具有远近视距的两目视觉系统标定技术研究  

Calibration of Two-Camera Vision System with Far and Near Sight Distance

作　　者：石世锋 叶南[1] 张丽艳[1] Shi Shifeng;Ye Nan;Zhang Liyan(College of Mechanical&Electrical Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing,Jiangsu 210016,China)

机构地区：[1]南京航空航天大学机电学院,江苏南京210016

出　　处：《光学学报》2021年第24期181-192,共12页Acta Optica Sinica

基　　金：国家自然科学基金面上项目(52075260);中央高校基本科研业务费(3082020NP2020305)。

摘　　要：工业机械臂在多工位作业时通常需要具有远近视距的双目视觉系统,用于全局目标定位和局域精确测量。由于具有远近视距的两目相机缺乏公共视场,无法由传统双目立体视觉标定内外参数,提出了一种基于点阵编码元和多视图几何的标定技术。首先为具有远近视距的两目系统制作与之视场大小匹配的两种尺寸的点阵编码元标定板,提出了一种基于灰度梯度的亚像素边缘定位方法以提高椭圆中心定位精度,并改进了点阵编码元的解码算法用于图像特征的稳健匹配。再利用不同视角下编码元的高精度中心像素坐标和图像间编码元的对应关系,通过多视图几何解算出两目相机的内参数和相对各自标定板的转换矩阵。然后由转换矩阵构造AX=ZB手眼标定方程形式,求解方程式中的X即可得到两目相机间的外参数。最后分析了两类优化方法对标定误差的抑制情况。实验结果表明,经优化后标定精度得到提高,角度误差为0.05°,位置误差为0.36 mm。A two-camera vision system with far and near sight distance for global target positioning and accurate local measurement is usually required when an industrial robotic arm works in multiple stations.Lacking a common field of view,the intrinsic and extrinsic parameters of the vision system cannot be calibrated using traditional methods;therefore,a new calibration technology based on point-array coded targets and multi-view geometry is proposed.First,two sizes of calibration panels with point-array coded targets matching the field of view size are prepared for the two-camera vision system with far and near sight distance.A sub-pixel edge detection method based on gray gradient is proposed to improve the positioning accuracy of the ellipse centers.Then,a decoding algorithm of the point-array coded target is improved for robust image feature matching.Based on this,using high-precision central pixel coordinates of point-array coded targets under different perspectives and the corresponding relationship of targets between different images,the intrinsic parameters of two cameras and the transformation matrices between cameras and calibration panels can be calculated using multi-view geometry technology.Then,a hand-eye calibration equation,AX=ZB,is constructed from the transformation matrix,and the extrinsic parameter X between two cameras can be obtained by solving the equation.Finally,the suppression of calibration error by two kinds of optimization methods is analyzed.Experimental results demonstrate that the calibration accuracy is improved after optimization.The angle error is reduced to 0.05°,and the position error is reduced to 0.36 mm.

关 键 词：机器视觉 内外参标定 多视图几何 亚像素边缘 编码元 手眼标定方程式 

分 类 号：TN948.41[电子电信—信号与信息处理] TP391[电子电信—信息与通信工程]