相位物体的相位检测分析方法

介绍了相位物体的相位检测方法,包括传统的暗场法、纹影法和相衬法,重点介绍基于图像处理的相位物体的双点源光束干涉测量与扫描成像方法,并比较它们的优缺点,同时对目前的研究进展进行了综述.     

High accurate estimation of relative pose of cooperative space targets based on measurement of monocular vision imaging

Autonomous rendezvous and docking (ARD) plays a very important role in planned space programs, the success of ARD rests with the estimation accuracy and efficiency of relative pose among various spacecraft in rendezvous and docking. In this paper, a high accuracy and efficiency estimation algorithm of relative pose of cooperative space targets is presented based on monocular vision imaging, in which a modified gravity model approach and multiple targets tracking methods are employed to improve the accuracy of feature extraction and enhance the estimation efficiency, meanwhile the Levenberg–Marquardt method (LMM) is used to achieve a well global convergence. Moreover an experimental platform with DSP and FPGA is designed and implemented. The comprehensive experimental results demonstrate its outstanding accuracy and efficiency, the update rate achieves 16 Hz and the estimated error of depth does not exceed 2% with noise influence.     

A novel method of camera pose estimation by parabolic motion

Camera pose estimation is a basic and crucial problem in computer vision, accordingly a novel method is proposed for pose estimation based on parabolic motion in our paper. Firstly, the intersection of lines which are the image plane projection of free-falling trajectories in different locations is computed. According to the properties of vanishing point, the intersection is defined as the vanishing point in gravity direction. Secondly, the image plane projected curve of parabolic trajectory is obtained by Sampson Approximation. Finally, the camera pose is estimated by employing the projective geometry properties of vanishing point and vanishing line implicated in the projected parabola, provided that the intrinsic parameters of camera are specified. The absolute Euclidean distance of translation is obtained innovatively with the known frame frequency. Numerical simulation as well as practical experiment in this paper demonstrates the correctness and feasibility of our method, with the known frame frequency, as the experiment show that compared with the traditional checkerboard method the mean errors of rotation axis, rotation angle and translation are respectively 0.017 rad, 0.007 rad and 11.650 mm by our method. It can generally satisfy the accuracy requirements of camera.     

透明体的光学定量测量

综述了使用光学方法测量透明体的方法。介绍了两种常用的光学方法——相衬法和微分干涉相衬法。在 2 0世纪 80年代 ,一般认为相衬法和微分干涉相衬法只适用于定性观察而不能实现定量测量 ,主要是因为在其成像原理中的非线性因素的影响。但是对于微分干涉相衬法 ,最近国内外出现了几种定量测量的方法 ,本文对这几种方法进行了总结和比较。     

Profile measurement of a one-dimensional phase boundary sample using a single shot phase-step method

Phase shifting interferometry is a preferred technique for high-resolution phase profile measurement, but the difficulty in generating the requested shifted pattern has limited the use of the technique to low-noise environment and in case accurate calibration of the phase shifting device is available. In the present experiment, a sample having one-dimensional straight phase boundary is mounted in one arm of an interferometer. One single image of the fringe pattern is recorded, a simple image process is applied generating phase shifted patterns from the original image. Using the appropriate phase shift algorithms, a phase map of the sample is obtained which gives a quantitative measurement of the topographical structure with the resolution of the phase shift method but a single shot recorded pattern.     

基于修正平行投影法的飞行姿态测量

摄影系统的成像满足透视投影模型,使用平行投影法做飞行姿态交会存在模型误差。依据在目标成像的中轴线通过像面中心的时候,平行投影法和透视投影法有相同的成像特征这一事实,提出了一种无模型误差的修正平行投影法。在判读出目标图像中轴线的斜率K和截距L的情况下,假设摄影系统的高低角再旋转atan(L/K)度,使得旋转后图像的中轴线过像面的中心点。依据透视投影模型,计算出旋转后图像中轴线的斜率,再使用此斜率做平行投影交会。仿真结果表明,该方法可以很好的消除由平行投影模型带来的模型误差,为空间目标姿态交会提供了更精确的计算结果。     

Remote atomic information concentration without Bell-state measurement

This paper proposes a scheme for information concentration of two remote two-level atoms in cavity QED. This scheme does not involve the Bell-state measurement. During the interaction between atom and cavity, the cavity frequency is large-detuned from the atomic transition frequency, thus the scheme is insensitive to both the cavity decay and the thermal field. This idea can directly be generalized in the case of multi-atom information concentration.     

Three-dimensional shape measurement for an underwater object based on two-dimensional grating pattern projection

In this paper, a practical method using phase tracking and ray tracing algorithms is proposed for measuring the three-dimensional (3D) shape of an underwater object. A 2D projected sinusoidal fringe goes through the water and illuminates the tested object. Firstly, the phase tracking algorithm is employed to identify homologous points in phase distributions of the deformed fringe captured by the camera and these of the fringe pattern projected by the projector. The projector is regarded as a special camera as regards the stereovision principle. In the calibrated system, both ray directions of the homologous points can be easily figured out. Secondly, the ray tracing algorithm is used to trace the propagation path of each ray and to calculate the 3D coordinates of each point on the tested object's surface. Finally, the whole shape of the tested object can be reconstructed.     

基于影像-位置序图的光学测姿方法

针对空中飞行目标姿态测量问题,提出一种新的光学测姿实现方法,对光学多站测姿实施复杂、单站测姿成像要求高等问题进行改进。该方法充分利用了目标飞行连续影像信息和相应的外弹道位置数据,首先通过目标位置数据确定目标轴线向量起点,根据轴线向量终点的约束方程确定向量终点;然后通过偏航角、俯仰角与轴线向量起点、终点的关系,解算目标姿态角;最后通过姿态连续变化的先验信息,确定解算结果的唯一值。仿真计算和精度分析表明,可实现测姿误差总体小于1,表明提出的方法兼顾了便捷性和测量精度,具有较高工程应用价值。     

提高基于CCD测量精度的新方法

为了提高基于CCD测量系统的测量精度,对传统的基于CCD的测量方法和测量精度进行了研究。当CCD成像平面与被测物体成一夹角α时,导出空间距离与图像像素之间的非线性关系。提出了通过标定和校准来提高基于CCD测量精度的新方法。实际结果表明,该方法可满足对大尺寸物体的高精度测量。     

A two-beam laser triangulation for measuring the position of a moving object

A two-beam laser triangulation method has been proposed to measure the position of a moving object. The method uses two parallel laser beams to judge the moving direction of an object, allowing us to track it and measure its positions. An uncertainty of 0.2 mm for a measurement range of 50 mm has been obtained. This tracking measurement capability is useful in the calibration of the position of a moving robot arm.     

基于共面特征点的单目视觉位姿测量误差分析

为了克服单目视觉测量中景深信息缺失的问题,运用改进的两段式迭代算法,对刚体位姿测量解算模型进行了优化.给出了特征标靶最优化布局,理论分析了标靶尺寸大小、标靶基线长度及特征圆点大小和解算准确度的关系.实验结果表明,优化的特征标靶布局、较大的特征标靶基线长度及较小的特征圆点靶标能够提高测量解算准确度.该研究对提高实际测量系统解算准确度具有一定的理论指导意义.     

Rate of equilibration of a one-dimensional Wigner crystal

We consider a system of one-dimensional spinless particles interacting via long-range repulsion. In the limit of strong interactions the system is a Wigner crystal, with excitations analogous to phonons in solids. In a harmonic crystal the phonons do not interact, and the system never reaches thermal equilibrium. We account for the anharmonism of the Wigner crystal and find the rate at which it approaches equilibrium. The full equilibration of the system requires umklapp scattering of phonons, resulting in exponential suppression of the equilibration rate at low temperatures.     

基于灰度信息的动场景视频序列中运动对象的提取

提出了一种基于视频序列灰度信息的运动对象提取方法。该方法采用改进的Sobel算子提取边缘图像,依据边缘信息将视频图像分割为不同的灰度连续区域。在各灰度连续区域中,选取特征点进行匹配获得特征点对。根据特征点对合并灰度连续区域,获得全局运动参数。采用具有自适应帧间隔的帧差交集法,获得图像中运动对象区域。结合灰度信息和运动信息,分割出运动对象。实验结果表明,该算法可以有效地将运动对象从视频序列中提取出来。     

A new method of three-dimensional measurement by differential interference contrast microscope

Based on weak phase approximation and the partial coherence theory, we analyze the image characteristics of a phase object using a microscope. We show that the image of the phase object is formed by the interplay between the phase distribution and the defocus.Using this theory, we also show the image characteristics of a differential interference contrast (DIC) microscope.We develop a method for extracting the phase component from the DIC image using two images with different retardation to reconstruct the phase distribution of the object. We call our new microscope a “retardation-modulated DIC (RM-DIC) microscope”. We describe the RM-DIC microscope and confirm our method using grating samples with depths of 20 and 50 nm.To measure the three-dimensional (3D) figures of the microstructures on the object using a DIC microscope we need to extract the phase component from the DIC image and to deconvolute the phase component by means of the modulation transfer function (MTF) of the DIC microscope.We conclude that our RM-DIC microscope can take quantitative measurements of the phase distribution, making it a very useful tool for 3D measurement of an object’s microstructures.     

指向精度对光学姿态测量精度的影响分析

为验证光轴指向误差对光学姿态测量精度的影响程度,并为后续实况类设备实现姿态测量提供理论依据,以中轴线法为依据,对算法步骤进行拆分,并对光轴指向误差的影响进行溯源,得出指向误差影响姿态处理结果可从两个方面进行分析。同时对模型内交会算法的直接影响和模型外动态基准的间接影响进行推导分析,将仿真计算和实测数据进行结合验证,获取了在典型中长远光学姿态测量中指向误差200″对姿态角误差不超过0.1°的结论,为现有姿态测量可靠性分析以及后续靶场设备能力拓展奠定了理论基础。     

单目显微视觉测头动态测量技术的研究

为了解决现有坐标测量机中的单目显微视觉测头视场小和景深小的缺点,提出了显微视觉测头的动态测量方法。建立了运动模糊图像的复原模型以及序列图像的全景组合模型,并提出了测量系统的自标定方法,标定重复性精度优于0.5nm。实验证明:该系统在以6mm/s的速度扫描测量时,测量重复性精度可达到5μm。     

Measurement of a discontinuous object based on a dual-frequency grating

The dual-frequency grating measurement theory is proposed in order to carry out the measurement of a discontinuous object. Firstly, the reason why frequency spectra are produced by low frequency gratings and high frequency gratings in the field of frequency is analysed, and the relationship between the wrapped-phase and the unwrapping-phase is discussed. Secondly, a method to combine the advantages of the two kinds of gratings is proposed: one stripe is produced in the mutation part of the object measured by a suitable low frequency grating designed by MATLAB, then the phase produced by the low frequency grating need not be unfolded. The integer series of stripes is produced by a high frequency grating designed by MATLAB based on the frequency ratio of the two kinds of gratings and the high frequency wrapped-phase, and the high frequency unwrapping-phase is then obtained. In order to verify the correctness of the theoretical analysis, a steep discontinuous object of 600×600 pixels and 10.00~mm in height is simulated and a discontinuous object of ladder shape which is 32.00~mm in height is used in experiment. Both the simulation and the experiment can restore the discontinuous object height accurately by using the dual-frequency grating measurement theory.     

The DRESOR method for radiative heat transfer in a one-dimensional medium with variable refractive index

This paper extends the DRESOR (Distribution of Ratios of Energy Scattered by the medium Or Reflected by the boundary surface) method to radiative transfer in a variable refractive index medium. In this method, the intensity is obtained from the source term along the curved integration paths determined only by the variable refractive index, and the DRESOR values are calculated by the Monte Carlo method in which the propagation of the energy bundles are affected by Snell's law. With given temperatures on the black boundaries of a one-dimensional medium, the temperature distribution inside the medium with a variable scattering property is calculated under the condition of radiative equilibrium. It is shown that the DRESOR method has a good accuracy in the cases studied. For an isotropic-scattering medium with the same optical thickness, the scattering albedo has no effect on the temperature distribution, which can be obtained from the general equations and can be seen as an extension of what exists for a constant refractive index; however, the different refractive index causes obvious changes in the temperatures inside the medium. The effect of anisotropic scattering on the temperature distribution cannot be ignored, although it is still weaker than the effect caused by variation in the refractive index.     

Torus maps and the problem of a one-dimensional optical resonator with a quasiperiodically moving wall

We study the problem of the asymptotic behavior of the electromagnetic field in an optical resonator one of whose walls is at rest and the other is moving quasiperiodically (with d≥2 incommensurate frequencies). We show that this problem can be reduced to a problem about the behavior of the iterates of a map of the d-dimensional torus that preserves a foliation by irrational straight lines. In particular, the Jacobian of this map has (d−1) eigenvalues equal to 1. We present rigorous and numerical results about several dynamical features of such maps. We also show how these dynamical features translate into properties for the field in the cavity. In particular, we show that when the torus map satisfies a KAM theorem—which happens for a Cantor set of positive measure of parameters—the energy of the electromagnetic field remains bounded. When the torus map is in a resonant region—which happens in open sets of parameters inside the gaps of the previous Cantor set—the energy grows exponentially.