Multiple-Beam Interferometry: Intensity Distribution in the Reflected System

Abstract

The intensity distribution within the reflected fringe system from a multiple-beam interferometer employing silvered reflecting surfaces is discussed in its dependence upon the reflectivities and phase conditions at the reflecting surfaces. Using the Fizeau fringes of equal thickness localized on the zero order Feussner surface, the reflected intensity distribution is examined experimentally as the reflection coefficients of the interferometer surfaces vary between 4% and 90%. In the range of low reflectivities, when the silverings used showed marked colours, the changes in the reflected system lead to the measurement of a phase quantity related to the optical constants of the silver in the form of the thin film. Also in this range, the reflected fringes have a symmetrical form which is of use in the examination of sources of low intensity. In the range of high reflectivities, the conditions for the use of the reflected fringes in topographical investigation are discussed. The findings apply to fringes of equal chromatic order as well as to Fizeau fringes in reflection.