Fire detection method and apparatus using overlapping spectral bands
First Claim
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1. A method of monitoring an area for the presence of a fire, comprising:
- sensing radiation within a first spectral band, and within a second spectral band broader than, and overlapping, the first spectral band, each of the spectral bands having long and short cut-off wavelengths, a separation between one of the long cut-off wavelengths of the first and second spectral bands and the short cut-off wavelengths of the first and second spectral bands being less than approximately 50% of a bandwidth of the first spectral band and greater than 0% of the bandwidth of the first spectral band; and
determining from the sensed radiation whether a fire is present in the monitored area.
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Abstract
An optical fire detector employs two or more sensors operating a different spectral bands. The spectral bands are selected to have approximately coincident cut-off wavelengths in order to make the detector'"'"'s ability to positively identify a fire more uniform over its field of view. The use of three overlapping spectral bands provides the detector with enhanced detection capabilities for large, hot fires that behave like black body radiators.
58 Citations
69 Claims
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1. A method of monitoring an area for the presence of a fire, comprising:
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sensing radiation within a first spectral band, and within a second spectral band broader than, and overlapping, the first spectral band, each of the spectral bands having long and short cut-off wavelengths, a separation between one of the long cut-off wavelengths of the first and second spectral bands and the short cut-off wavelengths of the first and second spectral bands being less than approximately 50% of a bandwidth of the first spectral band and greater than 0% of the bandwidth of the first spectral band; and determining from the sensed radiation whether a fire is present in the monitored area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus for detecting a fire in a monitored area, comprising:
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first and second sensors sensitive to radiation in first and second spectral bands respectively, the second spectral band being wider than, and overlapping, each of the spectral bands having long and short cut-off wavelengths, one of the long cut-off wavelengths of the first and second spectral bands and the short cut-off wavelengths of the first and second spectral bands being substantially similar, a separation between the one of the long cut-off wavelengths of the first and second spectral bands and the short cut-off wavelengths of the first and second spectral bands is less than approximately 50% of a bandwidth of the first spectral band and greater than 0% of the bandwidth of the first spectral band; and a processing unit configured to determine the presence of a fire in the monitored area based on signals received from the first and second sensors. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of monitoring for the presence of a fire, comprising:
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monitoring radiation at a plurality of overlapping spectral bands, where one of short cut-off wavelengths of each of the spectral bands and long cut-off wavelengths of each of the spectral bands vary with angle of incidence on a corresponding sensor in an essentially similar manner; and determining the presence of the fire based on relative amounts of radiation in the spectral bands. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. Apparatus for detecting fire in a monitored area, comprising:
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a plurality of sensors sensitive to radiation in corresponding overlapping spectral bands, one of short cut-off wavelengths for each of the spectral bands and long cut-off wavelengths for each of the spectral bands having essentially similar variations with angle of incidence on the corresponding sensor; and a processing unit coupled to the sensors and configured to determine the presence of a fire based on signals received from the plurality of sensors. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. A method of detecting radiation in an area where there is a risk of fire, comprising monitoring radiation at a plurality of overlapping spectral bands, each spectral band having a short and a long cut-off wavelength, one of short and long cut-off wavelength of at least two of the spectral bands varying with angle of incidence on a sensor used to monitor the spectral bands in a substantially similar manner.
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43. A method of detecting radiation in an area where there is a risk of fire, comprising:
monitoring radiation in at least three spectral bands, each of the spectral bands having a short and a long cut-off wavelength, short cut-off wavelengths of first and second spectral bands being essentially similar and long cut-off wavelengths of first and third spectral bands being essentially similar, the first spectral band being narrower than the second and third spectral bands.
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44. A method of monitoring an area for the presence of a fire, comprising:
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sensing radiation within first, second and third spectral bands, the second spectral band broader than, and overlapping, the first spectral band, a long cut-off wavelength of the first spectral band and a long wavelength cut-off of the second spectral band being substantially similar, the third spectral band being broader than, and overlapping, the first spectral band, a short cut-off wavelength of the first spectral band being substantially similar to a short wavelength cut-off wavelength of the third spectral band; and determining from the sensed radiation whether a fire is present in the monitored area. - View Dependent Claims (45, 46, 47, 48, 49, 50)
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51. A method of monitoring an area for the presence of a fire, comprising:
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sensing radiation within first, second and third spectral bands, the second spectral band being broader than, and overlapping, the first spectral band, each of the spectral bands having long and short cut-off wavelengths, one of i) the long cut-off wavelengths of the first and second spectral bands and ii) the short cut-off wavelengths of the first and second spectral bands being substantially similar, the first spectral band having a center wavelength between center wavelengths of the second and third spectral bands; and determining from the sensed radiation whether a fire is present in the monitored area. - View Dependent Claims (52, 53, 54, 55, 56, 57)
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58. Apparatus for detecting a fire in a monitored area, comprising:
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first, second and third sensors sensitive to radiation in first, second and third spectral bands respectively, the second spectral band being wider than the first spectral band, each of the spectral bands having long and short cut-off wavelengths, the long cut-off wavelengths of the first and second spectral bands being substantially similar and the short cut-off wavelengths of the first and third spectral bands being substantially similar; and a processing unit coupled to receive signals from the first, second and third sensors, and to determine the presence of a fire in the monitored area based on the received signals. - View Dependent Claims (59, 60, 61, 62, 63)
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64. Apparatus for detecting a fire in a monitored area, comprising:
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first, second and third sensors sensitive to radiation in first, second and third spectral bands respectively, the second spectral band being wider than, and overlapping the first spectral band, the first spectral band having a center wavelength between center wavelengths of the second and third spectral bands; and a processing unit configured to determine the presence of a fire in the monitored area based on signals received from the first and second sensors. - View Dependent Claims (65, 66, 67, 68, 69)
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Specification