| 摘要 |
PURPOSE:To make a detector of tobacco smoke small in size, and to raise the photodetecting efficiency by providing a photodetector for photodetecting directly light of a light emitting elements, between the light emitting element and a scattered light photodetector by smoke. CONSTITUTION:A holder 6 is provided in a case 4, a light emitting element 1 of a photodiode is provided on its one end, and a scattered light photodetector 2 is provided on the other end. Also, a direct photodetector 3 is provided between the light emitting element 1 and the scattered light photodetector 2, and its optical axis is turned to an optical axis of the light emitting element 1. In this state, when tobacco smoke goes in from a gap 7 of the case 4, a light emitted from the light emitting element 1 is scattered by the smoke, and photodetected by the photodetector 2. In this case, the photodetector 3 photodetects the light directly, and the smoke is detected from a difference in the photodetecting quantity between the photodetector 2 and 3. Also, when an angle theta at which the optical axis of the light emitting element 1 and the optical axis of the photodetector 2 cross is made small, the large scattered light by smoke can be detected. Accordingly, the device is made compact since the light emitting element and the scattered light photodetector are provided on both ends around the direct photodetector. |
