Two-shot point-diffraction interferometer with an unknown phase shift

On the basis of a modified Mach-Zehnder interferometer, this paper proposes a two-shot point-diffraction interferometer (PDI), by which two pi-shifted interferograms are created according to the principle of half-wave loss and are simultaneously captured by a single CCD camera. After an arbitrary unknown phase shift is induced, a second and final shot captures these last two patterns. Then a novel algorithm based on statistical principles is developed to extract the actual phase shift and the wavefront phase from four interferograms. The combination of two required shots and a robust algorithm allows the proposed PDI to be implemented efficiently and accurately. Related simulation and experiments are conducted to prove the correctness of the proposed method.