Diferential method for the formation of relative phase shifts between light beams in two-arm interferometer

Abstract

The possibility of improving technical means that make it possible to introduce phase shifts into light beams in the interferometer paths is considered. An optical-mechanical phase modulator in the form of a plane-parallel glass plate rotated around an axis lying in its plane was adopted as the initial version of these technical means. A differential method is proposed for the formation of relative phase shifts between beams in a two-arm interferometer. A variant of the modulator has been developed in the form of a pair of rigidly interconnected plates, the planes of which are initially rotated at a given angle. In this case, each of the parallel light beams in the interferometer passes through its own plate. It is shown that in this case a practically linear relationship is provided between the generated relative phase shift and the total angle of rotation of the plates. A variant of using a single plate as a modulator under the established conditions for the incidence of two beams propagating in different arms of the interferometer is considered. The operability of the proposed differential method for controlling the phase shift between light beams is confi rmed by the data of a test experiment. The results obtained will be useful in the development of special tools based on the method of digital speckle pattern interferometry for measurements of the displacement fields of deformable bodies