Method and apparatus providing noise reduction while preserving edges for imagers

• US 20070127836A1
• Filed: 12/07/2005
• Published: 06/07/2007
• Est. Priority Date: 12/07/2005
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Subbotin, Igor
• Granted Patent: US 7,929,798 B2
• Time in Patent Office: Days
• US Class Current: 382/260
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 1/409 Edge or detail enhancement; Noise or error suppression

Abstract

A method of reducing noise in an image including steps for obtaining a first value for a target pixel, obtaining a respective second value for each neighboring pixel surrounding the target pixel and having the same color as the target pixel, for each neighboring pixel, comparing a difference between said first value and said second value to a threshold value, and replacing the first value with an average value obtained from the first value and at all second values from the neighboring pixels which have an associated difference which is less than or equal to the threshold value based on a result of the comparing step.

Claims

1. A method of reducing noise in an image comprising the steps of:

obtaining a first value for a target pixel;

obtaining a respective second value for each neighboring pixel surrounding said target pixel and having the same color as said target pixel;

for each neighboring pixel, comparing a difference between said first value and said second value to a threshold value; and

replacing said first value with an average value obtained from said first value and at all second values from said neighboring pixels which have an associated difference which is less than or equal to said threshold value based on a result of said comparing step.

2. The method of claim 1, wherein said first value is one of a red, green, or blue image signal value.

3. The method of claim 2, wherein said second values are the same type of red, green, or blue signal value as said first value.

4. The method of claim 1, wherein said first value is one of a luminance or chrominance image signal value.

5. The method of claim 4, wherein said second values are the same type of luminance or chrominance value as said first value.

6. The method of claim 1, wherein said threshold is based on at least one of an analog and digital gain.

7. The method of claim 1, wherein the method is implemented as a recursive method.

8. The method of claim 1, wherein the method is implemented as a non-recursive method.

9. The method of claim 1, wherein the method is implemented as a partially recursive method.

10. A method of reducing noise in an image comprising the steps of:

selecting a set of pixels surrounding an identified target pixel;

for each of said surrounding pixels of said set, calculating a respective difference value between said target pixel and said surrounding pixel;

for each of said surrounding pixels of said set, determining if said respective difference is at or below a predetermined level; and

substituting an average value as a value for the target pixel, wherein said average value is based on said target pixel and each pixel giving a respective difference value at or below said predetermined level.

11. The method of claim 10, wherein said first value is one of a red, green, or blue image signal value.

12. The method of claim 11, wherein said second values are the same type of red, green, or blue signal value as said first value.

13. The method of claim 10, wherein said first value is one of a luminance or chrominance image signal value.

14. The method of claim 13, wherein said second values are the same type of luminance or chrominance value as said first value.

15. The method of claim 10, wherein said threshold is based on at least one of an analog and digital gain.

16. The method of claim 10, wherein the method is implemented as a recursive method.

17. The method of claim 10, wherein the method is implemented as a non-recursive method.

18. The method of claim 10, wherein the method is implemented as a partially recursive method.

19. An imaging device comprising:

a pixel array comprising a plurality of pixels, each pixel outputting a signal representing an amount of light received; and

a pixel denoising circuit for denoising at least one identified pixel value,

wherein said pixel denoising circuit is configured to perform steps for;

obtaining a first value for a target pixel;

obtaining a respective second value for each neighboring pixel surrounding said target pixel and having the same color as said target pixel;

comparing a difference between said first value and said second value to a threshold value for each neighboring pixel; and

replacing said first value with an average value obtained from said first value and at all second values from said neighboring pixels which have an associated difference which is less than or equal to said threshold value based on a result of said comparing step.

20. The imaging device of claim 19, wherein said first value is one of a red, green, or blue image signal value.

21. The imaging device of claim 20, wherein said second values are the same type of red, green, or blue signal value as said first value.

22. The imaging device of claim 19, wherein said first value is one of a luminance or chrominance image signal value.

23. The imaging device of claim 22, wherein said second values are the same type of luminance or chrominance value as said first value.

24. The imaging device of claim 19, wherein said threshold is based on at least one of an analog and digital gain.

25. The imaging device of claim 19, wherein the steps are implemented recursively.

26. The imaging device of claim 19, wherein the steps are implemented non-recursively.

27. The method of claim 19, wherein the steps are implemented partially recursively.

28. An imaging device comprising:

a pixel array comprising a plurality of pixels, each pixel outputting a signal representing an amount of light received; and

a pixel denoising circuit for denoising at least one identified pixel value,

wherein said pixel denoising circuit is configured to perform steps for;

selecting a set of pixels surrounding an identified target pixel;

calculating a respective difference value between said target pixel and said surrounding pixel for each of said surrounding pixels of said set;

determining if said respective difference is at or below a predetermined level for each of said surrounding pixels of said set; and

substituting an average value as a value for the target pixel, wherein said average value is based on said target pixel and each pixel giving a respective difference value at or below said predetermined level.

29. The imaging device of claim 28, wherein said first value is one of a red, green, or blue image signal value.

30. The imaging device of claim 29, wherein said second values are the same type of red, green, or blue signal value as said first value.

31. The imaging device of claim 28, wherein said first value is one of a luminance or chrominance image signal value.

32. The imaging device of claim 31, wherein said second values are the same type of luminance or chrominance value as said first value.

33. The imaging device of claim 28, wherein said threshold is based on at least one of an analog and digital gain.

34. The imaging device of claim 28, wherein the steps are implemented recursively.

35. The imaging device of claim 28, wherein the steps are implemented non-recursively.

36. The imaging device of claim 28, wherein the steps are implemented partially recursively.

37. A processor having an associated program, said program enabling said processor to denoise an image by carrying out the acts of:

obtaining a first value for a target pixel;

obtaining a respective second value for each neighboring pixel surrounding said target pixel and having the same color as said target pixel;

for each neighboring pixel, comparing a difference between said first value and said second value to a threshold value; and

replacing said first value with an average value obtained from said first value and at all second values from said neighboring pixels which have an associated difference which is less than or equal to said threshold value based on a result of said comparing step.

38. The processor of claim 37, wherein said first value is one of a red, green, or blue image signal value.

39. The processor of claim 38, wherein said second values are the same type of red, green, or blue signal value as said first value.

40. The processor of claim 37, wherein said first value is one of a luminance or chrominance image signal value.

41. The processor of claim 40, wherein said second values are the same type of luminance or chrominance value as said first value.

42. The processor of claim 37, wherein said threshold is based on at least one of an analog and digital gain.

43. The processor of claim 37, wherein the program is implemented recursively.

44. The processor of claim 37, wherein the program is implemented non-recursively.

45. The processor of claim 37, wherein the program is implemented partially recursively.

46. A processor having an associated program, said program enabling said processor to denoise an image by carrying out the acts of:

selecting a set of pixels surrounding an identified target pixel;

for each of said surrounding pixels of said set, calculating a respective difference value between said target pixel and said surrounding pixel;

for each of said surrounding pixels of said set, determining if said respective difference is at or below a predetermined level; and

substituting an average value as a value for the target pixel, wherein said average value is based on said target pixel and each pixel giving a respective difference value at or below said predetermined level.

47. The processor of claim 46, wherein said first value is one of a red, green, or blue image signal value.

48. The processor of claim 47, wherein said second values are the same type of red, green, or blue signal value as said first value.

49. The processor of claim 46, wherein said first value is one of a luminance or chrominance image signal value.

50. The processor of claim 49, wherein said second values are the same type of luminance or chrominance value as said first value.

51. The processor of claim 46, wherein said threshold is based on at least one of an analog and digital gain.

52. The processor of claim 46, wherein the program is implemented recursively.

53. The processor of claim 46, wherein the program is implemented non-recursively.

54. The processor of claim 46, wherein the program is implemented partially recursively.

55. A carrier medium containing a program for operating a processor to denoise an image comprising the acts of:

obtaining a first value for a target pixel;

obtaining a respective second value for each neighboring pixel surrounding said target pixel and having the same color as said target pixel;

for each neighboring pixel, comparing a difference between said first value and said second value to a threshold value; and

replacing said first value with an average value obtained from said first value and at all second values from said neighboring pixels which have an associated difference which is less than or equal to said threshold value based on a result of said comparing step.

56. The carrier medium of claim 55, wherein said first value is one of a red, green, or blue image signal value.

57. The carrier medium of claim 56, wherein said second values are the same type of red, green, or blue signal value as said first value.

58. The carrier medium of claim 55, wherein said first value is one of a luminance or chrominance image signal value.

59. The carrier medium of claim 58, wherein said second values are the same type of luminance or chrominance value as said first value.

60. The carrier medium of claim 55, wherein said threshold is based on at least one of an analog and digital gain.

61. The carrier medium of claim 55, wherein the program is implemented recursively.

62. The carrier medium of claim 55, wherein the program is implemented non-recursively.

63. The carrier medium of claim 55, wherein the program is implemented partially recursively.

64. A carrier medium containing a program for operating a processor to denoise an image comprising the acts of:

selecting a set of pixels surrounding an identified target pixel;

for each of said surrounding pixels of said set, calculating a respective difference value between said target pixel and said surrounding pixel;

for each of said surrounding pixels of said set, determining if said respective difference is at or below a predetermined level; and

substituting an average value as a value for the target pixel, wherein said average value is based on said target pixel and each pixel giving a respective difference value at or below said predetermined level.

65. The carrier medium of claim 64, wherein said first value is one of a red, green, or blue image signal value.

66. The carrier medium of claim 65, wherein said second values are the same type of red, green, or blue signal value as said first value.

67. The carrier medium of claim 64, wherein said first value is one of a luminance or chrominance image signal value.

68. The carrier medium of claim 67, wherein said second values are the same type of luminance or chrominance value as said first value.

69. The carrier medium of claim 64, wherein said threshold is based on at least one of an analog and digital gain.

70. The carrier medium of claim 64, wherein the program is implemented recursively.

71. The carrier medium of claim 64, wherein the program is implemented non-recursively.

72. The carrier medium of claim 64, wherein the program is implemented partially recursively.