Method and device for determining the color appearance of color overprints
First Claim
1. A method for determining respective sets of np parameters that spectrally characterize one or more colorants in order to predict the color of an overprint of the colorants printed in an order of printing at a set of respective coverage percentages on a substrate of a substrate type using a printing technique, each of the colorants defined by a respective recipe of one or more basic colorants, the method comprising, for a particular colorant of the colorants:
- (a) for each basic colorant of the respective recipe defining the particular colorant;
(i) making a selected number of sets of prints of the basic colorant on said selected number of respective substrates of the same substrate type, a set of prints comprising prints of the basic colorant on the respective substrate at a range of coverage percentages of interest, the selected number of prints at any particular coverage percentage being on backgrounds of said selected number of different background colors, said selected number dependent on np ;
(ii) measuring the spectra of the prints of the selected number of sets of prints and the spectra of each of the different background colors; and
(b) determining from the recipe and from the measured spectra, the set of np colorant parameters of the particular colorant as a function of the coverage percentage and of wavelength, the colorant parameters substantially independent of the color of the substrate.
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Abstract
A method and apparatus for determining a small number of parameters that spectrally characterize colorants by a small number of parameters and for using such colorant parameters to predict the spectral reflection or transmission characteristics of such colorants when laid on top of one another, either on an opaque, transparent or semitransparent carrier of a particular type, each colorant laid with a certain coverage percentage, for example, dot percentage in the case of offset printing, the colorant parameters of any colorant being substantially independent of the color of the substrate. The method involves making measurements of sets prints of varying coverage percentages of a colorant on a number of backgrounds, and solving the resulting set of equations for the colorant. Colorants that are defined by a recipe of basic colorants can be characterized from measurements on prints of the basic colorants.
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Citations
50 Claims
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1. A method for determining respective sets of np parameters that spectrally characterize one or more colorants in order to predict the color of an overprint of the colorants printed in an order of printing at a set of respective coverage percentages on a substrate of a substrate type using a printing technique, each of the colorants defined by a respective recipe of one or more basic colorants, the method comprising, for a particular colorant of the colorants:
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(a) for each basic colorant of the respective recipe defining the particular colorant; (i) making a selected number of sets of prints of the basic colorant on said selected number of respective substrates of the same substrate type, a set of prints comprising prints of the basic colorant on the respective substrate at a range of coverage percentages of interest, the selected number of prints at any particular coverage percentage being on backgrounds of said selected number of different background colors, said selected number dependent on np ; (ii) measuring the spectra of the prints of the selected number of sets of prints and the spectra of each of the different background colors; and (b) determining from the recipe and from the measured spectra, the set of np colorant parameters of the particular colorant as a function of the coverage percentage and of wavelength, the colorant parameters substantially independent of the color of the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 49)
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37. An apparatus for determining the color of an overprint of one or more colorants each colorant printed in an order at a respective coverage percentage on a substrate of a substrate type, each colorant defined by a set of np colorant parameters that are a function of the coverage percentage the colorant is printed on, and of wavelength, the colorant parameters substantially independent of the color of the substrate the colorant is printed on, np being at least 2 for a non-scattering colorant and at least 3 for a scattering colorant, the set of colorant parameters defined by a relationship relating the spectrum of a print of a selected colorant at a selected coverage percentage on a base substrate to the spectrum of the base substrate and the set of colorant parameters of the selected colorant at the selected coverage percentage, the apparatus comprising:
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(a) a first memory for storing a spectrum, said first memory initially storing the spectrum of the substrate; (b) a logic unit, the logic unit including a set of one or more inputs, the inputs coupled to signals specifying a coverage percentage, a second memory for storing the values of the colorant parameters of at least one of the colorants at a selected set of coverage percentages, a set of one or more multidimensional outputs, each multidimensional output generating the values of the colorant parameters at the coverage percentage of a respective input of the set of inputs, (c) a combiner unit having a first input coupled to the first memory, the combiner unit coupled to said set of outputs of the logic unit for determining as an output the spectrum of an overprint essentially according to the relationship. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 50)
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Specification