2020

• Record 181 of
  
  Title:Structured light stereo vision system research
  
  Author(s):Wang, Zhiyuan(1,2); Xue, Bin(1); Li, Zhicong(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11567  Issue:   DOI: 10.1117/12.2579956  Published: 2020  
  Abstract:Three-dimensional measurement technology is a popular technology in recent years. The traditional binocular vision measurement system has a low image matching accuracy when there are few or many duplicate feature points on the surface of the object to be measured, which affects the work of three-dimensional reconstruction. In this paper, the combination of structured light three-dimensional measurement technology and binocular imaging technology reduces the difficulty of feature point search, increases the accuracy of image matching, and conducts experiments of three-dimensional measurement by building a verification system. The measurement results show that the technology is highly feasible. © 2020 SPIE.
  Accession Number: 20205009602520
• Record 182 of
  
  Title:Optimized all-fiber laser Doppler velocimeter with large depth of field
  
  Author(s):Hao, GeYang(1); Cui, Ying(2); Yang, Yucheng(1); lv, Xiaopeng(1); Wu, Guojun(1)
  Source: Optical Fiber Technology  Volume: 60  Issue:   DOI: 10.1016/j.yofte.2020.102333  Published: December 2020  
  Abstract:Due to the low spatial coupling efficiency of optical fiber and large energy loss, the depth of field in the all-fiber laser Doppler velocimeter is short, and the focus needs to be adjusted before measurement, so it is impossible to continuously measure the velocity of object moving along the optical axis. To solve this problem, an all-fiber Doppler velocimeter based on the Mach-Zehnder interferometer structure is designed, also, in the optical antenna section, C-lens is used to change the divergence angle of the light coming out of the optical fiber. The optimized design achieves the detection with large depth of field. The experiment is designed to verify the intensity of the echo signal, signal-to-noise ratio (SNR) and the speed accuracy of the velocimeter taken in different depths of field. The test results show that the depth of field in this system is superior to 25 m. The SNR is stable around 16 dB with small fluctuation in the range of depth of field, and the speed accuracy is better than ±0.1 m/s. © 2020 Elsevier Inc.
  Accession Number: 20204409423547
• Record 183 of
  
  Title:A propagation of interferogram signal-to-noise (SNR) and phase uncertainty in Doppler asymmetric spatial heterodyne spectrometer
  
  Author(s):Sun, Chen(1,2); Feng, Yu-Tao(1); Fu, Di(1); Zhang, Ya-Fei(1,2); Li, Juan(1); Liu, Xue-Bin(1)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 69  Issue: 1  DOI: 10.7498/aps.69.20191179  Published: January 5, 2020  
  Abstract:Passive atmospheric wind detection technique retrieves atmospheric wind profile by measuring the Doppler shift of airglow emissions. Doppler asymmetric spatial heterodyne spectrometer (DASH), which is a Fourier transform spectrometer(FTS), retrieves the Doppler shift information of airglow emissions by detecting the phase shift of interferograms, and the measured phase accuracy directly affects the retrieved wind speed precision. The signal-to-noise (SNR) ratio is one of the significant indexes for evaluating the performance of wind-measuring interferometers in engineering applications. Studying the quantitative relationship between retrieved phase uncertainty and original interferogram SNR that is based on observations is quite essential for the DASH design, performance evaluation and wind profile applications. In this paper, the study is based on the noise propagation theory in FTS and DASH phase retrieval model. According to the Fourier transform relationship between time and frequency domain, we start from original interferogram expression, then we conduct the Fourier transforming, single frequency extracting, inverse Fourier transforming, phase calculating and first-order Taylor expanding, and finally we establish a theoretical relationship model between original interferogram SNR and retrieved phase uncertainty. In order to verify the theoretical relationship model, firstly, we generate 20 groups of interferograms (each group with 1000 frames) randomly with varying the 30–250 times SNR value. After removing the low frequency baseline, we calculate the phase of each interferogram by DASH phase retrieval model, and obtain the phase uncertainty by calculating standard deviation of the 512th sampling of each group interferogram. Another phase retrieval uncertainty is obtained by using the theoretical relationship model between SNR and retrieved phase uncertainty derived from this paper. Secondly, a total of 23 groups of experimental interferograms (each group with 100 frames) with different intensities are collected through the self-developed DASH with a center wavelength of 632.8 nm, basic optical path difference of 50 mm, spectral resolution of 0.78 cm−1. Combining physical characteristics of shot noise and DASH parameters, interferogram SNR of each frame is calculated. We calculate phase uncertainty of experimental data through the two methods mentioned above. The results from the two different calculation methods are compared with each other to determine whether the conclusion is correct. In order to improve the accuracy of phase calculation, three lines are averaged as input to reduce the random error. The average residual between the two methods is only 0.03 mrad, the high consistency of the results indicates that the theoretical relationship model between SNR and retrieved phase uncertainty for DASH is correct. The phase uncertainty can be evaluated by interferogram SNR directly in engineering, which provides a theoretical basis for optimizing the interferometer design. © 2020 Chinese Physical Society.
  Accession Number: 20202108693719
• Record 184 of
  
  Title:Research on high precision position attitude measurement method of moving platform based on optical calibration
  
  Author(s):Wei, Hao(1); Fang, Wang(2); Meilin, Xie(1); Yu, Cao(1,3); Minglai, Chen(1,3); Peng, Liu(1,3); Xuezheng, Lian(1); Wei, Huang(1); Kai, Liu(1)
  Source:   Volume:   Issue:   DOI: 10.1109/ITAIC49862.2020.9338885  Published: 2020  
  Abstract:Based on the airborne platform, the research on the measurement technology of moving base target is not without loss of generality. The methods and key technologies to improve the target measurement accuracy can be applied to airships, ships, vessels, vehicles and other moving platforms. However, the optical measurement based on the moving platform relies heavily on the position and attitude measurement accuracy of the platform itself. Therefore, aiming at the measurement environment of the airborne opto-electronic platform, a calibration camera unit is proposed to be installed on the UAV, and an attitude measurement system is formed by the active motion cross aim imaging of the calibration camera. According to the prior attitude information, position information, target UAV position information and target UAV miss distance, the attitude of UAV is calculated and measured. This paper first introduces the working principle of the whole system, and then deduces the attitude solution method in detail. Finally, through simulation, it is verified that this method can reach the attitude solution accuracy within 17 '. The method proposed in this paper is an effective supplementary means of range optical measurement, which lays a foundation for further research. © 2020 IEEE.
  Accession Number: 20210809946289
• Record 185 of
  
  Title:Investigation of high-precision algorithm for the spot position detection for four-quadrant detector
  
  Author(s):Xuan, Wang(1,2,3); Xiuqin, Su(1); Guizhong, Liu(2); Junfeng, Han(1); Rui, Wang(1,3)
  Source: Optik  Volume: 203  Issue:   DOI: 10.1016/j.ijleo.2019.163941  Published: February 2020  
  Abstract:In this paper, we propose a new polynomial fitting algorithm to improve the spot position detection accuracy based on four-Quadrant Detector (4QD) when the circular spot with Gaussian energy is used as the incident light model. The traditional polynomial fitting method is difficult to ensure high spot position detection accuracy in a wide detection range. To solve this problem, we analyze and compare the characteristics of different algorithms for spot position detection, and consider the influence of the 4QD gap size in the model. Based on the initial solution of the geometric approximation method, we introduce the error compensation factor function, a new spot position detection model is designed. The results of simulation and experiment show that the new algorithm can greatly reduce the position detection error of 4QD for Gaussian spot. When the radius of incident spot is 0.5 mm and within the detection range of [-0.5 mm∼0.5 mm], the maximum error is 0.001353 mm and the root-mean-square error is 0.0004596 mm with the new five-order polynomial fitting algorithm which are reduced 56.7% and 69.7% than traditional nine-order polynomial fitting algorithm. Moreover, the computational complexity of the new algorithm is much less than traditional algorithm and the new algorithm also has good prospects in laser communication, high energy laser weapons or others. © 2019 Elsevier GmbH
  Accession Number: 20195007811264
• Record 186 of
  
  Title:Design of a compact freeform optical system via the surface contribution analysis method
  
  Author(s):Gangyi, Zou(1,2); Xuewu, Fan(1); Zhihai, Pang(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11570  Issue:   DOI: 10.1117/12.2579719  Published: 2020  
  Abstract:The surface contribution analysis method is to find the wavefront map at the local intermediate entrance and exit pupil reference spheres for each optical surface. Direct pictures of each surface aberration contribution are then given by fitting the wavefront errors with Fringe Zernike polynomials which can help optical designers to find the origins of the main aberrations at the final focal plane and make them choose the effective variables for optimization consciously, which is very helpful for designing the freeform optical system with hundrands of variables. This paper discusses the surface contribution analysis method. A Matlab routine is written to communicate with Code V and to give direct pictures of aberration contribution for each surface. A compact freeform optical system is designed to validate the surface contribution analysis design method which is proved to have good convergence and very directive for optical designers. © 2020 SPIE. All rights reserved.
  Accession Number: 20204909580474
• Record 187 of
  
  Title:Inter-site harmonization based on dual generative adversarial networks for diffusion tensor imaging: Application to neonatal white matter development
  
  Author(s):Zhong, Jie(1,2); Wang, Ying(2); Li, Jie(2); Xue, Xuetong(2); Liu, Simin(1); Wang, Miaomiao(1); Gao, Xinbo(2); Wang, Quan(3); Yang, Jian(1); Li, Xianjun(1)
  Source: BioMedical Engineering Online  Volume: 19  Issue: 1  DOI: 10.1186/s12938-020-0748-9  Published: January 15, 2020  
  Abstract:Background: Site-specific variations are challenges for pooling analyses in multi-center studies. This work aims to propose an inter-site harmonization method based on dual generative adversarial networks (GANs) for diffusion tensor imaging (DTI) derived metrics on neonatal brains. Results: DTI-derived metrics (fractional anisotropy, FA; mean diffusivity, MD) are obtained on age-matched neonates without magnetic resonance imaging (MRI) abnormalities: 42 neonates from site 1 and 42 neonates from site 2. Significant inter-site differences of FA can be observed. The proposed harmonization approach and three conventional methods (the global-wise scaling, the voxel-wise scaling, and the ComBat) are performed on DTI-derived metrics from two sites. During the tract-based spatial statistics, inter-site differences can be removed by the proposed dual GANs method, the voxel-wise scaling, and the ComBat. Among these methods, the proposed method holds the lowest median values in absolute errors and root mean square errors. During the pooling analysis of two sites, Pearson correlation coefficients between FA and the postmenstrual age after harmonization are larger than those before harmonization. The effect sizes (Cohen's d between males and females) are also maintained by the harmonization procedure. Conclusions: The proposed dual GANs-based harmonization method is effective to harmonize neonatal DTI-derived metrics from different sites. Results in this study further suggest that the GANs-based harmonization is a feasible pre-processing method for pooling analyses in multi-center studies. © 2020 The Author(s).
  Accession Number: 20200408066526
• Record 188 of
  
  Title:A Research on Typhoon Tracking System Based on Meteorological Remote Sensing
  
  Author(s):Qiu, Shi(1); Li, Bin(2); Gao, Guilong(1); Zhou, Tao(2); Meng, XianJia(2); Liang, Ting(1)
  Source: 2020 International Conference on Internet of Things and Intelligent Applications, ITIA 2020  Volume:   Issue:   DOI: 10.1109/ITIA50152.2020.9312338  Published: November 27, 2020  
  Abstract:Due to the difficulty of typhoon detection and tracking, a typhoon tracking system based on Meteorological remote sensing is proposed. Firstly, the SSD algorithm is improved to detect typhoon, and then a correlation filter is constructed to track typhoon. In order to enhance the stability of tracking model, a day-night line extraction algorithm is proposed to realize the accurate detection and tracking of typhoon. The tracking accuracy can reach 90%. © 2020 IEEE.
  Accession Number: 20210910007198
• Record 189 of
  
  Title:Non-blind image blur removal method based on a Bayesian hierarchical model with hyperparameter priors
  
  Author(s):Yang, Haoyuan(1,2); Su, Xiuqin(1); Wu, Jing(3); Chen, Songmao(1,2)
  Source: Optik  Volume: 204  Issue:   DOI: 10.1016/j.ijleo.2020.164178  Published: February 2020  
  Abstract:In many image blur removal schemes, a proper point spread function is usually estimated in advance from the blurry image, then the latent image comes out by using existing non-blind techniques. However, some of the techniques suffer from strong artifacts. Therefore, an efficient non-blind method plays an important role in image restoration issues. In most models, image priors act as the regularization terms that hold image details and suppress noises. This paper introduces a new image prior based on a parameterized scaled Gaussian model and a gamma distribution, with hyperparameters based on the statistical properties of tens of thousands of images. Our regularized cost function is then formed via a Bayesian hierarchical approach. It consists of a data fidelity term and a series of constraints on image gradients in multiple orientations. The former is used to assure the best approximation of the original image, and the latter is for preserving sharp edges. The optimization problem is solved by an effective tail-recursive algorithm based on the conjugate descent technique. Experimental results show that our model can both deal with simulated data and real scenes. The comparisons show our method outperforms others and achieves promising results. © 2020 Elsevier GmbH
  Accession Number: 20200207998355
• Record 190 of
  
  Title:Remote Sensing Scene Classification by Gated Bidirectional Network
  
  Author(s):Sun, Hao(1,2); Li, Siyuan(1,3,4); Zheng, Xiangtao(1); Lu, Xiaoqiang(1)
  Source: IEEE Transactions on Geoscience and Remote Sensing  Volume: 58  Issue: 1  DOI: 10.1109/TGRS.2019.2931801  Published: January 2020  
  Abstract:Remote sensing (RS) scene classification is a challenging task due to various land covers contained in RS scenes. Recent RS classification methods demonstrate that aggregating the multilayer convolutional features, which are extracted from different hierarchical layers of a convolutional neural network, can effectively improve classification accuracy. However, these methods treat the multilayer convolutional features as equally important and ignore the hierarchical structure of multilayer convolutional features. Multilayer convolutional features not only provide complementary information for classification but also bring some interference information (e.g., redundancy and mutual exclusion). In this paper, a gated bidirectional network is proposed to integrate the hierarchical feature aggregation and the interference information elimination into an end-to-end network. First, the performance of each convolutional feature is quantitatively analyzed and a superior combination of convolutional features is selected. Then, a bidirectional connection is proposed to hierarchically aggregate multilayer convolutional features. Both the top-down direction and the bottom-up direction are considered to aggregate multilayer convolutional features into the semantic-assist feature and appearance-assist feature, respectively, and a gated function is utilized to eliminate interference information in the bidirectional connection. Finally, the semantic-assist feature and appearance-assist feature are merged for classification. The proposed method can compete with the state-of-the-art methods on four RS scene classification data sets (AID, UC-Merced, WHU-RS19, and OPTIMAL-31). © 1980-2012 IEEE.
  Accession Number: 20200408075939
• Record 191 of
  
  Title:Learning Non-Local Spatial Correlations to Restore Sparse 3D Single-Photon Data
  
  Author(s):Chen, Songmao(1); Halimi, Abderrahim(2); Ren, Ximing(1); McCarthy, Aongus(2); Su, Xiuqin(2); McLaughlin, Stephen(1); Buller, Gerald S.(1)
  Source: IEEE Transactions on Image Processing  Volume: 29  Issue:   DOI: 10.1109/TIP.2019.2957918  Published: 2020  
  Abstract:This paper presents a new algorithm for the learning of spatial correlation and non-local restoration of single-photon 3D Lidar images acquired in the photon starved regime (fewer or less than one photon per pixel) or with a reduced number of scanned spatial points (pixels). The algorithm alternates between three steps: (i) extract multi-scale information, (ii) build a robust graph of non-local spatial correlations between pixels, and (iii) the restoration of depth and reflectivity images. A non-uniform sampling approach, which assigns larger patches to homogeneous regions and smaller ones to heterogeneous regions, is adopted to reduce the computational cost associated with the graph. The restoration of the 3D images is achieved by minimizing a cost function accounting for the multi-scale information and the non-local spatial correlation between patches. This minimization problem is efficiently solved using the alternating direction method of multipliers (ADMM) that presents fast convergence properties. Various results based on simulated and real Lidar data show the benefits of the proposed algorithm that improves the quality of the estimated depth and reflectivity images, especially in the photon-starved regime or when containing a reduced number of spatial points. © 1992-2012 IEEE.
  Accession Number: 20200808199930
• Record 192 of
  
  Title:Optofluidic in-fiber on-line ethanol sensing based on graphene oxide integrated hollow optical fiber with suspended core
  
  Author(s):Gao, Danheng(1); Yang, Xinghua(1); Teng, Pingping(1); Kong, Depeng(2); Liu, Zhihai(1); Yang, Jun(1); Luo, Meng(1); Li, Zhanao(1); Wen, Xingyue(1); Yuan, Libo(1,3); Li, Kang(4); Copner, Nigel(4)
  Source: Optical Fiber Technology  Volume: 58  Issue:   DOI: 10.1016/j.yofte.2020.102250  Published: September 2020  
  Abstract:In this study, a novel in-fiber optofluidic trace ethanol sensor is proposed firstly. The microstructured hollow fiber (MHF) with a suspended core is a key part of the overall device which is integrated with graphene oxide (GO). The GO can be uniformly trapped on the whole surface of the suspended core in the MHF by using evanescent field inducing method. When trace microfluidic ethanol passes through the in-fiber device, the light intensity of the suspended core can be significantly modulated through the interaction between the GO on the core and ethanol. The device presents an excellent linearity on-line response with an average sensitivity of 0.16 dB/% with linear regression equation of y = 0.16x + 25.989. In general, this compact optofluidic in-fiber trace ethanol sensor can be utilized as for on-line detection of trace amounts of ethanol in special environments. © 2020 Elsevier Inc.
  Accession Number: 20202208713748