Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1997-05-16
2001-02-06
Hartary, Joseph W. (Department: 2852)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S007000, C347S098000
Reexamination Certificate
active
06183071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus, as well as to a method, for recording information on a recording medium by jetting a recording liquid onto the recording medium. More particularly, the present invention is concerned with an ink jet recording apparatus and an ink jet recording method which use, as the recording liquid, a blended ink formed by mixing a plurality of types of ink. The present invention is also concerned with an ink supply system.
2. Description of the Related Art
In general, conventional ink jet recording systems employ a recording head having a plurality of ink discharge openings from which ink droplets are discharged in accordance with data to be recorded towards the recording medium so as to be deposited on the latter to record the data. This type of recording system is used in, for example, printers, facsimile machines and copying machines.
Various ink discharging techniques are available for discharging the ink as the recording liquid. For instance, a heat generating element (referred to as an “electro-thermal transducer”) in the ink channel near the discharge opening. In operation, an electrical signal is applied to the heat-generating element to locally heat the ink so as to generate a bubble in the ink, thereby causing a pressure change in the ink channel to discharge the ink in the form of a droplet. Another discharge technique incorporates an electro-mechanical conversion element such as a piezoelectric element.
Techniques are also known for recording halftone images or information using one of the known discharge methods described above. For instance, a method referred to as dot-density control method is known in which halftone recording is realized by controlling the density per unit area of dots of a constant size formed by the ink droplets. In another method known as dot-size control method, half-tone is realized by controlling the size of the recording dots.
Since the latter method, i.e., the dot-size control method, requires a complicated control to achieve delicate variation of dot size, the former method, i.e., dot-density recording method, is used more broadly.
Recording heads incorporating the above-mentioned electro-thermal transducers can be produced comparatively easily and can perform recording with high level of resolution by virtue of this ability to attain high dot density. In this type of recording head, however, it is rather difficult to delicately control the level of pressure generated by the electro-thermal transducer and, therefore, it is impossible to modulate the dot size in accordance with the information to be recorded. Consequently, this type of recording head cannot suitably be used in dot-size control type recording operation.
For the reasons stated above, dot-density control method is used as a primary recording method rather than the dot-size control method. The ordered dither method is known as one of the typical binary coding methods for realizing halftone image recording. This method, however, has a shortcoming in that the number of levels of tone or gradation is limited by the matrix size. That is to say, a larger of matrix is required to obtain a greater number of gradation levels. A larger matrix size undesirably increases the size of one pixel of recorded image constituted by one matrix, resulting in problems such as degradation of resolution.
A conditioned determination type dither method such as the error diffusion method also has been known as another binary coding method. The above-mentioned structural dither method is an independent determination type dither method which uses a binary-coding threshold independent of the input pixel, and the conditioned determination dither method varies the threshold level taking into consideration the values of pixels around the pixel in interest. The conditioned determination dither method, represented by error diffusion method, is advantageous in that gradation and resolution are made compatible at high levels and in that generation of unwanted moiré patterns in the image recorded from a printed image is greatly reduced. This method, however, suffers from a disadvantage in that coarseness of recording dots is noticeable particularly in bright regions of the recorded image, thus degrading the quality of the image. This problem is serious particularly when the recording density is low.
In order to make the coarseness of dots less noticeable, a recording method has been proposed which employs a pair of recording heads: namely, one for discharging an ink having a low dye concentration, i.e., an ink which is of a comparatively light color and which produces an image of a comparatively low thickness on the recording medium (referred to as “thin ink”, hereinafter) and one for discharging an ink having a high dye concentration, i.e., an ink which is of a comparatively dark or thick color and which produces an image of a comparatively thick image on the recording medium.
According to this multi-level tone recording method using plural types of ink having different levels of thickness of the same color, the gradation is improved particularly in the highlighted region of the recorded image when the number of levels is increased, with the result that the coarseness of dots becomes less noticeable, thus improving the image quality. This is because the highlighted portion of the image is formed by light color ink dots which are inconspicuous.
FIG. 1A
is a schematic perspective view of an example of a conventional ink jet recording apparatus which relies upon the above-mentioned multi-level tone method.
Referring to
FIG. 1A
, a carriage
706
carries eight ink tanks
701
containing, respectively, thin and thick ink of black, cyan, magenta and yellow colors. The carriage
706
also carries a multi-head
702
having eight heads for discharging these different types of ink.
FIG. 1B
illustrates the discharge openings of one of the heads on the multi-head
702
, as viewed in the direction of the arrow Z, i.e., from the reverse side of the drawing sheet, of FIG.
1
A.
The thick and thin inks of black, cyan, magenta and yellow are represented here by Kk, Ku, Ck, Cu, Mk, Mu, Yk and Yu. These discharge openings are arranged in parallel arrays in the direction of the arrow Y. These arrays, however, may be slightly inclined within the X-Y plane. In such a case, the discharge of inks from the respective discharge openings is conducted with predetermined time lags or delay, while the head
702
travels in the direction of the arrow X.
Referring again to
FIG. 1A
, a sheet feed roller
703
rotates in the direction of the arrow to cooperate with an auxiliary roller
704
in feeding a recording paper sheet
707
in the direction of the arrow y while imparting a certain level of tension to the sheet
707
. Numeral
705
denotes another sheet feed roller which feeds the recording paper sheet
707
and functions to impart a certain level of tension to the recording sheet
707
in a manner similar to the roller pair
703
,
704
. The carriage
706
is stationed at a home position “h” illustrated by broken line when recording is not conducted and when a discharge recovery operation is being conducted. A recovery mechanism (not shown) such as capping means holds the multi-head in a predetermined condition.
The carriage
706
stationed at the home position “h” commences its movement in the direction of the arrow X along a carriage guide shaft
798
, in response to a record start instruction. During the movement of the carriage, thick and thin inks of four colors are selectively discharged from the n discharge openings
801
of the multi-head
702
, based on a carriage position signal which is produced by a linear encoder
709
in accordance with the travel of the carriage, whereby an image fraction of a width corresponding to the width D of the arrays of the discharge openings on the recording head. As a result of this scanning operation, ink droplets reach the recording sheets in such an order or sequence of colors that
Akiyama Yuji
Gotoh Fumihiro
Hirabayashi Hiromitsu
Kanda Hidehiko
Kashino Toshio
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hartary Joseph W.
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