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Record 349 of
Title:Flexible On-Orbit Calibration for Monocular Camera and Laser Rangefinder Integrated Pose Measurement System
Author(s):Zhang, Guangdong(1); Zhang, Gaopeng(2); Yang, Hongtao(2); Wang, Changqing(2); Bao, Wenfan(1); Chen, Weining(1); Cao, Jianzhong(2); Du, Hubing(3); Zhao, Zixin(4); Liu, Chang(3)
Source: IEEE Transactions on Instrumentation and Measurement Volume: 72 Issue: null Article Number: 1003116 DOI: 10.1109/TIM.2023.3265638 Published: 2023
Abstract:Due to its low cost and ease of manufacture, integrated monocular space camera and laser rangefinders are commonly used in many space applications (i.e., pose measurement of noncooperative targets). This and other composite systems estimate poses with high precision using a combination of high-resolution lateral visual and high-precision distance information. Notably, any system that is tested on ground must again receive precise on-orbit calibration because the accompanying spaceborne turntables and arms must be frequently manipulated to meet the field-of-view and distance measurement requirements and require complicated realignments. To accommodate flexible multiple target calibration, this study proposed an on-orbit model that obtains accurate pose relationships jointly using the monocular camera and laser rangefinder. First, we invented a robust calibration model and derive its pose transformation matrix based on the given component positions. We then provided an improved (simplified) orthogonal iteration algorithm that optimizes the given matrix for calibration. The influences of different factors on calibration accuracy are quantitatively analyzed via simulations, and the new method's performance is verified with real-world experiments. This system enables several novel and significant space and military applications. ? 1963-2012 IEEE.
Accession Number: 20231714014773
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Record 350 of
Title:Segmentation of Thyroid Nodules Based on Hyperspectral Images
Author(s):Wang, Junjie(1,2); Tao, Chenglong(1); Du, Jian(1); Hu, Bingliang(1,3); Zhang, Zhoufeng(1,3)
Source: IEEE Joint International Information Technology and Artificial Intelligence Conference (ITAIC) Volume: null Issue: null Article Number: null DOI: 10.1109/ITAIC58329.2023.10408843 Published: 2023
Abstract:Thyroid nodules are a common thyroid disease, and early detection and treatment have a significant impact on the prognosis of patients. Hyperspectral image technology has significant advantages in medical image analysis due to its high-resolution and multi band characteristics, especially in the recognition and classification of thyroid nodules, which has important application value. But currently, there is no very effective method for segmenting hyperspectral images of thyroid nodules. Deep learning algorithms have shown superior performance in recent years in computer vision and pattern recognition tasks, including medical image analysis. This paper proposes the use of VGG model for segmentation of hyperspectral images of thyroid nodule tissue. Hyperspectral images can obtain spatial and spectral information of organizations, and VGG models can segment images through deep networks. Using hyperspectral and VGG, we found that thyroid nodule tissue can be well distinguished at the pixel level. ? 2023 IEEE.
Accession Number: 20240915642401
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Record 351 of
Title:Short pulse laser drive technology in a distance-selective imaging system
Author(s):Wang, Chong(1); Yang, Jia-Hao(1); Zhu, Bing-Li(2); Han, Jiang-Hao(1); Dang, Wen-Bin(1)
Source: Chinese Optics Volume: 16 Issue: 3 Article Number: null DOI: 10.37188/CO.2022-0142 Published: May 2023
Abstract:In a distance-selected imaging system based on single-photon detection, a short-pulse laser is emitted and synchronization control between the transmitter and receiver is performed, and the detector operates in photon counting mode and integrates in time to complete the imaging. In order to obtain a short pulse laser that meets the system requirements while reducing the system’s size and cost, we propose to apply two types of narrow pulse generation circuits based on RF bipolar transistor and Step Recovery Diode (SRD) to single photon distance selective imaging systems. We introduce the principle and design method of both types and verify the system through simulation, physical fabrication and testing. The characteristics of the pulse generator and factors affecting its pulse width and amplitude are analyzed. The physical test results show that the transistor-based method can generate a narrow pulse with a rise time of 903.5 ps, a fall time of 946.1 ps, a pulse width of 824 ps, and an amplitude of 2.46 V; the SRD-based method can generate a narrow pulse with a rise time of 456.8 ps, a fall time of 458.3 ps, a pulse width of 1.5 ns, and an amplitude of 2.38 V; and the repetition frequency of both can reach 50 MHz. Both design methods can be used with external current-driven laser diodes to achieve excellent short pulse laser output. ? 2023 Editorial Office of Chinese Optics. All rights reserved.
Accession Number: 20232314196042
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Record 352 of
Title:Thermal compensation design of achromatic and apochromatic optical systems using a 3D glass chart
Author(s):Ren, Zhiguang(1,2); Li, Xuyang(1,2); Pang, Zhihai(1,2); Wang, Wei(1,2); Wei, Jinyang(1,2); Zhao, Jiawen(1,2); Yao, Kaizhong(1,2)
Source: Applied Optics Volume: 62 Issue: 17 Article Number: null DOI: 10.1364/AO.489048 Published: June 10, 2023
Abstract:It is important to determine the ideal combination of housing materials, groups of refractive materials, and their optical powers for athermalizing achromatic and apochromatic optical systems. This study proposes a combined design approach that utilizes three or more glass types to resolve thermal aberrations and defocus achromatic and apochromatic optical systems. It selects a suitable glass type using a 3D glass chart and calculates the optical power analytically. Furthermore, a temperature-insensitive optical system with a 450-750 nm band based on refractive materials (CDGM Glass Co., Ltd.) is designed, with the modular transfer function value of the center field of view decreasing by less than 0.024 in the temperature range of-40°Cto+80°Cand the secondary spectrum aberration decreasing by over three times and being maintained within 0.08mm. ? 2023 Optica Publishing Group.
Accession Number: 20232914414183
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Record 353 of
Title:Design of a co-aperture composite imaging system for visible light remote sensing camera and synthetic aperture radar
Author(s):Zhao, Wei(1,2); Yue, Pan(1); Xuewu, Fan(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12965 Issue: null Article Number: 129650A DOI: 10.1117/12.3007773 Published: 2023
Abstract:Accord1ing to requirements, a co-aperture design has been performed for the visible light remote sensing camera and the synthetic aperture radar, allowing the remote sensing satellite to acquire both visible light and radar images simultaneously. The front system is a two-mirror, no-focus system with a primary mirror diameter of 3 meters, serving to compress the beam. To avoid obstruction, the primary mirror is placed off-axis. The visible light component consists of an off-axis threemirror system, with the entrance pupil aligned with the exit pupil of the front system. All three mirrors are secondary mirrors with quadratic surfaces. The primary mirror size is 500mm, and the system's focal length is 7.22m. The overall ground resolution of the system reaches sub-meter level, with a full field of view measuring 0.8° × 0.03°. Optical design software ZEMAX was employed to evaluate the imaging quality within the visible light wavelength range. The results indicate that the spot size of the system is smaller than 13μm within each field of view. At the Nyquist frequency, the modulation transfer function (MTF) values for each field of view exceed 0.4, approaching the diffraction limit, showcasing good imaging quality. This design enhances the satellite's adaptability and observational capabilities, reduces the overall size of the instrument, and saves on manufacturing and launch costs. ? 2023 SPIE. All rights reserved.
Accession Number: 20240215333275
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Record 354 of
Title:Multi-Perspective Long-Focus Camera Calibration Algorithm Based on Parallel Perspective Projection Model
Author(s):Ni, Siyu(1,2); Xue, Bin(1); Tao, Jinyou(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12963 Issue: null Article Number: 129631A DOI: 10.1117/12.3007788 Published: 2023
Abstract:To overcome the limitations of conventional long-focus camera calibration, this paper proposes an improved algorithm for calibrating multi-perspective long-focus cameras based on the parallel perspective projection model. The algorithm employs an affine approximation projection model to describe the imaging process of long-focus cameras. By capturing images of the same static scene from different viewpoints and utilizing multi-view images and bundle adjustment, the algorithm jointly estimates camera parameters, including focal length, distortion coefficients, and rotation matrices, facilitating rapid, flexible, and accurate calibration of long-focus cameras. Finally, the proposed algorithm is compared with the Zhang Zhengyou calibration algorithm by calibrating a Canon EOS 60D18-200 camera with a 100mm focal length. The precision and stability of the proposed algorithm are verified through comparison, laying a foundation for subsequent tasks in computer vision, such as 3D reconstruction and image fusion. ? 2023 SPIE. All rights reserved.
Accession Number: 20240215330726
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Record 355 of
Title:Monolithic scintillator PET detector by using light sharing between adjacent detector modules
Author(s):Sun, M.D.(1); Zhang, C.H.(2); He, Z.(1); Wang, H.J.(1)
Source: Journal of Instrumentation Volume: 18 Issue: 5 Article Number: P05044 DOI: 10.1088/1748-0221/18/05/P05044 Published: May 1, 2023
Abstract:A monolithic crystal-based positron emission tomography (PET) detector has a low cost and high sensitivity and allows determining 3D positions by scintillation light distribution. However, the edge effect inherent to scintillators deteriorates the position resolution of the detector toward the crystal borders due to the escape and reflection of the scintillation light. An increase in crystal thickness will improve the detection efficiency, but the edge effect becomes severe. To improve the position resolution and detection efficiency of scintillators, the light-sharing technique is developed. Two identical trapezoidal monolithic cerium-doped lutetium yttrium orthosilicate (LYSO) crystals with a bottom size of 25.80 × 25.80 mm2 and a thickness of 20 mm are optically coupled at one lateral face by an optical medium. The scintillation light near the optically coupled interface is jointly collected by two adjacent 8 × 8 SiPM arrays from the bottom faces. The SiPM signals are individually read out and processed by using the multichannel readout application-specific integrated circuits (ASICs) of TOFPET2 to provide a light distribution. The transverse positions and depth of interaction (DOI) are calculated from the measured light distribution. As expected, the optical glue with a refractive index of n = 1.68 shows better light sharing between two LYSO crystals than the coupling media of silicon grease (n = 1.40) and air. For the 20 mm thick monolithic LYSO-based PET detector, the transverse position resolution near the crystal edge is improved by nearly 30% by using the light-sharing method compared with the black-painted treatment. However, the DOI resolution near the edge of the crystal is not significantly improved, which may be attributed to the incomplete collection of scintillation light. The DOI resolution of the detector would be improved by using electronics with lower noise and SiPM arrays with smaller pixel. ? 2023 IOP Publishing Ltd and Sissa Medialab.
Accession Number: 20232214173394
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Record 356 of
Title:Image Processing Algorithm Design for Low-Light EBCMOS Devices Based on FPGA
Author(s):Cao, Yi(1); Wei, Na(1); Zhu, Xiangping(1); Ma, Jun(2)
Source: 2023 3rd International Conference on Electronic Information Engineering and Computer Communication, EIECC 2023 Volume: null Issue: null Article Number: null DOI: 10.1109/EIECC60864.2023.10456650 Published: 2023
Abstract:In this study, a hardware platform based on the Xilinx 7-series Field-Programmable Gate Array (FPGA) is employed. The design of a Static Storage Control Module and a Median Filtering Module is accomplished through programming in the Verilog hardware description language using Vivado software. The functionality of these modules is rigorously verified through logical validation using Modelsim software. The algorithm is applied to process low-light images captured by a custom EBCMOS image sensor. Comparative analysis with software testing platforms reveals a substantial improvement in image processing speed when utilizing the FPGA-based hardware resources. This improvement allows the processing of 1 pixel per clock cycle. As a result, this work lays the foundation for the design of lightweight, integrated data acquisition systems for the nextgeneration night vision helmet systems. ? 2023 IEEE.
Accession Number: 20241415845461
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Record 357 of
Title:Current Status and Development Tendency of Image Motion and Compensation About Space Based on Optical Imaging System（Invited）
Author(s):Hao, Wei(1,2); Yan, Peipei(1,2); Li, Zhiguo(1,2); Cheng, Zhiyuan(1,2); She, Wenji(1,2)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 52 Issue: 6 Article Number: 0611001 DOI: 10.3788/gzxb20235206.0611001 Published: June 2023
Abstract:Along with the development and progress of science and technology，the image quality will be affected by variation of orbit，attitude angle and other factors，as well as tracking speed errors，platform and moving parts jitter. All of these factors will cause image motion，which will lead to image resolution reduction，image blurring and image quality declined. Therefore，how to suppress the impact of dynamic image motion becomes the bottleneck of obtaining high-resolution images. At present， the existed researches basically analyze the factors of image motion from a separate application field. They do not present the generation and compensation technology of image motion of space-based optical system systematically and comprehensively. How to suppress the influence of dynamic image shift gradually has become the bottleneck of obtaining high-resolution and clear images. Compared to the conventional ground-based telescope，the space one can get away from the distortions of the Earth’s atmosphere. So less background noise，wider optical wavebands and higher imaging precision to the diffraction limit can be achieved. This paper analyzes the various factors that produce image shifts during the imaging process of the space-based space target optical system and on this basis，comprehensively analyzes and locates the factors that affect the quality of dynamic imaging. Aiming at the problem of unclear imaging caused by dynamic image movement in the process of space high-speed moving target tracking，the degradation mechanism is analyzed，and the satellite platform disturbance，moving base tracking stability，stray light，defocusing，and imaging distance within the integration time are analyzed in detail. The influence of factors such as changes on the dynamic MTF is given，and the mathematical model corresponding to each influencing factor is given. An image motion compensation scheme based on FSM is given，which has been verified by laboratory tests and can effectively reduce the impact of image motion. During the space camera's on-orbit working process，vibration caused by reaction wheel assembles；solar panels and lower frequency can be compensated and suppressed by attitude controllers. While vibration with a smaller amplitude and higher frequency will still convey through the platform to the sensor，resulting in subtle jitter and weakened attitude stability of the sensor. Due to the tiny unit pixel view angle of high resolution sensor，jitter will lead to the image point of the ground scene indistinct and imaging quality declined in exposure time. With the development of spacecraft attitude control method，sensing，optical system design and manufacturing level，how to suppress the influence of dynamic image shift gradually It has become the bottleneck of obtaining high-resolution and clear images. In order to realize high resolution imaging，the space-based space target optical imaging system has higher and higher requirements for the spatial resolution of the payload，and a wider and wider range of motion adaptation of the space moving target. This paper sketches the mechanism of image motion influence and image motion compensation technologies. On the basis of that，this paper classifies space-based imaging according to the applications，such as remote sensing，space astronomical observation，Mars exploration and space target detection. Furthermore，we introduce in detail the research progress of image motion influence and compensation in the fields of remote sensing，space astronomical observation，Mars exploration and space target detection. This paper provides the research progress of image motion influence and compensation in the fields of domestic and international in recent years. Through analyzing the research，we can further improve our understanding of the development direction of space optical technology，and provide new methods and approaches for the development of space optical technology and equipment. ? 2023 Chinese Optical Society. All rights reserved.
Accession Number: 20233014444827
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Record 358 of
Title:Unsupervised real image super-resolution via knowledge distillation network
Author(s):Yuan, Nianzeng(1); Sun, Bangyong(1); Zheng, Xiangtao(2)
Source: Computer Vision and Image Understanding Volume: 234 Issue: null Article Number: 103736 DOI: 10.1016/j.cviu.2023.103736 Published: September 2023
Abstract:Super-resolution convolutional neural networks recently have demonstrated high-quality restoration for single images. Despite existing methods have achieved remarkable performance based on synthetic datasets, the performance is poor on real-world or natural data. To address this issue, zero-shot super-resolution (ZSSR) has been proposed for adaptive learning. However, ZSSR is unable to keep the simulated degradation process consistent with the degradation kernel of the real degradation process. Furthermore, the learned mapping of ZSSR is different from the desired mapping. In this paper, an unsupervised image super-resolution via knowledge distillation network (USRKDN) is proposed. Specifically, the proposed degradation module generates an image-specific degradation kernel and corresponding degenerated images. Moreover, the knowledge distillation module is proposed to solve the issue that the mapping cannot be completely equivalent, which transfers the learned map by knowledge distillation. The full convolution module is also explored to help the reconstruction of information. Extensive experimental results on synthetic and real datasets demonstrate the effectiveness of USRKDN. In addition, USRKDN is proven to be good at reconstructing image details in real scenes, which provides an effective method for generating information learning tasks with fewer samples. ? 2023 Elsevier Inc.
Accession Number: 20232514272482
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Record 359 of
Title:Generation of a vector conventional soliton via a graphene oxide saturable absorber
Author(s):Mei, Chao(1); Duan, Lina(2); Chang, Sansan(1); Guo, Xinyu(3); Yu, Jia(3)
Source: Applied Optics Volume: 62 Issue: 20 Article Number: null DOI: 10.1364/AO.492928 Published: July 2023
Abstract:We have experimentally observed an ultrashort conventional vector soliton in an erbium-doped fiber laser. The few-layered graphene oxide (GO) is used as a saturable absorber (SA). It is found that the saturable absorption characteristic of GO is polarization independent. Therefore, vector solitons can be obtained without polarization control by using such SA. By using a polarization beam splitter to split the mode-locked pulse obtained in the oscillator, two orthogonal polarization vector solitons with equal intensity and consistent characteristics can be obtained. It demonstrates that the initial soliton consists of two orthogonal polarization components. It is worth noting that these two orthogonal polarization component solitons improve the signal-to-noise ratio (SNR) of 3 dB compared with the initial soliton. The improvement in SNR is very significant and cannot be neglected. This phenomenon has not been reported before, to our knowledge. In addition, the conventional soliton generated by this mode-locked laser has a central wavelength of 1559 nm with 1.1 ps pulse duration. The mode-locking state of this laser can be self-started. After mode locking, the environmental stability is excellent. The experimental results indicate that GO as a broadband SA has great potential and application prospects in the field of vector soliton generation. ? 2023 Optica Publishing Group.
Accession Number: 20233214487854
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Record 360 of
Title:Research on Laser Cold Machining Hole Penetration Spectroscopy Detection Technology
Author(s):Yan, Qing(1); Peng, Bo(1); Wang, Li(1); Wang, Dong(1); Zhao, Hualong(2); Gao, Fei(1); Hua, Dengxin(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 52 Issue: 3 Article Number: 0352119 DOI: 10.3788/gzxb20235203.0352119 Published: March 2023
Abstract:The ultra-high peak power and ultra-short pulse time characteristics of the femtosecond laser allow it to act quickly on a specific area during machining，and the material in the area of the laser beam is removed in the form of a plasma eruption to achieve cold machining with almost no thermal impact on the surrounding material. Laser cold machining technology is widely used because of its high processing accuracy，small heat-affected zone and high machining efficiency. One of the important applications is the machining of air film holes in aero-engine turbine blades. Due to the existence of hollow cavities and the close distance between the opposite walls of the aero-engine turbine blades，the hole making process is prone to contramural damage. Therefore，in order to avoid contramural damage and improve the quality of air film hole machining，a real-time detecting system needs to be developed to judge the hole penetration status during the hole machining in real time. Laser Induced Breakdown Spectroscopy（LIBS）is a kind of atomic emission spectroscopy technology，which has a fast response time and can achieve real-time detection and analysis of the target under test. In the LIBS detection system，a spectrometer is used to collect the emission spectra excited during the plasma cooling process of femtosecond laser machining，and the elements corresponding to each spectral line can be identified according to the characteristic wavelength of atomic or ion emission spectra in a specific wavelength band，and quantitative analysis can be achieved by measuring the intensity of emission spectra captured at a specific wavelength. Aiming at the problem of contramural damage in the machining of aero-engine turbine blade with femtosecond laser， a hole penetration detection scheme based on laser-induced breakdown spectroscopy detection technology of femtosecond laser hole making is proposed. Based on the elemental analysis of the material and the information of the LIBS spectrogram obtained in the wavelength 520~560 nm during processing，the emission spectrum of Cr（I）521.531 nm is selected as the characteristic spectral line，and the change in intensity of the characteristic spectral line is used to realize the judgment of the hole machining process. In this paper，we design a laser cold machining hole penetration spectroscopy detection system consisting of an ultrashort pulse laser，a grating spectrometer，a focusing optical path and an upper computer for data processing and analysis. The effect of important machining parameters on the detection performance of LIBS is studied experimentally，and the effect of machining parameters on the spectral intensity is analyzed，and the optimized machining parameters are selected as laser energy of 32 W，the distance of the part to be processed from the focus of 150 mm，and the laser spin speed of 2 400 r/min. The designed hole penetration detection system is used to continuously collect and analyze the plasma spectra during the actual hole machining，and the correspondence between the specific spectral intensity and the penetration state of the sample to be processed in the hole machining is obtained. The intensity of the spectrum peaks at the beginning of the hole punching because of the high percentage of upward reflection of the atomic emission spectra during the laser exit stage；the overall intensity of the atomic emission spectra gradually decreases as the hole depth increases；the detected intensity of the atomic emission spectra starts to decrease significantly when the hole starts to penetrate gradually；when the hole is completely penetrated，there are no reflected back characteristic spectral lines and only background noise with spectral line intensity less than 230. The experimental results verify the feasibility of the method in solving the problem of preventing damage to the opposite wall during femtosecond laser hole machining，and can provide real-time feedback on the completion of hole processing to help the development of the feedback system，which is conducive to the further optimization of laser cold machining technology in terms of accuracy and efficiency. ? 2023 Chinese Optical Society. All rights reserved.
Accession Number: 20231713945967
