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Method and apparatus for implementing accurate angle screens

  • US 5,426,519 A
  • Filed: 08/25/1994
  • Issued: 06/20/1995
  • Est. Priority Date: 08/25/1994
  • Status: Expired due to Fees
First Claim
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1. A color document printing system for eliminating moire in printed output, the color document including a plurality of color separations wherein each separation is defined with a set of image signals representing optical density with m possible density levels, comprising:

  • a printer, capable of rendering density with n density levels, adapted to print the color separations at distinct spatial resolutions, so that when the color separations are superposed on a substrate, a selected color is defined;

    a source of image signals describing the color document with a plurality of color separations, each image signal representing optical density as one of m levels for a discrete area of a color separation;

    a spatial resolution scaler, operatively connected to said source of image signals;

    a first halftone processor, operatively connected to said spatial resolution scaler, for reducing the number of levels m representing optical density in a subset of the color separations to a number of levels n representing optical density, said processor generating a first periodic pattern at a first spatial resolution;

    a second halftone processor, operatively connected to said spatial resolution scaler, for reducing the number of levels m representing optical density in at least one remaining color separation to a number of levels n representing optical density, said processor generating a second periodic pattern at a second spatial resolution; and

    a video processor directing the distinct spatial resolution signals processed at each halftone processor to said printer to print the processed color image.

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