2020

• Record 205 of
  
  Title:Single multimode fiber focused spot scanning based on a liquid crystal spatial light modulator
  
  Author(s):Zhang, Zaikun(1,2); Geng, Yi(1,2); Chen, Hui(1,2); Wang, Ruiduo(1,2); He, Zhengquan(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11717  Issue:   DOI: 10.1117/12.2586312  Published: 2020  
  Abstract:At present, there are some problems in the digital scanning imaging methods of multimode optical fiber, such as poor quality of focused spot, large amount of calculation and long time in the forming process of focused spot. In order to solve the above problems, a parallel phase compensation method based on liquid crystal spatial light modulator (LCSLM) is proposed to achieve fast point-focused scanning of multimode fiber (MMF). The parallel algorithm, which includes the two processes of collecting online specklegrams and calculating offline phase masks, calculates the compensation phase masks so that the phase masks can be loaded on SLM in turn to generate a series of focused spots at different predefined positions, which greatly saves time. Experiments demonstrate that this method doesn't need many iterations, and the phase compensation mask used for focusing spot at a predefined position on the MMF output facet can be obtained by using a two-step phase-shifting technique, and a series of phase compensation masks can be quickly obtained by using the parallel method, so as to form focused spots at different predefined positions. Experimentally, we obtained 100 focused spots, the average focused efficiency was 30.12%, the average focused diameter was 2.3382µµm, and the quality of the focused spot was improved compared with previous reports. © 2020 SPIE.
  Accession Number: 20210109714274
• Record 206 of
  
  Title:Doublet-waveplate polarization transceiver system for backscattering suppression in laser communication terminal
  
  Author(s):Wang, Jing(1,2,3); Xue, Jingjing(3); Qu, Enshi(1); Ren, Liyong(4)
  Source: Optics Communications  Volume: 466  Issue:   DOI: 10.1016/j.optcom.2020.125621  Published: 1 July 2020  
  Abstract:The backscattering suppression capability of the optical signal transceiver is the key to establish a single wavelength full-duplex bidirectional laser communication link. When the signal is transmitted and received through the same telescope of the laser communication terminals, stray light from the high-power laser on mirrors will be received by the high-sensitivity detector, affecting the sensitivity of the system. In this paper, the polarization modulation characteristics of scattered light by the mirrors with different roughness are analyzed. The traditional system based on polarization splitting and transmitting with a single quarter waveplate is improved by using a doublet waveplate, i.e., a combination of a half waveplate and a quarter waveplate. The transceiver system including the off-axis optical antenna is developed and the signal transceiver isolation (ability of suppressing backscattering light) is improved by 7∼8 dB. Although the system complexity is increased, the waveplate can work as a solar window to improve the environmental adaptability. The laser communication terminal would meet the requirements of further link communication, including inter-satellite networks under the same aperture condition. © 2020 Elsevier B.V.
  Accession Number: 20201008258755
• Record 207 of
  
  Title:Algorithm for Underwater Polarization Imaging Based on Global Estimation
  
  Author(s):Feng, Fei(1,2); Wu, Guojun(1,2); Wu, Yafeng(1,2); Miao, Yuhong(1,2); Liu, Bo(1,2)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 40  Issue: 21  DOI: 10.3788/AOS202040.2111002  Published: November 10, 2020  
  Abstract:In order to realize the clear imaging of underwater targets with high degree of polarization (HDOP), the traditional polarization imaging model is analyzed. Based on the Schechner polarization imaging model and the definition of polarization degree, a polarization imaging restoration algorithm is proposed to globally estimate the polarization degree of backscattered light, which considers the polarization degree of reflected light of targets. The polarization imaging experiment is conducted, in which the polarization images of three kinds of targets in turbid water with different concentrations are restored. The restoration results show that the measure of enhancement value of the restored image is increased by more than 90% compared to the original Schechner algorithm. Meanwhile, the average gradient, standard deviation and information entropy of image grey are also increased. The restoration results of different polarization images of targets show that the proposed algorithm is not only suitable for the underwater targets with low degree of polarization (LDOP) and rough surfaces, but also makes the underwater targets with HDOP and smooth surfaces gain satisfactory restoration effect. © 2020, Chinese Lasers Press. All right reserved.
  Accession Number: 20210609880667
• Record 208 of
  
  Title:Overview of spaceborne hyperspectral imagers and the research progress in bathymetric maps
  
  Author(s):Jia, Xinyin(1,2); Li, Siyuan(1); Ke, Shanliang(1); Hu, Bingliang(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11427  Issue:   DOI: 10.1117/12.2550312  Published: 2020  
  Abstract:Coastal environmental elements such as bathymetry maps are of great significance to the economic and military development of each country. Spaceborne hyperspectral imager is one of the important instruments for coastal zone monitoring. Firstly, this paper systematically reviews the index system of spaceborne hyperspectral imagers, and then introduces the applications of hyperspectral remote sensing images in the retrieval of nearshore bathymetry. In order to improve the inversion accuracy, the current research status and shortcomings of fusion technology of laser active remote sensing and hyperspectral passive remote sensing are discussed. Furthermore, the index system of hyperspectral imagers is prospected based on the requirement of applications in coastal zone monitoring, which provides reference and support for the further development of hyperspectral remote sensing in coastal applications. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
  Accession Number: 20201108282826
• Record 209 of
  
  Title:Simultaneous optimization method for tool contour design and path planning of freeform surface flank milling
  
  Author(s):Wang, Jing(1,2); Luo, Ming(1); Zhang, Dinghua(1); Chen, Bing(1)
  Source: Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica  Volume: 41  Issue: 11  DOI: 10.7527/S1000-6893.2020.23720  Published: November 25, 2020  
  Abstract:Aiming at the difficulties in toolpath planning and machining accuracy achievement in free-surface flank milling, this paper proposes a method for designing the tool contour of freeform generatrix. While optimizing the tool contour, this method fully considers the workpiece accuracy and tool axis smoothness during machining, thereby realizing the tool contour design and the flank milling path planning. This study first evaluates the machining error by calculating the interference between tool and workpiece on the cutting line after respectively defining the tool contour generatrix and tool axis trajectory surface to express the tool shape and flank milling path. The tool axis smoothness is also evaluated by tool axis trajectory energy, and a simultaneous optimization model of tool contour and machining trajectory based on the machining error and tool axis smoothness is established. Secondly, to solve the simultaneous optimization model, a solution strategy based on the successive approximation method is presented, and the method for acquiring the control parameters of the tool axis trajectory surface and the tool contour control parameters in the initial values are also provided. Finally, the path planning experiment and tool contour design experiment are designed respectively, verifying the correctness and effectiveness of the algorithm in the tool contour design and path optimization for 4-axis flank milling of freeform surface proposed in this paper. This research provides an effective method for both accuracy improvement in flank milling of freeform surface parts and realization of the tool contour design and path planning of flank milling. © 2020, Beihang University Aerospace Knowledge Press. All right reserved.
  Accession Number: 20205309698977
• Record 210 of
  
  Title:Stray light suppression of common aperture optical antenna for laser communication system
  
  Author(s):Wanga, Jing(1,2,3); Huc, Xinrong(3); Chenc, Su(3); Zhang, Huanhuan(3); Qua, Enshi(1); Rend, Liyong(4)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11570  Issue:   DOI: 10.1117/12.2575985  Published: 2020  
  Abstract:The laser communication system with polarized beam splitting is a useful method for interstellar networking. In longdistance communication terminals which adopts a system of common aperture same frequency transmitting-receiving, the stray light comes from the inside system is generated by retroreflectance and scattering, which will cause interference to the reception of signal light. The ability of internal stray light suppression is the main factor restricting the output power of the system signal and the distance of communication chain-establishment. The optical antenna as the key component of the common channel, coaxial optical antennas are replaced by off-axis optical antennas to reduce paraxial stray light. This work designed miniaturized off-axis optical antenna with a large field of view, and combined the YNI factor to analyze the factors affecting the internal stray light. The proportion of stray light generated on each surface was determined through surface modeling and simulation in Tracepro, and the optical antenna was actually tested by constructing optical path. The test result 71dB is close to the simulation result73dB. It indicates that the off-axis angle and YNI factor can be used to characterize the isolation indicator of optical antenna. We believe this work is of great significance for guiding the rapid design and indicator analysis of the system, meanwhile provides reference for other systems of stray light suppression. © 2020 SPIE. All rights reserved.
  Accession Number: 20204909580497
• Record 211 of
  
  Title:Analysis of Influence of Spike on Phase Retrieval Accuracy of Doppler Asymmetric Spatial Heterodyne Spectrometer and Correction Method
  
  Author(s):Yu, Ting-Ting(1,2); Feng, Yu-Tao(1); Fu, Di(1); Wang, Xuan(1,2); Sun, Chen(1,2); Bai, Qing-Lan(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 49  Issue: 12  DOI: 10.3788/gzxb20204912.1230001  Published: December 2020  
  Abstract:The doppler asymmetric spatial heterodyne interferometer can be used to retrieve the atmospheric wind speed by measuring the phase frequency shift of interference fringes. Because of the interference from cosmic rays and "hot pixels" in CCD, some spikes that have random location and intensity occur on the interferogram. The presence of such spikes can seriously affect the accuracy of wind speed retrieval. In this paper, the theoretical influence of various parameters of spike on the phase inversion accuracy of doppler asymmetric spatial heterodyne interferometer is discussed, and the spike correction method is proposed. Based on the characteristics of the spike and the phase retrieval model of doppler asymmetric spatial heterodyne interferometer, a theoretical model between the phase error and the intensity and position of the spike is established. The influence of the intensity, position and width of the spike on the phase retrieval accuracy is analyzed and verified by experiments. The results show that the phase retrieval error varies periodically with the position of the spike, and is positively correlated with the intensity and peak width of spike. A new method of spike correction based on nearest neighbor comparison and windowed median filter is proposed. The new method can effectively correct the spike without affecting the original interference data. The phase error caused by the spike after correction is reduced by more than 90%, which will help to improve the accuracy of subsequent interference data processing. © 2020, Science Press. All right reserved.
  Accession Number: 20210209739050
• Record 212 of
  
  Title:Advances in soliton microcomb generation
  
  Author(s):Wang, Weiqiang(1); Wang, Leiran(1,2); Zhang, Wenfu(1,2)
  Source: Advanced Photonics  Volume: 2  Issue: 3  DOI: 10.1117/1.AP.2.3.034001  Published: May 1, 2020  
  Abstract:Optical frequency combs, a revolutionary light source characterized by discrete and equally spaced frequencies, are usually regarded as a cornerstone for advanced frequency metrology, precision spectroscopy, high-speed communication, distance ranging, molecule detection, and many others. Due to the rapid development of micro/nanofabrication technology, breakthroughs in the quality factor of microresonators enable ultrahigh energy buildup inside cavities, which gives birth to microcavity-based frequency combs. In particular, the full coherent spectrum of the soliton microcomb (SMC) provides a route to low-noise ultrashort pulses with a repetition rate over two orders of magnitude higher than that of traditional mode-locking approaches. This enables lower power consumption and cost for a wide range of applications. This review summarizes recent achievements in SMCs, including the basic theory and physical model, as well as experimental techniques for single-soliton generation and various extraordinary soliton states (soliton crystals, Stokes solitons, breathers, molecules, cavity solitons, and dark solitons), with a perspective on their potential applications and remaining challenges. © The Authors. Published by SPIE and CLP under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
  Accession Number: 20215011312399
• Record 213 of
  
  Title:Design of a 16 times visible light continuous zoom TV lens component system
  
  Author(s):Yang, Long-Fei(1,2); Wu, Li(1); Liang, Chen-Guang(3); Mei, Chao(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11567  Issue:   DOI: 10.1117/12.2579587  Published: 2020  
  Abstract:In this paper, a TV component of 16 times visible light continuous zoom lens is presented based on 1280*1024@2.7 micron COMS device. The system adopts 4 groups of 12 lenses to achieve continuous zoom, the former fixed group consists of 1 set of adhesive lenses and 1 single lens, the zoom group use 2 single lenses and 1 set of adhesive lenses, the compensating group use 3 single lenses and 1 set of adhesive lenses, and the latter fixed group consists of 2 sets of adhesive lenses and 1 single lens. After selecting three focal length positions for calculation and simulation, when the focal length are 5mm, 40mm and 80mm, the MTF of each field of view is above 0.3 at 120lp/mm, the total length of the system is less than 200mm, the field Angle is 1.6*24.1, F# is 4, and the focal length can be up to 5mm-80mm. The root-mean-square value of the dispersion circle size of each focal length position of the 16-fold visible light continuous zoom TV lens is less than the size of one pixel, so the image quality of each focal length position of the system is better. When the system is in the short focus position, the variable doubling group and the compensation group are at two ends, and the distance between them is the largest. When the system changes from short focus to long focus, the variablesize group and the compensation group approach to the middle, and the distance between them becomes smaller. In the process of system zoom, the image quality is clear, the CAM curve is smooth and suitable for processing. Continuous zoom TV lens all adopt spherical mirror with the characteristic of manufacturing easily, and the glass materials of the system are all taken from Chengdu bright glass library that the materials are easy to obtain. The zoom curve of the continuous zoom lens is smooth and the image is clarity. The distortion of the full view field is less than 3%, which meets the system requirements of the TV lens components. © 2020 SPIE.
  Accession Number: 20205009602495
• Record 214 of
  
  Title:A deep hashing technique for remote sensing image-sound retrieval
  
  Author(s):Chen, Yaxiong(1,2); Lu, Xiaoqiang(1)
  Source: Remote Sensing  Volume: 12  Issue: 1  DOI: 10.3390/RS12010084  Published: January 1, 2020  
  Abstract:With the rapid progress of remote sensing (RS) observation technologies, cross-modal RS image-sound retrieval has attracted some attention in recent years. However, these methods perform cross-modal image-sound retrieval by leveraging high-dimensional real-valued features, which can require more storage than low-dimensional binary features (i.e., hash codes). Moreover, these methods cannot directly encode relative semantic similarity relationships. To tackle these issues, we propose a new, deep, cross-modal RS image-sound hashing approach, called deep triplet-based hashing (DTBH), to integrate hash code learning and relative semantic similarity relationship learning into an end-to-end network. Specially, the proposed DTBH method designs a triplet selection strategy to select effective triplets. Moreover, in order to encode relative semantic similarity relationships, we propose the objective function, which makes sure that that the anchor images are more similar to the positive sounds than the negative sounds. In addition, a triplet regularized loss term leverages approximate l1-norm of hash-like codes and hash codes and can effectively reduce the information loss between hash-like codes and hash codes. Extensive experimental results showed that the DTBH method could achieve a superior performance to other state-of-the-art cross-modal image-sound retrieval methods. For a sound query RS image task, the proposed approach achieved a mean average precision (mAP) of up to 60.13% on the UCM dataset, 87.49% on the Sydney dataset, and 22.72% on the RSICD dataset. For RS image query sound task, the proposed approach achieved a mAP of 64.27% on the UCM dataset, 92.45% on the Sydney dataset, and 23.46% on the RSICD dataset. Future work will focus on how to consider the balance property of hash codes to improve image-sound retrieval performance. © 2019 by the authors.
  Accession Number: 20200808209252
• Record 215 of
  
  Title:Multisource Compensation Network for Remote Sensing Cross-Domain Scene Classification
  
  Author(s):Lu, Xiaoqiang(1); Gong, Tengfei(1,2); Zheng, Xiangtao(1)
  Source: IEEE Transactions on Geoscience and Remote Sensing  Volume: 58  Issue: 4  DOI: 10.1109/TGRS.2019.2951779  Published: April 2020  
  Abstract:Cross-domain scene classification refers to the scene classification task in which the training set (termed source domain) and the test set (termed target domain) come from different distributions. Various domain adaptation methods have been developed to reduce the distribution discrepancy between different domains. However, current domain adaptation methods assume that the source domain and target domain share the same categories. In reality, it is hard to find a source domain that can completely cover all the categories of target domain. In this article, we propose to use multiple complementary source domains to form the categories of target domain. A multisource compensation network (MSCN) is proposed to tackle these challenges: distribution discrepancy and category incompleteness. First, a pretrained convolutional neural network (CNN) is exploited to learn the feature representation for each domain. Second, a cross-domain alignment module is developed to reduce the domain shift between source and target domains. Domain shift is reduced by mapping the two domain features into a common feature space. Finally, a classifier complement module is proposed to align categories in multiple sources and learn a target classifier. Two cross-domain classification data sets are constructed using four heterogeneous remote sensing scene classification data sets. Extensive experiments are conducted on these datasets to validate the effectiveness of the proposed method. The proposed method can achieve 81.23% and 81.97% average accuracies on two-source-complementary data set and three-source-complementary data set, respectively. © 2019 IEEE.
  Accession Number: 20201508402756
• Record 216 of
  
  Title:Retrieval Topic Recurrent Memory Network for Remote Sensing Image Captioning
  
  Author(s):Wang, Binqiang(1,2); Zheng, Xiangtao(1); Qu, Bo(1); Lu, Xiaoqiang(1)
  Source: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing  Volume: 13  Issue:   DOI: 10.1109/JSTARS.2019.2959208  Published: 2020  
  Abstract:Remote sensing image (RSI) captioning aims to generate sentences to describe the content of RSIs. Generally, five sentences are used to describe the RSI in caption datasets. Every sentence can just focus on part of images' contents due to the different attention parts of annotation persons. One annotated sentence may be ambiguous compared with other four sentences. However, previous methods, treating five sentences separately, may generate an ambiguous sentence. In order to consider five sentences together, a collection of words, which named topic words contained common information among five sentences, is jointly incorporated into a captioning model to generate a determinate sentence that covers common contents in RSIs. Instead of employing a naive recurrent neural network, a memory network in which topic words can be naturally included as memory cells is introduced to generate sentences. A novel retrieval topic recurrent memory network is proposed to utilize the topic words. First, a topic repository is built to record the topic words in training datasets. Then, the retrieval strategy is exploited to obtain the topic words for a test image from topic repository. Finally, the retrieved topic words are incorporated into a recurrent memory network to guide the sentence generation. In addition to getting topics through retrieval, the topic words of test images can also be edited manually. The proposed method sheds light on controllability of caption generation. Experiments are conducted on two caption datasets to evaluate the proposed method. © 2008-2012 IEEE.
  Accession Number: 20201008260498