Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-11-29
2004-02-10
Nguyen, Judy (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000
Reexamination Certificate
active
06688716
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus for performing recording by ejecting ink from recording means onto a recorded medium.
2. Description of the Related Art
There are recording apparatuses having recording capabilities, such as printers, copiers and facsimiles, or recording apparatuses for use as output equipments of composite-type electronic equipment and work station including computers and word processors. The above-mentioned recording apparatuses are to record images (including texts and the like) on recorded media, such as sheets of paper or plastic thin sheets, on the basis of image information (containing character information). The recording apparatuses may be classified by recording method into ink-jet type, wire dot-matrix type, thermal, recording type and laser-beam type. Of the types of recording apparatuses, the ink-jet type recording apparatuses (ink jet recording apparatuses) perform recording by ejecting ink from recording means (recording head(s)) onto recorded media, which are superior to the other types of recording apparatuses and enable high-resolution recording to be carried out quietly at high speed. In addition, the ink-jet type recording apparatuses are inexpensive, thus displaying excellent characteristics.
In recent years, with the growing need for apparatuses capable of printing finer (high-resolution) color images, many color ink-jet recording apparatuses capable of recording color images by ejecting a plurality of color inks have also been developed.
To improve recording speed, the above-mentioned ink jet recording apparatuses use a recording head constituted of a plurality of recording elements integrated therein, with a plurality of combinations of ink ejection orifices as ink ejection parts and liquid channels integrated therein. For color recording, plural recording heads configured such above are generally provided.
FIG. 1
shows a configuration of a printer part for carrying out printing on the surface of a recording medium using the above-mentioned recording head. Indicated with the reference numeral
101
in
FIG. 1
are ink cartridges, each of which is composed of an ink tank and a recording head
102
. Each ink tank is filled with one of four color inks, namely black, cyan, magenta or yellow ink. A row of plural orifices is formed on the recording head
102
.
FIG. 2
is a schematic diagram showing the plural ejection orifices aligned on the recording head
102
as viewed from the direction of an arrow Z in FIG.
1
. Indicated with the reference numeral
201
in
FIG. 2
are orifices aligned on the recording head
102
.
In
FIG. 1
, the reference numeral
103
designates a convey roller. The convey roller
103
rotates in the direction of the arrow while holding a recording paper P in cooperation with an auxiliary roller
104
. The rotation of the paper feed roller
103
in cooperation with that of the auxiliary roller
104
enables the recording paper P to be conveyed along the Y direction as a sub-scan direction from the upstream side to the downstream side. The reference numeral
105
designates feed rollers, which are operative not only to feed the recording paper P, but also to hold the same therebetween in the same manner as between the rollers
103
and
104
. The reference numeral
106
designates a carriage for supporting and moving the four ink cartridges during printing. The carriage
106
is placed at a home position (h) indicated with a dotted line during standby or when the recording head needs recovering.
The carriage
106
located at the home position before printing is initiated to move along the direction indicated with an arrow X in
FIG. 1
in response to input of print start instructions. As the carriage
106
moves, recording is performed by ejecting ink from the plural ejection orifices
201
formed on the ejection orifice surface of the recording head
102
on the basis of recording data. After completion of printing data up to the rear end of the line, the carriage
106
returns to the home position and starts moving again in the X direction to print data for the next line.
In the case of image printing, various factors such as color development, gradation and uniformity are required. Uniformity is critical to image printing, especially when slight variations in nozzles occur in the process of manufacturing recording heads. It is known that the slight variations in nozzles affect the ink ejection amount and direction of each nozzle to cause density irregularities and the like, resulting in a decline in the quality of a finally printed image.
Referring to
FIGS. 3 and 4
, a specific example of such a decline in the quality of an image will be described. Schematically shown at (a) of
FIG. 3
with the reference numeral
31
is a recording head in which a row of eight nozzles
32
is provided. The reference numeral
33
designates ink droplets (hereinbelow referred to as ink droplets or simply as the ink) ejected from the nozzles
32
. Shown at (b) of
FIG. 3
is an example of an image formed by ejecting the ink periodically from the row of the nozzles of the recording head
31
. As shown, eight dots are recorded by ejecting the ink from each of the nozzles while moving the recording head. Further, (c) of
FIG. 3
is a graph showing optical density of the image shown at (b) of
FIG. 3
, choosing density as the abscissa.
It is ideal that the same amount of ink droplets is ejected from the recording head
31
in the same direction as shown at (a) of FIG.
3
. If such ideal ejection is attained, the same sized dots will be hit on the paper surface as shown at (b) of
FIG. 3
, thus obtaining a uniform image without any density irregularity as a whole as shown at (c) of FIG.
3
.
However, if variations in nozzles occur as discussed above and printing is performed as shown in
FIG. 3
without any compensation for the variations, the size and direction of the ink droplets ejected from the nozzles will vary to cause density irregularities.
FIG. 4
is a schematic diagram for explaining the density irregularities caused when the variations in nozzles occur in the recording head. In
FIG. 4
, (a), (b) and (c) correspond to (a), (b) and (c) of
FIG. 3
, respectively. In other words,
FIGS. 3 and 4
show a comparison between ideal recording and an actual state in which recording is performed with nozzles varying from one another.
Shown at (a) of
FIG. 4
is a state in which variations occurs in the recording head and hence in the size and direction of ink droplets ejected from the nozzles of the recording head. As shown at (a) of FIG.
4
, if the size and direction of ink droplets ejected from the respective nozzles vary, the ink droplets may be hit on the paper surface as shown at (b) of FIG.
4
. This cause indicates the existence of blank parts that do not meet 100 percent of the area factors periodically, or excess dots overlapped one upon another to the contrary, or the occurrence of a white streak as shown in the center. The group of dots hit in this state shows a density distribution as shown at (c) of
FIG. 4
in the direction in which the nozzles are aligned, resulting in such a phenomenon that it is perceptible to the human eye as density irregularities. Variations in paper feed amount may also make the streak conspicuous.
To take measures against the above-mentioned density irregularities, Japanese Patent Laid-open No. 06-143618 discloses a method of reducing the density irregularities. Referring to
FIG. 5
, the method will be described below in brief.
The recording operation as shown in
FIG. 5
is completed by performing scanning of the recording head
31
three times for a recording area as shown at (b) of
FIG. 3
or
4
. Shown at (a) of
FIG. 5
with the reference numbers
31
a
,
31
b
and
31
c
are relative positions of the recording head
31
at the fist, second and third scans, respectively. In this recording operation, the recording head
31
and the recording paper are moved relative to each other along a sub-scan direction
Kanda Hidehiko
Moriyama Jiro
Nakagawa Yoshinori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Judy
Stewart Jr. Charles W.
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