Modeling and Calibration of a Structured-light Optical CMM via Skewed Frame Representation

Abstract

A new tetrahedron-target-based approach is presented for the extrinsic calibration of a non-contact “light-striping” (structured light) optical coordinate measuring machine (CMM). The procedure makes automated on-line calibration possible. The system modeling is based on a unique skewed frame representation without the use of pin-hole camera model assumption. It is demonstrated that the extrinsic calibration matrix can be decomposed into two classes of transformations, one homogeneous and the other nonhomogeneous. The nonhomogeneous transformation between a Cartesian world frame and the non-Cartesian skewed sensor frame is studied. The sensitivity of the dimensional deformation on the two skew angles is simulated. Experimental studies show that a micron level calibration accuracy can be achieved.