Method for detection of an object using correlation filters with score reaffirmation post processing

• US 7,202,940 B1
• Filed: 06/16/2005
• Issued: 04/10/2007
• Est. Priority Date: 06/16/2005
• Status: Expired due to Fees

• Current Assignee: Secretary Of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Lam, Chi-Kin, Cook, Thomas Dean
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US11/155,926
• Time in Patent Office: 663 Days
• Field of Search: 356/4.01, 356/5.01, 356/5.1, 356/28, 342/90, 342/95, 342/96, 342/159, 382103-106
• US Class Current: 356/4.03
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G06F 18/254 of classification results, e.g. of results related to same input data

Abstract

A method and system for detecting a target which uses composition correlation filters with score reaffirmation post processing for acquiring a target. The method and system uses target decision rules that are based on comparing the dot products, or peaks, of three score reaffirmation filters and their registered LADAR image to detect a target.

Claims

1. A method for detecting targets within a target scene comprising the steps of:

(a) generating LADAR range data of said target scene by directing a LADAR sensor at said target scene;

(b) providing said LADAR range data reflected from said target scene to a first stage correlation filter which detects said targets within a first preset range, azimuth angle and depression angle;

(c) producing a correlation peak for said targets detected by said first stage correlation filter within said first preset range, azimuth angle and depression angle, wherein said first stage correlation filter processes said LADAR range data to produce said correlation peak;

(d) providing a first score reaffirmation filter which is identical to said first stage correlation filter;

(e) providing a second score reaffirmation filter for detecting said targets within a second preset range, azimuth angle and depression angle;

(f) generating a third score reaffirmation filter which consist of said second score reaffirmation filter having a mask of border pixels of said second score reaffirmation filter removed therefrom to generate said third score reaffirmation filter;

(g) calculating dot products for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter; and

(h) comparing the dot products calculated for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter to reaffirm a detection of said targets by said first stage correlation filter.

2. The method of claim 1 wherein said first preset range, azimuth angle and depression angle comprises a preset range of 900 to 1100 meters, an azimuth angle from 90 to 120 degrees, and a depression angle from 8 to 10 degrees.

3. The method of claim 1 wherein said second preset range, azimuth angle and depression angle comprises a preset range of 950 to 1150 meters, an azimuth angle of 80 to 95 degrees, and a depression angle of 8 to 10 degrees.

4. The method of claim 1 wherein said first stage correlation filter comprises twelve filters to detect a potential target within said target scene.

5. The method of claim 1 wherein the dot products calculated for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter comprise first, second and third peak scores respectively for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter.

6. The method of claim 5 wherein a decision rule compares said first peak score to said second peak score and said second peak score to said third peak score to reaffirm said targets detected by said first stage correlation filter.

7. The method of claim 5 wherein said decision rule determines whether second peak score is greater than said first peak score or said third peak score is greater than said second peak score to reaffirm said targets detected by said first stage correlation filter.

8. A method for detecting targets within a target scene comprising the steps of:

(a) generating LADAR range data of said target scene by directing a LADAR sensor at said target scene;

(b) providing said LADAR range data reflected from said target scene to a first stage correlation filter which detects said targets within a first preset range, azimuth angle and depression angle;

(c) producing a correlation peak for said targets detected by said first stage correlation filter within said first preset range, azimuth angle and depression angle, wherein said first stage correlation filter processes said LADAR range data to produce said correlation peak;

(d) providing a first score reaffirmation filter which is identical to said first stage correlation filter;

(e) providing a second score reaffirmation filter for detecting said targets within a second preset range, azimuth angle and depression angle;

(f) generating a third score reaffirmation filter which consist of said second score reaffirmation filter having a mask of border pixels of said second score reaffirmation filter removed therefrom to generate said third score reaffirmation filter wherein said mask of boarder pixels is obtained by providing a narrow filter and subtracting a mask of said narrow filter from a mask of second score reaffirmation filter;

(g) calculating dot products for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter; and

(h) comparing the dot products calculated for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter to reaffirm a detection of said targets by said first stage correlation filter.

9. The method of claim 8 wherein said first preset range, azimuth angle and depression angle comprises a preset range of 900 to 1100 meters, an azimuth angle from 90 to 120 degrees, and a depression angle from 8 to 10 degrees.

10. The method of claim 8 wherein said second preset range, azimuth angle and depression angle comprises a preset range of 950 to 1150 meters, an azimuth angle of 80 to 95 degrees, and a depression angle of 8 to 10 degrees.

11. The method of claim 8 wherein said first stage correlation filter comprises twelve filters to detect a potential target within said target scene.

12. The method of claim 8 wherein the dot products calculated for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter comprise first, second and third peak scores respectively for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter.

13. The method of claim 12 wherein a decision rule compares said first peak score to said second peak score and said second peak score to said third peak score to reaffirm said targets detected by said first stage correlation filter.

14. The method of claim 13 wherein said decision rule determines whether second peak score is greater than said first peak score or said third peak score is greater than said second peak score to reaffirm said targets detected by said first stage correlation filter.

15. The method of claim 8 wherein said narrow filter has a target range from 1025 to 1075 meters, an azimuth angle from 83.5 to 91.5 degrees, and a depression angle from 8 to 10 degrees.

16. An apparatus for detecting targets within a target scene comprising:

(a) means for generating LADAR range data of said target scene;

(b) first stage filtering means for receiving said LADAR range data of said target scene and detecting said targets in said target scene within a first preset range, azimuth angle and depression angle, said first stage filtering means producing a correlation peak for said targets detected by said first stage filtering means within said first preset range, azimuth angle and depression angle, wherein said first stage filtering means processes said LADAR range data to produce said correlation peak;

c) first score reaffirmation filtering means for detecting said targets within said first preset range, azimuth angle and depression angle, wherein said first score reaffirmation filtering means is identical to said first stage filtering means;

(d) second score reaffirmation filtering means for detecting said targets in said target scene within a second preset range, azimuth angle and depression angle;

(e) third score reaffirmation filtering means for detecting said targets within said target scene, said third score reaffirmation filtering means comprising said second score reaffirmation filtering means having a mask of border pixels of said second score reaffirmation filtering means removed therefrom to generate said third score reaffirmation filtering means wherein said mask of boarder pixels is obtained by providing a narrow filter and subtracting a mask of said narrow filter from a mask of said second score reaffirmation filtering means;

(g) means for calculating dot products for said first score reaffirmation filtering means, said second score reaffirmation filtering means and said third score reaffirmation filtering means; and

(h) means for comparing the dot products calculated for said first score reaffirmation filtering means, said second score reaffirmation filtering means and said third score reaffirmation filtering means to reaffirm a detection of said targets by said first stage correlation filtering means.

17. The apparatus of claim 16 wherein said first preset range, azimuth angle and depression angle comprises a preset range of 900 to 1100 meters, an azimuth angle from 90 to 120 degrees, and a depression angle from 8 to 10 degrees, and said second preset range, azimuth angle and depression angle comprises a preset range of 950 to 1150 meters, an azimuth angle of 80 to 95 degrees, and a depression angle of 8 to 10 degrees.

18. The apparatus of claim 16 wherein the dot products calculated for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter comprise first, second and third peak scores respectively for said first score reaffirmation filter, said second score reaffirmation filter and said third score reaffirmation filter.

19. The apparatus of claim 18 wherein a decision rule compares said first peak score to said second peak score and said second peak score to said third peak score to reaffirm said targets detected by said first stage correlation filter.

20. The apparatus of claim 16 wherein said narrow filter has a target range from 1025 to 1075 meters, an azimuth angle from 83.5 to 91.5 degrees, and a depression angle from 8 to 10 degrees.