Noise-equivalent change in radiance for misalignment noise in a double-sided interferogram.

Engineers designing optical alignment servo systems for Michelson interferometers and Fourier-transform infrared spectrometers need to predict the amount of noise expected from the small and randomly varying amounts of misalignment that occur as the servo attempts to maintain alignment while taking data. A formula is derived for the noise-equivalent change in radiance due to this effect and the formula's accuracy is demonstrated by comparison of its predictions to the errors found in simulated interferometer measurements contaminated by misalignment noise.

Noise-equivalent change in radiance for sampling noise in a double-sided interferogram.

The formula for the noise-equivalent change in radiance (NEdN) for sampling noise [Appl. Opt. 38, 139 (1999)] can work well when applied to the double-sided interferograms of radiance spectra dominated by isolated emission lines, but it does not work well when applied to broad, slowly varying radiance spectra such as a Planck blackbody curve.