| 摘要 |
Light emitted from a light emitting element (1) is converted into parallel light by a lens (2), and a light receiving element (4) detects scattered light occurring due to particulate existent in a fan-shaped field pattern spreading along the optical path of the parallel light. Since parallel light is used, stray light can be processed within a limited space. Furthermore, since the scattered light of parallel light which occurs due to the particulate is detected using the fan-shaped field pattern, particulate detection can be performed on volumes of air at a high signal-to-noise ratio. A further improvement is achieved by providing a light trap (7) comprising reflection planes for further minimizing stray light and noise. In a still further improvement, an air inlet (8) and an air outlet (9) are arranged oppositely, forming a passage of air, the light source being arranged in the vicinity of the inlet and the light receiver in the vicinity of the outlet, so that the air passage is overlapping the optical path, thereby concentrating scattering particles in the optical path. |
