We address a framework to reduce the unwrapping errors of the measurement system using a digital multiple-wavelength phase-shifting algorithm. In particular, the following framework is proposed: (1) smooth the raw phase by smoothing the sine and cosine images of the phase computation of the inverse tangent function; (2) locate and remove the incorrectly unwrapped points by the monotonicity condition of the phase map; (3) obtain the unwrapped phase map for the shortest wavelength without smoothing; (4) detect holes and fill them to preserve as much useful information as possible. Experiments demonstrated that the proposed framework significantly alleviated the measurement errors caused by the phase noise.
Song Zhang, Song Zhang,
"Phase unwrapping error reduction framework for a multiple-wavelength phase-shifting algorithm," Optical Engineering 48(10), 105601 (1 October 2009). https://doi.org/10.1117/1.3251280