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Record 421 of
Title:Nanosecond passively Q-switched Nd:YVO4 laser based on WS2 saturable absorber
Author(s):Wang, Xi(1); Li, Lu(1); Wang, Yonggang(1,2); Zhang, Ling(3); Wen, Qiao(4); Yang, Guowen(1)
Source: Laser Physics Volume: 27 Issue: 4 DOI: 10.1088/1555-6611/aa5f90 Published: April 2017
Abstract:We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:YVO4 laser using a tungsten disulfide (WS2) solution saturable absorber (SA). The WS2 suspension is fabricated by the liquid-phase-exfoliated method and injected into a quartz cell for the use of SA. Compared with solid absorber, such solution absorber has the virtues of good optical transparency, high heat dissipation and long term stability. By inserting the WS2 solution SA in the laser cavity, a stable Q-switched laser operation centered at 1064.45 nm wavelength is obtained with the shortest pulse duration of 788 ns and corresponding repetition rate of 333.5 kHz. The maximum average output power is registered to be 720 mW with the slope efficiency of 7.8%. To the best of our knowledge, it is the highest output power so far among pulsed lasers based on transition metal dichalcogenides (TMDs) SAs. The results demonstrate that WS2 solution absorber is a promising saturable absorber for the generation of high output power pulsed lasers. ? 2017 Astro Ltd Printed in the UK.
Accession Number: 20171303489950
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Record 422 of
Title:Algorithm of focal spot reconstruction for laser measurement using the schlieren method
Author(s):Lin, Hui(1,2); Da, Zheng-shang(2); Cao, Shi-kang(2); Wang, Zheng-zhou(1,2)
Source: Optik Volume: 145 Issue: DOI: 10.1016/j.ijleo.2017.07.033 Published: September 2017
Abstract:The far-field distribution of lasers is an important parameter for measuring beam quality. To overcome the insufficiencies of the CCD Camera dynamic range when measuring the far-field focal spot, the schlieren method was used to measure the focal spot far-field spatial distribution. Focal spot reconstruction was achieved after gray image matching, calculating the center, and image merging of the main lobe and side lobe. In this study, we used an algorithm based on the optimal arc to obtain the center for the side lobe images by fitting the circle center to improve the accuracy of the focal spot reconstruction. The results showed that the schlieren method of measuring the focal spot reconstruction algorithm could effectively, accurately and completely obtain the far-field focal spot. ? 2017 Elsevier GmbH
Accession Number: 20173003969021
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Record 423 of
Title:Removal functions of different polishing heads worked in planet motion model
Author(s):Yao, Yong-Sheng(1); Ma, Zhen(1); Xu, Liang(1); Ding, Jiao-Teng(1); Wang, Yong-Jie(1); Shen, Le(1); Jiang, Bo(1,2)
Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 25 Issue: 10 DOI: 10.3788/OPE.20172510.2706 Published: October 1, 2017
Abstract:To obtain Gaussian-like removal function in optical manufacturing process, a convenient method to derive the removal functions of various complicated polishing heads by integrating the rotation removal function along the revolution trajectory was proposed based on the traditional planet polising theory. When the speed ratio was greater than 10,the removal function curve of a solid disk by the proposed method was very close to the result by the traditional method, which verifies the correctness of the proposed method. The proposed method was used to derive polishing removal functions of different polishing heads. By computer simulation, it shows that type II petal polishing head gets a better removal function curve when the eccentricity ratio is 0.4.Finally, the type II petal polishing head was polished, and the results indicate that when the eccentricity ratio was 0.4 and the speed ratio is 10,the test and simulation results are consistent with each other and they are all close to the Gaussian curve. These test result verifies the correctness of the proposed method again. ? 2017, Science Press. All right reserved.
Accession Number: 20175104560054
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Record 424 of
Title:Method of controlling optical surface roughness based on stray light requirements
Author(s):Song, Yan-Song(1,2); Yang, Jian-Feng(1); Li, Fu(1); Ma, Xiao-Long(1); Wang, Hong(1,2)
Source: Wuli Xuebao/Acta Physica Sinica Volume: 66 Issue: 19 DOI: 10.7498/aps.66.194201 Published: October 5, 2017
Abstract:Scattering introduced by optical surface fabrication errors could degrade optical performance severely. Therefore, the optical designers are required to provide a roughness index for describing the specific surface or even all surfaces to ensure the final imaging performance. The surface root-mean-square (RMS) roughness is a common index to quantify surface topography. And there are also some available methods to acquire the surface RMS roughness based on bidirectional scattering distribution function theory or the angle spread function theory. However, the influence of the optical surface scattering on the optical system cannot be accurately revealed by the surface RMS roughness determined by these methods. On the one hand, the RMS roughness corresponds to an excessively wide spatial frequency range from 0 to 1/λ, where λ is the wavelength of the light. Consequently, it is difficult to measure the RMS roughness during manufacture. On the other hand, what really worsens the stray light performance of the system is only the surface profile located within a certain subinterval of the aforementioned frequency range, to put it in another way, the surface RMS roughness identified by the methods above is incompetent to quantify the amount of the energy that is surfacescattered to the detector. To address the issues above, in this paper we propose a novel approach to identifying the surface roughness. This method seeks to deduce the relation between optical surface RMS roughness and the stray light requirement of the system by dint of partial integrated scattering (PIS). In contrast to total integrated scattering, PIS counts the scattering light energy that could reach the detector. Hence, the RMS roughness identified in this way corresponds to the effective spatial frequency range that contributes to the stray light in the system. Firstly, the effective frequency range concerned with the system stray light level is identified through the analysis of the propagation path of the scattered light. Then, the surface RMS roughness would be measured within the established range according to the stray light requirement of the system and used to control the surface roughness as the roughness index during the optical manufacture process. The method not only considers the scattering as the surface characteristic, but also takes into account the influence of scattering on the system. Taking the solar magnetic field telescope (MFT) for example, the validity of the method is verified by comparing with the traditional methods. As manifested in the outcome, the effective frequency range of primary mirror is from 0 to 18 mm-1, and the surface RMS roughness identified in such a new way can stage the stray light performance of MFT in a more precise manner, which is more reliable to serve as a surface roughness index. ? 2017 Chinese Physical Society.
Accession Number: 20174904498814
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Record 425 of
Title:Estimation of position and velocity for a low dynamic vehicle in near space using nonresolved photometric and astrometric data
Author(s):Jing, Nan(1,2); Li, Chuang(1); Chong, Yaqin(1,2)
Source: Applied Optics Volume: 56 Issue: 3 DOI: 10.1364/AO.56.000671 Published: January 20, 2017
Abstract:An estimation method for indirectly observable parameters for a typical low dynamic vehicle (LDV) is presented. The estimation method utilizes apparent magnitude, azimuth angle, and elevation angle to estimate the position and velocity of a typical LDV, such as a high altitude balloon (HAB). In order to validate the accuracy of the estimated parameters gained from an unscented Kalman filter, two sets of experiments are carried out to obtain the nonresolved photometric and astrometric data. In the experiments, a HAB launch is planned; models of the HAB dynamics and kinematics and observation models are built to use as time update and measurement update functions, respectively. When the HAB is launched, a ground-based optoelectronic detector is used to capture the object images, which are processed using aperture photometry technology to obtain the time-varying apparent magnitude of the HAB. Two sets of actual and estimated parameters are given to clearly indicate the parameter differences. Two sets of errors between the actual and estimated parameters are also given to show how the estimated position and velocity differ with respect to the observation time. The similar distribution curve results from the two scenarios, which agree within 3σ, verify that nonresolved photometric and astrometric data can be used to estimate the indirectly observable state parameters (position and velocity) for a typical LDV. This technique can be applied to small and dim space objects in the future. ? 2017 Optical Society of America.
Accession Number: 20170403284857
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Record 426 of
Title:Design of VisSWIR continuous zoom optical system
Author(s):Yang, Mingyang(1,2); Yang, Hongtao(1,2); Qu, Ruia(1); Mei, Chaoa(1); Zhou, Zuofeng(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10256 Issue: DOI: 10.1117/12.2259866 Published: 2017
Abstract:For 640 pixel×512 pixel cooled staring focal plane array detector, a VisSWIR wideband continuous zoom optical system with 7X zoom range is presented based on the pattern of the negative zoom group and compensating lens group. The zoom system provides continuous changed in the field of view from narrow to the wide. The zoom optical system works in the range of 0.4μm～1.7μm, F number is 4, the pixel of the detector is 15μm. It realizes 20mm～140mm continuous zoom with a smooth zoom path and provided high image quality with the whole zoom range, the zoom ratio is 7:1. The modulation transfer function(MTF) for the system is above 0.5 within the whole focal length range at spatial frequency of 34lp/mm and it almost approaches the diffraction limit. RMS value of spot diameter was investigation, the maximum distortion value is less than 5% and the surface type of all lens applied is spherical. Moreover, the cam curve after optimization is given by the optical design software Code V macro. The design results provide that the zoom system has the small size, high resolution, excellent image quality and the smooth cam curve etc. ? 2017 SPIE.
Accession Number: 20171703607581
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Record 427 of
Title:Research on position error of sparse optical system
Author(s):Wang, Chenchen(1,2); Shen, Yang(1,2); Zou, Gangyi(1,2); Li, Ruichang(1,2); Fan, Xuewu(1)
Source: Optik Volume: 144 Issue: DOI: 10.1016/j.ijleo.2017.06.082 Published: September 2017
Abstract:The main method to improve the resolution of optical system is to increase the aperture of the optical system, and it is a common method to use the sparse-aperture mirrors to obtain a large aperture primary mirror. The primary mirror of optical system is deployed when it is launched into the orbit, and the deviation between deployed position and design position determines the quality of the optical system. So it is necessary to analyze the position accuracy of segmented mirrors. Sparse-aperture optical system is modeled by optical software Zemax, and by adjusting six degrees of freedom of segmented mirrors can get curves between position error and image quality. The results show that different positions of segmented mirrors can produce different wave-front when they have same position error. Moving along the Z axis, the inner mirrors influence most while the outer ones influence smallest; tilt along the X axis, middle ones have maximum wave-front aberration while the outer ones produce minimum wave-front aberration. When tilt along Y axis, middle segmented mirrors have the smallest wave-front aberration and outer ones have maximum. Two methods are used to distribute the wave-front aberration onto each segmented mirror. One is that according to the relationship curves, distribute the position error to each segmented mirror alone. Another is that each one has same position errors. The final result shows that the former method has a more relax position error when generates the same wave-front aberration. ? 2017 Elsevier GmbH
Accession Number: 20172803922836
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Record 428 of
Title:Movement decoupling control for two-axis fast steering mirror
Author(s):Rui, Wang(1,2); Qiao, Yongming(2); Tao, Lv(2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10256 Issue: DOI: 10.1117/12.2257346 Published: 2017
Abstract:Based on flexure hinge and piezoelectric actuator of two-axis fast steering mirror is a complex system with time varying, uncertain and strong coupling. It is extremely difficult to achieve high precision decoupling control with the traditional PID control method. The feedback error learning method was established an inverse hysteresis model which was based inner product dynamic neural network nonlinear and no-smooth for piezo-ceramic. In order to improve the actuator high precision, a method was proposed, which was based piezo-ceramic inverse model of two dynamic neural network adaptive control. The experiment result indicated that, compared with two neural network adaptive movement decoupling control algorithm, static relative error is reduced from 4.44% to 0.30% and coupling degree is reduced from 12.71% to 0.60%, while dynamic relative error is reduced from 13.92% to 2.85% and coupling degree is reduced from 2.63% to 1.17%. ? 2017 SPIE.
Accession Number: 20171703607526
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Record 429 of
Title:A Multispectral target tracking algorithm based on particle filter
Author(s):Gao, Zhen-Zhen(1,2); Zhang, Geng(1); Hu, Bing-Liang(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10462 Issue: DOI: 10.1117/12.2284791 Published: 2017
Abstract:Target detection and tracking important in many applications including intelligent monitoring system, defense system and terminal guidance system. Aiming to solve the problem of simulated target tracking, this paper proposes an adaptive algorithm which uses the fusion of the spectral and morphological features of multispectral image to realize the target tracking based on the Particle Filter. Firstly, the target area is manually initialized in the multispectral image and the spectral and texture features of the target are extracted. Secondly, we build the adaptive tracking model of multiple features under the framework of Particle Filter. We validate the effectiveness of the proposed approach on the MATLAB platform. The results show that the proposed approach achieves accurate and stable multispectral target tracking in complex scenes by improving the efficiency of particles usage under defective tracking conditions, which is of great theoretical and practical values for the application of multispectral target tracking technology. ? 2017 SPIE.
Accession Number: 20180404671142
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Record 430 of
Title:AID: A benchmark data set for performance evaluation of aerial scene classification
Author(s):Xia, Gui-Song(1); Hu, Jingwen(1,2); Hu, Fan(1,2); Shi, Baoguang(3); Bai, Xiang(3); Zhong, Yanfei(1); Zhang, Liangpei(1); Lu, Xiaoqiang(4)
Source: IEEE Transactions on Geoscience and Remote Sensing Volume: 55 Issue: 7 DOI: 10.1109/TGRS.2017.2685945 Published: July 2017
Abstract:Aerial scene classification, which aims to automatically label an aerial image with a specific semantic category, is a fundamental problem for understanding high-resolution remote sensing imagery. In recent years, it has become an active task in the remote sensing area, and numerous algorithms have been proposed for this task, including many machine learning and data-driven approaches. However, the existing data sets for aerial scene classification, such as UC-Merced data set and WHU-RS19, contain relatively small sizes, and the results on them are already saturated. This largely limits the development of scene classification algorithms. This paper describes the Aerial Image data set (AID): a large-scale data set for aerial scene classification. The goal of AID is to advance the state of the arts in scene classification of remote sensing images. For creating AID, we collect and annotate more than 10000 aerial scene images. In addition, a comprehensive review of the existing aerial scene classification techniques as well as recent widely used deep learning methods is given. Finally, we provide a performance analysis of typical aerial scene classification and deep learning approaches on AID, which can be served as the baseline results on this benchmark. ? 1980-2012 IEEE.
Accession Number: 20171703602276
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Record 431 of
Title:Application of linear CCD in tunnel crack detection
Author(s):Jie, Liu(1,2); Hua, Li(2); Xin, Jiang(2); Hemin, Chang(2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10256 Issue: DOI: 10.1117/12.2257653 Published: 2017
Abstract:To meet the actual demand, the linear CCD technology is applied to tunnel crack detection, and an edge detection algorithm is proposed to measure the crack width. Firstly, the application form of linear CCD imaging technology in tunnel crack detection is introduced concretely in this paper. Then, the key influencing parameters of measurement are discussed. Finally, an edge detection algorithm based on the change of gray level in linear direction is proposed and it is verified by experiments. Experimental results indicated that the linear CCD imaging technology in tunnel crack detection could obtain measurement data quickly and improve the efficiency of tunnel cracks' measurement, and that the detection algorithm could be used for the crack width measuring. ? 2017 SPIE.
Accession Number: 20171703607548
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Record 432 of
Title:Influence of test equipment pose error on dividing error measurement based on autocollimator
Author(s):Tian, Liu-De(1,2); Zhao, Jian-Ke(1); Wang, Tao(1); Zhao, Huai-Xue(1); Duan, Ya-Xuan(1,2); Liu, Zhao-Hui(1)
Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 25 Issue: 9 DOI: 10.3788/OPE.20172509.2267 Published: September 1, 2017
Abstract:In order to improve the measurement accuracy of dividing error of encoders, the principle and method to measure dividing error by using angular polygon and autocollimator were introduced, and the error sources were analyzed. According to the measurement principle, coordinate systems of angular polygon and autocollimator were established. Utilizing the method of coordinate transformation, precise mathematical models were deduced for indicating the relationships between dividing error and misalignment errors, such as parallelism error between the angular polygon working surface and the axis of the tested unit, perpendicularity error between autocollimator optical axis and the working surface of angular polygon, parallelism error between vertical wire of the autocollimator and the axis of the tested unit. In order to verify the error models of misadjustment, three experiments were performed in the laboratory, taking the positioning error of a single-axis position turntable as test object. The experimental and theoretical results have good consistency and the maximum deviation was less than 0.9″, which indicate that the error models of misadjustment are applicable to guide dividing error measurement. ? 2017, Science Press. All right reserved.
Accession Number: 20174504379313
