Saturday, March 26, 2011

RGB, YCC, and the importance of claim drafting

A key dispute in the Kodak ITC investigation is over the meaning of "at least three different colors" in element "b" of claim 15:

(b) a motion processor for generating from the captured images, a second number of color pixel values provided in a second color pattern having at least three different colors and representative of a series of motion images to be previewed, the second number of color pixel values being less than the first number of color pixel values, and the second color pattern being different from the first color pattern;

In essence, the claim describes capturing images with a high resolution pixel mosaic, a Bayer pattern with four sensors per pixel, half being green, for instance, and producing a motion stream of lower resolution images where each pixel is represented by three color values, such as red, green, and blue intensities ("RGB").

The filings imply strongly that Apple captures high resolution images with an RGB sensor, then produces lower resolution JPEG images for preview display.  A common first step in converting uncompressed RGB images to compressed JPEG images is to convert the color space of the image to YCbCr (or "YCC" as used in the filings).  This allows a lower compression ratio to be used on the very important luminance channel, and higher compression ratios to be used on the two chroma channels.

Do pixels represented in YCC color space have "three different colors"?  That's a key issue in this case.

From a imaging or color science perspective, the replacement of the claim phrase "having at least three different colors" with "each represented by at least three color coordinates" or "said pixels represented using at least three color channels," would have better encompassed the use of YCC or other luminance-chrominance color coordinate spaces.

With the use of the phrase "at least three different colors," the administrative law judge understandably gravitated toward an interpretation where each of the three "colors" is a "color" in layman's terms, namely "red," "green," or "blue."  It is this interpretation that Kodak is now trying to change when the case is reviewed.


Sources:

  • Final Initial and Recommended Determinations, ITC 337-703, Official Receive Date 3/08/2011
  • US ITC Filing, COMPLAINANT EASTMAN KODAK COMPANY'S PETITION FOR REVIEW OF THE FINAL INITIAL AND RECOMMENDED DETERMINATIONS, Filed February 17, 2011 by Eric C. Rusnak of K&L Gates, representing Eastman Kodak.
  • US Patent 6,292,218

 

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