JP2004501008A - Inkjet using surplus ink dots is resistant to defects - Google Patents

Abstract

An inkjet device.
A print that prints extra dots on adjacent rows to identify parts of the image that are not printed due to equipment failure and, if possible, reduce visual effects due to defects that are not printed exactly in place. Method.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to digital printing, and more particularly to printing using a device that ejects ink onto a substrate to be printed. However, the present invention is not limited to the ink ejection device, but can be applied to a laser printer, an LED printer, and a digital copier.
[0002]
[Prior art]
In an ink ejection device, a printhead has an array of nozzles that selectively ejects ink onto a substrate that moves relative to the printhead. The printhead can be printed by scanning across the substrate and printing the horizontal width, or can pass along the length of the page if the printhead is a full page width printhead It is. In the case of a scanning printhead, when a nozzle is blocked, a plurality of horizontal blank lines are generated, and in the case of a page width printhead, one vertical blank line is generated. Such a blank line is undesirable because it degrades the quality of the printed result.
[0003]
[Problems to be solved by the invention]
The present invention provides a method for improving prints in an image to reduce or effectively eliminate the visual effects caused by one or more such blocked nozzles that are visible to a viewer in normal use. I do. However, the invention is applicable to other forms of printing where the elements (passive or active) are used repeatedly to create dots of ink or the like on the substrate. INDUSTRIAL APPLICABILITY The present invention is applicable to laser printers, LED printers, and copiers in which a defect in an image drum or a light source may repeatedly cause a defect in a created image. The term "image" used above and in the detailed description and claims of the invention is to be interpreted broadly and includes any printed matter, such as text, diagrams, and the like.
[0004]
[Means for Solving the Problems]
In one broad form, the present invention provides a method of modifying an image that is digitally printed by a printing device that compensates for a failure to accurately print a dot of ink at a particular location. The method includes:
(1) identifying the particular one or more locations; (2) comparing at least one additional location adjacent or adjacent to the respective particular location with respect to the request by the image data. In another broad form of the step of adding additional dots, the present invention provides an activatable element array for arranging a row of dots on a substrate upon activation, and an element array substantially perpendicular to the row of dots. Means for moving the substrate relative to the rows. The printer includes:
[0005]
Means for determining whether one or more of the above elements does not operate correctly Analyze the image or image data and identify one or more specific ink dots to be printed by activation of the incorrectly operating elements. A control means for identifying one or both elements on both sides of the failed element to identify the position and compare with the request for image data to create an excess ink dot. If the location to be used is not used by the image, it can simply be placed beside each particular location. One or more surplus dots can be placed laterally and above or below, or both above and below each particular location. Two or more surplus dots can be provided within each quadrant relative to each particular location.
[0006]
The surplus ink dots can be of the same size as the dots normally required by the image data, or larger or smaller. The ink dots adjacent to the place where the surplus dots are printed and required by the image data can be reduced in size in accordance with the surplus ink dots.
[0007]
Depending on the “regular” ink dot size and interval, the number and size of the surplus dots, and any size change of the “regular” dots adjacent to the surplus dots, the surplus dots can be replaced with other surplus dots or “regular” dots. It is possible for the dots to overlap, or both, or to be identifiable non-overlapping dots. The surplus dots are preferably printed on both sides of a specific position.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be more fully understood from the following description of non-limiting preferred embodiments and figures.
[0009]
Referring to FIG. 1, a printhead 10 has an array of inkjet nozzles 12 arranged in a row. For illustration purposes, only 14 nozzles are shown, but in practice there may be tens to thousands of nozzles in a row. The paper passes under the printhead in a direction substantially perpendicular to the line of inkjet nozzles, as indicated by arrow 14. The printhead may be a fixed head or a moving head. As the paper passes beneath the printhead, the inkjet nozzles AN selectively operate to place an array of ink dots on the paper. The array is a series of rows and columns, the spacing of which depends on the spacing of the inkjet nozzles and the minimum feed step, respectively. It is preferable that the horizontal and vertical intervals of the dots be the same, but they need not necessarily be realized because the factors of the respective intervals are different. The printhead may be a hedge-width printhead or a smaller printhead that scans across the page and prints laterally to position the head across the width of a series of prints. May be used.
[0010]
For purposes of illustration, it is assumed that inkjets ag and in operate correctly, but for some reason inkjet h does not operate correctly or does not operate at all. It is also assumed that the printer diagnostic system, as will be understood by those skilled in the art, has also detected that nozzle h is not functioning correctly. In most cases, a malfunctioning element will partially or totally occlude, resulting in improper or no ink placement on the paper.
[0011]
Referring to FIG. 2, a print portion made with the printhead 10 without correcting for defects is schematically illustrated. Here, a blank line described by “h” corresponding to the inkjet h is shown. On the other hand, rows ag and in are correctly and selectively printed. This causes one or more blank lines to appear in the print, depending on whether the printhead 10 is a full page width printhead or a scanning printhead. The white circles with the numbers 16, 18, 20, 22 correspond to ink drops that are to be printed in row h but are not printed. FIG. 3 shows the same image printed by the printhead 10 with defect correction, according to an operational embodiment of the present invention.
[0012]
Referring to FIG. 3, the controller activates the elements for rows g and i at a higher than normal frequency as soon as a dot of ink attempts to be placed on row h. As a result, as shown by the dot 24, extra dots are created and arranged between regular dot rows. Depending on the column spacing, the extra dots may overlap with the “regular” dots on the upper and lower rows, or may be separated from the upper and lower rows. In the prints of FIGS. 2 and 3, dots are required at only about 50% of the possible positions on row h. Therefore, an extra dot is created by the controller only in the row before and after the dot to be printed on the row h. However, the creation of the surplus dots may be performed before or after each dot or in two or more rows of both. Further, when dot creation is not required on an adjacent row, the controller creates an extra dot between the “regular” columns and an extra dot at the “regular” position of the corresponding row. May be created. This can be seen in columns 1 and 3 of row g where the extra dots are printed at the "regular" position. FIG. 4 shows a print in which dots 30, 32, 34, 36, 38, 40 on a row h, that is, six dots on eight columns are required. FIG. 5 shows the result of performing the defect correction operation. It can be seen on rows g and h where the extra dot was created between all "regular" columns and was also created at the "regular" position. This creates an overlapping, continuous array of regular and extra dots on rows g and i, thus significantly reducing the white space caused by unprinted obstructions on row h.
[0013]
Depending on the performance characteristics of the actuator, the extra dots may be the same size as the “regular” dots, or larger or smaller as desired or required. For example, a mechanical ink ejector can operate at 50 Hz, ie, eject 50,000 drops of ink per second. The ejector can be used in a "home" type printer that only needs to operate at, for example, 25 KHz for the paper feed speed. That is, each ejector can operate at 50 KHz to create dots between rows without increasing the size of the dots.
[0014]
Even if the normal activation frequency is generally higher than one half of the "maximum" design frequency for the printhead, an individual ink ejector can be activated at twice its normal activation frequency. In a micromechanical ink ejector that relies on thermal flexion, the micromechanical ejector may return to its normal quiescent state and / or the ink reservoir may be operated prior to the start of the next "regular" ink drop ejection cycle. It may be necessary to narrow the pulse width of the drive signal and / or reduce the voltage of the drive signal so that it is replenished. A smaller pulse width / reduced voltage creates a smaller redundant dot. Alternatively, the ejector may be activated without changing the pulse width and voltage of the drive signal. This may result in the actuator not returning to its quiescent state and / or the ink reservoir not being refilled before the quiescent cycle begins, or both. This produces smaller ink drops for the dots on the “regular” and extra rows. Still, this effect is at a satisfactory level.
[0015]
It will be appreciated that this technique is applicable to other digital printing technologies where the imaging system can also cycle faster than normal. For example, a laser printer scans rapidly with a laser beam across an imaging drum, so that less than one of two scans is actually used. An extra dot may be created using a scan not used at this time. Similarly, light emitting device printers may operate light emitting devices at higher than normal cycles to achieve the same result.
[0016]
Also, it is not possible to print extra large dots next to or adjacent to non-printed locations without shifting, and / or to print extra dots between adjacent or non-printed columns. It is within the scope of the present invention.
[0017]
In the technology described above, only the consideration of the columns printed after the original column is described in determining the dot arrangement location. However, if the look-ahead characteristic is used, the position of the dot printed on the column printed before the original column is considered. It will be appreciated that the placement of the dots is possible. For example, using a non-read-ahead criterion, the dots are placed in the row to the right of the failed nozzle, but look ahead, and for the next few columns, the dots are legally required on that row. In this case, it is clear that better results can be obtained by arranging dots on the left row in the original column. Similarly, in the above-described embodiment, the dot may be replaced with the row to be printed next to the position that is normally desired. If good results are obtained, dots may be printed on rows that are printed before the legitimate desired position using the look-ahead feature.
[0018]
It will be appreciated that this technique can also be used for laser printers, LED printers, copiers and other types of digital printers, where the placement of the ink dots depends on the individual activation of elements or components. . For example, LEDs in LED printers may fail, or defects may occur in the photoconductive drum of a laser printer. In both cases, shifting the dots can hide or reduce visual effects due to defects in elements or components.
[Brief description of the drawings]
FIG.
FIG. 2 is a schematic view of a set of nozzles of an inkjet print head.
FIG. 2
FIG. 2 is a schematic diagram of an array of ink dots formed by the print head of FIG. 1 when no defect correction operation is used.
FIG. 3
FIG. 3 is a schematic diagram of the same array of ink dots as FIG. 2 formed by the print head of FIG. 1 when using a defect correction operation.
FIG. 4
FIG. 2 is a second schematic diagram of an array of ink dots formed by the printhead of FIG. 1 without a defect correction operation.
FIG. 5
FIG. 5 is a schematic diagram of the same array of ink dots as FIG. 4 formed by the print head of FIG. 1 when using a defect correction operation.
[Explanation of symbols]
Reference Signs List 10 Print head 12 Ink jet nozzle 14 Paper passage direction 16, 18, 20, 22 Non-printed ink dots 24 Extra dots 30, 32, 34, 36, 38, 40 Ink dots that need to be printed but are not printed

Claims (19)

A method of modifying an image that is digitally printed by a printing device to compensate for the drawback of failing to accurately print dots of ink at specific locations, comprising:
(1) identifying the particular one or more locations;
(2) adding at least one additional dot at at least one additional position adjacent to or in close proximity to each of said specific positions as compared to the request by the image data;
A method that includes The method of claim 1, wherein the at least one additional location is located laterally of the particular location. The method of claim 1, wherein the at least one additional location is located longitudinally of the particular location. The method of claim 1, wherein the dots are printed in rows and the at least one additional location is located between the rows. The method of claim 1, wherein the dots are printed in rows and at least two additional locations are located between adjacent rows for each particular location. The method of claim 1, wherein the dots are printed in rows, and wherein at least two additional locations are located between adjacent rows on the same side of each particular location. The method of claim 1, wherein the dots are printed in columns and rows, and wherein the at least one additional location is located on one or both rows on both sides of the particular location and between the columns. The method according to claim 1, wherein the dot size of the dot at the additional position is the same size as the dot at the position required by the image data. The method according to claim 1, wherein the dot size of the dot at the additional position is smaller than the dot size of the dot at the position required by the image data. The method according to claim 1, wherein a dot size of a dot at a position required by the image data adjacent to an additional position is smaller than a dot size of a dot at a position required by the image data. A printer comprising: a row of activatable elements for arranging rows of dots on the substrate when activated; and means for moving the substrate relative to the rows of elements in a direction substantially perpendicular to the rows of dots. Means for determining whether one or more of said elements does not operate correctly;
Analyzing the image or image data, identifying one or more specific locations of the ink dots to be printed by activation of the incorrectly operating elements, and comparing excess image ink requirements with the image data requirements. Control means for identifying one or both elements on both sides of the failed element to create a dot;
A printer comprising: 12. The printer according to claim 11, wherein the control means adjusts the size of dots arranged on the same row at the respective specific positions by one or both elements on both sides of the failed element. The control means adjusts a size of a dot arranged by one or both elements on both sides of the failed element in at least one row adjacent to or adjacent to the row at the specific position. The printer according to claim 11, which performs the following. If a dot is not created or a minute dot is created by the activation of the incorrectly operating element, a dot created by the activation of one or both of the elements adjacent to the incorrectly operating element The printer of claim 11, wherein the size of the printer is increased. The device of claim 11, wherein the element is a thermal ink ejection element and the control system activates the ejection element for a longer period and / or provides a greater drive signal. Printer. The printer according to claim 11, wherein the element is a light emitting element, and an amount of light emitted by the light emitting element is adjusted. 12. The printer of claim 11, wherein the elements are part of a photoconductive imaging drum and the adjusted dot size of the adjusted dots is adjusted by changing the amount of light to which each of the elements is exposed. The printer of claim 11, wherein at least some adjusted oversized dots contact or overlap adjacent dots. 12. The printer of claim 11, wherein the adjusted size dots do not contact or overlap adjacent dots.