System and method for adaptive local white balance adjustment

• US 8,013,907 B2
• Filed: 04/08/2008
• Issued: 09/06/2011
• Est. Priority Date: 04/08/2008
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Xiong, Weihua, Kuang, Jiangtao
• Primary Examiner(s): Ometz; David
• Assistant Examiner(s): Trehan; Akshay
• Application Number:
  US12/099,351
• Publication Number:
  US 20090251561A1
• Time in Patent Office: 1,246 Days
• Field of Search: 348/223.1, 348/655, 348/E9.051, 382/167
• US Class Current: 348/223.1
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control

Abstract

The disclosure describes embodiments of an apparatus comprising an image sensor including a pixel array having a plurality of pixels and an automatic white balance (AWB) circuit coupled to the pixel array. The AWB circuit is used to determine a local white balance component for each pixel, determine a global white balance component for each pixel, and apply a white balance adjustment to each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component. The disclosure also describes embodiment of a process including receiving image data from each pixel in a pixel array, determining a local white balance component for the image data from each pixel, determining a global white balance component for the image data from each pixel, and applying a white balance adjustment to the image data from each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component. Other embodiments are also disclosed and claimed.

Claims

1. An apparatus comprising:

an image sensor including a pixel array having a plurality of pixels;

an automatic white balance (AWB) circuit coupled to the pixel array to;

determine a local white balance component for each pixel using a spatial-domain function and an intensity-domain function, wherein the spatial-domain function decreases the weight of pixels within a local domain that are spatially distant from the pixel to which the white balance adjustment is being applied,

determine a global white balance component for each pixel, and

apply a white balance adjustment to each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component.

2. The apparatus of claim 1 wherein the AWB circuit determines local white balance components for each red, green, and blue value output by each pixel.

3. The apparatus of claim 1 wherein the AWB circuit determines the local white balance component for a particular pixel using data from other pixels within a local domain surrounding the particular pixel.

4. The apparatus of claim 1 wherein the AWB circuit determines the global white balance component for a particular pixel using image data from pixels in a global domain, the global domain being different than the local domain.

5. The apparatus of claim 4 wherein the global domain comprises all active pixels in the pixel array.

6. The apparatus of claim 1 wherein the spatial-domain function is a Gaussian kernel function.

7. The apparatus of claim 1 wherein the combination of the local white balance component and the global white balance component is a linear combination.

8. An apparatus comprising:

an image sensor including a pixel array having a plurality of pixels;

an automatic white balance (AWB) circuit coupled to the pixel array to;

determine a local white balance component for each pixel using a spatial-domain function and an intensity-domain function, wherein the intensity-domain function decreases the weight of pixels within a local domain whose intensity differs greatly from the intensity of the pixel to which the white balance adjustment is being applied,

determine a global white balance component for each pixel, and

apply a white balance adjustment to each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component.

9. The apparatus of claim 8 wherein the AWB circuit determines local white balance components for each red, green, and blue value output by each pixel.

10. The apparatus of claim 8 wherein the AWB circuit determines the local white balance component for a particular pixel using data from other pixels within a local domain surrounding the particular pixel.

11. The apparatus of claim 8 wherein the AWB circuit determines the global white balance component for a particular pixel using image data from pixels in a global domain, the global domain being different than the local domain.

12. The apparatus of claim 11 wherein the global domain comprises all active pixels in the pixel array.

13. The apparatus of claim 8 wherein the intensity-domain function is a Gaussian kernel function.

14. The apparatus of claim 8 wherein the combination of the local white balance component and the global white balance component is a linear combination.

15. A system comprising:

an optical element;

an image sensor coupled to the optical element, the image sensor comprising a pixel array including a plurality of pixels;

an automatic white balance (AWB) circuit coupled to the pixel array to;

determine a local white balance component for each pixel using a spatial-domain function and an intensity-domain function, wherein the spatial-domain function decreases the weight of pixels within a local domain that are spatially distant from the pixel to which the white balance adjustment is being applied,

determine a global white balance component for each pixel, and

apply a white balance adjustment to each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component; and

one or both of a display unit and a storage unit coupled to the digital signal processor.

16. The system of claim 15 wherein the AWB circuit is a circuit within the image sensor.

17. The system of claim 15 wherein the AWB circuit is a digital signal processor coupled to the image sensor.

18. The system of claim 15 wherein the AWB circuit determines local white balance components for each red, green, and blue value output by each pixel.

19. The system of claim 15 wherein the AWB circuit determines the local white balance component for a particular pixel using data from other pixels within a local domain surrounding the particular pixel.

20. The system of claim 15 wherein the AWB circuit determines the global white balance component for a particular pixel using image data from pixels in a global domain, the global domain being different than the local domain.

21. The system of claim 20 wherein the global domain comprises all active pixels in the pixel array.

22. The system of claim 15 wherein the spatial-domain function is a Gaussian kernel function.

23. The system of claim 15 wherein the combination of the local white balance component and the global white balance component is a linear combination.

24. A system comprising:

an optical element;

an image sensor coupled to the optical element, the image sensor comprising a pixel array including a plurality of pixels;

an automatic white balance (AWB) circuit coupled to the pixel array to;

determine a local white balance component for each pixel using a spatial-domain function and an intensity-domain function, wherein the intensity-domain function decreases the weight of pixels within a local domain whose intensity differs greatly from the intensity of the pixel to which the white balance adjustment is being applied,

determine a global white balance component for each pixel, and

apply a white balance adjustment to each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component; and

one or both of a display unit and a storage unit coupled to the digital signal processor.

25. The system of claim 24 wherein the AWB circuit is a circuit within the image sensor.

26. The system of claim 24 wherein the AWB circuit is a digital signal processor coupled to the image sensor.

27. The system of claim 24 wherein the AWB circuit determines local white balance components for each red, green, and blue value output by each pixel.

28. The system of claim 24 wherein the AWB circuit determines the local white balance component for a particular pixel using data from other pixels within a local domain surrounding the particular pixel.

29. The system of claim 24 wherein the AWB circuit determines the global white balance component for a particular pixel using image data from pixels in a global domain, the global domain being different than the local domain.

30. The system of claim 29 wherein the global domain comprises all active pixels in the pixel array.

31. The system of claim 24 wherein the intensity-domain function is a Gaussian kernel function.

32. The system of claim 24 wherein the combination of the local white balance component and the global white balance component is a linear combination.

33. A process comprising:

receiving image data from each pixel in a pixel array;

determining a local white balance component for the image data from each pixel using a spatial-domain function and an intensity-domain function, wherein the spatial-domain function decreases the weight of pixels within a local domain that are spatially distant from the pixel to which the white balance adjustment is being applied;

determining a global white balance component for the image data from each pixel; and

applying a white balance adjustment to the image data from each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component.

34. The process of claim 33 wherein determining a local white balance component comprises determining local white balance components for each red, green, and blue value output by each pixel.

35. The process of claim 33 wherein determining a local white balance component comprises determining the local white balance component for a particular pixel using data from other pixels within a local domain surrounding the particular pixel.

36. The process of claim 33 wherein determining a global white balance component comprises using image data from pixels in a global domain, the global domain being different than the local domain.

37. The process of claim 36 wherein the global domain comprises all active pixels in the pixel array.

38. The process of claim 33 wherein the spatial-domain function is a Gaussian kernel function.

39. The process of claim 33 wherein the combination of the local white balance component and the global white balance component is a linear combination.

40. A process comprising:

receiving image data from each pixel in a pixel array;

determining a local white balance component for the image data from each pixel using a spatial-domain function and an intensity-domain function, wherein the intensity-domain function decreases the weight of pixels within a local domain whose intensity differs greatly from the intensity of the pixel to which the white balance adjustment is being applied;

determining a global white balance component for the image data from each pixel; and

applying a white balance adjustment to the image data from each pixel, the applied white balance adjustment comprising a combination of the local white balance component and the global white balance component.

41. The process of claim 40 wherein determining a local white balance component comprises determining local white balance components for each red, green, and blue value output by each pixel.

42. The process of claim 40 wherein determining a local white balance component comprises determining the local white balance component for a particular pixel using data from other pixels within a local domain surrounding the particular pixel.

43. The process of claim 40 wherein determining a global white balance component comprises using image data from pixels in a global domain, the global domain being different than the local domain.

44. The process of claim 43 wherein the global domain comprises all active pixels in the pixel array.

45. The process of claim 43 wherein the intensity-domain function is a Gaussian kernel function.

46. The process of claim 43 wherein the combination of the local white balance component and the global white balance component is a linear combination.