A two steps phase-shifting demodulation method using the VU factorization

•A robust two-steps phase shifting algorithm.•Phase demodulation using only two phase-shifting interferograms.•Two-steps phase-shifting algorithm without fringe pattern normalizarion. In this paper, we present a two steps phase-shifting fringe pattern demodulation method using the VU factorization. Compared with other methods, our proposal is robust to non-constant background illuminations and modulating terms (non-normalized fringes). We use the two given fringe patterns, and from these, we synthetically generate another two images that approach the background illumination in order to obtain a total set of four images. Such set is used in a matrix model that can be factorized using the VU factorization method to determine the modulating phase. Our proposal is able to recover the phase without: 1) known phase shift, 2) normalized fringe patterns, and 3) any special non-linear pre-processing. Tests and results with an important representative diversity of interferograms, taken from different experiments, are shown to demonstrate the feasibility of this method.