最新刊期
卷 32 ， 期 3 ， 2024
- 摘要：This study presents a method for correcting light intensity in light⁃induced thermoelastic spectroscopy (LITES) using a nonlinear light intensity response, enabling precise light intensity corrections. The DFB laser, set to a wavelength modulation mode at a frequency of 16369.75 Hz, benefits from enhanced nonlinear light intensity due to a fiber amplifier. The laser beam traverses a multi⁃pass cell before focusing on the quartz tuning fork (QTF) base, generating a thermoelastic signal. A lock⁃in amplifier demodulates the harmonic signal, and polynomial fitting of the harmonic signal's baseline extracts harmonics related to both concentration and light intensity. Experimental data reveal a strong linear correlation (coefficient > 0.998) between the baseline amplitude of the harmonic signal and light intensity as it varies from 22.03 mW to 3.16 mW, with normalized harmonic signal amplitude variation under 0.37%. In methane detection, the system demonstrates a robust linear response across a broad concentration range, with harmonic signal noise ratios indicating a detection threshold as low as 0.22×10-6. This research offers a novel approach for LITES light intensity correction, significantly enhancing system stability for prolonged measurements.关键词：light-induced thermoelastic spectroscopy;harmonic signal;Nonlinear response;polynomial fitting;light intensity correction
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发布时间：2024-02-22 - 摘要：The rapid advancement of fluorescence microscopy technology has increased the need for better excitation light sources, particularly for multi⁃wavelength lasers coupled in single mode fiber. This article explores the technology of coupling multi⁃wavelength lasers into single mode fibers within the spectral range of 400-680 nm. To enhance the coupling efficiency of different wavelengths, a triplet lens is designed to effectively reduce chromatic aberration. Moreover, a fiber coupling component structure and a quick and easy coupling adjustment method was developed to address the challenges of fiber coupling alignment. Fiber coupling experiments involving four commonly used laser wavelengths in fluorescence microscopy (405, 488, 561, 638 nm) have demonstrated a coupling efficiency of over 65% for all four wavelengths. These results validate the effectiveness of the multi⁃wavelength lasers coupler designed in this study. Furthermore, due to its simple adjustment and low cost, the coupler holds significant commercial value and establishes a solid foundation for the localization of multi⁃wavelength lasers coupled in single mode fiber.关键词：fluorescence microscopy;single mode laser coupling;muti-wavelength lasers;fiber Coupling
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发布时间：2024-02-22 - 摘要：Full-aperture continuous polishing is crucial for refining large flat optical elements， with the main challenge being the deterministic control of the elements' surface figure. This study delves into the factors and control strategies affecting the surface figure to enhance the process's deterministic control. It emphasizes the role of kinematic parameters， the polishing lap's surface shape， and its passivation state. A kinematic model， based on effective sliding distance， was developed to highlight the impact of the lap's groove design on the surface figure. A novel approach for measuring the lap's surface shape involves using a displacement sensor for scanning， followed by shape reconstruction through an interpolation algorithm. The paper introduces an in-situ method for precise correction of the lap's shape error using a subaperture technique with small tools. In addition， it proposes a monitoring method for the lap's surface passivation state and explores its effect on the surface figure. Findings indicate that annular grooves tend to produce annular textures， whereas square and spiral grooves yield smoother surfaces. Through in-situ measurement and correction of the lap's shape error， significant enhancements in surface figure can be achieved. The surface deteriorates as the lap becomes more passivated. An 800 mm×400 mm×100 mm flat element polished with this method achieved a surface figure better than λ/6. This research sheds light on the factors influencing surface figure in full-aperture continuous polishing and introduces a quantitative control approach， significantly enhancing the process's control precision.关键词：optical fabrication;full-aperture continuous polishing;surface figure;influencing principle;control method
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发布时间：2024-02-22 - 摘要：To achieve real⁃time, multi⁃degree⁃of⁃freedom measurement and feedback on the position and orientation of a robot's end⁃effector, a planar 3⁃DOF non⁃contact measurement system utilizing sensor fusion of a Position Sensitive Detector (PSD) was developed. The system's design involved studying the measurement principle, signal processing circuitry, ambient light interference mitigation, and a nonlinear calibration algorithm. Initially, a 4⁃PSD measurement system was tailored to the PSD sensor's measurement capabilities and the specific needs of planar 3⁃DOF measurement, establishing a mathematical model for the system. The PSD sensor's signal processing was then explored, achieving single PSD signal processing through an operational amplifier and divider, integrated with an MCU and A/D conversion chip for high⁃frequency signal acquisition on a PC. Preliminary tests of the 4⁃PSD system addressed ambient light interference using laser modulation and digital filtering techniques. Calibration of the 4⁃PSD system⁃comprising origin, angle, length, and second⁃order nonlinear calibration-was conducted using a laser displacement sensor, detailing the calibration steps and post⁃calibration error distribution. The designed system boasts a high measurement frequency of 50 Hz, with calibration experiments indicating an average accuracy of 0.49 mm within a 70 mm×70 mm range, achieving a 90% error reduction post⁃calibration. This system fulfills the majority of requirements for high⁃speed, high⁃precision, non⁃contact real⁃time measurement and feedback of robot end⁃effectors.关键词：Position Sensitive Detector（PSD） sensor;Position and orientation measurement;real-time feedback;Measurement and calibration
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发布时间：2024-02-22 - 摘要：In laser heterodyne interferometry, displacement measurement errors arise from the rotation of the measuring mirror alongside the measured object. To address this, the paper introduces a compensation technique using a Kalman filter for laser heterodyne interferometric displacement measurements. By analyzing the correlation between the measuring mirror's rotational angle and the measuring beam spot's position shift, a position sensitive detector (PSD) is employed to gauge the rotational angle. Enhancing angle measurement precision, the Kalman filter method is utilized to diminish the noise in the PSD's position voltage signal, thereby accurately determining the spot's position shift. Subsequently, displacement is compensated based on the measured rotational angle, utilizing a decoupling mathematical model that separates rotational angle from displacement. To assess the proposed filtering algorithm and displacement measurement compensation method's viability and efficiency, an experimental laser heterodyne interferometric setup was established. Experiments conducted included spot position stability measurement, rotational angle measurement verification, and laser heterodyne interferometric displacement measurement and compensation. Results demonstrate a reduction in the standard deviation of spot position drifts from 0.52 μm to 0.18 μm post-Kalman filter denoising. Moreover, the discrepancy between measured angles and the Thorlabs 6-DOF motion stage's rotational angles remain within ±1.38×10-4°. Displacement and rotational angle of the M-531.DD linear stage over a 200 mm range are measured. Following compensation with the measured angle, the standard deviation between the displacement measurement results and the M-531.DD linear stage's positionings decreases from 1.55 μm to 0.29 μm.关键词：laser heterodyne interferometry;displacement measurement;error compensation;kalman filtering
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发布时间：2024-02-22
Modern Applied Optics
- 摘要：Creating microstructures on sapphire surfaces is key to altering their wettability. The laser-induced plasma etching method offers distinct benefits for crafting these microstructures. This study examines how laser fluence， the distance between the target and sapphire， and scanning speed impact the microgrooves' morphology and geometry on sapphire surfaces using the laser-induced plasma-assisted ablation （LIPAA） technique， employing a controlled variable approach. Further， it explores how LIPAA's processing parameters affect the sapphire's surface contact angle through orthogonal testing. Results indicate that laser scan line spacing most significantly influences the surface contact angle， followed by the target-to-sapphire distance and laser fluence， with scanning speed having the minimal impact. At a laser fluence of 6.3 J/cm²， scan line spacing of 200 μm， target-to-sapphire distance of 150 μm， and scanning speed of 10 mm/s， the sapphire's surface contact angle reached 136°， demonstrating superior hydrophobicity. Conversely， with a laser fluence of 7.4 J/cm²， scan line spacing of 50 μm， target-to-sapphire distance of 100 μm， and scanning speed of 5 mm/s， the surface contact angle was 29°， indicating strong hydrophilicity， which remained stable over time. SEM observations revealed numerous nanoparticles on the sapphire microstructures， which together influence the sapphire's wettability.关键词：laser-induced plasma-assisted ablation;sapphire;Microstructures;processing parameter;surface wettability
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发布时间：2024-02-22 - 摘要：To address the issue of underactuation caused by passive buffers in a tether-driven microgravity simulation system， an active buffer control method based on Pneumatic Artificial Muscles （PAM） was proposed. Firstly， the tether-driven microgravity simulation system was analyzed for ground-based micro/low-gravity simulation. A block-structured nonlinear neural network modeling method to effectively overcome the highly nonlinear nature of PAM was introduced. Subsequently， the disturbances caused by the flexible interaction between the tether and the spacecraft was analyzed. Finally， a nonlinear model predictive tracking control approach was employed. Compared to traditional PID control methods， the proposed was introduced approach offers advantages such as simple parameter adjustment， excellent real-time tracking performance， and robust control performance in the presence of perturbations to the target inertia parameters of the unloading system. Experimental results demonstrate that the proposed method ensures tracking force error within 3% under various disturbances. The feasibility of the active buffer based on PAMs is confirmed experimentally， and the proposed control method achieves force-tracking control in the presence of flexural uncertainty.关键词：suspended gravity offloading system;pneumatic artificial muscle;active buffer;nonlinear model predictive tracking control
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发布时间：2024-02-22 - 摘要：To achieve the thinning and polishing of small-size copper-plated InP wafers using 8-inch chemical mechanical polishing （CMP） equipment， it's essential to enhance equipment compatibility， streamline process steps， and mitigate issues like cracks and surface particles on InP wafers due to excessive handling. Initially， employing custom-made molds allows the processing of small-size InP wafers on 8-inch CMP equipment. Subsequently， to address the brittleness of InP wafers， adjusting the equipment's polishing head pressure， speed， and polishing pad speed， among other process parameters， is crucial to satisfy the demands of the subsequent bonding process. Experimental validation shows that with the use of special molds and the polishing head pressure set to 20.684 kP， along with polishing head and pad speeds of 93 r/min and 87 r/min， respectively， the InP wafer's surface roughness achieves Ra≤1 nm， and the copper layer's removal rate is 3 857×10-10/min. This preparation ensures defect-free bonding with 8-inch wafers， eliminating voids at the bonding interface. The CMP process for 2-inch InP wafers on 8-inch equipment significantly lowers CMP costs， prevents the increase in surface particle size and scratches during wafer transfer， and facilitates hybrid bonding and Cu interconnections between InP and Si wafers.关键词：chemical mechanical polishing;InP;removal rate;bonding;surface roughness
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发布时间：2024-02-22 - 摘要：The evolution of objectives and the broadening of tasks have heightened the need for swift maneuverability in the photoelectric tracking and pointing system. Shifting from ground⁃based to diverse mobile platforms such as vehicles, ships, aircraft, and spacecraft marks a significant trend in the development of photoelectric tracking and pointing systems. The stabilization of the line of sight using an inertial reference unit (IRU) is essential to counteract the high⁃frequency disturbances encountered on these mobile platforms, enabling the system to achieve tracking accuracy at the micro⁃radian or even sub⁃micro⁃radian level. This paper delves into various IRU implementation strategies to mitigate disturbances from the carriers, ensuring precise aiming of the photoelectric tracking and pointing system on moving platforms. It highlights a system design that employs low noise and wideband inertial sensors for angle disturbance detection and achieves line of sight stabilization via feedback control. The document details the system's operational modes, functional features, constructs its mathematical model, and reviews both domestic and international research advancements and future directions in IRU technology. It emphasizes that inertial sensing, support structures, and control systems are critical to IRU's stabilization performance, and it organizes the latest research trends in these three vital areas. Conclusively, the paper outlines the spaceborne applications of IRU and explores potential future application domains, considering current demands.关键词：inertial reference unit;moving platform;photoelectric tracking and targeting system;line-of-sight stabilization;disturbance suppression
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发布时间：2024-02-22
Micro/Nano Technology and Fine Mechanics
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Three-dimensional mapping of park based on synchronous fusion of lidar and inertial measurement unit AI导读
摘要：To address the issues of inaccurate mapping and position drift in 3D autonomous driving maps， LIDAR odometry was utilized to counteract cumulative errors of the inertial measurement unit（IMU）， and corrections for LIDAR point cloud distortions were made through IMU pre-integration. This approach enabled the creation of a mapping system where LIDAR and IMU were tightly integrated. Subsequently， the back-end map was enhanced by the incorporation of loopback detection， LIDAR odometry， and IMU pre-integration factors， aiming to bolster the global consistency of the positioning map and minimize cumulative drift errors. The optimization of the back-end map sought to enhance global localization consistency， reduce positioning errors， and curtail cumulative drift. Experimental validation was conducted in a school campus environment and with the use of the KITTI open-source dataset. The results demonstrate that in the school campus scenario， an 11.04% reduction in average APE error and a 17.35% decrease in RMSE are achieved by the refined algorithm compared to the baseline algorithm. For the KITTI dataset scenario， a reduction of 10.04% in both average APE error and RMSE， and a 12.04% decrease in mean square error are observed， underscoring the efficacy of the enhanced mapping technique in elevating position estimation and map construction precision.关键词：lidar;automatic driving;synchronous positioning and mapping;sensor fusion- 53
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发布时间：2024-02-22 - 摘要：In visible and thermal infrared tracking（RGB-T）， to effectively merge these two modalities building on traditional tracking techniques， this study introduces an attention-based RGB-T tracking approach based on the attention mechanism. This method employs the attention mechanism to augment and integrate features from both visible and infrared images. It features a self-feature enhancement encoder to boost single modality features， and a cross-feature interaction decoder for merging the enhanced features from both modalities. Both the encoder and decoder incorporate dual layers of attention modules. To streamline the network， the traditional attention module is simplified by substituting fully connected layers with 1×1 convolutions. Moreover， it merges features from various convolutional layers to thoroughly explore details and semantic insights. Comparative experiments on three datasets—GTOT， RGBT234， and LasHeR—demonstrate that our method achieves superior tracking performance， underscoring the efficacy of the attention mechanism in RGB-T tracking.关键词：RGB-T tracking;attention mechanism;feature fuse of multi-modality;feature enhancement
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发布时间：2024-02-22 - 摘要：To address the challenges of large-scale and complex network structures in deep learning-based stereo matching， this work introduces a compact yet highly accurate network. The feature extraction module simplifies by removing complex， redundant residual layers and incorporating an Atrous Spatial Pyramid Pooling （ASPP） module to broaden the field of view and enhance contextual information extraction. For cost calculation， three-dimensional （3D） convolutional layers refine stereo matching accuracy through cost aggregation. In addition， a bilateral grid module is integrated into the cost aggregation process， achieving precise disparity maps with reduced resolution demands. Tested on widely-used datasets like KITTI 2015 and Scene Flow， our network demonstrates a significant reduction in parameters by approximately 38% compared to leading networks like Pyramid Stereo Matching Network （PSM-Net）， without compromising on experimental accuracy. Notably， it achieves an end-point error （EPE） of 0.86 on the Scene Flow dataset， outperforming many top-performing networks. Thus， our network effectively balances speed and accuracy in stereo matching.关键词：computer vision;stereo matching;artificial neural network;parallax
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发布时间：2024-02-22 - 摘要：Light field cameras, capable of capturing both the intensity and direction of light, are utilized in applications like foreground occlusion removal and depth estimation. However, the limited size of imaging sensors restricts the simultaneous achievement of high spatial and angular resolution in light field images. This paper introduces a method combining Fourier convolution and channel attention for light field angular reconstruction, which indirectly creates dense light field images from sparse ones using reference views from the image's four corners. This method leverages the light field image's inherent 4D structure, employing channel⁃level dense fast Fourier residual convolution blocks to model the spatial and angular correlations in both spatial and frequency domains. Channel attention blocks, utilizing global response normalization, then adaptively fuse these channels. Furthermore, an enhanced viewpoint⁃weighted indirect synthesis approach is proposed, assigning a confidence map to each reference view to improve the synthesis of new, realistic views by establishing relationships between reference views. Experimental results demonstrate that our method outperforms the advanced light field angular reconstruction technique IRVAE, showing an average PSNR improvement of 0.08, 0.13, and 0.13 dB on the natural light field dataset 30Scenes, Occlusion, and Reflective, respectively, ensuring clear reconstruction results with angular consistency in the light field.关键词：light field angular reconstruction;fourier convolution;global response normalization;viewpoint weighting indirect view synthesis
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发布时间：2024-02-22
Information Sciences
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