| 摘要 |
PURPOSE:To introduce fine particles near the end of an optical transmission line and prevent the entry of noise light and coarse objects from the outside by providing an optical transmission holding case near the end of the optical transmission line of a photoelectric type fine particle detector. CONSTITUTION:An optical fiber 22 leads the light 21 from a light source into an optical transmission line holding case 26 and an optical fiber 24 receives the light radiated from the end of the optical fiber 22 and is fixed together with the optical fiber 22 to the case 26. When smoke 25 enters the case 26, the transmitted light 23 having been attenuated by the smoke is led from the end of the optical fiber 24 into the fiber and reaches a photo detector, by which the existence of the smoke is detected. Whereupon, screen-form outlet and inlet 28 are provided to the case 26, by which the entry of coarse objects may be prevented. In addition, light shield plates 27 are provided near the outlet and inlet 28, and therefore external light which becomes noise may be prevented. |
