METHOD AND APPARATUS FOR IMAGE SIGNAL COLOR CORRECTION WITH REDUCED NOISE

• US 20090245632A1
• Filed: 03/31/2008
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Ovsiannikov, Ilia, Jerdev, Dmitri
• Granted Patent: US 8,411,943 B2
• Time in Patent Office: Days
• US Class Current: 382/167
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence

Abstract

A method and apparatus for applying color correction to image signals provides different color corrections depending on a characterization associated with a pixel signal being processed or the gain applied to the pixel signal such as a value of a pixel signal being processed. The color corrections may be configured such that darker pixels have less color correction applied to them.

Claims

1. A method of performing a color correction, comprising:

applying first color correction to a pixel signal if the pixel signal level is higher than a first pre-determined threshold; and

applying second color correction different from said first, to said pixel signal if the pixel signal level is lower than said first pre-determined threshold.

2. The method of claim 1 further comprising:

applying a third color correction to said pixel signal if the pixel signal level is lower than a second pre-determined threshold, wherein said second pre-determined threshold is lower than said first pre-determined threshold.

3. The method of claim 2 further comprising:

applying a fourth color correction to said pixel signal if the pixel signal level is lower than a third pre-determined threshold, wherein said third pre-determined threshold is lower than said second pre-determined threshold.

4. The method of claim 3, wherein said fourth color correction is a desaturated unity color correction.

5. The method of claim 3, wherein said third color correction is a combination of a desaturated unity color correction and a unity color correction.

6. The method of claim 3, wherein said second color correction is a combination of a unity color correction and said first color correction.

7. A method of performing a color correction on image signals, comprising:

applying a first color correction to a pixel signal if a value of the maximum of one of the components of an ROB triplet of the pixel signal is higher than a first predetermined threshold a, and

applying a second different color correction to said pixel signal a value of the maximum of one of the components of an RGB triplet of the pixel signal is lower than said first pre-determined threshold a.

8. The method of claim 7, where said first color correction is a color correction equation of the form:

9. The method of claim 7 further comprising:

applying a third color correction to said pixel signal if the maximum value of RGB triplet of the pixel signal m is lower than a second pre-determined threshold b, wherein said second pre-determined threshold b is lower than said first pre-determined threshold a.

10. The method of claim 9, wherein said second color correction is a color correction equation of the form:

B·

(1−

α

)+A·

α

, which is applied to said pixel signal,

where

11. The method of claim 9, wherein said third color correction is a color correction equation of the form

C·

(1−

α

)+B·

α

, which is applied to said pixel signal

where

12. The method of claim 10 further comprising:

applying a fourth color correction to said pixel signal if maximum value m is lower than a third pre-determined threshold c, wherein said third predetermined threshold c is lower than said second pre-determined threshold b.

13. The method of claim 12, wherein said fourth color correction is an equation of the form:

14. A method of performing a color correction, comprising:

applying a first color correction to a pixel signal if a characteristic associated with said pixel signal is higher than a first predetermined threshold; and

applying a second different color correction to said pixel signal if said characteristic is lower than said first pre-determined threshold.

15. The method of claim 14 wherein said characteristic associated with said pixel signal is a gain setting applied to said pixel signal.

16. The method of claim 15, further comprising:

applying a third color correction to said pixel signal if the characteristic is lower than a second pre-determined threshold, wherein said second pre-determined threshold is lower than said first pre-determined threshold.

17. The method of claim 16, further comprising:

applying a fourth color correction to said pixel signal if the characteristic is lower than a third pre-determined threshold, wherein said third pre-determined threshold is lower than said second pre-determined threshold.

18. An image processor for performing a color correction process on image signals, said image processor comprising;

a color correction matrix multiplier configured to apply a color correction matrix to an image signal; and

a circuit configured to determine a color correction matrix which is applied by said matrix multiplier in accordance with a value of said image signal, said color correction matrix mixer coupled to and configured to provide a determined color correction matrix to said color correction matrix multiplier.

19. The image processor of claim 18, wherein said color correction matrix mixer is configured to determine a first color correction matrix if the pixel signal is higher than a first pre-determined threshold, said color correction matrix mixer is configured to determine a second color correction matrix if the pixel signal is lower than said first pre-determined threshold.

20. The image processor of claim 19, wherein said color correction matrix mixer is configured to determine a third color correction matrix if the pixel signal is lower than said second predetermined threshold.

21. The image processor of claim 18, wherein said color correction matrix mixer is part of a camera system.

22. The image processor of claim 19, wherein said first color correction is

23. The image processor of claim 22, wherein said second color correction is B·

(1−

α

)+A·

α

,

where

24. The image processor of claim 23, wherein said third color correction is C·

(1−

α

)+B·

α

,

where

25. The image processor of claim 24, wherein said color correction matrix mixer is configured to determine a fourth color correction matrix if the pixel signal is lower than said third predetermined threshold, where said fourth color correction is