Non-contact radar system for reconstruction of scenes obscured under snow and similar material

• US 6,621,448 B1
• Filed: 04/05/2002
• Issued: 09/16/2003
• Est. Priority Date: 04/05/2002
• Status: Expired due to Fees

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Shahrdad, Tabib, Ravani, Bahram, Lasky, Ty A.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US10/117,988
• Publication Number:
  US 20030189511A1
• Time in Patent Office: 529 Days
• Field of Search: 342/21, 342/22, 342/26, 342/27, 342/28, 342/89, 342/90, 342/118, 342/145, 342/146, 342/147, 342/158, 342/175, 342/195, 342/5, 342/11, 342/25, 342/157, 342/176, 342/179, 342/190, 342/191
• US Class Current: 342/22
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A system and method for imaging objects obscured by a covering layer of snow. The system preferably utilizes a continuous-wave radar generating short-wavelength radio-frequency (RF) signal beam-scanned over angular displacements following a scanning pattern toward a target area. Reflections of the:RF signal from objects buried beneath the snow are registered by an array of RF detectors whose signal magnitudes are summed arid correlated with scan direction to generate a signal providing spatial object information, Which by way of example, is visually displayed. The radio-frequency beam may be scanned over the scene electronically or by either mechanically or electromechanically modulating antenna direction or the orientation of a beam deflector. The system is capable of generating multiple image frames per second, high-resolution imaging, registration of objects to a depth exceeding two meters, and can be implemented at low cost without complex signal processing hardware.

Claims

1. An apparatus for detecting an object which is obscured beneath a covering of snow, comprising:

(a) means for generating a radio-frequency (RF) scanning beam over a predetermined scan path; and

(b) means for detecting the magnitude of a reflection of said beam from an object in said scan path, correlating the direction of said scanning beam with the magnitude of said reflection, and generating spatial information regarding said object from said correlation.

2. An apparatus as recited in claim 1, wherein said means for generating a radio-frequency (RF) scanning beam over a scan path comprises:

(a) an RF transmitter; and

(b) a beam scanning device configured to spatially modulate output signals from said RF transmitter.

3. An apparatus as recited in claim 1 ,wherein said means for detecting the magnitude of a reflection of said scanning beam from an object in said scan path, correlating the direction of said scanning beam with the magnitude of said reflection, and generating spatial information regarding said object from said correlation, comprises:

(a) an RF receiver;

(b) a computer; and

(c) programming associated with said computer for,

(i) correlating the direction of said scanning beam with the magnitude of said reflection, and

(ii) generating an object detection signal;

(d) wherein said object detection signal provides spatial information about one or more objects in said scan path.

9. An apparatus as recited in claim 1, 4, 6 or 8, wherein said scanning beam has an RF frequency in the range from approximately 100 MHz to approximately 6 GHz.

10. An apparatus as recited in claim 9, wherein said RF frequency is approximately 4 GHz.

11. An apparatus as recited in claim 1, 4, 6 or 8, wherein said scanning beam has an RF power level in the range from approximately 100 mW to approximately 2 W.

12. An apparatus as recited in claim 11, wherein said RF power level is approximately 1 W.

13. An apparatus as recited in claim 2, 4, 7 or 8, wherein said RF transmitter comprises:

(a) an RF waveform generator;

(b) an RF power amplifier connected to said radio frequency waveform generator.

14. An apparatus as recited in claim 13, further comprising an antenna connected to said power amplifier.

15. An apparatus as recited in claim 14, further comprising a negative refractive index lens positioned in the output path of said antenna.

16. An apparatus as recited in claim 14, wherein said antenna comprises a rutile dielectric-filled horn.

17. An apparatus as recited in claim 2, 4, 7 or 8, wherein said beam scanning device is configured to spatially modulate signals from said RF transmitter by modulating the phase relationship between multiple antennas connected to said RF transmitter.

18. An apparatus as recited in claim 2, 4, 7 or 8, wherein said beam scanning device is configured to spatially modulate signals from said RF transmitter by modulating the direction of an antenna connected to said RF transmitter.

19. An apparatus as recited in claim 2, 4, 7 or 8, wherein said beam scanning device is configured to spatially modulate signals from said RF transmitter by modulating the direction of a beam deflector device upon Which said RF signals impinge.

20. An apparatus as recited in claim 3, 5, 6 or 8, further comprising:

a display unit adapted to receive said object detection signal and to display images of said detected objects.

21. An apparatus as recited in claim 20, further comprising synthetic aperture imaging means for combining multiple images of the target area by pixel interpolation to generate composite images of the target area having higher image resolution than provided by the individual contributing images.

22. An apparatus as recited in claim 21, wherein said synthetic aperture imaging means comprises:

(a) a computer configured to receive and store multiple spatially displaced object images; and

(b) programming associated.with said computer for,

(i) interpolating between pixels of said spatially displayed object images to combine the images into a composite image having a higher image resolution than the individual contributing images.

23. An apparatus as recited in claim 3, 5, 6 or 8, wherein said RF receiver comprises:

(a) a detector array; and

(b) a summing amplifier configured to sum and amplify signals received by said detector array.

24. An apparatus as recited in claim 23, wherein said computer controls the gain of said summing amplifier.

25. An apparatus as recited in claim 23, wherein said detector array comprises:

(a) a plurality of antennas; and

(b) a plurality of RF detectors associated with said antennas.

26. An apparatus as recited in claim 25, wherein said RF detectors comprise Schottky diodes.

27. An apparatus as recited in claim 1, 4, 6 or 8, further comprising means for periodically suspending, or redirecting, said generated radio frequency beam, and for detecting the level of background radiation present for use in compensating the object detection signal for background radiation levels.

28. An apparatus as recited in claim 27, wherein said means for periodically suspending, or redirecting, said radio-frequency transmissions comprises:

programming executed on a computer and adapted to selectively deactivate, or redirect, the output of said radio-frequency transmitter so that the background radiation level is detected.

29. An apparatus as recited in claim 3, 5, 6 or 8, further comprising an annunicator responsive to said object detection signal for indicating detection of an object.

30. An apparatus as recited in claim 29, wherein said annunicator is selected from the group consisting essentially of audible, visual, haptic, and kinesthetic alert devices.

4. An apparatus for detecting an object which is obscured beneath a covering of snow, comprising:

(a) an RF transmitter;

(b) a beam scanning device configured to spatially modulate output signals from said RF transmitter and form a scanning beam; and

(c) means for detecting the magnitude of a reflection of said scanning beam from an object in said scan path, correlating the direction of said scanning beam with the magnitude of said reflection, and generating spatial information regarding said object from said correlation.

5. An apparatus as recited in claim 4, wherein said means for detecting the magnitude of a reflection of said scanning beam from an object in said scan path, correlating the direction of said scanning beam with the magnitude of said reflection, and generating spatial information regarding said object from said correlation, comprises:

(a) an RF receiver;

(b) a computer; and

(c) programming associated with said computer for;

(i) correlating the direction of said scanning beam with the magnitude of said reflection, and

(ii) generating an object detection signal;

(d) wherein said object detection signal provides spatial information about one or more objects in said scan path.

6. An apparatus for detecting an object which is obscured beneath a covering of snow, comprising:

(a) means for generating a radio-frequency (RF) scanning beam over a predetermined scan path;

(b) an RF receiver;

(c) a computer; and

(d) programming associated with said computer for,

(i) correlating the direction of said scanning beam with the magnitude of said reflection; and

(ii) generating an object detection signal;

(e) wherein said object detection signal provides spatial information about one or more objects in said scan path.

7. An apparatus as recited in claim 6, wherein said means for generating a radio-frequency (RF) scanning beam over a scan path comprises:

(a) an RF transmitter; and

(b) a beam scanning device configured to spatially modulate output signals from said RF transmitter.

8. An apparatus for detecting an object which is obscured beneath a covering of snow, comprising:

(a) an RF transmitter;

(b) a beam scanning device configured to spatially modulate output signals from said RF transmitter and form a scanning beam;

(c) an RF receiver,

(d) a computer; and

(e) programming associated with said computer for,

(i) correlating the direction of said scanning beam with the magnitude of said reflection, and

(ii) generating an object detection signal;

(f) wherein said object detection signal provides spatial information about one or more objects in said scan path.

31. A method of detecting objects whose visibility is obscured by a layer of snow, comprising:

generating a narrow radio-frequency signal beam of sufficient frequency and power to penetrate snow;

scanning said signal beam over a predetermined scan path oriented toward a target area;

detecting the amplitude of the reflected radio-frequency signal beam; and

generating an object detection signal based on correlating said predetermined scan path with the amplitude of said detected radio-frequency signal.

32. A method as recited in claim 31, further comprising:

annunciating the receipt of said object detection signal in response to objects obscured from view by snow.

33. A method as recited in claim 32, wherein said annunciating of said object detection signal is performed by displaying an image of objects on a display in response to radio-frequency signal reflections from said target area.

34. A method as recited in claim 31, further comprising:

suspending the generation of the radio-frequency signal beam for predetermined periods of time;

detecting the level of background radiation that is present during said suspension of radio-frequency signal beam generation; and

compensating for the background radiation when generating staid object detection signal.

35. A method as recited in claim 31, further comprising:

enhancing image resolution by performing synthetic aperture, imaging in which image pixel intensity is interpolated based on the amplitude of the radio-frequency signal beams being detected from spatially displaced locations.

36. A method as recited in claim 31, wherein said narrow high frequency radio-frequency signal beam is generated.within an approximate range of frequencies between 100 MHz and 6 GHz.

37. A method as recited in claim 31, wherein the step of scanning said signal beam over a predetermined scan path comprises deflecting said narrow high frequency radio-frequency signal beam toward said target area following a predetermined scanning pattern.

38. A method as recited in claim 31, wherein said generation of said object detection signal comprises combining the amplitude of said detected radio-frequency signal and position information along said predetermined scan path.

39. A method as recited in claim 31, further comprising generating an alarm to alert an operator of said system.

40. A method as recited in claim 39, wherein said alarm comprises audible video or kinesthetic operator feedback.

41. A method as recited in claim 40, wherein said kinesthetic feedback comprises coupling a haptic feedback device to the seat, or controls, of said operator.