INFRARED ANTI-REFLECTION FILM OF GERMANIUM SUBSTRATE

摘要

PURPOSE:To decrease the absorption of IR rays and to improve durability by providing prescribed films having prescribed refractive indices on the respective layers from the 1st to the 2nd layers. CONSTITUTION:A ZnS film having an intermediate refractive index is disposed on the 1st layer counted from the substrate side, Ge having a high refractive index on the 2nd layer, ZnS having said intermediate refractive index on the 3rd layer, LaF3, BaF2 or MgF2 having a low refractive index on the 4th layer and a ZnS film having said intermediate refractive index on the 5th layer, in the anti- reflection film of a germanium substrate. The respective thicknesses of the 1st layer - the 5th layer designated as d1, d2, d3, d4, d5 and the respective refractive indices designated as n1, n2, n3, n4, n5 are set at n1d1:n2d2: n3d3:n4d4:n5d5= 1:2:4.2:2.5:0.7. The IR anti-reflection film which provides a high effect of preventing reflection of IR rays, permits vapor deposition at a high speed and makes it easy to obtain the vapor-deposited film having high quality is thus obtd.