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Spread spectrum digital screening

DC CAFC
  • US 5,689,623 A
  • Filed: 03/27/1995
  • Issued: 11/18/1997
  • Est. Priority Date: 03/27/1995
  • Status: Expired due to Term
First Claim
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1. A digital screening mask comprising:

  • a computer readable memory for storing data, wherein stored in the memory is a two dimensional array of optical density threshold values, each value being in a range between a minimum value and a maximum value, wherein a frequency domain plot of said array of threshold values is characterized by a function in magnitude independent of angle within a band of frequencies between a minimum frequency and a maximum frequency, the minimum frequency normally being imperceptible to humans and the maximum frequency being a frequency within the ability of a printing press to print.

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