AR coating is the most common used coating in our life . It can be devided into many kinds: Single layer AR coating; laser AR coating; multilayer AR coating; single wavelength AR coating; double wavelength AR coating. Every coating can be used in different ways . AR coating is always used for reducing the reflectivity of the optical surface . As usual, an optical surface has a high reflectivity .We can’t use it as a window unless it is coated with AR coating.The coating make more light go through the surface,thus we can see things more clearly by the glass