Double-passed two-beam interferometers. II. Effects of specimen absorption and finite path difference

Abstract

Expressions are obtained in this paper for the irradiance distribution in the fringe systems in double-passed Jamin and Twyman-Green interferometers with an absorbing specimen in one of the paths. Expressions are also obtained in the latter case for the effects of the spectral coherence of the source, the degree of collimation of the incident beam, and the wedge angle of the virtual air film in which interference takes place, on the irradiance distribution in the fringe pattern obtained with an appreciable optical path difference. The theoretical loss in setting accuracy in the various cases, as well as the corrections to be applied to obtain the true optical path difference are evaluated.