Method of detecting particles by detecting a variation in scattered radiation
View Patent ↗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.
1. A method of detecting particles, comprising the following steps:
emitting a beam of radiation into a monitored region;
capturing images of the monitored region, having one or more image segments, with an image capture device; and
in a data processor, detecting a variation in scattered radiation in images of the monitored region indicating the presence of the particles,
wherein the location of the particles is determined in accordance with a geometric relationship between the locations of a source of emitted radiation, a direction of the emitted radiation and a point of image detection wherein, the geometric relationship is determined from the images.
2. A method as claimed in claim 1 , further comprising the step of modulating the beam of radiation.
3. A method as claimed in claim 2 , wherein scattered radiation within the zone is represented in one or more segments of a corresponding image, which allows for the location of the particles in the region to be identified.
4. A method of detecting particles according to claim 1 ,
wherein the detected variation is an increase in scattered radiation intensity.
5. A method of detecting particles as claimed in claim 4 ,
wherein the increase is assessed with reference to a threshold value.
6. A method of detecting particles as claimed in claim 5 ,
wherein the threshold value is calculated by averaging integrated intensity values from the images.
7. The method as claimed in claim 5 , further comprising the step of assigning different threshold values for different spatial positions within the region.
8. A method as claimed in claim 1 , further comprising the steps of directing the radiation along a path and identifying a target in the images, the target representing a position at which the radiation is incident on an objective surface within the region.
9. A method as claimed in claim 8 , wherein a location of the target in the images is monitored and the emission of radiation is ceased in response to a change in the location of the target.
10. A method as claimed in claim 1 , further comprising the step of identifying a location of an emitter in the images.
11. A method as claimed in claim 1 , further comprising the step of determining an operating condition of the emitter based on radiation intensity at the identified location of the emitter.
12. A method as claimed in claim 1 , wherein the images are processed as frames which are divided into sections which represent spatial positions within the monitored region.
13. A method as claimed in claim 1 , further comprising the steps of monitoring intensity levels in associated sections of the images and assigning different threshold values for different spatial positions within the region which correspond to the associated sections.
14. Apparatus adapted to detect particles, said apparatus comprising processor means adapted to operate in accordance with a predetermined instruction set, said apparatus, in conjunction with said instruction set, being adapted to perform the method as claimed in claim 1 .
15. A computer program product comprising; a computer usable non-transitory medium having computer readable program code and computer readable system code embodied on said medium for detecting particles within a data processing system, said computer program product comprising; computer readable code within said computer usable medium for performing the method steps of claim 1 .