INTERPOLATION FOR FOUR-CHANNEL COLOR FILTER ARRAY

• US 20100309347A1
• Filed: 06/09/2009
• Published: 12/09/2010
• Est. Priority Date: 06/09/2009
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Inventors: Pillman, Bruce H., Kumar, Mrityunjay, Adams, James E. JR., Hamilton, James A.
• Granted Patent: US 8,253,832 B2
• Time in Patent Office: Days
• US Class Current: 348/273
• CPC Class Codes: G06T 3/00 Geometric image transformations in the plane of the image
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/133 including elements passing panchromatic light, e.g. filters passing white light
• CPC Class Codes: H04N 25/135 based on four or more different wavelength filter elements

Abstract

A method is described for forming a full-color output image from a color filter array image comprising capturing an image using an image sensor including panchromatic pixels and color pixels having at least two different color responses, the pixels being arranged in a rectangular minimal repeating unit wherein for a first color response, the color pixels having the first color response alternate with panchromatic pixels in at least two directions, and for each of the other color responses there is at least one row, column or diagonal of the repeating pattern that only has color pixels of the given color response and panchromatic pixels. The method further comprising, computing an interpolated panchromatic image from the color filter array image; computing an interpolated color image from the color filter array image; and forming the full color output image from the interpolated panchromatic image and the interpolated color image.

Claims

1. A method of forming a full-color output image from a color filter array image having a plurality of color pixels having at least two different color responses and panchromatic pixels, comprising one or more processor(s) for providing the following:

a) capturing a color filter array image using an image sensor comprising a two dimensional array of light-sensitive pixels including panchromatic pixels and color pixels having at least two different color responses, the pixels being arranged in a rectangular minimal repeating unit having at least eight pixels and having at least two rows and two columns, wherein for a first color response, the color pixels having the first color response alternate with panchromatic pixels in at least two directions, and for each of the other color responses there is at least one row, column or diagonal of the repeating pattern that only has color pixels of the given color response and panchromatic pixels;

b) computing an interpolated panchromatic image from the color filter array image;

c) computing an interpolated color image from the color filter array image; and

d) forming the full color output image from the interpolated panchromatic image and the interpolated color image.

2. The method of claim 1 wherein step c) further includes using the interpolated panchromatic image in the process of computing the interpolated color image.

3. The method of claim 2 wherein the process of computing the interpolated color image includes forming an interpolated color difference image using color difference values formed from the interpolated panchromatic image and the color filter array image.

4. The method of claim 1 wherein step d) further includes

i) applying a high-pass filter to the interpolated panchromatic image to form a high frequency panchromatic image;

ii) applying a low-pass filter to the interpolated color image to form a low frequency color image; and

iii) merging the high frequency panchromatic image and the low frequency color image to form the full color output image.

5. The method of claim 1 wherein step d) further includes

i) performing a pyramid decomposition to the interpolated panchromatic image to form a panchromatic image pyramid;

ii) performing a pyramid decomposition to the interpolated color image to form a color image pyramid;

iii) merging the panchromatic image pyramid and the color image pyramid to form the output image pyramid; and

iv) forming the full color output image from the output image pyramid.

6. The method of claim 5 wherein step iii) includes applying a high-pass filter to each level of the panchromatic image pyramid to form a high frequency panchromatic image pyramid, applying a low-pass filter to each level of the color image pyramid to form a low frequency color image pyramid and merging each level of the high frequency panchromatic image pyramid and the low frequency color image pyramid to form the output image pyramid.

7. The method of claim 1 wherein the color pixels are red, green and blue pixels.

8. The image sensor of claim 1 wherein the minimal repeating unit has four rows and four columns, and wherein the first and third rows of the minimal repeating unit have a pixel sequence of green, panchromatic, green, panchromatic, the second row of the minimal repeating unit has a pixel sequence of panchromatic, red, panchromatic, panchromatic, and the fourth row of the minimal repeating unit has a pixel sequence of panchromatic, panchromatic, panchromatic, blue.

9. The method of claim 1 wherein the color pixels are cyan, magenta and yellow pixels.

10. The image sensor of claim 1 wherein the minimal repeating unit has four rows or four columns, and wherein the color pixels for each color response alternate with the panchromatic pixels for at least one row, column or diagonal of the repeating pattern.

11. A method of forming a full-color output image from a color filter array image having a plurality of color pixels having at least two different color responses and panchromatic pixels, comprising one or more processor(s) for providing the following:

a) capturing a color filter array image using an image sensor comprising a two dimensional array of light-sensitive pixels including panchromatic pixels and color pixels having at least two different color responses, the pixels being arranged in a rectangular minimal repeating unit having at least eight pixels and having at least two rows and two columns, wherein the color pixels of at least one color response alternate with panchromatic pixels in at least two directions, and wherein for each of the other color responses the color pixels for a given color response either alternate with panchromatic pixels in at least one direction or have at least two adjacent panchromatic pixels on both sides of the color pixels in at least two directions;

b) computing an interpolated panchromatic image from the color filter array image;

c) computing an interpolated color image from the color filter array image; and

d) forming the fill color output image from the interpolated panchromatic image and the interpolated color image.