Flame detector for monitoring a region adjacent to bodies of water and taking into consideration a degree of polarization present in the received light for the activation of a fire alarm

Abstract

A flame detector, may be aligned to cover a region to be monitored near a body water. The flame detector has at least one radiation sensor and a downstream evaluation unit. The at least one radiation sensor is sensitive to light in the spectrum of open fire. The evaluation unit outputs a fire alarm in the event of fluctuations or flicker frequencies characteristic of open fire being detected. A linear polarizing filter positioned upstream of the radiation sensor(s) has a polarization plane rotated about a main receiving direction to largely suppress the horizontal component of the received light, based on the knowledge that light reflected from water surfaces is predominantly horizontally polarized. If characteristic flicker frequencies and a significant degree of polarization are simultaneously detected in the received light, the detector identifies sunlight reflected off bodies of water and modulated by the swell, and a false alarm output is inhibited.