CFA correction for CFA images captured at partial resolution

• US 6,366,318 B1
• Filed: 03/27/1998
• Issued: 04/02/2002
• Est. Priority Date: 03/27/1998
• Status: Expired due to Term

• Current Assignee: Monument Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Eastman Kodak Company
• Inventors: Smith, Craig M., Adams, James E. Jr.
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): NGUYEN, LUONG TRUNG
• Application Number:
  US09/049,400
• Time in Patent Office: 1,467 Days
• Field of Search: 348/272, 348/273, 348/274, 348/275, 348/231, 348/280, 348/220, 358/525, 382/162, 382/166, 382/299, 382/300
• US Class Current: 348/272
• CPC Class Codes: G06T 3/4007 based on interpolation, e.g. bilinear interpolation image demosaicing G06T3/4015; edge-driven or edge-based scaling G06T3/403
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

In a method for generating color image signals derived from an array of color image pixels, the array of color pixels are subsampled in order to generate an array of subsampled color pixels. An array of new, evenly spaced color pixels are interpolated from the subsampled color pixels using surrounding pixels of the same color, and the color image signals derived from the array of new color pixels are subsequently processed, e.g., in a color filter array interpolation. By providing this correction in a preprocessing step, the rest of the normal image processing hardware or software may be used on the resultant subsampled CFA image without developing the characteristic blocky and wavy artifacts caused by an irregular subsampling pattern.

Claims

1. A method for generating color image signals derived from an array of color image pixels, said method comprising the steps of:

subsampling the array of color pixels in order to generate an array of subsampled color pixels, the pixels of the array of subsampled color pixels being unevenly spaced in a row direction and a column direction;

interpolating an array of new, evenly spaced color pixels from the subsampled color pixels, the pixels of the array of new color pixels being evenly spaced in the row direction and the column direction, a given pixel of the array of new color pixels being interpolated using surrounding pixels, of the same color as the given pixel, in the array of subsampled color pixels; and

processing the color image signals derived from the array of new color pixels.

2. A method as claimed in claim 1 wherein the step of interpolating comprises a bilinear interpolation.

3. A method for processing color image signals derived from an array of color image pixels arranged at a predetermined pixel spacing, said method comprising the steps of:

subsampling the array of color pixels in 2×

2 blocks of color pixels at half resolution in order to generate an array of subsampled color pixels, the pixels of the array of subsampled color pixels being unevenly spaced in a row direction and a column direction;

interpolating an array of new color pixels at half pixel spacing from the subsampled color pixels, the pixels of the array of new color pixels being evenly spaced in the row direction and the column direction, a given pixel of the array of new color pixels being interpolated using surrounding pixels, of the same color as the given pixel, in the array of subsampled color pixels; and

processing the color image signals derived from the array of new color pixels.

4. A method as claimed in claim 3 wherein the step of interpolating comprises a bilinear interpolation.

5. A method as claimed in claim 4 wherein the bilinear interpolation is weighted to produce half pixel spacing.

6. A method for processing color image signals derived from an array of color image pixels arranged at a predetermined pixel spacing, said method comprising the steps of:

capturing a color image through a color filter array to generate a corresponding array of color pixels;

subsampling the array of color pixels in 2×

2 blocks of color pixels at half resolution in order to generate an array of subsampled color pixels, the pixels of the array of subsampled color pixels being unevenly spaced in a row direction and a column direction;

interpolating an array of new color pixels at half pixel spacing from the subsampled color pixels, the pixels of the array of new color pixels being evenly spaced in the row direction and the column direction, a given pixel of the array of new color pixels being interpolated using surrounding pixels, of the same color as the given pixel, in the array of subsampled color pixels; and

processing the color image signals derived from the array of new color pixels.

7. A method as claimed in claim 6 wherein the step of interpolating comprises a bilinear interpolation.

8. A method as claimed in claim 7 wherein the bilinear interpolation is weighted to produce half pixel spacing.

9. A method as claimed in claim 6 wherein the color filter array is a Bayer color filter array.

10. A method as claimed in claim 6 wherein the step of processing comprises a color filter array interpolation.

11. A method as claimed in claim 6 wherein the step of processing includes one or more processing steps selected from the group consisting of noise reduction, white balance correction, color filter array interpolation, color correction, edge enhancement, and image compression.