Common-path interferometer with four simultaneous phase-shifted interferograms using ronchi grating and cube beamsplitter

• Four interferograms with similar fringe visibility are recorded in one exposure.
• The setup is built using a 4f optical system with simple optical elements.
• The common path configuration makes the setup more stabile and repeatable.
• Experiments are done to show the validity and stability of the proposed method.

A common-path interferometer is built using a 4f optical system with a ronchi ruling used as a spatial filter and a cubic beamsplitter used as an interferogram duplicator. The input aperture is divided into two windows to support the orthogonal circular polarized reference and object beams. Four phase shifted interferograms modulated by polarizing filter array can be captured simultaneously in the output plane. Because the four interferograms have the same fringe visibility, a standard four step algorithm can be used to reconstruct the phase of a sample. The validity and stability of the proposed interferometer in achieving four simultaneous phase-shifted interferograms is proved through experiments.