Circuit for detecting alignment-register marks produced by multicoloured printing - contains differentially connected photoelectric sensors, trigger circuit and evaluation device with interconnected counters

摘要

The circuit contains two or more differentially connected photoelectric mark sensors arranged along the transport direction of printed material and connected to a trigger circuit for their difference signal. An evaluation device receives the outputs of the trigger circuit and of a counter (9) with count pulse input driven by a fixed frequency generator (19). The counter data input (12) is driven by the data output (13) of a additional counter (14) whose count pulse input (20) is driven by the frequency generator (19). A 2:1 frequency divider (17) resettable by the charge pulse of the first counter is connected between its count pulse input (15) and the frequency generator. USE/ADVANTAGE - For determining the position of register markers wrt. a fixed reference value on printed products. Accurate measurement of the edge positions of multicolour markers is achieved at low cost and over the entire range of speeds of the printed material.