Method and apparatus for acquisition and tracking of light sources in a transient event rich environment

• US 5,260,557 A
• Filed: 01/31/1992
• Issued: 11/09/1993
• Est. Priority Date: 01/31/1992
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Flynn, David, Kissh, Frank, Fowski, Walter, Bolin, Kenneth, Miklus, Kenneth, Abreu, Rene
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Messinger, Michael
• Application Number:
  US07/829,459
• Time in Patent Office: 648 Days
• Field of Search: 250/203.6, 250/208.1, 250/203.3, 250/203.1, 358/109, 358/103, 382/50-53, 382/48, 382/27, 382/1, 356/141, 356/152
• US Class Current: 250/203.6
• CPC Class Codes: G01S 3/7867 Star trackers navigation using star trackers G01C21/025

Abstract

A method and apparatus for tracking a light source in a transient event rich environment locks on to a light source incident on a field-of-view 1 of a charge-coupled-device (CCD) array 6, validates the permanence of said light source and transmits data relating to the brilliance and location of said light source if said light source is determined to be permanent.

Claims

1. A method for tracking a light source in the field-of-view of a tracking system in a transient event rich environment, the system having a charge-coupled-device (CCD) array, a processor, a memory for storing digitized data, and a communication means for communicating data as to the position and brightness of said light source to a host, the method comprising the steps of:

a) obtaining a first data set representative of the brightness of the field-of-view incident upon the pixels of an acquisition window array comprising at least a portion of said CCD array and storing said data set to memory;

b) obtaining a second data set representative of the brightness of the field-of-view incident upon the pixels of said acquisition window and storing said data set to memory;

c) comparing said first data set stored in memory with said second data set stored in memory so as to select the pixel coordinates of a target group of pixels from said second data set of said acquisition window and store the pixel coordinates of said target group in memory, said target group is determined from a group of contiguous pixels from said second data set having approximately the same brightness and location as a group of contiguous pixels from said first data set;

d) obtaining a third data set representative of the brightness of the field-of-view incident upon the pixels of a tracking window array comprising at least a portion of said CCD array, wherein the center of said tracking window array has the same pixel coordinates as said target group of pixels, and storing said data to memory;

e) comparing the location of said target group of pixels with the brightness and location of the pixels of said tracking window array so as to determine the pixel coordinates of a tracking group of pixels, said tracking group determined from a group of contiguous pixels having approximately the same brightness and position as said target group; and

f) outputting to said host the pixel coordinates and brightness of said tracking group.

2. The method of claim 1, wherein the system further includes a dynamic threshold function and wherein said first data set and said second data set are obtained with said dynamic threshold function activated.

3. The method of claim 1, wherein said group of contiguous pixels from said first and second data sets comprise at least two pixels.

4. The method of claim 1, wherein said group of contiguous pixels from said first data set and said second data set is above a predetermined magnitude threshold.

5. The method of claim 1, wherein said target group is further determined by a first group of contiguous pixels from said second data set having approximately the same pixel location as a group of contiguous pixels in a target window, said target window comprising at least a portion of said acquisition window and having a center with the same pixel coordinates as a group of contiguous pixels from said first data set.

6. The method of claim 1, wherein said group of contiguous pixels of said third data set comprise at least two pixels.

7. The method of claim 1, wherein said group of contiguous pixels of said third data set is above a predetermined magnitude threshold.

8. The method of claim 1, wherein said tracking group is determined by selecting the group of contiguous pixels representing the brightest object within the field-of-view incident on said tracking window.

9. The method of claim 1, wherein said tracking group is determined by selecting a group of contiguous pixels closest to a predetermined location.

10. The method of claim 9, wherein said predetermined location is the center of said target group.

11. The method of claim 1, wherein said tracking group is determined by selecting a group of contiguous pixels located from the center of the tracking window in a predetermined direction, wherein said predetermined direction is derived from the location of the group of continuous pixels in the target window relative to the center of the target window.

12. The method of claim 1, wherein the method is returned to the step for obtaining a first data set if no target group is determined.

13. The method of claim 1, wherein the method is returned to the step for obtaining a first data set if no tracking group is determined.

14. The method of claim 1, wherein the output to said host further includes data as to the quality of the tracking group, wherein said quality indication is determined by the position and brightness of said tracking group.

15. The method of claim 14, wherein said tracking group quality indication is further determined by the centroid of the group of contiguous pixels being within a radius of a predetermined location.

16. The method of claim 14, wherein said tracking group quality is further determined by comparing tracking group brightness measurements with target group brightness measurements.

17. The method of claim 14, wherein the method is returned to the step for obtaining a third data set and wherein the pixel coordinates of said tracking group become the pixel coordinates of said target group.

18. The method of claim 17, wherein the system is returned to the step for obtaining a third data set as long or said tracking group is above a preset quality threshold.

19. A system for tracking a light source in the field-of-view of a tracking system in a transient event rich environment, the system having a charge-coupled-device (CCD) array, a processor, a memory for storing digitized data, and a communication means for communicating data as to the position and brightness of said light source to a host, the system comprising:

a) means for obtaining a first data set representative of the brightness of the field-of-view incident upon the pixels of an acquisition window array comprising at least a portion of said CCD array and means for storing said data set to memory;

b) means for obtaining a second data set representative of the brightness of the field-of-view incident upon the pixels of said acquisition window and means for storing said data set to memory;

c) means for comparing said first data set stored in memory with said second data set stored in memory so as to select the pixel coordinates of a target group of pixels from said second data set of said acquisition window and means for storing the pixel coordinates of said target group is in memory, said target group determined from a group of contiguous pixels from said second data set having approximately the same brightness and location as a group of contiguous pixels from said first data set;

d) means for obtaining a third data set representative of the brightness of the field-of-view incident upon the pixels of a tracking window array comprising at least a portion of said CCD array, wherein the center of said tracking window array has the same pixel coordinates as said target group of pixels, and means for storing said data to memory;

e) means for comparing the location of said target group of pixels with the brightness and location of the pixels of said tracking window array so as to determine the pixel coordinates of a tracking group of pixels, said tracking group determined from a group of contiguous pixels having approximately the same brightness and position as said target group; and

f) means for outputting to said host the pixel coordinates and brightness of said tracking group.

20. The system of claim 19, wherein the system further includes a dynamic threshold function and wherein said first data set and said second data set are obtained with said dynamic threshold function activated.

21. The system of claim 19, wherein said group of contiguous pixels from said first and second data sets comprise at least two pixels.

22. The system of claim 19, wherein said group of contiguous pixels from said first data set and said second data set is above a predetermined magnitude threshold.

23. The system of claim 19, wherein said target group is further determined by a first group of contiguous pixels from said second data set having approximately the same pixel location as a group of contiguous pixels in a target window, said target window comprising at least a portion of said acquisition window and having a center with the same pixel coordinates as a group of contiguous pixels from said first data set.

24. The system of claim 19, wherein said group of contiguous pixels of said third data set comprise at least two pixels.

25. The system of claim 19, wherein said group of contiguous pixels of said third data set is above a predetermined magnitude threshold.

26. The system of claim 19, wherein said tracking group is determined by means for selecting the group of contiguous pixels representing the brightest object within the field-of-view incident on said tracking window.

27. The system of claim 19, wherein said tracking group is determined by means for selecting a group of contiguous pixels closest to a predetermined location.

28. The system of claim 27, wherein said predetermined location is the center of said target group.

29. The system of claim 19, wherein said tracking group is determined by means for selecting a group of contiguous pixels located from the center of the tracking window in a predetermined direction, wherein said predetermined direction is derived from the location of the group of continuous pixels in the target window relative to the center of the target window.

30. The system of claim 19, wherein the system is returned to the means for obtaining a first data set if no target group is determined.

31. The system of claim 19, wherein the system is returned to the means for obtaining a first data set if no tracking group is determined.

32. The system of claim 19, wherein the output of the means for outputting to said host further includes data as to the quality of the tracking group, wherein said quality is determined by the position and brightness of said tracking group.

33. The system of claim 19, wherein said tracking group quality indication is further determined by the distance of the centroid of said tracking group from a predetermined location.

34. The system of claim 33 wherein said tracking group quality is further determined by comparing tracking group brightness measurements with target group brightness measurements.

35. The system of claim 32, wherein the system is returned to the means for obtaining a third data set and where in the pixel coordinates of said tracking group become the pixel coordinates of said target group.

36. The system of claim 35, wherein the system is returned to the means for obtaining a third data set as long as said tracking group is above a preset quality threshold.