2024

• Record 157 of
  
  Title:Environmentally stable all-fiber femtosecond laser for industrial application based on a SESAM mode-locked ytterbium-doped laser
  
  Author(s):Cao, Xue(1,2,3); Li, Feng(1); Song, Dongdong(1); Wang, Yishan(1); Li, Qianglong(1,2,3); Zhao, Hualong(1); Zhao, Wei(1); Wen, Wenlong(1); Si, Jinhai(2)
  Source:Microwave and Optical Technology Letters
  Volume: 66  Issue: 4  DOI: 10.1002/mop.34119  Published: April 2024  
  Abstract:We demonstrate an environmentally stable femtosecond laser for industrial application based on all polarization-maintaining Yb-doped laser and experimentally explore the effect of the net cavity dispersion (NCD) on output characteristics. The oscillator emits pulses with 5.1 ps and a 23 nm spectral bandwidth, then the pulse is compressed to 88 fs. The instabilities over 120 h gives 0.32% relative root mean square noise, indicating high stability of the pulse laser. With effective regulation of NCD, we obtained the maximum spectral bandwidth of 27 nm. Such broadband oscillator with compact all-fiber configurations provide extremely high stability should be very attractive for long-term industrial application. © 2024 Wiley Periodicals LLC.
  Accession Number: 20241315798070
• Record 158 of
  
  Title:Optical Design of High-compression Ratio and Low-wavefront Error Gravitational Wave Detection Telescope
  
  Author(s):Liang, Rong(1,2); Zhou, Xiaojun(1); Zou, Chunbo(3); Xu, Huangrong(1); Li, Chenxi(1); Yu, Tao(1,2); Yu, Weixing(1,2)
  Source:Guangzi Xuebao/Acta Photonica Sinica
  Volume: 53  Issue: 1  DOI: 10.3788/gzxb20245301.0122002  Published: January 2024  
  Abstract:Since the first detection of gravitational wave，gravitational wave astronomy has advanced swiftly. As a crucial component of the detection system，the gravitational wave telescope is obviously crucial. The highly stable laser telescope with a low wavefront error and a high suppression ratio of stray light is a crucial medium for the detection of gravitational waves，as it must not only transmit energy in the order of watt to distant spacecraft，but also receive weak laser signals in the order of picowatt from other satellite base station located millions of kilometers away. Therefore，the backward stray light of the local telescope is required to reach 10−10 orders of the incident laser power. Considering the requirements of small size，light weight，and high compactness，it is clear that the benefits of a reflective system cannot be compared to those of a transmission design. In general，the coaxial Cassegrain structure and off-axis multi-mirror structure are utilized. The off-axis design is preferred over the coaxial design for gravitational wave telescopes due to advantages such as the ability to optimize multiple parameters，the absence of a central obstruction，and the high energy collection capacity. In this paper，based on the design of off-axis four-mirror and the theory of coaxial reflection system，we designed and optimized the telescope combined with the characteristics of high magnification，low wavefront error and high suppression ratio of stray light. In the capture field of view of ±200 µrad，we realized the compression ratio of 100 of telescope，and the entrance pupil diameter of the principle system is 300 mm，whose design result of wavefront error is less than of λ/80 because the actual outgoing wavefront error must be less than λ/40. The system distortion of the edge field is less than 0.056 9%. In order to verify the processing and alignment of the principle system as well as the ability of stray light suppression of it，a 0.5 times scale system is established beneath the system with a wavefront error less than λ/175. Internal stray light is suppressed by increasing the light turning angle between the tertiary mirror and quaternary mirror on the condition of low wavefront error of λ/80. The optimized deflection angle of the tertiary mirror is 5.5 degrees，and the tertiary mirror is the plane surface，which can significantly reduce the difficulty of processing and alignment. A simulation of stray light is applied to analyze the stray light of our designed telescope. The steps of stray light analysis consist of the following steps：1）selection and optimization of the optical structure；2）model setting of the corresponding reflection，scattering，and absorption surfaces；3）stray light analysis of the entire system；4）iterative optimization design；5）fulfillment of the system's requirements. Therefore，we investigated the optical paths and power of the backscattered stray light. After positioning the field stop in the middle image plane between the secondary mirror and the tertiary mirror，the proportion of the stray light caused by the secondary mirror is the smallest. The stray light energy caused by the tertiary mirror and the quaternary mirror is the largest，which can reach more than 90%. The tolerance of the optical design is also analyzed，and the results of the analysis indicate that the tolerance of the parabolic primary mirror has the strongest impact on the wavefront error of the system. The principle system has a 90% cumulative probability wavefront error less than λ/40，which can satisfy the design requirement of gravitational wave detection and have the potential to play a significant role in future missions aimed at low wavefront error，high magnification and a high suppression ratio of stray light in the telescope while detecting gravitational waves. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20240815579474
• Record 159 of
  
  Title:Study on Stray Light Testing and Suppression Techniques for Large-Field of View Multispectral Space Optical Systems
  
  Author(s):Lu, Yi(1); Xu, Xiping(1); Zhang, Ning(1); Lv, Yaowen(1); Xu, Liang(2)
  Source:IEEE Access
  Volume: 12  Issue:   DOI: 10.1109/ACCESS.2024.3369471  Published: 2024  
  Abstract:To evaluate the ability of space optical systems to suppress off-axis stray light, this paper proposes a stray light testing method for large-field of view, multispectral spatial optical systems based on point source transmittance (PST). And a stray light testing platform was developed using a high-brightness simulated light source, large-aperture off-axis reflective collimator, high-precision positioning mechanism and a double column tank to evaluate the stray light PST index of spatial optical system. On the basis of theoretical analyses, a set of calibration lenses and stray light elimination structures such as hoods, baffle and stop are designed for the accuracy calibration of stray light testing systems. The theoretical PST values of the calibration lens at different off-axis angles are analyzed by Trace Pro software simulation and compared with the measured values to calibrate the accuracy of the system. The testing results show that the PST measurement range of the system reaches 10-3 ~10-10 when the off-axis angles of the calibration lens are in the range of ±5? ~ ±60?. The stray light test system has the advantages of wide working band, high automation and large dynamic range, and its test results can be used in the correction of lens hood and other applications. © 2013 IEEE.
  Accession Number: 20240915654572
• Record 160 of
  
  Title:Multi-Objective Topology Optimization of Acquisition Pointing and Tracking System
  
  Author(s):Gao, Bo(1,2,3); Yang, Hongtao(1,2); Chen, Weining(1,3); Wang, Hao(1); Fei, Jiaqi(1); Qi, Zimiao(2)
  Source:International Journal of Pattern Recognition and Artificial Intelligence
  Volume: 38  Issue: 6  DOI: 10.1142/S0218001424560032  Published: May 1, 2024  
  Abstract:There is a growing need for the lightweight acquisition, tracking, and pointing (APT) system during satellite launches due to the escalating demand in space missions. The APT system may work under multiple loading cases during different launch steps. Hence, this study introduces an innovative amalgamation of genetic operation and bi-directional evolutionary structural optimization (BESO) to fulfill the multi-objective requirements through the attainment of Pareto optimal fronts. A typical instance in two dimensions illustrates the effectiveness of the innovative multi-objective approach by contrasting the outcomes acquired from a solitary fulfillment requirement under two distinct burdens. Furthermore, the novel multi-objective method is utilized to remove inefficient material from the APT system by 20.12%. To ensure the safety of the lightweight design, the simulation and experiment of random vibration are both investigated according to the fundamental natural frequency of the launcher. © 2024 World Scientific Publishing Company.
  Accession Number: 20242316207436
• Record 161 of
  
  Title:Mural Anomaly Region Detection Algorithm Based on Hyperspectral Multiscale Residual Attention Network
  
  Author(s):Guo, Bolin(1,2); Qiu, Shi(1); Zhang, Pengchang(1); Tang, Xingjia(3)
  Source:Computers, Materials and Continua
  Volume: 81  Issue: 1  DOI: 10.32604/cmc.2024.056706  Published: 2024  
  Abstract:Mural paintings hold significant historical information and possess substantial artistic and cultural value.However, murals are inevitably damaged by natural environmental factors such as wind and sunlight, as well as by human activities. For this reason, the study of damaged areas is crucial formural restoration. These damaged regions differ significantly from undamaged areas and can be considered abnormal targets. Traditional manual visual processing lacks strong characterization capabilities and is prone to omissions and false detections. Hyperspectral imaging can reflect the material properties more effectively than visual characterization methods. Thus, this study employs hyperspectral imaging to obtain mural information and proposes a mural anomaly detection algorithm based on a hyperspectral multi-scale residual attention network (HM-MRANet). The innovations of this paper include: (1) Constructing mural painting hyperspectral datasets. (2) Proposing a multi-scale residual spectral-spatial feature extraction module based on a 3D CNN (Convolutional Neural Networks) network to better capture multiscale information and improve performance on small-sample hyperspectral datasets. (3) Proposing the Enhanced Residual Attention Module (ERAM) to address the feature redundancy problem, enhance the network's feature discrimination ability, and further improve abnormal area detection accuracy. The experimental results show that theAUC(AreaUnderCurve), Specificity, andAccuracy of this paper's algorithmreach 85.42%, 88.84%, and 87.65%, respectively, on this dataset. These results represent improvements of 3.07%, 1.11% and 2.68% compared to the SSRN algorithm, demonstrating the effectiveness of this method for mural anomaly detection. © 2024 The Authors. Published by Tech Science Press.
  Accession Number: 20244317244003
• Record 162 of
  
  Title:Design of multi-channel sequential front light imaging system for transient condition
  
  Author(s):Zhang, Zhanfei(1); Huang, Jie(2); Song, Qiang(2); Feng, Fei(1); Ding, Jianwen(2)
  Source:Guangxue Jingmi Gongcheng/Optics and Precision Engineering
  Volume: 32  Issue: 4  DOI: 10.37188/OPE.20243204.0478  Published: February 2024  
  Abstract:In order to obtain stable and high-quality sequential images under transient condition and different object distances, a four-channel sequential front light high-speed imaging system was designed. The system used image space parallel light splitting, taking the imaging principle as the starting point to analyze the key design elements of system. Based on the theoretical calculation parameters, the sub-lens groups (objective lens group, field mirror and collimating lens group, converging lens group) was designed and aberrations were independently corrected. Adding field mirror to reduce the size and weight of system and improve light energy utilization. The transmission effect of beam was improved by accurate connection of field of view and pupil. On this basis, the sub lens groups were integrated and optimized, and beam splitters were added to form the final four-channel sequential front light imaging system. The object distance adjustable optical path was designed, and the image quality of system at the object distance of 0.5 m~∞ was guaranteed by adjusting the handwheel of objective lens group in use, while keeping the position of primary image plane unchanged, enhancing the stability of system performance stability and reducing the difficulty of installation and adjustment. The receiving part of system can be replaced according to actual needs, and the system can be expanded to eight-channel system after adding splitters in the beam splitting region. The installed and adjusted sequential front-light imaging system is used for laboratory testing and field tests, and main optical performance is good. the resolution of each channel can reach 72 lp/mm, and imaging consistency is greater than 98%. Field test results show that the optical system can meet the requirements for shooting sequence images under transient condition. © 2024 Chinese Academy of Sciences. All rights reserved.
  Accession Number: 20241115748899
• Record 163 of
  
  Title:Feasible spindle speed interval identification method for large aeronautical component robotic milling system
  
  Author(s):Wang, Zhanxi(1); Zhang, Banghai(1); Gao, Wei(2); Qin, Xiansheng(1); Zhang, Yicha(3); Zheng, Chen(1)
  Source:Mechatronics
  Volume: 99  Issue:   DOI: 10.1016/j.mechatronics.2024.103143  Published: May 2024  
  Abstract:Robotic machining systems have been widely implemented in the assembly sites of large components of aircraft, such as wings, aircraft engine rooms, and wing boxes. Milling is the first step in aircraft assembly. It is considered one of the most significant processes because the quality of the subsequent drilling, broaching, and riveting steps depend strongly on the milling accuracy. However, the chatter phenomenon may occur during the milling process because of the low rigidity of the components of the robotic milling system (i.e., robots, shape-preserving holders, and rod parts). This may result in milling failure or even fracture of the robotic milling system. This paper presents a feasible spindle speed interval identification method for large aeronautical component milling systems to eliminate the chatter phenomenon. It is based on the chatter stability model and the analysis results of natural frequency and harmonic response. Firstly, the natural frequencies and harmonics of the main components of the robot milling system are analyzed, and the spindle speed that the milling system needs to avoid is obtained. Then, a flutter stability model considering the instantaneous cutting thickness is established, from which the critical cutting depth corresponding to the spindle speed can be obtained. Finally, the spindle speed interval of the robotic milling system could be optimized based on the results obtained from the chatter stability model and the analysis result of the natural frequency and harmonic response of the milling system. The effectiveness of the proposed spindle speed interval identification method is validated through time-domain simulation and experimental results of the large aeronautical component milling system. © 2024 Elsevier Ltd
  Accession Number: 20240715537558
• Record 164 of
  
  Title:Hyperspectral Image Reconstruction of SD-CASSI Based on Nonlocal Low-Rank Tensor Prior
  
  Author(s):Yin, Xiaorui(2); Su, Lijuan(2); Chen, Xin(1); Liu, Hejian(2); Yan, Qiangqiang(2,3); Yuan, Yan(2)
  Source:IEEE Transactions on Geoscience and Remote Sensing
  Volume: 62  Issue:   DOI: 10.1109/TGRS.2024.3398299  Published: 2024  
  Abstract:In single disperser coded aperture snapshot spectral imaging (SD-CASSI) systems, many methods have been developed to reconstruct hyperspectral images (HSIs) from compressed measurements. Among these, deep learning (DL)-based methods have stood out, relying on powerful DL networks. However, the solidified structure of DL-based methods limits their adaptability. Moreover, they are often based on a model that neglects the dispersion process and instead emphasizes the encoding-compression process. Furthermore, research on optimization-based methods designed especially for SD-CASSI is lacking. In this article, we propose a comprehensive two-step projection imaging model for SD-CASSI that includes both spectral shearing projection and encoding-compression projection. Based on this model, we derive a tensor-based optimization framework that incorporates with the nonlocal low-rank tensor (NLRT) prior. In particular, NLRT extracts inherent spatial structural information from the measurements and employs it to guide the clustering of spatial-spectral similar HSI blocks. A CANDECOMP/PARAFAC (CP) low-rank regularizer is introduced to constrain the low-rank property of HSI block clusters. After that, we develop a solution framework based on the alternating direction method of multiplier (ADMM) approach. Comprehensive experiments demonstrate that our NLRT method outperforms state-of-the-art methods in terms of flexibility and performance. The source code and data of this article are publicly available at https://github.com/sdnjyxr/NLRT. © 1980-2012 IEEE.
  Accession Number: 20242016095987
• Record 165 of
  
  Title:Influencing mechanisms of hot isostatic pressing on surface properties of additively manufactured AlSi10Mg alloy
  
  Author(s):Sun, Lijun(1,2); Yang, Yulei(3); Li, Siyuan(2); Chen, Wencong(2); Wang, Yichun(2); Yan, Peng(2); Zhu, Yueqi(2); Wu, Weichao(1); Hu, Bingliang(2)
  Source:Journal of Materials Processing Technology
  Volume: 329  Issue:   DOI: 10.1016/j.jmatprotec.2024.118426  Published: August 2024  
  Abstract:Additively manufactured AlSi10Mg alloys have received considerable attention due to the prospectives in light-weight structural applications. Hot isostatic pressing (HIP) is widely utilized to minimize internal pores and enhance mechanical properties in terms of fatigue strength and ductility. Whereas the influence and mechanisms of HIP on surface properties, which is of crucial importance for aerospace optical components, remain to be further clarified. In the present study, systematic surface and subsurface analysis were conducted to unveil the underlying mechanisms of HIP on the surface qualities of an additively manufactured AlSi10Mg alloy. Three-dimensional white-light interfering profilometer, high-resolution X-ray micro computed tomography, X-ray diffraction, scanning electron microscope and transmission electron microscope were exploited to characterize the surface and subsurface alterations induced by HIP. The results demonstrate that, although remarkable reduction in the amount and size of internal pores can be achieved, sharp increase in the surface defects and roughness occurred for the precisely machined surface of the HIP treated alloy. Surface and subsurface analysis reveal that the deterioration in surface properties results from the establishment of micron Si particles and the reduction in nanohardness induced by HIP treatment. © 2024 Elsevier B.V.
  Accession Number: 20241916054071
• Record 166 of
  
  Title:A Large Aperture Static Interference Hyperspectral Imaging Data Compression Method
  
  Author(s):Wang, Wei(1,2,3); Feng, Xiangpeng(1,3); Zhang, Geng(1,3); Liu, Xuebin(1,3); Li, Siyuan(1,3)
  Source:Guangzi Xuebao/Acta Photonica Sinica
  Volume: 53  Issue: 6  DOI: 10.3788/gzxb20245306.0610004  Published: June 2024  
  Abstract:After spectral reconstruction of large aperture static interferometry remote sensing data，a spectral image data cube can be generated that contains both spatial information about the ground objects and interference information. Considering the large volume of large aperture static interferometry remote sensing data and the scarce bandwidth of space-to-earth links，it is necessary to find suitable compression methods to compress this data. Starting from the mechanism of large aperture static interferometry imaging，based on the principles of large aperture static interferometry spectral imaging and the redundant information in the data，a compression algorithm called Spectral-Interference-Optical Path Difference Redundancy Removal（SIORR） is proposed. This algorithm fully considers the similarities between the interference curves of similar ground points and the redundancy between multiple frames. The SIORR algorithm can be divided into three parts. First，it analyzes and processes the interference curves in the hyperspectral data. In large aperture static interferometry spectral imaging remote sensing images，due to the continuity of spatial distribution of adjacent ground objects，the differences between interference curves of the same category are small. By constructing a table of typical interference curves to encode representations of different categories of interference curves，indexes of matching items and necessary correction information are recorded. Each table item not only represents a specific interference curve but also serves as a reference for compressing that type of curve. During the actual compression process，each interference curve in the original data is matched with an item in the curve table，and data compression and recovery are achieved by recording the index of the matching item and necessary correction information. Subsequently，during the interferometric imaging process，there is a high similarity between different optical path difference images，specifically reflected in the texture features of the remote sensing images. By using a prediction method to remove inter-frame correlations and utilizing the high correlation between different optical path difference images，while also avoiding the decrease in correlation caused by large differences in optical path difference，this algorithm adopts a grouping strategy. Every ten different optical path difference images are grouped together，and one is selected as the reference frame. Based on this reference frame，the other nine images are predicted. After these two processing steps，the correlation between different optical path difference images in large aperture static interferometry spectral imaging data has been reduced to about 0.5，while effectively reducing the quantization bit rate of pixel data points. After processing，the main information is stored in the image residuals and curve table suitable for compression，and the errors introduced by lossy compression are relatively small，thus the interference curves restored by the spectral curves are also closer to the original spectral curves. In lossy compression，spectral data is protected. Finally，the JPEG2000 image compression algorithm is used for lossless or lossy compression. Experimental results show that for large aperture static interferometry data，the proposed SIORR algorithm can achieve a 3.1× compression ratio in lossless compression. In lossy compression，the average peak signal-to-noise ratio is about 3 dB higher than that of other comparative algorithms. The spectral angle and relative quadratic error of the spectral curves of images restored by the SIORR algorithm are better than those processed by other comparison algorithms. The remote sensing images restored by the SIORR algorithm are also better than those of other comparison algorithms. Under lossless compression conditions，the SIORR algorithm can effectively increase the compression ratio. In lossy compression，compared to other algorithms，the SIORR algorithm has a higher image peak signal-to-noise ratio，and the interference curves and spectral curves are closer to the original curves，effectively protecting the spectral information. The SIORR algorithm not only has better compression effects but also has lower complexity and is easier to port，making it more suitable for compression processing of large aperture static interferometry remote sensing images. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20242716616440
• Record 167 of
  
  Title:Dynamic multi-focus laser sculpting of freeform 3D glass microstructures
  
  Author(s):Yao, Li(1); Xu, Kang(1); Huang, Lingyu(1); Huang, Peilin(1); Li, Zongyao(1); Wang, Pu(1,2,3); Xu, Shaolin(1)
  Source:Optics and Lasers in Engineering
  Volume: 180  Issue:   DOI: 10.1016/j.optlaseng.2024.108278  Published: September 2024  
  Abstract:The three-dimensional (3D) sculpturing of glass remains a significant challenge owing to its inherent hard and brittle nature. We develop a novel dynamic multi-focus laser sculpting (DMLS) method tailored for 3D glass fabrication. This method employs two-dimensional (2D) spatial multi-focus beams to form sectional profiles of 3D structures, which are modulated by superimposing the phase of Fresnel lenses and blazed gratings. With dynamic switching of phase diagrams on a spatial light modulator, the multi-focus beam rotates and creates a customized 3D laser-modified region inside the bulk glass. Following chemical etching helps remove the modified zones, forming ultimate 3D morphology on glass surface. The feasibility of this method hinges upon achieving uniform foci energy and narrow spatial foci intervals, essential for the precise removal of modified regions through connected crack channels during etching. We propose an extracting strategy to separate foci with random sequences into several groups to disrupt the periodicity of foci, thereby effectively weakening the unexpected Moiré fringes on the phase diagrams. This strategy enables the forming of dense foci by a single diagram with high uniformity, shortening the interval between foci. Further, for the lower surface roughness and higher precision of 3D structures, optimization of fabrication parameters is applied by experimental and numerical analysis. With the above optimization, the DMLS method is capable of carving diversified 3D glass structures, including hemispheres, cones, pyramids, semi-ellipsoids, and petal-like structures. Our method exhibits considerable versatility in processible structures with shape deviation lower than 1.9 μm, showing substantial potential in glass processing. © 2024 Elsevier Ltd
  Accession Number: 20242016089755
• Record 168 of
  
  Title:Efficient anti-frosting enabled by femtosecond laser-induced salt-philic and superhydrophobic surface
  
  Author(s):Deng, Qinwen(1); Wu, Tingni(1); Yin, Kai(1,2,3); Li, Xun(4); Wang, Lingxiao(1); Huang, Qiaoqiao(1); Huang, Yin(1); Arnusch, Christopher J.(5); Duan, Ji-An(2)
  Source:Applied Physics Letters
  Volume: 125  Issue: 12  DOI: 10.1063/5.0232717  Published: September 16, 2024  
  Abstract:Frost formation is a normal phase transition phenomenon in cold climates, while it usually brings certain troubles to human lives and production. Therefore, it is of great significance to develop frost resistant materials and key technologies. Here, a salt-philic and superhydrophobic surface is designed on a PDMS substrate by femtosecond laser direct writing technology in combination with salt-ethanol-water mixtures droplet treatment. The laser-treated PDMS embedded salt (LTP-S) surface exhibits superhydrophobicity, which alone is a property that can resist the formation of frost and enables a self-cleaning effect. Meanwhile, the salt coating further enhances the frost resistance of the surface by reducing the freezing point temperature. The LTP-S surface is revealed to perform well in frosting-defrosting cycles, washing resistance, chemical corrosion resistance, heating resistance, and long-term air exposure tests as a highly efficient and stable anti-frosting surface. This work demonstrates a facile strategy to fabricate a salt-philic and superhydrophobic surface for efficient anti-frosting. © 2024 Author(s).
  Accession Number: 20244117169329