Method of detecting particles by detecting a variation in scattered radiation

摘要

A smoke detecting method which uses a beam of radiation such as a laser (16), to monitor a region, such as a room (12). A camera (14) is used to capture images of part of the room (12), including a path of the laser beam. Particles in the laser beam scatter light (30), and this is captured by the camera (14) for analysis. A processor (20) extracts data relating to the scattered light (30) to determine the density of particles in the beam, to determine the level of smoke in the region. The laser may have a modulated output (38) so that images captured without the laser tuned “on” can be used as a reference point and compared to images taken with the laser turned “on”, to assist in determining the level of scattered light (30) compared to ambient light. Filters (24, 26) may be used to decrease signals generated from background light.

主权项

1. A method of detecting smoke within a monitored region:
directing a beam of radiation across the monitored region; capturing images of monitored region, including at least part of a path of the beam of radiation through the region; analizing the captured images to determine the presence of smoke on the basis of an increase in light scattered from the beam; integrating intensity values from the images; determining individual smoke levels for a respective plurality of portions of the monitored region using the integrated intensity values and different thresholds for each portion, each of the smoke levels being based on an increase in light scattered from a portion of the beam within a corresponding portion of the monitored region.