Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1999-07-26
2002-11-19
Wallerson, Mark (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S518000, C358S525000
Reexamination Certificate
active
06483607
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computerized color graphics, color reproduction, and electronic printing systems. In particular, the present invention relates to a method and apparatus for characterizing colorants such as inks and predicting the color appearance of placing one or more colorant layers on top of a substrate such as paper or film as occurs, for example, in printing a page and photography.
BACKGROUND OF THE INVENTION
Computerized color graphics systems and electronic printing systems are known in the art. Typically, they enable a user to produce a color image (any visual two-dimensional pattern including text, graphic line art, continuous tone images, etc.), and from that image to produce a picture which can be printed via a color reproduction system, for example, by producing color separation plates for offset printing. There has been much effort in the past to develop ways to accurately predict or simulate the appearance of such images when printed on a substrate, for example paper or film, using a number of colorants, such as inks, the prediction carried out without actually printing the images.
Printing may be carried out using halftoning, also called screening, which is the process of creating the illusion of a continuous tone (“CT,” “contone”) image using an output (e.g., printing) device capable only of binary output (ink deposited or not deposited at any location on a substrate). For color printing, several images (“separations”) are produced in the primary colorants (typically inks) used to print in color, and printed over each other in a press. For typical four color printing, four images are produced in cyan (“C”), magenta (“M”), yellow (“Y”) and black (“K”), and each of these images are halftoned. Usually, digital halftoning is used together with an imagesetter, laser printer, ink jet printer, digital film recorder, or other recorder output device.
It is desirable to be able to calculate accurately how a picture will look when one prints an image, including a halftoned continuous tone color image, with a certain technique on a certain substrate using a certain set of colorants (e.g., inks). A method of predicting the color appearance can be used for example to display a simulation of the color appearance on a computer display, or to print a simulation of the color appearance on a more easily accessible and cheaper printer as a proof of what is to be printed finally in production.
It is desirable to do this for both reflection printing on an opaque substrate, and transmission imaging on a transparent substrate.
By accurately calculating we mean a maximum deviation between predicted color and actual color of the order of 5 CIELAB Delta E units, and an average deviation of about 2 CIELAB Delta E units.
PRIOR ART METHODS
Various methods are known for calculating the color resulting from superimposing a set of colorant layers on a substrate. These methods can be divided in two groups. The first group are characterized by requiring printing and measuring a relatively large number of overprints of the colorants. That is, this group includes methods that for a particular set of colorants, a particular printing technique (e.g., offset printing on a particular imagesetter), a particular substrate type (e.g., paper, or film for a photographic transparency or print, textile, sheet of plastic, etc.), a particular substrate color (e.g., the color of the paper, or of the transparent film in the case of a transparency, or of the textile, or of the plastic sheet, etc.) and a particular order of printing the colorants, involve printing a relatively large number of overprints of the colorants in the set, for example as patches. These patches are measured with a spectrophotometer or calorimeter and the measurements are used to calculate any overprint of colorants in the set using mathematical techniques, for example, interpolation. If carried out well and carefully, these methods can lead to accurate results. Modem color management techniques such as COLORSYNC™ (Apple Computer, Inc., Cupertino, Calif.) and the methods promoted by the International Color Consortium (ICC, see http://www.color.org) use such techniques. While these techniques can produce accurate results, and also work for halftone images, there are several drawbacks with such methods. One is that a large number of color patches of overprints need to be made. For example, the IT8.7.3 chart (American National Standards Institute [ANSI] Committee IT8 for Digital Data Exchange Standards) contains nearly a thousand patches for a four color output. Hence it is very difficult to characterize sets of more than four colorants, for example printing with six or seven colors (“HI-FI” printing including PANTONE® Hexachrome from Pantone, Inc., Carlstadt, N.J.). There also are applications where inks other than cyan, magenta, yellow and black need to be used. Another drawback is that a set of patches will only be useful for accurately calculating overprints using the particular colorants and the particular colorant printing order used in the patches. Changing one colorant in the colorant set or changing the order of overprinting typically requires redoing the whole job of printing the set of patches.
An additional problem occurs when using such characterizations with more than four inks in a typical modem color management workflow, such as the ICC workflow. The ICC standard uses look up tables and interpolation to predict the CIELAB values of a particular output device. The number of nodes in these lookup tables increases exponentially with the number of inks, and the amount of computer resources becomes too high to be feasible.
Also included in this first group of known methods are those that use the well known Neugebauer equations to predict the color of an overprint of colorants, and their derivative based on Yule-Nielsen and spectral Neugebauer equations (See H. E. J. Neugebauer: “Die theoretischen Grundlagen des Mehrfarbenbuchdrucks”,
Zeitschrift fur wissenschaftliche Photographie, Photophysik und Photochemie
, Band 36, Heft 4, April 1937; J. S. Arney, C. D. Arney:” Modeling the Yule-Nielsen Halftone effect,” Journal of imaging science and technology, vol. 40, No. 3, pp. 233-238, June 1996; R. Rolleston and R. Balasubramanian: “Accuracy of Various Types of Neugebauer Model”,
IS
&
T and SID's Color Imaging Conference: Transforms and Transportability of Color
, pp. 32-37, 1993). These Neugebauer-like models still need the knowledge of the color of the overprints of the primary inks, so still requires measurements overprint combinations of the colorants and the gradation steps of the colorants. Also, Neugebauer equations-based methods are known not to produce accurate results.
A second group of prior art methods are those that determine spectral characterizations of individual colorants that can be used for predicting the color of overprints of so-characterized colorants. These methods, for a fixed substrate and printing technique, involve making one or more printouts of each colorant on one or more substrates, measuring the prints, and out of this data extracting a set of one or more parameters for each colorant that can be used to calculate an overprint of each colorant. These methods thus have the advantage of not requiring producing a large set of overprints. One such prior art method uses the two-parameter Kubelka-Munk method which describes an ink wither by one spectral parameter, (K/S)(&lgr;), or by two spectral parameters, scattering S(&lgr;) and absorption &agr;(&lgr;), where &lgr; is the wavelength. See James H. Nobbs: “Kubelka-Munk Theory and the Prediction of Reflectance”,
Rev. Prog. Coloration
, Vol. 15, pp. 66-75, 1985.
Determining the two colorant parameters involves measuring the spectrum on a bare substrate and on a black substrate, and solving the resulting equations. There also exist in the literature refinements on the two-parameter Kubelka-Munk theory that incorporate internal reflection, anisotropic scattering and other second order effects. However, these
Meireson Baldewin
Van de Capelle Jean-Pierre
Detrix N. V.
Inventek
Rosenfeld Dov
Wallerson Mark
LandOfFree
Method and device for determining the color appearance of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for determining the color appearance of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for determining the color appearance of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2984428