Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-12-22
2001-11-13
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06315383
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to ink-jet hard copy apparatus, and, more specifically, to methods and apparatus for the use of electrostatic devices for detection of ink drop characteristics and printing with correction for offsets.
2. Description of Related Art
The art of ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, and facsimile machines employ ink-jet technology for producing hard copy. The basics of this technology are disclosed, for example, in various articles in 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) editions. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in
Output Hardcopy
[sic]
Devices
, chapter 13 (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).
FIG. 1
depicts an ink-jet hard copy apparatus, in this exemplary embodiment a computer peripheral printer,
101
. A housing
103
encloses the electrical and mechanical operating mechanisms of the printer
101
. Operation is administrated by an electronic controller
102
(usually a microprocessor-controlled printed circuit board) connected by appropriate cabling to a computer (not shown). Cut-sheet print media
105
, loaded by the end-user onto an input tray
107
, is fed by a suitable paper-path transport mechanism (not shown) to an internal printing station where graphical images or alphanumeric text is created. A carriage
109
, mounted on a slider
111
, scans the print medium. An encoder
113
,
114
subsystem is provided for keeping track of the position of the carriage
109
at any given time. A set of ink-jet pens, or print cartridges,
115
x
(where the letter is a color designation, e.g., cyan (C), magenta(M), yellow (Y), black (K), red (R), blue (B), green (G), or a fixer chemical (F)) are releasably mounted in the carriage
109
for easy access. In pen-type hard copy apparatus, separate, replaceable or refillable, ink reservoirs
117
x
are located within the housing
103
and appropriately coupled to the pen set
115
via ink conduits
119
. Once a printed page is completed, the print medium is ejected onto an output tray
121
. Printing is accomplished on the print medium as it transits a print zone
123
.
“A simplistic schematic of a swath-scanning ink-jet pen
115
is shown in
FIG. 2
(PRIOR ART). The body
210
of the pen
115
generally contains an ink accumulator and regulator mechanism
212
. The internal accumulator and regulator are fluidically coupled
119
(
FIG. 1
only) to an off-axis ink reservoir
117
x
in any known manner to the state of the art. The printhead
214
element includes an appropriate electrical connections
220
(such as a tape automated bonding flex tape) for transmitting signals to and from the printhead. Columns of individual nozzles
217
form an addressable firing array
216
. The typical state of the art scanning pen printhead may have two or more columns with more than one-hundred nozzles per column, each nozzle having a diameter of about {fraction (1/300)}th inch or less. Multi-color pens having the nozzle array
216
is subdivided into discrete subsets, known as “primitives” are also known in the art. In a thermal ink-jet pen, the drop generator includes a heater resistor subjacent each nozzle which on command superheats local ink to a cavitation point such that an ink bubble's expansion and collapse ejects a droplet from the associated nozzle
217
. In commercially available products, piezoelectric and wave generating element techniques are also used to fire the ink drops. Degradation or complete failure of the drop generator elements cause drop volume variation, trajectory error, or misprints, referred to generically as “artifacts,” and thus affect print quality.
In essence, the ink-jet printing process involves digitized dot-matrix manipulation of drops of ink, or other liquid colorant, ejected from a pen onto an adjacent print media. [For convenience of describing the ink-jet technology and the present invention hereinafter, all types of print media are referred to simply as “paper,” all compositions of colorants are referred to simply as “ink,” and all types of hard copy apparatus are referred to simply as a “printer.” No limitation on the scope of invention is intended nor should any be implied.] Each column or selected subset of nozzles selectively fires ink droplets (typically each being only a few picoliters in liquid volume, having a nominal diameter of only about ten in flight and forming a dot of approximately forty &mgr;m on the paper) that create a predetermined print matrix of dots on the adjacently positioned paper as the pen is scanned. The pen scanning axis is the x-axis, the paper path is the y-axis and the ink drop firing direction is the z-axis; related linear offsets are referred to as delta-x, delta-y and delta-z, respectively, and rotational offsets are referred to as theta-x (printhead planar pitch), theta-y (roll) and theta-z (yaw). A given nozzle of the printhead is used to address a given matrix column print position on the paper (referred to as a picture element, or “pixel”).
Horizontal positions, matrix pixel rows, on the paper are addressed by repeatedly firing a given nozzle at matrix row print positions as the pen is scanned. Thus, a single sweep scan of the pen across the paper can print a swath of tens of thousands of dots. The paper is stepped to permit a series of contiguous swaths. Complex digital dot matrix manipulation is used to render alphanumeric characters, graphical images, and even photographic reproductions from the ink drops. Page-wide ink-jet printheads are also contemplated and are adaptable to the present invention.
As can now be recognized, the seemingly simple process of creating a computer print by scanning a plurality of printheads while actively firing minute ink droplets across a z-axis gap onto a sheet of paper as a digital dot matrix of organized pixels in order to form sophisticated graphics and photographs is actually a highly complex process. The reduction of visible artifacts in the print is a constant concern of the system designer.
A variety of techniques have been used over the years since the inception of ink-jet printing to ensure appropriate dot placement. In U.S. Pat. No. 4,794,411, filed in 1987 by Taub et al., a THERMAL INK-JET HEAD STRUCTURE WITH ORIFICE OFFSET FROM RESISTOR methodology teaches a controlling of misdirection of fired drops by proper nozzle design. In U.S. Pat. No. 4,922,268, filed in 1989 by Osborne, a PIEZOELECTRIC DETECTOR FOR DROP POSITION DETERMINATION IN MULTI-PEN THERMAL INK JET PEN PRINTING SYSTEMS teaches a methodology for mapping the positions of nozzles with respect to a pattern of openings in the detector [U.S. Pat. No. 5,036,340 filed in 1990 by Osborne is a continuation-in-part of '268.] In U.S. Pat. No. 4,922,270 filed simultaneously with Osborne by Cobbs et al., an optical or piezoelectric or electrostatic phase plate detector through which a drop is fired and measurements are used for INTER PEN OFFSET DETERMINATION AND COMPENSATION IN MULTI-PEN THERMAL INK JET PEN PRINTING SYSTEMS [U.S. Pat. No. 5,109,239 is a continuation-in-part of '270]. In U.S. Pat. No. 5,404,020, filed in 1993 Cobbs teaches a PHASE PLATE DESIGN FOR ALIGNING MULTIPLE INKJET CARTRIDGES BY SCANNING A REFERENCE PATTERN. In U.S. Pat. No. 5,448,269, filed in 1993 by Beauchamp et al., MULTIPLE INKJET CARTRIDGE ALIGNMENT FOR BIDIRECTIONAL PRINTING BY SCANNING A REFERENCE PATTERN is shown. In U.S. Pat. No. 5,835,108, filed in 1996, Beauchamp et al. teach a CALIBRATION TECHNIQUE FOR MISDIRECTED INKJET PRINTHEAD NOZZLES. Each of the aforementioned patents is assigned to the common assignee herein and incorporated herein by reference.
As thermal ink-jet pens are used, damage may occur, such as due to a printhe
Elgee Steven B
Sarmast Sam Michael
Barlow John
Hewlett--Packard Company
Loper, Jr. Robert D
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