A Theoretical Discussion of the Comparative Performances of Dispersion and Fourier-Transform Interferometric Spectrometers for the Infrared Region

Abstract

A summary is given of the theoretical factors that determine the performances of dispersion and Fourier-transform (interferometric) infrared spectrometers in terms of the signal/noise ratio obtainable in relation to the time spent in signal measurement for a given spectral resolution. It is assumed that, as is normal in the infrared region of the spectrum, the performances of the spectrometers are limited by detector noise. “Trading rules” are given relating the spectral resolution to the time of spectral measurement or the signal/noise ratio for each type of instrument. It is shown that, for a given pair of dispersion and interferometric spectrometers, the latter operating with matched-throughput, the relative performance of the interferometer improves by a factor of √2 in signal/noise ratio (or 2 in time) when the resolution interval, Δ, is halved.