Method and apparatus for scanning masters

An apparatus for point-by-point and line-by-line, opto-electronic scanning of a master, comprising:

• a scanner drum for chucking a master to be scanned;
• an illumination unit for generating an illumination spot with a scan light on the master by imaging a light spot onto the master;
• a scanner objective;
• a scanner element for converting the scan light modulated with a content of the master and focused with the scanner objective into an image signal;
• and
• a feed support at which the illumination unit for generating the light spot, the scanner objective and the scanner element are arranged, the feed support executing a feed motion in a direction of the rotational axis of the scanner drum for scanning of the master;
• the illumination unit is designed such that a size of the illumination spot is variable via an imaging scale of the illumination spot;
• a measuring unit for measuring a luminance of the illumination spot;
• and
• a modifying structure connected to the measuring unit and to the illumination unit for modifying the imaging scale of the illumination spot dependent on the measured luminance.

A method for scanning of a master, comprising the steps of:

• mounting the master on a scanner drum;
• generating a light spot with a scan light for point-by-point illumination of the master and imaging it onto the master as an illumination spot;
• modulating the scan light with a content of the master, and converting it into an image signal in an opto-electronic scanner element;
• executing a feed motion with the illumination spot and scanner element in a direction of the rotational axis of the scanner drum for scanning of the master;
• measuring luminance of the illumination spot;
• and
• setting the illumination of the master dependent on the measured luminance by modifying an imaging scale with which the light spot is imaged onto the master as the illumination spot.