| 摘要 |
PROBLEM TO BE SOLVED: To provide an infrared ray cut filter which has a transmittance of 90% or more in the transmission band of wavelength 430 to 600 nm, can minimize a space in the optical axis direction and hardly causes warping even when a multilayer film is formed on a substrate. SOLUTION: The infrared ray cut filter comprises the multilayer film, which is made by alternately laminating transparent thin film consisting of high refractive index material and transparent thin film consisting of low refractive index material plural times and is formed on a transparent base plate, has a transmission band of wavelength≥430 nm and≤600 nm and a non-transmission band of wavelength≥750 nm and≤1,050 nm and has such a transmittance characteristic that the transmittance of wavelength region interposed between the transmission band and the non-transmission band is gradually reduced from the transmission band side toward the non-transmission band. Therein, an alumina thin film layer is formed on a principal plane of the transparent base plate, the transparent thin film consisting of the high refractive index material and the transparent thin film consisting of the low refractive index material are alternately disposed in order from the transparent substrate side and the final layer consists of the low refractive index material. COPYRIGHT: (C)2006,JPO&NCIPI
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