Thin films play a critical role in our lives as they are used, for example, in electronics, solar cells and coatings on eyeglasses in order to reduce glare and increase the amount of transmitted light through the lenses. For example, anti-reflection (AR) coatings are applied to lenses in order to reduce glare that would otherwise be present in uncoated lenses. This has become an attractive feature for many consumers and, therefore, measurement and control of AR coatings has become increasingly important.
Figure 1 shows two reflectance spectra of ophthalmic lenses. The black spectrum is the reflectance spectrum of a lens that contains a hard coating as well as an AR coating, whereas the red spectrum is a lens that only has a hard coating.