2019

• Record 205 of
  
  Title:Design of improved Köhler illumination for full-field optical coherence tomography system
  
  Author(s):Yang, Fanfan(1,2); Wang, Xingfeng(1,2); Lei, Jiao(1,2); Chen, Guoqing(1,2); Yang, Jianfeng(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 10838  Issue:   DOI: 10.1117/12.2506175  Published: 2019  
  Abstract:According to the characteristics of the reflective optical microscope lighting system, an improved Köhler illumination system for the full-field optical coherence tomography system (FFOCT) was designed to realize the illumination of biological samples and living biological tissues. The illumination system differs from the conventional Köhler illumination system. The filament of the halogen lamp is imaged on the back focal plane of the microscope objective, then parallel light is incident on the sample plane. The improved Köhler illumination system uses a halogen lamp as the light source and is divided into two parts: The condenser front and rear groups. The front condenser group uses two double-glued structures, and the rear group uses a double-coupled lens. The optical design software Zemax was used to optimize the design, and the illumination analysis software Tracepro was used to trace the ray and simulate the imaging of the light source in the front focal plane of the microscope objective. The entire improved Köhler illumination optical path has a total length of 594 mm, the diaphragm is 122 mm from the front group of the condenser, 99 mm from the rear group, and the working distance is 292 mm; the luminous efficiency of the receiving surface is as high as 60.38%, and the edge of the light spot is smooth and clear. The illumination system makes full use of the optical power emitted by the light source and facilitates the placement of a device such as a splitting prism between the condenser and the microscope objective, which satisfies the requirement of the entire machine well. © 2019 COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20190506430693
• Record 206 of
  
  Title:Vignetting effect in Fourier ptychographic microscopy
  
  Author(s):Pan, An(1,2); Chao Zuo(3); Yuege Xie(4); Ming Lei(1); Baoli Yao(1)
  Source: Optics and Lasers in Engineering  Volume: 120  Issue:   DOI: 10.1016/j.optlaseng.2019.02.015  Published: September 2019  
  Abstract:In the usual model of Fourier ptychographic microscopy (FPM), the coherent microscopic system is approximated by being taken as linear space-invariant (LSI) with transfer function determined by a complex pupil function of the objective. However, in real experimental conditions, several unexpected "semi-bright and semi-dark" images with strong vignetting effect can be observed when the sample is illuminated by the LEDs within the "transition zone" between bright field and dark field. These imperfect images, apparently, are not coincident with the LSI model and could deteriorate the reconstruction quality severely. Herein, we investigate the cause and the impact of model misfit based on ray-based and rigorous wave optics-based analysis. Our analysis shows that for a practical FPM microscope with a low magnification objective and a large field-of-view (FOV), the LSI model breaks down as a result of diffraction at other stops or apertures associated with different lens elements. A modified version of the linear space-variant (LSV) model is derived for quantitative analysis. The spectrum of the object will be modulated unexpectedly by a quadratic phase term relatively if assuming the shape of pupil function is invariable. Two countermeasures are also presented and experimentally verified to bypass or alleviate the vignetting-induced reconstruction artifacts. An adaptive update order and initial guess strategy is proposed and demonstrated for better reconstructions. Our work gives a deeper insight into the vignetting effect on wide-FOV imaging and provides a useful guide for easily achieving improved FPM reconstructions that bypass the adverse effect. © 2019 Elsevier Ltd
  Accession Number: 20191006583840
• Record 207 of
  
  Title:Analysis and design of ground-based photoelectric detection system for star observation during the daytime
  
  Author(s):Yu, Yue(1,2); Tian, Yan(1); Hao, Wei(1); Li, Zhe(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11341  Issue:   DOI: 10.1117/12.2544503  Published: 2019  
  Abstract:In this paper, we mainly studied how to calculate the energy values of stars received by ground optical systems. Then according to the characteristics of the radiation spectrum of stars and the radiation spectrum of sky background light, we analyzed and selected the observation spectrum of the image-forming system. We also studied the influence of optical system design parameters, such as field of view, focal length and aperture, on detection capability. At the same time, we analyzed and calculate the limitation of the detector's dark current, readout noise and other noise factors on the ability of receiving stars. The significance of these studies is that we provide an effective theoretical basis for designing and improving ground-based photoelectric detection system for star observation during the daytime. In addition, we used digital image processing technology to process the existing observation images and improve the quality of the image. We provide several algorithms for extracting small targets in strong background. We use threshold segmentation, morphological filtering and other methods to improve the signal-to-noise ratio of the image and then improve the detection ability of the system again. According to the simulation, the target extraction accuracy can reach 1/10 pixels when the target imaging size is 4 pixels and the signal-to-noise ratio is less than 5. Improving the detection ability of photoelectric detection system, detecting more available stars and obtaining their relative position information are the important basis for star map matching and the estimation of targets' position and gesture. © 2019 SPIE.
  Accession Number: 20200408063360
• Record 208 of
  
  Title:Research on active polarization imaging experiments and key technologies in smoke and dust environment
  
  Author(s):Xie, Meilin(1,2); Liu, Peng(1,2); Ma, Caiwen(1); Hao, Wei(1); Huang, Wei(1); Lian, Xuezheng(1); Li, Zhiguo(1); Han, Junfeng(1,2)
  Source: Optik  Volume: 198  Issue:   DOI: 10.1016/j.ijleo.2019.163309  Published: December 2019  
  Abstract:For realizing the engineering application of key technologies in the long-range active polarization imaging system, an experimental platform is built to study the static active polarization imaging technology and related image fusion algorithm in the smoke and dust environment. In the experiments, 532 nm CW laser is used as illumination source after collimation and beam expansion, metal bullet model is used as detection target, smoke environment is created through smoke generator in organic glass hood, polarization direction can be rotated by the polarizer, the images are collected by Lumerera-LM135 camera. The analysis and handling on the images are conducted by the use of the MATLAB software. In the aspects of image information entropy, average gradient, spatial frequency and standard deviation, the polarization imaging effects in various environments are quantitatively compared and analyzed, and the imaging advantages of laser illumination and polarization imaging technology in smoke and dust environment and dim conditions are verified. In order to further improve the imaging quality of active polarization imaging technology, a polarization image fusion algorithm based on fuzzy adaptive is proposed after analyzing a large number of data acquired in the experiment. The experimental results show that the active polarization imaging technology and the improved image fusion algorithm can improve the detection distance of optical system and image contrast, expand the digestible information of images for the long-range dim target imaging in low visibility environment, and provide important data reference and technology support for the application of this technology in shooting range. © 2019 Elsevier GmbH
  Accession Number: 20193707416809
• Record 209 of
  
  Title:Application research of high-precision laser beam pointing technology in airborne aiming pod
  
  Author(s):Xie, Meilin(1,2); Liu, Peng(1,2); Ma, Caiwen(1); Hao, Wei(1); Zhang, Furui(1,2); Huang, Wei(1); Lian, Xuezheng(1)
  Source: Optik  Volume: 183  Issue:   DOI: 10.1016/j.ijleo.2019.02.152  Published: April 2019  
  Abstract:Airborne aiming pod is mainly used for searching, capturing and tracking the target indicated by the laser, and then dropping the laser-guided weapons precisely to complete the close-range support attack or dual-aircraft cooperative instruction/attack. High-precision laser beam pointing technology is the core of the airborne aiming pod, and the accuracy of it is fatal for the realization of the final tactical index. In this paper, the factors affecting the beam pointing accuracy based on the research of airborne aiming pod platform are analyzed. At first, the composition of the pod system and the motion coupling of the composite axis pod are introduced; and then the beam pointing algorithm under the external guidance combined with aircraft disturbance and the effects of atmospheric turbulence and atmospheric attenuation on beam quality, including optical axis drift, beam spread and intensity distribution variation are discussed. Finally, the performance of the pod servo system is simulated and verified in Simulink. The simulation result of the real flight situation with disturbance moment shows that the pointing accuracy of the airborne aiming pod can reach 0.0075 degrees. The data analyzed in this paper can provide technical reference for other aiming photoelectric platforms. © 2019 Elsevier GmbH
  Accession Number: 20191006600389
• Record 210 of
  
  Title:Single space object image denoising and super-resolution reconstructing using deep convolutional networks
  
  Author(s):Feng, Xubin(1,2,4); Su, Xiuqin(1,2); Shen, Junge(3); Jin, Humin(1)
  Source: Remote Sensing  Volume: 11  Issue: 16  DOI: 10.3390/rs11161910  Published: 2019  
  Abstract:Space object recognition is the basis of space attack and defense confrontation. High-quality space object images are very important for space object recognition. Because of the large number of cosmic rays in the space environment and the inadequacy of optical lenses and detectors on satellites to support high-resolution imaging, most of the images obtained are blurred and contain a lot of cosmic-ray noise. So, denoising methods and super-resolution methods are two effective ways to reconstruct high-quality space object images. However, most super-resolution methods could only reconstruct the lost details of low spatial resolution images, but could not remove noise. On the other hand, most denoising methods especially cosmic-ray denoising methods could not reconstruct high-resolution details. So in this paper, a deep convolutional neural network (CNN)-based single space object image denoising and super-resolution reconstruction method is presented. The noise is removed and the lost details of the low spatial resolution image are well reconstructed based on one very deep CNN-based network, which combines global residual learning and local residual learning. Based on a dataset of satellite images, experimental results demonstrate the feasibility of our proposed method in enhancing the spatial resolution and removing the noise of the space objects images. © 2019 by the authors.
  Accession Number: 20193607396467
• Record 211 of
  
  Title:Optical system design of star sensor with long-life
  
  Author(s):Wang, Hu(1,2); Zhang, Xibin(1); Xue, Yaoke(1); Liu, Jie(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11341  Issue:   DOI: 10.1117/12.2541746  Published: 2019  
  Abstract:During process of satellite attitude control, the star sensor provides accurate attitude information for the entire control system, and then ensures the precision of following control operations and the stabilization of flight track. To these satellites in the medium and high Earth orbit, the transmittance of entire system will rapidly attenuate after suffering a long time irradiation of space particles, which leads to the inefficacy of total star sensor and inability of providing accurate attitude information for the satellite control system. This paper presents an optical system of long-life star sensor, with optical characteristics that focal length is 49.7mm, relative aperture is 1/1.18, circular field of view is 14.14°, and the spectral range is 0.51/20.8μm. That can meet the requirement of work time at least eight years in space. The optical system is designed by all spherical mirrors with an compact structure which is just composed by six lenses. the first lens of optical system is fused quartz, the other are just made of two different optical glasses. There are some advantages that its energy is more concentrated because of small dispersed spot and low chromatic aberration, it is to be the benefit of overall debugging with better adaptability to the environmental temperature, and it has the function of optical filtering that the transmittance is higher in the work range of spectrum and is lower out the work range of spectrum, which is benefit to eliminate the stray lights. © 2019 SPIE.
  Accession Number: 20200408063333
• Record 212 of
  
  Title:Sparse representation based medical ultrasound images denoising with reshaped-RED
  
  Author(s):Pu, Xiaoqiu(1,2); Li, Zhixin(1,2); Li, Baopeng(1); Lei, Hao(1); Gao, Wei(1); Liu, Jiwei(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11179  Issue:   DOI: 10.1117/12.2540245  Published: 2019  
  Abstract:Medical ultrasound images are usually corrupted by the noise during their acquisition known as speckle. Speckle noise removal is a key stage in medical ultrasound image processing. Due to the ill-posed feature of image denoising, many regularization methods have been proved effective. This paper introduces an approach which collaborate both sparse dictionary learning and regularization method to remove the speckle noise. The method trains a redundant dictionary by an efficient dictionary learning algorithm, and then uses it in an image prior regularization model to obtain the recovered image. Experimental results demonstrate that the proposed model has enhanced performance both in despeckling and texture-preserving of medical ultrasound images compared to some popular methods. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20193907475158
• Record 213 of
  
  Title:Hyperspectral image classification with imbalanced data based on oversampling and convolutional neural network
  
  Author(s):Cai, Lei(1,2); Zhang, Geng(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11342  Issue:   DOI: 10.1117/12.2543458  Published: 2019  
  Abstract:Data imbalance is a common problem in hyperspectral image classification. The imbalanced hyperspectral data will seriously affect the final classification performance. To address this problem, this paper proposes a novel solution based on oversampling method and convolutional neural network. The solution is implemented in two steps. Firstly, SMOTE(Synthetic Minority Oversampling Technique) is used to enhance the data of minority classes. In the minority classes, SMOTE method is used to generate new artificial samples, and then the new artificial samples are added to the minority classes, so that all classes in the training dataset can reach to the balanced distribution. Secondly, According to the data characteristics of hyperspectral image, a convolutional neural network is constructed for classifying the hyperspectral image. The balanced training data set is used to train the convolutional neural network. We experimented with the proposed solution on the Indian Pines, Pavia University dataset. The experimental results show that the proposed solution can effectively solve the problem of imbalanced hyperspectral data and improve the classification performance. © 2019 SPIE.
  Accession Number: 20200308047029
• Record 214 of
  
  Title:Research on key technology of the optical measurement device used in liquid oxygen tank of carrier rocket
  
  Author(s):Wu, Li(1); Qiang, Zihao(1,2); Li, Yahui(1,2); Gao, Bo(1); Mei, Chao(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 10839  Issue:   DOI: 10.1117/12.2506665  Published: 2019  
  Abstract:For some extreme environment, such as vibration and shock during rocket launching or ultralow temperature in tank of cryogenic propellant, some key technology of the optical measurement device used in liquid oxygen tank of carrier rocket have been researched. In order to obtain a light-weight, high-stiffness and large-heat resistance main board structure for optical measurement device, a thermo-mechanical topology optimization technique is introduced into the main board structure design of optical measurement device for improving the designing quality. Compared with that before the optimization the main board structure reduces weight loses 46.8 percent with the first-order natural frequency above 420 Hz. The numerical results indicate that after adopting the topologic optimization design method, not only the design course is shortened, but also the main board structure weight is effectively reduced, heat resistance is effectively increased and the capability of the main board structure is enhanced. The extreme temperature test results show that the method is effective. © 2019 SPIE.
  Accession Number: 20190706489059
• Record 215 of
  
  Title:Review on on-orbit assembly of large space telescopes
  
  Author(s):Song, Yang(1); Li, Chuang(1); Zhao, Hui(1); Xia, Siyu(1); Li, Xupeng(1,2); Fan, Xuewu(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11341  Issue:   DOI: 10.1117/12.2539065  Published: 2019  
  Abstract:Space telescopes are widely used nowadays with the development of space optics and manufacture technologies. Large aperture of telescope means better resolution and observation. However, due to the carrying capacity and outline dimension of rocket, the aperture of telescope cannot be too large. In order to get the large telescope, more and more scientists and engineers are coming to a new idea that assembling the large space telescope on orbit. First of all, the paper makes an introduction about the concepts and types of on-orbit assembly for telescope. Then paper presents some projects which are being conducted and takes one project as an example to introduce specific implementation methods of on-orbit assembly. What's more, high precision robots are needed in this process. Therefore, paper also introduces technologies about the robots for space assembly. At last, the paper summarizes the features and technical difficulties in on-orbit assembly of large space telescope. Furthermore, the paper points out the development directions about on-orbit assembly telescope in the future, which can give some help or guidance to engineers. © 2019 SPIE.
  Accession Number: 20200408063317
• Record 216 of
  
  Title:Performance analysis of DDR SDRAM in high speed image data acquisition
  
  Author(s):Wang, Yan(1,2); Chen, Xiaolai(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11337  Issue:   DOI: 10.1117/12.2547444  Published: 2019  
  Abstract:High-resolution original video image acquisition has higher and higher requirements for data caching. How to perform real-time, high-speed, complete and effective caching of large-capacity data has become the focus of high-speed image data collection. This article will introduce the FPGA, which is produced by Xilinx, as the main control unit for data storage and processing, supplemented by an experimental platform built by other peripheral circuits. On this experimental platform, the performance of DDR SDRAM in high-speed image data acquisition is studied. Firstly, it introduces the block diagram of the high-speed image data transmission system, the principle of data acquisition subsystem and DDR SDRAM, and the basic principle of high-speed image data read and write control. In addition, the DDR SDRAM read and write data stream speed and bus occupancy rate are simulated and tested during high-speed image data acquisition. Finally, through a lot of experiments, the bandwidth utilization rate of the DDR SDRAM is up to 41.5% when the clock frequency of the DDR SDRAM is 200MHz, which improves the operating speed of the image data acquisition system and reduces the power consumption of the system. © 2019 SPIE.
  Accession Number: 20200408062488