Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-11-24
2002-03-12
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000
Reexamination Certificate
active
06354687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to ink-jet technology, more particularly to characterizing ink-jet performance and, even more specifically, to methods and apparatus for predicting and adjusting ink-jet component performance.
2. Description of the Related Art
The art of ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. [For convenience, the term “printer” is used hereinafter as generic for all ink-jet hard copy apparatus; no limitation on the scope of the invention is intended by the inventors nor should any be implied.]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). As providing background information, the foregoing documents are incorporated herein by reference.
FIG. 1
(PRIOR ART) is a schematic depiction of an ink-jet hard copy apparatus
10
. A writing instrument
12
has a printhead
14
having “drop generators” for ejecting ink droplets onto an adjacently positioned print medium, e.g., a sheet of paper
16
, in the apparatus' printing zone
34
. (The word “paper is used hereinafter for convenience as a generic term for all print media; the implementation shown is for convenience in explaining the present invention and no limitation on the scope of the invention is intended by the inventors nor should any be implied.) An endless-loop belt
32
is one type of known manner printing zone
34
input-output paper transport. A motor
33
having a drive shaft
30
is used to drive a gear train
35
coupled to a belt pulley
38
mounted on an fixed axle
39
. A biased idler wheel
40
provides appropriate tensioning of the belt
32
. The belt rides over a platen
36
in the printing zone
34
. The paper sheet
16
is picked from an input supply (not shown) and its leading edge
54
is delivered to a guide
50
,
52
where a pinch wheel
42
in contact with the belt
32
takes over and acts to transport the paper sheet
16
through the printing zone
34
(the paper path is represented by arrow
31
). Downstream of the printing zone
34
, an output roller
44
in contact with the belt
32
receives the leading edge
54
of the paper sheet
16
and continues the paper transport until the trailing edge
55
of the now printed page is released.
It is also known to have an on-board controller
62
, electrically connected
60
,
64
to the motor, to sensors
41
on the pulley, to the writing instrument
12
, and to other electromechanical systems of the hard copy apparatus
10
. Operation is administrated by the electronic controller
62
which is usually a microprocessor or application specific integrated circuit (“ASIC”) controlled printed circuit board which, if necessary, for the particular hard copy apparatus connected by appropriate cabling to the computer (not shown). It is well known to program and execute imaging, printing, print media handling, control functions, and logic with firmware or software instructions for conventional or general purpose microprocessors or ASIC's. Within the printing zone
34
, graphical images or alphanumeric text are created with the ink droplets deposited on the paper sheet
16
using state of the art color imaging and text rendering via dot matrix manipulation techniques.
A simplistic schematic of a swath-scanning ink-jet pen
12
is shown in
FIG. 2
(PRIOR ART). The body of the pen
12
generally contains an ink accumulator and regulator mechanism
200
. The internal accumulator and regulator are fluidically coupled
200
' to an off-axis ink reservoir (not shown) in any known manner to the state of the art. The printhead
14
element includes an appropriate electrical connector
201
(such as a tape automated bonding flex tape) for transmitting signals to and from the printhead. Columns of nozzles
203
form an addressable firing array
205
. The typical state of the art scanning pen printhead may have two or more columns with more than one-hundred nozzles per column. The nozzle array
205
is usually subdivided into discrete subsets, known as “primitives,” which are dedicated to firing droplets of specific colorants. In a thermal ink-jet pen, the drop generator includes a heater resistor subjacent each nozzle which superheats ink to a cavitation point such that an ink bubble's expansion and collapse ejects a droplet from the associated nozzle
203
. In commercially available products, piezoelectric and wave generating element techniques are also used to fire the ink drops. Other ink-jet writing instruments are known in the art; some, for example, are structured as page-wide arrays. 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 some state of the art ink-jet printers, replacement ink reservoirs are available and thus use the same single writing instrument printhead
14
repeatedly, requiring a longer life than the intended one-time use disposable ink-jet cartridge that contains an on-board ink reservoir. Thus, one of the operational characteristics of concern to the designer is printhead
14
life. One gauge, or “ruler,” that has been used in the prior art is drop counting. U.S. Pat. No. 5,583,547, DROP COUNT-BASED INK-JET PEN SERVICING METHOD, and U.S. Ser. No. 07/951,255, by Gast et al. describes exemplary methods and apparatus. In the main, drop counting and ink droplet flight-path monitoring provide information useful in controlling printer operations. There are certain advantages for the use of drop counting as a ruler to anticipate some characteristics of the printhead and to adjust future printer activity accordingly. While drop counting is a logical ruler, it has been found that it is not necessarily the best printhead life indicator. Printhead life based on a total drop count for the pen, or even per column count, assumes that the energy to firing nozzles in the array is always the same regardless of firing patterns. In fact, however, the total energy going into the printhead varies from print pattern to print pattern (low frequency text printing energy is substantially less than photo-quality color graphics printing) and from primitive to primitive (i.e., a particular firing sequence may fire from zero to all of the nozzles in a primitive and from one to all the primitives of the entire nozzle array). Thus, drop counting with respect to determining printhead performance and life-expectancy characteristics is effectively only a type of averaging technique.
There is a need for a more accurate predictor of printhead firing element life and performance. The tool should be easily implemented and provide real-time data useful on-the-fly to adjust printer activity or to provide information useful to the end-user.
SUMMARY OF THE INVENTION
In a basic aspect, the present invention provides an ink-jet printhead printing method for a printhead having a predetermined matrix of drop generators. The method includes the of: setting a predetermined accumulated energy budget value for each addressable subset of drop generators; determining a next drop generator firing sequence; setting firing energy for addressed subsets of drop generators based on a function of current accumulated energy budget; printing with the next drop generator firing sequence; resetting said predetermined accumulated energy budget value for addressed subsets of drop generators as a function of number of nozzles fired in the step of printing as reset accumula
Su Wen-Li
Wetchler David
Hewlett -Packard Company
Hsieh Shih-Wen
Le N.
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