Anti-noise and precise circle target center location method of CCD laser autocollimator

To satisfy the stringent requirements for measuring accuracies of charge coupled device (CCD) laser autocollimators in the fields, such as high accuracy metrology system, and azimuth aiming and tracing system, an anti-noise and precise circle target center location method based on orthogonal Fourier-Mellin moments (OFMMs) is proposed. The specific characteristics of the circle target edge of CCD laser autocollimators can be fully extracted, the noises in images can be efficiently diminished by using the rotation invariance and lower radial orders of the orthogonal Fourier-Mellin moments, edge location can be accomplished by setting the edge in vertical direction and analyzing the relationships among these moments of the edge, and the center position of the circle target can be accurately acquired by using the least square fitting method.