| 摘要 |
PURPOSE:To form an inexpensive polygonal prism with an optical interference filter by vapor-depositing an optical interference filter directly on side faces of a polygonal prism. CONSTITUTION:Optical interference filters 8 and 9 are vapor-deposited directly on two of side faces of a pentagonal prism 7. Those optical interference filters 8 and 9 consists of at least two kinds of layers among a layer material with a low refractive index, a layer of material with a high refractive material, and a layer of material with a refractive index between 1 and the refractive index of the high-refractive-index material. The optical interference filter 8 transmits light with wavelength lambda1 and reflects light with wavelength lambda2 and the optical interference filter 9, on the other hand, reflects the light with the wavelength lambda1 and transmits the light with the wavelength lambda2. Further, a reflection preventive film 10 which prevents both light beams with the wavelengths lambda1 and lambda2 is vapor-deposited directly on the incidence surface of the pentagonal prism 7.
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