A New Angular Shearing Interferometer for Collimation in the Nanoradian Range

Abstract
A new compact polarization laser angular interferometer for precision collimation of a mirror in the nanoradian range is described with an analytical treatment and an experimental verification of its performance. The phase of the optical fringe is proportional to the angular deflection of the object mirror. The angular shearing in two interfering laser beams modulates its amplitude so sharply that it enables determination of a particular optical fringe out of a number of periodic fringes. Ray tracing and Gaussian beam treatment can describe the mechanism of the modulation and explain the experimental behavior and predict some important features of the interferometer required for other precision applications.