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Anti-reflective coating
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<p>An antireflective, antiglare or anti-reflection (AR) coating is a type of <a href="/facts/Optical_coating/pGnrNRn6">optical coating</a> applied to the surface of <a href="/facts/Lens_(optics)/ejlH6n5c">lenses</a>, other optical elements, and <a href="/facts/Photovoltaic_cell/3L814UCC">photovoltaic cells</a> to reduce <a href="/facts/Reflection_(physics)/BhcjDs79">reflection</a>. In typical imaging systems, this improves the efficiency since less <a href="/facts/Light/jeofpMn4">light</a> is lost due to reflection. In complex systems such as <a href="/facts/Camera/j4uqsfJQ">cameras</a>, <a href="/facts/Binoculars/DPHVmKIL">binoculars</a>, <a href="/facts/Telescope/BDwYahhR">telescopes</a>, and <a href="/facts/Optical_microscope/5700vcna">microscopes</a> the reduction in reflections also improves the <a href="/facts/Contrast_(vision)/zD9F91Je">contrast</a> of the image by elimination of <a href="/facts/Stray_light/7TAs3tR4">stray light</a>. This is especially important in <a href="/facts/Planetary_astronomy/ocX6rp0d">planetary astronomy</a>. In other applications, the primary benefit is the elimination of the reflection itself, such as a coating on <a href="/facts/Glasses/ER3sFKmJ">eyeglass</a> lenses that makes the eyes of the wearer more visible to others, or a coating to reduce the glint from a covert viewer's <a href="/facts/Binoculars/DPHVmKIL">binoculars</a> or <a href="/facts/Telescopic_sight/P174A0vB">telescopic sight</a>. </p><p>Many coatings consist of transparent <a href="/facts/Thin-film_optics/lwgIJUwc">thin film</a> structures with alternating layers of contrasting <a href="/facts/Refractive_index/yjkzvgeE">refractive index</a>. Layer thicknesses are chosen to produce <a href="/facts/Destructive_interference/lI5f78I4">destructive interference</a> in the beams reflected from the interfaces, and constructive interference in the corresponding transmitted beams. This makes the structure's performance change with wavelength and <a href="/facts/Angle_of_incidence_(optics)/DTaCjhTU">incident angle</a>, so that color effects often appear at <a href="/facts/Oblique_angle/gFUTEQYq">oblique angles</a>. A <a href="/facts/Wavelength/kcJU0ymz">wavelength</a> range must be specified when designing or ordering such coatings, but good performance can often be achieved for a relatively wide range of <a href="/facts/Frequencies/QUSbPaW8">frequencies</a>: usually a choice of <a href="/facts/Infrared/44XdJNcc">IR</a>, visible, or <a href="/facts/Ultraviolet/kncBUqn5">UV</a> is offered. </p>