Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1997-03-04
2001-09-04
Grimley, Arthur T. (Department: 2852)
Incremental printing of symbolic information
Ink jet
Controller
C347S037000
Reexamination Certificate
active
06283572
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to inkjet printers using multi-pass printmodes and, more particularly, to an inkjet printer which corrects for malfunctioning or inoperable ink ejection elements by substituting a fully functioning ink ejection element.
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) and U.S. Pat. Nos. 4,490,728 and 4,313,684. 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. 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.
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 nozzles 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 wide as the number of nozzles arranged in a column of the ink cartridge times the distance between nozzle centers. After each such completed movement or swath the medium is moved forward the width of the swath, and the ink cartridge begins the next swath. By proper selection and timing of the signals, the desired print is obtained on the medium.
Color inkjet hardcopy devices commonly employ a plurality of print cartridges, usually either two or four, mounted in the printer carriage to produce a full spectrum of colors. In a printer with four cartridges, each print cartridge contains a different color ink, with the commonly used base colors being cyan, magenta, yellow, and black. In a printer with two cartridges, one cartridge usually contains black ink with the other cartridge being a tri-compartment cartridge containing the base color cyan, magenta and yellow inks. The base colors are produced on the media by depositing a drop of the required color onto a dot location, while secondary or shaded colors are formed by depositing multiple drops of different base color inks onto the same dot location, with the overprinting of two or more base colors producing the secondary colors according to well established optical principles.
For many applications, such as personal computer printers and fax machines, the ink reservoir has been incorporated into the pen body such that when the pen runs out of ink, the entire pen, including the printhead, is replaced. However, for other hardcopy applications, such as large format plotting of engineering drawings, color posters and the like, there is a requirement for the use of much larger volumes of ink than can be contained within the replaceable pens. Therefore, various off-board ink reservoir systems have been developed recently which provide an external stationary ink supply. The external stationary ink supply may connected to the scanning cartridge or pen via a tube, or alternatively, the scanning cartridge or pen may move to the stationary ink supply and refill by “taking a gulp” from the ink supply. The external ink supply is typically known as an “off-axis,” “off-board,” or “off-carriage” ink supply.
The print quality produced from an inkjet device is dependent upon the reliability of its ink ejection elements. A multi-pass print mode can partially mitigate the impact of the malfunctioning ink ejection elements on the print quality. However, when more than a few ink ejection elements are malfunctioning, the multi-pass print mode can no longer solve the image quality problems caused by the malfunctioning ink ejection elements and the pen has to replaced in order to obtain satisfactory image quality.
Accordingly, what is needed is a method which corrects for malfunctioning or inoperable ink ejection elements by substituting a fully functioning ink ejection element.
SUMMARY OF THE INVENTION
The present invention provides a dynamic multi-pass print mode correction method which corrects for malfunctioning or inoperable ink ejection elements by substituting a fully functioning ink ejection element. The method comprises the steps of obtaining a printmask; identifying ink ejection elements which are malfunctioning; ascertaining potential replacement ink ejection elements from the printmask for the ejection elements which are malfunctioning; selecting replacement ink ejection elements from the potential replacement ink ejection elements; and modifying the printmask by removing the malfunctioning ink ejection elements from the printmask and replacing them with the selected replacement ink ejection elements.
REFERENCES:
patent: 5124720 (1992-06-01), Schantz
patent: 5319389 (1994-06-01), Ikeda et al.
patent: 0694396 (1996-01-01), None
patent: WO9632263 (1996-10-01), None
patent: WO9840222 (1998-09-01), None
Gaston Gonzalo
Kumar Shailendra
Lagares Javier
Grimley Arthur T.
Hewlett--Packard Company
Moldafsky Greg
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