PARTICLE DETECTION

• US 20110058167A1
• Filed: 11/14/2008
• Published: 03/10/2011
• Est. Priority Date: 11/15/2007
• Status: Active Grant

• Current Assignee: Garrett Thermal Systems Ltd. (Honeywell International Inc.)
• Original Assignee: Xtralis Technologies Ltd (Honeywell International Inc.)
• Inventors: Knox, Ron, Ajay, Kemal, Boettger, Karl
• Granted Patent: US 9,025,144 B2
• Time in Patent Office: Days
• US Class Current: 356/338
• CPC Class Codes: G01N 15/06 Investigating concentration of particle suspensions by weighing G01N5/00; investigating sedimentation of particle suspensions G01N15/04; investigating individual particles G01N15/10
• CPC Class Codes: G01N 15/075 by optical means
• CPC Class Codes: G01N 2015/0693 by optical means, e.g. by integrated nephelometry
• CPC Class Codes: G01N 21/53 within a flowing fluid, e.g. smoke
• CPC Class Codes: G08B 17/125 by using a video camera to detect fire or smoke
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence
• CPC Class Codes: G08B 29/185 Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

A particle detection system (100), such as an active video smoke detection system, includes at least one illumination means (102) for directing a beam (106) of radiation through at least part of the air volume being monitored (110), an image sensor (104) is positioned to capture images of at least part of a beam (106) from illumination means (102); and means to analyse (107) the captured images to detect the presence of particles within the volume. At least 29 different aspects are described for improving the sensitivity, usability, and robustness of particle detection. These include, for example, configuring illumination means (102) to create a curtain of light or a rapidly-scanned beam across the air volume (110), and configuring a reflector to steer or change direction of a beam reflected from illumination means (102).

Claims

1. A particle detection system configured to detect particle in an air volume, said system including:

a primary light source configured to create a curtain of light across at least part of a volume being monitored.

2. A particle detection system as claimed in claim 1 further including:

an image sensor is positioned to capture images of a least part of the curtain of light; and

means to analyse the captured images to detect the presence of particles within the volume on the basis of scattered radiation captured in the images.

3. A particle detection system as claimed in claim 2 wherein the curtain of light is created using optical means to create a divergent beam.

4. A particle detection system as claimed in claim 2 wherein the curtain of light is created by scanning a linear beam across the volume being monitored.

6. A particle detection system as claimed in claim 2 wherein the image sensor is placed in the plane.

5. (canceled)

7. A method of operating an particle detection system at an ambient light level at which would cause saturation of an image sensor of the system at a predetermined aperture size, at a first exposure duration, the method including:

determining a reduced exposure duration which will not cause saturation of the image sensor; and

determining an increased frequency of image capture on the basis of the reduced exposure duration.

8. A method as claimed in claim 7, wherein the exposure time is reduced by a factor of N to avoid saturation, and the image capture frequency is increased by substantially the same factor N.

9. A method as claimed in claim 8 in which the increased frequency of image capture is above 500 images per second.

10-23. -23. (canceled)

24. A particle detection system configured to detect particle in an air volume, the system including:

primary illumination means for directing a beam of radiation across the air volume being monitored,

a primary image sensor is positioned to capture images of a least part of the beam, said primary illumination means and primary image sensor being positioned on non-opposing sides of the volume being monitored;

at least one reflector configured to direct light emitted by the primary light source to a predetermined target position such that the light traverses a path across at least part of the volume being monitored; and

means to analyse the captured images to detect the presence of particles within the volume on the basis of scattered radiation captured in the images.

26. A particle detection system as claimed in claim 24 wherein the primary light source and primary light sensor are located on a same side of the volume being monitored.

27. A particle detection system as claimed in claim 26 wherein the primary light source and primary light sensor are substantially co-located.

29. A particle detection system as claimed claim 27 wherein field of view of the primary light sensor includes at least part of the beam incident on the reflector and the reflected beam.

30. A particle detection system as claimed in claim 29 wherein the field of view of the primary light sensor includes a predetermined target position.

31. A particle detection system as claimed in claim 24 wherein the reflector includes a plurality of reflective surfaces

34. A particle detection system as claimed in claim 24, further including a second light sensor positioned to receive the reflected beam.

25. (canceled)

28. (canceled)

32-33. -33. (canceled)

35-58. -58. (canceled)

59. A method of determining alignment of a beam in an AVSD system, the method including:

emitting a beam of light across a volume being monitored;

scanning the beam of light across a predetermined area;

receiving at least a portion of the beam of light at a light sensor; and

based on at least one measured parameter of the received light determining an alignment of the beam of light.

60. A method as claimed in claim 59 wherein the measured parameter includes any one or more of the following characteristics:

light intensity, spot size, total received irradiance, a light intensity pattern.

61. A method as claimed in claim 59 wherein the method additionally includes:

reflecting at least a portion of the light beam from a reflector, back toward a light sensor such that either the emitted beam or reflected beam traverse the volume being monitored.

63. A method as claimed in claim 61 wherein the method includes the step of:

analysing the light received as a result of scanning of the beam to identify a light reception pattern characteristic of a reflection from a reflector forming part of the AVSD system.

65. A method as claimed in claim 63 wherein the optical characteristics of the reflector include means for forming a detectable pattern in light reflected from the reflector caused by a reflectivity, refraction and/or diffraction characteristic of at least part of the reflector.

68. A method as claimed in claim 59 wherein the step of scanning the beam of light across a predetermined area includes scanning the beam in a predetermined pattern.

72. A method as claimed in claim 68 wherein the pattern includes any one or more of the following patterns;

a linear patter, a raster pattern, a spiral pattern.

73. A method as claimed in claim 72 wherein the method includes on the basis of the determined alignment, changing the alignment of a beam of light emitted by a system so that the beam is aligned in a predetermined manner.

62. (canceled)

64. (canceled)

66-67. -67. (canceled)

69-71. -71. (canceled)

74-190. -190. (canceled)

191. A method of processing a light scattering signal from particle detection system:

receiving a light scattering signal;

identifying a temporary peak in received scattered light intensity in the signal; and

smoothing the temporary increase in received scattered light intensity of the signal.

192. The method as claimed in claim 191 wherein the temporary peak in received scattered light intensity has a size of a predetermined number of pixels when compared to a spatially based average intensity.

194. The method as claimed in claim 191 wherein the temporary peak in received scattered light intensity is has a size of a predetermined number of frames when compared to a time based average intensity.

196. A method as claimed in claim 191 wherein the step of smoothing the spike includes one or more of the following:

clipping the peak,

ignoring the peak;

or

replacing the peak with a predetermined value.

193. (canceled)

195. (canceled)

197-267. -267. (canceled)