Photoelectric smoke detector with expanded visual field

摘要

A thin-type photoelectric smoke detector which is less susceptible to the effect of disturbance light noise, contamination of a smoke detecting unit, etc., and which ensures high sensitivity for the optical detection characteristic of the smoke detecting section. In the photoelectric smoke detector of the type in which infrared light is irradiated into a flat smoke detecting chamber and the scattered light of the irradiated infrared light due to smoke entering into the smoke detecting chamber is detected by a light-sensing element, there are provided optical members for expanding the visual field of the light-sensing element to a flat visual field corresponding to the cross-sectional shape of the smoke detecting chamber.