最新刊期
期 23 ， 2023
- 摘要：To obtain high-purity cylindrical vector beam pulses， a wavelength-switchable passive mode-locked cylindrical vector beams all-fiber laser is proposed and constructed based on a symmetrical two-mode coupler. First， the refractive index matching diameter for the conversion from the fundamental mode to the higher-order mode was obtained based on the principles of fiber optic transmission. The influence exerted by the structural parameters of the symmetrical two-mode coupler on mode selection and coupling characteristics was analyzed， employing simulations of mode coupling theory and the beam propagation method. The symmetrical double-mode coupler was fabricated utilizing the fusion tapering method. This method eliminates the complicated pre-taper process commonly employed in traditional mode selection coupler production. Finally， a passive mode-locked all-fiber laser， based on the symmetrical two-mode coupler， was constructed. This laser showcases a switchable central wavelength of 1 039 nm and 1 068 nm， pulse repetition interval of 113.8 ns， repetition rate of 8.78 MHz， pulse durations of 660 ps/656 ps， and maximum output average power of 5.25 mW/5.2 mW. In addition， it achieves a mode purity of over 97% for the vector beam output. The conducted experiments validate the feasibility of the symmetrical two-mode coupler and present a viable solution for obtaining high-purity cylindrical vector beams in future applications.关键词：fiber laser;symmetric two-mode coupler;Nonlinear Polarization Rotation Principle mode-locked;cylindrical vector beams;high mode purity
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发布时间：2023-12-13 - 摘要：To address the problems of low measurement accuracy and significant human interference in lens position adjustment in existing center deviation measurement methods， this paper proposes an automatic measurement method for the center deviation of differential confocal lenses. This method uses differential confocal focusing technology to precisely locate the cat's eye and confocal points of the measured lens， based on the fact that the zero point of the differential confocal axial light intensity response curve corresponds precisely to the characteristic point of the measured lens. The high-precision air-bearing rotating shaft drives the rotation of the measured mirror， while the displacement sensor records the position information of the measured mirror. In combination with the five-dimensional posture automatic adjustment mechanism， the high-precision correction of the attitude deviation of the measured mirror was realized， the eccentricity error was eliminated， and the measurement accuracy was improved. Finally， a laser differential confocal lens center deviation measurement system was established， which automatically measured the lens center deviation with high precision. The experimental results show that the measurement accuracy of the lens eccentricity can reach 0.41%， while the measurement repeatability is greater than 100 nm. Compared with the existing manual single measurement method， the proposed method has good repeatability， small random error， and high measurement accuracy. It serves as a new technical approach for the automatic measurement of lens eccentricity with high precision.关键词：laser measurement;Differential confocal;centrality deviation;automatic adjustment;automatic measurement;position deviation
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发布时间：2023-12-13 - 摘要：To expand the application of fiber Bragg grating sensors in the field of robotic intelligent sensing， we have designed a novel FBG forearm sensing sheath. In this workstudy， a wavelength -electric conversion control system and the an algorithm forof human-computer bionic tracing were developed. There were three FBG sensing units including tension rings in the forearm sensing sheath. The tension rings made of spandex polyurethane fibers exerted a pre-tightening force on FBGs， which could effectively avoid the traction direction deviation caused by clothing or skin gathering. The joint movements caused the spandex polyurethane fibers to drive the FBGs stretch or axial contractionng axially and the wavelengths shift of FBGs' wavelengths shift. Thereafter， the wavelength-electric conversion control system transfered the motion posture features of human elbow bending angle α， wrist pitching angle β， and knuckle joint motion angle γ to the robot arm's direction θ， height φ， and mechanical claw opening and closing angle ψ， respectively. By deducing the relationship between the range of the human joint movement's range and the output range of the robot arm， the detection coefficient and the control coefficient were obtained. Then， the wavelength-electric conversion coefficient was deduced by converting the dynamic wavelength to the control electric signal in real-time. The experimental results demonstrate that this wavelength -electric conversion control system can make the robotic arm trace the human elbow bending， wrist pitching， and finger joint motion with good linear responses. Within the experimental range， the maximum cumulative error of wavelength-electric conversion coefficient of direction， height， and open/close control output are 0.771 11%，1.992 91%， and 0.341 17%， and the deviation of three control angle outputs are 1.135 60°， 1.720 56°， and 1.826 57°， respectively. The wavelength -electric conversion control system has good control accuracy and it can make the robotic arm track human forearm movements . The research results can provide a theoretical basis to further develop the FBG sensing system of bionic tracing for the robotic arm.关键词：optical fiber Bragg grating;bionic tracing;wave-electric conversion;posture feature
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发布时间：2023-12-13 - 摘要：With the development of quantum secure communication networks and industrialization， there is an urgent need for lightweight and miniaturized receiving telescopes for scalable and portable multiple application scenario requirements of quantum tracking instruments. A detailed comparative analysis was performed on the technical systems that meet the requirements of receiving telescopes， the optical system form of the RC+micropixel+quantum module was determined， and the technical system of a small F#+micro pixel was adopted. An all-aluminum Φ280 quantum tracker receiving telescope was designed. The optical design results of RC telescope of F5 were obtained. Using RSA-6061 microcrystalline aluminum alloy as the structural material for the telescope mirror， coupled with an integrated hard aluminum alloy of high-rigidity structure， the static （gravity and temperature deformation） simulation analysis results met the requirements of near-diffraction limit imaging and high-efficiency quantum reception. The dynamic simulation analysis results demonstrated that the first mode was 91 Hz， which had a sufficiently high dynamic stiffness and safety redundancy. The integration test results show that： The wave aberration RMS of the central field of view of the telescope is λ/14.7， and the wavefront aberration of the five field of view systems is better than λ/12.7， which ensured high-quality beacon imaging near the diffraction limit. The measured optical transfer function at Nyquist frequency is 0.15； The average polarization contrast of the four polarization states （HV+-） of the telescope is 454， along with an overall system efficiency of 51.93%， which allows high-quality quantum key reception； The experimental results of external stellar imaging at 25 and +30 ℃ verified the stability of the system， which can be used for high-quality centroid extraction for off-target closed loop； The QKD experiment with Mozi obtains 92.9 kb codes， and the total bit error rate is 1. 18%， allowing high-efficiency quantum reception.关键词：Quantum communication;lightweight and miniaturized;Quantum tracker;high rigidity;quantum key distribution
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发布时间：2023-12-13
Modern Applied Optics
- 摘要：To reduce the residual attitude error of the drag-free satellite， a pointing stability control mechanism based on momentum exchange was designed. To realize nanoradian-level pointing stability accuracy for the satellite， a composite axis control method was implemented. This method work in conjunction with the drag-free attitude control loop， simultaneously reducing the consumption of working fluid in other actuators. This approach was designed to extend the satellite's operational lifespan. Firstly， the design incorporated a linear reciprocating mechanism driven by piezoelectric ceramics on the satellite. This setup allowed for the derivation and analysis of additional interference torque， which resulted from the movement of small masses. The analysis was grounded in the principles of satellite attitude dynamics. Secondly， the composite axis system's main and auxiliary axes were individually tuned， and the system's bandwidth was calculated to ensure it meets performance requirements. Following this， a feed-forward inverse model and adaptive PID control were employed. These techniques compensated for the nonlinearity of the piezoelectric ceramics and any disturbances affecting the satellites. Finally， the feasibility of the overall system was verified by an Adams and Simulink joint simulation. The simulation results show that the intervention of the mechanism can effectively reduce the bandwidth of the control system and realize high-precision pointing stability control of approximately 10 nrad·Hz-1/2@1 mHz~1 Hz.关键词：Drag-free satellite;Composite axis control;Attitude stabilization;piezoelectric ceramics
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发布时间：2023-12-13 - 摘要：Additive manufacturing combined with reactive sintering can be used to fabricate extremely lightweight silicon carbide ceramic mirrors. However， the mechanical properties of silicon carbide prepared by this method， such as flexural strength and elastic modulus， are low and insufficient. A novel method was proposed to improve the properties of silicon carbide by high temperature oxidation. First， silicon carbide prepared by additive manufacturing and reactive sintering was oxidized at 850 ℃. Thereafter， the effect of oxidation time on material composition and surface defect content was studied. The enhancement mechanism of oxidation time on the properties of silicon carbide was elucidated. The results demonstrate that when the oxidation time is 2 h， a dense silica film is in-situ grown on the surface of the material， which can render the surface defects of the material to self-heal and effectively reduce their contents. In addition， the final body obtained the best comprehensive properties by this method， and the flexural strength and elastic modulus are 263.9 MPa and 384.75 GPa， with increments of 10.7% and 14.4%， respectively. This method has the advantages of high efficiency， low cost， and easy operation. The study provides theoretical guidance for improving the performance of additive manufacturing silicon carbide ceramics.关键词：Additive manufacturing;reaction-bonded silicon carbide;oxidation time;properties regulation
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发布时间：2023-12-13 - 摘要：Involute cylindrical gears are a key component of various machines and are widely used in all areas of the national economy. To achieve uniformity in involute measurements， gear involute artifacts are often used as entity standards for the traceability， transfer， and comparison of involute profile deviations. This paper reviews the progress in research on high-precision gear involute artifacts with single and multi-base circular parameters， gear artifacts integrating other geometrical parameters， non-involute artifacts， and high-precision involute measuring instruments in various countries. It also suggests uses of roll path length of gear involute artifacts and provides an outlook on the development of high-precision gear involute artifacts.关键词：involute artifact;involute profile deviations;involute measuring instrument;measurement standard
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发布时间：2023-12-13
Micro/Nano Technology and Fine Mechanics
- 摘要：In hazy weather， the image quality is decreased owing to the scattering effect of atmospheric particles on light， which can affect target detection and key information extraction. In response to the shortcomings of current polarization defogging algorithms， this study proposes a defogging method based on polarization dark channel. First， polarization information is calculated through the polarized light intensity of four different angles， to obtain the polarized light intensity of any angle. Thereafter， based on the dark channel prior principle， the dark channel of the polarized image is defined. The atmospheric light intensity at infinity is obtained， and the atmospheric transmission rate is calculated. Finally， the atmospheric scattering model is constructed to obtain a defogging image. The experimental results demonstrate that the evaluation indicators of grayscale variance， average gradient， and image entropy of the defogged image processed by this method are significantly improved compared to those of the original image. The grayscale variance， average gradient， and image entropy are increased by 25%， 30%， and 5%， respectively. This method can effectively improve the quality and clarity of images in hazy weather and enrich image details.关键词：Polarization image;image defogging;dark channel;prior principle
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发布时间：2023-12-13 - 摘要：Addressing the challenge posed by the low contrast between the choroid and sclera in choroid segmentation， this research introduces the TransGLnet choroid automatic segmentation network， employing an attention mechanism. The incorporation of a Global Attention Module （GAM） within the convolutional layer involves matrix multiplication between features， establishing nonlinear interactions across multiple features in the global spatial context. This enables the extraction of global features without an excessive number of parameters. To explore local features， a Local Attention Module （LAM） is introduced between the convolution layer and Transformer encoder， focusing on a 1/4 feature graph. The movement rule for feature graph elements maintains row position consistency while rearranging elements in the column position from largest to smallest. The integration of these two modules ensures that the network effectively considers both global and local features. Experimental results showcase the efficacy of the proposed TransGLnet network with a Dice value of 0.91， accuracy at 0.98， equal crossover ratio of 0.89， F1 value reaching 0.90， and a Hausdorff distance of 6.56. Comparative analysis against existing automatic choroidal segmentation methods reveals notable improvements in performance metrics. The network presented in this study demonstrates robustness and stability， rendering it suitable for clinical reference.关键词：medical image processing;automatic choroidal segmentation;TransUnet;global attention;local attention
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发布时间：2023-12-13 - 摘要：A fusion method for infrared and visible images was developed based on target enhancement and butterfly optimization to address the problems of target blurring， textural detail loss， and artifacts in traditional infrared and visible image fusion results. First， to deal with the blurring of the fusion target edge caused by the imaging mechanism of the infrared image， an infrared image enhancement module based on target edge enhancement was constructed. Second， a visible light enhancement module based on multiscale Retinex with color restoration was developed to solve the problem of missing details in fused images caused by the low quality of visible images. Third， fourth-order partial differential equations and the principal component analysis method were used to smooth out the edges of infrared and visible enhanced images to solve the problem of artifacts in the fusion results. Finally， an image reconstruction module based on butterfly optimization was designed for the adaptive allocation of reconstructed image weights. This allows the target to be highlighted in the final fusion result while retaining more textural details. To verify the advantages of the proposed algorithm， it was compared with six classic algorithms on the TNO， INO， M3FD， and RoadScene datasets. The experimental results show that the fusion results obtained by the proposed algorithm have clear edges， strong contrast， no artifacts， and rich textural details. Compared with the other algorithms， the objective evaluation indicators EN， SF， SD， JE， VIF， and NSS are improved by an average of 9.24%， 38.88%， 51.11%， 4.65%， 35.44% and 19.36%， respectively.关键词：image fusion;infrared image;visible image;multi-scale;Butterfly optimization
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发布时间：2023-12-13 - 摘要：This paper proposes a fusion of multiplexed optical sensors and variable integral PID methods for intelligent handling robots to deal with their inability to realize accurate trajectories in complex environments. First， a short-wavelength semiconductor laser sensor and multiple grayscale sensors were used to sample the trajectory in real time， and the collected data were preprocessed by applying the sliding average filtering algorithm. Then， the deviation of the data from the equilibrium state was calculated using a combined multi-optical sensing and variable integral PID control algorithm. The accumulation and fusion were weighted， which serves as the input of the variable integral PID control algorithm and reduces the convergence distance to 10 cm. Finally， to expand the applicability of the gripping structure of the object block， a four degrees-of-freedom robotic arm， extractor pump， and load table were used to form a grasping structure. The experimental results show that the algorithm can perform the functions of QR code recognition， stable trajectory， and block grasping and handling in 3 min， in both indoor and outdoor environments. The robot has a task handling accuracy rate of 100%. The algorithm improved the stability and environmental adaptability of the trajectory of the handling robot， strengthened the real-time feedback of the robot route in the process of handling the trajectory， and accelerated the robot's response to the trajectory error， which is of great significance for automation technology.关键词：Photoelectric handling robot;semiconductor laser;PID control algorithm;QR code recognition
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发布时间：2023-12-13 - 摘要：To achieve a smooth autonomous landing of the intermeshing-rotor unmanned helicopter in the presence of GPS signal interference， the TAG36H11 image from the AprilTags visual fiducial system was used as the landing landmark. A vision assisted autonomous landing control system for the intermeshing-rotor unmanned helicopter was designed based on this landmark. The process involved image pre-processing of the landing landmark， followed by the extraction of feature information using Canny edge detection， Hough transform straight line detection， and rectangle detection. The system then solved for the relative position and attitude of the unmanned helicopter using camera imaging principles and coordinate system conversion. An algorithm to determine the yaw angle using Hough transform linear detection was proposed， specifically for scenarios with GPS signal interference. The control system incorporated a cascade PID control structure， including a square root controller in position control to limit the desired position and maximum acceleration of the helicopter. In addition， an intermeshing-rotor unmanned helicopter attitude control mechanism was designed， which adjusted the cyclic pitch of the intermeshing-rotor by controlling the swashplate angle with six digital servos. This mechanism was pivotal in altering the flight attitude of unmanned helicopters. The system's effectiveness was verified through simulations with the Mission Planner flight control ground station， which combined the vision processing system with the flight control system. These simulations show that the vision-assisted flight control system can accurately track the desired position of the unmanned helicopter. After experimental verification， it is found that the attitude angle offset is controlled within 4° and the position offset within 0.05 m， demonstrating the system's capability to realize the intermeshing-rotor unmanned helicopter's vision-assisted autonomous landing.关键词：visual aid;intermeshing-rotor unmanned helicopter;autonomous landing;position control;attitude control
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发布时间：2023-12-13
Information Sciences
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