基于亚像素图像拼接的透明元件视觉测量方法

Visual Measurement Method for Transparent Elements Based on Sub-Pixel Image Mosaics

针对透明光学元件特征不明显以及机器视觉难以进行大视场、高精度尺寸测量的问题,提出一种基于亚像素图像拼接的视觉测量方案.该方案对相机坐标系与世界坐标系间的旋转角进行标定,获得精确的尺度因子与图像预匹配结果;图像坐标系旋转角校正后小于0.1°;通过添加网格背景实现透明元件特征匹配.所提基于滑动窗口预匹配、随机采样一致性筛选最佳偏移向量的配准算法,使图像拼接精度达到0.05 pixel,较已有研究明显提升.将该方案应用于透明光学元件视觉检测系统中,在移动精度仅为0.02 mm的条件下,获得了平均误差为0.12 pixel的图像拼接结果,实现了透明光学元件的大视场、高精度尺寸测量.

A vision measurement scheme based on subpixel image stitching is proposed to solve the problems of unclear features of transparent optical elements,difficulty in the large field of view,and highprecision dimension measurement by machine vision.Furthermore,the rotation angle between the camera coordinate system and the world coordinate system is calibrated in the proposed scheme to obtain accurate scale factors and imagematching results.The rotation angle of the image coordinate system is less than 0.1°after correction.Additionally,feature matching of transparent components is achieved by adding a grid background.The proposed registration algorithm based on sliding window prematching and random sampling consistency to screen the best offset vector increases the image mosaic accuracy to attain 0.05 pixel,which is significantly improved compared with the previous studies.The scheme is applied to the vision inspection system of transparent optical elements.Under the condition that the moving accuracy is only 0.02 mm,the image mosaic result with an average error of 0.12 pixel is obtained,and the large field of view and highprecision size measurement of transparent optical elements are realized.