An Improved Method of Location of the Circular Target

In this paper, the two invariants in the perspective projection model of camera imaging process are analyzed and a five-point constraint is put forward. And then methods of determining the true projective position of the circular target using a concentric circular target, and an optimal method of suppressing stochastic errors in the location of circle centers with the optimization object function based on cross-ratio and the straightness of the fitting line are proposed with the help of hybrid particle swarm algorithm. All methods are combined into one locating method to obtain the true circles´ centers. The experiment shows that those methods which could be applied to computer vision and camera calibration are effective to compensate for the locating errors.