Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-02-10
2001-11-13
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S015000
Reexamination Certificate
active
06315392
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to printers and, in particular, to a technique for increasing the speed of printing an image on a medium.
BACKGROUND OF THE INVENTION
Conventional printers are capable of printing in several different modes. The modes represent tradeoffs between print speed and print quality. For example, a printer may have a “best” mode which prints a high quality image at a relatively slow speed, a “normal” mode which prints a medium quality image at a relatively medium speed, and an “economy” mode which prints a low quality image, typically text, at a relatively fast speed.
One way of increasing print speed in color printers is to minimize the distance the carriage in the printer must travel. The carriage of a color printer typically holds several printheads (e.g., cyan, magenta, yellow, and black) and scans across a medium while depositing drops of ink from the printheads along the way. After the carriage completes one or more scans, the medium is shifted, and the carriage then begins another scan. This process is repeated until a desired image is formed on the medium. Since the carriage must scan this distance numerous times before the desired image is printed on the medium, a significant time savings could be achieved if the distance the carriage had to travel to complete a scan could be shortened.
Another way of increasing effective print speed in color printers is to underprint and overprint the black ink. As used herein, underprinting refers to depositing one or more drops of color ink (or a fixer fluid) on dot locations that will subsequently have one or more drops of black ink deposited thereon, and overprinting refers to depositing one or more drops of color ink (or a fixer fluid) on dot locations that have previously received one or more drops of black ink.
Underprinting and/or overprinting increases print speed because, with certain types of ink, black ink dries more quickly when it comes in contact with the color ink. This is due to the different chemistries of black ink and color inks. Black inks are often pigment based where color inks are often dye based. Pigment based inks dry slower than dye based inks. Since black ink dries relatively slowly, and since the ink must be dry before it is touched or has another sheet of paper dropped on top of it, the black ink drying time frequently becomes the bottleneck for print speed. Underprinting with a dye-based ink effectively wets the medium so that the black pigment vehicle is more quickly absorbed by the medium and dries quickly. Overprinting offsets any color shift by the underprinting.
Additionally, a chemical reaction may take place between the black ink and certain types of underprinted or overprinted ink (or other fluid) to speed up the drying time of the black ink. This also prevents the black ink from bleeding into adjacent color image portions. Accordingly, underprinting and/or overprinting increases print speed by decreasing the time it takes black ink to dry.
Another advantage of underprinting and overprinting is that the optical density (i.e., blackness) of the black printed image is increased if underprinting and/or overprinting is used.
A disadvantage of underprinting and overprinting is that the carriage which holds the cyan (C), black (K), magenta (M), and yellow (Y) printheads must travel a longer distance in order for the color inks (typically cyan and magenta) to underprint and overprint all of the black dot locations. This is especially disadvantageous when print speed is at a premium, for example when printing in the previously described “economy” mode.
Accordingly, what is needed is a technique that allows for underprinting and overprinting while minimizing the distance the carriage must travel when scanning across a medium.
SUMMARY
The present invention provides a method and an apparatus that allows for underprinting and overprinting while minimizing the distance the carriage must travel when scanning across a medium.
In one embodiment of the invention, a printer includes a carriage, a first printhead (e.g., cyan) mounted in the carriage, a second printhead containing black ink mounted in the carriage adjacent to the first printhead, and a third printhead (e.g., magenta) mounted in the carriage adjacent to the second printhead. The printer has a print zone, where black ink may be printed, having a left boundary and a right boundary. The carriage scans across the print zone such that the second printhead does not extend beyond the left or right boundary of the print zone, while the first and third printheads provide underprinting and/or overprinting of the black ink, depending on the leading and trailing printhead during a scan.
In the most straight-forward approach for underprinting, the leading printhead, rather than the black ink printhead, is positioned by the carriage at the edges of the print zone. The present technique modifies this straight-forward approach, as described above and, in one embodiment, reduces carriage travel by 1.5 inches during each scan to speed up printing by about 20%.
In one embodiment of the invention, the amount of ink deposited by the first printhead and third printhead for underprinting and overprinting is coordinated to minimize hue shift.
REFERENCES:
patent: 4952942 (1990-08-01), Kanome et al.
patent: 5568169 (1996-10-01), Dudek et al.
patent: 5933164 (1999-08-01), Sato et al.
patent: 6132021 (2000-10-01), Smith et al.
patent: 6139127 (2000-10-01), Kato et al.
patent: 6158834 (2000-12-01), Kato et al.
patent: 1038688 (2000-09-01), None
patent: 2293352 (1996-03-01), None
Ahlvin Eric L.
Kinas Erick
Hewlett--Packard Company
Nguyen Lamson D.
Nguyen Thinh
LandOfFree
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