Iteratively correcting algorithm for suppressing temporal variations in phase-shifting interferometry

In this paper, we introduce an iterative correcting algorithm for phase demodulation in optical metrology via phase-shifting interferometry. The scheme can effectively cope with interferograms with both temporal intensity variations and non-uniformly spaced phase shifts. When the background intensity and fringe visibility vary only over time while spatially remaining constants, our approach can iteratively estimate and correct them. For each iteration, we propose retrieving the phase shifts and the temporal variations, and then we extract the phase map from the corrected interferograms. We provide the spectral analysis of the method according to the frequency transfer function (FTF) formalism for phase-shifting algorithms. Results show that our scheme can accurately retrieve the phase map where the demodulation errors are unintelligible. Additionally, our method has computational time comparable to state-of-the-art iterative algorithms for non-uniformly phase-shifted interferograms, converging rapidly within ten iterations.