Printing – Multicolor – Processes
Reexamination Certificate
2002-07-19
2004-04-27
Eickholt, Eugene H. (Department: 2854)
Printing
Multicolor
Processes
C101S181000, C358S002100, C345S597000, C356S402000, C356S421000
Reexamination Certificate
active
06725772
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to the field of printing and, more particularly, to a system admixture compensation system and method.
BACKGROUND OF THE INVENTION
Full-color printing on offset presses has become relatively reliable and affordable for clients long accustomed to printing in black and white or with just one or two pre-mixed spot inks. Such printing utilizes photo-chemical processes to reduce original multi-colored materials to the four constituent colors used in printing. For example, printed color images currently typically combine different intensities of four basic colors—Magenta (“M”), Yellow (“Y”), Cyan (“C”), and Black (“K”)—using a printing process known as four-color-process printing. In practice, accurately printing a color image to a customer's satisfaction is often times tedious, problematic and time consuming, as it usually requires manual intervention. For example, conventional four-color-process printing usually utilizes presses that are only designed to either apply or not apply a single amount of ink to any given location on a page. To reduce the number of errors and expenses associated with errors in acceptable print quality off the press, proofs are usually used.
To illustrate, four-color-process printing requires a reliable color proof for use as a guide for press operators and customers in finalizing a printing press to perform a production print job. For example, the proof conveniently and inexpensively provides a printing prototype for a customer to approve color appearances to be used on a production print job, in an easily-changed and viewable image. A single piece of film for each of the four colors is also required by the platemaker to make thin printing plates that are wrapped on the drums of the printing press, covered with the appropriate inks, which are then indirectly rolled over sheets of paper during the printing process. Computer-to-Plate (CTP) technology can eliminate the need for film in the plate-creation process.
Traditional attempts in performing or addressing aspects of the color management process for Reflective Multi-Color Reproduction Systems (RM/CRSs) include approaches which typically suffer from compromises and results that in many cases customers in the printing industry feel are unsatisfactory. For example, traditional quality control specifications such as Specifications Web Offset Publications (SWOP) have utilized solid ink density, ink color (hue)/sequence, and dot gain and print contrast to control variables, with only limited success.
SUMMARY OF THE INVENTION
Unfortunately, a proof includes inherent tone and color differences from a press sheet, and a great deal of time is consumed in assessing how to improve the coincidence of the tone and color reproduction characteristics of a press to those of a proofing system. Moreover, SWOP specifications do not typically discuss several variables such as proportionality failure rates, system admixture characteristics, and color gamut mismatches that color scientists use in characterizing color reproduction. International Color Consortium (ICC) color management systems have also attempted to address the color management process by utilizing colorimetry measurements, usually in a single graphic data file multi-dimensional transformation process, but practitioners in the printing press industry usually believe that this type of adaptation is inadequate. These systems also fail to separate or compensate for these variables. ICC-colorimetry based color management systems also attempt to map points on a larger color gamut to a nearest point on a smaller color gamut by a variety of corrections, such as relative or absolute colorimetric or photometric. Unfortunately, this type of gamut mapping has typically resulted in compromises that are unacceptable in the printing industry. Moreover, these systems usually attempt to map colors to be used with a proofing device, which usually has a larger color gamut, to those to be used with a printing device, which usually has a smaller color gamut. These systems and methods typically limit the output achievable by a printing press.
Unfortunately and for example, the SWOP approach suffers from inconsistencies and inaccuracies because, among other things, this approach utilizes dot gain and print contrast measurements, which may not provide the right measurements to perform aspects of accurate color management. Moreover, these systems and methods do not consider varying effects from the principle variables that ultimately should be addressed in the color management process. For example, tonal reproduction characteristics vary widely with characteristics of a reflective reproduction device such as electrophotographic, thermal, laser and inkjet printers, and offset lithography, letter press, gravure, and flexography printing presses and peripheral conditions, and traditionally are reported as dot gain and print contrast. Many of these variations that may be caused by fluctuations in press printing conditions' printing characteristics including, but not limited to, variations due to paper/base substrates, inks, plates, fountain solutions, image transferring cylinder blankets, press mechanical settings and ambient moisture/temperature conditions may change batch-to-batch or day-to-day. These fluctuations usually affect the printing device's reproduction characteristics during each production print job and, unfortunately, it is not practical to track down causes of these fluctuations.
From the foregoing, it may be appreciated that a need has arisen for a system admixture compensation system and method. In accordance with teachings of the present invention, a system and method are provided that may substantially reduce or eliminate disadvantages and problems of conventional printing systems.
Aspects of the invention may provide several important advantages. Various embodiments of the invention may have none, some, or all of these advantages. For example, one aspect of the invention is a method for gathering data such as density data that provides more control in the color management process. The method includes providing reference profile density values for at least one color combination having a plurality of colors produced by a reference device using a reference colorant set. The reference colorant set has reference initial percent dot values (IPDVs) for the at least one color combination. The method also includes providing current profile density values for at least one color combination produced by a current device using a current colorant set. The current colorant set has current IPDVs for the at least one color combination. The method also includes quantifying reference theoretical percent dot values (TPDVs) as efficiency attributes using the reference colorant set and quantifying current TPDVs as efficiency attributes using the current colorant set. The method also includes calculating percent dot value correction factors that compensate for at least one difference between image data produced with the reference colorant set and image data to be printed with the current colorant set in response to the reference efficiency attributes and the current efficiency attributes, the factors to be used to adjust and generate the image data to be printed. Such calculations may provide substantially representative characteristics of a full tonal scale (1-100%) for press and/or proofing conditions, and the ability to provide factors that may be applied to, for example, digital representations of images, at a computer-to-plate (CTP) or direct imaging press production phase. In other words the accuracy, with which the appearance of the outputs of one reflective reproductive system may be made to correspond to another, may be improved.
Another aspect of the invention may also provide for separately compensating for two of five principle variables. For example, one embodiment of a system admixture compensation method includes identifying system admixture characteristics of data produced by a reference colorant set a
Krause Barry W.
Martinez Charles
Martinez Henry
Ackley Martinez Company
Eickholt Eugene H.
Munsch Hardt Kopf & Harr P.C.
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