Measurement of small angular displacements with a flat-parallel glass plate.

Abstract

A new, simple method is presented for the accurate measurement of small angular displacements. An incident laser diode beam on a flat-parallel glass plate was reflected at the front and the rear surface of the plate, and the interference pattern of two reflected beams was measured with a one-dimensional image sensor and a microcomputer, After the running average of the interference pattern signals was computed numerically to reduce spatial noise on the interference pattern, interference peak positions and angular displacements were estimated. The small angular displacements thus obtained were found to be in approximate agreement with a theory.