PHOTOELECTRONIC TYPE SMOKE DETECTOR OF SCATTERED LIGHT DETECTING TYPE

摘要

PURPOSE:To obtain the same performance without using photodetecting lens, by providing the 1st shield plate shielding unnecessary light from the light source of the smoke detector and the 2nd shield plate shielding unnecessary light produced by it. CONSTITUTION:The 1st shield plate 5A is provided at the location where the unnecessary light from the light source 1 providing the projection lens 2 is not entered to the photodetector 4A. Further, the 2nd shield plate 6 is provided at the location where the unnecessary light produced at the ridge 5A' of the 1st shield plate 5A with reflection and diffraction is not entered to the photodetector 4A. The provision of the two shield plates like this enables to obtain the same S/N and sensitivity as the provision of expensive photo-detecting lens without it.