| 摘要 |
PURPOSE:To set an apparatus freely at a location other than a front window as well, by connecting a sensor section varying in the quantity of transmission light with difference in refractive index from that of a water drop to at least one of light emitting and receiving elements with an optical fiber. CONSTITUTION:A light guide-shaped sensor section 51 made of a transparent resin is provided on a back part of the like of a door mirror 4 and one side thereof is exposed outside. An optical fiber 52 is made to face one end of the sensor section 51 optically while a light emitting element 54 such as LED faces the other end of the optical fiber 52 within a thermostatic box 58. An optical fiber 53 is made to face the other end of the sensor section 51 and a light receiving element 55 such as photo diode is arranged in the thermostatic box 58. This enables the arranging of the apparatus at a location without blocking the field of view of crew. In addition, both the elements 54 and 55 are set near an air-conditioning equipment thereby achieving a higher temperature stability.
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