High-Speed, Direct Recording Fabry-Perot Interferometer

Abstract

A direct recording Fabry‐Perot interferometer is described which has a high optical speed and provides a direct tracing of spectral line shapes on a linear scale. A photomultiplier views the center spot of the interference pattern. The output of the photomultiplier goes to a vibrating‐reed electrometer and then to a pen recorder. The wavelength of the light at the center of the interference pattern is made to vary with time by changing the index of refraction between the interferometer plates. This is accomplished by enclosing the plates in a gas‐tight housing and admitting an inert gas such as argon or helium to the housing. By the proper choice of gas and of the rate of pressure change, one obtains the desired rate of tracing the line shape. Orders of magnitude reduction in ``exposure'' time are achieved by eliminating the use of photographic plates.