| 摘要 |
PURPOSE:To make it possible to discriminate whether an article is present in water or air without relying on the judgement of a man regardless of water pressure, by using a transparent optical member having an outer surface contacted with the outside and having a refractive index (n) larger than 1,333 being the refractive index of water while allowing light to be incident on said outer surface at a specific angle. CONSTITUTION:When the outer surface 1b of a transparent optical member 1 made of glass or an acrylic resin having a refractive index (n) is present in air, light emitted from a light emitting element 2 straightly advances along the surface 1c of the optical member 1 and is incident on the outer surface 1b at an angle theta1. By setting this incident angle theta1 to a range represented by formula I , the light from the light emitting element 2 is entirely reflected from the surface 1b when the outer surface is contacted with air and incident to a light receiving element 3 from the surface 1d of said member 1. On the other hand, when the outer surface 1b of the optical member 1 is present in water, a part of light is reflected from the surface 1b and the remainder of light is refracted to be diffused into water. Therefore, by discriminating the light receiving amount of the light receiving element 3, it can be discriminated whether a camera is present in air or water. |
