Signal processing method

Details Signal processing method Signal processing method

2000-02-17

2004-04-06

Lee, Thomas D. (Department: 2624)

Facsimile and static presentation processing

Static presentation processing

Attribute control

C358S003300

Reexamination Certificate

active

06717701

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention is in the field of electronic reproduction technology and is directed to a method for signal processing in an electronic engraving machine for engraving printing forms, particularly printing cylinders, for rotogravure.
In an electronic engraving machine, an engraving element with an engraving stylus as a cutting tool moves along a rotating printing cylinder in an axial direction. The engraving stylus controlled by an engraving control signal cuts a sequence of depressions, called cups, arranged in a rotogravure raster into the generated surface of the printing cylinder. The engraving control signal is formed in a signal editing unit by superimposition of an engraving signal representing the gradations between “light” (white) and “dark” (black) with a periodic raster signal (vibration). Whereas the raster signal effects a vibrating lifting motion of the engraving stylus for producing the raster, the engraving signal, in conformity with the gradations to be reproduced, controls the geometric parameters of the engraved cups such as longitudinal diagonal, transverse diagonal and cut depth.
Occurring among other things in the signal processing stage are a calibration of the engraving signal values for “light” and “dark”, the superimposition of the corrected engraving signal with the raster signal for generating the engraving control signal, and the amplification of the engraving control signal.
U.S. Pat. No. 5,424,845 already discloses a method for signal processing in an electronic engraving machine, whereby the engraving signal value for “dark” is known and the engraving signal value for “light” is input, whereby an offset value is additionally calculated from the engraving signal values.
When the engraving signal value for “dark” is set in a traditional signal processing unit, then the engraving signal value for “light” simultaneously changes. As a result thereof, a faulty transverse diagonal of the engraved cups for “light” results, and the operator must disadvantageously manually correct the engraving signal value for “light”, so that the transverse diagonal or the engraved gradation remains constant given modification of the engraving signal value for “dark”.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to improve a method for signal processing in an electronic engraving machine for engraving printing forms, particularly printing cylinders, for rotogravure such that the engraving signal value for “light” is automatically kept constant when the engraving signal value for “dark” changes.
According to the present invention, a method is provided for signal processing in an electronic engraving machine for engraving printing forms for rotogravure. Engraving control signal values are formed from engraving data that represent predetermined gradations between “light” and “dark” and from a periodic raster signal for generating a raster. An engraving stylus of an engraving element controlled by the engraving control signal values engraves a sequence of cups arranged in the raster into the printing form, engraving depths thereof defining the actually engraved gradations. The engraving element implements a feed motion along the printing form for engraving of the cups. Before the engraving, the engraving control signals for “light” and “dark” are calibrated by a light setting value and a dark setting value such that the engraved gradations “light” and “dark” correspond to the predetermined gradations “light” and “dark”. For keeping the engraved gradation “light” constant when modifying the gradation “dark”, the difference value between the old dark setting value and a new dark setting value is formed before the engraving. A new light setting value is calculated from the engraving datum for “light”, from the old light setting value, and from the difference value. An automatic recalibration of the engraving control signal value for “light” is undertaken with the new light setting value.


REFERENCES:
patent: 3893166 (1975-07-01), Pugsley
patent: 5424845 (1995-06-01), Holowko et al.
patent: WO 98/55303 (1998-12-01), None
patent: WO 94/19900 (1994-01-01), None
patent: WO 96/26836 (1996-06-01), None
patent: WO 96/26837 (1996-06-01), None

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