GB1264461A - - Google Patents

Abstract

1,264,461. Anti-reflection coatings. BRITISH SCIENTIFIC INSTRUMENT RESEARCH ASSOCIATION. Feb.24, 1969 [Dec.20, 19671, No.57957/67. Heading G2J. A three layer anti-reflection coating has substantially zero reflectance at two wavelengths # 0 and # 0 ' wherein the thicknesses of the three layers are related by the equations where g 1 , g 2 and g 3 represent the normalized phase thicknesses of the first, second and third layers respectively, the first layer being in contact with the substrate and are given by g 1 = 2#n 1 d 1 /# 0 , p 1 (# 0 ) represents the phase change through the first layer at wavelength # 0 , p 3 (# 0 ) represents the phase change through the third layer at wavelength # 0 , p 1 (# 0 ') represents the phase change through the first layer at wavelength # 0 ', p 3 (# 0 ') represents the phase change through the third layer at wavelength # 0 ' and where no, n 1 , n 2 , n 3 and n < being the refractive indices of the substrate, the first, second and third layers and the incident medium respectively and d 1 , d 2 and d 3 are the physical thicknesses of the first, second and third layers respectively. The substrate may comprise glass, the first layer may be made by co-depositing titanium monoxide and silicon monoxide in an oxidizing atmosphere, the second layer may comprise neodymium oxide, ceric oxide, titanium dioxide or zinc sulphide, and the third layer may comprise magnesium fluoride. The layers may be deposited on a substrate by vacuum deposition.