Interferometers vs Monochromators: Separating the Optical and Digital Advantages

Fourier transform (FT) and grating infrared spectrophotometers are compared from a theoretical viewpoint in terms of the multiplex advantage of FT spectrometers, the relative optical throughputs, the comparative performance of the detectors used with each type of system, and other more minor parameters. The signal/noise ratios of spectra measured using commercial FT and grating spectrophotometers are compared. The relative performance varies with wavenumber in the manner forecast theoretically, although the experimental performance of the FT spectrometer is slightly worse than we predicted. Optimum applications for each type of instrument are discussed in terms of these results.