Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1992-02-07
1994-07-19
Coles, Sr., Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358455, 358445, H04N 140
Patent
active
053314298
ABSTRACT:
An error diffusion, or adaptive dither method of producing halftone images includes an injected periodic screen pattern. The frequency of error diffusion dot formation is tuned to roughly match the frequency of the periodic screen pattern by adjustment of a hysteresis constant so that dot formation is phase and frequency locked to the phase and frequency of the periodic screen pattern. The resulting halftone, consisting of an orderly array of dots placed on a grid pattern at substantially the same angle and screen ruling as the periodic screen pattern, combines the advantages of both traditional screening such as precisely angled screens, and the advantages of error diffusion screening, such as better rejection of both internal and external moire artifacts. Any type of screen generation technique such as rational tangent, irrational tangent and rational supercell techniques can be used as a source of the periodic screen pattern.
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Coles Sr. Edward L.
Nguyen Madeleine
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