Classical Optical Filters

Abstract

As was demonstrated in section 2.3 of this book, the reflectance from an air/glass (or a glass/air) boundary is about 4% through the visible wavelength range at normal incidence. Hence, each glass optical element (lenses, waveplates, etc.) working at transmission mode is responsible for at least 8% of the losses in transmitted power. The situation is even worse for optical elements made of higher refractive index materials. Therefore, the total transmittance of even relatively simple optical systems can be quite low. In addition, light reflected from the various surfaces in the optical system can (and usually does) reach the focal plane, which leads to the degradation of optical system performance. To solve these problems, antireflection coatings are used. Antireflection coating is usually understood to be the coating of the optical surface minimizes the reflection from the surface at some angles of incidence over a specified wavelength range.