Heidelberger Druckmaschinen Ag

Ludo Kerz

Martin Schmitt-Lewen

Michael Kaiser

Wolfram Kolbe

Heinrich Wadle

A method for the digital screening of a halftone image by using a first screen having an arbitrary desired screen width and an arbitrary desired screen angle. For the method, the threshold value matrix of a second screen with a different screen angle and width is read out and compared with the color values of a halftone image presented. In order also to approximate screens having a particular irrational tangent and to avoid unpleasant sudden exposed device pixels in clear regions, it is proposed to provide at least one second threshold value matrix having XYaddresses, the XYaddresses of the second threshold value matrix are displaced by a factor 1/B in relation to the XYaddresses of the first threshold value matrix, and to read out the second threshold value matrix as soon as an error D between the first and the second screen exceeds a predefined limiting value.

Method for the digital screening of halftone images

A method for producing a pseudo-stochastic master surface for producing a cover or jacket of a cylinder for contacting printing material, includes providing the master surface with a pseudo-stochastic distribution of microsurfaces. The master surface is produced on the basis of a digital master in a jacket preliminary stage and serves for a preferably galvanic production of a microstructured cover, in which structure elevations correlate with the microsurfaces. The pseudo-stochastic distribution helps to avoid disruptive discernible effects, for example the moir&#xe9; effect and helps to construct the microstructuring in a targeted manner. A master surface, a method for producing a cylinder cover, a cylinder cover, a machine for processing printing material, a method for producing printed products and a method for microstamping printed products, are also provided.

Method for producing a pseudo-stochastic master surface, master surface, method for producing a cylinder cover, cylinder cover, machine processing printing material, method for producing printed products and method for microstamping printing products

A register control mark for the detection of positional deviations between at least two color separations printed over one another on a printing material in multicolor printing. The control mark has a pattern with parallel lines of a first color separation and, printed in parallel over the pattern, at least two parallel lines of a second color separation.

Compact register mark

A method of preparing a print control strip including at least two process control elements and being adapted to at least a width of at least one used area of at least one original image, includes determining borders of the at least one used area. A state is assigned to every process control element in dependence on if the process control element is located substantially inside the borders. A print control strip is created by using only process control elements that have been assigned a state as being inside the borders.

Print control strip and method of preparing the same

A method for digital imaging of a printing form () through application of energy is described, in which a burn-off area () is detachably fixed by supporting points (), supporting points () being left in place on the printing form () through non-imaging of image spots () and in which the burn-off from the burn-off area () is detached from the printing form () in a cleaning step. A supporting point () at a reference point is left in place precisely if the number of image spots () to be imaged in a surrounding area () of the reference point () exceeds a limit value and a boundary area () in the surrounding area () around the reference point () contains only image spots () to be imaged. The method may be used in a system for digital imaging of printing forms () having an energy source (), a cleaning unit (), a control unit (), and an image processing unit () with a computing unit (), in particular with a raster image processor (RIP) () in a printing unit of a printing press.

Method and system for digital imaging of printing forms

A method for performing a digital multistage screening of a continuous-tone image with a screen having any desired screen resolution and any desired screen angle, in which the screening is carried out by reading out threshold values and comparing the threshold values read out with the color values of the continuous-tone image. Threshold value matrices are used in which the threshold values represent one or more screen dots of a given screen, with which the desired screen resolution and the desired angle are approximated. While the threshold values are being read out, an error between the coordinates of the desired screen and of the given screen is determined, and the error is compensated for by correcting the read address for the threshold value matrix, as soon as the error exceeds a predefined limiting value. Instead of the threshold value matrices, printing-value matrices can also be used.

Multistage screening with screens of any desired screen resolutions and screen angles

In a method for digital rastering of a half-tone image with rasters having arbitrary screen widths and screen angles, the rastering occurs by reading out a threshold matrix and comparing the thresholds that are read out to the color values of the half-tone image. For that purpose, a threshold matrix is employed wherein the thresholds represent one or more raster dots of a raster arranged at an angle, the desired screen width and the desired angle being approximated therewith. During the readout of the thresholds, an error between the desired raster and the raster approximated by the threshold matrix is calculated, and the error is compensated by a correction of the readout address for the threshold matrix as soon as the error exceeds a predetermined limit value. Alternatively, stored bit patterns can be employed instead of the threshold matrix, these having been acquired by comparing the tonal values to be reproduced to a threshold matrix.

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Nieder-Olm, Germany

Ludo Kerz