Calibration of a 3-D surface contouring and ranging system

A new 3-D surface contouring and ranging system based on a digital fringe projection and phase shifting technique is described. In this system, three phase-shifted fringe patterns and a centerline pattern are used to determine the absolute phase map of the object. This phase map is then converted to the absolute x, y, and z coordinates of the object surface by a transformation algorithm To determine the accurate values of the system parameters as required by the transformation algorithm, a two-step calibration procedure was developed. First the parameters were indirectly measured through experiments to determine their approximate values. Second, a calibration plate whose features were calibrated by a coordinate measuring machine (CMM) was measured by the system at various positions. An iteration algorithm was then used to estimate the system parameters. Measurements of the calibration plate, a sheet-metal panel, and a Ford master gauge showed results consistent with the actual surface contours of the objects.