Method and apparatus for setting black level in an imager using both optically black and tied pixels

• US 20070131846A1
• Filed: 12/14/2005
• Published: 06/14/2007
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Eskerud, Erik
• Granted Patent: US 7,427,735 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: H04N 25/621 for the control of blooming
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/633 by using optical black pixels
• CPC Class Codes: H04N 25/677 for reducing the column or line fixed pattern noise
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors

Abstract

An imaging pixel array includes an active area of pixels, organized into rows and columns of pixels. The array also includes a plurality of dark pixel columns adjacent to the active area of pixels such that rows of pixels in the active area of pixels extend across the plurality of dark pixel columns. The plurality of dark pixel columns are composed of tied pixels. The array also includes a plurality of dark pixel rows adjacent to the active area of pixels and the plurality of dark pixel columns such that columns of pixels in the active area of pixels extend across the plurality of dark pixel rows. The plurality of dark pixel rows are composed of both optically black pixels and tied pixels on the same row.

Claims

1. An imaging pixel array, comprising:

an active area of pixels, organized as a plurality of rows and columns of pixels; and

a plurality of dark pixels arranged in at least one of pixel rows and pixel columns which are adjacent said active area of pixels, said plurality of dark pixels comprising optically black pixels and tied pixels, wherein each row of the plurality of dark pixels is organized into a first half and a second half, the first half comprising optically black pixels, and the second half comprising tied pixels.

2. The imaging pixel array of claim 1, wherein the optically black pixels and tied pixels in the plurality of dark pixel rows are organized in a checkerboard pattern.

4. The imaging pixel array of claim 1, wherein the first and the second halves of dark pixels are located on alternating sides of adjacent dark pixel rows.

5. The imaging pixel array of claim 1, wherein the optically black pixels and the tied pixels in the plurality of dark pixel rows are organized in a symmetrical pattern.

3. (canceled)

6. An apparatus for providing pixel correction values for an imager, said apparatus comprising a black level correction module that calculates a black level correction value based on at least one comparison of output values of a plurality of optically black pixels and a plurality of tied pixels from at least one of a plurality of dark pixel rows of a pixel array.

7. The apparatus of claim 6, wherein the black level correction module further comprises:

an averaging module to calculate an average optically black pixel output and an average tied pixel output for each row in the plurality of dark pixel rows;

a determining module to determine a difference between the average optically black pixel output and the average tied pixel output for each row in the plurality of dark pixel rows; and

a calculating module to calculate the black level correction value as an average of the determined differences.

8. The apparatus of claim 6, wherein the optically black pixels and tied pixels in the plurality of dark pixel rows are organized in a checkerboard pattern.

9. The apparatus of claim 6, wherein each row of the plurality of dark pixel rows is organized into a first half and a second half, the first half comprising optically black pixels, and the second half comprising tied pixels.

10. The apparatus of claim 9, wherein the first and the second halves of pixels are located on alternating sides of adjacent dark pixel rows.

11. The apparatus of claim 6, wherein the optically black pixels and the tied pixels in the plurality of dark pixel rows are organized in a symmetrical pattern.

12. A method of correcting pixel signals of an imager, said method comprising:

calculating an average optically black pixel output and an average tied pixel output for each row in a plurality of dark pixel rows in a pixel array of the imager;

determining a difference between the average optically black pixel output and the average tied pixel output for each row;

averaging the determined differences to generate a black level correction value; and

using the black level correction value to correct the pixel outputs of each pixel in the imager pixel array that is not located in the plurality of dark pixel rows.

13. The method of claim 12, wherein the average optically black pixel output and the average tied pixel output for each row are calculated from a plurality of optically black and tied pixels arranged in a checkerboard pattern within the plurality of dark pixel rows.

14. The method of claim 12, wherein the average optically black pixel output and the average tied pixel output for each row are calculated from a plurality of optically black and tied pixels arranged in a symmetrical pattern within the plurality of dark pixel rows.

15. An imager, comprising:

a pixel array, comprising;

an active area of pixels, composed of rows and columns of pixels; and

a plurality of dark pixels arranged in at least one of pixel rows and pixel columns which are adjacent said active area of pixels, said plurality of pixels comprising optically black pixels and tied pixels; and

a black level calculating module that calculates a black level correction value based on at least one comparison of the outputs of the optically black pixels and the tied pixels in the plurality of dark pixel rows.

16. The imager of claim 15, wherein the black level calculating module further comprises:

averaging module to calculate an average optically black pixel output and an average tied pixel output for each row in the plurality of dark pixel rows;

comparing module to determine a difference between the average optically black pixel output and the average tied pixel output for each row; and

calculating module to calculate the black level correction value as an average of the determined differences.

17. The imager of claim 15, wherein the optically black pixels and tied pixels in the plurality of dark pixel rows are organized in a checkerboard pattern.

18. The imager of claim 15, wherein each row of the plurality of dark pixel rows is organized into a first half and a second half, the first half comprising optically black pixels, and the second half comprising tied pixels.

19. The imager of claim 18, wherein the first and the second halves of pixels are located on alternating sides of adjacent dark pixel rows.

20. The imager of claim 15, wherein the optically black pixels and the tied pixels in the plurality of dark pixel rows are organized in a symmetrical pattern.

21. An imaging system, comprising:

an imager, comprised of;

a pixel array, comprising;

an active area of pixels, composed of rows and columns of pixels; and

a plurality of dark pixels arranged in at least one of pixel rows and pixel columns which are adjacent said active area of pixels, said plurality of pixels comprising optically black pixels and tied pixels; and

a black level calculating module that calculates a black level correction value based on at least one comparison of the outputs of the optically black pixels and the tied pixels in the plurality of dark pixel rows.

22. The system of claim 21, wherein the black level calculating module further comprises:

averaging module to calculate an average optically black pixel output and an average tied pixel output for each row in the plurality of dark pixel rows;

comparing module to determine a difference between the average optically black pixel output and the average tied pixel output for each row; and

calculating module to calculate the black level correction value as an average of the determined differences.

23. The system of claim 21, wherein the optically black pixels and tied pixels in the plurality of dark pixel rows are organized in a checkerboard pattern.

24. The system of claim 21, wherein each row of the plurality of dark pixel rows is organized into a first half and a second half, the first half comprising optically black pixels, and the second half comprising tied pixels.

25. The system of claim 24, wherein the first and the second halves of pixels are located on alternating sides of adjacent dark pixel rows.

26. The system of claim 21, wherein the optically black pixels and the tied pixels in the plurality of dark pixel rows are organized in a symmetrical pattern.

27. A carrier medium for carrying a program for operating a processor to perform the acts of:

calculating an average optically black pixel output and an average tied pixel output for each row in a plurality of dark pixel rows in a pixel array;

determining a difference between the average optically black pixel output and the average tied pixel output for each row;

averaging the determined differences to generate a black level correction value; and

using the black level correction value to correct the pixel outputs of each pixel in the pixel array that is not located in the plurality of dark rows.

28. The carrier medium of claim 27, wherein the average optically black pixel output and the average tied pixel output for each row are calculated from a plurality of optically black and tied pixels arranged in a checkerboard pattern within the plurality of dark pixel rows.

29. The carrier medium of claim 27, wherein the average optically black pixel output and the average tied pixel output for each row are calculated from a plurality of optically black and tied pixels arranged in a symmetrical pattern within the plurality of dark pixel rows.