| 摘要 |
PURPOSE:To steepen the rise of a transmittance characteristics and to remarkably improve the transmittance in a transmission band and reflectivity in a reflection band by forming a titled filter into a 40-layered structure by using a high refractive index material and low refractive index material and forming a specific film constitution. CONSTITUTION:A substrate material is one of flint glass and has about 1.66 refractive index. The 40-layered 2-wavelength sepn. filter consisting of the high refractive index material TiO2 and the low refractive index material SiO2 is formed on said substrate. The TiO2 is formed as the layers of the odd numbers counted from the substrate and the SiO2 as the layers of the even numbers in the film constitution. The optical film thicknesses of the respective layers are so determined that the optical film thicknesses of the 3rd layer, 8th layer, 14th layer, 20th layer, 26th layer, 32nd layer and 37th layer are about lambda0/2 and the rest are lambda0/4 when the design wavelength is designated as lambda0. The rise characteristic is thereby steeped and the two-wavelength sepn. filter which is improved in the reflectivity and transmittance in the use wavelength band is obtd.
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