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Record 397 of
Title:Automatic detection of cloud in high-resolution remote sensing images based on adaptive SLIC and MFC
Author(s):Kang, Chaomeng(1,2); Liu, Jiahang(1); Yu, Kai(1,2); Lu, Zhuanli(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10462 Issue: DOI: 10.1117/12.2285505 Published: 2017
Abstract:Reliable cloud detection plays an important role in the manufacture of remote sensing and the alarm of natural calamities. However, it makes the task difficult with high-resolution remote sensing images with complex background and various types of clouds with different concentration, color and shapes. Related works mostly used gray, shape and texture features to detect clouds, which obtain results with poor robustness and efficiency. To detect cloud more automatically and robustly, we propose a novel could detection method based on the fusion of local optimum by adaptive simple linear iterative clustering (ASLIC) and the whole optimum by bilateral filtering with an improved saliency detection method. After this step, we trained a multi-feature fusion model based support vector machine(SVM) used geometric feature: fractal dimension index (FRAC) and independence index (IDD) which is proposed by us to describe the piece of region's spatial distribution, texture feature: We use four angles to calculate the gray-level co-occurrence matrix (GLXM) about entropy, energy, contrast, homogeneity, spectral feature(SF): After principal component analysis(PCA) we choose the first bond, the second bond and the near infrared bond(NIR). Besides, in view of the disturbance of water, ice, we also use NDVI and HOT index to estimate the model. Compared to the traditional methods of SLIC,our new method for cloud detection is accurate, and robust when dealing with clouds of different types and sizes over various land satellite images. ? 2017 SPIE.
Accession Number: 20180404671009
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Record 398 of
Title:Simple and fast spectral domain algorithm for quantitative phase imaging of living cells with digital holographic microscopy
Author(s):Min, Junwei(1,2); Yao, Baoli(2); Ketelhut, Steffi(1); Engwer, Christian(3); Greve, Burkhard(4); Kemper, Bj?rn(1)
Source: Optics Letters Volume: 42 Issue: 2 DOI: 10.1364/OL.42.000227 Published: January 15, 2017
Abstract:We present a simple and fast phase aberration compensation method in digital holographic microscopy (DHM) for quantitative phase imaging of living cells. By analyzing the frequency spectrum of an off-axis hologram, phase aberrations can be compensated for automatically without fitting or pre-knowledge of the setup and/or the object. Simple and effective computation makes the method suitable for quantitative online monitoring with highly variable DHM systems. Results from automated quantitative phase imaging of living NIH-3T3 mouse fibroblasts demonstrate the effectiveness and the feasibility of the method. ? 2017 Optical Society of America.
Accession Number: 20170303262993
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Record 399 of
Title:A self-Adaptive remote sensing image enhancement method based on gradient and intensity histogram
Author(s):Lu, Zhuanli(1,2); Liu, Jiahang(1); Chen, Tieqiao(1,2); Kang, Chaomeng(1,2); Yu, Kai(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10462 Issue: DOI: 10.1117/12.2285168 Published: 2017
Abstract:It is crucial to enhance the lower contrast Remote remote sensing images to obtain more details information for further remote sensing image processing and application. In this letter here, a self-Adaptive remote sensing image contrast enhancement method has been proposed. The method is an improvement, based on gradient and intensity histogram equalization (GIHE) by using the advantage of histogram compaction transform (HCT). Firstly, we obtained two enhanced images by GIHE and HCT, respectively. Then furthermore, the two enhaceed images were normalized with a self-Adaptive paremeter, which based on standard deviation and mean of the gradient. Finally and then, we modified the normalized image by dual-gamma function for preserving the local details. It's evidenced that the proposed method have more richer details and better subjective visual quality, comparedwith the other methods. The experimental results depicted in terms of PSNR, MAE and Q. Comparing with the other methods, the proposed method had richer details and better subjective visual quality. ? 2017 SPIE.
Accession Number: 20180404671166
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Record 400 of
Title:Application of phase diversity wave-front sensing technique to large space-borne camera
Author(s):Zhao, Hui(1); Yi, Hong-Wei(1); Fan, Xue-Wu(1); Li, Chuang(1); Zou, Gang-Yi(1); Pang, Zhi-Hai(1); Ren, Guo-Rui(1); Zhao, Yan(1); Li, Ai-Ling(1); Wei, Jing-Xuan(2); Xie, Xiao-Peng(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 46 Issue: 1 DOI: 10.3788/gzxb20174601.0111001 Published: January 1, 2017
Abstract:Based on the fundamental principle of phase diversity technique, a prototype space-borne camera was used to experimentally demonstrate the effects of wavefront reversal of phase diversity technique through laboratory and outfield push-broom imaging experiments. Experimental results demonstrate that, the accuracy of wavefront reversal based on phase diversity technique is near 1/40λ(λ=632.8 nm)by using the root-mean-squares of residual wave-front errors between the really obtained wave-front through Zygo and the calculated wave-front through phase diversity as a criterion. At the same time, by carrying out deconvolution to the degraded push-broom images using the estimated wave-front, the image quality could be prominently improved. The signal-to-noise ratio could be improved at least 40% and the modulation transfer function at Nyquist frequency could be improved 80% above, which indirectly proves the effectiveness of phase diversity technique as well. The work reported in this manuscript will pave the way for in-orbit application of phase diversity based wave-front sensing technique in future. ? 2017, Science Press. All right reserved.
Accession Number: 20171103436785
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Record 401 of
Title:Dimensionality reduction method based on a tensor model
Author(s):Yan, Ronghua(1,2); Peng, Jinye(1,3); Ma, Dongmei(4); Wen, Desheng(2)
Source: Journal of Applied Remote Sensing Volume: 11 Issue: 2 DOI: 10.1117/1.JRS.11.025011 Published: April 1, 2017
Abstract:Dimensionality reduction is a preprocessing step for hyperspectral image (HSI) classification. Principal component analysis reduces the spectral dimension and does not utilize the spatial information of an HSI. Both spatial and spectral information are used when an HSI is modeled as a tensor, that is, the noise in the spatial dimension is decreased and the dimension in a spectral dimension is reduced simultaneously. However, this model does not consider factors affecting the spectral signatures of ground objects. This means that further improving classification is very difficult. The authors propose that the spectral signatures of ground objects are the composite result of multiple factors, such as illumination, mixture, atmospheric scattering and radiation, and so on. In addition, these factors are very difficult to distinguish. Therefore, these factors are synthesized as within-class factors. Within-class factors, class factors, and pixels are selected to model a third-order tensor. Experimental results indicate that the classification accuracy of the new method is higher than that of the previous methods. ? 2017 Society of Photo-Optical Instrumentation Engineers (SPIE).
Accession Number: 20172803900091
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Record 402 of
Title:An Allotype Double H-V Depolarizer for Hyperfine Spectrometer
Author(s):Tang, Qian(1); Guo, Li-Xin(1); Zhao, Bao-Chang(2)
Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis Volume: 37 Issue: 12 DOI: 10.3964/j.issn.1000-0593(2017)12-3913-07 Published: December 1, 2017
Abstract:High precision atmospheric detection spectrometers are widely used, because the sunlight would be polarized while passing the atmosphere and that could reduce detecting precision of the devices. There are many efforts on removing this influence. An allotype double H-V(Horizontal-Vertical) depolarizer is proposed, and it is equipped on hyperfine spectrometer used for atmosphere detecting in UV. Because the birefringence structure of crystals could eliminate the polarization, they are always chosen for depolarizers. Essentially, the birefringence of depolarizer can induce depolarization and double-imaging at the same time. The difference between traditional structure and the allotype is the inequality of the wedge angles of two sub H-Vs. There are different double-imaging distances in the spectrum dimension and the spatial dimension. So the contradiction between high-depolarization and high-imaging quality could be resolved. This paper will describe the design and analyzed the result. Depolarization is better than 98.8% and distance of the double-imaging is just 8.7% in the spatial dimension. ? 2017, Peking University Press. All right reserved.
Accession Number: 20181605016138
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Record 403 of
Title:Finite element model updating based on sensitivity analysis for 5-DOF manipulator
Author(s):Fu, Jia(1); Luo, Haitao(1); Yu, Min(2); Liu, Guangming(1)
Source: Proceedings of 2017 IEEE 3rd Information Technology and Mechatronics Engineering Conference, ITOEC 2017 Volume: 2017-January Issue: DOI: 10.1109/ITOEC.2017.8122544 Published: November 27, 2017
Abstract:Multi-degree of freedom manipulators have become a hotspot in the field of robotics because of many advantages. In this paper, a 5-DOF manipulator was taken as the object of study. The modal analysis on it was carried out by methods of test and finite element analysis. A model updating method based on sensitivity analysis was put forward, and the final finite element model was established by iterative optimization. By means of correlation analysis and MAC modal judgment criterion, it was verified that the simulation results of the final simulation model of the manipulator have a good correlation with the experimental modal results. The finite element model determined by this method accurately reflected the actual structural dynamic characteristics of the manipulator. ? 2017 IEEE.
Accession Number: 20181104890537
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Record 404 of
Title:Reflector control technology in space laser communication
Author(s):Xie, Meilin(1,2); Ma, Caiwen(1,2); Yao, Cheng(1,2); Huang, Wei(1); Lian, Xuezheng(1); Feng, Xubin(1,2); Jing, Feng(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10605 Issue: DOI: 10.1117/12.2286414 Published: 2017
Abstract:The optical frequencies band is used as information carrier to realize laser communication between two low-orbit micro-satellites in space which equipped with inter-satellite laser communication terminals, optical switches, space routers and other payload. The laser communication terminal adopts a two-dimensional turntable with a single mirror structure. In this paper, the perturbation model of satellite platform is established in this paper. The relationship between the coupling and coordinate transformation of satellite disturbance is analyzed and the laser pointing vector is deduced. Using the tracking differentiator to speed up the circular grating angle information constitute speed loop feedback, which avoids the problem of error amplification caused by the high frequency of the conventional difference algorithm. Finally, the suppression ability of the satellite platform disturbance and the tracking accuracy of the tracking system are simulated and analyzed. The results show that the tracking accuracy of the whole system is 10μrad in the case of satellite vibration, which provides the basis for the optimization of the performance of the space-borne laser communication control system. ? 2017 SPIE.
Accession Number: 20181705047000
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Record 405 of
Title:Study on Single Dispersion Spectral Imager Based on Compressed Coding
Author(s):Tang, Xing-Jia(1,2); Li, Li-Bo(1); Zhao, Qiang(1); Li, Hong-Bo(1); Hu, Bing-Liang(1)
Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis Volume: 37 Issue: 9 DOI: 10.3964/j.issn.1000-0593(2017)09-2919-08 Published: September 1, 2017
Abstract:With the development of spectral imaging towards higher space resolution, higher spectral resolution and higher signal to noise ratio, some problems have appeared in the traditional spectral imager, for example, data acquisition quantity is too big, the resolution is affected by frame frequency and pixel size of detector, precise alignment is difficult for big caliber and long focus system, and hard to develop signal to noise ratio because of limited optics power. To solve the above problems, a single dispersion spectral imager based on compressed coding is studied. Specially, for the lack of system realization and experiment verification at home, the designation, realization, mathematic model and reconstruction algorithm under multi-frame measurement are mainly studied, and the prototype testing and data processing are achieved. At last, some key problems still need to study, such as code error analysis, multi-model and multi-algorithm, system demarcation, and reconstruction evaluation. This imaging system is consisted of object glass, coding template, dispersion element, collimating lens, focus lens and detector, and hyperspectral data was reconstructed by sparse reconstruction algorithm. There are many advantages in the new system, for example, a smaller data size due to the sparse sample of multi-information, a higher resolution because of code super-resolution, an easier implementation for lower hardware requirement, a higher optical energy usage because the code is instead of slit. The results show that the measurement is efficient, the design of prototype is proper, reconstruction algorithm and calibration method are accurate, the space information of alphabet HSI object is clear, and the spectral information of alphabet HSI object is accurate and closed to tungsten lamp spectral, so the system designation and engineering realization are feasible. ? 2017, Peking University Press. All right reserved.
Accession Number: 20174304306489
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Record 406 of
Title:Optimum structural design for collimation frame of space-based two-dimensional turntable
Author(s):Zhang, Yongqiang(1,2); Liu, Zhaohui(1); Li, Zhiguo(1); Xie, Youjin(1)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 46 Issue: DOI: 10.3788/IRLA201746.S113003 Published: December 25, 2017
Abstract:Space-based two-dimensional turntable is the main load-bearing structure of space photoelectric detection equipment, and the collimation frame is the key support component of turntable, so its stiffness characteristics are vital for the performance of turntable. In order to decrease the mass and improve the stiffness performance, the structure of collimation frame was topologically optimized based on the variable density theory by finite element software -MSC. Patran/Nastran. Modal shape of collimation frame was regarded as the deformation of model under the thrust. The model was optimized with stiffness maximization as the objective function, the ratio of residual volume as the constraints. The results show that the model weight after optimization is lighten 1.32 kg and the first-order natural frequency increases 14.5 Hz compared with the model of experience design. The maximum deformation is relatively reduced by 22.4% and the maximum stress value is relatively reduced by 42.6% under the action of gravity in the Z direction and the statics characteristic of model are increased significantly in the other directions. The dynamic characteristics of the collimation frame are improved significantly with the weight reduction. Modal experiment was done for the optimization model and the results indicate that the finite element analysis is correct. Therefore, it is feasible to use the method of topology optimization to design the structure of collimation frame. ? 2017, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.
Accession Number: 20181705054712
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Record 407 of
Title:A design of high-precision BLDCM drive with bus voltage protection
Author(s):Lian, Xuezheng(1); Wang, Haitao(1); Xie, Meilin(1,2); Huang, Wei(1); Li, Dawei(1); Jing, Feng(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10605 Issue: DOI: 10.1117/12.2286416 Published: 2017
Abstract:In the application of space satellite turntable, the design of balance wheel is very necessary. To solve the acquisition precision of Brushless DC motor speed is low, and the encoder is also more complex, this paper improves the original hall signal measurement methods. Using the logic device to achieve the six frequency multiplication of hall signal, the signal is used as speed feedback to achieve speed closed-loop control and improve the speed stability. At the same time, in order to prevent the E.M.F of BLDC motor to raise the voltage of the bus bar when reversing or braking, and affect the normal operation of other circuit modules, the analog circuit is used to protect the bus bar voltage by the way of energy consumption braking. The experimental results are consistent with the theoretical design, and the rationality and feasibility of the frequency multiplication scheme and bus voltage protection scheme are verified. ? 2017 SPIE.
Accession Number: 20181705047001
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Record 408 of
Title:Thermal effects of optical antenna under the irradiation of laser
Author(s):Sun, Yi(1,2); Li, Fu(2); Yang, Wenqiang(1,2); Yang, Jianfeng(2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10463 Issue: DOI: 10.1117/12.2285378 Published: 2017
Abstract:The laser communication terminal is a precision optical, mechanical, electrical integration device which operations extremely high accuracy. It is hard to improve the space environment adaptability in the hash vibration, thermal cycling, high vacuum and radiation conditions space environment. Accordingly, the optical antenna will be influenced by space thermal environment. Laser energy will be absorbed when optical antenna under the irradiation of laser. It can contribute to thermal distortion and make the beam quality degradation which affects the performance of laser communications links. This influence will aggravate when the laser power rising.Wavefront aberration is the distance between the ideal reference sphere and the actual distorted wavefront. The smaller the wavefront aberration, the better the optical performance of the optical antenna. On the contrary, the greater the wavefront aberration, the worse the performance of the optical antenna or even affect the normal operation of the optical antenna. The performance index of the optical antenna generally requires the wavefront aberration to be better than λ/20. Due to the different thermal and thermal expansion coefficients of the material, the effect of thermal deformation on the optical antenna can be reduced by matching the appropriate material. While the appropriate support structure and proper heat dissipation design can also reduce the impact. In this paper, the wavefront aberration of the optical antenna is better than λ/50 by the material matching and the appropriate support structure and the secondary design of the diameter of 5mm hole thermal design. ? 2017 SPIE.
Accession Number: 20180304654522
