| 摘要 |
PURPOSE: To provide optical parts having excellent resistance against heat and environments and excellent productivity by forming the film comprising a first layer and a second layer from the surface of a substrate and forming the first layer as a high refractive index layer and the second layer as a low refractive index layer. CONSTITUTION: A dielectric film having two layers are formed by vapor deposition on the substrate 1 of an optical part in such a manner that the first layer 2 from the substrate is formed as a high refractive index layer having 1.85-1.95 refractive index and the second layer 3 is formed as a low refractive index layer having 1.45-1.47 refractive index. The optical film thickness d1 , d2 of the first layer 2 and the second layer 3, respectively, satisfy 0.30λ0 /4<=d1 <=0.40λ0 /4 and 1.29λ0 /4<=d2 <=1.34λ0 /4. By designing the layers as above specified, excellent optical performances are obtd. so that the reflectance of the film ranging from 0.16% to 0.84% can be stably reproduced according to the film constitution for the specified designed wavelength. In this method, the first high refractive index layer 2 consists of cerium oxide and the second low refractive index layer 3 consists of silicon oxide. |
