| 摘要 |
PURPOSE:To prevent characteristics such as transmissivity and reflectivity from deteriorating even if there is the formation variance and wavelength shift of a two-wavelength separation filter by forming dielectric material layer which have a high refractive index as odd-numbered layers and a low refractive index as even-numbered layer, shifting the optical film thickness of a specific high- refractive index layer from 1/4 of designed reference wavelength lambda0, and setting other respective layers to l0/4. CONSTITUTION:Thirty nine dielectric material layers which are made of TiO2 as with the high refractive index as the odd-numbered layers and SiO2 with the low refractive index as the even-numbered layers are laminated on a prism 1 alternately. When the designed optical film thickness is lambda0, the optical film thickness of 1st and 39th layers is 1.29lambda0/4, the optical film thickness of 3rd and 37th layers about 1.17lambda0/4, the optical film thickness of the 7th and 33th layers 1.06lambda0/4, and the optical film thickness of other layers lambda0/4. Consequently, the two-wavelength separation filter is obtained which has a steep rising characteristic from a reflection band to a transmission band and excellent transmission efficiency while a ripple in the transmission band is reduced.
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