Active vision-based accuracy calibration technology for measurement devices

The method for the accuracy calibration and maintenance of vision measuring device was studied to meet the requirement of the accuracy and stability of the measurement device in industrial online monitoring. An imaging model to which image distortion was introduced in the principle of perspective was analyzed. The trajectory equation of spots moving in the distortion image when the measuring device was in linear motion in relation to the laser was deduced. The method for accuracy calibration of active vision-based measurement device was proposed. The procedures were as follows: Firstly, gathering the information on feature points necessary for calibration from the in-plane translational motion of the measurement device under control; secondly, obtaining the distortion coefficient of measurement image by the spot trajectory equation and correcting the image distortion; and at last, getting the homography matrix between the image plane and the measured plane to complete the accuracy calibration. The layout of the feature points was optimized. The experimental results indicate that the peak value error of centering measurement is 0.373 pixel, and the root-mean-square error is 0.178 pixel. The method is easily applicable and accurate enough for industrial online monitoring.