A device and a method detect an edge of a recording material, in particular a
printing
plate, in an exposer for recording printing originals. An exposer has an exposure
drum for holding the printing plate, and an exposure head, which is moved axially
along the exposure drum and focuses exposure beams onto the printing plate. The
position of the edge of the printing plate is determined by a sensing device. To
this end, a sensing finger is pivoted into a groove in the surface of the exposure
drum and a signal is generated by a sensor when the sensing finger moves when it
touches the edge of the recording material. The sensor used is preferably a microswitch.
The axial position of the edge of the printing plate is determined by counting
the cycles of the feed drive that moves the sensing device.
