Why is the AR coating of sunglass lenses so important?
The opinion is often voiced that an AR coating is not required for sunglass lenses because reflections are not allegedly noticed due to the tint. In actual fact, reflections on coloured lenses are considerably more irritating for both the wearer and anyone looking at him than on clear lenses. The relationship of unwanted light to usable light makes this clear: In an uncoated, clear lens with the refractive index 1.525, the relationship of unwanted light to usable light is approx. 9%; in an uncoated sunglass lens it is as much as approx. 19.7% (internal transmittance = 23%). The darker the lens, the more disturbing the reflections. Every sunglass lens should therefore be supplied with an AR coating. History Not only contraction of the pupils, but also closing of the eyelids protect the eyes against glare and UV radiation. This realisation probably led to what is known as “slit spectacles”. These wooden spectacles worn by Eskimos are one of the earliest forms of sun protection. Their nar
