Dual channel multi-spectrum infrared optical fire and explosion detection system

• US 5,612,676 A
• Filed: 11/16/1993
• Issued: 03/18/1997
• Est. Priority Date: 08/14/1991
• Status: Expired due to Fees

• Current Assignee: Vibro-Meter, Inc. (Parker-Hannifin Corporation)
• Original Assignee: Meggitt Avionics, Inc. (Parker-Hannifin Corporation)
• Inventors: Minott, George L., Plimpton, Jonathan C.
• Primary Examiner(s): TARCZA, THOMAS H
• Assistant Examiner(s): Oda, Christine K.
• Application Number:
  US08/153,801
• Time in Patent Office: 1,218 Days
• Field of Search: 340/578, 340/587, 340/577, 250/338.1, 250/338.3, 250/339.05, 250/339.15, 250/372, 250/554, 250/339.01, 250/340
• US Class Current: 340/578
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
• CPC Class Codes: G08B 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence

Abstract

A fire detection system including two optical sensing channels and signal processing circuitry that processes the two sensing channels'"'"' output signals and generates another output signal when the processed signals are indicative of a fire. The system automatically detects hydrocarbon and certain non-hydrocarbon fueled fires. The first sensing channel simultaneously senses IR radiation in two IR spectral regions having separate and distinct bandwidths and generates a first signal corresponding to incident IR radiation being sensed in at least one of these spectral regions. One bandwidth is selected so the first sensing channel is responsive to the IR radiation emitted by hydrocarbon and/or certain non-hydrocarbon fueled fires and the other bandwidth is selected so the first sensing channel is responsive to IR radiation emitted from hydrocarbon fueled fires. Both bandwidths are selected so the first sensing channel is essentially non-responsive to solar IR radiation. The second sensing channel simultaneously senses IR radiation in three IR spectral regions, defined by separate and distinct bandwidths, and generates a second signal corresponding to the incident IR radiation being sensed in at least one of the these spectral regions. Each second channel spectral region bandwidth is selected so the second sensing channel is responsive to IR radiation emitted by non-fire radiation sources but non-responsive to IR radiation in the first channel spectral regions.

Claims

1. A fire detection system for automatically detecting a fire fueled by at least one of hydrocarbon and certain non-hydrocarbon fuels, the fire detection system having a low incidence of false alarms from incident infrared (IR) radiation emitted by non-fire radiation sources, the fire detection system comprising:

a first optical sensing channel being configured so as to sense IR radiation in at least one IR spectral region and to generate a first signal corresponding to incident IR radiation being sensed in each of said at least one IR spectral region, wherein each of said at least one first sensing channel IR spectral region is defined by a separate and distinct predetermined bandwidth;

wherein the predetermined bandwidth for each of said at least one first sensing channel IR spectral region is selected so said first optical sensing channel is responsive to the incident IR radiation emitted from the fire;

wherein the predetermined bandwidth for each of said at least one first sensing channel IR spectral region is also established so said first optical sensing channel is essentially non-responsive to the incident IR radiation emitted by the sun;

a second optical sensing channel being configured so as to simultaneously sense IR radiation in three IR spectral regions and to generate a second signal corresponding to the incident IR radiation being sensed in each of said second sensing channel IR spectral regions, said second sensing channel IR spectral regions being defined by predetermined bandwidths that are separate and distinct from each other;

wherein the predetermined bandwidth for each of said second sensing channel IR spectral regions is selected such that said second optical sensing channel is responsive to the incident IR radiation emitted by non-fire radiation sources but non-responsive to the incident IR radiation that lies in the predetermined bandwidth for each of said at least one first channel IR spectral region; and

signal processing means both for processing said first and said second signals, respectively of said first and second optical sensing channels, and for generating a fire signal when the processed first and second signals are indicative of a fire.

2. The fire detection system of claim 1, wherein said first optical sensing channel is configured to simultaneously sense IR radiation in two IR spectral regions, a first and a second IR spectral region, each said first and said second spectral regions being defined by separate and distinct predetermined bandwidths, and wherein said first signal being generated corresponds to the incident radiation being sensed in each of said first and said second IR spectral regions so that the fire detection system can automatically detect fires fueled by hydrocarbons and certain non-hydrocarbons;

wherein the predetermined bandwidth for said first IR spectral region is selected such that said first optical sensing channel is both responsive to the incident IR radiation emitted from the fire fueled by hydrocarbons and responsive to the incident IR radiation emitted from the fire fueled by certain non-hydrocarbons;

wherein the predetermined bandwidth for said second IR spectral region is selected such that said first optical sensing channel is responsive to the incident IR radiation emitted from the fire fueled by hydrocarbons; and

wherein said second sensing channel IR spectral regions are non-responsive to the incident IR radiation that lies in the predetermined bandwidths for said first and said second IR spectral regions of said first optical sensing channel.

3. The fire detection system of claim 2, wherein said first optical sensing channel further includes an IR optical dual bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidths for said first and said second IR spectral regions.

4. The fire detection system of claim 3, wherein said second optical sensing channel further includes an IR optical filter means for filtering IR radiation so that only IR radiation lying in the predetermined bandwidths of said second channel IR spectral regions is passed by said IR optical filter means.

5. The fire detection system of claim 3, wherein said second optical channel simultaneously senses IR radiation in a third, a fourth and a fifth IR spectral region and wherein said second signal being generated corresponds to the incident IR radiation being sensed in each of said third, fourth and fifth IR spectral regions.

6. The fire detection system of claim 5, wherein said second optical sensing channel further includes an IR optical triple bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidths for said third, said fourth and said fifth IR spectral regions.

7. The fire detection system of claim 6, wherein the predetermined bandwidth of said third IR spectral region covers a spectral region having wavelengths shorter than said first IR spectral region, wherein the predetermined bandwidth of said fourth IR spectral region covers an IR spectral region disposed between said first and said second IR spectral regions, and wherein the predetermined bandwidth for said fifth IR spectral region covers an IR spectral region having wavelengths longer than said second IR spectral region.

8. The fire detection system of claim 6 wherein said first optical sensing channel further includes a first filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical dual bandpass filter, the predetermined bandwidth of said first filter window is established so that at least IR radiation in both the predetermined bandwidths of said first and said second IR spectral regions is passed, said first filter window being disposed in front of said IR dual bandpass filter;

and

a first IR sensing element disposed behind said IR optical dual bandpass filter, said first IR sensing element being responsive to at least IR radiation in the predetermined bandwidths of said first and said second IR spectral regions and generating a signal proportional to the incident radiation filtered by said first filter window and said IR optical dual bandpass filter and being sensed by said first IR sensing element.

9. The fire detection system of claim 8 wherein said second optical sensing channel further includes a second filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical triple bandpass filter, the predetermined bandwidth of said second filter window being established so that at least IR radiation in the predetermined bandwidths of said third, said fourth and said fifth IR spectral regions is passed, said second filter window being disposed in front of said IR triple bandpass filter;

and

a second IR sensing element disposed behind said IR optical triple bandpass filter, said second IR sensing element being responsive to at least IR radiation in the predetermined bandwidths of said third, said fourth and said fifth IR spectral regions and generating a signal proportional to the incident radiation filtered by said second filter window and said IR optical triple bandpass filter and being sensed by said second IR sensing element.

10. The fire detection system of claim 6, wherein the predetermined bandwidth for said first IR spectral region is centered at 2.9 microns, wherein the predetermined bandwidth for said second IR spectral region is centered at 4.4 microns, wherein the predetermined bandwidth for said third IR spectral region is centered at 2.2 microns, wherein the predetermined bandwidth for said fourth IR spectral region is centered at 3.7 microns, and wherein the predetermined bandwidth for said fifth IR spectral region is centered at 5.7 microns.

11. The fire detection system of claim 10, wherein the predetermined bandwidth for said first filter window is 2.4 microns to 6.4 microns.

12. The fire detection system of claim 11, wherein the predetermined bandwidth for said second filter window is 1.9 microns to 6.4 microns.

13. The fire detection system of claim 9, wherein said first IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, a photovoltaic indium antimonide sensor, and a germanium doped gold IR sensor and wherein said second IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, and a germanium doped gold IR sensor.

14. The fire detection system of claim 9, wherein said first IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.6 microns to 4.75 microns.

15. The fire detection system of claim 9, wherein said second IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.0 microns to 6.4 microns.

16. The fire detection system of claim 10, wherein each of said IR spectral regions is defined by a half-power bandwidth over the range of 0°

to 45°

angle-of-incidence, wherein the half-power bandwidth for said first IR spectral region is 2.6 microns to 3.2 microns, wherein the half-power bandwidth for said second IR spectral region is 4.0 microns to 4.75 microns, wherein the half-power bandwidth for said third IR spectral region is 2.0 microns to 2.3 microns, wherein the half-power bandwidth for said fourth IR spectral region is 3.3 microns to 3.9 microns, and wherein the half-power bandwidth for said fifth IR spectral region is 4.8 microns to 6.4 microns.

17. The fire detection system of claim 2, wherein said signal processing means further includes signal comparing means for comparing said first signal and said second signal to determine the presence of a fire, wherein said signal comparing means determines a fire is present when the ratio of said first signal to said second signal exceeds a predetermined value.

18. The fire detection system of claim 1, wherein said first optical sensing channel senses IR radiation in a first IR spectral region having a predetermined bandwidth and generates said first signal corresponding to the incident radiation being sensed in said first IR spectral region, and wherein said first optical sensing channel further includes an IR optical single bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidth for said first IR spectral region.

19. The fire detection system of claim 18, wherein said second optical sensing channel further includes an IR optical filter means for filtering IR radiation so that only IR radiation lying in the predetermined bandwidths of said second channel IR spectral regions is passed by said IR optical filter means.

20. The fire detection system of claim 18, wherein said second optical channel simultaneously senses IR radiation in a second, third, and fourth IR spectral region and wherein said second signal being generated corresponds to the incident IR radiation being sensed in each of said second, third, and fourth IR spectral regions.

21. The fire detection system of claim 20, wherein said second optical sensing channel further includes an IR optical triple bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidths for said second, said third, and said fourth IR spectral regions.

22. The fire detection system of claim 21 wherein said first optical sensing channel further includes a first filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical single bandpass filter, the predetermined bandwidth of said first filter window is established so that at least IR radiation in the predetermined bandwidth of said first IR spectral region is passed, said first filter window being disposed in front of said IR single bandpass filter;

and

a first IR sensing element disposed behind said IR optical single bandpass filter, said first IR sensing element being responsive to at least IR radiation in the predetermined bandwidth of said first IR spectral region and generating a signal proportional to the incident IR radiation filtered by said first filter window and said IR optical single bandpass filter and being sensed by said first IR sensing element.

23. The fire detection system of claim 22 wherein said second optical sensing channel further includes a second filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical triple bandpass filter, the predetermined bandwidth of said second filter window is established so that at least IR radiation in the predetermined bandwidths of said second, said third, and said fourth IR spectral regions is passed, said second filter window being disposed in front of said IR triple bandpass filter;

and

a second IR sensing element disposed behind said IR optical triple bandpass filter, said second IR sensing element being responsive to at least IR radiation in the predetermined bandwidths of said second, said third, and said fourth IR spectral regions and generating a signal proportional to the incident radiation filtered by said second filter window and said IR optical triple bandpass filter and being sensed by said second IR sensing element.

24. The fire detection system of claim 23, wherein said first IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, a photovoltaic indium antimonide sensor, and a germanium doped gold IR sensor and wherein said second IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, and a germanium doped gold IR sensor.

25. The fire detection system of claim 23, wherein said first IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 4.0 microns to 4.75 microns and wherein said second IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.0 microns to 6.4 microns.

26. The fire detection system of claim 23, wherein said first IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.6 microns to 3.2 microns and wherein said second IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.0 microns to 6.4 microns.

27. The fire detection system of claim 23, wherein the predetermined bandwidth for said first filter window is 3.5 microns to 6.4 microns and wherein the predetermined bandwidth for said second filter window is 1.9 microns to 6.4 microns.

28. The fire detection system of claim 23, wherein the predetermined bandwidth for said first filter window is 2.4 microns to 6.4 microns and wherein the predetermined bandwidth for said second filter window is 1.9 microns to 6.4 microns.

29. The fire detection system of claim 21, wherein the predetermined bandwidth for said first IR spectral region is centered at 4.4 microns, wherein the predetermined bandwidth for said second IR spectral region is centered at 2.2 microns, wherein the predetermined bandwidth for said third IR spectral region is centered at 3.7 microns, and wherein the predetermined bandwidth for said fourth IR spectral region is centered at 5.7 microns so the system automatically detects hydrocarbon fueled fires.

30. The fire detection system of claim 29, wherein each of said IR spectral regions is defined by a half-power bandwidth over the range of 0°

to 45°

angle-of-incidence, wherein the half-power bandwidth for said first IR spectral region is 4.0 microns to 4.75 microns, wherein the half-power bandwidth for said second IR spectral region is 2.0 microns to 2.3 microns, wherein the half-power bandwidth for said third IR spectral region is 3.3 microns to 3.9 microns, and wherein the half-power bandwidth for said fourth IR spectral region is 4.8 microns to 6.4 microns.

31. The fire detection system of claim 21, wherein the predetermined bandwidth for said first IR spectral region is centered at 2.9 microns, wherein the predetermined bandwidth for said second IR spectral region is centered at 2.2 microns, wherein the predetermined bandwidth for said third IR spectral region is centered at 3.7 microns, and wherein the predetermined bandwidth for said fourth IR spectral region is centered at 5.7 microns so the system automatically detects at least certain non-hydrocarbon fueled fires.

32. The fire detection system of claim 31, wherein each of said IR spectral regions is defined by a half-power bandwidth over the range of 0°

to 45°

angle-of-incidence, wherein the half-power bandwidth for said first IR spectral region is 2.6 microns to 3.2 microns, wherein the half-power bandwidth for said second IR spectral region is 2.0 microns to 2.3 microns, wherein the half-power bandwidth for said third IR spectral region is 3.3 microns to 3.9 microns, and wherein the half-power bandwidth for said fourth IR spectral region is 4.8 microns to 6.4 microns.

33. The fire detection system of claim 18, wherein said signal processing means further includes signal comparing means for comparing said first signal and said second signal to determine the presence of a fire, wherein said signal comparing means determines the fire is present when the ratio of said first signal to said second signal exceeds a predetermined value.

34. A fire detection system for automatically detecting fires fueled by hydrocarbons and certain non-hydrocarbons, the fire detection system having a low incidence of false alarms from incident infrared (IR) radiation emitted by non-fire radiation sources, the fire detection system comprising:

a first optical sensing channel being configured so as to simultaneously sense IR radiation in both a first IR spectral region and a second IR spectral region and to generate a first signal corresponding to incident IR radiation being sensed in each of said first and said second IR spectral regions, said first and said second spectral regions being defined by predetermined bandwidths that are separate and distinct from each other;

wherein said first optical sensing channel further includes an IR optical dual bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidths for said first and said second IR spectral regions;

wherein the predetermined bandwidth for said first IR spectral region is selected such that said first optical sensing channel is both responsive to the incident IR radiation emitted from the fires fueled by the hydrocarbons and responsive to the incident IR radiation emitted from the fires fueled by the certain non-hydrocarbons;

wherein the predetermined bandwidth for said second IR spectral region is selected such that said first optical sensing channel is responsive to the incident IR radiation emitted from the fires fueled by the hydrocarbons;

wherein the predetermined bandwidths of said first and said second spectral regions are also selected so said first optical sensing channel is essentially non-responsive to the incident IR radiation emitted by the sun;

a second optical sensing channel being configured so as to simultaneously sense IR radiation in a third, a fourth and a fifth IR spectral region and to generate a second signal corresponding to the incident IR radiation being sensed in each of said third, said fourth and said fifth IR spectral regions, said third, said fourth and said fifth IR spectral regions being defined by predetermined bandwidths that are separate and distinct from each other;

wherein said second optical sensing channel further includes an IR optical triple bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidths for said third, said fourth and said fifth IR spectral regions;

wherein the predetermined bandwidth for said third, said fourth and said fifth IR spectral regions is selected such that said second optical sensing channel is responsive to the incident radiation emitted by non-fire radiation sources but non-responsive to the incident IR radiation that lies in the predetermined bandwidths for said first and said second spectral regions; and

signal processing means both for processing said first and said second signal and for generating a fire signal when the processed first and second signals are indicative of a fire.

35. The fire detection system of claim 34, wherein the predetermined bandwidth of said third spectral region covers an IR spectral region having wavelengths shorter than said first IR spectral region, wherein the predetermined bandwidth of said fourth IR spectral region covers an IR spectral region disposed between said first and said second IR spectral regions, and wherein the predetermined bandwidth for said fifth IR spectral region covers an IR spectral region having wavelengths longer than said second IR spectral region.

36. The fire detection system of claim 34 wherein said first optical sensing channel further includes a first filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical dual bandpass filter, the predetermined bandwidth of said first filter window is established so that at least IR radiation in both the predetermined bandwidths of said first and said second IR spectral regions is passed, said first filter window being disposed in front of said IR dual bandpass filter;

and

a first IR sensing element disposed behind said IR optical dual bandpass filter, said first IR sensing element being responsive to at least IR radiation in the predetermined bandwidths of said first and said second IR spectral regions and generating a signal proportional to the incident radiation filtered by said first filter window and said IR optical dual bandpass filter and being sensed by said first IR sensing element.

37. The fire detection system of claim 36 wherein said second optical sensing channel further includes a second filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical triple bandpass filter, the predetermined bandwidth of said second filter window is established so that at least IR radiation in the predetermined bandwidths of said third, said fourth and said fifth IR spectral regions is passed, said second filter window being disposed in front of said IR triple bandpass filter;

and

a second IR sensing element disposed behind said IR optical triple bandpass filter, said second IR sensing element being responsive to at least IR radiation in the predetermined bandwidths of said third, said fourth and said fifth IR spectral regions and generating a signal proportional to the incident radiation filtered by said second filter window and said IR optical triple bandpass filter and being sensed by said second IR sensing element.

38. The fire detection system of claim 37, wherein the predetermined bandwidth for said first filter window is 2.4 microns to 6.4 microns and wherein the predetermined bandwidth for said second filter window is 1.9 microns to 6.4 microns.

39. The fire detection system of claim 37, wherein said first IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, a photovoltaic indium antimonide sensor, and a germanium doped gold IR sensor and wherein said second IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, and a germanium doped gold IR sensor.

40. The fire detection system of claim 37, wherein said first IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.6 microns to 4.75 microns and wherein said second IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.0 microns to 6.4 microns.

41. The fire detection system of claim 34, wherein the predetermined bandwidth for said first IR spectral region is centered at 2.9 microns, wherein the predetermined bandwidth for said second IR spectral region is centered at 4.4 microns, wherein the predetermined bandwidth for said third IR spectral region is centered at 2.2 microns, wherein the predetermined bandwidth for said fourth IR spectral region is centered at 3.7 microns, and wherein the predetermined bandwidth for said fifth IR spectral region is centered at 5.7 microns.

42. The fire detection system of claim 41, wherein each of said IR spectral regions is defined by a half-power bandwidth over the range of 0°

to 45°

angle-of-incidence, wherein the half-power bandwidth for said first IR spectral region is 2.6 microns to 3.2 microns, wherein the half-power bandwidth for said second IR spectral region is 4.0 microns to 4.75 microns, wherein the half-power bandwidth for said third IR spectral region is 2.0 microns to 2.3 microns, wherein the half-power bandwidth for said fourth IR spectral region is 3.3 microns to 3.9 microns, and wherein the half-power bandwidth for said fifth IR spectral region is 4.8 microns to 6.4 microns.

43. The fire detection system of claim 34, wherein said signal processing means further includes signal comparing means for comparing said first signal and said second signal to determine the presence of a fire, wherein said signal comparing means determines a fire is present when the ratio of said first signal to said second signal exceeds a predetermined value.

44. A fire detection system for automatically detecting fires fueled by one of a number of prespecified fire sources, the fire detection system having a low incidence of false alarms from incident infrared (IR) radiation emitted by non-fire radiation sources, the fire detection system comprising:

a first optical sensing channel being configured so as to sense IR radiation in a first IR spectral region, being defined by a predetermined bandwidth, and to generate a first signal corresponding to incident IR radiation being sensed in said first IR spectral region;

wherein the predetermined bandwidth for said first IR spectral region is selected so said first optical sensing channel is responsive to the incident IR radiation emitted from the fires fueled by the one of the number of prespecified fire sources;

wherein the predetermined bandwidth of said first IR spectral region is also established so said first optical sensing channel is essentially non-responsive to the incident IR radiation emitted by the sun;

a second optical sensing channel being configured so as to simultaneously sense IR radiation in at least two IR spectral regions and to generate a second signal corresponding to the incident IR radiation being sensed in each of said at least two second sensing channel IR spectral regions, said second sensing channel IR spectral regions being defined by predetermined bandwidths that are separate and distinct from each other;

wherein the predetermined bandwidth for each of said at least two second sensing channel IR spectral regions is selected such that said second optical sensing channel is responsive to the incident IR radiation emitted by non-fire radiation sources but non-responsive to the incident IR radiation that lies in the predetermined bandwidth for said first IR spectral region; and

signal processing means both for processing said first and said second signals, respectively of said first and second optical sensing channels, and for generating a fire signal when the processed first and second signals are indicative of a fire.

45. The fire detection system of claim 44, wherein said first optical sensing channel further includes an IR optical single bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidth for said first IR spectral region.

46. The fire detection system of claim 45, wherein said second optical sensing channel further includes an IR optical filter means for filtering IR radiation so that only IR radiation lying in the predetermined bandwidths of said at least two second channel IR spectral regions is passed by said IR optical filter means.

47. The fire detection system of claim 45, wherein said second optical channel simultaneously senses IR radiation in two IR spectral regions, a second and third IR spectral region, and wherein said second signal being generated corresponds to the incident IR radiation being sensed in each of said second and third IR spectral regions.

48. The fire detection system of claim 47, wherein said second optical sensing channel further includes an IR optical dual bandpass filter being tuned to pass IR radiation that lies in the predetermined bandwidths for said second and said third IR spectral regions.

49. The fire detection system of claim 48 wherein said first optical sensing channel further includes a first filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical single bandpass filter, the predetermined bandwidth of said first filter window is established so that at least IR radiation in the predetermined bandwidth of said first IR spectral region is passed, said first filter window being disposed in front of said IR single bandpass filter;

and

a first IR sensing element disposed behind said IR optical single bandpass filter, said first IR sensing element being responsive to at least IR radiation in the predetermined bandwidth of said first IR spectral region and generating a signal proportional to the incident IR radiation filtered by said first filter window and said IR optical single bandpass filter and being sensed by said first IR sensing element.

50. The fire detection system of claim 49 wherein said second optical sensing channel further includes a second filter window that filters the incident IR radiation emitted by the fire and the non-fire radiation sources so only a predetermined bandwidth of the incident IR radiation passes through to said IR optical dual bandpass filter, the predetermined bandwidth of said second filter window is established so that at least IR radiation in the predetermined bandwidths of said second and said third IR spectral regions is passed, said second filter window being disposed in front of said IR dual bandpass filter;

and

a second IR sensing element disposed behind said IR optical dual bandpass filter, said second IR sensing element being responsive to at least IR radiation in the predetermined bandwidths of said second and said third IR spectral regions and generating a signal proportional to the incident IR radiation filtered by said second filter window and said IR optical dual bandpass filter and being sensed by said second IR sensing element.

51. The fire detection system of claim 50, wherein the predetermined bandwidth for said first filter window is 3.5 microns to 6.4 microns and wherein the predetermined bandwidth for said second filter window is 3.25 microns to 6.4 microns.

52. The fire detection system of claim 50, wherein the predetermined bandwidth for said first filter window is 2.4 microns to 6.4 microns and wherein the predetermined bandwidth for said second filter window is 1.9 microns to 6.4 microns.

53. The fire detection system of claim 50, wherein said first IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, a photovoltaic indium antimonide sensor, and a germanium doped gold IR sensor and wherein said second IR sensing element is selected from a group consisting of a thin film thermopile sensor, a pyroelectric sensor, a photoconductive lead selenide sensor, a photovoltaic mercury cadmium telluride sensor, and a germanium doped gold IR sensor.

54. The fire detection system of claim 50, wherein said first IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 4.0 microns to 4.75 microns and wherein said second IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 3.3 microns to 6.4 microns.

55. The fire detection system of claim 50, wherein said first IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.6 microns to 3.2 microns and wherein said second IR sensing element is an IR sensor that has an unfiltered response which includes at least the spectral region of 2.0 microns to 3.9 microns.

56. The fire detection system of claim 48, wherein the prespecified fire source is hydrocarbons and wherein the predetermined bandwidth for said first IR spectral region is centered at 4.4 microns, wherein the predetermined bandwidth for said second IR spectral region is centered at 3.7 microns, and wherein the predetermined bandwidth for said third IR spectral region is centered at 5.7 microns.

57. The fire detection system of claim 56, wherein each of said IR spectral regions is defined by a half-power bandwidth over the range of 0°

to 45°

angle-of-incidence, wherein the half-power bandwidth for said first IR spectral region is 4.0 microns to 4.75 microns, wherein the half-power bandwidth for said second IR spectral region is 3.3 microns to 3.9 microns, and wherein the half-power bandwidth for said third IR spectral region is 4.8 microns to 6.4 microns.

58. The fire detection system of claim 48, wherein the prespecified fire source is certain non-hydrocarbons and wherein the predetermined bandwidth for said first IR spectral region is centered at 2.9 microns, wherein the predetermined bandwidth for said second IR spectral region is centered at 2.2 microns, and wherein the predetermined bandwidth for said third IR spectral region is centered at 3.7 microns.

59. The fire detection system of claim 58, wherein each of said IR spectral regions is defined by a half-power bandwidth over the range of 0°

to 45°

angle-of-incidence, wherein the half-power bandwidth for said first IR spectral region is 2.6 microns to 3.2 microns, wherein the half-power bandwidth for said second IR spectral region is 2.0 microns to 2.3 microns, and wherein the half-power bandwidth for said third IR spectral region is 3.3 microns to 3.9 microns.

60. The fire detection system of claim 48, wherein said signal processing means further includes signal comparing means for comparing said first signal and said second signal to determine the presence of a fire, wherein said signal comparing means determines a fire is present when the ratio of said first signal to said second signal exceeds a predetermined value.

61. A fire detection system for automatically detecting fires fueled by one of a number of prespecified fire sources including hydrocarbons and certain non-hydrocarbons, the fire detection system having a low incidence of false alarms from incident infrared (IR) radiation emitted by non-fire radiation sources, the fire detection system comprising:

a first optical sensing channel being configured so as to sense IR radiation in at least one IR spectral region and to generate a first signal corresponding to incident IR radiation being sensed in each of said at least one IR spectral region, wherein each of said at least one first sensing channel IR spectral region is defined by a separate and distinct predetermined bandwidth;

wherein the predetermined bandwidth for each of said at least one first sensing channel IR spectral region is selected so said first optical sensing channel is responsive to the incident IR radiation emitted from the fires fueled by the one of the number of prespecified fire sources;

wherein the predetermined bandwidth for each of said at least one first sensing channel IR spectral region is also established so said first optical sensing channel is essentially non-responsive to the incident IR radiation emitted by the sun;

a second optical sensing channel being configured so as to simultaneously sense IR radiation in at least two IR spectral regions and to generate a second signal corresponding to the incident IR radiation being sensed in each of said second sensing channel IR spectral regions, each of said at least two second sensing channel IR spectral regions being defined by predetermined bandwidths that are separate and distinct from each other;

wherein the predetermined bandwidth for each of said at least two second sensing channel IR spectral regions is selected such that said second optical sensing channel is responsive to the incident radiation emitted by non-fire radiation sources but non-responsive to the incident IR radiation that lies in the predetermined bandwidth for each of said at least one first sensing channel IR spectral region; and

signal processing means both for processing said first and said second signals, respectively of said first and second optical sensing channels, and for generating a fire signal when the processed first and second signals are indicative of a fire.