A SMALL LAMELLAR GRATING INTERFEROMETER FOR VERY FAR-INFRAPED

This paper describes the construction and performance of a lamellar grating interferometer designed for routine spectroscopy in the 3-80 cm-1 spectral region, which differs from other lamellar grating interferometers recently described in the literature due to its considerably reduced size-8 cm dia. optics-and the fact that it utilises a room temperature infrared detector rather than a detector operating at liquid helium temperature. A number of solid, liquid and gaseous absorption spectra are presented, to demonstrate the versatility, operating range and high resolution capability (0.1-0.2 cm-1) of this instrument when used with Golay infrared detectors. The interferometer's performance has been assessed using gratings of different period and comparative tests were made with a Michelson interferometer of similar size optics. The lamellar grating interferometer was found to give a better performance at frequencies <25 cm-1 than the Michelson interferometer. © 1969.