The Michelson interferometer may be used to measure the separation between two parallel surfaces which are distant from the interferometer. A beam of light incident normal to these surfaces must be at least partially reflected back to the interferometer by each surface in order for the technique to work. The results of three measurements using this technique are described, and the effect of dispersion is discussed.
R. A. Patten, "Michelson Interferometer as a Remote Gauge," Appl. Opt. 10, 2717-2721 (1971)