Optical flame detection system and method

• US 7,541,938 B1
• Filed: 03/29/2007
• Issued: 06/02/2009
• Est. Priority Date: 03/29/2006
• Status: Active Grant

• Current Assignee: University of Alabama (University of Alabama System)
• Original Assignee: Darell Eugene Engelhaupt
• Inventors: Engelhaupt, Darell Eugene
• Primary Examiner(s): Wu; Daniel
• Assistant Examiner(s): Fan; Hongmin
• Application Number:
  US11/729,653
• Time in Patent Office: 796 Days
• Field of Search: 340/600, 340/577, 340/578, 250/544, 250/339.15, 356/213, 356/218, 356/229, 356335-337
• 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

Abstract

A long range optical sensor and system for detecting the flame of forest fires or other fires while rejecting false alarms due to solar radiation is described. The sensor utilizes a collector optic that collects energy from a wide field of view and concentrates the energy onto a detector. The collector may be a non-imaging collector and may match to a non-planar sensor. In one embodiment the sensor may be arrayed to achieve larger area coverage. In another, the sensor system may be scanned to increase the encompassed viewing area. Larger areas may be covered by RF radio links or networks interconnecting multiple arrayed sensor modules. UVC reflective coatings may include enhanced aluminum with silicon dioxide, silicon monoxide, or magnesium fluoride, or high phosphorous nickel phosphorous. In one embodiment a UVC sensitive Geiger Mueller tube may be coupled to a non-imaging spherical reflective collector. A catadioptric UVC/infra-red flame sensor is disclosed. Refractive or reflective designs are considered.

Claims

1. An enhanced flame detector for detecting flame in environments where the sun may come within a field of view of the enhanced flame detector, comprising:

an optical detector sensitive to the ultraviolet C range and insensitive to ultraviolet A and ultraviolet B; and

a concentrator for collecting energy from a flame and directing said energy to said optical detector, said concentrator having a reflecting surface that is reflective for ultraviolet C, said concentrator providing a concentration ratio greater than 1;

wherein the concentrator is a non-imaging concentrator having an axis of symmetry of said concentrator, and the detector is substantially cylindrical with a cylindrical axis of symmetry, said detector receiving said energy from said flame through a side of said detector, said side parallel to said cylindrical axis of symmetry, and said concentrator spreads said energy across at least one dimension of said optical detector so that heating from the sun is spread across said at least one dimension of said optical detector when the sun is within said field of view of said enhanced flame detector.

2. The enhanced flame detector of claim 1, wherein the concentrator is spherical, ellipsoidal, or hyperboloidal.

3. The enhanced flame detector of claim 1, wherein the detector is a Geiger Mueller tube.

4. The enhanced flame detector of claim 1, wherein said cylindrical axis of symmetry of said optical detector is oriented parallel to said axis of symmetry of said concentrator.

5. The enhanced flame detector of claim 1, wherein the concentrator shape is based on a conic section curve and the detector has a length dimension disposed collinear with said axis of symmetry of said concentrator.

6. The enhanced flame detector of claim 1, wherein the concentrator is based on rotation of a conic section about said axis of symmetry of said concentrator, said detector is mounted with the cylindrical axis of symmetry parallel to said axis of symmetry of said concentrator for enhanced radial viewing angle while maintaining higher collection efficiencies.

7. The enhanced flame detector of claim 1, further including a cover enclosing a space within said concentrator, said cover comprising a material transparent to ultraviolet C, said cover for protection of said concentrator from contamination.

8. A method for detecting a flame with a flame detector in environments where the sun may come within a field of view of said flame detector, said flame detector comprising a concentrator and a sensor, said method comprising:

collecting and concentrating ultraviolet C energy from said flame by said concentrator to produce concentrated energy;

said concentrator having an axis of symmetry, said concentrator having a reflecting surface that is reflective for ultraviolet C;

directing said concentrated energy to said sensor;

wherein the concentrated energy is distributed along a length dimension of said sensor, said detector being characterized substantially by said length dimension and a diameter dimension;

said sensor receiving said energy from said flame through a side of said sensor, said side parallel to said length dimension of said sensor; and

said concentrator spreads said energy across said length dimension of said sensor so that heating from the sun is spread across said length dimension of said sensor when the sun is within said field of view of said flame detector, and

placing said detector with said length dimension collinear to said axis of symmetry of said concentrator.

9. An enhanced flame detector for detecting flame in environments where the sun may come within a field of view of the enhanced flame detector, comprising:

an optical detector sensitive to the ultraviolet C range and insensitive to ultraviolet A and ultraviolet B; and

a concentrator for collecting energy from a flame and directing said energy to said optical detector, said concentrator having a reflecting surface that is reflective for ultraviolet C, said concentrator providing a concentration ratio greater than 1; and

said concentrator spreads said energy across at least one dimension of said optical detector so that heating from the sun is spread across said at least one dimension of said optical detector when the sun is within said field of view of said enhanced flame detector,

wherein the concentrator is a spherical concentrator, said spherical concentrator defined by a sphere;

said optical detector having a substantially cylindrical shape, said cylindrical shape having a cylindrical axis of symmetry, wherein said optical detector is oriented with said cylindrical axis of symmetry perpendicular to a plane tangent to said sphere defining said spherical mirror;

said detector receiving said energy from said flame through a side of said detector, said side parallel to said cylindrical axis of symmetry.

10. The enhanced flame detector of claim 9, wherein the optical detector is a Geiger Mueller tube.