Object detection method and apparatus

• US 20050099330A1
• Filed: 11/24/2004
• Published: 05/12/2005
• Est. Priority Date: 05/25/1999
• Status: Active Grant

• Current Assignee: Peacock Myers PC
• Original Assignee: Safe Food Systems Incorporated
• Inventors: West, Jonathan M., Hausner, Jerry
• Granted Patent: US 7,167,123 B2
• Time in Patent Office: Days
• US Class Current: 342/22
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: G01S 7/2883 using FFT processing
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

Method and apparatus for detecting objects. In one embodiment, a person entering a secured zone is illuminated with low-power polarized radio waves. Differently polarized waves which are reflected back from the person are collected. Concealed weapons are detected by measuring various parameters of the reflected signals and then calculating various selected differences between them. These differences create patterns when plotted as a function of time. Preferably a trained neural network pattern recognition program is then used to evaluate these patterns and autonomously render a decision on the presence of a weapon.

Claims

1. A method of determining a presence of an object associated with a target, the method comprising the steps of:

illuminating a target with polarized illuminating radiation;

collecting first radiation reflected from the target which has a same polarization as the illuminating radiation;

collecting second radiation reflected from the target which has an opposite polarization from the illuminating radiation; and

employing a weighted plurality of criteria of the first radiation and the second radiation to determine the presence of the object.

2. A method as recited in claim 1, wherein the employing step comprises employing a weighted plurality of criteria of the collected radiation converted to a time domain by a Chirp-Z Transform process.

3. A method as recited in claim 2, wherein the employing step comprises employing a magnitude spread of one or both of the first radiation and the second radiation at a plurality of times.

4. A method as recited in claim 2, wherein the employing step comprises employing a plurality of criteria selected from the group consisting of a first magnitude of the first radiation at zero time after conversion to the time domain by the Chirp-Z Transform process, a second magnitude of the second radiation at zero time after conversion to the time domain by the Chirp-Z Transform process, and a difference between the first magnitude and the second magnitude.

5. A method as recited in claim 4, wherein the employing step comprises employing a time of arrival difference between the first radiation and the second radiation.

6. A method as recited in claim 4, wherein the employing step comprises employing a measurement of the shape of a curve of one or both of the first radiation and the second radiation in the time domain or frequency domain.

7. A method as recited in claim 6, wherein the measurement comprises a ratio of a peak value of the curve to a total area under the curve.

8. A method as recited in claim 1 wherein the method is repeated a plurality of times, and further comprising the step of combining results of each performance of the method.

9. A method as recited in claim 3, further comprising the step of training a neural network on calibration data.

10. A method as recited in claim 9 wherein the employing step further comprises the step of using the neural network to autonomously determine presence of the object.

11. A method as recited in claim 1, in which the target comprises a person.

12. A method as recited in claim 1, in which the object comprises a concealed weapon.

13. A method as recited in claim 12, in which the concealed weapon is selected from the group consisting of a knife, firearm, gun, bomb, explosive device, and suicide vest.

14. An apparatus for detecting an object associated with a target, said apparatus comprising:

a transmit antenna for illuminating the target with polarized illuminating radiation;

a first receive antenna for collecting first radiation reflected from the target which has a same polarization as the illuminating radiation;

a second receive antenna for collecting second radiation reflected from the target which has an opposite polarization from the illuminating radiation; and

a processor for employing a weighted plurality of criteria of the first radiation and the second radiation to determine a presence of the object.

15. An apparatus as recited in claim 14, wherein said processor employs a weighted plurality of criteria of the collected radiation converted to a time domain by a Chirp-Z Transform process.

16. An apparatus as recited in claim 15, wherein said processor employs a magnitude spread of one or both of said first radiation and said second radiation at a plurality of times.

17. An apparatus as recited in claim 15, wherein said processor employs a plurality of criteria selected from the group consisting of a first magnitude of said first radiation at zero time after conversion to the time domain by the Chirp-Z Transform process, a second magnitude of said second radiation at zero time after conversion to the time domain by the Chirp-Z Transform process, and a difference between said first magnitude and said second magnitude.

18. An apparatus as recited in claim 17 wherein said processor employs a time of arrival difference between said first radiation and said second radiation.

19. An apparatus as recited in claim 17 wherein said processor employs a shape of a curve of one or both of said first radiation and said second radiation in the time domain or frequency domain.

20. An apparatus as recited in claim 17, wherein said processor employs a variation in time of one or both of the first radiation and the second radiation.

21. An apparatus as recited in claim 14, wherein a single dual-polarized antenna comprises said first receive antenna and said second receive antenna.

22. An apparatus as recited in claim 14, wherein said processor combines results from a plurality of applications of the illuminating radiation to the target.

23. An apparatus as recited in claim 14, in which the target is a person.

24. An apparatus as recited in claim 14, in which the object is a concealed weapon.

25. An apparatus as recited in claim 24, in which the concealed weapon is selected from the group consisting of a knife, firearm, gun, bomb, explosive device, and suicide vest.

26. An apparatus as recited in claim 14 wherein said processor employs a neural network to automatically detect the presence of the object.

27. An apparatus as recited in claim 26 wherein said processor assigns a value to each of said criteria and determines the presence of the object based on a combination of values of said criteria.