Photoelectric scanning of register marks on printed web - using logic circuit with counter receiving speed proportional pulses between detection of first and second marks of recognition character

摘要

Recognition characters on a printed web are used for photoelectric scanning of registration masks. Photocells for determining character width are arranged transversely to the direction of motion of the web. A logic circuit connected to the cells gives an output signal when a definite portion of the cells is influenced at only one of two successive instants which depend on web speed. A pulse generator whose output is proportional to speed is connected to a counter (11) via a gate (10). Pulses only reach the counter after a first mark of character has been detected by the photocells and before a second mark is detected. An output from the logic circuit can only appear when a given counter state has been reached.