"Phase unwrapping error reduction framework for a multiple-wavelength phase-shifting algorithm," Opt. Eng., (2009)

[19] S Zhang, "Phase unwrapping error reduction framework for a multiple-wavelength phase-shifting algorithm," Opt. Eng.,48(10), 105601, 2009 (Accepted without revision); doi:10.1117/1.3251280

We address a framework to reduce the unwrapping errors of the measurement system using a digital multiple-wavelength phaseshifting 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.