| 摘要 |
PURPOSE:To enable the detection of a liquid especially water drops with excellent selectivity by optical method, by projecting two luminous fluxes into a transparent medium at a different incident angles from the side opposite to a detecting surface to compare changes in intensity of reflected light detected with a light receiving element. CONSTITUTION:Light emitting elements 21 and 22 are arranged on an inner surface 1b opposite to a detecting surface 1a of a transparent medium 1 while light receiving elements 31 and 32 are arranged at a fixed angle. Moreover, light emitted from the light emitting elements 21 and 22 as a light source are introduced into the transparent medium 1 at a different angle with a prism 4 optically bonded on the inner surface 1b of the transparent medium. A incident light propagating through the transparent medium 1 by total reflection is led out of the transparent medium 1 through a prism 5 optically bonded on the inner surface 1b to irradiate light receiving elements 31 and 32. The intensity of the detection light with the light receiving elements 31 and 32 is outputted as electrical signal and compared with a comparator circuit to detect presence of water (rain drops or the like). |
