Shape measurement of discontinuous objects using projected fringes and temporal phase unwrapping

Abstract

Temporal phase unwrapping is a method of analyzing fringe patterns in which the fringe phase, /spl Phi/, at each pixel is measured and unwrapped as a function of time, t. We propose a method for improving the signal-to-noise ratio of the total phase change by incorporating data from the intermediate phase values. The performance of the method is compared theoretical and experimentally, using data from a fringe projector based on a spatial tight modulator. The best way to use the method is with /spl Phi/ decreasing exponentially with time from its maximum value to zero; this provides significant improvements in reliability, accuracy and computation time compared with the original temporal unwrapping algorithm.