Incremental printing of symbolic information – Ink jet – Controller
Patent
1998-06-15
2000-07-04
Royer, William
Incremental printing of symbolic information
Ink jet
Controller
347 37, B41J 29393
Patent
active
060846070
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an ink-type image forming device and particularly to such a device which includes a plurality of recording heads for multi-color printing.
BACKGROUND ART
An ink-jet system, one of ink recording systems, is a system in which a nozzle, filled with ink derived from an ink container, includes a heater which is driven with a pulse signal for heating the nozzle to eject an ink drop by the pressure of an air bubble that is created in the ink by the heating. In an image forming device employing such an ink-jet recording system, an image is formed using a recording head which is constituted by a plurality of nozzles aligned in line.
As shown in FIG. 11, a recording head 3 (heareinafter referred to as only "head") mounted on a carriage is moved in a main-scanning direction (X) to successively print a multiple of columns 17 one by one on a sheet of paper 15 to form one band of an image. Then, the paper sheet 15 is moved in a sub-scanning direction (Y) to form a second band of the image which adjoins the first band. In order to form a full-color image, a plurality of recording heads are used which eject ink drops of different colors, e.g., cyan C, magenta M, yellow Y and black K, to perform a printing with the colors overlapped with each other.
However, the printing with the plurality of recording heads of different colors as described above to form a full-color image suffers from the following drawbacks. As shown in FIG. 12, misalignment or deviation D1 in relative position of the plurality of heads could be present among the heads in a lateral or main-scanning direction. Such deviation D1 will cause a vertical stripe pattern in a printed image. FIG. 12 shows an example in which only the head of magenta M is misaligned leftward by an amount D1 with respect to other heads. Likewise, as shown in FIG. 13, deviation D2 in a vertical or sub-scanning direction could also be present among the plurality of heads. Such deviation D2 will cause a horizontal stripe pattern to appear in a printed image. FIG. 13 shows an example in which only the head of magenta M is misaligned downward by an amount D2 with respect to other heads. Thus, the deviation among the heads could degrade a printed image.
There is an ink-type image forming device which synchronizes the ejection of ink drops by using a linear scale 301, which has slits 303 regularly provided therealong for every dot position, and a linear sensor 302, which is movable along the linear scale 301 to detect the presence/absence of the slits at any position thereof, as shown in FIG. 14 to eject ink drops at accurate points corresponding to individual positions in the main-scanning direction of the heads. This type of image forming device, when performing a bi-directional (or two-way) printing in which printing is made in both forward and backward paths of the heads moving along the main-scanning direction, as shown in FIG. 15(a), in the forward path a delay time d1 is created from the detection of a slit to the actual ejection of an ink drop whereas in the backward path a delay time d2 is similarly created. Thus, the sum of the delay times makes (d1+d2). The sum of the delay times (d1+d2) could degrade a printed image because of the deviations (D5) of ejected positions of ink drops between the forward and backward paths in spite of attempting to print dots at the same position P. The image degradation is significant especially when printing a line drawing. For example, as shown in FIG. 15(b), when ideally one vertical line 151 is to appear, two parallel dashed lines 12 would be printed.
The configuration of a head is classified into two types: an integrated type in which an ink container is integrated with an associated head as shown in FIG. 16(b) and a separate type in which a head 3 is separate from an ink container 3' as shown in FIG. 16(a).
The integrated type recording heads are handled as consumable supplies which are exchanged arbitrarily by a user when the ink container runs short of ink. Therefore, each time of the ex
REFERENCES:
patent: 4675696 (1987-06-01), Suzuki
patent: 5404020 (1995-04-01), Cobbs
patent: 5600350 (1997-02-01), Cobbs et al.
Copyer Co. Ltd.
Royer William
Tran Hoan
LandOfFree
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