Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-11-06
2004-12-28
Nguyen, Lamson D. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06834927
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an ink jet recording apparatus, that is, an image forming apparatus which forms images on recording medium by forming numerous ink dots on the recording medium by ejecting onto the recording medium, and a method for preventing an ink jet recording apparatus from forming defective images, in particular, a method for compensating for the specific unwanted properties of the recording heads of an ink jet recording apparatus, more specifically, compensating for the recording head nozzles which do not eject ink straight, recording head nozzles which fail to eject ink, etc.
In recent years, various information processing devices such as copying machines, wordprocessors, computers, etc., and also, communication devices, have come into general use. Consequently, digital recording devices employing a single or plurality of ink jet recording heads have rapidly come into general use, as one of the image forming (recording) apparatuses for the information processing devices and communication devices. Also in recent years, information processing devices and communication devices have been colorized, being therefore drastically improved in terms of visual information. Consequently, the demand for recording apparatuses higher in image quality, and for the colorization of recording apparatuses have been increasing.
In order to reduce picture element size, increase recording speed, etc., these new types of recording apparatuses employ a recording head (which hereinafter may be referred to as multi-head) comprising a plurality of integrally arranged recording elements. Each recording element comprises an ink ejection orifice and a liquid path thereto. Thus, a multi-head comprises a plurality of ink ejection orifices and liquid paths which are integrally arranged at a high density. Generally, color image forming apparatuses comprise a plurality of the above described multi-heads which correspond one for one to cyan, magenta, yellow and black inks, for example, to effect various colors.
The primary concerns in the technological field of this ink jet recording apparatus are how to improve recording speed, how to reduce recording cost, and how to improve image quality, while maintaining the above described structural arrangement. As one of the means for improving recording speed, a method in which the length of a multi-head is approximately matched with the width of recording medium, so that the multi-head has to pass the recording medium only once, has been realized.
However, this method has the following weakness. That is, for example, in order to enable a page printer to accommodate an A4 recording paper positioned so that the shorter edges become parallel to the direction in which the recording paper is conveyed through the printer, the multi-head of this page printer must be no less than approximately 30 cm in length, requiring no less than 7000 nozzles, provided that the resolution is 6000 psi. From the standpoint of yield, it is extremely difficult to produce a large number of flawless multi-heads having this many nozzles. Further, because of the shear number of nozzles, there is no guarantee that all nozzles are equal in performance. Moreover, there is a substantial possibility that some nozzles will stop ejecting ink while in use.
The head shading technologies for compensating for the nonuniformity among the nozzles, in terms of the amount by which recording liquid is ejected therefrom, as well as in terms of the deviation of the liquid droplets in terms of the target landing points have been attracting attention. Further, the technologies for compensating for the failing nozzles so that even a multi-head, all the nozzles of which are not flawless, can be employed, have also been attracting attention.
According to the most commonly used head shading method, a predetermined pattern (for example, pattern in which dots are arranged in zigzags, duty ratio of which in 50%, which hereinafter may be referred to as a zigzag pattern) is printed, and the printed pattern is measured in density while establishing the positional relationship between a specific point of the printed pattern and a specific nozzle. Then, the performance of each nozzle in terms of density is calculated from the measurement, and the image formation data are modified according to the calculated performance of each nozzle.
For example, if a given nozzle is smaller in the amount of the recording liquid ejected therefrom compared to those from the other nozzles, and therefore, the area of an image corresponding to this nozzle is lower in density, the image formation data are modified so that the gradation value for the area corresponding to this nozzle is increased in order to output images uniform in density.
Further, the technologies for compensating for abnormal nozzles other than the above described nozzles which are smaller in the amount of the liquid they eject, nozzles greater in the ejection direction deviation, nozzles unable to eject, etc., have been proposed. An abnormal nozzle is treated as a nozzle unable to eject, even if it is capable of ejecting. Therefore, it may be referred to as a “non-ejection nozzle”. Thus, hereinafter, the technologies for recording images while compensating for non-ejection nozzles will be referred to simply as “non-ejection compensation technology”.
SUMMARY OF THE INVENTION
The flow resistance of an ink path is affected by production errors, sedimentation of foreign substances therein, etc. Therefore, it is more likely than not that the nozzles of a long head, such as the aforementioned long head having approximately 7000 nozzles, become different in refill properties during their service lives.
As long as the relationship between the recording conditions and refill properties of the recording head is such that the amount of the liquid to be ejected from each nozzle per unit of time is smaller than the amount by which each nozzle is refilled per unit of time, there is no problem. However, as some nozzles deteriorates in refill properties, that is, as the amount by which these nozzles are refilled per unit of time becomes smaller than the amount by which liquid is ejected therefrom per unit of time, the amount by which liquid is ejected therefrom reduces, or in the worst case, ink is not ejected therefrom. This condition will be referred to as “insufficient refill non-ejection”. It is rather difficult to determine the above described refill properties of each nozzle, based on the aforementioned nozzle check pattern for checking whether or not a given nozzle is literally a non-ejection nozzle, for the following reason. That is, this nozzle check pattern is not likely to allow a given nozzle to fail to eject as long as the given nozzle is the only nozzle among the nozzles in its adjacencies which is caused to eject ink. In other words, even if the flow resistance is increased by a piece of sedimentation
72
as schematically shown in
FIG. 7
, ink is supplied to the adjacencies of a heater
71
from the adjacencies of the sedimentation
72
. Thus, when a given nozzle is allowed to eject ink while preventing the nozzles in the adjacencies thereof from ejecting, as is when the aforementioned nozzle check pattern is printed, there is not likely to be a delay in ink supply Therefore, the nozzle ejects ink like a normal nozzle, making it difficult to determine whether or not this nozzle is normal. In other words, even if a given nozzle is recognized as a non-ejection nozzle while ink is continuously ejected from this nozzle during an image recording operation, if sometimes fails to be recognized as a non-ejection nozzle while the nozzle check pattern is printed, that is, while ink is ejected at a relatively low duty ratio.
This creates the following problems. That is, when the presence of nozzles inferior in refill properties, even though the head shading or non-ejection compensation is effective when printing the low duty areas of an image, they are not effective enough when printing the high duty areas of the image. This re
Fujimoto Yasunori
Koitabashi Noribumi
Shibata Tsuyoshi
Tsuboi Hitoshi
Yashima Masataka
LandOfFree
Ink jet recording apparatus and correcting method for image does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet recording apparatus and correcting method for image, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet recording apparatus and correcting method for image will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3295669