Calibration of a three-dimensional shape measurement system

A 3-D surface shape measurement 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 x , y , and z coordinates of the object surface by a conversion algorithm. To determine the accurate values of the system parameters as required by the conversion algorithm, a two-step calibration procedure was developed. The parameters were first measured to determine their approximate values, then a calibration plate was measured by the system at various positions, and an iteration algorithm used to estimate the system parameters. Measurement results of several objects are presented. The standard deviation of the measurement error was found to be 0.23 mm.