A general approach to the optical characterization of thin films is developed. A numerical scheme is used to invert sets of optical equations for a stratified medium to solve for the optical constants and thickness of a thin film that is part of the medium. This inversion makes it possible to use any combination of measurements with the required information content. The inversion is essentially exact, and is also used in an error analysis of various optical methods. Several new optical methods involving reflectance and transmittance measurements are described and shown to give improvements in convenience and sensitivity.
Wilford N. Hansen, "Optical characterization of thin films: Theory," J. Opt. Soc. Am. 63, 793-802 (1973)