Patent ID: 7525702

Claim:
A method for correcting color distortions, comprising method operations of: scanning a calibration image comprised of a plurality of rows of patterns, wherein each row of patterns is shifted by a fraction of a pixel relative another row; calculating a color shift of a first color channel with respect to a second color channel along each pixel column of the calibration image, the color shift defining a correction for the color distortions includes: (a) selecting a first pixel group along a pixel row in the first color channel, the first pixel group including a pixel in a pixel column (b) calculating an interpolated color value for each pixel in the first group of pixels forming an interpolated pixel group. wherein the interpolated color value is representative of color values that are shifted by a fraction of a pixel relative to the pixel position; (c) selecting a second pixel group along the pixel row in the second color channel, the second pixel group corresponding to the pixels in the first group; (d) calculating differences in pixel color values between the interpolated pixel group and color values of the second pixel group; (e) repeating steps (a)-(d) among a plurality of pixel rows, each pixel group includes a pixel in the pixel column, wherein the color values in each row are shifted by the same fraction; (f) calculating a cost of the factional shift based on the differences calculated for the plurality of rows; (g) repeating steps (a)-(f) with a plurality of fractional shifts, to extract a fractional shift with a minimum cost; and (g) repeating steps (a)-(g) with a plurality of pixel columns; and applying the correction to subsequent scanned images.