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

• US 7,800,042 B2
• Filed: 08/18/2008
• Issued: 09/21/2010
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Eskerud, Erik
• Primary Examiner(s): Luu; Thanh X
• Application Number:
  US12/222,857
• Publication Number:
  US 20080315073A1
• Time in Patent Office: 764 Days
• Field of Search: 250/208.1, 348/241, 348/243, 348/245
• US Class Current: 250/208.1
• 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 a plurality of dark pixel columns adjacent to a first side of said active area of pixels and in a plurality of dark pixel rows adjacent to a second side of said active area of pixels and to said plurality of dark pixel columns, the plurality of dark pixel rows having a width corresponding to a width of the active area of pixels and the plurality of dark pixel columns, wherein each row of the plurality of dark pixel rows includes a first half of only optically black pixels and a second half of only 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.

3. The imaging pixel array of claim 1, wherein the first and the second halves of adjacent dark pixel rows are located on alternating sides of a vertical axis marking the midpoint of the dark rows.

4. 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.

5. An imaging system, comprising:

an imager, comprising a pixel array, comprising;

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

a plurality of dark pixels arranged in a plurality of dark pixel columns adjacent to a first side of said active area of pixels and in a plurality of dark pixel rows adjacent to a second side of said active area of pixels and to said plurality of dark pixel columns, the plurality of dark pixel rows having a width corresponding to a width of the active area of pixels and the plurality of dark pixel columns, wherein each row of the plurality of dark pixels comprises optically black pixels and tied pixels; and

a black level calculating module that calculates a black level correction value based on the outputs of an equal number of the optically black pixels and the tied pixels.

6. The system of claim 5, wherein the black level calculating 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 comparing module to determine a difference between the average optically black pixel output and the average tied pixel output for each row; and

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

7. The system of claim 5, wherein the optically black pixels and tied pixels in the plurality of dark pixel rows are organized in a checkerboard pattern.

8. The system of claim 5, 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.

9. The system of claim 8, wherein the first and the second halves of pixels are located on alternating sides of adjacent dark pixel rows.

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

11. 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 a plurality of dark pixel columns adjacent to a first side of said active area of pixels and in a plurality of dark pixel rows adjacent to a second side of said active area of pixels and to said plurality of dark pixel columns, the plurality of dark pixel rows having a width corresponding to a width of the active area of pixels and the plurality of dark pixels columns, approximately half of said plurality of dark pixels in said dark pixel rows comprising optically black pixels and approximately half of said plurality of dark pixels in said dark pixel rows comprising tied pixels, wherein the dark pixel rows comprise optically black pixels and tied pixels arranged in a checkerboard pattern.