An interferometer can be used to measure infrared spectra. The instrument has no slits, and therefore has a relatively high light-gathering ability. It is also not necessary to disperse polychromatic radiation. The signal-to-noise ratio obtained is consequently high and can be further increased by multiple scanning and coherent addition of information, so that a highly sensitive instrument is available for the measurement of infrared spectra. The interference spectrometer is particularly well suited for the examination of infrared radiation of very low intensity, and has been used to measure infrared absorption, reflection, and emission spectra of a wide variety of materials. Some examples of applications are presented and discussed, including the measurement of infrared emission spectra of minerals and rock specimens and the analysis of the effluent stream of a gas chromatograph.
M. J. D. Low, "Applications of Multiple-Scan Interferometry to the Measurement of Infrared Spectra," Appl. Spectrosc. 22, 463-471 (1968)