2024

• Record 325 of
  
  Title:Fatigue mechanism analysis and life prediction model of piezoelectric ceramic tube based on fiber-optic nutator
  
  Author(s):Peng, Bo(1,2,3); Ruan, Ping(1,3); Han, Junfeng(1,3); Chang, Zhiyuan(1,3); Han, Jingyu(1,2,3); Wang, Jiahao(1,2,3); He, Deqiu(1,2,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 13068  Issue:   DOI: 10.1117/12.3016249  Published: 2024  
  Abstract:As a driving unit and core component of the acquisition, pointing and tracking (APT) system's fiber actuator, the fatigue mechanism and fatigue life analysis of the piezoelectric ceramic tube (PCT) nutator in a high-frequency dynamic state have become one of the urgent research issues in the reliability field of interstellar laser communicating key devices. This article commences by elucidating the principles of deflection and nutation of the PCT nutator. Subsequently, employing finite element simulation methodologies, an exhaustive analysis is conducted to discern the stress and strain energy density distribution within a single operational cycle under specific working parameters. The findings illuminate the principal fatigue failure mechanism of the dynamic piezoelectric ceramic tube, characterized by crack propagation and eventual rupture resulting from localized stress accumulation during dynamic processes. Furthermore, the coordinates of the "most dangerous element" are ascertained, and a fatigue life model for the PCT nutator in transient nutation is proposed based on the theory of material fatigue damage accumulation. Based on model calculations, the theoretical fatigue life of the PCT nutator can reach 2.31×106 cycles under the environmental conditions with a 500Hz bandwidth and maximum nutation radius. © 2024 SPIE.
  Accession Number: 20240715542577
• Record 326 of
  
  Title:Nanosecond pulse X-ray emission source based on ultrafast laser modulation
  
  Author(s):Li, Yun(1,2); Su, Tong(1); Sheng, Li-Zhi(1); Zhang, Rui-Li(1); Liu, Duo(3); Liu, Yong-An(1); Qiang, Peng-Fei(1); Yang, Xiang-Hui(1); Xu, Ze-Fang(1,2)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 73  Issue: 4  DOI: 10.7498/aps.73.20231505  Published: 2024  
  Abstract:In response to the growing demand for miniaturized ultrafast pulsed X-ray sources in the fields of fundamental science and space applications, we design and develop an ultrafast pulsed X-ray generator based on a laser-modulated light source and a photoelectric cathode. This innovative technology addresses the limitations commonly encountered in traditional X-ray emission devices, such as low repetition rate, insufficient time stability, and suboptimal pulse characteristics. Our effort is to study and develop the ultrafast modulation control module for the pulsed X-ray generator. This effort results in achieving high levels of time accuracy and stability in ultrafast time-varying photon signals. Moreover, we successfully generate nanosecond pulsed X-rays by using a laser-controlled light source. Theoretically, we establish a comprehensive time response model for the pulsed X-ray generator in response to short pulses. This includes a thorough analysis of the time characteristics of the emitted pulsed X-rays in the time domain. Experimentally, we conduct a series of tests related to various time-related parameters of the laser-controlled light source. Additionally, we design and implemente an experimental test system for assessing the time characteristics of pulsed X-rays, by using an ultrafast scintillation detector. The experimental results clearly demonstrate that our pulsed X-ray generator achieves impressive capabilities, including high repetition rates (12.5 MHz), ultrafast pulses (4 ns), and exceptional time stability (400 ps) in X-ray emission. These results closely align with our established theoretical model. Compared with traditional modulation techniques, our system exhibits significant improvement in pulse time parameters, thereby greatly expanding its potential applications. This research provides a valuable insight into achieving ultra-high time stability and ultrafast pulsed X-ray emission sources. These advances will further enhance the capabilities of X-ray technology for scientific research and space applications. © 2024 Chinese Physical Society.
  Accession Number: 20241515855160
• Record 327 of
  
  Title:A Snapshot Multi-Spectral Demosaicing Method for Multi-Spectral Filter Array Images Based on Channel Attention Network
  
  Author(s):Zhang, Xuejun(1,2); Dai, Yidan(1,2); Zhang, Geng(1); Zhang, Xuemin(3); Hu, Bingliang(1)
  Source: Sensors  Volume: 24  Issue: 3  DOI: 10.3390/s24030943  Published: February 2024  
  Abstract:Multi-spectral imaging technologies have made great progress in the past few decades. The development of snapshot cameras equipped with a specific multi-spectral filter array (MSFA) allow dynamic scenes to be captured on a miniaturized platform across multiple spectral bands, opening up extensive applications in quantitative and visualized analysis. However, a snapshot camera based on MSFA captures a single band per pixel; thus, the other spectral band components of pixels are all missed. The raw images, which are captured by snapshot multi-spectral imaging systems, require a reconstruction procedure called demosaicing to estimate a fully defined multi-spectral image (MSI). With increasing spectral bands, the challenge of demosaicing becomes more difficult. Furthermore, the existing demosaicing methods will produce adverse artifacts and aliasing because of the adverse effects of spatial interpolation and the inadequacy of the number of layers in the network structure. In this paper, a novel multi-spectral demosaicing method based on a deep convolution neural network (CNN) is proposed for the reconstruction of full-resolution multi-spectral images from raw MSFA-based spectral mosaic images. The CNN is integrated with the channel attention mechanism to protect important channel features. We verify the merits of the proposed method using 5 × 5 raw mosaic images on synthetic as well as real-world data. The experimental results show that the proposed method outperforms the existing demosaicing methods in terms of spatial details and spectral fidelity. © 2024 by the authors.
  Accession Number: 20240715548327
• Record 328 of
  
  Title:Research progress on hyperspectral anomaly detection
  
  Author(s):Qu, Bo(1,2,3); Zheng, Xiangtao(1); Qian, Xueming(2); Lu, Xiaoqiang(1)
  Source: National Remote Sensing Bulletin  Volume: 28  Issue: 1  DOI: 10.11834/jrs.20232405  Published: 2024  
  Abstract:The applications of remote sensing images in numerous fields have been increasing with the continuous development of aerospace and remote sensing technologies. HyperSpectral Image (HSI) is a common type of remote sensing image that comprises a series of two-dimensional remote sensing images as a 3D data cube. Each two-dimensional image in HSI can reveal the reflection/radiation intensity of different wavelengths of electromagnetic waves, and each pixel of HSI corresponds to the spectral curve reflecting the spectral information in different wavelengths. Therefore, the hyperspectral remote sensing images are characterized by"spatial-spectral integration," which contains not only spectral information with strong discriminant but also rich spatial information. Therefore, the hyperspectral data have considerable application potential. Hyperspectral anomaly detection aims to detect pixels in a scene with different characteristics from surrounding pixels and determines them as anomalous targets without any previous knowledge of the target. Hyperspectral anomaly detection is an unsupervised process that does not require any priori information regarding the target to be measured in advance; thus, this type of detection plays a crucial role in real life. For example, anomaly target detection technology can be used to search and rescue people after a disaster, quickly determine the fire point of a forest fire, and search mineral points in mineral resource exploration. Hyperspectral anomaly detection has been a popular research direction in the area of remote sensing image processing in recent years, and a numerous researchers have conducted extensive research and achieved rich research results. However, hyperspectral anomaly detection still encounters many difficult problems. For example, the targets of the same material may exhibit various spectral characteristics due to the different imaging equipment and environment, which may interfere with the detection results and lead to the problem of"same object with different spectra."Meanwhile, the targets of different materials may also exhibit the problem of"different objects with different spectra."Then, most of the existing hyperspectral anomaly detection algorithms are only in the laboratory stage and with low technology maturity. Furthermore, the hyperspectral data may have numerous spectral bands that contain a considerable amount of redundant information, which increases the difficulty of data processing. Moreover, the number of publicly available hyperspectral anomaly detection datasets is insufficient and mostly old. In this paper, the main research progress of hyperspectral anomaly detection is first summarized. The existing mainstream algorithms are then classified and summarized. These algorithms are mainly divided into five categories: statistics-based anomaly detection methods, data expression-based anomaly detection methods, data decomposition-based anomaly detection methods, deep learning-based anomaly detection methods, and other methods. Through the investigation, analysis, and summary of the existing methods, three future development directions of hyperspectral anomaly detection are proposed. (1) Database expansion: new datasets with additional images and highly sophisticated remote sensing sensors are introduced. (2) Multisource data combination: the advantages of different imaging sensors and various types of remote sensing data are maximized. (3) Algorithm practicality: the anomaly detection algorithms are relayed for application on real platforms. © 2024 Science Press. All rights reserved.
  Accession Number: 20241515892466
• Record 329 of
  
  Title:Material removal and surface generation mechanisms in rotary ultrasonic vibration–assisted aspheric grinding of glass ceramics
  
  Author(s):Sun, Guoyan(1,2); Wang, Sheng(3); Zhao, Qingliang(3); Ji, Xiabin(1); Ding, Jiaoteng(1)
  Source: International Journal of Advanced Manufacturing Technology  Volume: 130  Issue: 7-8  DOI: 10.1007/s00170-023-12904-x  Published: February 2024  
  Abstract:High-efficiency precision grinding can shorten the machining cycle of aspheric optical elements by a factor of 2–10. To achieve this objective, ultrasonic vibration (UV)–assisted grinding (UVG) has been increasingly applied to manufacture aspheric optics. However, the mechanisms of material removal and surface formation in UV-assisted aspheric grinding of glass ceramics have rarely been studied. Herein, rotary UV-assisted vertical grinding (RUVG) was used to explore the machining mechanism of coaxial curved surfaces. First, RUV-assisted scratch experiments were conducted on aspheric surface of glass ceramics, which exhibited multiple benefits over conventional scratching. These include a reduction in the scratch force by 37.83–44.55% for tangential component and 3.87–28.15% for normal component, an increase in plastic removal length by 43.75%, and an increase in material removal rate by almost a factor of 2. Moreover, grinding marks on the aspheric surface in RUVG were accurately simulated and optimized by adjusting grinding parameters. RUVG experiments were performed to verify the accuracy of grinding texture simulations and investigate the UV effect. The results demonstrate that UV can improve the surface quality of aspheric grinding when compared with conventional vertical grinding. In particular, the total height of the profile of form accuracy and its root mean square were significantly improved by a factor of 3.38–4.54 and 7.15–10.82, respectively, and the surface roughness reduced by 10.03–12.10%. This study provides deeper insight into material removal and surface generation mechanisms for RUVG of aspheric surfaces, and it is thus envisaged that these results will be useful in engineering applications. © 2024, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.
  Accession Number: 20240215352394
• Record 330 of
  
  Title:Influence of nutating deflection on fiber coupling efficiency for fiber optic nutator
  
  Author(s):Peng, Bo(1,2,3); Ruan, Ping(1,3); Wang, Xingfeng(1,3); Han, Junfeng(1,3); Chang, Zhiyuan(1,3); Han, Jingyu(1,2,3)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 13104  Issue:   DOI: 10.1117/12.3023648  Published: 2024  
  Abstract:In the relay optics of the space laser communication terminal's Acquisition, Pointing, and Tracking (APT) system, the Fiber Optic Nutator (FON), based on a Piezoelectric Ceramic Tube (PCT), is capable of actively achieving signal light reception and coupling through the implementation of energy feedback compensation algorithms with a lightweight design approach. Throughout the fiber nutation process, the deflection amplitude of the receiving fiber's end face significantly impacts the fiber coupling efficiency of the fiber optic nutator. To quantify this influence, the curve depicting the effect of the relative aperture (D/f) of the relay optics focusing lens on fiber coupling efficiency is initially computed. Notably, when D/f=0.213, the fiber coupling efficiency attains its theoretical maximum of 0.813. Subsequently, the composite motion of the fiber end face in three-dimensional space is deconstructed into radial and axial translations, along with rotations based on the axial direction. Through meticulous simulation calculations, it is ascertained that the fiber coupling efficiency decreases by more than 5% when the radial displacement r of the fiber end face exceeds 3.65μm, or when the axial displacement d surpasses 0.25mm, or when the angular deviation θ exceeds 0.08°. These findings offer quantifiable criteria for the dimensional selection of the PCT under varied application conditions, providing constructive guidance for determining core structural design parameters of the fiber optic nutator. © COPYRIGHT SPIE.
  Accession Number: 20241816027629
• Record 331 of
  
  Title:Phase correction strategy based on structured light fringe projection profilometry
  
  Author(s):Cao, Hongyan(1,2); Qiao, Dayong(1,2); Yang, Di(3)
  Source: Optics Express  Volume: 32  Issue: 3  DOI: 10.1364/OE.513572  Published: January 29, 2024  
  Abstract:Fringe projection profilometry based on structured light has been widely used in 3-D vision due to its advantages of simple structure, good robustness, and high speed. The principle of this technique is to project multiple orders of stripes on the object, and the camera captures the deformed stripe map. Phase unwrapping and depth map calculation are important steps. Still, in actual situations, phase ambiguity is prone to occur at the edges of the object. In this paper, an adaptive phase segmentation and correction (APSC) method after phase unwrapping is proposed. In order to effectively distinguish the stable area and unstable area of the phase, a boundary identification method is proposed to obtain the structural mask of the phase. A phase compensation method is proposed to improve the phase accuracy. Finally, we obtain the 3-D reconstruction result based on the corrected phase. Specific experimental results verify the feasibility and effectiveness of this method. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20240615499844
• Record 332 of
  
  Title:Research on the Effect of Vibrational Micro-Displacement of an Astronomical Camera on Detector Imaging
  
  Author(s):Liu, Bin(1); Guan, Shouxin(1); Wang, Feicheng(1); Zhang, Xiaoming(2); Yu, Tao(1); Wei, Ruyi(3,4,5)
  Source: Sensors  Volume: 24  Issue: 3  DOI: 10.3390/s24031025  Published: February 2024  
  Abstract:Scientific-grade cameras are frequently employed in industries such as spectral imaging technology, aircraft, medical detection, and astronomy, and are characterized by high precision, high quality, fast speed, and high sensitivity. Especially in the field of astronomy, obtaining information about faint light often requires long exposure with high-resolution cameras, which means that any external factors can cause the camera to become unstable and result in increased errors in the detection results. This paper aims to investigate the effect of displacement introduced by various vibration factors on the imaging of an astronomical camera during long exposure. The sources of vibration are divided into external vibration and internal vibration. External vibration mainly includes environmental vibration and resonance effects, while internal vibration mainly refers to the vibration caused by the force generated by the refrigeration module inside the camera during the working process of the camera. The cooling module is divided into water-cooled and air-cooled modes. Through the displacement and vibration experiments conducted on the camera, it is proven that the air-cooled mode will cause the camera to produce greater displacement changes relative to the water-cooled mode, leading to blurring of the imaging results and lowering the accuracy of astronomical detection. This paper compares the effects of displacement produced by two methods, fan cooling and water-circulation cooling, and proposes improvements to minimize the displacement variations in the camera and improve the imaging quality. This study provides a reference basis for the design of astronomical detection instruments and for determining the vibration source of cameras, which helps to promote the further development of astronomical detection. © 2024 by the authors.
  Accession Number: 20240715548318
• Record 333 of
  
  Title:A neighbourhood feature-based local binary pattern for texture classification
  
  Author(s):Lan, Shaokun(1); Li, Jie(1); Hu, Shiqi(2); Fan, Hongcheng(3); Pan, Zhibin(1,4)
  Source: Visual Computer  Volume: 40  Issue: 5  DOI: 10.1007/s00371-023-03041-3  Published: May 2024  
  Abstract:The CNN framework has gained widespread attention in texture feature analysis; however, handcrafted features still remain advantageous if computational cost needs to take precedence and in cases where textures are easily extracted with few intra-class variation. Among the handcrafted features, the local binary pattern (LBP) is extensively applied for analysing texture due to its robustness and low computational complexity. However, in local difference vector, it only utilizes the sign component, resulting in unsatisfactory classification capability. To improve classification performance, most LBP variants employ multi-feature fusion. Nevertheless, this can lead to redundant and low-discriminative sub-features and high computational complexity. To address these issues, we propose the neighbourhood feature-based local binary pattern (NF-LBP). Inspired by gradient’s definition, we extract the neighbourhood feature in a local region by simply using the first-order difference and 2-norm. Next, we introduce the neighbourhood feature (NF) pattern to describe intensity changes in the neighbourhood. Finally, we combine the NF pattern with the local sign component and the centre pixel component to create the NF-LBP descriptor. This approach provides better complementary texture information to traditional local sign pattern and is less sensitive to noise. Additionally, we use an adaptive local threshold in the encoding scheme. Our experimental results of classification accuracy and F1 score on five texture databases demonstrate that our proposed NF-LBP method attains outstanding texture classification performance, outperforming existing state-of-the-art approaches. Furthermore, extensive experimental results reveal that NF-LBP is strongly robust to Gaussian noise and salt-and-pepper noise. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023. corrected publication 2023.
  Accession Number: 20233414605121
• Record 334 of
  
  Title:Electron vortices generation of photoelectron of H 2 + by counter-rotating circularly polarized attosecond pulses
  
  Author(s):Yang, Haojing(1); Liu, Xiaoyu(1); Zhu, Fengzheng(2); Jiao, Liguang(3,4); Liu, Aihua(1,5)
  Source: Chinese Physics B  Volume: 33  Issue: 1  DOI: 10.1088/1674-1056/ad011a  Published: January 1, 2024  
  Abstract:Molecular-frame photoelectron momentum distributions (MF-PMDs) of an H 2 + molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrödinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counter-rotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distance-dependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs. © 2024 Chinese Physical Society and IOP Publishing Ltd
  Accession Number: 20240515465957
• Record 335 of
  
  Title:FPM-WSI: Fourier ptychographic whole slide imaging via feature-domain backdiffraction
  
  Author(s):Zhang, Shuhe(1,2,3); Wang, Aiye(1,4); Xu, Jinghao(1,4); Feng, Tianci(1,4); Zhou, Jinhua(3); Pan, An(1,4)
  Source: arXiv  Volume:   Issue:   DOI: 10.48550/arXiv.2402.18270  Published: February 28, 2024  
  Abstract:Fourier ptychographic microscopy (FPM), characterized by high-throughput computational imaging, theoretically provides a cunning solution to the trade-off between spatial resolution and field of view (FOV), which has a promising prospect in the application of digital pathology. However, block reconstruction and then stitching has currently become an unavoidable procedure due to vignetting effects. The stitched image tends to present color inconsistency in different image segments, or even stitching artifacts. Consequently, the advantages of FPM are not as pronounced when compared to the conventional scanning-and-stitching schemes widely employed in whole slide imaging (WSI) systems. This obstacle significantly impedes the profound advancement and practical implementation of FPM, explaining why, despite a decade of development, FPM has not gained widespread recognition in the field of biomedicine. In response, we reported a computational framework based on feature-domain backdiffraction to realize full-FOV, stitching-free FPM reconstruction. Different from conventional algorithms that establish the loss function in the image domain, our method formulates it in the feature domain, where effective information of images is extracted by a feature extractor to bypass the vignetting effect. The feature-domain error between predicted images based on estimation of model parameters and practically captured images is then digitally diffracted back through the optical system for complex amplitude reconstruction and aberration compensation. Through massive simulations and experiments, the method presents effective elimination of vignetting artifacts, and reduces the requirement of precise knowledge of illumination positions. We also found its great potential to recover the data with a lower overlapping rate of spectrum and to realize automatic blind-digital refocusing without a prior defocus distance. Furthermore, to the best of our knowledge, we firstly demonstrated application of FPM on a WSI system, termed FPM-WSI. This platform enables full-color, high-throughput imaging (4.7 mm diameter FOV, 336 nm half-pitch resolution with blue channel illumination) without blocking-and-stitching procedures for a batch of 4 slides. The platform also possesses autofocusing, shifting and regional recognition of slides that are completed by additional automatic mechanical hardware, and the acquisition time for a single slide is less than 4 s. In addition, we provide a user-friendly operation interface to facilitate the workflow, and alternative colorization schemes to choose from. The impact of the reported platform, with advantages of high-quality, high-speed imaging and low cost, will be far-reaching and desired in many fields of biomedical research, as well as in clinical applications. © 2024, CC BY-NC-SA.
  Accession Number: 20240098566
• Record 336 of
  
  Title:Theoretical derivation and application of empirical Harvey scatter model
  
  Author(s):Ma, Zhanpeng(1,2); Wang, Hu(1,2,3); Chen, Qinfang(1,2); Xue, Yaoke(1,2,4,5); Yan, Haoyu(1,2,3); Liu, Jiawen(1,2,3)
  Source: Optics Express  Volume: 32  Issue: 6  DOI: 10.1364/OE.519414  Published: March 11, 2024  
  Abstract:Starting from the Rayleigh-Rice perturbation theory, this paper derives the empirical Harvey scatter model and ABg scatter model applied extensively in optical analysis software packages and verifies the shift-invariant behavior of the scattered radiance in direction cosine space. Using data obtained from multi-wavelength laser scatterometer on carbon nanotube black coating and pineblack coating, we establish the polynomial model based on the sine of the scattering angle plus the sine of the specular reflection angle, i.e., sin θs+sin θ0 and the dual-Harvey model based on sin θs-sin θ0 , respectively. The models are in good accordance with the experimental data and further extend the valid range of empirical models. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20241215761907