EP3921172A1 - Procédé pour améliorer la qualité d'une image d'impression imprimée par jet d'encre - Google Patents

Procédé pour améliorer la qualité d'une image d'impression imprimée par jet d'encre

Info

Publication number
EP3921172A1
EP3921172A1 EP20703200.4A EP20703200A EP3921172A1 EP 3921172 A1 EP3921172 A1 EP 3921172A1 EP 20703200 A EP20703200 A EP 20703200A EP 3921172 A1 EP3921172 A1 EP 3921172A1
Authority
EP
European Patent Office
Prior art keywords
image
printed
image data
target
print
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20703200.4A
Other languages
German (de)
English (en)
Inventor
Thomas Boosmann
Jens VOELSCHOW
Sven Michael
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Windmoeller and Hoelscher KG
Original Assignee
Windmoeller and Hoelscher KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Windmoeller and Hoelscher KG filed Critical Windmoeller and Hoelscher KG
Publication of EP3921172A1 publication Critical patent/EP3921172A1/fr
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/401—Compensating positionally unequal response of the pick-up or reproducing head
    • H04N1/4015—Compensating positionally unequal response of the pick-up or reproducing head of the reproducing head
    • 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

Definitions

  • the invention relates to a method for increasing the quality of a print image of a digital printing machine that is printed on a web of material using the inkjet printing process, the digital printing machine comprising a print head with inkjet nozzles, an image acquisition unit for acquiring at least part of the print image and a control unit for controlling the print head .
  • the invention also relates to a digital printing machine for carrying out such a method.
  • the printing lengths usually vary between 10 meters and a few 1000 meters.
  • the following three influences have a negative effect on the quality of the printed image:
  • the object of the invention is therefore to keep the quality of the print image constant over the entire print length during the print job. This object is achieved by a method according to claim 1 and a digital printing press according to claim 9.
  • the invention makes it possible to identify and correct the above-mentioned changes in the print image in a simple manner.
  • the solution according to the invention is based on a method in which a test chart is printed at the beginning and / or during a print job, the first image data of which is recorded by the image acquisition unit and transmitted to the control unit, with an error correction of defective inkjet media as a function of the first image data.
  • Nozzles and / or and / or an alignment of the misaligned print head is carried out, in which, after the error correction and / or alignment has been completed, a target print image is printed, the target image data of which is captured by the image acquisition unit, transmitted to the control unit and stored there, in which, after printing the target print image, further actual print images are printed, the actual image data of which is captured by the image acquisition unit and compared with the target image data in the control unit and stored as target / actual comparison image data, whereby depending on the target image Actual comparison image data is an error correction of defective inkjet nozzle sen is carried out.
  • the error correction consists in switching off the defective inkjet nozzles.
  • neighboring inkjet nozzles take over the printing area of the respective switched off inkjet nozzle and print. This technique is also called "software-based inkjet nozzle overlap".
  • TWZ dot gain
  • a "normal viewer” was defined in various standards (in particular IS0 12647 and DIN 5033).
  • the normal color values are calculated from the spectrum of the received light, the spectral reflectance of the color and the standardized spectral value functions of the normal viewer. With the normal color values calculated in this way, the color measured with a spectral sensor can then be described exactly.
  • the CIELAB color model describes a three-dimensional color space in which corresponding color differences, which humans perceive to be the same size, are each measurably approximately the same distance apart. The most important thing about this color space is that
  • the coordinates of the CIELAB color space are often referred to as L * , a * and b * to distinguish them from the Hunter coordinates Lab (introduced in 1948 by Richard Sewall Hunter).
  • L * , a * and b * are omitted in this description, ie the CIELAB color space is referred to as Lab throughout.
  • the L value is always between 0 and 100. 0 stands for absolutely black and 100 for absolutely white. A normal viewer and the normal light type were defined to ensure a clear color perception.
  • the difference between two color locations is expressed by the color distance AE. The color difference is calculated using the following formula:
  • the values AL, Aa and Ab are the differences between the components of the two color loci.
  • the color distance formulas known from the literature with the designations AE cmc , AE 94 , AE m or AE m are also further developments to the above distance formula, for example the color distance formulas known from the literature with the designations AE cmc , AE 94 , AE m or AE m .
  • the color distance AE is therefore understood to mean any color distance that has been calculated according to a specific color distance formula, the person skilled in the art being able to select the appropriate color distance formula for the particular application.
  • test chart in the sense of the present description is a pattern printed separately from the printed image, the properties of which are optimized for carrying out certain tests.
  • a test chart can be used for ICC color calibration.
  • the test chart consists of a limited number of color fields, the composition of which is known from the process colors cyan, magenta, yellow and black.
  • Another example of using a test chart is the error correction of defective inkjet nozzles.
  • the test chart is designed in such a way that defective inkjet nozzles can be easily and clearly detected.
  • Another example of using a test chart is the detection of misaligned printheads. Check mark
  • a check mark (equivalent terms are "calibration field" or
  • test strips in the context of the present description is a pattern that is superimposed on the printed image. There are several options:
  • test mark is printed directly within the print image.
  • the test mark is usually not visible to the naked eye, while digital imaging systems recognize and
  • test marking Enable further processing. It is also possible, for example, for the test marking to consist of yellow micro dots which can be easily detected by a camera under UV light. Such yellow microdots are also used for color printer marking as a so-called machine identification code (MIC).
  • MIMIC machine identification code
  • test marking it is also possible for the test marking to be arranged between two printing sections in the printing direction.
  • the print sections can have a repetitive print content or also vary in the print content.
  • the target print image comprises a partial area of the subsequent actual print images.
  • an image area of the actual print image is automatically determined as the target print image.
  • the image area has the largest color gamut compared to other image areas of the actual printed image.
  • the image acquisition unit is a line camera. According to a further preferred embodiment it is provided that the image acquisition unit is a spectral sensor.
  • the comparison of the actual image data with the desired image data is based on the histogram data of the respective image data.
  • FIG. 1 a simplified block diagram of a digital printing machine with an inkjet print head for carrying out the method according to the invention.
  • Fig. 1 shows a simplified block diagram of a digital printing machine with an inkjet print head for performing the method according to the invention.
  • the core of the digital printing machine is the inkjet print head 101, which comprises several inkjet nozzles 106 with which individual ink droplets 102 are generated from the printing ink and transferred to the moving material web 103.
  • Control information is calculated by the control unit 104 and transmitted to the inkjet print head 101.
  • the control unit 104 obtains its
  • Print image that is stored in the control unit 104 in the form of digital target raster points and digital target color information.
  • the rastered print image was generated from a standard digital image format (e.g. RGB 24 bit, TIFF or PDF) as part of the so-called raster image process (abbr .: RIP).
  • An image capture unit 105 is arranged above the completely printed image, which can consist, for example, of a camera.
  • a test chart is printed, the first image data of which is captured by the image capture unit 105 and transmitted to the control unit 104.
  • Alignment of the misaligned print head 101 is carried out.
  • a target print image is then printed, the target image data of which is captured by the image capture unit 105, transmitted to the control unit and stored there.
  • Example 1 shows that a measured change in
  • Brightness L from 84 to 80 in this case only affects the chromatic colors cyan, magenta and yellow.
  • Corresponding correction in the pre-separated contone data by adapting the gradation curves in the cyan, magenta and yellow channels can be a
  • the lightness L has darkened from 37 to 30 (DE from 7), with the result that 6 colors in the 7c color space have changed.
  • a quality requirement of e.g. DE less than 2.5 it is sufficient to have a
  • a test chart is printed, the first image data of which is captured by the image capturing unit 105 and transmitted to the control unit 104, with an error correction of defective inkjet nozzles 106 and / or alignment of the misaligned inkjet nozzle 106 depending on the first image data Print head 101 is performed.
  • a target print image is then printed, the target image data of which is captured by the image acquisition unit 105 and sent to the
  • Control unit 104 are transmitted and stored there,
  • test mark printed a test mark together with the print image.
  • the test mark is present in the control unit 104 in digital form and forms the target image data.
  • its actual image data are captured by the image acquisition unit 105 and compared in the control unit 104 with the target image data and stored as target-actual comparison image data, misaligned print heads being detected as a function of the target-actual comparison image data.
  • the control unit corrects the misaligned print heads.

Abstract

L'invention concerne un procédé permettant d'améliorer la qualité d'une image d'impression d'une machine à imprimer numérique, ladite image étant imprimée en mode d'impression à jet d'encre sur une bande de matériau, la machine à imprimer numérique comprenant une tête d'impression dotée de buses pour jet d'encre, une unité de capture d'image destinée à saisir au moins une partie de l'image d'impression et une unité de commande destinée à commander la tête d'impression. L'invention vise à assurer une qualité constante de l'image d'impression pendant le travail d'impression, sur toute la durée d'impression. A cet effet, la solution selon l'invention repose sur un procédé selon lequel, au début et/ou pendant le travail d'impression, une mire d'essai est imprimée, dont de premières données d'image sont enregistrées par l'unité de capture d'image et transmises à l'unité de commande, procédé selon lequel, en fonction des premières données d'image, une correction d'erreur de buses pour jet d'encre défectueuses et/ou un alignement de la tête d'impression désajustée sont effectués, procédé selon lequel une fois la correction d'erreur et/ou l'alignement terminés, une image d'impression de consigne est imprimée, dont des données d'image de consigne sont enregistrées par l'unité de capture d'image, transmises à l'unité de commande et stockées dans celle-ci, procédé selon lequel après impression de l'image d'impression de consigne, d'autres images d'impression sont imprimées, dont des données d'image réelles sont enregistrées par l'unité de capture d'image et comparées dans l'unité de commande aux données d'image de consigne et mémorisées comme données d'image de comparaison de consigne-réelles, une correction d'erreur de buses pour jet d'encre étant effectuée, en fonction des données d'image de comparaison de consigne-réelles.
EP20703200.4A 2019-02-04 2020-01-31 Procédé pour améliorer la qualité d'une image d'impression imprimée par jet d'encre Pending EP3921172A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102019102696 2019-02-04
PCT/EP2020/052428 WO2020161014A1 (fr) 2019-02-04 2020-01-31 Procédé pour améliorer la qualité d'une image d'impression imprimée par jet d'encre

Publications (1)

Publication Number Publication Date
EP3921172A1 true EP3921172A1 (fr) 2021-12-15

Family

ID=69423317

Family Applications (1)

Application Number Title Priority Date Filing Date
EP20703200.4A Pending EP3921172A1 (fr) 2019-02-04 2020-01-31 Procédé pour améliorer la qualité d'une image d'impression imprimée par jet d'encre

Country Status (2)

Country Link
EP (1) EP3921172A1 (fr)
WO (1) WO2020161014A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4254925A1 (fr) * 2022-03-29 2023-10-04 Flooring Industries Limited, SARL Procédé de fabrication d'un substrat décoratif pour un panneau décoratif

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8531743B2 (en) * 2010-10-18 2013-09-10 Xerox Corporation System and method for detecting missing inkjets in an inkjet printer using image data of printed documents without a priori knowledge of the documents
JP5619041B2 (ja) * 2012-01-23 2014-11-05 富士フイルム株式会社 吐出不良検出方法及び装置、画像処理装置、プログラム、並びに印刷システム
DE102015207566B3 (de) * 2015-04-24 2016-04-14 Heidelberger Druckmaschinen Ag Verfahren zur Detektion ausgefallener Druckdüsen in Inkjet-Drucksystemen

Also Published As

Publication number Publication date
WO2020161014A1 (fr) 2020-08-13

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