Method and apparatus providing noise reduction while preserving edges for imagers

• US 8,218,898 B2
• Filed: 03/04/2011
• Issued: 07/10/2012
• Est. Priority Date: 12/07/2005
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Subbotin, Igor
• Primary Examiner(s): ENTEZARI, MICHELLE M
• Application Number:
  US13/040,648
• Publication Number:
  US 20110149122A1
• Time in Patent Office: 494 Days
• Field of Search: 382/242, 382/275, 382/272, 382/270, 348/E09.037, 348/250
• US Class Current: 382/275
• 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 a image comprising, for each pixel in the image, the steps of:

calculating a difference between a value of a target pixel and a value of each same-color neighboring pixel surrounding the target pixel, and

replacing the value of the target pixel with an average value calculated from the value of the target pixel along with values from each of the same-color neighboring pixels which have an associated difference that is less than or equal to a noise amplitude threshold,

wherein pixels are denoised sequentially, such that values of any previously de-noised, same-color neighboring pixels are used in replacing the value of the target pixel.

2. The method of claim 1, wherein the noise amplitude threshold is selected as a function of analog or digital gains applied to amplify pixels signals in the image.

3. The method of claim 1, wherein denoised values are first determined for each pixel in the image and then the calculating and replacing steps are performed for each pixel using the denoised values.

4. The method of claim 1, wherein the image is a bayer pattern image.

5. The method of claim 4, wherein the target pixels are divided into color channels and processed separately.

6. The method of claim 5, wherein there are four color channels:

red, blue, green pixels in red rows, and green pixels in blue rows.

7. A method of reducing noise in an image comprising, for each pixel in the image, the steps of:

selecting a set of pixels surrounding an identified target pixel;

for each same-color neighboring pixel of the set, calculating a respective difference value between said target pixel and the same-color neighboring pixel;

substituting an average value as a value for the target pixel, wherein said average value is based on the value of said target pixel along with values of each same-color neighboring pixel that has a respective difference value less than or equal to a noise amplitude threshold,

wherein pixels are denoised sequentially, such that the calculating, determining and substituting steps comprise using values of any previously de-noised same-color neighboring pixels.

8. The method of claim 7, wherein the image is a bayer pattern image.

9. The method of claim 8, wherein the set of pixels comprises the eight same-color pixels surrounding an identified target pixel.

10. The method of claim 8, wherein pixels in the image are divided into four color channels:

red, blue, green pixels in red rows, and green pixels in blue rows.

11. 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 denoising circuit for denoising an image comprising pixel signals obtained from the pixel array, the denoising circuit being configured to perform a denoising operation comprising;

calculating a difference between a value of a target pixel and a value of each same-color neighboring pixel surrounding the target pixel, and

replacing the value of the target pixel with an average value calculated from the value of the target pixel along with values from each of the same-color neighboring pixels which have an associated difference that is less than or equal to a noise amplitude threshold,

wherein the values of any previously de-noised, same-color neighboring pixels are used in replacing the value of the target pixel.

12. The imaging device of claim 11, wherein the noise amplitude threshold is selected as a function of analog or digital gains applied to amplify pixels signals in the image.

13. The imaging device of claim 11, wherein pixels are denoised sequentially.

14. The imaging device of claim 11, wherein denoised values are first determined for each pixel in the image and then the calculating and replacing steps are performed for each pixel using the denoised values.

15. The imaging device of claim 13, wherein the image is a bayer pattern image.

16. The imaging device of claim 15, wherein the target pixels are divided into color channels and processed separately.

17. The imaging device of claim 16, wherein there are four color channels:

red, blue, green pixels in red rows, and green pixels in blue rows.