High-quality 3D shape measurement using saturated fringe patterns

This paper proposes a method to potentially conquer one of the challenges in the optical metrology community: optically measuring three-dimensional (3D) objects with high surface contrast. We discover that for digitally equally phase-shifted fringe patterns, if the fringe period P   is an even number, the N=P/2×kN=P/2×k, (k=1, 2, 3, …) step algorithm can accurately recover phase even if the fringe patterns are saturated; and if P   is an odd number, N=P×kN=P×k step algorithm can also accurately recover phase even if the fringe patterns are saturated. This finding leads to a novel method to optically measure shiny surfaces, where the saturation due to surface shininess could be substantially alleviated. Both simulations and experiments successfully verified the proposed method.