基于激光测距原理的锻件倾斜度测量

提出了一种基于激光测距原理的倾斜度测量方法。首先,利用激光位移传感器采集锻件表面信息, 并采用基于回归分析的异常值判别方法剔除测量数据中的异常值; 然后,将获得的距离信息经坐标变换转换为坐标信息,用直接最小二乘法对离散点进行椭圆曲线拟合; 最后,拟合竖直方向的多个椭圆长轴中心点得到锻件中轴线的三维直线方程,根据直线方程计算锻件的倾斜角度。实验结果表明:该方法的测量误差<0.1°。     

三维直线的表示及其约束

三维直线的表示是计算机图形学和计算机视觉中最基本的问题之一。在介绍了直线的表示原则以及分析了二维和三维直线的各种表示方法的基础上,选择并提出了适合三维重建的二维和三维直线表示方法：用法线式表示法表示二维直线;基于法线式表示法用垂直相交两平面表示法表示三维直线。提出了二维和三维直线的坐标概念,给出了正轴测投影和透视投影下三维直线之间的一些基本约束关系及其证明。     

基于同视场参考点的落点坐标测量系统的设计与应用

提出了一种用于测量空间三维点坐标的单摄像机模型。该模型利用透视投影几何关系,对摄像机参数进行标定,制定固定关联基准,建立参考点与被测点的平面方程,利用这两个条件,建立相应的数学模型,通过读取单目CCD摄像机像面坐标,就可重建物体落点的三维坐标。     

wMPS系统中扫描光面的拟合与评定技术

工作空间测量定位系统是一种采用光平面交汇原理的大尺寸坐标测量系统,测量过程中发现扫描光面并不是理想平面,影响了测量精度.提出了一种思路:利用二次曲面方程来描述扫描光面.运用线性最小二乘法对扫描光面上的离散点进行拟合,得到二次曲面方程,在正交线性变换的基础上,分析了扫描光面的形状.对同一组测量点数据分别用二次曲面和平面进行拟合,将拟合的效果进行比较,结果表明:利用抛物柱面方程能够更准确地描述扫描光面.     

平面三次代数曲线(连载No.10)

10 焦点曲线10.1 二级曲线束设k_2为二次曲线。若将k_2看做是直线的包络,则称k_2为二级曲线;若将它看做是点的轨迹,则称做二阶曲线。设u_1,u_2,u_3,表表示平面上的直线坐标,则中_2的方程可表示成     

基于3D视觉的微通道换热器定位与尺寸测量

为实现微通道换热器生产线的自动化与智能化,提出一种基于3D视觉的微通道换热器定位与尺寸测量方法,以引导机械臂进行抓取上下料。首先,用3D相机以俯视角度拍摄产品,矫正获取的图像并将RGB图像与深度图像对齐;其次,通过产品3D信息的辅助实现精确的二维图像分割以及角点的二维坐标定位;最后,加权拟合角点的深度值,通过角点二维坐标及深度信息进行坐标转换得到其三维坐标,计算产品尺寸。实验结果表明:该算法能够在复杂的背景中实现精确的图像分割与尺寸测量,在测量距离为4000mm时相对测量误差可控制在1%以内,能够满足系统需求。     

无位姿约束的线激光视觉传感器参数标定

针对现有线激光单目视觉传感器参数标定方法中靶标移动需要精密机械控制或可自由移动靶标摆放位姿受约束等不足,提出一种靶标可自由移动且摆放位姿无约束的新标定方法.根据靶标特征点的成像点所构成向量簇的叉积方向集合的射影不变性,对成像点排序,建立靶标特征点与其成像点的对应关系;由光刀中心拟合直线与靶标特征点的成像点所构成包络求交,提取光平面特征点,并根据交比不变原理计算其三维坐标;最优化拟合计算单目摄像机内外参数及线激光投射器光平面参数,实现传感器参数的精确标定.试验表明,该标定方法操作自由、步骤简便,具有较理想的标定精度.     

图像测速法的摄像机标定技术

针对漂浮在空气中或者液体中的粒子的速度测量,提出了一种基于双目视觉的测量方法。采用两个光轴相互垂直的CCD摄像机,分布在测量腔体的左右两侧。结合系统的几何结构特点,两个CCD摄像机分别标定,将标定模型方程转化为多项式形式,利用最小二乘原则获取平面模型标定参数,然后再利用公垂线距离最短原则实现三维坐标测量。实验给出了三维坐标的偏差分布图,证明这是一种实用有效快速的标定方法。     

地面激光扫描仪三维坐标测量精度检测方法

地面三维激光扫描仪是一种新型测量仪器,应用范围广泛,它的精度对测量成果质量起着至关重要的作用。目前,对三维激光扫描仪进行精度评定时,多将三维坐标反算为水平角、竖直角和距离,并建立基准对距离和角度进行精度评定。扫描仪给出的直接数据为三维坐标,反算会引起精度损失。文章提出两种方法评定地面三维激光扫描仪的坐标精度。以Leica AT901跟踪仪测量球形靶标坐标为基准,对Faro Photon80测量的三维坐标精度进行评定;以光滑平面作为基准,对点云进行拟合评定扫描仪精度。     

平面三次和四次代数曲线的射影构成

本文在叠置场上研究平面三次和四次代数曲线的射影构成。提出在射影坐标系里二次线束单参数方程的表示法,并证明它的充分性和必要性。进而证明三个定理:①一次线束和其射影对应的二次线束,所对应直线交点的轨迹为三次平面曲线;②射影三线场对应直线交点构成平面三次曲线;③两成射影对应的二次线束,其对应直线交点的轨迹是四次平面曲线。且写出了上述定理的对偶定理,并在微机APPLE-Ⅱ上作出部分图形。     

多目视觉测量系统的光束法平差改进

为了消除三维扫描测量机器人系统中工业机器人定位误差对测量结果的不利影响,搭建了多目视觉测量系统对三维扫描测头进行空间同步定位.由于系统中相机与标志点之间的距离变化较大,标志点重投影误差难以评价空间定位误差,另外受相机标定精度影响,光束法平差对三维坐标修正不明显.为解决上述问题,本文改进了光束法平差,在传统光束法平差的误...     

Estimating three-dimensional vehicle motion in an outdoor scene using stereo image sequences

We propose a motion estimation system that uses stereo image pairs as the input data. To perform experimental work, we also obtain a sequence of outdoor stereo images taken by two metric cameras. The system consists of four main stages, which are (1) determination of point correspondences on the stereo images, (2) correction of distortions in image coordinates, (3) derivation of 3D point coordinates from 2D correspondences, and (4) estimation of motion parameters based on 3D point correspondences. For the first stage of the system, we use a four-way matching algorithm to obtain matched point on two stereo image pairs at two consecutive time instants (t_i and t_{i + 1}). Since the input data are stereo images taken by cameras, it has two types of distortions, which are (i) film distortion and (ii) lens distortion. These two distortions must be corrected before any process can be applied on the matched points. To accomplish this goal, we use (i) bilinear transform for film distortion correction and (ii) lens formulas for lens distortion correction. After correcting the distortions, the results are 2D coordinates of each matched point that can be used to derive 3D coordinates. However, due to data noise, the calculated 3D coordinates to not usually represent a consistent rigid structure that is suitable for motion estimation; therefore, we suggest a procedure to select good 3D point sets as the input for motion estimation. The procedure exploits two constraints, rigidity between different time instants and uniform point distribution across the object on the image. For the last stage, we use an algorithm to estimate the motion parameters. We also wish to know what is the effect of quantization error on the estimated results; therefore an error analysis based on quantization error is performed on the estimated motion parameters. In order to test our system, eight sets of stereo image pairs are extracted from an outdoor stereo image sequence and used as the input data. The experimental results indicate that the proposed system does provide reasonable estimated motion parameters.     

非球面在线检测的系统误差分离与修正

为了解决非球面在线检测的系统误差问题,针对系统误差产生的机理、误差的数学模型、分离方法以及补偿方法进行了研究.提出一种将空间误差投影到不同平面上进行分析从而解决测量系统误差的新方法并建立了各系统误差的数学模型.根据最小二乘法的基本思想,建立了基于标准球面的系统误差分离数学模型,得到了各参数的最小二乘估计值,并利用误差修正模型进行了校正.利用标准球面进行测量实验,验证了该方法的有效性和精确性.实验结果表明所提出的解决测量系统误差的思路可行,最终可使测量系统精度达到1μm数量级,从而满足精磨阶段在线检测的需要.     

Generalized data reduction approach for aspheric testing in a non-null interferometer

Data reduction in non-null tests is difficult due to the presence of retrace error. We propose a simple yet effective data reduction approach for aspheric testing in a non-null interferometer. The new approach gives figure error of the aspheric by just subtracting the theoretical wavefront and first-order errors from the real wavefront obtained in the non-null interferometer. Precise prediction of the theoretical wavefront can be achieved by accurate calibration of the partial compensation system. The approach can be considered a generalization of the traditional data processing method in null tests, and errors that may affect its accuracy are discussed. A set of experiments have been carried out to demonstrate its validity and feasibility.     

A classical iterative theory based on the Langevin equation for two-dimensional nonlinear terahertz spectroscopy

A classical iterative theory based on the Langevin equation is presented to obtain the nonlinear response of a system and simulate two-dimensional (2D) nonlinear terahertz (THz) spectroscopy (2DTS). Compared with the widely used method of calculating the multi-time correlation function or the Poison brackets, we start from the classical Langevin equation and use an iterative method to obtain any order of nonlinear response. The anharmonic potential (AHP) and nonlinear coordinates dependence of the dipole moment (NDM) are two types of nonlinear sources introduced here. Results are derived for general three-pulse processes with nonlinear sources, AHP or NDM, separately and with the combination of both. Only the simulative 2DTS results for the single mode case with impulsive incident THz fields are presented.     

一种高次光学非球面度的计算方法

针对现有光学非球面度计算方法不统一的问题,在分析常用方法特点的基础上,对于高次光学非球面度的计算提出最小最大残差法。寻找最接近球面,使其沿法线方向与非球面的最大偏离量最小,此时的最大偏离量即为非球面的最大非球面度。该方法适于计算机编程,计算结果准确,且可完全统一二次曲面和高次非球面的非球面度计算。     

Error estimates for frequency responses calculated from time-domainmeasurements

Estimates are derived for the errors in frequency responses calculated from measured step or impulse response data. Three error sources are considered-aliasing errors, errors due to random noise added to the amplitudes of the data, and errors due to random noise added to the time coordinates of the data. Two types of error estimates are derived. Pre-measurement estimates are based on easily determined parameters of the signal and noise; post-measurement estimates are based on the difference between two measurements of the same signal. The post-measurement error estimates apply to additional sources of error. The goal of the paper is to give easily used error estimates for easily implemented methods rather than to present the most sophisticated methods     

交比投影不变原理在结构光平面拟合中的应用

文中简介了机器视觉研究中的一种编码结构光投影系统，在它的编码模板上具有很多的编码特征点，它们在模板的水平和垂直方向上分别构成多组共线的点，经投影后，这些点分别形成了纵向和横向的若干光平面，而这些光平面相对于投影系统三维坐标系的位置关系需要事先标定。在标定过程中需要若干组位于各光平面上的三维空间特征点，将这些点与光平面共同成像于CCD像平面上，再从图像中提取出它们的图像坐标，由共线投影不变性可知，三维特征点所在的直线与光平面所在的直线在CCD像平面上相交于若干点，然后利用代数射影几何中的交比不变原理就可将结构光平面与三维空间点建立对应关系，从而标定出各光平面的参数。文中给出了详细的实验步骤，列出了一些数据及图表，并对实验结果进行了说明。     

Determination of spectrometer-detector parameters from calibration spectra and the use of the parameters in spectrometer calibrations

The grating equation is used to generate quadratic calibration equations for multichannel detectors with perpendicular and tilted focal planes. The quadratic coefficients are not independent and contain terms that are used to solve for spectrometer-detector parameters. The parameters can be calculated from a quadratic fit at one spectrometer position, but more accurate values can be obtained from quadratic fits at two spectrometer positions. The calculations show that the detector focal plane is tilted by about two degrees. Once values for the spectrometer-detector parameters are obtained from calibrations using at least three lines at one or two spectrometer positions, only one calibration line at any spectrometer position is required to obtain accuracies on the order of 0.1 cm(-1) over a several thousand wavenumber range. The main cause of spectrometer drift is a change in the diffraction angle and/or the spectrometer included angle. This drift is almost totally compensated by the one-line calibration, which adjusts the diffraction angle. A neon pen lamp is used to generate the calibration spectra. Using standard air wavelengths compared to true wavelengths can produce calibration errors of 0.1 to 0.6 cm(-1); the magnitude depends on local conditions and how the laser wavelength is treated.     

Considerations for tolerancing aspheric optical components

Optical designs often specify both surface form and centering (tilt and lateral displacement) tolerances on aspheric surfaces. In contrast to spherical surfaces, form and centering errors are coupled for aspheric surfaces. Current standards do not specify how to interpret such tolerances, and in particular they do not define the position of an aspheric surface that has form errors. The straightforward definition that uses the best-fit surface position that minimizes rms error has subtle problems. The best-fit surface position for aspheric surfaces is influenced by power error and can be highly sensitive to surface form errors when the derivative of aspheric departure is small. We analyze the conditions under which form and centering tolerances may be considered compatible when the best-fit surface-position definition is used. We propose alternative definitions of surface position that do not suffer from the same problems and consider their consequences for optical design and metrology.