Anti-reflection coatings

摘要

An anti-reflection coating (20) for a transparent or semi-transparent substrate comprising a first layer (26) adjacent to the substrate (22) having a refractive index greater than about 1.9; a second layer (28) comprising silicon dioxide or silicon dioxide doped with less than 20% of another material; a third layer (30) having a refractive index greater than about 2.1 and an optical thickness less than lambda 0/4, where lambda 0 is the central wavelength of the anti-reflection coating and is in the range 420 to 1600 nm; and a fourth layer (32) comprising silicon dioxide or silicon dioxide doped with less than 20% of another material.