coating of lenses

coating of lenses

The deposition of one or more thin uniform transparent coatings on lens surfaces, usually by vacuum evaporation or other electronic techniques; these coatings reduce the amount of scattered light resulting from reflection at each refracting surface, say the interfaces between air and lens and between lens and air. A bloomed lens is coated with a single film of suitable refractive index and thickness: destructive interference can then occur between light reflected from the coating-air surface and light reflected from the lens-coating surface. Multilayer coating depends on thin-film interference. Using up to 30 layers of controlled thickness, extremely low levels of reflected light can be achieved. Multilayer coating can also be used to produce very high levels of reflection from a mirror.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006