ABSTRACT
It is only rarely that thin-film filters or coatings are used by themselves. They usually form part of an optical system, and it is in integrating coatings into such systems where many problems appear. There is an unfortunate tendency to leave coatings until late in the design process and some of the most severe problems occur during the attempted integration of coatings once the remainder of the design has been frozen. Such problems could frequently have been avoided had the incorporation of coatings been studied at a time when there was still some design flexibility.
