High-precision visual calibration of motion stage positioning errors using adaptive Zernike moments

Aiming at the problems of insufficient accuracy and cumbersome operation in the precision motion platform error calibration of lithography equipment, this paper characterizes the platform motion information with a high-precision array concentric circle calibration plate, and proposes a visual calibration method of platform positioning error based on A-Zernike moments (Adaptive gradient Zernike). The initial value of the edge is screened according to the morphological characteristics of the target, a linear gradient model is introduced on the basis of the traditional Zernike moment algorithm, and the adaptive acquisition of sub-pixel edges is realized based on gradient sampling and Gaussian fitting to obtain the accurate position of the target center. The system parameters affecting the calibration process are analyzed, and the joint calibration of system parameters is carried out by combining the changes of the target position before and after the motion. Based on the parameter calibration results, the conversion model of image coordinates was constructed and platform displacement to realize the solution and calibration of positioning error. The algorithm performance evaluation experiments and platform error calibration verification experiments show that the edge detection accuracy of the A-Zernike moment algorithm is 47.41% higher than that of the traditional algorithm, and the maximum positioning error of the platform is reduced from 15.601 to 0.783 μm after the calibration, which effectively improves the accuracy and reliability of the calibration of the positioning error of the precision motion platform.