| 摘要 |
The infrared optical filter of the present invention comprises a substrate formed of an infrared transmitting material and a plurality of filter parts arranged side by side on one surface side of the substrate. Each filter part includes: a first λ/4 multilayer film in which two kinds of thin films having mutually different refractive indices but an identical optical film thickness are alternately stacked; a second λ/4 multilayer film in which the two kinds of thin films are alternately stacked, said second λ/4 multilayer film being formed on the opposite side of the first λ/4 multilayer film from the substrate side, and; and a wavelength selection layer interposed between the first λ/4 multilayer film and the second λ/4 multilayer film, said wavelength selection layer having an optical film thickness different from the optical film thickness of each the thin film according to a desired selection wavelength. A low refractive index material of the first λ/4 multilayer film and the second λ/4 multilayer film is an oxide, and a high refractive index material thereof is a semiconductor material of Ge. A material of the wavelength selection layer is identical to a material of the second thin film from the top of the first λ/4 multilayer film. |
