Processing color and panchromatic pixels

1. A method for forming a digital color image comprising:

capturing an image using a solid state image sensor having a pixel array that includes both panchromatic pixels and color pixels, wherein the color pixels correspond to at least two color photoresponses and wherein the pixel array is made up of a plurality of tiled minimal repeating units, each minimal repeating unit including a plurality of cells, each cell including at least two panchromatic pixels and at least two pixels having the same color photoresponse;

grouping signals from all of the color pixels in each cell into one or more group signals to increase color photosensitivity, wherein all pixels whose signals are grouped into a group signal have the same color photoresponse;

combining the group signals to form a low-resolution digital color image having a first resolution based on the resolution of the cells;

using second signals from the individual panchromatic pixels to provide a high-resolution digital panchromatic image having a second resolution based on the resolution of the pixels in the image sensor; and

combining the high-resolution digital panchromatic image and the low-resolution digital color image to provide a high-resolution digital color image.

2. The method of claim 1 , wherein each minimal repeating unit includes at least twelve pixels.

3. The method of claim 2 , wherein the cells are non-overlapping cells.

4. A method for processing a color image captured by an image sensor to permit the effective reproduction of a color image captured under low lighting conditions, comprising:

(a) using a solid state image sensor to capture an image, the image sensor having a pixel array including both panchromatic pixels and color pixels, wherein the color pixels correspond to at least two color photoresponses, and wherein the pixel array is made up of a plurality of tiled minimal repeating units, each minimal repeating unit including a plurality of cells, each cell including at least two panchromatic pixels and at least two pixels having the same color photoresponse;

(b) grouping signals from all of the color pixels within each cell into one or more group signals to increase color photosensitivity, wherein all pixels whose signals are grouped into a group signal have the same color photoresponse;

(c) combining the group signals to form a low-resolution digital color image having a first resolution based on the resolution of the cells;

(d) using second signals from the individual panchromatic pixels to provide a high-resolution digital panchromatic image having a second resolution based on the resolution of the pixels in the image sensor; and

(e) combining the low-resolution digital color image and the high-resolution digital panchromatic image to produce a high-resolution digital color image.

5. The method of claim 4 , wherein element (b) includes summing the first signals from the plurality of pixels having the same color photoresponse in each group.

6. The method of claim 4 , wherein element (e) includes:

summing pixel values from the high-resolution panchromatic image to produce a low-resolution panchromatic image having the first resolution;

using the low-resolution panchromatic image and the low-resolution color image to produce a color difference image; and

using the color difference image and the high-resolution panchromatic image to produce a high-resolution color image.

7. The method of claim 5 wherein element (e) includes:

summing pixel values from the high-resolution panchromatic image to produce a low-resolution panchromatic image having the first resolution;

using the low-resolution panchromatic image and the low-resolution partial color image to produce a color difference image; and

using the color difference image and the high-resolution panchromatic image to produce a high-resolution color image.