Patent ID: 9702803
Date: 2017-07-11
CPC Classifications: G01N,G08B,H04N

Claim:
1. A method in an active video smoke detection (AVSD) system, the AVSD system including: at least one primary light source configured to emit a beam of light across a volume being monitored; an image sensor having a field of view and arranged to capture images of a least part of the beam of light; and means to analyze images captured by the image sensor to detect the presence of particles within the volume on the basis of light scattered from the beam and captured in the images; said method comprising: emitting the beam of light across the volume being monitored at a primary beam position to enable detection of particles within the volume based on the analysis of images captured by the image sensor on the basis of light scattered from the beam at the primary beam position and captured in the images; and determining an intrusion of an object into the field of view of the image sensor such that the object impedes the image sensor's view of the beam in the primary beam position when detecting particles, by (a) scanning a beam of light across a part of the volume being monitored to illuminate a region within the volume that lies between a primary beam position and the image capture means, and (b) analyzing the output of the image sensor to determine whether an object has impinged upon the beam of light emitted in step (a), to identify an object that blocks a line of sight between the image capture means and the beam of light when it is in its primary beam position.