Monitoring of optical coatings

Abstract

Monitoring implies the measurement and control of the parameters of optical thin films during deposition with the object of ensuring the production of an acceptable coating. Monitoring techniques usually concentrate on film thickness as the most important parameter. The principal monitoring arrangements in current use are surveyed with a brief account of their relative merits. It is shown that they are less able to cope with refractive-index errors than with simple thickness errors and that tight control of material parameters is required to take advantage of recent advances in monitoring techniques.