Spatial carrier phase shifting method for the phase recovery from two interferograms with closed fringes

A procedure is developed to recover the phase from two interferograms with a non-constant phase shift between them. This method may find broad applications when environmental disturbances do not allow implementing traditional phase shifting techniques which normally require three or more images. A spatial carrier phase shifting method is implemented to analyze the two measured temporal phase shifted interferometric images. This approach is very fast, avoids the use of fringe normalization techniques, preserves good tolerance against small (lambda/20) or non-constant phase shifts, background and modulation variations and noise as tested in real and simulated data.