Printing – Embossing or penetrating – Processes
Reexamination Certificate
2000-12-14
2003-02-25
Eickholt, Eugene H. (Department: 2854)
Printing
Embossing or penetrating
Processes
C101S483000, C358S003290, C358S406000, C382S203000
Reexamination Certificate
active
06523467
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the field of the electronic reproduction technology and relates to a method for measuring cups given the engraving of printing cylinders in an electronic engraving machine.
DE-C-25 087 34 discloses an electronic engraving machine for engraving printing cylinders. An engraving member having an engraver, which is controlled by an engraving control signal, as a cutting tool moves in an axial direction along a rotating printing cylinder. The engraver cuts a sequence of cups into the surface area, the cups being arranged in a printing raster. The engraving control signal is acquired by superimposition of a periodical raster signal with image signal values representing the hue values between “light” (white) and “dark” (black). While the raster signal effects an oscillating lifting motion of the engraver for engraving the cups arranged in the printing raster, the image signal values determine the geometric dimensions of the engraved cups corresponding to the hue values to be reproduced.
The engraving control signal must be calibrated, so that the cups engraved into the printing cylinder correspond to the hue values that are prescribed by the image signal values. For this purpose, a test engraving is carried out prior to the engraving, whereby cups are engraved for prescribed hue values, for example for the hue values “light” and “dark”. Subsequent to the test engraving, the geometric actual dimensions of the engraved cups, such as the transverse diagonals and the longitudinal diagonals, are measured. The geometric actual dimensions are compared to the geometric set dimensions of the cups, which represent the hue values prescribed for the test engraving. Adjustment values are acquired from the comparison, by means of which the engraving control signal can be calibrated such that the cups that are actually generated in the later engraving correspond to the cups required for an engraving with the correct hue value.
It is already known from WO-A-94/19900 to measure cups that are engraved during a test engraving in a video image picked up by a video camera.
WO-A-98/55302 discloses the determination of the geometric dimensions of an engraved cup in a video image on the basis of the cup contour with the aid of an electronic measuring line that can be displaced in the video image. For this purpose, a contour search is initially performed, whereby the image points situated on the cup contour are marked as contour points. Subsequently, the desired geometric dimensions are determined as a number of image points between relevant contour points.
In practical operation, the surface area of an engraved printing cylinder can often have defects such as scratches, which, during the contour search, are incorrectly interpreted in the video image as real contour points of a cup—as far as they are situated in the area of cup edges—so that faulty measurements result during the automatic cup measuring.
SUMMARY OF THE INVENTION
It is an object of the invention to improve a method for measuring cups during the engraving of printing cylinders in an electronic engraving machine, preferably for measuring cups generated during a test engraving, such that a secure and precise automatic determination of the geometric dimensions of engraved cups is assured despite present defects on the printing cylinder.
According to the method of the invention for measuring cups given engraving of printing forms in an electronic engraving machine, an engraving member engraves cups into a printing form. Geometric dimensions of the cups represent actual hue values. A A video image is produced of at least one engraved cup. A contour of the engraved cup is searched for in the video image. The cup contours found in the video image are smoothed. The geometric dimensions of the cups are determined on the basis of the smooth cup contour in order to avoid erroneous measurements.
The invention is subsequently explained in greater detail on the basis of FIGS.
1
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6
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Broer Olaf
Fangmeyer Dieter
Eickholt Eugene H.
Heidelberger Druckmaschinen Aktiengesellschaft
Schiff & Hardin & Waite
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