| 摘要 |
PROBLEM TO BE SOLVED: To reduce the influence on a measurement result due to waterdrops formed from a condensed water vapor and attached to a surface of an optical element facing a gas duct, after driving over a long time. SOLUTION: A photocatalyst TiO<SB>2</SB>layer 23 is applied to a surface, exposed to a space which is connected to the gas duct of a collimating lens 8, a reflection plate 14 and a reflecting mirror 10. Light sources 24a, 24b, 26, 28a, 28b are provided in the vicinity of the collimating lens 8, the reflecting plate 14 and the reflecting mirror 10 and turned to the surfaces of these, so as to irradiate an ultraviolet light. Water vapor, attached to the surfaces on the gas duct side of the collimating lens 8, the reflecting plate 14 and the reflecting mirror 10, will not turn into waterdrops, but will turn into a thin film by the action of the photocatalyst layer 23. COPYRIGHT: (C)2005,JPO&NCIPI
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