Differential rotationally shearing interferometer: implementation concept

A new type of interferometer, a differential rotationally shearing interferometer, differs from the traditional rotationally shearing interferometer in that the angle of rotation is infinitesimal or, at least, very small. A differential rotationally shearing interferometer may be used for the detection of wavefront asymmetry even when its asymmetry is very small. We present an implementation concept for the differential rotationally shearing interferometer, based on the Mach-Zehnder interferometer. One of the important advantages of the new interferometer is that the polarization problems do not arise do the small angle of rotation between the two wavefronts.