Broadband Interferometry - A Non-contact Optical Method for Measuring the thickness of Transparent Thin Films and Coatings

Kevin Lifsey

Presented by Ian Bain, Scalar Technologies Ltd.

"Fringe counting” has long been employed to estimate small changes in film thickness. Recent advances in modern optics and electronics have made it possible to automate this and produce a thin film measurement system which is fast, accurate and easy to use. Furthermore by using broad-spectrum (or “white” light) illumination, it is often possible to measure the thickness of several layers of transparent material simultaneously. This paper briefly outlines the theory behind this technique, assesses its accuracy and discusses its areas of application. Finally it addresses the instrument’s suitability as an in-line tool, why it can be used in high solvent concentration (explosive) situations and explains why the line speed is limited today but will shortly be increased.

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