| 摘要 |
PURPOSE:To easily detect whether liquid is present or not by making light incident on the boundary surface on a liquid side below a critical angle, and detecting reflected light from the boundary surface by a photodetecting element. CONSTITUTION:A boundary surface 5 is formed of a solid body 3 and an air layer on the transparent solid body 3 at the side of a light emitting element 1 and the photodetecting element 2, and a boundary surface 6 is formed of the transparent solid body 3 and air on the transparent solid body 3 at the side of liquid. Part of light which is emitted by the light emitting element 1 and arrives at the boundary surface 5 is refracted and transmitted in the transparent solid body 3 to reach the other boundary surface 6, by which part of it is reflected to reach the photodetecting element 2 through the boundary surface. When the liquid which varies in amount contacts the transparent solid body 3, the quantity of reflected light on the boundary surface 6 varies and the quantity of light reaching the photodetecting element 2 varies. Consequently, it is judged easily whether the liquid is present or not from the output of the photodetecting element 2. |
