The thicknesses of UO2 films from 100 Å to 1800 Å on uranium substrates were determined from reflectance measurements in the visible region. The reflectance measurements on the U-UO2 system were analyzed by two different methods to determine film thicknesses. In the first method, film thicknesses were determined by comparing theoretical reflectance calculations with the experimental reflectance measurements. In the second method, film thicknesses were determined by obtaining the best match of the clorimetric properties (wavelength, excitation purity, and luminous reflectance) of the sample with the colorimetric properties of a predetermined film thickness calibration curve.
D. T. Larson, L. A. Lott, and D. L. Cash, "Surface Film Thickness Determination by Reflectance Measurements," Appl. Opt. 12, 1271-1275 (1973)