基于单目视觉的中医诊疗机械手三维坐标定位和变换方法

为了在按摩、针灸等中医相关诊疗过程中,高效率定位中医按诊所需腧穴.结合单目视觉标定与定位原理,提出了一种基于三维坐标系之间转换矩阵求取的中医诊疗机械手坐标定位和转换方法.通过进行相机标定得到相机内参数并建立相机三维世界坐标系,再基于可粘贴于机械手任意固定位置的自定义标签图像建立相机三维世界坐标系与机械手坐标系的转换关系...     

一种光学遥感卫星多相机成像系统的高精度影像拼接方法EI北大核心CSCD

提出一种基于虚拟大相机的光学遥感卫星多相机系统成像数据的拼接方法,实现多相机影像的高精度拼接。该方法根据各单相机的几何成像模型,构建虚拟大相机的几何成像模型;利用坐标正算、反算过程对各单相机影像进行间接法几何纠正,得到虚拟大相机图像坐标系下的各虚拟单相机影像;将各虚拟单相机影像基于影像坐标信息拼接处理后得到最终的虚拟大相机影像。该方法利用虚拟大相机实现多相机影像的高质量拼接,为后期处理提供了与之相对应的高精度有理函数模型,可用于不同数量、不同分辨率的多相机系统实现全自动智能地面预处理。     

一种光学遥感卫星多相机成像系统的高精度影像拼接方法

提出一种基于虚拟大相机的光学遥感卫星多相机系统成像数据的拼接方法,实现多相机影像的高精度拼接。该方法根据各单相机的几何成像模型,构建虚拟大相机的几何成像模型;利用坐标正算、反算过程对各单相机影像进行间接法几何纠正,得到虚拟大相机图像坐标系下的各虚拟单相机影像;将各虚拟单相机影像基于影像坐标信息拼接处理后得到最终的虚拟大相机影像。该方法利用虚拟大相机实现多相机影像的高质量拼接,为后期处理提供了与之相对应的高精度有理函数模型,可用于不同数量、不同分辨率的多相机系统实现全自动智能地面预处理。     

中国探月工程“嫦娥三号”将首次以月基天文望远镜观测天体

我国将于2013年12月实施嫦娥三号探月任务,嫦娥三号作为探月二期工程的主要任务,将实现我国航天器在地外天体首次软着陆,从嫦娥三号着陆器中释放出的月球车,将进行我国首次在月表巡视探测.这是继美国阿波罗计划后人类重返月球的首个月球软着陆探测器."嫦娥三号"执行的任务中有其他国家没有做过的.一是利用"嫦娥三号"就位和巡视的特色,制定了一个特殊的科学目标:"观天,看地、探月".第一,观天,用月基天文望远镜观测天文;第二,看地,用月基极紫外照相机监测地球等离子体层的密度     

“句芒号”激光光斑质心提取方法与稳定性分析

根据句芒号足印影像特点,提出一种针对复杂背景噪声的激光光斑质心提取方法：基于灰度转换模型去除地物背景,结合距离约束、高斯滤波和大津阈值分割去除影像噪声,并利用灰度重心法计算质心坐标。使用所提方法对多种地物类型仿真光斑和实测光斑进行质心提取,结果表明：所提方法的质心提取均方根误差约为0.074 pixel,最大误差约为0.482 pixel,对句芒号光斑影像的适应性较好。对句芒号足印影像光斑开展了稳定性分析,结果表明,所有激光波束的光斑质心坐标的标准差小于0.34 pixel,激光器与光轴监视相机的相对几何关系较为稳定。所提方法可用于激光光斑质心提取及稳定性监测,对句芒号激光数据处理和应用有一定参考价值。     

一种无公共视场相机位置关系的求解方法

多相机系统的标定是立体视觉测量中的一个重要问题。而当各相机间公共视场较小或无公共视场时,标定参照物不能同时出现在所有相机的公共视场,因此无法求解系统中多相机的相对位置关系。针对该类问题,论文在二维靶标标定法的基础上,提出了一种基于两轴转台的无公共视场相机位置关系的求解方法。将待标定系统固定在转台上,利用转台转动确定靶标坐标系与转台坐标系之间的相对关系;通过转动转台使二维靶标依次进入每个相机视场以分别确定转动后每个相机在靶标坐标系中的位置,并记录转动的角度;最后,结合靶标坐标系与转台坐标系关系,求解各相机之间的相对位置关系。实验结果表明,该方法具有可操作性,解算误差在0.5%以内,可较准确地确定多个光轴之间角度较大的非共视场相机位置关系。     

微通道板光子计数成像探测器预处理实验研究

微通道板光子计数成像探测器是嫦娥三号极紫外相机的关键成像器件,嫦娥三号极紫外相机被用于探测地球等离子层中极微弱的He+共振散射辐射,为了消除微通道板内部吸附的残余气体产生的离子反馈等背景噪音对探测器微弱信号成像性能的影响,需要对微通道板进行预处理.预处理包括高温真空烘烤和紫外光电子清刷.根据预处理的实验要求,设计了一套微通道板预处理装置,为微通道板预处理实验提供高真空环境和高温加热及保温功能.本文详细介绍了微通道板预处理实验的实现过程,对三片Z型级联的微通道板进行预处理实验后,背景噪音由27.09counts/s·cm2降低为0.53counts/s·cm2、空间分辨率达到125μm,上述实验结果表明MCP在预处理之后其表面、亚表面和体内吸附的杂质气体得以有效去除,获得了稳定的增益,成像性能也得以改善.     

嫦娥三号全景相机图像全景镶嵌方法的研究

为实现嫦娥三号月球车全景相机图像的无缝镶嵌,针对全景相机序列图像光照不均、月表影像的特殊性等问题,提出了一种基于加速稳健特征(SURF)算法的嫦娥三号全景相机图像全景镶嵌方法。采用SURF算法提取特征点,用SURF描述子的欧氏距离作为判定度量进行特征匹配。求取相邻两幅图像间的变换矩阵,并利用Levenberg-Marquardt非线性优化算法进行优化。采用基于线性插值的渐入渐出方法对图像重叠区域进行融合,实现月表图像的无缝镶嵌。结果显示,该方法针对嫦娥三号全景相机图像实现了快速准确的镶嵌,生成的镶嵌图满足月球车探测目标选取及路径规划的需求。     

基于坐标转换的数字天顶仪定向方法

为了提高仪器的工作效率,在数字天顶仪定位的基础上开展了定向方法的研究,构建了识别星点的坐标转换模型.从坐标转换模型出发,分析了仪器倾斜及光轴倾斜等因素对恒星像点图像坐标的影响,研究了焦距值及光轴指向的天文坐标对恒星理论坐标的影响,并在坐标转换的基础上建立了定向模型.试验结果表明,单组星图的定向精度均在5″以内,定向精度较高,能够满足实际条件下对定向精度的要求.     

自由度冗余蛇形臂机器人手眼标定研究

针对自由度冗余蛇形臂机器人的手眼标定问题,提出一种不依赖蛇形臂机构运动参数求解视觉系统与末端法兰盘手眼关系的方法;借助外部辅助双目相机系统,通过构造外部相机、末端法兰盘、视觉导航相机三者坐标系的闭环转换得到待求手眼关系;首先根据立体视觉原理得到标志点在对应相机坐标系下的3D坐标;然后利用四元数法分别求得外部相机坐标系与法兰盘坐标系、外部相机坐标系与视觉导航相机坐标系间的转换关系;最后构建坐标系转换关系闭环求得手眼关系;实验结果表明,该标定法避免了蛇形臂自由度冗余导致运动控制精度差带来的干扰,标定精度满足设计要求。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.