Apparatus and method for improving image quality of image sensor

• US 8,199,216 B2
• Filed: 06/30/2009
• Issued: 06/12/2012
• Est. Priority Date: 11/01/2005
• Status: Active Grant

• Current Assignee: Intellectual Ventures II LLC (Intellectual Ventures LLC)
• Original Assignee: Intellectual Ventures II LLC (Intellectual Ventures LLC)
• Inventors: Hwang, Sung-Hyun
• Primary Examiner(s): SELBY, GEVELL V
• Application Number:
  US12/495,129
• Publication Number:
  US 20090262223A1
• Time in Patent Office: 1,078 Days
• Field of Search: 348/223.1, 348/224.1, 348/241
• US Class Current: 348/223.1
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

Provided are an apparatus and method for improving an image quality of an image sensor, capable of adaptively removing noise occurring in a de-mosaicking that is performed for generating three-channel data of R, G and B from a single channel pixel structure based on a bayer pattern. The apparatus includes a first converting unit for converting RGB color data into a YCbCr color data, the RGB color data being obtained from bayer data through a de-mosaicking, a noise removal unit for removing noise from a Cb and a Cr color data outputted from the first converting unit, and a second converting unit for converting the Cb and the Cr color data from the noise removal unit and a Y data from the first converting unit into the RGB color data.

Claims

1. An apparatus, comprising:

a color-space converter configured to receive RGB color data produced from image data of a plurality of adjacent pixels, and to output YCbCr color data for the plurality of adjacent pixels; and

an adaptive filter configured to;

receive Cb color data for the plurality of adjacent pixels;

determine a data range for the plurality of adjacent pixels based on the received Cb color data; and

filter the Cb color data that falls within the data range,

wherein the adaptive filter comprises;

a linear filter configured to smooth selected Cb color data; and

a data selector configured to select Cb color data for the linear filter that falls within the determined data range.

2. The apparatus of claim 1, wherein the adaptive filter is further configured to:

receive Cr color data for the plurality of adjacent pixels;

determine a second data range for the plurality of adjacent pixels based on the received Cr color data; and

filter Cr color data that falls within the second data range.

3. The apparatus of claim 1, further comprising a de-mosaicking unit configured to:

receive bayer data for the plurality of adjacent pixels; and

output the RGB color data for the plurality of adjacent pixels.

4. The apparatus of claim 1, wherein:

the adaptive filter further comprises an adaptive threshold generator configured to determine a threshold value based on the received Cb color data, and output an upper threshold and lower threshold of the data range;

the upper threshold corresponds to the threshold value added to the Cb color data for a central pixel from the plurality of adjacent pixels; and

the lower threshold corresponds to the threshold value subtracted from the Cb color data for the central pixel.

5. The apparatus of claim 1, wherein the adaptive filter is further configured to:

filter the Cb color data based on Gaussian weights in response to a select signal having a first state; and

filter the Cb color data based on unit weights in response to the select signal having a second state.

6. A method, comprising:

converting RGB color data associated with a plurality of adjacent pixels to YCbCr color data;

determining a data range for the plurality of adjacent pixels based on Cr color data for the plurality of adjacent pixels;

generating a threshold value based on the Cr color data;

adding the threshold value to Cr color data for a central pixel from the plurality of adjacent pixels to obtain an upper threshold of the data range;

subtracting the threshold value from the Cr color data for the central pixel to obtain a lower threshold of the data range; and

filtering Cr color data for the plurality of adjacent pixels that falls within the data range.

7. The method of claim 6, further comprising:

determining a second data range for the plurality of adjacent pixels based on the Cb color data for the plurality of adjacent pixels; and

filtering Cb color data for the plurality of adjacent pixels that falls within the second data range.

8. The method of claim 6, further comprising:

receiving bayer data for the plurality of adjacent pixels; and

generating the RGB color data for the plurality of adjacent pixels based on the bayer data.

9. The method of claim 6, wherein said filtering Cr color data comprises:

selecting Cr color data of the plurality of adjacent pixels that falls between the upper threshold and the lower threshold; and

filtering the selected Cr color data.

10. The method of claims 6, wherein said filtering Cr color data comprises:

selecting Cr color data that have a predetermined relationship to the upper threshold and the lower threshold; and

smoothing only the Cr color data that were selected.

11. The method of claim 6, wherein said filtering Cr color data comprises:

smoothing the Cr color data based on Gaussian weights in response to a first signal; and

smoothing the Cr color data based on unit weights in response to a second signal.

12. A method, comprising:

converting first, second, and third color component data associated with a plurality of adjacent pixels to luma, first chroma, and second chroma component data for the plurality of adjacent pixels;

determining a data range based on the first chroma component data; and

filtering the first chroma component data that have a predetermined relationship to the data range;

wherein said filtering first chroma component data comprises;

selecting first chroma component data that have a predetermined relationship to the data range; and

smoothing only the first chroma component data that were selected.

13. The method of claim 12, further comprising:

determining a second data range based on the second chroma component data; and

filtering the second chroma component data that have a predetermined relationship to the second data range.

14. The method of claim 13, further comprising:

receiving bayer data for the plurality of adjacent pixels; and

generating the first, the second, and the third color component data based on the bayer data.

15. The method of claim 12, wherein:

the first, the second, and the third color component data respectively correspond to R, G, and B color data.

16. The method of claim 12, wherein:

the luma, the first chroma, and the second chroma component data respectively correspond to Y, Cr, and Cb color data.

17. A method, comprising:

converting first, second, and third color component data associated with a plurality of adjacent pixels to luma, first chroma, and second chroma component data for the plurality of adjacent pixels;

determining a data range based on the first chroma component data; and

filtering the first chroma component data that have a predetermined relationship to the data range;

wherein said filtering first chroma component data comprises;

smoothing the first chroma component data based on Gaussian weights in response to a first signal; and

smoothing the first chroma component data based on unit weights in response to a second signal.

18. The method of claim 17, further comprising:

receiving bayer data for the plurality of adjacent pixels; and

generating the first, the second, and the third color component data based on the bayer data.

19. The method of claim 17, wherein:

the first, the second, and the third color component data respectively correspond to R, G, and B color data; and

the luma, the first chroma, and the second chroma component data respectively correspond to Y, Cr, and Cb color data.

20. An image sensor, comprising:

a pixel array arranged in a bayer pattern and configured to output bayer data;

a de-mosaicking unit configured to convert the bayer data to first color-space data comprising first, second, and third color component data;

a color-space converter unit configured to convert the first color-space data to second color-space data comprising luma, first chroma, and second chroma component data; and

an adaptive filter configured to determine a data range for a plurality of adjacent sensor pixels of the pixel array based on the first chroma component data, and to filter the first chroma component data that have a predetermined relationship to the data range;

wherein said adaptive filter is further configured to;

select first chroma component data that have a predetermined relationship to the data range; and

smooth only the first chroma component data that were selected.

21. The image sensor of claim 20, wherein the adaptive filter is further configured to:

determine a second data range based on the second chroma component data; and

filter the second chroma component data that have a predetermined relationship to the second data range.

22. The image sensor of claim 20, wherein:

the first, the second, and the third color component data respectively correspond to R, G, and B color data; and

the luma, the first chroma, and the second chroma respectively correspond to Y, Cr, and Cb color data.

23. An image sensor, comprising:

a pixel array arranged in a bayer pattern and configured to output bayer data;

a de-mosaicking unit configured to convert the bayer data to first color-space data comprising first, second, and third color component data;

a color-space converter unit configured to convert the first color-space data to second color-space data comprising luma, first chroma, and second chroma component data; and

an adaptive filter configured to determine a data range for a plurality of adjacent sensor pixels of the pixel array based on the first chroma component data, and to filter the first chroma component data that have a predetermined relationship to the data range;

wherein the adaptive filter is further configured to;

smooth the first chroma component data based on Gaussian weights in response to a first signal; and

smooth the first chroma component data based on unit weights in response to a second signal.

24. The image sensor of claim 23, wherein the adaptive filter is further configured to:

determine a second data range based on the second chroma component data; and

filter the second chroma component data that have a predetermined relationship to the second data range.

25. The image sensor of claim 23, wherein:

the first, the second, and the third color component data respectively correspond to R, G, and B color data; and

the luma, the first chroma, and the second chroma respectively correspond to Y, Cr, and Cb color data.