Particle Detector, System and Method

• US 20080297360A1
• Filed: 11/14/2005
• Published: 12/04/2008
• Est. Priority Date: 11/12/2004
• Status: Active Grant

• Current Assignee: Garrett Thermal Systems Ltd. (Honeywell International Inc.)
• Original Assignee: VFS Technologies Ltd.
• Inventors: Knox, Ron, Ajay, Kemal, Boettger, Karl
• Granted Patent: US 8,508,376 B2
• Time in Patent Office: Days
• US Class Current: 340/628
• CPC Class Codes: G01N 15/1433 using image recognition
• CPC Class Codes: G01N 2021/1765 Method using an image detector and processing of image signal
• CPC Class Codes: G01N 21/17 Systems in which incident light is modified in accordance with the properties of the material investigated where the material investigated is optically excited causing a change in wavelength of the incident light G01N21/63
• CPC Class Codes: G01N 21/49 within a body or fluid
• CPC Class Codes: G01N 21/532 with measurement of scattering and transmission
• CPC Class Codes: G01N 2201/06113 Coherent sources; lasers
• CPC Class Codes: G01N 33/0031 comprising two or more sensors, e.g. a sensor array electrochemical electrode arrays G01N27/27
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/95 for meteorological use
• CPC Class Codes: G01S 7/4873 by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/4876 by removing unwanted signals G01S7/495 takes precedence
• CPC Class Codes: G08B 17/103 using a light emitting and receiving device
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/117 by using a detection device for specific gases, e.g. combustion products, produced by the fire G08B17/103, G08B17/11 take precedence
• CPC Class Codes: G08B 17/125 by using a video camera to detect fire or smoke
• CPC Class Codes: G08B 25/10 using wireless transmission systems G08B25/009 takes precedence
• CPC Class Codes: G08B 29/043 of fire detection circuits
• 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: G08B 29/24 Self-calibration, e.g. compensating for environmental drift or ageing of components
• CPC Class Codes: Y02A 90/10 : Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The invention provides use of one or more emitted beams of radiation (16), for example, laser beam(s), in combination with an image capturing means (14), for example, one or more video cameras and/or optical elements to detect particles (30), for example smoke particles, located in an open space (12).

Claims

1. :

A method of detecting particles comprising;

emitting a beam of radiation into a monitored region; and

detecting a variation in images of the region with image capturing means such that the variation in images indicates the presence of the particles,

wherein the steps of emitting and detecting comprise determining an ON period of the beam of radiation and an exposure period of the image capturing means on the basis of a power level of the emitted beam.

2. :

A method as claimed in claim 1 wherein the step of modulating further comprises;

synchronising the ON period of the beam with the exposure period of the image capturing means.

3. :

A method as claimed in claim 2 wherein the ON period of the beam is one of greater than, less than or equal to the exposure period.

4. :

A method as claimed in claim 1 wherein the beam is pulsed.

5. :

A method as claimed in claim 1 further comprising one or more of the following steps;

providing an ON period of the beam in the range of about a few seconds to about 0.1 msecs or less;

providing a corresponding beam power level in the range of about 1.18 mW or less to about 500 mW.

6. :

A method as claimed in claim 1 wherein the image capturing means operates with a frame rate in the range of about 25 to 100 frames per second and the beam is pulsed at a frequency in a range of about 12.5 Hz to about 50 Hz.

12. :

A method as claimed in claim 1

wherein the particles comprise smoke particles.

19. :

A method as claimed in claim 1 wherein the image capturing means comprises one or more image capture devices.

20. :

A method as claimed in claim 1 wherein the image capturing means comprises opposing image capture devices.

21. :

A method as claimed in claim 1 further comprising the steps of;

providing a first beam emitter paired with a first image capture device;

providing a second beam emitter paired with a second image capture device;

monitoring the emitted beam of the first emitter with the second image capture device; and

monitoring the emitted beam of the second emitter with the first image capture device.

22. :

A method as claimed in claim 21 wherein one or more of the first and second paired emitters and image capture devices are provided in one and the same mounting arrangement.

23. :

A method as claimed in claim 22 further comprising the step of;

pre-aligning one or more of the first and second paired emitters and image capture devices.

24. :

A method as claimed in claim 23 wherein the step of pre-aligning comprises;

setting a beam direction of respective emitters such that the beam emerges at a predetermined angle with respect to the centre of view of the corresponding image capture device.

25. :

A method as claimed in claim 24 wherein the predetermined angle is θ

, the distance between respective emitter/image capture device pairs is D metres such that a distance between a target spot of the beam of the first emitter and the second image capture device is given by;

S=D tan θ

34. :

A method as claimed in claim 2 wherein the step of synchronising the emission of the beam of radiation and the image capturing means comprises;

emitting of the beam of radiation at a pre-determined rate;

identifying the radiation source in one or more video images captured by the image capturing means; and

continually modifying the image capturing means frame rate to remain in synchronisation.

35. :

A method as claimed in claim 34 wherein the radiation source is fitted with a secondary light source comprising a wide angle of emission.

36. :

A method as claimed in claim 35 further comprising the step of;

flashing the secondary light source in a predetermined timing relationship with the light source to facilitate locating the source in the image capturing means image.

37. :

A method as claimed in claim 36 wherein the secondary light source flashes in one or more of;

a periodic pattern;

a pseudo-random sequence.

38. :

A method as claimed in claim 36 further comprising the steps of;

providing an image capturing means frame rate that approximates the rate of an oscillator of the light source;

identifying the flashing secondary source;

varying the phase of the image capturing means frame rate to maintain the timing relationship between image capturing means exposures and the light source.

39. :

A method as claimed In any one of claims 34 wherein a frequency of the light source oscillator is altered to be one of;

the same as;

a multiple of;

a sub multiple of an AC mains electricity supply frequency.

45. :

A method as claimed in claim 1 further comprising the steps of;

determining a path loss measurement by recording the intensity of a target incident beam spot of the emitted beam within the captured image and;

comparing the recorded intensity with a recorded intensity at a previous time.

101. :

A method as claimed in claim 1 wherein the ON period of the beam of radiation and an exposure period of the image capturing means is determined in accordance with an indirectly proportional relationship with the power level of the beam.

7-11. -11. (canceled)

13-18. -18. (canceled)

26-33. -33. (canceled)

40-44. -44. (canceled)

46-95. -95. (canceled)

96. :

A system for detecting particles in monitored region, including one or more light sources configured to at least periodically emit a beam of radiation into the monitored region, one or more image capture devices for collecting an image of the region being monitored during an exposure period, an image processor for determining a variation in the images to detect the presence of particles at a plurality of locations within the region wherein at least one of the duration and timing of the emission of the beam into the monitored region and exposure period are determined on the basis of the power level of the emitted beam.

97. :

A system for detecting particles as claimed in claim 96 wherein the emission of the beam is synchronised with the exposure period of the image capturing means.

98. :

A system for detecting particles as claimed in claim 96 wherein the beam is pulsed.

99. :

A system for detecting particles as claimed in claim 96 wherein the duration of emission of the beam into the region is in the range of about a few seconds to about 0.1 msecs or less; and

the corresponding beam power level is in the range of about 1.18 mW or less to about 500 mW.

100. :

A system for detecting particles as claimed in claim 96 wherein the image capturing means operates with a frame rate in the range of about 25 to 100 frames per second and the periodicity of emission of the beam is in a range of about 12.5 Hz to about 50 Hz.