The effect of misalignment in phase retrieval based on a spatial light modulator

Recently we have proposed the conception of an innovative experimental scheme for phase retrieval from a set of consecutive intensity measurements. It is based on a 4f-optical filter with a reflective phase-only spatial light modulator (SLM) located in the Fourier domain. The main advantage of this scheme is the greatly reduced measurement time since no mechanical shift is required throughout the capturing process. To recover the phase, the captured intensities have been subjected to an iterative process based on generalized projections. Here, we investigate the influence of misalignment, between the optical axes of the setup, on the performance of the iterative scheme's solution. It is demonstrated that if misalignments is present, measurement errors will be propagated in the iterative process and thus affect the accuracy and the rate of convergence of the phase retrieval. The concept is demonstrated by investigating the wavefield diffracted by the U. S. Air Force resolution target. In the case of an aligned setup, it is shown that only 5 planes and 10 iterations give good reconstructions.