Polarization-based phase-shifting method for shape contours

A phase shifting technique of changing polarization state in a Twyman-Green interferometer is presented to measure the shape of the object surface. The wavefronts of the reference beam and object beam are orthogonally polarized. They are resolved by a quarter-wave plate and then detected by a polarizer as an analyzer. Four intensity measurements with phase difference associated with polarization variation are used to obtain interferometric phase corresponding to shape contour.