| 摘要 |
PURPOSE:To enable accurate and correct detection of a specified liquid level without being affected even by the pollution of a light emission surface or the like of a light emitting body and the adhesion of a liquid drop or a liquid film. CONSTITUTION:A photodetecting body 3 is arranged on a light emission body 1 which emits light L from a projector 2 from a horizontal emission surface 1a and an inclined emission surface 1b with a gap G therebetween. The photodetecting body 3 is provided with a first photo detector 4 which receives light regardless of whether the gap is in a liquid or not, a second photo detector 5 which receives light only when the gap G is in the liquid and a third photo detector 6 which receives light only when the gap G is in the air. When a output ratio between the second photo detector 5 and the first photo detector 4 is larger than that between the third photo detector 6 and the first photo detector 4, a liquid level is determined as specified one. |
