PHASE EFFECTS IN POLYCHROMATIC INTERFEROMETERS.

Abstract

Interferometry is indispensable in optical metrology. Since interferometry constitutes a phase measurement, the measured values are highly degenerate and derived results are ambiguous unless special measures are taken. Although there is much useful information within the constraints of these ambiguities, it is often desirable or necessary to minimize them. Monochromatic sources provide long useful measurement ranges but also have the most ambiguity. The ambiguities can often be reduced by going to polychromatic sources to obtain an extra degree of freedom in the measurement system. There are also other reasons one might want to go to polychromatic interferometers such as source brightness, availability, or snr. Today there is a move towards multilayer, thin-film coatings in components because of their versatility. We examine some typical thin-film devices for their effects on a polychromatic interferometer.