Infrared sniper detection enhancement

• US 5,686,889 A
• Filed: 05/20/1996
• Issued: 11/11/1997
• Est. Priority Date: 05/20/1996
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Hillis, David B.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US08/668,607
• Time in Patent Office: 540 Days
• Field of Search: 340/540, 340/600, 250/330, 250/339.05, 250/339.14, 250/339.15, 250/342, 250/395
• US Class Current: 340/540
• CPC Class Codes: F41G 3/147 based on detection of a firing weapon
• CPC Class Codes: G01S 3/7864 T.V. type tracking systems

Abstract

Firing of small arms results in a muzzle flash that produces a distinctiveignature conducive to automated or machine-aided detection with an IR (infrared) imager. The muzzle flash is intense and abrupt in the 3 to 5 μm band. A sniper detection system operating in the 3 to 5 μm region must deal with the potential problem of false alarms from solar clutter. The invention reduces the false alarm rate of an IR based muzzle flash or bullet tracking system (during day time) by adding a visible light (standard video) camera. The standard video camera helps detect (and then discount) potential sources of false alarm caused by solar clutter. If a flash is detected in both the IR and the visible spectrum at the same time, then the flash is most probably the result of solar clutter from a moving object. If a flash is detected only in the IR, then it is most probably a true weapon firing event.

Claims

1. A method for reducing the false alarm rate of an infrared detection system comprising:

detecting infrared radiation in a first field of view and producing a first signal indicative thereof;

detecting humanly visible light in a second field of view and producing a second signal indicative thereof;

comparing the first signal to the second signal;

and

declaring a positive detection, if the first signal is large compared to the second signal.

2. The method of claim 1, wherein the step of detecting infrared radiation includes detecting infrared radiation in the 3 to 5 micron range.

3. The method of claim 2, wherein the first and second signals include video signals and further comprising filtering the signals at least one of temporally and spatially.

4. The method of claim 3, wherein the second field of view includes the first field of view.

5. The method of claim 1, further comprising the step of physically boresighting an infrared detector and a humanly visible light detector.

6. The method of claim 1, further comprising the step of establishing a pixel to pixel correspondence between an infrared detector and a humanly visible light detector.

7. The method of claim 1, wherein the step of declaring includes declaring a positive detection, if the first signal is greater than three times as large as the second signal.

8. An apparatus for reducing the false alarm rate of an infrared detection system comprising:

an infrared detector for producing a first signal;

a humanly visible light detector for producing a second signal;

means for comparing the first signal to the second signal;

and

means for declaring a positive detection, if the first signal is large compared to the second signal.

9. The apparatus of claim 8, wherein the infrared detector and the humanly visible light detector are physically boresighted.

10. The apparatus of claim 8, further comprising means for establishing a pixel to pixel correspondence between the infrared detector and the humanly visible light detector.

11. The apparatus of claim 8, wherein the infrared detector comprises an infrared imager and the humanly visible light detector comprises a humanly visible light camera.

12. The apparatus of claim 11, wherein the means for comparing and the means for declaring a positive detection comprise a computer.

13. The apparatus of claim 8, wherein the means for declaring includes means for declaring a positive detection, if the first signal is greater than three times as large as the second signal.

14. An apparatus for reducing the false alarm rate of an infrared detection system comprising:

an infrared detector for producing a first signal;

a humanly visible light detector for producing a second signal;

and

a host computer which includes a video processing card connected to the infrared detector and the humanly visible light detector, for comparing the first signal to the second signal and for declaring a positive detection, if the first signal is large compared to the second signal.

15. The apparatus of claim 14, wherein the infrared detector and the humanly visible light detector are physically boresighted.

16. The apparatus of claim 14, further comprising means for establishing a pixel to pixel correspondence between the infrared detector and the humanly visible light detector.

17. The apparatus of claim 14, wherein the infrared detector comprises an infrared imager and the humanly visible light detector comprises a humanly visible light camera.

18. The apparatus of claim 14, wherein the host computer declares a positive detection, if the first signal is greater than three times as large as the second signal.