Hybrid coding strategy for SNR improvement in 3-step phase measuring profilometry

With fast speed and reliable capability of depth recovery, two-frequency phase measuring profilometry (PMP) is widely used for reconstructing 3-D surface. However, it suffers from random noise when the number of patterns is less. In this paper, we propose a hybrid pattern coding scheme which embeds Gray coding patterns into high-frequency PMP patterns through amplitude modulation. From captured modulated images, wrapped phase and fringe orders can be simultaneously obtained, and then absolute phase will be computed from the wrapped phase with the fringe orders. Both theoretical analysis and experimental results demonstrate that, compared with standard 3-step PMP, the presented strategy can achieve higher accuracy.