Optical characteristics of thin film coating and measurement of its thickness

Theoretical analysis of the optical characteristics of thin film coatings was carried out. The relations of refractive index, phase change and film thickness were studied. As a result, a new optical method of measuring thickness of thin metallic coatings was developed. Further, the technique can also be used to find the refractive index of the thin film and the phase change of the light beam owing to being reflected from the coating. It is shown that the new method is very accurate for measuring the thin coating thickness. A specimen coating was tested with a polarised laser beam and the measured phase change falls between the reasonable range of 0 and π.