CN109249711B - Method of detecting malfunctioning printing nozzles at printing edge - Google Patents
Method of detecting malfunctioning printing nozzles at printing edge Download PDFInfo
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- CN109249711B CN109249711B CN201810768954.5A CN201810768954A CN109249711B CN 109249711 B CN109249711 B CN 109249711B CN 201810768954 A CN201810768954 A CN 201810768954A CN 109249711 B CN109249711 B CN 109249711B
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- 238000007639 printing Methods 0.000 title claims abstract description 174
- 238000000034 method Methods 0.000 title claims abstract description 47
- 238000012360 testing method Methods 0.000 claims abstract description 113
- 230000000737 periodic effect Effects 0.000 claims abstract description 6
- 238000004458 analytical method Methods 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 2
- 230000002950 deficient Effects 0.000 abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract 1
- 238000001514 detection method Methods 0.000 description 27
- 239000000976 ink Substances 0.000 description 11
- 238000011161 development Methods 0.000 description 7
- 230000018109 developmental process Effects 0.000 description 7
- 238000007641 inkjet printing Methods 0.000 description 7
- 238000011156 evaluation Methods 0.000 description 5
- 239000000758 substrate Substances 0.000 description 4
- 230000007257 malfunction Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000010561 standard procedure Methods 0.000 description 2
- 230000032258 transport Effects 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J29/00—Details of, or accessories for, typewriters or selective printing mechanisms not otherwise provided for
- B41J29/38—Drives, motors, controls or automatic cut-off devices for the entire printing mechanism
- B41J29/393—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/21—Ink jet for multi-colour printing
- B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
- B41J2/2142—Detection of malfunctioning nozzles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/165—Prevention or detection of nozzle clogging, e.g. cleaning, capping or moistening for nozzles
- B41J2/16579—Detection means therefor, e.g. for nozzle clogging
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/21—Ink jet for multi-colour printing
- B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
- B41J2/2139—Compensation for malfunctioning nozzles creating dot place or dot size errors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/21—Ink jet for multi-colour printing
- B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
- B41J2/2146—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding for line print heads
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J29/00—Details of, or accessories for, typewriters or selective printing mechanisms not otherwise provided for
- B41J29/38—Drives, motors, controls or automatic cut-off devices for the entire printing mechanism
- B41J29/393—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
- B41J2029/3935—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns by means of printed test patterns
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- Engineering & Computer Science (AREA)
- Quality & Reliability (AREA)
- Ink Jet (AREA)
Abstract
The invention relates to a method for detecting defective printing nozzles in an inkjet printer by means of a computer, a nozzle test pattern being printed, the nozzle test pattern comprising a certain number of water parallels of equally spaced lines printed vertically in a periodic manner, the lines being arranged one above the other, in each line a certain number of printing nozzles corresponding to a horizontal line respectively only in a periodic manner contributing to the realization of a nozzle test pattern, the printed nozzle test pattern being detected by means of an image sensor, digitized and transmitted to the computer, the start of the horizontal line of nozzle test patterns being checked in order to determine defective printing nozzles at the edge of the printing head when the nozzle test pattern is processed analytically by the computer: how much the line is geometrically deviated at the beginning of the corresponding descending row of the nozzle test pattern, the geometrical deviation of the line is checked: how large the horizontal spacing between the first line of a row of nozzle test patterns and the first line of the corresponding lower row of nozzle test patterns is.
Description
Technical Field
The invention relates to a method for detecting a faulty printing nozzle at the printing edge in an inkjet printer.
Background
The present invention is in the field of digital printing technology.
In the operation of an inkjet printer, which emits ink drops specifically through a print head target having one or more rows of printing nozzles, it is possible to form a so-called "missing nozzle" ("missing nozzles") false image. This means that: the individual printing nozzles no longer work in a functionally normal manner. This can be expressed, for example, as: so-called "white lines" appear in the printed image at such locations: at this point, the defective printing nozzle is responsible. The white line consists of a product in the form of a strip along the printing direction, which product is white in the case of monochrome printing at this location in the printed image, and is represented by color distortion in the case of multicolor printing.
The reason for missing nozzles is mostly that the printing nozzles are blocked and no ink is ejected at all. Damage in such a transport path, which transports ink to the printing nozzles, could also lead to such erroneous images in theory. Furthermore, partial blocking is also possible, whereby the printing nozzles emit a reduced amount of ink and/or the ink jet deviates from their desired printing point at a defined angle, whereby the printing nozzles print askew in terms of the final effect.
In order to compensate for such missing nozzles, different solutions exist in the prior art. It is known, for example, to use redundant printing nozzles, so that, in the event of a failure of a single printing nozzle, a further printing nozzle covering the same location in the printed image can be replaced.
Since this redundancy leads to an increase in the cost of the printing press, another solution is provided: the adjacent printing nozzle of the missing nozzle, which is still printing properly, can cover off the white line caused by the missing nozzle by the increased ink application.
In a further embodiment, in the case of multicolor printing, the defective printing nozzle that determines a color is covered by a pre-calculated combination of the available printing colors of the other color-separated printing nozzles that print in the same position. In this way, although the color values in the region of the missing nozzles are also changed here, the purposefully calculated, deviating color values in the entire printed image are always significantly better than the uncontrolled white lines with respect to the perceptible aspect.
A completely further solution is also to adapt the print image in the prepress phase of the printing process in such a way that the color values to be printed are adapted in the print head at the location of the defective printing nozzle in such a way that the missing nozzle can thereby be compensated for, given the known position of the missing nozzle. Variations in the printed image with respect to the geometric position in the printed image may also help reduce the impact of missing nozzles.
However, in order to be able to carry out this compensation method, the missing nozzle must first be precisely located once. For this purpose, various solutions are known in the prior art. One of the most common schemes is: printing test patterns by means of which the defined print couple can be targeted accuratelySuch as (for example dots or lines) assigned to the printing nozzles. Such a known test pattern is for example a vertical line that can be printed by every tenth printing nozzle in a printing head. In this case, in a first horizontal row (Reihe), every first, eleventh, twenty-first, etc. printing nozzle prints a respective vertical line, and in a second horizontal row, every second, twelfth, twenty-second, etc. printing nozzle prints until a tenth, twenty, thirty-third line with a tenth printing nozzle. The number of rows to be printed here corresponds to the spacing between the individual printing nozzles printed in the test pattern. Other intervals (e.g., every fifth or every twenty print nozzles) may also be selected. The number of these rows then varies accordingly. The decisive parameter for selecting the spacing between the individual printing nozzles in the test pattern is the resolution of the camera, with which the nozzle test pattern is determined. In the current state of the art, it is still today: the digital camera used for evaluating the test pattern has a resolution which is smaller than the resolution achievable with the print head of the inkjet printer. Thus, it becomes meaningless to print the following test pattern: at the test pattern, all the printing nozzles are directly in one row. The printing nozzles can also achieve different drop sizes. If, for example, printing is done with the largest possible drop size, what may happen is: those image objects printed by each printing nozzle influence each other because the inks run, for example, towards each other (mitenander)
). Which makes a test pattern with one row impractical.
After printing the nozzle test pattern, the nozzle test pattern is measured by a digital camera, which may be integrated in an inkjet printer, for example, as a component of an image detection system. Alternatively, the nozzle test pattern is printed first and then inspected by an external camera. By means of a computer-supported evaluation of the nozzle test pattern with respect to missing image objects, the missing nozzles can then be detected precisely, since the spacing between the individual printing nozzles and thus between the printed image objects is known.
However, a problem in this solution is that if the printing nozzles at the outermost edges of the printing heads in each case fail, this cannot be recognized in a targeted manner in the detection by means of the printed test pattern and subsequent digital evaluation. The computer that analyzes the digital image identifies the rows of image objects that have been printed in the nozzle test pattern by the individual printing nozzles. However, what the computer cannot recognize is: the computer analyzes the rows of these vertical lines, for example in a first horizontal row of nozzle test patterns, wherein in case of a failure of the first printing nozzle the first line is not actually the first line of the nozzle test pattern but the second line. The reason for this is that the exact position of the first printing nozzle in the digital printing image is not known per se for the detection algorithm in the analysis processing computer. That is, a malfunction of the respective first or last print nozzle in the print head cannot be solved by known nozzle test patterns by means of standard methods for detecting malfunctioning print nozzles. If a second, third or other print nozzle located inside the print head fails, the detection algorithm will recognize that: the spacing between lines caused by the left and right sides of a failed print nozzle, respectively, would be expected to be greater than the known spacing between individual print nozzles.
In order to solve this problem, it is known from the prior art to use so-called "locator marks". In this case, certain positioning marks having known measurement dimensions and positions are added to the nozzle test pattern, so that the detection algorithm can always recognize during the evaluation of the digital image of the nozzle test pattern: at which location the horizontal line of vertical image objects of the nozzle test pattern starts or ends. However, such a positioning mark has the following disadvantages: the positioning marks may affect the structure of the nozzle test pattern, thereby impairing the analysis process performed for detecting missing nozzles.
Disclosure of Invention
The object of the present invention is therefore to provide a method for detecting defective printing nozzles by means of a printed and evaluated nozzle test pattern (dusentestmaster), which does not require positioning marks and which overcomes the disadvantages known from the prior art.
The solution of the proposed task is a method for detecting faulty printing nozzles in an inkjet printer by means of a computer, wherein for each color separation a nozzle test pattern is printed which comprises a certain number of horizontal rows of equally spaced lines printed vertically in a periodic manner, said lines being arranged one above the other (uneiner), wherein in each row of the nozzle test pattern only such printing nozzles in a periodic manner contribute to the realization of the nozzle test pattern: these printing nozzles correspond to a defined number of the horizontal rows, and wherein a printed nozzle test pattern is detected for the evaluation by means of an image sensor, digitized and transmitted to a computer for the evaluation, and characterized in that, in order to determine a faulty printing nozzle at the edge of the printing head, the start of the horizontal row of nozzle test patterns is checked in this way when the nozzle test patterns are evaluated by the computer: how much the lines are geometrically deviated at the beginning of the corresponding lower run (jeweils darultriegenden Reihe) of the nozzle test pattern, wherein the computer checks the geometrical deviations of the lines in such a way that: how large the horizontal spacing between the first line of one row of nozzle test patterns and the first line of the lower row of nozzle test patterns is. The method according to the invention is essential in that the computer (or detection algorithm) always checks, when analyzing the digital image of the nozzle test pattern: where the respective first lines of the descending of these vertical lines are located. The reason for this is that in the applied nozzle test pattern (comprising x different rows of lines printed by the printing nozzles at intervals x), the start of each row necessarily has a certain geometrical deviation. For example, if a first row includes a first, eleventh, twenty-first print nozzle, while a second row includes a corresponding twelfth, twenty-second print nozzle, and so on, then the beginning of the second row is shifted by the horizontal spacing between the first and second print nozzles. For the case in which the first printing nozzle fails at this time, for example, then the first row starts at the position of the eleventh printing nozzle, whereas the second row (in the case of a correctly functioning second printing nozzle) starts further to the left at a spacing relative to the nine printing nozzles. However, in the case where all printing nozzles are functioning properly, the spacing between the beginning of the first row and the beginning of the second row must be significantly smaller, namely: only the space between the first and second printing nozzles is spaced apart. Since the image sensor that captures the printed nozzle test pattern has a resolution that is smaller than the spacing made between two printing nozzles, the test cannot be performed for the desired spacing between the first and second printing nozzles. Instead, the test is performed for the true spacing between the second and eleventh printing nozzles that exists in the event of a failure of the first printing nozzle. For such an interval of nine printing nozzles, the resolution of the image sensor used is sufficiently large. If this excessive spacing of nine printing nozzles now occurs between the beginning of the first and second rows, the compensation algorithm can detect the failure of the first printing nozzle in a targeted manner. The method is likewise also applicable here to the second, third, fourth and fifth printing nozzles, respectively, etc., which represent the respective beginnings of the second, third, fourth, fifth, etc. lines. The decisive analytical processes here are: the distance between the start of a line and the start of the line respectively below the line is evaluated. If this spacing of nine printing nozzles is measured here, this indicates that the corresponding first printing nozzle of the row is defective. If the spacing is still larger (e.g. a spacing of nineteen print nozzles), then even the first and second print nozzles of the row fail. Since each vertical line can be assigned to a specific printing nozzle in the nozzle test pattern, one or more defective printing nozzles at the printing edge can thus be detected in a targeted manner.
Advantageous and further preferred developments of the method result from the description of the associated preferred embodiments and the associated drawings.
A preferred development of the method according to the invention consists in that the computer detects and evaluates the spacing of these first lines of the respective run-down of the nozzle test pattern until it is ensured that: none of the first lines of the respective lower rows of nozzle test patterns are located to the horizontal left of the respective inspected first lines of a row. In the special case of a failure of a respective plurality of directly following printing nozzles at the printing edge (for example the first and second printing nozzles), the position of the first line of the respective row further below the row must also be detected. Thus, for example, for the above-described case (failure of both the first and second printing nozzles), if only the beginning of the second line is of interest, a failure of the first printing nozzle cannot be detected by means of the method according to the invention. Since in this case, the second printing nozzle is also defective, the start of the second row (in this case, corresponding to the twelfth printing nozzle) is again displaced by only one nozzle spacing (i.e. to the eleventh printing nozzle which marks the start of the first row). That is, the detection algorithm must also take care of: where the beginning of the third row is. The detection algorithm first obtains here: the spacing between the start of the second row and the start of the third row is correspondingly nine nozzle positions, and correspondingly the spacing between the start of the first row and the start of the third row is eight nozzle positions. That is, with these recognitions, the detection algorithm also recognizes: both the first and second printing nozzles fail. That is, the detection algorithm must compare the start of a row with the start of a corresponding number of downlinks located below the row for such a long time until the detection algorithm finds the corresponding start of the downlinks that starts on the left side of the horizon. In this case, the detection algorithm can consider as: all rows up to such a row: the beginning of the row, further to the left in the horizontal, all have missing nozzles in their respective first printing nozzles. If the detection algorithm does not find the beginning of the descending such level to the left, the detection algorithm can consider: none of the printing nozzles 1 to 10 respectively located at the outermost edges of the printing of the nozzle test pattern failed. The exceptional cases here are: the first nine print nozzles all failed and the tenth functioned normally. In this case, the beginning of the tenth row is offset to the left by only one nozzle spacing from the first line of the first row, since the beginning of the first row is in this case the eleventh printing nozzle, while the beginning of the tenth row is the tenth printing nozzle. The spacing is then too small in the horizontal direction, so that it can be detected according to the invention. The first nine printing nozzles on the workpiece fail, which is, however, extremely unlikely. On the other hand, such a serious error becomes immediately apparent in the subsequent official printing. Naturally, the principle according to the invention is also applicable to all other nozzle test patterns which operate with a different number of rows than 10.
A further preferred development of the method according to the invention consists in that, in the event of a failure of all first printing nozzles at the edge of the print head, the computer detects therefrom: that is, the total spacing between the first line of the first row of nozzle test patterns and the last line of the last row of nozzle test patterns is less than the spacing between the first and last print nozzles of the printhead. For the extremely unlikely case that all the first printing nozzles (which print the respective first lines of the first row) fail, the detection algorithm can detect in this case by: that is, the detection algorithm compares the spacing between the first line of the first row and the last line of the last row to the known total spacing between the first print nozzle and the last print nozzle. If this spacing is correspondingly significantly smaller than the desired spacing between the first and last printing nozzles, it can be concluded therefrom that all first printing nozzles at the printing edge have failed. Furthermore, the special case mentioned is that all first printing nozzles at the printing edge fail (except for the last row of printing nozzles), which can no longer be detected directly due to the too small resolution of the image sensor, but can nevertheless be detected with the aid of the present solution.
A further preferred development of the method according to the invention consists in that, in order to determine defective printing nozzles at opposite edges of the printing head, the computer executes the same method at the end of a row in a point-symmetrical manner. The method according to the invention described so far can be carried out in a point-symmetrical manner for the printing nozzles at the opposite edges of the print head. The first x respectively outer printing nozzles can thus be checked for a failure for both edges of the nozzle test pattern.
A further preferred development of the method according to the invention consists in that, for carrying out the method by means of an Inline measurement (Inline-messengen), the image sensor is a digital camera installed in an inkjet printer. The method according to the invention is carried out in a computer-supported manner, for which it is extremely advantageous if the digital cameras for recording the image data of the nozzle test patterns are digital cameras installed in the inkjet printer, which respectively carry out inline measurements. This means that the nozzle test pattern is printed in the inkjet printer and then immediately inline measured by a digital camera installed in the inkjet printer.
A further preferred development of the method according to the invention consists in that, in addition to the method for detecting defective printing nozzles at the printing edge, a further method for detecting printing nozzles located further inwards is also carried out. Since only missing nozzles at the printing edge are detected by means of the method according to the invention, it is naturally also necessary to carry out the conventional method for detecting missing nozzles which are not located at the printing edge at the same time. For this, standard methods are sufficient, for example for the analysis of the horizontal spacing of the vertical lines in the nozzle test pattern.
A further preferred development of the method according to the invention consists in that the information about the detected faulty printing nozzles is forwarded by the computer to a compensation algorithm (kompensationsalerithmus) which compensates for the detected faulty printing nozzles by adapting the print image data or by actuating adjacent active printing nozzles. The defective printing nozzles at the printing edges detected by the method according to the invention are forwarded by the computer to a compensation algorithm, which then compensates the defective printing as well as possible by means of the compensation methods known from the prior artAnd (4) brushing the nozzle. This can be carried out, for example, by a prepress stage computer in the case of adaptation of the print image data in the prepress stage. In this case, information on the detected missing nozzles is transmitted from the computer to the prepress stage computer. In the case of compensation in the printing press by actuating the respectively adjacent active printing nozzles of the missing nozzle, it is conceivable to send the information directly to the control computer of the printing press. For the case where the control computer of the printing press is identical to the computer that executes the detection method, an internal care (INTERNE) is implemented
) To the compensation algorithm.
Drawings
The figures show:
FIG. 1: a schematic of a page inkjet printer;
FIG. 2: false images of white lines caused by missing nozzles;
FIG. 3: applied multi-line nozzle test pattern;
FIG. 4: a schematic of the beginning and end of such a nozzle test pattern;
FIG. 5: schematic flow of the method according to the invention.
Detailed Description
A preferred application area of the embodiment variant is an inkjet printer 7. An example of the basic structure of such a machine/inkjet printer 7 is shown in fig. 1, which comprises a feeder 1 to a receiver 3 for feeding a print substrate 2 to a printing/inkjet printing unit 4, in which printing unit/inkjet printing unit 4 the print substrate 2 is printed by a print/inkjet print head 5. The present invention relates to a sheet ink jet printer 7, which sheet ink jet printer 7 is controlled by a control computer 6. In operation of the printing/inkjet printing machine 7, a malfunction of individual printing nozzles in the plurality of printing heads/inkjet printing heads 5 in the printing/inkjet printing unit 4 may occur (as described above). The result is then a white line 13 in the printed image 12 (or a distorted color value in the case of multicolor printing). An example of such a white line 13 in the printed image 12 is shown in fig. 2.
Fig. 3 shows an example of a printed nozzle test pattern 16 for a determined print color. This pattern/digital nozzle test pattern 14 is printed for each printing color. Characterized by equally spaced vertical lines/printed nozzle test lines 15. At every ten nozzle printing 10 lines with vertical stripes (or printing nozzle test lines 15) have to be printed in order to print with all nozzles. In a first row, for example, first nozzles {1,11, 21. } print, in the next row, all second nozzles {2,12, 22. } print, and so on. Also the result of the faulty printing nozzles in the form of white lines 13 can easily be seen in fig. 3, because of the absence of printing nozzle test lines at these locations in the printed nozzle test pattern.
The method according to the invention is compatible with the structure of the nozzle test pattern/digital nozzle test pattern 14 and the printed nozzle test pattern 16. In fig. 5, the flow of the method is shown in a schematic overview. In a first step a digitally present nozzle test pattern/digital nozzle test pattern 14 is printed. Such a nozzle test pattern/digital nozzle test pattern 14 can be located here not only next to the printed image 12 to be produced originally on the print substrate 2, but also on its own (at the printed image 12 to be produced originally). The printed nozzle test pattern 16 is then recorded by a camera which is installed after the last printing unit/inkjet printing unit 4 of the inkjet printer 7 and detects the resulting printed image 12. The detected digital print image 10 with the nozzle test pattern/printed nozzle test pattern 16 is then forwarded to the computer 6 for analysis processing.
Fig. 4 shows a simplified example of a printed nozzle test pattern/printed nozzle test pattern 16 with only 20 vertical lines of printing nozzles, here showing nozzles 'a' at the left edge 9 of the printing nozzles in the printed left edge/nozzle test pattern to nozzles't' at the right edge 8 of the printing nozzles in the printed right edge/nozzle test pattern. If the nozzle 'a' at the left edge 9 of the printed nozzle in the printed left edge/nozzle test pattern fails, then the detection algorithm identifies the 'k' line and then also both 'b' and 'I' lines. The image resolution of the applied digital camera and thus of the digital image generated, which is analyzed and processed by the detection algorithm, is limited. Even so, the detection algorithm still recognizes: 'b' is arranged at the left side of the horizontal and below 'k', and 'I' is arranged below 'k'. Thus, the detection algorithm can infer: the printing nozzle 'a' is missing. In contrast, if it is recognized that the first line at the left edge of the image is located below the 'I' line, the printing nozzles 'a' and 'b' are missing, respectively. This process continues up to the 'I' line. If the detection algorithm does not find a line to the left of the horizontal, then the detection algorithm may consider: the printing nozzles 'a' up to 'j' respectively located at the printing outermost left edge of the nozzle test pattern/the printing nozzle left edge 9 in the nozzle test pattern are not failed.
If all the printing nozzles of a row at the printing edge fail (in fig. 4, correspondingly printing nozzles 'a' to 'j', 'k' to't'), the detection algorithm recognizes: the measured interval 'k' to't' is smaller than the desired known interval of the printing nozzles 'a' to't'. In this case, a fault message can be output, since so many nozzles cannot be compensated for.
This correlation also applies in a point-symmetric manner to the nozzle test pattern/printed right edge of the nozzle test pattern 16/line 'k' to't' of printing nozzles at the printing nozzle right edge 8 in the nozzle test pattern.
The detected missing nozzles/the sought missing nozzles 11 are forwarded by the detection algorithm to the control computer/computer 6 of the printer/inkjet printer 7, which control computer/computer 6 enables the sought faulty printing nozzle/the sought missing nozzle 11 to be compensated for as may be required. In the case of larger print heads/inkjet print heads 5 with more than 20 print nozzles, there are also internal print nozzles in the nozzle test pattern/digital nozzle test pattern 14 and the printed nozzle test pattern 16. In addition to the detection algorithm for the printing nozzles at the right printing nozzle edge 8 in the printing edge/nozzle test pattern and the left printing nozzle edge 9 in the nozzle test pattern, the image produced by the digital camera/the detected digital printing image 10 must also be tested for missing nozzles in a further detection algorithm for these internal printing nozzles. It is sufficient here to apply methods known from the prior art, which test for gaps or deviations in the printed nozzle test pattern/the printed nozzle test pattern 16.
List of reference numerals:
1 feeder
2 printing substrate
3 material collector
4 ink-jet printing mechanism
5 ink jet print head
6 computer
7 ink jet printer
Printing nozzle right edge in 8-nozzle test pattern
Left edge of print nozzle in 9-nozzle test pattern
10 detected digital printed image
11 missing nozzle
12 selected print image
13 white line
14 digital nozzle test pattern
15 printing nozzle test line
16 printed nozzle test pattern
Claims (7)
1. A method for detecting faulty printing nozzles in an inkjet printer (7) by means of a computer (6), wherein for each color separation a nozzle test pattern is printed, which nozzle test pattern comprises a certain number of horizontal lines of equally spaced lines printed vertically in a periodic manner, which lines are arranged one above the other, wherein in each horizontal line of nozzle test pattern there is respectively only a certain number of printing nozzles in a periodic manner corresponding to the horizontal line to contribute to the nozzle test pattern, and wherein for the analysis process the printed nozzle test pattern is detected by means of an image sensor, digitized and transmitted to the computer (6) for the analysis process, characterized in that, for the determination of faulty printing nozzles at the edge of the print head, while the nozzle test pattern is being analyzed by the computer (6), check the start of the horizontal line of the nozzle test pattern: how much the line has a geometric deviation at the beginning of the respective downward run of the nozzle test pattern, wherein the computer (6) checks the geometric deviation of the line: how large the horizontal spacing between the first line of a row of the nozzle test pattern and the first line of the corresponding lower row of the nozzle test pattern that is below the row is.
2. A method according to claim 1, characterized in that the computer (6) detects and analyses the spacing of the first lines of the respective downlinks of the nozzle test pattern until it is ensured that: none of the first lines of the respective lower rows of nozzle test patterns are located to the horizontal left of the respective inspected first lines of a row.
3. A method according to claim 2, characterized in that for the case that all first printing nozzles at the edge of the print head fail, the computer (6) detects that the total spacing between the first line of the first row of the nozzle test pattern and the last line of the last row of the nozzle test pattern is smaller than the spacing between the first printing nozzles and the last printing nozzles of the print head.
4. A method according to one of claims 1 to 3, characterized in that, in order to determine faulty printing nozzles at opposite edges of the print head, the computer (6) performs the same method in a point-symmetrical manner at the end of a row of said nozzle test patterns, respectively.
5. Method according to one of claims 1 to 3, characterized in that, for carrying out the method by means of inline measurement, the image sensor is a digital camera installed in an inkjet printer (7).
6. Method according to one of claims 1 to 3, characterized in that in addition to the method for detecting a faulty printing nozzle at the edge of the printing head, another method for detecting a further internally located printing nozzle is also performed.
7. Method according to one of claims 1 to 3, characterized in that the information about detected faulty printing nozzles is forwarded by the computer (6) to a compensation algorithm which compensates the detected faulty printing nozzles by adapting the print image data or by actuating adjacent, active printing nozzles.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102017211988.8 | 2017-07-13 | ||
| DE102017211988.8A DE102017211988A1 (en) | 2017-07-13 | 2017-07-13 | Detection of failed pressure nozzles at the pressure edge |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109249711A CN109249711A (en) | 2019-01-22 |
| CN109249711B true CN109249711B (en) | 2021-02-26 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810768954.5A Active CN109249711B (en) | 2017-07-13 | 2018-07-13 | Method of detecting malfunctioning printing nozzles at printing edge |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP3427957B1 (en) |
| CN (1) | CN109249711B (en) |
| DE (1) | DE102017211988A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111439035B (en) * | 2019-01-17 | 2022-03-18 | 海德堡印刷机械股份公司 | Improved printed nozzle test pattern |
| NL2023206B1 (en) * | 2019-05-27 | 2020-12-02 | Spgprints B V | Failing nozzle compensation and non-uniformity correction in inkjet printing |
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| DE60115345T2 (en) * | 2000-09-01 | 2006-07-27 | Canon K.K. | Method and apparatus for inkjet printing |
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| US20130100189A1 (en) * | 2011-10-20 | 2013-04-25 | Canon Kabushiki Kaisha | Printing apparatus and processing method thereof |
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| GB9823833D0 (en) * | 1998-10-31 | 1998-12-23 | Xaar Technology Ltd | Droplet ejection apparatus |
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| US6905186B2 (en) * | 2002-07-30 | 2005-06-14 | Fuji Photo Film Co., Ltd. | Image recording apparatus |
| JP2006240232A (en) * | 2005-03-07 | 2006-09-14 | Canon Inc | Ink jet recording apparatus |
| JP4618789B2 (en) * | 2005-03-24 | 2011-01-26 | キヤノン株式会社 | Inkjet recording apparatus and inkjet recording method |
| KR100717018B1 (en) * | 2005-08-05 | 2007-05-10 | 삼성전자주식회사 | Ink jet image forming apparatus, and method for detecting defect nozzle thereof |
| JP4881271B2 (en) * | 2007-09-27 | 2012-02-22 | 富士フイルム株式会社 | Test chart, measuring method thereof, test chart measuring apparatus and program |
| JP2009148930A (en) * | 2007-12-19 | 2009-07-09 | Canon Finetech Inc | Registration error detection method and inkjet image forming device |
| JP2011201051A (en) * | 2010-03-24 | 2011-10-13 | Fujifilm Corp | Fine pattern position detection method and apparatus, defective nozzle detection method and apparatus, and liquid delivering method and apparatus |
| JP5623192B2 (en) * | 2010-08-31 | 2014-11-12 | キヤノン株式会社 | Image processing apparatus and image processing method |
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| JP6408946B2 (en) * | 2015-03-25 | 2018-10-17 | 株式会社沖データ | Recording device |
| US9718269B2 (en) * | 2015-06-04 | 2017-08-01 | Electronics For Imaging, Inc. | Multi-waveform inkjet nozzle correction |
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2017
- 2017-07-13 DE DE102017211988.8A patent/DE102017211988A1/en not_active Withdrawn
-
2018
- 2018-05-17 EP EP18172810.6A patent/EP3427957B1/en active Active
- 2018-07-13 CN CN201810768954.5A patent/CN109249711B/en active Active
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| DE60115345T2 (en) * | 2000-09-01 | 2006-07-27 | Canon K.K. | Method and apparatus for inkjet printing |
| US20080036803A1 (en) * | 2006-08-14 | 2008-02-14 | Samsung Electronics Co., Ltd. | Array type inkjet printer and method for determining condition of nozzles thereof |
| US20130100189A1 (en) * | 2011-10-20 | 2013-04-25 | Canon Kabushiki Kaisha | Printing apparatus and processing method thereof |
| US20170066262A1 (en) * | 2015-09-03 | 2017-03-09 | Fujifilm Corporation | Inkjet recording apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| EP3427957B1 (en) | 2020-03-11 |
| CN109249711A (en) | 2019-01-22 |
| DE102017211988A1 (en) | 2019-01-17 |
| EP3427957A1 (en) | 2019-01-16 |
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