Sunglasses anti reflection

A common problem with sunglasses is back glare, which is caused by the reflection of light onto the back of the lens and back into your eyes. The function of anti reflective protective coating is to reduce the reflection of light by the lens. Like the scratch resistant protective layer, the anti reflective coating is a strong and thin film layer on the lens. The refractive index of the anti reflective coating material is between air and glass. This makes the intensity of the reflected light on the inner and outer surfaces of the film almost equal. When the thickness of the film is about a quarter of the wavelength of light waves, the light reflected from the inner and outer surfaces of the film will cancel out each other through destructive interference, thereby minimizing the glare you see. Anti reflective coatings are also applied to the front surface of refractive contact lenses and some sunglasses to eliminate the "hotspots" caused by the strong light reflected by the lenses.