Lateral shearing interferometer using phase shifting technique without moving element

A simple phase shifting (PS) technique without moving element in lateral shearing (LS) interferometer is presented. This method uses Murty's simple LS interferometer with an wedge plate and adds only two identical transmission gratings. The two gratings can make three (or odd number of) equally separated identical test wavefronts. The wedge plate changes the optical path difference between the original wavefront and the sheared wavefront along the wedge direction. So three (or odd number of) interferograms having different phase shift quantity can be obtained simultaneously and 3-step PS interferometry algorithm can be applied.