Old rules useful to the designer of optical coatings

Optical coatings are usually composed of multilayer film structures which are used to obtain a desired transmission, reflection and absorption from a surface. The spectral characteristic may be due to the intrinsic property of the material (e.g. metal reflectors) or due to interference effects arising from the multilayer stack. The following is a set of guidelines ("old rules") useful to the designer of optical systems of which coated surfaces are an integral part.