Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-04-29
2001-06-19
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S009000
Reexamination Certificate
active
06247787
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to thermal inkjet printers, and more particularly to printmodes.
BACKGROUND OF THE INVENTION
Thermal inkjet hardcopy devices such as printers, graphics plotters, facsimile machines and copiers have gained wide acceptance. These hardcopy devices are described by W. J. Lloyd and H. T. Taub in “Ink Jet Devices,” Chapter 13 of
Output Hardcopy Devices
(Ed. R. C. Durbeck and S. Sherr, San Diego: Academic Press, 1988). The basics of this technology are further disclosed in various articles in several editions of the
Hewlett
-
Packard Journal
[Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No.1 (February 1994)], incorporated herein by reference. Inkjet hardcopy devices produce high quality print, are compact and portable, and print quickly and quietly because only ink strikes the paper.
An inkjet printer forms a printed image by printing a pattern of individual dots at particular locations of an array defined for the printing medium. The locations are conveniently visualized as being small dots in a rectilinear array. The locations are sometimes “dot locations”, “dot positions”, or pixels”. Thus, the printing operation can be viewed as the filling of a pattern of dot locations with dots of ink.
Inkjet hardcopy devices print dots by ejecting very small drops of ink onto the print medium and typically include a movable carriage that supports one or more printheads each having ink ejecting nozzles. The carriage traverses over the surface of the print medium, and the nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to the pattern of pixels of the image being printed.
The typical inkjet printhead (i.e., the silicon substrate, structures built on the substrate, and connections to the substrate) uses liquid ink (i.e., dissolved colorants or pigments dispersed in a solvent). It has an array of precisely formed orifices or nozzles attached to a printhead substrate that incorporates an array of ink ejection chambers which receive liquid ink from the ink reservoir. Each chamber is located opposite the nozzle so ink can collect between it and the nozzle and has a firing resistor located in the chamber. The ejection of ink droplets is typically under the control of a microprocessor, the signals of which are conveyed by electrical traces to the resistor elements. When electric printing pulses heat the inkjet firing chamber resistor, a small portion of the ink next to it vaporizes and ejects a drop of ink from the printhead. Properly arranged nozzles form a dot matrix pattern. Properly sequencing the operation of each nozzle causes characters or images to be printed upon the paper as the printhead moves past the paper.
In an inkjet printhead the ink is fed from an ink reservoir integral to the printhead or an “off-axis” ink reservoir which feeds ink to the printhead via tubes connecting the printhead and reservoir. Ink is then fed to the various vaporization chambers either through an elongated hole formed in the center of the bottom of the substrate, “center feed”, or around the outer edges of the substrate, “edge feed.”
The ink cartridge containing the nozzles is moved repeatedly across the width of the medium to be printed upon. At each of a designated number of increments of this movement across the medium, each of the resistors is caused either to eject ink or to refrain from ejecting ink according to the program output of the controlling microprocessor. Each completed movement across the medium can print a swath approximately as high as the number of nozzles arranged in a column of the ink cartridge multiplied times the distance between nozzle centers. After each such completed movement or swath the medium is moved forward the height of the swath or a fraction thereof, and the ink cartridge begins the next swath. By proper selection and timing of the signals, the desired print is obtained on the medium.
Lines, text and graphics are normally printed with uniform density. In one or two pass printmodes, this results in a high firing frequency for black and saturated colors. High firing frequency has a negative effect on the drops that are ejected: drop velocity, drop volume, drop shape and drop trajectory. Output printed with high frequency and uniform density text and lines exhibits defects that are the result of the sub-optimal firing conditions. Accordingly, there is a need for a solution to the problem of text and graphics degradation and, more generally, edge roughness that is associated with high frequency firing.
SUMMARY OF THE INVENTION
The present invention provides a method for incremental printing with an inkjet swath printer by depositing multiple drops of an ink from a printhead in each column of an image, in each scanning pass of the printhead over a print medium by obtaining the image, analyzing the image to determine which drops of ink will define trailing edges in each row of the image element with respect to a scanning direction, removing at least one drop of ink preceding the drop defining the trailing edges in each of the rows and depositing the remaining drops of the ink on the medium while passing the printhead over the media in the scanning direction. Another embodiment provides a method for incremental printing with an inkjet swath printer by depositing multiple drops of an ink from a printhead in each column of an image, in each scanning pass of the printhead over a print medium by obtaining the image, analyzing the image to determine which drops of ink will define leading edges in each row of the image element with respect to a scanning direction, removing at least one drop of ink after the drop defining the leading edges in each of the rows and depositing the remaining drops of the ink on the medium while passing the printhead over the media in the scanning direction.
Another embodiment of the present invention is a method of printing with an inkjet printing system scanning over a print medium by providing a printhead having a supply of ink and a plurality of ink ejection chambers for ejecting ink onto the print medium, each of the ink ejection chambers depositing the ink onto a corresponding row, the ink ejection chambers ejecting ink drops in a range of frequencies between a base firing frequency and a maximum firing frequency, obtaining an image, analyzing the image to determine which drops of ink will define trailing edges in each row of the image element with respect to a scanning direction, ejecting the drop of ink defining the trailing edges in each of the rows at an ejection frequency less than the maximum frequency and depositing the remaining drops of the ink on the medium while passing the printhead over the media in the scanning direction. Another embodiment of the present invention is a method of printing with an inkjet printing system scanning over a print medium providing a printhead having a supply of ink and a plurality of ink ejection chambers for ejecting ink onto the print medium, each of the ink ejection chambers depositing the ink onto a corresponding row, the ink ejection chambers ejecting ink drops in a range of frequencies between a base firing frequency and a firing frequency, obtaining an image, analyzing the image to determine which drops of ink will define leading edges in each row of the image element with respect to a scanning direction, ejecting the drop of ink defining the leading edges in each of the rows at an ejection frequency less than the maximum frequency and depositing the remaining drops of the ink on the medium while passing the printhead over the media in the scanning direction.
REFERENCES:
patent: 5661507 (1997-08-01), Sperry
patent: 6161918 (2000-12-01), Bailey et al.
Askeland Ronald A.
Giere Matthew D
Holstun Clayton L
Hewlett--Packard Company
Nguyen Thinh
Stenstrom Dennis G.
LandOfFree
Print mode for improved leading and trailing edges and text... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Print mode for improved leading and trailing edges and text..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Print mode for improved leading and trailing edges and text... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445538