AR coating means anti-reflective coating.When light comes into contact with an optical material it is transmitted, reflected and absorbed in varying proportions. The aim of an anti-reflective (AR) coating is to minimize the reflection element and in doing so greatly increase transmission. This is key in applications where high transmission is desirable or where reflection needs to be reduced to prevent stray light affecting other elements of an optical system. Anti-reflective coatings are relatively soft and not suitable for applications where they will be exposed to harsh conditions.