Controlling register in a printing press.

摘要

For register control when printing on a web, signals corresponding to a predetermined hidden pattern of low-amplitude density variations are superimposed on picture signals representing the image to be printed. After printing, light from elements of the printed image, with its hidden pattern, is detected by a register scanning head and the variations are correlated in a signal processor with the known variations of portions of the predetermined hidden pattern. In this way a position error signal is derived and can be used to correct the web position.