The Raman scattering intensity from a polyphenylether fluid film entrapped between a diamond window and a one-inch-diameter steel ball is found to correlate linearly with fluid film thickness over a 0.1 to 10 μm thickness range. The calibration and precision of the technique, as well as comparisons with other methods, are discussed.
Erik J. Hutchinson, Darren Shu, Fred LaPlant, and Dor Ben-Amotz, "Measurement of Fluid Film Thickness on Curved Surfaces by Raman Spectroscopy," Appl. Spectrosc. 49, 1275-1278 (1995)