Advanced Thin Film Measurement System. Thickness, refractive index and extinction coefficient are measured quickly and easily with the F20 advanced spectrometry system. Spectral analysis of reflections from the top and bottom of the thin-film provides thickness and optical constants (n and k) in seconds. Measurement Range: Thickness 100 angstroms to 50 micrometers, Optical Constants 1000 angstroms to 10 micrometers. Thickness Accuracy: +/- 1 nm at 500 nm thickness. Precision: 0.1 nm. Repeatability: 0.07 nm.