| 摘要 |
PROBLEM TO BE SOLVED: To obtain a level sensor which can detect a level without using a prism, by a method wherein a filler as a transparent liquid or a transparent solid whose refractive index is nearly equal to the refractive index of a tubular case is filled into an optical path to a light-receiving element from a light- emitting element. SOLUTION: The inside space (especially the optical path L to a light- receiving element 2B from a light-emitting element 2A) of a tubular case 1 is filled with a material 3 whose refractive index is larger than the air and whose refractive index is close to that of the tubular case 1. Thereby, the angle of incidence of light on the outside 1A of the tubular case 1 can be set at a critical angle or higher. A photointerruptor 2 which is composed of the light- emitting element 2A and of the light-receiving element 2B is installed at the inside of the tubular case 1, and the filler 3 is filled into the optical path L to the light-receiving element 2B from the light-emitting element 2A. As a result, a level can be detected without using a prism. In addition, when the incident state of light on the light-receiving element 2B at the photointerruptor 3 is monitored, levels in a plurality of places can be detected without using a prism. |
