A method is described in which a Fabry-Perot interferometer is used to measure the thickness of uniform thin films to an accuracy of ±15A. The separation of the D-lines of sodium light is used as a standard of length. The method is evaluated by comparison with other methods and in terms of its applications and limitations.
L. G. SCHULZ, "An Interferometric Method for Accurate Thickness Measurements of Thin Evaporated Films," J. Opt. Soc. Am. 40, 690-692 (1950)