CN100377879C - Inkjet Fault Tolerance Method - Google Patents

Abstract

A method of printing that recognizes that a portion of an image will not print due to equipment failure and, if possible, moves ink dots laterally or vertically to an adjacent row or column in order to alleviate the visual failure to print in the original position Effect.

Description

Inkjet Fault Tolerance Method

This application is a divisional application of the application dated June 30, 2000, the application number is 00819709.1 (PCT/AU00/00752), and the title of the invention is "Inkjet fault-tolerant device and method".

technical field

This invention relates to digital printing, and more particularly to printing using devices that eject ink onto a printing substrate. But the use of the present invention is not limited to inkjet printing equipment, it can also be applied to laser printers, LED printers and digital photocopiers.

Background technique

In an inkjet printing device, the printhead has an array of nozzles through which ink is selectively ejected onto the substrate as the substrate is moved relative to the printhead. The printhead can print horizontal bands by scanning across the substrate, or, in the case of a full page width, the printhead can print longitudinally along the length of the page. If one nozzle becomes clogged, this results in multiple horizontal blank lines in the case of scanning printheads and a single blank vertical line in the case of pagewide printheads. Such blank lines are undesirable because they reduce the quality of the print.

Contents of the invention

The present invention provides a method of correcting image printing by which the visual effects of one or more clogged nozzles that are noticeable to a viewer's eye in normal use can be reduced or effectively eliminated. Of course, the invention is also applicable to other forms of printing where, whether passive or active, a device is repeatedly used to produce dots of ink on a substrate, etc. The invention is also applicable to laser printers, LED printers, and photocopiers, where failure of the imaging drum or light source may cause repetitive errors in the images produced. The term image is used in this article in a broad sense to refer to any printed content such as text and line drawings.

According to one aspect of the present invention there is provided a method of modifying an image to be printed by a digital printing device which prints the image onto a surface using a plurality of actuatable components to compensate for the actuatable components A failure of at least one of the malfunctioning components to correctly print ink at one or more specific locations, the method comprising the steps of:

a) identifying at least one of said faulty components to determine said one or more specific locations;

b) moving the planned printing position from at least one of said specific positions to a shifted printing position which is arranged in a row but which is not part of the printed dot matrix of the original image;

Wherein the specific location refers to a planned printing location of at least one of the faulty components.

In another broad aspect, the present invention provides a method of correcting an image to be printed by a digital printing device that prints an image using a plurality of similar components to compensate for a failure of the device to correctly printing ink, the method comprising the steps of: identifying said one or more specific locations, and for at least one specific location planned to be printed by a first of said plurality of parts, applying the plan to the specific location in the image The printing position of the dot is moved to a shifted position not already used by other dots in the image, whereby a second printing of the plurality of components is scheduled for at least some of the inks at the shifted position.

In other broad aspects, the present invention provides a printer having an array of devices capable of ejecting rows of dots onto a substrate, and with respect to the row of devices, said substrate is positioned in a direction substantially perpendicular to said rows of dots. direction mobile device, the printer includes:

a) means for determining whether one or more of the above-mentioned devices are not functioning properly;

b) control means which analyzes the image to be printed, determines when the ink drop should be printed by activating the failed device, and moves the position of the dot in the printed image so that the dot can be printed by activating one of the printing devices on either side of the failed device come out.

Ink dots intended to be printed by a malfunctioning printing device may move laterally, vertically, or both. It is preferable to be able to move the ink to a position closest to the original position.

A malfunctioning printing device may produce one or more defective lines in the printed image, so it is preferable to alternately move the ink dots to both sides of the defective line. Ink is preferably only moved laterally relative to the line, but ink may also be moved both longitudinally and transversely and longitudinally along the line if no printing position is available in the same line. Ink can be moved up or down from the original row position.

Description of drawings

For a better understanding of the present invention, please refer to the accompanying drawings and the description of the preferred embodiments, wherein,

Figure 1 is a schematic diagram of a set of nozzles of an inkjet printhead.

FIG. 2 is a schematic diagram of an array of ink dots formed by the print head in FIG. 1 without error correction operations.

Figure 3 is a schematic diagram of the same ink dot array as that shown in Figure 2 formed by the printhead of Figure 1, but with error correction operations.

FIG. 4 is a schematic diagram of another dot matrix formed by the printhead of FIG. 1 without error correction.

Figure 5 is a schematic diagram of the same dot matrix as shown in Figure 4 formed by the printhead of Figure 1, but with error correction operations.

Detailed ways

As shown in FIG. 1, a printhead 10 has an array of nozzles 12 arranged in a row. For ease of illustration, only 14 nozzles are shown in the figure, but in fact, a row of nozzles may include tens or thousands of nozzles. The paper passes under the printhead in a direction substantially perpendicular to the nozzle line, as indicated by arrow 14 . The print head can be fixed or movable. As the paper passes under the printhead, nozzles A through N selectively print a pattern of ink dots onto the paper as needed. The array is composed of a series of rows and columns, the distance between them is determined by the distance between the nozzles and the minimum paper feeding step. While it is preferred that the points be equally spaced horizontally and vertically, this may not necessarily be possible due to the different mechanisms for controlling the distance. The printhead can use a pagewide printhead or a smaller printhead that scans along the paper to lay down a series of horizontal print bands.

For the sake of illustration, assume that nozzles a-g and i-n are functioning properly, while nozzle h is not functioning properly or not at all for some reason. Meanwhile, it is assumed that the diagnostic system of the printer (should be known to those skilled in the art) has detected that the nozzle h is not working properly. Usually, the nozzle does not work mainly because the nozzle is partially or completely blocked, resulting in insufficient ink or even no ink in the printed dot.

Figure 2 is a schematic illustration of a portion of a print job printed by printhead 10 without error correction, where there is a blank column, marked "h", for nozzle h, and columns a-g and i-n have been correctly selected for printing. Depending on whether the printhead 10 is a pagewidth printhead or a scanning printhead, this will result in one or more blank lines in the print job. The unshaded circles numbered 16, 18, 20 and 22 represent ink drops that would have been printed to column h, but were not. Figure 3 is the same image printed by printhead 10, but it has been subjected to error correction processing according to an embodiment of the present invention.

As mentioned above, the paper passes the print head in the direction of arrow 14 so that row 1 is printed first. In row 1, point 16 should be printed at column h. Since the nozzle h cannot work normally, the control system judges whether the adjacent nozzles g and i need to print ink dots. Since neither nozzle is required to print a dot of ink, the control system selects one of columns g and i to place a dot in that corresponding column instead of column h.

The control system usually prints additional ink drops alternately on both sides of the defective nozzle, so the preferred printing position should be the opposite side of the last printed ink dot. Of course there are situations where there is no previous data, for example just after a malfunction of the nozzle was detected, or when the printer was restarted. In this case, the control system will choose to print in the left or right column.

Because column g and column i are both "empty", the control system chooses to print a single ink dot at position g according to the above principles.

There are no dots on column h in row 2, so no extra dots need to be added.

Row 3 needs a point 18 on column h, and both column g and column h are empty, because the extra dot printed last time (at row 1) was printed in column g, so this time the extra ink dot prints in column i.

There is also a print point 20 on column h in row 4, but, this time, both column g and column h require points. So there is no extra dot in row 4. In row 5, column h is not required to print dots, and both column g and column i are empty. Since the last extra ink dot was printed in column i, row 5, column g is selected to print the dot that was originally planned to be printed in row 4, column h.

Line 6 requires a print point 22 also on column h, but this time, both column g and column h are already occupied. Therefore, it is necessary to go to the next line, line 7, to print additional ink dots. In row 7, there is no planned printing point in column h or column g, but there is a planned printing point in column i. It will be recalled that dot 20a is printed in column g, so the preferred location for additional ink dot 22a this time should be column i. However, this position is no longer free, so this point can only be printed in column g, although this will cause the next extra ink point to still need to be printed in column g. Although this may appear unbalanced at the micro level, it is still balanced at the macro level.

Figures 4 and 5 show two sets of print jobs that, on average, require more dots than Figures 2 and 3. Here, it is still assumed that the nozzle h does not work normally. Row 1 is printed first, and point 30 needs to be printed in column h. Since only column g is free, point 30a is printed in column g. Column h of row 2, row 3 both need to print a dot, but since column g is not available, both dot 32a and dot 34a are printed in column i, regardless of the "need" for alternate printing.

Lines 4 and 6 do not need dots, but lines 5 and 7 do. Since only one line is available, points 36a and 38a are printed into lines g and i respectively.

In addition, the present invention may also print large ink dots in non-shifted locations adjacent or near unprinted locations, and/or print additional ink dots between rows adjacent or near unprinted locations. This is usually achieved by operating the printer's controls to activate the printing nozzles adjacent to the faulty nozzle, as a corresponding printing regime that either prints larger dots or prints dots at a higher frequency.

Although the technique described here only considers lines printed after the original line when determining where to place ink dots, it will be appreciated that the look-ahead feature can be used to place dots on lines preceding the original line. For example: If you follow the backward-looking guideline, you should place the dot to the right of the faulty nozzle; but if you look forward, you will find that the next few lines in this column need to print ink dots, then a better solution is to place the Ink dots are printed in the left column of the original row. Likewise, this embodiment can also translate the point to the next row. With the look-ahead feature, the dot required to be printed can be printed to the line before the usual required position according to the needs of the printing effect.

In addition, the present invention can also be used together with laser printers, LED printers, photocopiers and other digital printers that use independent components to print different ink dots. For example, in an LED printer, an LED may have a problem; in a laser printer, a photosensitive imaging drum may have a problem. In both cases, moving the dots can hide or mitigate imperfections created by equipment failure, improving the visual quality of the image.

Claims (10)

1. A method of modifying an image to be printed by a digital printing device which prints said image onto a surface using a plurality of actuatable components so as to compensate for at least one faulty component of said actuatable components failure to correctly print ink at one or more specific locations, the method comprising the steps of: a) identifying at least one of said faulty components to determine said one or more specific locations; b) moving the planned printing position from at least one of said specific positions to a shifted printing position which is arranged in a row but which is not part of the printed dot matrix of the original image; Wherein the specific location refers to a planned printing location of at least one of the faulty components. 2. The method of claim 1, wherein the planned printing position is moved laterally. 3. The method of claim 1, wherein the planned printing position is moved longitudinally. 4. The method of claim 1, wherein the planned printing position is moved both laterally and longitudinally. 5. The method of claim 1, wherein when the planned print position can be moved to two or more possible positions, the selected shifted print position is subject to any nearby shift The position of the ink or the position of the most recently printed displaced ink or both. 6. The method of claim 1, wherein when the image includes a plurality of specific positions aligned in a line, about 50% of the shifted print positions are on one side of the line, and 50% are on one side of the line. on the other side of the line. 7. The method of claim 1, wherein when the image includes a plurality of specific locations arranged in a line, the ink relative to the line: a) lateral movement only; or b) Horizontal and vertical movement. 8. The method of claim 1, wherein the shifted printing position is directly adjacent to the original position in the horizontal direction or the longitudinal direction or both directions. 9. The method of claim 1, wherein additional ink is printed adjacent to the respective specific locations in the form of large sized ink drops. 10. The method of claim 1, wherein additional ink is printed adjacent to each specific location in the form of additional ink drops.

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