检索结果-南通市图书馆

Fast generation of controllable equal-intensity four beams based on isosceles triangle multilevel phase grating realized by liquid crystal spatial light modulator

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2011年第2期20卷 287-294页

作者：刘翔张健吴丽莹甘雨 Institute of Ultra-precision Optoelectronic instrument Engineering Harbin Institute of Technology

Liquid crystal spatial light modulator （LCSLM） realizing equal-intensity multiple beams often has some features, i.e., phase valley between two adjacent pixels, flybaek region when phase decreases immediately from 2~r to 0, and inevitable backplane curvature, which are different from those of most conventional diffractive optical elements （DOEs）, such as static DOEs. For optimal intensity uniformity, equal-intensity multi-beam generation must be considered for these artifacts. We present a tunable-grating method in which the intensity uniformity can be improved by considering the LCSLM artifacts. For instance, tuning phase modulation depth of the grating, called isosceles triangle multilevel phase grating （ITMPG）, can be used not only to improve the intensity uniformity, but also to fast steer four beams with narrow beamwidths, determined by the same effective aperture of ITMPG. Improved intensity uniformity and high relative diffraction efficiency are demonstrated through experiments with phase-only LCSLM.

关键词： liquid crystal spatial light modulator phase grating splitter

Fiber-based multiple access timing signal synchronization technique

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2017年第4期26卷 132-137页

作者：袁一博王波高超王力军 Joint Institute for Measurement Science State Key Laboratory of Precision Measurement Technology and InstrumentsTsinghua University department of Physics Tsinghua University department of precision instrument Tsinghua University

A fiber-based,multiple access timing signal synchronization scheme is *** coupling out the bidirectional transmission signals,a highly stable timing signal can be recovered at arbitrary points along the fiber with the help of the loop delay message broadcasted via ethernet from the local *** experiment is carried out on a 30-km fiber placed in a temperature-controlled *** one-day period,when the round trip fiber transfer delay fluctuation is60 ns,the fluctuations of the stabilized timing signal from the download and the remote modules were only ±125 ps and±100 ps,***,the system error caused by transmission path asymmetry and thermal drift is calibrated,and a100-ps magnitude synchronization accuracy is *** method could provide new insights into the construction of a fiber-based time transfer network.

关键词： time synchronization multiple access time transfer

Realtime Vision-Based Surface Defect Inspection of Steel Balls

在线全文

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2015年第1期21卷 76-82页

作者：王仲邢芊付鲁华孙虹 State Key Laboratory of precision Measuring Technology and instrument School of Precision Instrument and Opto-Electronics Engineering Tianjin University

In the proposed system for online inspection of steel balls, a diffuse illumination is developed to enhance defect appearances and produce high quality images. To fully view the entire sphere, a novel unfolding method is put forward based on geometrical analysis, which only requires one-dimensional movement of the balls and a pair of cameras to capture images from different directions. Moreover, a realtime inspection algorithm is customized to improve both accuracy and efficiency. The precision and recall of the sample set were 87.7% and 98%, respectively. The average time cost on image processing and analysis for a steel ball was 47 ms, and the total time cost was less than 200 ms plus the cost of image acquisition and balls' movement. The system can sort 18 000 balls per hour with a spatial resolution higher than 0.01 mm.

关键词： machine vision steel ball defect inspection image processing

A Soft Robotic Fish Actuated by Artificial Muscle Modules(SoRoFAAM-1)

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2023年第5期20卷 2030-2043页

作者： Moise Raphael Tsimbo Fokou Qirong Xia Hu Jin Min Xu Erbao Dong CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Precision Machinery and Precision InstrumentationUniversity of Science and Technology of ChinaHefei230026China

In this paper,we present the design,fabrication,locomotion and bionic analysis of a Soft Robotic Fish Actuated by Artificial Muscle(SoRoFAAM).As a carangiform swimmer,the most important part of SoRoFAAM-1,on the motion point of view,is its tail designed around a bidirectional flexible bending actuator by layered bonding *** actuator is made of two artificial muscle modules based on Shape Memory Alloy(SMA)*** artificial muscle module has four independent SMA-wire channels and is therefore capable of producing four different *** design allows us to implement an adaptive regulated control strategy based on resistance feedback of the SMA wires to prevent them from *** improve the actuation frequency to 2 Hz and the heat-dissipation ratio by 60%,we developed a round-robin heating ***,the thermomechanical model of actuator is built,and the thermal transformation is *** relationships between the actuation parameters and SoRoFAAM-1’s kinematic parameters are *** versatility of the actuator endows SoRoFAAM-1 with cruise straight and turning ***,SoRoFAAM-1 has a good bionic fidelity;in particular,a maneuverability of 0.15,a head swing factor of 0.38 and a Strouhal number of 0.61.

关键词： Soft robotic fish Artificial muscle Shape memory alloy Head swing factor Maneuverability Bionic fidelity

Fiber fuse behavior in kW-level continuous-wave double-clad field laser

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第1期25卷 600-603页

作者：孙骏逸肖起榕李丹王雪娇张海涛巩马理闫平 Center for Photonics and Eleconics Department of Precision InstrumentTsinghua UniversityBeijing 100084China

In this study, original experimental data for fiber fuse in kW-level continuous-wave （CW） high power double-clad fiber （DCF） laser are reported. The propagating velocity of the fuse is 9.68 m/s in a 3.1-kW Yb-doped DCF laser. Three other cases in Yb-doped DCF are also observed. We think that the ignition of fiber fuse is caused by thermal mechanism, and the formation of bullet-shaped tracks is attributed to the optical discharge and temperature gradient. The inducements of initial fuse and formation of bullet-shaped voids are analyzed. This investigation of fiber fuse helps better understand the fiber fuse behavior, in order to avoid the catastrophic destruction caused by fiber fuse in high power fiber laser.

关键词： fiber lasers high power lasers laser damage

Light People:*** Mazur speaks about ultrafast optics and education

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2024年第3期13卷 402-406页

作者： Chenzi Guo Yang Li Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchunChina State Key Laboratory of precision Measurement Technology and instrument Department of Precision InstrumentTsinghua UniversityBeijingChina

*** Mazur is a great influencer over and beyond the optics *** a physicist,he is a pioneer of ultrafast optics and was one of the inventors of colliding-pulse mode-locked *** an educator,he not only gave talks to thousands,but also revolutionized teaching with his globally renowned methodology“Peer Instruction”.As a leader and entrepreneur,he co-founded several companies and was President of Optica(formerly the Optical Society)and currently is the Chair of the Optica ***,Light:Science&Applications talked with *** Mazur about his opinions on research,education and *** full interview video can be found in the Supplementary File.

关键词： optics education companies

Environmental temperature effect on dimensional measurements of atomic force microscopy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nanotechnology and precision Engineering 2021年第2期4卷 20-24页

作者： Chengfu Ma Yuhang Chen Wenhao Huang Key Laboratory of precision Scientific instrumentation of Anhui Higher Education Institutes Department of Precision Machinery and Precision InstrumentationUniversity of Science and Technology of ChinaHefei 230026China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Precision Machinery and Precision InstrumentationUniversity of Science and Technology of ChinaHefei 230026China

Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in *** the environmental temperature is not controlled in many measurements,or is even varied on purpose,quantification of its effects on AFM dimensional measurements is *** this paper,the influences of the temperature in the entire environment of the AFM(excluding only the controller and computer)and that in the local environment around the tip–sample are *** results show that lateral dimensional measurements are affected mainly by the entire environmental ***,vertical measurements are influenced by the temperature of both the entire environment and the local *** effects become significant for temperatures higher than some threshold,here between 35 and 40 XC.

关键词： Atomic force microscopy Environmental temperature Dimensional measurement Pitch Height

An efficient Jacobian scaling method for time-domain optical mammography

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2010年第2期8卷 206-209页

作者：马艺闻高峰阮平巧杨芳赵会娟 State Key Laboratory of precision Measuring Technology and instruments Tianjin University College of precision instrument and Optoelectronics Engineering Tianjin University

Time-domain diffuse optical tomography can efficiently reconstruct optical parameters which can be further applied in diagnosing early breast cancer. Nevertheless, the performances of reconstructed imaging are badly influenced by different Jacobian magnitudes of absorption coefficient and reduced scattering coefficient. With the introudction of a relative data type based on generalized pulse spectrum technique, an efficient Jacobian scaling method is proposed. The interrelated simulated validation is also revealed for the enhancing performances.

关键词： Diagnostic radiography Optical tomography

A Novel Tunable Dual-frequency Laser with Large Frequency Difference

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 2002年第4期11卷 12-15页

作者：黄春宁郭辉李岩朱钧张书练 Dept. of precision instruments Tsinghua University The State Key Laboratory of Precision Measurement Technology and Instrument 北京 100084 Dept. of precision instruments Tsinghua University The State Key Laboratory of Precision Measurement Technology and Instrument 上海 100084

This paper proposed a novel tunable dual frequency laser with large frequency difference,which used LD to pump the Nd∶YAG microchip in the end surface and put the liquid pressure on the radial direction of the crystal by a pressure transporting thin film. As a result of the stress birefringence, there was a mode splitting phenomenon of the microchip laser longitudinal mode. Both theoretical analysis and experiments indicated that there is a directly proportional relation between the frequency difference and the pressure, so the tunable frequency difference could be obtained when the pressure was changed. A large frequency difference of about 3.4 GHz with linear tunable relation was achieved in the experiment,so it can be a practical light source for the absolute distance interferometry.

关键词： large frequency difference tunable dual frequency LD pumped Nd∶YAG laser