Noncontact interferometric optical probe for calibration of coordinate measuring machines

Our work deals with point length standards, which can be practically realized by two precise spheres or parts of spheres connected by a bar or array of spherical surfaces. The distance between the centers of spheres precisely determines the length. Two methods (mechanical and optical) are shown for determination of the centers of spheres of the length standard. The proposed optical method is based on the interference of light. General formulas are derived that make it possible to calculate accurately the center position of the spherical surface, which is used for the length standards. An analysis of the proposed method is described based on the third-order aberration theory. The proposed technique can be used for calibration and checking of computer numerical controlled machines.