N-color printing with hexagonal rosettes
First Claim
Patent Images
1. An image forming method for digitally reproducing a moiré
- -free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, N>
4, the method comprising;
using a color halftoning screening apparatus to perform;
defining rosette fundamental frequency vectors (VR1, VR2) that satisfy a length and sum requirement to meet visual acceptability standards according to |VR1|>
fmin, |VR2|>
fmin, and |VR1±
VR2|>
fmin;
defining N halftone screens for colorants i=1, N, respectively possessing first and second frequency vectors (Vi1, Vi2), where no two screens possess identical fundamental frequency vector pairs;
selecting fundamental frequency vectors for the N halftone screens according to;
(Vi1, Vi2)=(mi1VR1+mi2VR2, ni1VR1+ni2VR2) for integer m'"'"'s and n'"'"'s, where at least one fundamental frequency vector or its conjugate satisfies one of the following;
Vik=VR1, Vik=VR2, and |Vik|>
2max [|VR1|, |VR2|];
such that the set of N different halftone screens used in combination produces a moiré
-free halftone output; and
using said N halftone screens, as further specified by said selected fundamental frequency vectors, in an image forming apparatus for digital reproduction of a moiré
-free color halftone image.
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Abstract
What is provided herein are systems and methods for digitally reproducing a moiré-free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, where N>4. Also disclosed is an enhanced color halftoning screening apparatus for reproducing a moiré-free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, N>4. Further disclosed are embodiments for generating a plurality of non-orthogonal halftone screen outputs for moiré-free enhanced color halftoning.
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Citations
25 Claims
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1. An image forming method for digitally reproducing a moiré
- -free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, N>
4, the method comprising;using a color halftoning screening apparatus to perform; defining rosette fundamental frequency vectors (VR1, VR2) that satisfy a length and sum requirement to meet visual acceptability standards according to |VR1|>
fmin, |VR2|>
fmin, and |VR1±
VR2|>
fmin;defining N halftone screens for colorants i=1, N, respectively possessing first and second frequency vectors (Vi1, Vi2), where no two screens possess identical fundamental frequency vector pairs; selecting fundamental frequency vectors for the N halftone screens according to;
(Vi1, Vi2)=(mi1VR1+mi2VR2, ni1VR1+ni2VR2) for integer m'"'"'s and n'"'"'s, where at least one fundamental frequency vector or its conjugate satisfies one of the following;
Vik=VR1, Vik=VR2, and |Vik|>
2max [|VR1|, |VR2|];
such that the set of N different halftone screens used in combination produces a moiré
-free halftone output; andusing said N halftone screens, as further specified by said selected fundamental frequency vectors, in an image forming apparatus for digital reproduction of a moiré
-free color halftone image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- -free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, N>
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11. A method for generating a plurality of non-orthogonal halftone screen outputs for moiré
- -free enhanced color halftoning, the method comprising;
using a color halftoning screening apparatus to perform; defining rosette fundamental frequency vectors (VR1, VR2) that satisfy a length and a sum requirement to meet visual acceptability standards according to;
|VR1|>
fmin, |VR2|>
fmin, and |VR1±
VR2|>
fmin; and
,specifying a first and a second color halftone screen fundamental frequency vector for each of N halftone screens, N>
4 according to;
(Vi1, Vi2)=(mi1VR1+mi2VR2, ni1VR1+ni2VR2) for integer m'"'"'s and n'"'"'s, where at least one of the fundamental frequency vectors or its conjugate must also occur off of a second-order spectral hexagon which connects frequency components that lie just outside of a first-order spectral hexagon; andusing said N halftone screens, as further specified by said first and second fundamental frequency vectors, in an image forming apparatus for digital reproduction of a moiré
-free color halftone image. - View Dependent Claims (12, 13, 14, 15)
- -free enhanced color halftoning, the method comprising;
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16. A color halftoning screening apparatus for reproducing a moiré
- -free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, N>
4, the apparatus comprising;rosette fundamental frequency vectors VR1, VR2 that satisfy a length and sum requirement to meet visual acceptability standards according to |VR1|>
fmin, |VR2|>
fmin, and |VR1±
VR2|>
fmin;N halftone screens for colorants i=1, N, respectively possessing first and second frequency vectors (Vi1, Vi2), where no two screens possess identical fundamental frequency vector pairs; and fundamental frequency vectors for the N halftone screens according to (Vi1, Vi2)=(mi1VR1+mi2VR2, ni1VR1+ni2VR2) for integer m'"'"'s and n'"'"'s, where at least one fundamental frequency vector or its conjugate also satisfies one of the following;
Vik=VR1, Vik=VR2, and |Vik|>
2max [|VR1|, |VR2|]. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
- -free color halftone image using an enhanced halftone screen set consisting of a halftone screen for each of N colorants, N>
Specification