FIRST-IN-FIRST-OUT (FIFO) BUFFERED MEDIAN SCENE NON-UNIFORMITY CORRECTION METHOD

• US 20120113299A1
• Filed: 11/05/2010
• Published: 05/10/2012
• Est. Priority Date: 11/05/2010
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: PALIK, Stephen M.
• Granted Patent: US 8,625,005 B2
• Time in Patent Office: Days
• US Class Current: 348/241
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20182 Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering
• CPC Class Codes: G06T 2207/20216 Image averaging
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 25/683 by defect estimation performed on the scene signal, e.g. real time or on the fly detection

Abstract

A buffered scene-based non-uniformity correction method includes receiving a plurality of frames of video image data from an image detector; determining relative movement of a current image frame with respect to a previous image frame and responsive to a determination of substantial movement, adding the current image frame to a buffer memory sized to store a predetermined number of video frames; averaging pixel values of the frames in the buffer to determine a mean (or weighted mean) value for each pixel of a reference image; determining correction terms for each pixel of the current image frame by determining the difference between the current image frame pixel values and the corresponding reference image pixels; and correcting the current image frame using the correction terms. A scene-based non-uniformity correction system is also disclosed.

Claims

1. A buffered scene-based non-uniformity correction method comprising:

receiving a plurality of frames of video image data from an image detector;

determining relative movement of a current image frame with respect to a previous image frame;

if there is substantial movement determined, adding the current image frame to a buffer in a memory sized to store a predetermined number of video frames;

averaging pixel values of the frames in the buffer to determine a mean value for each pixel of a reference image;

determining correction terms for each pixel of the current image frame by determining the difference between the current image frame pixel value and the reference image; and

correcting the current image frame using the correction terms.

2. The method according to claim 1, wherein the buffer is a first-in-first-out (FIFO) buffer.

3. The method according to claim 1, wherein the buffer is configured to hold five frames of video.

4. The method according to claim 1, further comprising:

responsive to a determination that the current frame includes a uniform scene with low spatial frequency content, adding the current image frame to the buffer.

5. The method according to claim 1, further comprising:

responsive to a determination that there has been continuous motion in previous frames which has stopped in the current frame, adding one or more additional frames to the buffer corresponding to the current frame.

6. The method according to claim 1, further comprising:

identifying and removing blinking pixels from the images.

7. The method according to claim 1, wherein determining correction term values for each pixel comprises:

determining pixels in a near region to the current pixel;

determining pixels in a far region to the current pixel; and

analyzing the near and far region pixels.

8. The method according to claim 1, wherein determining relative movement of a current image frame with respect to the previous image frame comprises:

determining row and column sum vectors for the current image from and the previous image frame; and

analyzing the determined row and column sum vectors to determine a correlation between the current image frame and the previous image frame.

9. The method according to claim 8, wherein analyzing the determined row and column sum vectors comprises:

searching for movement between the current image frame and the previous image frame within a predetermined distance from each current pixel.

10. The method according to claim 1, wherein regions in the current frame which have high-frequency or dynamic range scene content are not corrected.

11. The method according to claim 1, wherein the pixel values of the frames in the buffer are continuously averaged when new frames are added to the buffer.

12. The method according to claim 1, wherein the mean value is a weighted mean value.

13. A buffered scene-based non-uniformity correction system comprising:

a buffer memory sized to store a predetermined number of video frames; and

a processor configured to;

receive a plurality of frames of video image data from an image detector;

determine relative movement of a current image frame with respect to a previous image frame;

if there is substantial movement determined, add the current image frame to the buffer;

average pixel values of the frames in the buffer to determine a mean value for each pixel of a reference image;

determine correction terms for each pixel of the current image frame by determining the difference between the current image frame pixel value and the reference image; and

correct the current image frame using the correction terms.

14. The system according to claim 13, further comprising:

a image detector configured to generated the video data.

15. The system according to claim 13, wherein the buffer is a first-in-first-out (FIFO) buffer.

16. The system according to claim 13, wherein the buffer is configured to hold five frames of video.

17. The system according to claim 13, wherein the processor is configured to:

responsive to a determination that the current frame includes a uniform scene with low spatial frequency content, add the current image frame to the buffer.

18. The system according to claim 13, wherein the processor is configured to:

responsive to a determination that there has been continuous motion in previous frames which has stopped in the current frame, add one or more additional frames to the buffer corresponding to the current frame.

19. The system according to claim 13, wherein the processor is configured to:

Identify and remove blinking pixels from the images.

20. The system according to claim 13, wherein, in determining correction term values for each pixel, the processor is configured to:

determine pixels in a near region to the current pixel;

determine pixels in a far region to the current pixel; and

analyze the near and far region pixels.

21. The system according to claim 13, wherein, in determining relative movement of a current image frame with respect to the previous image frame, the processor is configured to:

determine row and column sum vectors for the current image from and the previous image frame; and

analyze the determined row and column sum vectors to determine a correlation between the current image frame and the previous image frame.

22. The system according to claim 21, wherein, in analyzing the determined row and column sum vectors, the processor is configured to:

search for movement between the current image frame and the previous image frame within a predetermined distance from each current pixel.

23. The system according to claim 13, wherein regions in the current frame which have high-frequency or dynamic range scene content are not corrected.

24. The system according to claim 13, wherein the pixel values of the frames in the buffer are continuously averaged when new frames are added to the buffer.

25. The system according to claim 13, wherein the mean value is a weighted mean value.