Grating shearing interferometer with variable shear and fringe orientation

Abstract

A lateral shear interferometer using Ronchi rulings, spatial filtering, and moire technique is described. Two gratings of different spatial frequency are placed on opposite sides of the focus of the beam under test. First diffraction orders of the first grid after being diffracted at the second grating and subsequent spatial filtering form the carrier frequency lateral shear interferogram. It is visualized using the moire fringe technique which simultaneously provides arbitrary reference fringe orientation and number. The experimental verification of principles is given.