Application of Epipolar Line Rectification to the Stereovision-Based Measurement of Workpieces

A general epipolar line constraint equation for binocular stereo vision is first established for the measurement of workpiece surface, in which the intrinsic parameters of two cameras and their extrinsic structural parameters with respect to a reference base are included. To overcome the drawback of the relative distortion between left image and right image, An epipolar line rectification technique is used for the corresponding point detection in the stereovision-based measurement system. Instead of traditional rectangular window, a circular window sliding on epipolar lines is used to compute the correlation coefficient between the regions surrounding a selected point in the left image and its corresponding point in the right image. The stereovision-based measurement of a T-shaped circular pipe (as an example of workpieces) is carried out using the rectified epipolar lines and the workpiece surface is reconstructed with its acquired three-dimensional coordinates. Experimental results show that the relative distortion of left and right images can be eliminated and the measurement accuracy can be greatly improved after the application of epipolar line rectification, and the workpiece surface is reconstructed with less errors.