Anti-reflective coating (English: Anti-reflective coating, AR) is a surface optical coating that increases transmittance by reducing light reflection. In complex optical systems, it can improve contrast by reducing scattered light in the system.

Many coatings include transparent film structures with different refractive indices. The thickness of the film determines the wavelength of the reflected light that it acts on. When light is reflected twice on the AR coating, it will interfere with the original reflected light, thereby weakening the reflected light. According to the conservation of energy, the energy of light does not change. Therefore, when the reflected light decreases, the transmitted light increases. This is the principle of AR coating. Generally, when choosing an AR coating, you need to determine the wavelength, such as infrared, visible and ultraviolet.