Double-Passed Two-Beam Interferometers

Abstract

When the rays emerging from a conventional two-beam interferometer are reflected back through the instrument, fringes similar in appearance and behavior to three-beam fringes are obtained. Extremely accurate measurements are possible with the help of these fringes, using a photometric setting criterion. The mode of formation of these fringes, as well as the theoretical intensity distribution in them under various conditions, are discussed.