System and method for indicating a change between images

• US 5,500,904 A
• Filed: 04/22/1992
• Issued: 03/19/1996
• Est. Priority Date: 04/22/1992
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Reid, Anthony, Markandey, Vishal
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Tran, Phuoc
• Application Number:
  US07/873,932
• Time in Patent Office: 1,427 Days
• Field of Search: 382/56, 382/16, 382/30, 382/1, 382/41, 382/49, 382/54, 358/105, 358/135, 358/136, 348/155, 348/402, 348/113, 348/116, 348/154, 348/413, 348/416, 348/620, 364/423, 364/516, 364/517
• US Class Current: 382/103
• CPC Class Codes: G06T 7/269 using gradient-based methods

Abstract

A method and system are provided for indicating a change between a first image and a second image. In a first aspect, a sequence of images is sensed (304, 310) including the first and second image. The first image is previous in the sequence to the second image. Each image previous in the sequence to the second image is processed generating a first processed image (312). The first processed image and the second image are then processed generating a second processed image (316, 312). The first processed image and the second processed image are then processed generating an optical flow field (314). The optical flow field shows the change between the first image and the second image. In a second aspect, a first sequence of images including the first image is sensed (206). A second sequence of images including the second image is sensed (206). The first sequence is processed generating a first processed image (210). The second sequence is also processed generating a second processed image (208). The first processed image and the second processed image are then processed generating an optical flow field (216). This optical flow field also indicates the change between the first image and the second image.

Claims

1. A system for indicating a change between a first image and a second image of a target represented by electrical signals, comprising:

first means for sensing a sequence of images of the target including the first image, the second image and an additional image previous in said sequence to the first image and the second image, the first image being previous in said sequence to the second image, and for generating and transmitting said electrical signals representing said first image and said second image;

second means coupled to said first means for receiving said electrical signals transmitted by said first means;

third means coupled to said second means for digitizing said electrical signals;

fourth means responsive to said electrical signals and coupled to said third means for determining a first processed image in response to assigning a respective weight to each image previous in said sequence to the second image, determining a second processed image in response to said first processed image and the second image and determining an optical flow field in response to said first processed image and said second processed image, said optical flow field indicating the change between the first image and the second image;

fifth means coupled to said fourth means for indicating a change in the target in response to said optical flow field; and

sixth means coupled to said fifth means and to said first means for controlling said first means in response to said indicated change in the target.

2. The system of claim 1 wherein said fourth means includes means for generating an initialized first processed image by initializing said first processed image to equal said first image.

3. The system of claim 2 wherein said fourth means includes means for generating said second processed image according to

4. The system of claim 1 wherein said fourth means includes means for generating said first processed image according to

5. The system of claim 1 wherein said fourth means includes means for generating said second processed image according to

6. The system of claim 5 wherein 0<

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7. The system of claim 6 wherein 0.2681<

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8. The system of claim 7 wherein said change in the target is indicated by centroid coordinates.

9. The system of claim 8 wherein said change in the target is further indicated by a confidence measure.

10. The system of claim 7 wherein said change in the target comprises a movement of the target.

11. The system of claim 7 wherein said change in the target comprises a change in appearance of the target.

12. The system of claim 1 wherein said first means comprises a moving sensor.

13. A system for indicating a change between a first image and a second image of a target represented by electrical signals, comprising:

first means for sensing a first sequence of images of the target and a second sequence of images of the target, said first sequence including the first image, and said second sequence including the second image, and for generating and transmitting said electrical signals representing said first sequence of images and said second sequence of images;

second means coupled to said first means for receiving said electrical signals transmitted by said first means;

third means coupled to said second means for digitizing said electrical signals;

fourth means responsive to said electrical signals and coupled to said third means for determining a first processed image in response to assigning a respective weight to each image of said first sequence, determining a second processed image in response to said second sequence and determining an optical flow field in response to said first processed image and said second processed image, said optical flow field indicating the change between the first image and the second image;

fifth means coupled to said fourth means for indicating a change in the target in response to said optical flow field; and

sixth means coupled to said fifth means and to said first means for controlling said first means in response to said indicated change in the target.

14. The system of claim 13 wherein said first sequence and said second sequence have at least one image in common.

15. The system of claim 13 wherein the first image is previous in said first sequence to the second image, and wherein said second sequence includes the second image and the first image.

16. The system of claim 15 wherein said first sequence includes the first image and at least one additional image previous in said first sequence to the first image.

17. The system of claim 13 wherein each said respective weight is assigned in response to an order of images in said first sequence, said order including a latest image of said first sequence and an earliest image of said first sequence.

18. The system of claim 17 wherein said respective weight progressively decreases from said latest image to said earliest image.

19. The system of claim 18 wherein said respective weight progressively decreases in an exponential manner from said latest image to said earliest image.

20. The system of claim 19 wherein said respective weight is assigned according to a weighting function

21. A method of indicating a change between a first image and a second image represented by electrical signals, comprising the steps of:

sensing a sequence of images including the first image, the second image and an additional image previous in said sequence to the first image and the second image, the first image being previous in said sequence to the second image;

transmitting electrical signals representing said sequence of images to a receiver;

digitizing said electrical signals representing said sequence of images;

determining a first processed image in response to assigning a respective weight to each image previous in said sequence to the second image;

determining a second processed image in response to said first processed image and the second image;

determining an optical flow field in response to said first processed image and said second processed image, said optical flow field indicating the change between the first image and the second image;

compressing the first image and the second image by encoding the first image and the second image in response to said optical flow field; and

controlling said sensing in response to the indicated change in a target.

22. The method of claim 21 wherein said step of processing said first processed image and the second image comprises the step of generating said second processed image according to

23. The method of claim 21 wherein said step of determining an optical flow field in response to said first processed image and second processed image comprises the step of generating a multiresolution optical flow field.

24. The method of claim 21 wherein said step of determining an optical flow field in response to said first processed image and said second processed image comprises the step of generating said optical flow field according to brightness.

25. The method of claim 21 wherein said step of determining an optical flow field in response to said first processed image and said second processed image comprises the step of generating said optical flow field according to gradient constancy assumptions.

26. The method of claim 21 wherein said step of determining an optical flow field in response to said first processed image and said second processed image comprises the step of generating said optical flow field according to Fourier transform techniques.

27. A method of indicating a change between a first image and a second image represented by electrical signals, comprising the steps of:

sensing a first sequence of images including the first image;

sensing a second sequence of images including the second image;

transmitting electrical signals representing said first sequence of images and said second sequence of images to a receiver;

digitizing said electrical signals representing said first sequence of images and said second sequence of images;

determining a first processed image in response to assigning a respective weight to each image of said first sequence;

determining a second processed image in response to said second sequence;

determining an optical flow field in response to said first processed image and said second processed image, said optical flow field indicating the change between the first image and the second image; and

indicating a change in a target in response to said optical flow field.

28. The method of claim 27 wherein each said respective weight is assigned in response to an order of images in said first sequence, said order including a latest image of said first sequence and an earliest image of said first sequence.

29. The method of claim 28 wherein said respective weight progressively decreases from said latest image to said earliest image.

30. The method of claim 29 wherein said respective weight progressively decreases in an exponential manner from said latest image to said earliest image.

31. The method of claim 30 wherein said respective weight is assigned according to a weighting function

32. The method of claim 27 wherein said optical flow field comprises a plurality of pixel locations each having a value indicative of a magnitude and direction of movement of a corresponding pixel location of the first image relative to the second image.

33. The method of claim 32 wherein said indicating step comprises the step of processing said optical flow field by segmentation.

34. The method of claim 33 wherein said indicating step comprises the step of computing motion energy at a plurality of regions of said optical flow field.

35. The method of claim 33 wherein said step of processing said optical flow field comprises the step of performing histogram segmentation.

36. The method of claim 33 wherein said step of processing said optical flow field comprises the step of performing discontinuity edge detection.