Phase unwrapping algorithm based on double-frequency fringe projection and fringe background

Abstract

A phase unwrapping algorithm specially designed for phase-shifting fringe projection profilometry (FPP) is proposed. This algorithm is based on a principle that combines a refined double-frequency fringe projection algorithm and a fringe background based quality guided phase unwrapping algorithm (QGPUA). The phase demodulated from high-frequency fringe images are partially unwrapped by that from the low-frequency ones. This would help to avoid phase order ambiguity in the eventual phase unwrapping while guarantee the phase resolution. The fringe background based QGPUA is adopted to completely unwrap the partially unwrapped phase. The quality map utilized during the phase unwrapping is generated from the fringe background and divided into different subregions. Further unwrapping for the partially unwrapped phase goes on in the order from phase in the highest quality subregion to that in the lowest one gradually. Partially unwrapped phase in each subregion is unwrapped with flood-fill algorithm. Therefore the phase unwrapping speed can be improved. The proposed method can make the phase unwrapping for phase-shifting FPP more robust and faster. Experiment result confirms the effectiveness of the proposed method.