2024

• Record 133 of
  
  Title:Optical System Design of High-Precision Line-Scanning Spectral Confocal Displacement Sensor
  
  Author(s):Yang, Wei-Guang(1,2); Zhang, Zhou-Feng(1); Qi, Mei-Jie(1); Yan, Jia-Yue(1,2); Cheng, Mo-Han(1,2)
  Source:Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis
  Volume: 44  Issue: 10  DOI: 10.3964/j.issn.1000-0593(2024)10-2900-09  Published: October 2024  
  Abstract:Spectral confocal displacement sensor is a new geometric precision measurement sensor with high accuracy, high efficiency, and non-contact technical advantages. It is now widely used in measuring micro or macro geometric quantities. Conventional geometric measurement sensors use contact mechanical probes, which cause damage to the surface of the object, making it difficult to meet the needs of non-destructive measurement in modern manufacturing. Unlike conventional optical systems that require correction for axial chromatic aberration, spectral confocal displacement sensors use axial chromatic aberration to establish the relationship between displacement and wavelength. However, most current research on spectral confocal displacement sensing technology has focused on point sweep. This technique can only obtain the geometric information of a single point, which greatly limits the efficiency in the practical application of precision measurement of larger areas and requires high back-end data processing and cumbersome data reconstruction. This study designs a line-swept spectral confocal displacement sensor system with submicron resolution to address this technical drawback. This study analyzes the principle of the line-swept spectral confocal displacement sensor and the detailed design of a large-range dispersive objective lens and a high spectral resolution spectral spectroscopic unit is carried out. By optimizing the optical path structure of the dispersive objective and spectral spectroscopy unit and balancing the aberrations, the RMS radius of each field of view of the full system is less than 5.5 μm, and good imaging quality is obtained. The results show that the full system has a resolution of 0.8 μm at a scan line length of 10 mm and an axial range of 3mm. This study has a broad application prospect in high-efficiency and high-precision geometric precision measurement. © 2024 Science Press. All rights reserved.
  Accession Number: 20244017150539
• Record 134 of
  
  Title:Surface degradation of epoxy resin exposed to corona discharge under bipolar square wave field: From phenomenon to the insights
  
  Author(s):Zhang, Chuang(1); Xiang, Jiao(2); Chen, Zhen(3); Wang, Zhuofei(4); Su, Yiling(1); Wang, Shihang(1); Li, Jianying(1); Li, Shengtao(1)
  Source:Polymer Degradation and Stability
  Volume: 228  Issue:   DOI: 10.1016/j.polymdegradstab.2024.110922  Published: October 2024  
  Abstract:The unavoidable corona discharge induced by distorted field is detrimental to the safety of power equipment, especially the equipment with high voltage magnitude and high frequency. In this paper, the degradation morphology, residual components, lifetime of endurance, partial discharge characteristics, and evolution of surface traps of epoxy insulation under bipolar square wave field is investigated. The results show that degraded zone exhibits as three layers with round pits and channel-like ravines on the surface of epoxy resin exposed to corona discharge. It is demonstrated that more oxygen element during corona discharge while more carbon element during breakdown appeared, and nano-Al2O3 fillers migrates to the discharged zone. The maximum temperature and number of emitted phonons increase with voltage amplitude and frequency in power law and exponential form, respectively, corresponding to the fitting function of endurance lifetime. The emitted light is concentrated on the near ultraviolet (UV) and infrared ray (IR) band, indicating the energy pooling and thermal effect of corona discharge, which interprets the distinct degradation behavior of samples under sinusoidal and bipolar square wave voltage. The effect of space charge and thermal conductivity should be considered simultaneously in the degradation of epoxy insulation under bipolar square wave field due to polarity reversal and high frequency, which is proved by the disparate behavior of EP/nano-Al2O3 composites resistance to corona discharge and the breakdown moment at falling edge of bipolar square wave voltage. This work may contribute to the advancement of resistance to corona discharge degradation in equipment with high power density, high voltage amplitude and high frequency. © 2024
  Accession Number: 20243016735840
• Record 135 of
  
  Title:Multi-object tracking by detecting small objects in satellite video
  
  Author(s):Cui, Haowen(1,2); Xu, Chujie(1,2); Zheng, Xiangtao(1); Lu, Xiaoqiang(1)
  Source:National Remote Sensing Bulletin
  Volume: 28  Issue: 7  DOI: 10.11834/jrs.20232098  Published: July 2024  
  Abstract:Multi-object tracking determines the position of an object and estimates the trajectory of objects in remote sensing satellite videos. This method has attracted considerable interest, and its application to security monitoring, motion analysis, and intelligent transportation has been explored. Compared with surveillance videos, remote sensing satellite videos contain smaller objects and a larger background, and thus the foreground object is difficult to detect. In addition, remote sensing satellite videos are extremely large, requiring massive computation and storage. Multi-object tracking in remote sensing satellite videos have high real-time requirements. Based on the mentioned problems, a multi-object tracking method for remote sensing satellite videos is proposed in this paper, which adopts tracking-by-detection paradigm. First, the backbone added a transformer that capture the global context information in the detection stage, enabling the detector to distinguish between objects and background. Then, an attention mechanism was used to enhance objects’features, enabling the proposed method to focus on the region of objects. Finally, an extra prediction branch was added to the network to generat a high-resolution feature map, which retained the details of small objects and was beneficial to small-object detection. Owing to the small objects and occlusion in remote sensing satellite videos, the confidence of hard positive samples was quite low. In the data association stage, an association strategy was adopted, which considered high and low confidence detection simultaneously and associated detected small objects with existing trajectories. To verify the effectiveness of the proposed method, ablation and comparison experiments were carried out on the remote sensing satellite videos dataset. The proposed method achieved 63.1% MOTA and 78.0% IDF1. The proposed method showed optimal performance, which reflected its suitability for multi-object tracking in remote sensing satellite videos. The proposed method ranked second in the multi-object tracking challenge of the 2021 Gaofen Challenge. The proposed method was dedicated to solving the difficulty of small-object tracking in remote sensing satellite videos, and some helpful methods for small-object tracking were used. Experimental results showed that the proposed method can improve the performance of multi-object tracking in remote sensing satellite videos. © 2024 Science Press. All rights reserved.
  Accession Number: 20243016739213
• Record 136 of
  
  Title:Modeling of compliant-based support for large aperture rotary prisms with horizontal-axis
  
  Author(s):Tao, L.V.(1,2); Wansha, W.E.N.(1,2); Ruan, Ping(1,2); Hao, And W.E.I.(1,2)
  Source:Optics Express
  Volume: 32  Issue: 15  DOI: 10.1364/OE.530553  Published: July 15, 2024  
  Abstract:In the Thirty-Meter-Telescope (TMT), a pair of wedge prisms with diameters of approximately 1500 mm are proposed to mitigate atmospheric dispersion across different zenith angles. This is achieved through controlled linear and rotary movements of the prisms. However, providing stable support for such large aperture prisms, with variable cross-sections and capable of rotating 360° around a horizontal optical axis, poses a significant challenge. This paper introduces a compliant-based support method tailored for TMT’s large aperture prisms. The methodology involves a mechanical analysis of the wedge prism with push-pull forces combination, followed by the development of the support principle based on degrees of freedom and constraints analysis. Subsequently, numerical modeling is conducted using compliant elements as the fundamental units. Furthermore, an integrated optomechanical analysis is performed to evaluate the performance of the support. The findings demonstrate that employing this support method results in superior optical surface accuracy under the coupled conditions of gravity and temperature, particularly for prisms with large apertures, variable cross-sections, and rotational capabilities. © 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
  Accession Number: 20242916730905
• Record 137 of
  
  Title:Hyperspectral Image Based Interpretable Feature Clustering Algorithm
  
  Author(s):Kang, Yaming(1); Ye, Peishun(1); Bai, Yuxiu(1); Qiu, Shi(2)
  Source:Computers, Materials and Continua
  Volume: 79  Issue: 2  DOI: 10.32604/cmc.2024.049360  Published: 2024  
  Abstract:Hyperspectral imagery encompasses spectral and spatial dimensions, reflecting the material properties of objects. Its application proves crucial in search and rescue, concealed target identification, and crop growth analysis. Clustering is an important method of hyperspectral analysis. The vast data volume of hyperspectral imagery, coupled with redundant information, poses significant challenges in swiftly and accurately extracting features for subsequent analysis. The current hyperspectral feature clustering methods, which are mostly studied from space or spectrum, do not have strong interpretability, resulting in poor comprehensibility of the algorithm. So, this research introduces a feature clustering algorithm for hyperspectral imagery from an interpretability perspective. It commences with a simulated perception process, proposing an interpretable band selection algorithm to reduce data dimensions. Following this, a multi-dimensional clustering algorithm, rooted in fuzzy and kernel clustering, is developed to highlight intra-class similarities and inter-class differences. An optimized P system is then introduced to enhance computational efficiency. This system coordinates all cells within a mapping space to compute optimal cluster centers, facilitating parallel computation. This approach diminishes sensitivity to initial cluster centers and augments global search capabilities, thus preventing entrapment in local minima and enhancing clustering performance. Experiments conducted on 300 datasets, comprising both real and simulated data. The results show that the average accuracy (ACC) of the proposed algorithm is 0.86 and the combination measure (CM) is 0.81. © 2024 Tech Science Press. All rights reserved.
  Accession Number: 20242116118449
• Record 138 of
  
  Title:Snapshot coherent diffraction imaging across ultra-broadband spectra
  
  Author(s):Li, Boyang(1); Xiao, Zehua(1); Yuan, Hao(1,2); Huang, Pei(1); Cao, Huabao(1,2); Wang, Hushan(1,2); Zhao, Wei(1); Fu, Yuxi(1,2)
  Source:Photonics Research
  Volume: 12  Issue: 9  DOI: 10.1364/PRJ.532957  Published: September 1, 2024  
  Abstract:Ultrafast imaging simultaneously pursuing high temporal and spatial resolution is a key technique to study the dynamics in the microscopic world. However, the broadband spectra of ultra-short pulses bring a major challenge to traditional coherent diffraction imaging (CDI), as they result in an indistinct diffraction pattern, thereby complicating image reconstruction. To address this, we introduce, to our knowledge, a new ultra-broadband coherent imaging method, and empirically demonstrate its efficacy in facilitating high-resolution and rapid image reconstruction of achromatic objects. The existing full bandwidth limitation for snapshot CDI is enhanced to ∼60% experimentally, restricted solely by our laser bandwidth. Simulations indicate the applicability of our method for CDI operations with a bandwidth as high as ∼140%, potentially supporting ultrafast imaging with temporal resolution into ∼50-attosecond scale. Even deployed with a comb-like harmonic spectrum encompassing multiple octaves, our method remains effective. Furthermore, we establish the capability of our approach in reconstructing a super-broadband spectrum for CDI applications with high fidelity. Given these advancements, we anticipate that our method will contribute significantly to attosecond imaging, thereby advancing cutting-edge applications in material science, quantum physics, and biological research. © 2024 Chinese Laser Press.
  Accession Number: 20243717016353
• Record 139 of
  
  Title:Classification of Benign–Malignant Thyroid Nodules Based on Hyperspectral Technology
  
  Author(s):Wang, Junjie(1,2,3); Du, Jian(1,3); Tao, Chenglong(1,3); Qi, Meijie(1,3); Yan, Jiayue(1,2,3); Hu, Bingliang(1,3); Zhang, Zhoufeng(1,3)
  Source:Sensors
  Volume: 24  Issue: 10  DOI: 10.3390/s24103197  Published: May 2024  
  Abstract:In recent years, the incidence of thyroid cancer has rapidly increased. To address the issue of the inefficient diagnosis of thyroid cancer during surgery, we propose a rapid method for the diagnosis of benign and malignant thyroid nodules based on hyperspectral technology. Firstly, using our self-developed thyroid nodule hyperspectral acquisition system, data for a large number of diverse thyroid nodule samples were obtained, providing a foundation for subsequent diagnosis. Secondly, to better meet clinical practical needs, we address the current situation of medical hyperspectral image classification research being mainly focused on pixel-based region segmentation, by proposing a method for nodule classification as benign or malignant based on thyroid nodule hyperspectral data blocks. Using 3D CNN and VGG16 networks as a basis, we designed a neural network algorithm (V3Dnet) for classification based on three-dimensional hyperspectral data blocks. In the case of a dataset with a block size of 50 × 50 × 196, the classification accuracy for benign and malignant samples reaches 84.63%. We also investigated the impact of data block size on the classification performance and constructed a classification model that includes thyroid nodule sample acquisition, hyperspectral data preprocessing, and an algorithm for thyroid nodule classification as benign and malignant based on hyperspectral data blocks. The proposed model for thyroid nodule classification is expected to be applied in thyroid surgery, thereby improving surgical accuracy and providing strong support for scientific research in related fields. © 2024 by the authors.
  Accession Number: 20242216182048
• Record 140 of
  
  Title:Efficient single-cycle mid-infrared femtosecond laser pulse generation by spectrally temporally cascaded optical parametric amplification with pump energy recycling
  
  Author(s):Yuan, Hao(1,2); Huang, Pei(1); Feng, Tongyu(1,2); Ma, Yahui(1,2); Wang, Xianglin(1); Cao, Huabao(1,2); Wang, Yishan(1,2); Zhao, Wei(1,2); Fu, Yuxi(1,2)
  Source:Optics Letters
  Volume: 49  Issue: 9  DOI: 10.1364/OL.519729  Published: May 1, 2024  
  Abstract:We proposed spectrally temporally cascaded optical parametric amplification (STOPA) using pump energy recycling to simultaneously increase spectral bandwidth and conversion efficiency in optical parametric amplification (OPA). Using BiB3O6 and KTiOAsO4 nonlinear crystals, near-single-cycle mid-infrared (MIR) pulses with maximum energy conversion efficiencies exceeding 25% were obtained in simulations. We successfully demonstrated sub-two-cycle, CEP-stable pulse generation at 1.8 µm using a four-step STOPA system in the experiment. This method provides a solution to solve the limitations of the gain bandwidth of nonlinear crystals and the low conversion efficiency in broadband OPA systems, which is helpful for intense attosecond pulse generation and strong laser field physics studies. © 2024 Optica Publishing Group.
  Accession Number: 20241916073860
• Record 141 of
  
  Title:Effect of atmospheric environment on the stability of secondary electron emission from magnesium oxide and alumina surfaces
  
  Author(s):Lian, Zhuoxi(1); Zhu, Xiangping(2,3); Wang, Dan(1); Meng, Xiangchen(1); He, Yongning(1)
  Source:Journal of Physics D: Applied Physics
  Volume: 57  Issue: 12  DOI: 10.1088/1361-6463/ad15c0  Published: March 22, 2024  
  Abstract:MgO and Al2O3 are two typical ceramics with high secondary electron yield (SEY) and are widely applied in electron multiplier devices as dynode coating. However, dynodes in multipliers are inevitably exposed to various environments, degenerating their SEY performance. To specify the influence of the atmospheric environment on SEY for MgO and Al2O3 ceramics, we conducted environmental stability experiments on MgO and Al2O3 nanofilms. By exposing the nanofilms fabricated by atomic layer deposition to air for certain durations, it was found that although the MgO film possessed high SEY, its SEY decreased significantly as the storage duration increased, specifically, its SEY peak value (δ m) decreased from 5.97 to 3.35 after 180 d. Whereas the SEY of the Al2O3 film changed very little with the storage duration extending, its δ m decreased from 4.01 to 3.70 after 180 d, indicating the Al2O3 film had good SEY environmental stability. To reveal the mechanism of SEY degradation, the modification analysis of surface composition was implemented. It was found that the surface of MgO film underwent degradation besides unavoidable contamination, generating Mg(OH)2 and MgCO3. Whereas, there is no chemical reaction occurred on the Al2O3 surface. Combining the advantages of high SEY of MgO and good environmental stability of Al2O3, several Al2O3/MgO double-layer nanofilms were prepared. The δ m value of 20 nm MgO nanofilms covered by 1 nm Al2O3, decreased from 4.90 to 4.56, with a reduction of only 6.94% after 180 d. The results showed that the Al2O3 film achieved effective protection of the MgO film. The SEY environmental stability of the double-layer structure was significantly improved, and the effect of thickness on SEY was theoretically interpreted. This work makes significant sense for understanding the influence of the environment on the SEY for MgO and Al2O3, which has potential applications in electron multipliers. © 2023 IOP Publishing Ltd.
  Accession Number: 20240115304780
• Record 142 of
  
  Title:Depth-of-field extended Fourier ptychographic microscopy without defocus distance priori
  
  Author(s):Chen, Yanqi(1,2); Xu, Jinghao(1,2); Pan, An(1,2)
  Source:Optics Letters
  Volume: 49  Issue: 11  DOI: 10.1364/OL.524267  Published: June 1, 2024  
  Abstract:Fourier ptychographic microscopy (FPM) provides a solution of high-throughput phase imaging. Thanks to its coherent imaging model, FPM has the capacity of depth-of-field (DOF) extension by simultaneously recovering the sample’s transmittance function and pupil aberration, which contains a defocus term. However, existing phase retrieval algorithms (PRs) often struggle in the presence of a significant defocus. In this Letter, different PRs with embedded pupil recovery are compared, and the one based on the alternating direction multiplier method (ADMM-FPM) demonstrates promising potential for reconstructing highly defocused FPM images. Besides, we present a plug-and-play framework that integrates ADMM-FPM and total variation or Hessian denoiser for pupil function enhancement. Both simulations and experiments demonstrate that this framework enables robust reconstruction of defocused FPM images without any prior knowledge of defocus distance or sample characteristics. In experiments involving USAF 1951 targets and pathologic slides, ADMM-FPM combined with the Hessian denoiser successfully corrected the defocus up to approximately 200 µm, i.e., extending the DOF to 400 µm. © 2024 Optica Publishing Group.
  Accession Number: 20242416231469
• Record 143 of
  
  Title:Bit Error Rate Performance Study of UWOC System Based on Multiple Degenerate Composite Channels
  
  Author(s):Zhang, Jianlei(1); Zhang, Pengwei(1); Zhu, Yunzhou(2); Tian, Yuxin(1); Li, Jieyu(1); Yang, Yi(1); He, Fengtao(1)
  Source:Guangzi Xuebao/Acta Photonica Sinica
  Volume: 53  Issue: 3  DOI: 10.3788/gzxb20245303.0301002  Published: March 2024  
  Abstract:Underwater Wireless Optical Communication (UWOC) capitalizes on the blue-green segment of the light spectrum which is subject to minimal attenuation in marine environments, thereby rendering it optimal for the conveyance of information. The advantages of UWOC are manifold, it boasts of swift data transmission, negligible latency, and fortified confidentiality. However, UWOC grapples with significant barriers which encompass the limitation of transmission range and the deleterious effects attributable to the intrinsic properties of seawater, as well as marine turbulence-factors like absorption, scattering, bubbles and turbulence that collectively compromise communicative efficiency. To systematically confront these impediments and to gauge the comprehensive influence of the aforementioned factors on UWOC system efficacy, this inquiry has formulated an integrative underwater wireless optical channel model. This archetype not only encapsulates solitary influences but also their concomitant interactions and aggregate impact on signal transmission. By harnessing the Mie scattering theorem, the research meticulously delineates the volume scattering function, the scattering coefficient, and the phase function of microbubble assemblages in seawater—pivotal determinants essential for the assessment of scattering phenomena on the propagation of optical signals. Addressing turbulence, an elaborate channel model featuring a mixed exponential generalized Gamma distribution is employed, defining the statistical behavior of turbulence to faithfully represent the stochastic and unpredictable nature of the channel. This study extends its analysis to include the repercussion of signal attenuation and acoustic noise as a consequence of turbulence, effectively projecting these perturbations onto the optical signals disseminated through the composite channel. Importantly, it elucidates a closed-form expression for the Bit Error Ratio (BER) within the composite channel, employing On-Off Keying (OOK) modulation, thus establishing a theoretical groundwork for the analysis of UWOC system performance. The research delves into the impact of critical determinants such as turbulence strength, bubble density, transmission range, and marine water quality on the BER metrics of UWOC systems. It is discerned that heightened turbulence intensity incrementally necessitates a greater minimum Signal to Noise Ratio (SNR) at the receiver end to maintain a predetermined average BER. Consistent with this SNR, an augmentation in turbulence intensity conspicuously degrades system throughput, inducing a systematic deterioration in BER performance. Within a transparent seawater milieu at a transmission span of 20 m, with a bubble concentration of 3 × 106 per cubic volume, the system′s mean BER is recorded at 4.57 × 10-4. As the bubble density escalates to 9 × 106 and subsequently to 9 × 107 per cubic volume, the average BER correspondingly declines to 5.76 × 10-4 and 1.19 × 10-2. In scenarios of turbulence characterized by a scintillation index of 1.932 8, the system is adept at sustaining low BER transmissions. Ensuring dependable communication quality with an average BER falling below 10-3 across an array of aquatic environments—be it crystalline seawater, littoral waters, or murky harbor waters—the utmost permissible transmission distances with bubble presence(at a density of 1 × 107 per cubic volume)are confined to 22.5 m, 10.4 m, and 2.3 m respectively. Absent bubble interference, these distances are extendable to 28.0 m, 13.5 m, and 2.7 m. Given the pronounced absorption and scattering induced by elevated turbidity and suspended particulates, securing long-range communication in silt-laden harbor waters presents a significant hurdle. Additionally, the study substantiates that elevating the link distance precipitates an almost linear augmentation in BER, indicative of a noteworthy degeneration in signal integrity. The outcomes not only underscore the exigency of crafting and fine-tuning UWOC systems attuned to the vicissitudes of the oceanic realm but also accentuate the latent efficacy of modulation methodologies and channel coding strategies as instrumental in amplifying system competence. © 2024 Chinese Optical Society. All rights reserved.
  Accession Number: 20241215775065
• Record 144 of
  
  Title:Artificial potential field-empowered dynamic holographic optical tweezers for particle-array assembly and transformation
  
  Author(s):Li, Xing(1,2); Yang, Yanlong(1); Yan, Shaohui(1); Gao, Wenyu(1,2); Zhou, Yuan(1,2); Yu, Xianghua(1); Bai, Chen(1); Dan, Dan(1); Xu, Xiaohao(1); Yao, Baoli(1,2)
  Source:PhotoniX
  Volume: 5  Issue: 1  DOI: 10.1186/s43074-024-00144-5  Published: December 2024  
  Abstract:Owing to the ability to parallel manipulate micro-objects, dynamic holographic optical tweezers (HOTs) are widely used for assembly and patterning of particles or cells. However, for simultaneous control of large-scale targets, potential collisions could lead to defects in the formed patterns. Herein we introduce the artificial potential field (APF) to develop dynamic HOTs that enable collision-avoidance micro-manipulation. By eliminating collision risks among particles, this method can maximize the degree of parallelism in multi-particle transport, and it permits the implementation of the Hungarian algorithm for matching the particles with their target sites in a minimal pathway. In proof-of-concept experiments, we employ APF-empowered dynamic HOTs to achieve direct assembly of a defect-free 8 × 8 array of microbeads, which starts from random initial positions. We further demonstrate successive flexible transformations of a 7 × 7 microbead array, by regulating its tilt angle and inter-particle spacing distances with a minimalist path. We anticipate that the proposed method will become a versatile tool to open up new possibilities for parallel optical micromanipulation tasks in a variety of fields. © The Author(s) 2024.
  Accession Number: 20244217226084