Technique for detecting and identifying certain objects

• US 5,389,790 A
• Filed: 02/15/1991
• Issued: 02/14/1995
• Est. Priority Date: 02/15/1991
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Honey, Richard C., Brown, Robert A.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US07/656,766
• Time in Patent Office: 1,460 Days
• Field of Search: 382/17, 455/604, 250/342, 359/154
• US Class Current: 250/342
• CPC Class Codes: G01V 8/10 Detecting, e.g. by using light barriers by reflection from the object G01S17/00

Abstract

There is disclosed herein a technique for detecting and/or identifying a particular object from which electromagnetic radiation is emitted or reflected at an intensity which fluctuates in accordance with a frequency pattern unique to that object. In accordance with the technique, the fluctuating electromagnetic radiation is detected by suitable equipment which can operate across an optical bandwidth extending from the ultraviolet (200 nm) to the infrared (14 micrometers) spectrum. The detected electromagnetic radiation is converted to an electrical signal having the same unique frequency pattern as the electromagnetic radiation itself. This electrical signal, its frequency pattern serving as an identifying signature of the object in question, is used to detect, track, and/or identify the object.

Claims

1. A method of identifying a particular object from which electromagnetic radiation is emitted and/or reflected at an intensity that fluctuates in accordance with a frequency pattern unique to that object, said method comprising the steps of:

(a) detecting electromagnetic radiation that is emitted and/or reflected from an object during normal operation and is not provided as a special identification signal transmitted for the purpose of identifying the object;

(b) converting said detected radiation to an electric signal having the same unique frequency pattern as the electromagnetic radiation itself, the frequency pattern of said electrical signal serving as an identifying signature of said object; and

(c) using said electrical signal to identify said object.

2. A method according to claim 1 wherein said electrical signal is used to produce an acoustical signal at an intensity that fluctuates in accordance with a frequency pattern unique to said object and easily discernable by the human ear.

3. A method according to claim 1 wherein said electric signal is compared with one or more pre-established identifying signatures of known objects in order to identify the object in question.

4. A method of identifying an object that introduces intensity fluctuations into electromagnetic radiation emitted and/or reflected from the object, said fluctuations having a frequency not easily discernible by the human eye, but characteristic of said object, said fluctuations being incidental to normal operation of said object and not provided as a special identification code for the purpose of identifying said object, said method comprising the steps of:

(a) detecting said electromagnetic radiation; and

(b) producing from said detected radiation an acoustic signal at an intensity that fluctuates at a frequency which is also characteristic of said object but which is easily discernible by the human ear, whereby a person is able to listen to said acoustical signal and thereby identify said object.

5. A method according to claim 4 wherein the frequency of said electromagnetic radiation is within the bandwidth of the human ear and wherein said acoustic signal is produced at the same frequency as said radiation.

6. A method according to claim 5 wherein said acoustic signal is produced by first converting said radiation to an intermediate electrical signal from and at the same frequency as said electromagnetic radiation and thereafter producing said acoustic signal from and at the same time frequency as said intermediate electrical signal.

7. A method according to claim 4 wherein the frequency of said electromagnetic radiation is above the bandwidth of the human ear, and wherein said acoustic signal is produced by first converting said radiation to an intermediate electrical signal from and at the same frequency as said electromagnetic radiation, then downconverting said electrical signal to a lower frequency characteristic of said object and easily discernible by the human ear, and thereafter producing said acoustic signal from said downconverted electrical signal.

8. A method according to claim 4 wherein said spectral bands of interest consists of the ultraviolet, visible, and infrared bands.

9. A method according to claim 4 wherein said object is a fluctuating source of said radiation.

10. A method according to claim 4 wherein said step of detecting said radiation includes independently detecting radiation within a plurality of sub-bands of said spectral band of interests.

11. A method according to claim 10 wherein said spectral band extends from the ultra-violet spectrum starting at about 200 nm to the far infrared spectrum ending at about 14 μ

m.

12. A method according to claim 11 wherein said sub-bands includes the following:

400 μ

m-1100 μ

m

3 μ

m-5 μ

m

8 μ

m-12 μ

m

13. A method according to claim 4 including the step of making a video recording of said electromagnetic radiation as it fluctuates in intensity from said object.

14. A method according to claim 4 wherein said object and/or the means used to detect said object moves and including the step of tracking said object as the object and or the detecting means moves relative to the other.

15. A method of identifying objects that cause the intensity of electromagnetic radiation which is emitted and/or reflected from the object to fluctuate in accordance with a frequency pattern unique to the object, wherein said frequency pattern is provided incidental to normal operation and not provided as a special identification code for the purpose of identifying the object, said method comprising the steps of:

(a) detecting said electromagnetic radiation;

(b) converting said detected radiation to an electric signal having the same unique frequency pattern as the electromagnetic radiation itself, the frequency pattern of said electrical signal serving as an identifying signature of the object;

(c) comparing said identifying signature of said object in question with one or more pre-established signatures of known objects; and

(d) from the comparison between said identifying signature and said pre-established signatures, identifying the object in question.

16. A method according to claim 15 including the step of producing from said detected radiation an acoustic signal at an intensity that fluctuates in accordance with a frequency pattern unique to said object and which is easily discernible by the human ear, whereby a person is able to listen to said acoustical signal and thereby identify said object.

17. An apparatus for identifying objects that cause the intensity of electromagnetic radiation which is emitted and/or reflected from the object to fluctuate in accordance with a frequency pattern unique to the object, wherein said frequency pattern is provided incidental to normal operation and not broadcast as a special identification code for the purpose of identifying the object, said apparatus comprising:

(a) means for detecting said electromagnetic radiation;

(b) means for converting said detected radiation to an electrical signal having the same unique frequency pattern as the electromagnetic radiation itself, the frequency pattern of said electrical signal serving as an identifying signature of the object; and

(c) means for comparing said identifying signature of said object in question with one or more pre-established signatures of known objects, whereby from the comparison between said pre-established signatures, the object in question can be identified.

18. An apparatus according to claim 17 for identifying objects that emit electromagnetic radiation at intensities that fluctuate in accordance with frequency patterns unique to the objects, wherein said means for comparing said identifying signature comprise means for comparing said signature with a pre-established signature for electromagnetic radiation emitted by at least one of an AC-powered light, a missile launch, rocket launch, artillery flash, gunfire, explosion, ground fire, target designator, rocket plume, electric arc, flare, and sun glint.

19. An apparatus according to claim 17 for identifying objects that modulate ambient light wherein said means for comparing said identifying signature comprise means for comparing said signature with signature with a pre-established signature for sunlight reflected from at least one of a helicopter, airplane, wheeled vehicle, jet, motor, and generator.