185206292557 -
Record 383 of
Title:A stereo matching with reconstruction network for lowlight stereo vision
Author(s):Tang, Rui(1); Zhang, Geng(1); Liu, Xuebin(1)Source: ACM International Conference Proceeding Series Volume: Issue: DOI: 10.1145/3372806.3372821 Published: November 27, 2019Abstract:To solve the problem existing in the stereo matching of low-light images, this paper proposes a stereo matching with reconstruction network based on pyramid stereo matching network(PSMNet) and reconstruction module. In view of the characteristics of the lowlight image with severe and complex noise, the image reconstruction module is added into the traditional stereo matching network for automatic denoising. In this process, the image reconstruction module assists the stereo matching module in model training, so as to reduce the influence of noise on stereo matching and obtain more accurate results. The proposed method has been evaluated and achieves good performance on the Middlebury dataset which is preprocessed. In addition, a low-light binocular platform is built to get the true low-light image and test our network in night environment, results show the disparity maps are more accurate compared with previous methods. ? 2019 Association for Computing Machinery.Accession Number: 20200708152648 -
Record 384 of
Title:Spectral recovery matrices identification and experiment of Hadamard transform spectrometer based on DMD
Author(s):Xu, Jun(1); Xie, Zhengmao(2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 48 Issue: 7 DOI: 10.3788/IRLA201948.0717005 Published: July 25, 2019Abstract:A great deal of theoretical research and experimental verification has been done on the DMD spatial light modulated Hadamard transform spectrometer, but the research on this technology was still immature, many problems need to be further studied. The spatial distribution of the dispersion spectrum on the DMD was different because of the different spatial positions of the pixels on the image which resulted in the different encoding matrices of the dispersion spectrum of each pixel. An identification method of spectral recovery matrix was proposed by comparing the gray values of laser-coded images and combining with the changing rules of S-matrix elements. Taking the 7-order left-shift cyclic Smatrix as an example, the results of spectral recovery were verified by two imaging experiments. In the first experiment, a laser beam of 632.8 nm was directed into the spectrometer, the spectral response range of the spectrometer was 550-680 nm, and 632.8 nm within the fifth band range from 626 nm to 644 nm. Theoretically, only the fifth spectral images with a bond range of 626-644 nm was bright, and the rest of the images have no energy distribution. The actual experimental results are in agreement with the theoretical analysis. In the second experiment, the spectrometer was used to image a color butterfly model. The spectral curves of two test points were extracted from the recovered spectral images, and compared with the spectral characteristic curves obtained by radiometer. The experimental results show that the spectral curves obtained from the recovered spectral images are basically the same as the spectral characteristics curves extracted by radiometer. Two groups of spectral recovery experimental results verify the effectiveness of the proposed identification method for spectral recovery matrix. ? 2019, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.Accession Number: 20193807445247