An antireflective, antiglare or anti-reflection (AR) coating is a type of optical coating applied to the surface of lenses, other optical elements, and photovoltaic cells to reduce reflection. In typical imaging systems, this improves the efficiency since less light is lost due to reflection. In complex systems such as cameras, binoculars, telescopes, and microscopes the reduction in reflections also improves the contrast of the image by elimination of stray light. This is especially important in planetary astronomy. In other applications, the primary benefit is the elimination of the reflection itself, such as a coating on eyeglass lenses that makes the eyes of the wearer more visible to others, or a coating to reduce the glint from a covert viewer's binoculars or telescopic sight.
Uncoated glasses lens (top) versus lens with anti-reflective coating. The reflection from the coated lens is tinted because the coating works better at some wavelengths than others.
Anti-reflective coatings are often used in camera lenses, giving lens elements distinctive colors. Such colors indicate the wavelength of visible light least affected by the antireflective properties of the coating. A variety of colors can be produced whose precise hue depends entirely on the thickness of the coating. Color or cast can change radically when the coating is increased or decreased in thickness by tens of nanometers.
An unmetallised heterojunction solar cell precursor. The blue colour arises from the dual-purpose indium tin oxide anti-reflective coating, which also enhances emitter conduction.
An anti-reflection coated window, shown at a 45° and a 0° angle of incidence
An optical coating is one or more thin layers of material deposited on an optical component such as a lens, prism or mirror, which alters the way in which the optic reflects and transmits light. These coatings have become a key technology in the field of optics. One type of optical coating is an anti-reflective coating, which reduces unwanted reflections from surfaces, and is commonly used on spectacle and camera lenses. Another type is the high-reflector coating, which can be used to produce mirrors that reflect greater than 99.99% of the light that falls on them. More complex optical coatings exhibit high reflection over some range of wavelengths, and anti-reflection over another range, allowing the production of dichroic thin-film filters.
Optically coated mirrors and lenses
Comparison of uncoated glasses (top) and glasses with an anti-reflective coating (bottom).
A woman wears sunglasses featuring a highly reflective optical coating
