Non-uniform sampling based frequency shifting fringe projection technique

Recently, the frequency-shifting (FS) projection technique provides a promising alternative to the traditional phase-shifting (PS) fringe projection profilometry (FPP). It solves the absolute phase retrieval problem directly in a completely different fashion, without any phase unwrapping. However, due to the Nyquist sampling theorem (NST), a constant frequency-shift only supports for a limited effective field (EF). It only covers a limited region of the fringe pattern, and the phase retrieval quality degenerates dramatically for those out of the EF. This issue tends significant especially for a high-resolution fringe pattern, limiting the practical application in real life. To this end, we introduce the non-uniform sampling strategy into frequency-shifting technique. With a temporally varying frequency-shift, the EF can be improved significantly, achieving globally high quality across all regions in the pattern for the retrieved phase. Simulation and real experimental results have validated the efficacy of the proposed technique.