The central accuracy of circular targets is an important factor that has direct effect on the accuracy of calibration and the accuracy of measurement in the system based on binocular stereo.The traditional operator has poor accuracy which can not reach the requirement of high-precision measurement.The edge is measured by using Canny operator

the edge is relocated with sub-pixel by means of Zernike moment operator and the targets center location using least square fitting method.The experiment proves that the center of targets can be detected with high accuracy

the central accuracy is less than 0.1 pixel

the system error is less than 0.02mm

which can reach the requirement of measurement precision.