Patent Grant
7407242
The present embodiments relate to methods for processing of digital data purposed for output to an inkjet printing device.
Inkjet printing typically involves the use of water based inks. These water based inks interact with papers differently than inks used in other printing systems such as web offset printing. In particular, water based inks can cause print defects, such as bleed and mottle, and can cause paper deformities, such as cockle, curl, and show through of the text onto the opposite side of the page. These defects result in a need to limit the total amount of ink applied to the paper per unit area of a printed image. This limitation is often referred to as the upper ink limit (UIL) used for data processing for the printing system. The UIL necessary for one paper may not be the same as that appropriate for another paper, due to differences in paper type, weight, and coating. Thus, for each paper used on a given inkjet printing system, a different UIL needs to be specified by the user.
In the field of production printing, the ability to print text of various hues and saturations is commonly desirable. In order to achieve this range of colors, text may be printed using one or more colors of ink. Most commonly, process color prints are made using four inks: cyan, magenta, yellow, and black. Due to the defects mentioned above and the fine level of detail needed to render smaller point sizes of text and certain fonts with small features such as serifs, all possible ink loadings are not always acceptable. In particular, higher ink loads often result in printing defects, such as “ink bleed” that may cause small point sizes of text to be of unacceptably low quality or entirely illegible. The UIL allowable for text is partly dependent on the particular font and point size of the text, as well as the particular paper stock used for printing.
Typically, print defects are avoided by limiting the amount of ink that is used when printing smaller point sizes of text. The use a single ink limit for all colors of text is not often the most effective approach because when more than one color of ink is used for a particular text color a higher level of total ink might be permitted than for a text color that is created using only a single color of ink. The press operator or graphic designer may, therefore, specify several different total ink limits for small sizes of text based on whether the text is composed of one or more colors of ink. Empirically determining each of these limits for each paper and system configuration can be a tedious process.
A need exists for a series of steps to derive automatically the total ink limits of multi-ink texts using user supplied limits for text colors composed of just one or two inks. A need exists for a series of steps that enable the automatic adjustment of data coming into an ink jet printer and the use of these derived limits saving a user time and money for manually inputting two ink limits. A need has existed for a user to simply input one or two values for single and two-ink limits derive the remaining ink limits and apply all these ink limits to all parts of a print job regardless of size. The present methods meet these needs and save a user a significant amount of time and labor
The method for a printing device is used to determine the maximum amount of colorant to be deposited on a specific region of print media in order to form an image with a reduced quantity of visual defects. Initially, a single colorant value is input on the specific region of print media. The single colorant value indicates a total amount of single colorant that is to be applied by the printing device. The method then entails deriving a colorant limit for each color or combinations thereof according to a text ink limit algorithm, and applying each derived color ink limit to the image to limit the quantity of ink used by the printing device when one of the derived colorant limits is exceeded.
In the detailed description of the preferred embodiments presented below, reference is made to the accompanying drawings, in which:
The present embodiments are detailed below with reference to the listed Figures.
Before explaining the present embodiments in detail, it is to be understood that the embodiments are not limited to the particular descriptions and that it can be practiced or carried out in various ways.
In many printing systems, printing small point size text using the full amount of ink available on an ink jet printing system is not always possible. The ink and substrate frequently interact causing a maximum ink limit for small subject matter on certain types of substrates.
Typically, if a single primary color can print at X % ink coverage, secondary colors can usually be printed at Y % ink coverage, wherein Y is a value greater than X. A higher ink limit may be allowed if the two inks are applied at two different times. Similarly, three-color text can be printed at a higher percentage than two color text if printed sequentially. The embodied methods allow a user to derive all of the appropriate ink levels for a specific paper or other print media, with input from the user defining only one or two of the actual ink limit levels.
The present methods were created to limit the amount of visual defects in resulting printed images using an automatic system that requires little user input in order to quickly create a higher quality image as compared with existing systems.
The embodied methods provide for the automatic determination of text ink limits for the printing of multi-ink text given user input about only one or at the most two ink limits or a given text or font or image size with given types of media.
This automatic determination method uses a particular sequence of steps to compute the multi-ink text ink limits that is dependent on the particular printing system, the typical inks, and the selected print media substrate selected for use with that system. Given a particular printing system and samples of various media and ink associated with the system, the method uses a sequence of steps to predict the ink limits of text for a particular substrate composed of multiple inks using only one or two ink limit values.
With reference to the figures,
Visual defects include defects from colorant bleeding, print media deformation, show through defect, over saturation of colorant, mottle and the like. Bleeding defect occurs when the ink runs together or is diffused out of the specified region. Mottle defects are the appearance of spotty or uneven printing, most commonly in solid areas. Show-through defects and printings that are visible from the back side of a print media or from the next print media under normal lighting conditions. Wrinkles, with respect to ink, are defects in an uneven surface formed from drying.
The methods provide the user with a simplified way of producing printed text with optimal quality.
The methods are usable printing devices, such as ink jet printers, laser printers, off set printers, and even digital printing machines.
Within the scope of the methods, the print media can be paper, film, cardboard, paperboard, woven fabric, non-woven fabric, vinyl sheets, metallic foil, metalized plastic film, laminates thereof, and similar type materials that accept colorant to form images. The images formed on the print media are typically vector-based images, line art, text images, or combinations thereof.
As depicted in
The method continues by deriving a colorant limit for each color 20 or combinations thereof 22. The colorant limit is derived according to a text ink limit algorithm 24. Typically, the colors 20 used in printing are cyan, magenta, black, yellow, and combinations thereof, but the method is not limited to these specific colors.
The step of deriving of the colorant limit for each color utilizes the equation: Li=L(i−1)*(1+ai), wherein 0≦ai≦a(i−1)≦1. In the equation, Li represe the colorant limit when i number of colorants are applied to the specific region of the print media. L(i−1) represents the colorant limit when (i−1) number of colorants is applied to the specific region of the print media. The equation term ai represents the incremental amounts of additional colorant that can be applied when i number of colorants are increased by one to reach a maximum number of colorants i. The equation term a(i−1) represents the incremental increase in the amount of colorants that can be applied when (i−1) number of colorants are applied to a specific region of the print media, and wherein i≧2.
The color limit can be derived for each color utilizing two equations 27 and 30. One equation is L3=2*L2−L1, wherein L1 represents the single colorant value and L2 represents a combination of two colorant values 32. The other equation is L4=3*L2−2*L1, wherein L3 represents a combination of three colorant values 34 and L4 represents a combination of four colorant values 36.
For example, in a given printing system, the appropriate ink limits for a three color text and a four color text are determined according to the equations: L3=2*L2−L1 and L4=3*L2−2*L1
In these equations, L2 is the ink limit for two-color text ranging from 0% to 200%. Similarly, L1 is the ink limit for single color text ranging from 0% to 100%.
The method ends by applying each derived color ink limit to the image in order to limit the quantity of ink used by the printing device when one of the derived colorant limits is exceeded.
Additionally, hues can be preserved through additional processes of color management, prior to using the algorithm to be used in this method
The colorant usable herein can be toner, colored wax, pigment, dye, dye-based ink, water-based ink, oil-based ink, and ink with other solvent bases.
An embodiment of the method can include an algorithm derived from text limits. The algorithm can include coefficients determined from look-up tables. Once text limits have been derived using the method of the algorithm, inking input limits that exceed this threshold are scaled back.
Allocation of derived total limit to the individual primary colors must be determined. The simplest method is to ratio the total ink limit proportionally to each of the individual constituent inks in the text. A more complex method is to apply N-dimensional color management to minimize the error in hue while reducing the colorant levels to the established a threshold that is derived from a look-up table, an algorithm or some combinations thereof.
Look-up table values can be colorant independent, based on color gamut, or other measured physical attributes related to image quality, such as density. The look-up table can be used instead of the algorithm to derive ink limits for text based on physical parameters of the printing system. The look-up tables provide input values of 1-N (that is, 1 through N)color text, wherein the input value is a function of printing on certain substrates with certain inks and other print factors. Additionally, color measurements can be correlated to text ink limits. Color gamut and color saturation are strong indicators of inking levels for text.
For example, two vectors in a color space, one for each color, are measured from white paper to a point of maximum saturation. The look-up table is used to correlate the length of the vectors to ink text limit. Each primary color of multicolor text can have different look-up values based on different table entries corresponding to different vector lengths. Multiple output values from the look-up table usable herein, include variable point sizes and/or the number of primary colors composing the text.
An alternative embodiment of the methods can include look-up tables that are one-dimensional, or look-up tables are based on overall color gamut volume.
Embodiments of the methods extend beyond a text ink limit to a fine line, or fine image usage where the image requires an edge with high acuity. The embodied methods are considered applicable to line art, inked drawing reproduction, or other images where line thickness is important and edge definition is needed.
Additionally, hues can be preserved through additional processes of color management, prior to creating look-up tables to be used in this method.
The embodiments have been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the embodiments, especially to those skilled in the art.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20040114158 | Klassen et al. | Jun 2004 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20050248598 A1 | Nov 2005 | US |
