DE102023103467A1 - Method for adjusting a color in a printing press - Google Patents

Abstract

A method according to the invention for adjusting, preferably controlling, a color in a printing press, preferably an offset printing press, wherein the printing press (1) has at least one inking unit (2) with a number n, where n ≥ 2, adjustable ink zones (3) for the color (12), and the color is set to a color location, is characterized in that a target color location (21) is specified, that a corresponding number n of - with the color (12) on a printing material (10 ) printed - measuring fields (11) - for example by a camera - and a corresponding number n of coloring lines (22) are determined computationally, so that for each of the n coloring lines (22) there is a color location (23.) closest to the target color location (21). ) on the respective coloring line (22) is determined computationally, that an auxiliary color locus (25) - for example as an average, in particular a median - is determined computationally from the n closest color locations (23), and that the setting of the color (12 ) to the auxiliary color location (25). The invention advantageously makes it possible to optimize the setting and in particular the regulation of at least one color involved in printing.

Description

invention

The invention relates to a method for adjusting a color in a printing press with the features of the preamble of claim 1.

field of technology

The invention lies in the technical field of the graphic industry and there in particular in the area of automatic control of the printing ink(s) or their layer thicknesses on a printing material. The invention can be used in offset printing, i.e. in indirect planographic printing on printing materials such as paper, cardboard or plastic film.

State of the art

In the brochure “Expertise Color & Quality” from Heidelberger Druckmaschinen AG, point 5.3 describes spectrometric color control as it occurs in printing machines from Heidelberger Druckmaschinen AG.

The EP0228347A1 discloses a method for color application control, with spectral color measurement taking place. Using a measurement recording device, printed sheets produced by the printing press are photoelectrically measured in a series of test areas, for example in selected areas of the printed image or in the area of color measuring fields printed at the same time, and control data is determined from the measurement data obtained in this way, which corresponds to the color deviations of the printing inks involved in the printing correspond to the individual pressure zones and printing units and are fed to the control console as input variables. The control console generates control signals from the control data, which adjust the color guide elements of the printing press in such a way that the color deviations are minimal. For each test area (e.g. color measuring field), the spectral remissions are determined by spectral measurement and, if necessary, the color values of a selected color coordinate system are determined by conversion and compared with corresponding target remissions or target color values. The color guidance is then controlled based on the deviations of the spectral remissions or the color values from the target values (“color distances”).

The DE19749063A discloses a method for obtaining color measurement values.

The DE10223479A discloses a method for color control of a printing press based on device-independent color values.

The DE102006025898A discloses a method for calculating correction values in a color control or color control for a printing press.

Despite known measures, using these methods - even when adjusted - can lead to unacceptable differences in density and color.

Technical task

It is therefore an object of the present invention to create an improvement over the prior art, which in particular makes it possible to optimize the setting and in particular the regulation of at least one color involved in printing.

Inventive solution to the problem

This object is achieved according to the invention by a method according to claim 1.

Advantageous and therefore preferred developments of the invention emerge from the subclaims as well as from the description and the drawings.

A method according to the invention for adjusting a color in a printing press, wherein the printing press comprises at least one inking unit with a number n, where n > 2, of adjustable color zones for the color, and wherein the color is adjusted to a color locus, is characterized in that that a target color location is specified, that a corresponding number n of measuring fields - printed with the color on a printing material - are recorded and from this a corresponding number n of coloring lines are determined computationally, that for each of the n coloring lines there is a color location closest to the target color location on the respective coloring line it is determined computationally that an auxiliary color location is determined computationally from the n closest color locations, and that the color is set to the auxiliary color location.

Advantageous training and effects of the invention

The invention advantageously makes it possible to optimize the setting and in particular the regulation of at least one color involved in printing.

The invention advantageously serves to set, preferably regulate, a single color or individual color (e.g. C, M, Y or K) by detecting measuring fields for the individual color and deriving data for the setting from them. In other words: in multi-color printing (eg four-color printing: CMYK), each individual color used is individually recorded and adjusted according to the invention, preferably regulated.

Furthermore, the invention advantageously serves to computationally determine an optimal color location (nearest color locations) on a coloring line for the color zone for each color zone of each individual color and to computationally determine a common optimal color location (auxiliary color location) from these locations, on which ultimately is set, preferably regulated.

The procedure according to the invention offers the following advantage: if the target color location is far away from a coloring line, even a slight change in the coloring line can lead to a strong change in the optimal color location on the coloring line - preferably closest to the target color location. Calculating and using the auxiliary color location from several closest color locations solves this problem: Because the auxiliary color location is preferably closer to the n individual color lines (the n color zones of the individual color) than the target color location, the ultimately set color locations are also preferably regulated, n color locations advantageously close together.

Regarding the concept of the color line (also called “color train”): If you change the layer thickness of the color on the printing material, e.g. by changing the ink zone openings, the visual impression changes. If you imagine a color range from very little color to full saturation - e.g. in the CIE L*a*b* color space - for each adjustable or controllable color zone, a line is created that not only varies in brightness, but also in their position in the a and b planes. This line is called the coloring line. The individual coloring lines can be determined computationally in a known manner using a model by first calculating the spectra as a function of the layer thickness and then calculating the Lab values from the spectra. Further information can also be found in the Heidelberger Druckmaschinen AG brochure “Expertise Color & Quality”, in particular under point 5.3.6 “Measuring and regulating in printing”.

Further developments of the invention

Preferred further developments of the invention (in short: further developments) are described below.

A further development can be characterized by the fact that the closest color locations are determined computationally via their respective distance from the target color location, i.e. that on each coloring line the color location is determined as the closest color location which has the smallest distance to the target color location in a given color space.

A further development can be characterized in that when setting the color to the auxiliary color location, a further closest color location is determined for each color zone on the respective color line, which has the smallest distance to the auxiliary color location in the specified color space.

A further development can be characterized by the fact that the coloring lines are determined computationally and based on models. Further training can be characterized by the use of a color model.

A further development can be characterized by the fact that an average value is determined as the auxiliary color location from the n closest color locations. A further development can be characterized by the fact that weighting factors are used to determine the mean value. A further development can be characterized by the fact that at least one of the closest color locations is not taken into account when determining the mean value. Further training can be characterized by the fact that the mean is determined as a median.

A further development can be characterized by the fact that a measuring field is assigned to each color zone.

A further development can be characterized by the fact that the respective settings of the color zones remain unchanged while the measuring fields are being recorded.

A further development can be characterized by the fact that the measuring fields are recorded optically. A further development can be characterized by the fact that the measuring fields are recorded spectrally.

A further development can be characterized by the fact that the measuring fields only include the color, i.e. no other colors.

A further development can be characterized by the fact that the coloring lines correspond to a respective line in the lab room. Further training can be characterized by the fact that the lines in the lab space are curved. A further development can be characterized by the fact that the coloring lines correspond to a respective line in the ab plane in the lab space. A further development can be characterized in that the lines run at least between a respective first color location and a respective second color location, the first color location corresponding to a first color application amount of the color and the second color location corresponding to a different, ie higher or lower, second color application amount of the color .

A further development can be characterized by the fact that the color is set to the auxiliary color location as a control.

A further development can be characterized by the fact that the color is a printing ink. A further development can be characterized by the color corresponding to black, cyan, magenta, yellow, orange, green or violet or a special color different from these.

The features and combinations of features disclosed in the technical field, invention and further developments sections above as well as in the following exemplary embodiments section represent - in any combination with one another - further advantageous developments of the invention.

Alternatives

According to a first alternative to the invention mentioned, the object can also be solved by not calculating an auxiliary color location, preferably as an average of the closest color locations, but rather an average density of the closest color locations and then adjusting, preferably regulating, this density. For this purpose, in a first step, the optimal densities of the individual zones can be calculated in a known manner. These individual values can then be averaged and the average density value obtained can be regulated using a density control.

According to a second alternative to the invention mentioned, the object can also be solved by converting the density value into a color value using the actual spectrum of the color (preferably as the mean value of the individual spectra of the color zones) in a colorimetric control and then using it as the target color locus which is regulated.

Examples of embodiments of the invention and figures

• 1 eine Vorrichtung bei der Durchführung einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens;
• 2 ein Diagramm im Lab-Farbraum; und
• 3 Ablaufplan für eine bevorzugte Ausführungsform des erfindungsgemäßen Verfahrens

The figures show a preferred embodiment of the invention and the further developments:

• 1 a device for carrying out a preferred embodiment of the method according to the invention;
• 2 a diagram in the Lab color space; and
• 3 Flow chart for a preferred embodiment of the method according to the invention

1 shows an exemplary device when carrying out a preferred embodiment of the method according to the invention. The device comprises a printing press 1 with one or preferably several inking units 2, preferably an offset printing machine. The inking unit 2 shown in detail as an example comprises, arranged across its width, ie laterally, a number of n preferably identical ink zones 3. Each of these ink zones or their openings (e.g. the respective gap between adjustable knives and an inking roller) is adjustable, whereby the transferable The amount of color of a color or a printing ink can be adjusted in such a way that a desired print quality can be achieved. At least one drive 4 is provided for opening and closing the respective zones 3; each zone preferably comprises a separate and controllable drive, for example a stepper motor. The other inking units, which are not shown in detail, also include such ink zones and corresponding drives 4a. A single adjustable ink zone opening 5 (of a total of n openings) is shown as an example in a first ink zone 3.

1 also shows a printing material 10 processed or printed in the printing press, preferably a sheet of paper, cardboard or film, for a printed product. Lateral areas corresponding to zones 3 (separated from one another by imaginary and dashed lines) are shown on the printing material. In each such area there is at least one printed measuring field 11, which is printed with the color 12 of the inking unit 2 shown in detail. The n measuring fields can be arranged in a measuring strip that is essentially the width of the printing material. The measuring fields are preferably printed with only one color of an inking unit 2, for example only with cyan. Accordingly, additional measuring fields for other colors of the other inking units can be provided on the printing material, for example for magenta, yellow and black. The measuring fields are preferably recorded spectrally by a device 13 for recording, for example by one or more optical camera(s). Several such devices 13a can be provided, for example according to the number of inking units. For cost reasons, attempts are made to get by with as few cameras as possible or even to use only a single camera 13 in or after the printing press 1. All recorded data is transmitted unprocessed or already pre-processed to a computer 14, preferably a digital computer (“input”). This computer, in turn, is connected to the drive(s) (“output”). In this way, setting is, in particular, a control tion or regulation of the openings 5 of the color zones 3 possible. The computer can preferably be a machine computer of the printing press 1 or an additional computer.

2 shows a diagram. The well-known Lab color space 20 is shown with the axes a and b in the drawing plane (and the axis L perpendicular to it). A predetermined color location 21 can be seen. This is a target color location, for example for the color cyan. In addition, so-called coloring lines 22 can be seen; Only three lines are shown as examples; In fact, there are n lines, i.e. exactly as many as there are color zones. The coloring lines run at least between a first color location 22a and a second color location 22b and are usually curved between them. The coloring lines are preferably determined computationally using a predetermined color model. A color location 23 closest to the target color location 21 can be seen on each coloring line; In addition, the (color space) distances 24 of the closest color locations 23 to the target color location 21 can be seen; These distances 24 are the minimum distances between the color lines and the target color location 21. The closest color locations 23 are determined computationally according to the invention. According to the invention, an auxiliary color location 25 is determined computationally from the n closest color locations 23, for example by averaging. According to the invention, the setting, in particular the regulation, of the color is carried out on the auxiliary color location 25. In this case, another closest color location 26 is preferably determined computationally on each coloring line, the (color space) distance of which from the auxiliary color location 25 is minimal. For reasons of clarity, only one such location 26 is shown on a color line.

The computer 14 ultimately controls or regulates the drive 4 or the drives 4 in such a way that the other n closest color locations 26 on the n respective coloring lines 22 are reached in the n color zones of the color in question.

• Schritt 30: Bereitstellen eines Farbwerks 2 mit n einstellbaren Farbzonen 3 (veränderbaren Farbzonenöffnungen 5) und Bereitstellen einer Farbe 12.
• Schritt 31: Vorgeben eines Soll-Farborts 21 in einem vorgegebenen Farbraum 20, bevorzugt im Lab-Farbraum.
• Schritt 32: Drucken von n Messfeldern 11 mit der Farbe auf einen Bedruckstoff 10.
• Schritt 33: Erfassen der n Messfelder mit einer Einrichtung 13, bevorzugt einer Kamera.
• Schritt 34: Berechnen von n Färbungslinien 22, bevorzugt unter Anwendung eines vorgegebenen Farbmodells.
• Schritt 35: Berechnen von n zu dem Soll-Farbort nächstliegenden Farborten 23 auf den Färbungslinien.
• Schritt 36: Berechnen eines Hilfs-Farbortes 25 aus den n nächstliegenden Farborten, bevorzugt durch Mittwertbildung, insbesondere durch Medianbildung.
• Schritt 37: Einstellen, insbesondere Steuern oder Regeln, der Farbe auf den Hilfs-Farbort durch Verändern der Farbzonenöffnungen 5, bevorzugt unter Berechnung von weiteren zum Hilfs-Farbort nächstliegenden Farborten 26 auf den Färbungslinien.

3 shows a flowchart for a preferred embodiment of the method according to the invention with the following steps:

• Step 30: Providing an inking unit 2 with n adjustable ink zones 3 (changeable ink zone openings 5) and providing a color 12.
• Step 31: Specify a target color location 21 in a predetermined color space 20, preferably in the Lab color space.
• Step 32: Printing n measuring fields 11 with the color onto a printing material 10.
• Step 33: Acquiring the n measuring fields with a device 13, preferably a camera.
• Step 34: Calculating n coloring lines 22, preferably using a given color model.
• Step 35: Calculating n color locations 23 on the coloring lines that are closest to the target color location.
• Step 36: Calculating an auxiliary color locus 25 from the n closest color loci, preferably by averaging, in particular by averaging.
• Step 37: Adjusting, in particular controlling or regulating, the color to the auxiliary color location by changing the color zone openings 5, preferably by calculating further color locations 26 on the coloring lines that are closest to the auxiliary color location.

Reference symbol list

1

printing press

2

inking unit(s)

3

color zone(s)

4

Drive(s)

4a

other drives (or connections to them)

5

Color zone opening

10

printing material

11

measuring field(s)

12

Color

13

Device(s) for recording, e.g. camera

13a

other recording facilities (or connections to them)

14

calculator

20

Lab color space

21

specified color location / target color location

22

Coloring lines

22a

first color location

22b

second color location

23

nearest color locations

24

Distances to the target color location

25

Auxiliary color location

26

other closest color location

30

Providing an inking unit and providing a color

31

Specifying a target color location

32

Printing measuring fields

33

Capturing the measuring fields

34

Calculating coloring lines

35

Calculating nearest color locations

36

Calculating an auxiliary color locus

37

Setting the color to the auxiliary color location

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0228347 A1 [0004]
• DE 19749063 A [0005]
• DE 10223479 A [0006]
• DE 102006025898 A [0007]

Claims (10)

Method for setting a color in a printing press, wherein the printing press (1) comprises at least one inking unit (2) with a number n, where n ≥ 2, adjustable ink zones (3) for the color (12), and wherein the setting of the color on a color location, characterized in that a target color location (21) is specified, that a corresponding number n of measuring fields (11) printed with the color (12) on a printing material (10) is recorded and from this a corresponding number n of coloring lines (22) are determined computationally, that for each of the n coloring lines (22), a color location (23) closest to the target color location (21) on the respective coloring line (22) is determined computationally, that from the n closest color locations ( 23) an auxiliary color locus (25) is determined computationally, and the color (12) is set to the auxiliary color locus (25). Procedure according to Claim 1 , characterized in that the closest color locations (23) are determined computationally via their respective distance (24) to the target color location (21), that is, on each coloring line (21) the color location is determined as the closest color location (23) which is in a predetermined color space (20) has the shortest distance (24) to the target color location (21). Procedure according to Claim 2 , characterized in that when setting the color (12) to the auxiliary color location (25), a further closest color location (26) on the respective coloring line (22) is determined for each color zone (3), which is in the predetermined color space (20 ) has the shortest distance to the auxiliary color locus (25). Method according to one of the preceding claims, characterized in that the coloring lines (22) are determined computationally and based on models. Method according to one of the preceding claims, characterized in that an average value is determined as the auxiliary color location (25) from the n closest color locations (23). Procedure according to Claim 5 , characterized in that the mean is determined as a median. Method according to one of the preceding claims, characterized in that a measuring field (11) is assigned to each color zone (3). Method according to one of the preceding claims, characterized in that the measuring fields (11) are recorded spectrally. Method according to one of the preceding claims, characterized in that the measuring fields (11) only include the color (12), ie no other colors. Method according to one of the preceding claims, characterized in that the setting of the color (12) to the auxiliary color locus (25) takes place as a control.

Images