| 摘要 |
PROBLEM TO BE SOLVED: To prevent light transmission characteristics from lowering due to exposure to ultraviolet rays by providing a constitution in which ultraviolet cut-off filters are provided for both incident and emergent end faces of an optical fiber in such a way as to be opposed to the infrared incident plane of the optical fiber. SOLUTION: An infrared detector is formed of a fiber cord 12, an infrared detecting element 17, and an arithmetic processing circuit. The fiber cord 12 seats an optical fiber 13 formed of material based on silver halide housed in a metallic protective tube 15. Ultraviolet cut-off filters 16a and 16b opposed to the end faces of the optical fiber 13 are fitted into both end faces of the protective tube 15. When the plane of incidence of the fiber cord 12 is directed to an object to be measured 7, infrared rays from the object to be measured 7 are transmitted through the ultraviolet cut-off filter 16a, become incident onto the optical fiber 13, are transmitted through the ultraviolet cut-off filter 16b on the emergent side, and are received by the infrared detecting element 17. The arithmetic processing circuit computes the temperature of the object to be measured 7 by the output from the infrared detecting element 17 and displays it on a display part.
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