Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-12-07
2001-01-30
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06179402
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus with a multi-recording-element head.
With the wider use of a computers and communication machines, digital image forming machines using a recording head of an ink jet type or a thermal transfer type are increasingly used.
In an image recording apparatus using a recording head, a multi-element (image recording element) head is used for the recording head in order to increase the recording speed. In the case of the ink jet recording head, a multi-nozzle head having plural number of ink ejection nozzles is widely used, and in the case of the thermal transfer type head, plural heaters are provided.
It is difficult to produce multi-element heads wherein all of the elements in each head perform identically, and therefore, it is substantially unavoidable that the properties of the different image recording elements will vary. In the case of the ink jet multi-element head, for example, the dimensions and/or configurations of the several nozzles in one recording head may be different, and in the case of the multi-element head of the thermal transfer type, the configuration and/or the resistance of the heaters can vary. The variation of the properties of the image recording elements results in the variations in the sizes and densities of the dots provided by the image recording elements, and therefore, results in image density non-uniformity in the recorded image.
Some proposals of solutions to this problem have been made by adjusting the signals supplied to the image recording elements.
Referring first to
FIG. 2
, there is shown an example of a multi-element head
1
provided with a plurality of recording elements
2
. It is assumed that when the uniform electric signals are supplied to the image recording elements, as shown in
FIG. 3
, the resultant image density is non-uniform as shown by FIG.
4
. To avoid the non-uniformity, the supplied signals are adjusted as shown by
FIG. 5
, by which a large input is supplied to the image recording element providing the low density, and a small input is supplied to the image recording element providing the high density. By doing so, the resultant recording is as shown by FIG.
6
.
In the case of the recording system in which the size or the dot density is adjustable, the dot sizes are changed in accordance with the inputs. In the case of the ink jet recording system using piezoelectric elements, the driving voltage or the width of the driving voltage pulse applied to each of the piezoelectric element is changed in accordance with the input signal. In the case of the thermal transfer system, the driving voltage or the pulse width applied to the heater is changed in accordance with the input signal. By doing so, the dot sizes and dot densities by the recording elements are made uniform, as shown in FIG.
6
.
There is also the case wherein the dot size or the image density of the dots are not changed, or it is difficult to change the number of dots in accordance with the input. Here, a large number of dots are formed by an image recording element providing the low density image, and a smaller number of dots is presented by an image recording element providing a high density image. By doing so, the density distribution is made uniform as shown in FIG.
6
.
It is possible to correct the image density variations. However, there arises a problem.
That is, although the density variation can be corrected once, the density variations may still change thereafter, and so the adjustment of the input signal is no longer proper. For example, in the case of the ink jet recording head, the density distribution may change due to deposition of ink pigment adjacent the ink outlet nozzle and/or be due to foreign matter deposited externally. In the case of the thermal transfer type, the image density distribution may change due to deterioration of or change in the heater elements. The initial input adjustment is not effective to correct the changing density non-uniformity. In some cases, the initial adjustment makes the situation worse.
U.S. Ser. No. 480,041 filed on Feb. 14, 1990 and assigned to the assignee of the present application proposes one way to reduce the image variation. However, there still remain the problems to be solved.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the present invention to provide an image recording apparatus wherein the variation in recorded dot's variations over time and/or with use can be minimized.
It is another object of the present invention to provide an image recording apparatus wherein variations the individual recording elements can be corrected.
According to an embodiment of the present invention, there is provided a recording apparatus, comprising a recording head having plural recording elements for recording an image in accordance with input image data, detecting means for detecting density variation of the recording elements at predetermined timing and adjusting means for adjusting driving signals applied to the recording head on the basis of a result of detection by detecting means.
According to this embodiment, the adverse effects due to changes with use or time in the respective recording elements can be minimized.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
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McAdams, W.H., “Heat Transmission”, pp. 368-371 (McGraw-Hill, 1954).
Herbert, Alan J., “Large Area Imaging”, Journal of Imaging Technology, vol. 10, No. 5, Oct. 1984, pp. 201-206.
Fukushima Hisashi
Suzuki Akio
Takada Yoshihiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Le N.
Vo Anh T. N.
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