3-D shape measurement by composite pattern projection and hybrid processing

Abstract

This article presents a projection system with a novel composite pattern for one-shot acquisition of 3D surface shape. The pattern is composed of color encoded stripes and cosinoidal intensity fringes, with parallel arrangement. The stripe edges offer absolute height phases with high accuracy, and the cosinoidal fringes provide abundant relative phases involved in the intensity distribution. Wavelet transform is utilized to obtain the relative phase distribution of the fringe pattern, and the absolute height phases measured by triangulation are combined to calibrate the phase data in unwrapping, so as to eliminate the initial and noise errors and to reduce the accumulation and approximation errors. Numerical simulations are performed to prove the new unwrapping algorithms and actual experiments are carried out to show the validity of the proposed technique for accurate 3- D shape measurement.