| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical thin film body which does not cause the interference of light like conventional techniques but has extremely little absorption of light. SOLUTION: A holding thin film 2 made of tantalum pentaoxide is formed on a substrate 1 made of silicon dioxide. The holding thin film 2 has a lead-cut wedge-like cross section as shown in the figure, and an optical thin film 3 having specified optical characteristics is formed by alternately depositing silicon dioxide and tantalum pentaoxide with the interfaces of the layers parallel to the upper face of the holding thin film 2. By forming the holding thin film to have the lead-out wedge-like cross section, the propagation direction of the light reflected on the interface between the optical thin film 3 and the holding thin film 2 differs from the propagation direction of the light reflected on the back face of the holding thin film 2 (the lower side in the figure) and therefore, the beams do not interface with each other. The substrate 1 hardly influences the optical characteristics. Because the holding thin film 2 is made thin, it hardly attenuates light.
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