Method for developing and using an image reconstruction algorithm for multipath scattering

• US 7,259,715 B1
• Filed: 10/19/2004
• Issued: 08/21/2007
• Est. Priority Date: 01/08/2002
• Status: Expired due to Term

• Current Assignee: Leidos, Inc. (Leidos Holdings, Inc.)
• Original Assignee: Science Applications International Corporation
• Inventors: Garren, David Alan, Greeno, Robert R.
• Primary Examiner(s): Gregory; Bernarr E.
• Application Number:
  US10/967,298
• Time in Patent Office: 1,036 Days
• Field of Search: 342 25 R- 25 F, 342/27, 342/28, 342/59, 342159-164, 342175-197, 359/1, 359 27- 29
• US Class Current: 342/179
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/9017 with time domain processing of the SAR signals in azimuth G01S13/9005 takes precedence
• CPC Class Codes: G01S 13/9027 Pattern recognition for feature extraction
• CPC Class Codes: G01S 13/9052 Spotlight mode

Abstract

Described herein is an implementation of the IRAMS processing based upon a multi-delay-resolution framework applied to SAR image data measured at different aspect angles. The power of this new embodiment of IRAMS is that it produces a good separation of immediate response scatterer and delayed response scatterer data for the case of anisotropic scattering events, i.e., those in which the scattering intensity depends upon the aspect angle. Two sources of delayed response scattering include multiple reflection scattering events and delayed responses arising from the physical material composition of the scatterer. That is, this multi-delay-resolution IRAMS processing separates immediate response and delayed response scattering for cases in which there exist delayed response scattering data in the original SAR image data at some aspect angles, but the intensity of these delayed response scattering data is weak or non-existent at different aspect angles. Thus, this IRAMS embodiment provides the additional information of the particular aspect angles at which delayed response scattering effects are most important, thereby improving both the estimates of the delayed response scattering data and the immediate response scattering data.

Claims

1. A process for reconstructing a scene from scattering data comprising:

collecting multiple images of a scene, the multiple images containing scattering data from the scene representing

(a) single reflection data and

(b) multiple reflection data represented within the multiple images by at least one of amplitude data and phase data,

wherein (a) and (b) are located in any one of image planes, 0 to P, wherein P is greater than 0;

accounting for a change in the at least one of amplitude data and phase data representative of (b) from one of the multiple images of the scene to another of the multiple images of the scene;

separating (a) and (b) from the scattering data according to their respective locations within image planes 0 to P utilizing the multiple images.

2. The process according to claim 1, wherein the multiple images include scattering data for two-dimensions of the scene.

3. The process according to claim 1, wherein the multiple images are collected using synthetic aperture radar.

4. The process according to claim 3, wherein the multiple images are collected over a range of aspect angles.

5. The process according to claim 4, wherein the multiple images are collected at predetermined increments over the range of aspect angles.

6. The process according to claim 1, wherein the scene is reconstructed in three dimensions.

7. The process according to claim 1, wherein the scattering data is collected using a co-located transmitter and receiver.

8. The process according to claim 7, wherein the scattering data is comprised of waveforms when it is collected by the co-located transmitter and receiver.

9. The process according to claim 8, wherein the waveforms are collected at a far-field location, such that the wavefronts impinging on the region to be imaged and collected at the receiver are approximately linear.

10. The process according to claim 8, wherein the waveforms are collected at a near-field location, such that the wavefronts impinging on the region to be imaged and collected at the receiver are curved.

11. The process according to claim 1, wherein the scattering data is collected using non co-located transmitters and receivers.

12. The process according to claim 1, wherein the multiple reflection data exist in each of the P image planes.

13. The process according to claim 1, wherein the multiple reflection data exist in fewer than the P image planes.

14. The process according to claim 1, wherein the single reflection and multiple reflection data exhibit anisotropic scattering characteristics.

15. The process according to claim 1, wherein the scattering data is separated into single point and multiple point scattering data which are further separated into a framework containing multiple constituent data sets, each of the multiple constituent data sets being characterized by different aspect angles at which the multiple point scattering data exist and by a delay in the multiple point scattering data.

16. A process for analyzing scattering data from an area-of-interest comprising:

collecting a first image of the area-of-interest at a first aspect angle, the first image containing first scattering data comprised of first single bounce data and first multiple bounce data, which includes at least one of amplitude data and phase data;

collecting a second image of the area-of-interest at a second aspect angle, the second image containing second scattering data comprised of second single bounce data and second multiple bounce data, which includes at least one of amplitude data and phase data;

determining a change in the at least one of amplitude data and phase data of the first multiple bounce data with respect to the second multiple bounce data;

accounting for the change in the at least one of amplitude data and phase data, in order to differentiate the first and second single bounce data from the first and second multiple bounce data; and

analyzing the differentiated first and second single bounce data and the first and second multiple bounce data to determine characteristics of the area-of-interest.

17. The process according to claim 16, wherein the first and second multiple bounce data results from reflection of at least one transmitted signal off of at least two scattering points.

18. The process according to claim 17, wherein the at least one transmitted signal is a radar signal.

19. The process according to claim 16, further comprising:

collecting a third image of the area-of-interest at a third aspect angle, the third image containing third scattering data comprised of third single bounce data, which includes at least one of amplitude data and phase data;

determining a change in the at least one of amplitude data and phase data of the first multiple bounce data with respect to the second multiple bounce data;

accounting for the change in the at least one of amplitude data and phase data, in order to differentiate the first, second and third single bounce data from the first and second multiple bounce data; and

analyzing the differentiated first, second and third single bounce data and the first and second multiple bounce data to determine characteristics of the area-of-interest.

20. The process according to claim 19, wherein the first, second and third single bounce data and the first and second multiple bounce data are separated into a framework containing multiple constituent data sets, each of the multiple constituent data sets being characterized by different aspect angles at which the first and second multiple bounce data exist and by a delay in the first and second multiple bounce data.

21. The process according to claim 16, wherein the first and second single bounce data and the first and second multiple bounce data are separated into a framework containing multiple constituent data sets, each of the multiple constituent data sets being characterized by different aspect angles at which the first and second multiple bounce data exist and by a delay in the first and second multiple bounce data.

22. A process for analyzing scattering data from an area-of-interest comprising:

collecting a first image of the area-of-interest at a first aspect angle, the first image containing first scattering data comprised of first immediate data and first delayed data, which includes at least one of amplitude data and phase data;

collecting a second image of the area-of-interest at a second aspect angle, the second image containing second scattering data comprised of second immediate data and second delayed data, which includes at least one of amplitude data and phase data;

determining a change in the at least one of amplitude data and phase data of the first delayed data with respect to the second delayed data;

accounting for the change in the at least one of amplitude data and phase data, in order to differentiate the first and second immediate data from the first and second delayed data; and

analyzing the differentiated first and second immediate data and the first and second delayed data to determine characteristics of the area-of-interest.

23. The process of claim 22, wherein one of the determined characteristics of the area-of-interest is material composition.

24. The process according to claim 22, further comprising:

collecting a third image of the area-of-interest at a third aspect angle, the third image containing third scattering data comprised of third immediate data, which includes at least one of amplitude data and phase data;

determining a change in the at least one of amplitude data and phase data of the first delayed data with respect to the second delayed data;

accounting for the change in the at least one of amplitude data and phase data, in order to differentiate the first, second and third immediate data from the first and second delayed data; and

analyzing the differentiated first, second and third immediate data and the first and second delayed data to determine characteristics of the area-of-interest.

25. The process according to claim 24, wherein the first, second and third immediate data and the first and second delayed data are separated into a framework containing multiple constituent data sets, each of the multiple constituent data sets being characterized by different aspect angles at which the first and second delayed data exist and by a delay in the first and second delayed data.

26. The process according to claim 22, wherein the first and second immediate data and the first and second delayed data are separated into a framework containing multiple constituent data sets, each of the multiple constituent data sets being characterized by different aspect angles at which the first and second delayed data exist and by a delay in the first and second delayed data.

27. A method for imaging an object-of-interest comprising:

collecting phase history scattering data from the object-of-interest over a range of aspect angles, the scattering data including single point scattering data and multiple point scattering data, which includes at least one of amplitude data and phase data;

identifying the multiple point scattering data within the scattering data over the range of aspect angles according to a change in the at least one of amplitude data and phase data; and

comparing the identified multiple point scattering data with the collected scattering data in order to identify the single point scattering data; and

imaging the object-of-interest using the identified single point scattering data.

28. The process according to claim 27, wherein the multiple point scattering data results from reflection of at least one transmitted signal off of at least two scattering points.

29. The process according to claim 28, wherein the at least one transmitted signal is a radar signal.

30. A process for reconstructing a scene from scattering data comprising:

collecting multiple images of a scene, the multiple images containing scattering data from the scene representing

(a) immediate response data and

(b) delayed response data represented within the multiple images by at least one of amplitude data and phase data,

wherein (a) and (b) are located in any one of image planes, 0 to P, wherein P is greater than 0;

accounting for a change in the at least one of amplitude data and phase data representative of (b) from one of the multiple images of the scene to another of the multiple images of the scene;

separating (a) and (b) from the scattering data according to their respective locations within image planes 0 to P utilizing the multiple images.

31. The process according to claim 30, wherein the multiple images include scattering data for two-dimensions of the scene.

32. The process according to claim 30, wherein the multiple images are collected using synthetic aperture radar.

33. The process according to claim 32, wherein the multiple images are collected over a range of aspect angles.

34. The process according to claim 33, wherein the multiple images are collected at predetermined increments over the range of aspect angles.

35. The process according to claim 30, wherein the scene is reconstructed in three dimensions.

36. The process according to claim 30, wherein the scattering data is collected using a co-located transmitter and receiver.

37. The process according to claim 36, wherein the scattering data is comprised of waveforms when it is collected by the co-located transmitter and receiver.

38. The process according to claim 37, wherein the waveforms are collected at a far-field location, such that the wavefronts impinging on the region to be imaged and collected at the receiver are approximately linear.

39. The process according to claim 37, wherein the waveforms are collected at a near-field location, such that the wavefronts impinging on the region to be imaged and collected at the receiver are curved.

40. The process according to claim 30, wherein the scattering data is collected using non co-located transmitters and receivers.

41. The process according to claim 30, wherein the delayed response data exist in each of the P image planes.

42. The process according to claim 30, wherein the delayed response data exist in fewer than the P image planes.

43. The process according to claim 30, wherein the immediate response data and the delayed response data exhibit anisotropic scattering characteristics.

44. The process according to claim 30, wherein the scattering data is separated into single point and multiple point scattering data which are further separated into a framework containing multiple constituent data sets, each of the multiple constituent data sets being characterized by different aspect angles at which the multiple point scattering data exist and by a delay in the multiple point scattering data.

45. A process for reconstructing a scene from scattering data comprising:

collecting multiple images of a scene, the multiple images containing scattering data from the scene representing

(a) single reflection data and

(b) multiple reflection data,

wherein (a) and (b) are located in any one of image planes, 0 to P, wherein P is greater than 0;

accounting for a drift in the location of (b) from one of the multiple images of the scene to another of the multiple images of the scene;

separating (a) and (b) from the scattering data according to their respective locations within image planes 0 to P utilizing the multiple images.

46. The process according to claim 45, wherein the multiple images include scattering data for two-dimensions of the scene.

47. The process according to claim 45, wherein the multiple images are collected using synthetic aperture radar.

48. The process according to claim 47, wherein the multiple images are collected over a range of aspect angles.

49. The process according to claim 48, wherein the multiple images are collected at predetermined increments over the range of aspect angles.

50. The process according to claim 45, wherein the scene is reconstructed in three dimensions.

51. The process according to claim 45, wherein the scattering data is collected using a co-located transmitter and receiver.

52. The process according to claim 51, wherein the scattering data is comprised of waveforms when it is collected by the co-located transmitter and receiver.

53. The process according to claim 52, wherein the waveforms are collected at a far-field location, such that the wavefronts impinging on the region to be imaged and collected at the receiver are approximately linear.

54. The process according to claim 52, wherein the waveforms are collected at a near-field location, such that the wavefronts impinging on the region to be imaged and collected at the receiver are curved.

55. The process according to claim 45, wherein the scattering data is collected using non co-located transmitters and receivers.

56. A process for analyzing scattering data from an area-of-interest comprising:

collecting a first image of the area-of-interest at a first aspect angle, the first image containing first scattering data comprised of first single bounce data and first multiple bounce data;

collecting a second image of the area-of-interest at a second aspect angle, the second image containing second scattering data comprised of second single bounce data and second multiple bounce data;

determining a cross-range drift of the first multiple bounce data with respect to the second multiple bounce data;

accounting for the cross-range drift in order to differentiate the first and second single bounce data from the first and second multiple bounce data; and

analyzing the differentiated first and second single bounce data and the first and second multiple bounce data to determine characteristics of the area-of-interest.