Center extraction method of circular coding target based on radial line fitting of coding ring

Aiming at the problem that the center extraction accuracy of the circular coding target is easily affected by camera angle, a method to extract the center based on the radial line fitting of the coding ring is proposed in this paper. Firstly, the radial straight line edge of the circular coding target ring is obtained by edge extraction after image preprocessing, The extracted sub-pixel edge points set is mapped to the parameter space into curves, and the intersection points between all curves are found. Finally, the RANSAC (Random Sample Consensus) algorithm is used for fitting the line to the above points, and the actual center is obtained by mapping the fitted line to the original coordinate space. Compared with the ellipse fitting method, the reprojection error of the camera calibration by the extracted targets centers is reduced by 20%, and the calibration result is more accurate and reliable.