Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1997-11-17
2001-01-23
Coles, Edward L. (Department: 2722)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C368S001000, C368S277000, C382S237000, C347S015000, C347S043000
Reexamination Certificate
active
06178009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to printing systems which provide several alternative inks for printing. More specifically, the present invention concerns a printing system in which low-penetration black ink and high-penetration black ink are selectably used to print black pixels upon a recording medium.
2. Description of the Related Art
Conventional ink jet printing systems have heretofore employed several different methods to print black ink upon a recording medium. Particularly, black color may be printed using either low-penetration black ink, high-penetration black ink, or so-called process black (hereafter PCBk). It should be understood that, throughout the present specification, the terms “high-penetration” and “low-penetration” are not intended to describe absolute amounts of ink penetration into a recording medium. Rather, the term “high-penetration ink”, as used herein, merely indicates an ink such as dye-based ink having a relatively greater penetration into a recording medium, whereas those inks described herein as “low-penetration” are inks such as pigment-based or evaporation inks having a relatively lower penetration.
Low-penetration black ink is often used to print black color in situations where a user desires high contrast between a printed black region and a lighter-colored surrounding region. This situation most commonly arises during text printing. Accordingly, most monochrome ink jet printers utilize low-penetration black ink.
High-penetration black ink is conventionally used in conjunction with differently-colored inks in order to produce color images. In this regard, a color printer usually provides for high-penetration inks corresponding to the subtractive color components, cyan, magenta, and yellow, as well as for black ink, which is used for under color removal. Variously-colored pixels are produced by printing none or some or all of the four inks at a single location upon a recording medium. Mixing of the printed inks generally produces muddy colors so high-penetration inks, which do not mix thoroughly, are generally preferred for color printing. Since high-penetration color inks are used for color printing, high-penetration black ink, which produces images having an optical density near to that of the color inks, is preferred for printing black pixels within a differently-colored region.
PCBk is produced by combining equal amounts of full-intensity cyan, magenta and yellow inks. In practice, PCBk does not provide as satisfactory a black color as low-penetration black ink or high-penetration black ink. However, PCBk, which shares penetration characteristics similar to its component colored inks, provides an output density similar to that of differently-colored pixels and is therefore useful for printing black color where uniform density between a black region and a color region is desired.
Therefore, whether a black pixel within an image should be printed using low-penetration black ink, high-penetration black ink, or PCBk is influenced by the content of the image data proximate to the black pixel. In this regard, current printing systems analyze binarized image data adjacent to a black pixel in order to determine a method for printing the black pixel. Unfortunately, in a case where the binarized data is based on multi-level original image data, the binarized data may not accurately reflect the original image data. As a result, a determined method for printing the black pixel may be inappropriate.
Moreover, as can be understood from the foregoing, optical characteristics of printed ink depend substantially upon an amount of penetration of the ink into a recording medium. However, conventional ink jet printing systems do not provide for selectable printing of low-penetration black ink and high-penetration black ink based upon absorption or other characteristics of a recording medium.
Therefore, what is needed is a printing system which selectably provides high-penetration black ink and low-penetration black ink for printing black pixels upon a recording medium based upon multi-level image data and/or characteristics of a recording medium.
On a related note, due to bleeding that occurs at a boundary between high and low-penetration inks, PCBk is sometimes used in order to provide a transition between a black region printed using black ink and a differently-colored region. Such a technique is disclosed in commonly-assigned co-pending application Ser. No. 08/901,719, entitled “PRINT DRIVER FOR A COLOR PRINTER”, filed Jul. 28, 1997.
However, in a case that PCBk is used at a boundary between a black region printed using low-penetration ink and a differently-colored region, the boundary is distracting to the eye. This distraction is caused by differences between the optical density of the differently-colored region, printed using high-penetration ink, and the optical density of the black region, printed using low-penetration ink.
On the other hand, in a case that PCBk is used at a boundary between a black region printed using high-penetration ink and a differently-colored region, the printed black region consists of a low-contrast, dull black color. Accordingly, each of the foregoing methods for printing a boundary region between black regions and differently-colored regions are unsatisfactory.
SUMMARY OF THE INVENTION
The present invention addresses the foregoing by providing selection, based on multi-level image data, of either a pigment-based black ink or a dye-based black ink for printing within a single printing system. As a result, both a pigment-based black ink and a dye-based black ink can be used to print appropriate portions of a single image so as to provide improved image quality.
The present invention also addresses the foregoing by selectably providing a first ink or a second ink for printing on a recording medium based on a detected material type of the recording medium.
In addition, the present invention selectably provides, for printing black pixels, either a pigment-based black ink or a combination of a dye-based black ink and dye-based inks of each of subtractive primary colors.
Moreover, the present invention provides a system to print a boundary region between a black region and a differently-colored region using, in turn, low-penetration black ink, high-penetration black ink, and PCBk.
In particular, the present invention relates to a system to control printing of pixels corresponding to multi-level image data in which it is determined, based on multi-level image data for a target pixel and multi-level image data for pixels adjacent to the target pixel, whether the target pixel should be printed using a dye-based ink or whether the target pixel should be printed using a pigment-based ink. In a case that it is determined that the target pixel should be printed using the dye-based ink, a printer is instructed to print the target pixel using the dye-based ink. On the other hand, in a case that it is determined that the target pixel should be printed using the pigment-based ink, the printer is instructed to print the target pixel using the pigment-based ink.
Due to the foregoing, the present invention provides improved output image quality. For example, a multi-level image to be printed may contain small isolated black regions within a larger color region, as well as solid black regions. Small isolated black regions within a larger color region are preferably printed using a dye-based black ink so as to reduce contrast between the small isolated regions and the differently-colored portions of the color region, which are printed using dye-based ink. By doing so, the output density of the larger color region appears uniform. In contrast, a pigment-based ink is preferred for printing a solid black region such as a border region because the quality of black color thusly obtained is superior to that of a dye-based ink or PCBk.
Moreover, because the determination of whether the dye-based ink or the pigment-based ink should be used is based on multi-level data, such small isolated black region
Hirabayashi Hiromitsu
Yamada Akitoshi
Canon Kabushiki Kaisha
Coles Edward L.
Fitzpatrick ,Cella, Harper & Scinto
Lamb Twyler
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