GB1329337A - Apparatus for scanning and evaluating markings - Google Patents

Abstract

1329337 Sensing marks on packets G A O GES FUR AUTOMATION UND ORGANISATION mbH 19 April 1971 [30 April 1970] 22699/71 Heading G4M A device scanning two dimensional markings on a packet 2, consisting of a clock track 5 and a data track 6, relative movement taking place between the packet and scanning device has, for each track, a reading station containing two optical sensors 14, 15 or 16, 17 located beside each other in the direction of packet conveyance. The clock track contains equally spaced markings 11 and the data track has markings having a transition between clock track markings to indicate a "1" and an absence of a transition between clock track markings to indicate a "0". The sensors are spaced by a distance corresponding to the clock track markings and contain a lens and a mask arranged so that only the central portion 18 of the markings are examined. The outputs of the clock track markings are fed to a differential amplifier arranged to feed a Schmitt trigger when the two sensors have equal values (Fig. 4a). The trigger enables a gate passing the signal from a differential amplifier coupled to the data track sensors such that if one sensor detects a mark and the other detects the absence of a mark a "1" is indicated and if both sensors detect a mark or the absence of a mark a "0" is indicated (Fig. 6, not shown). The sensors are not affected by difference in positioning between the packet and sensors, by blurring of the markings or by decrease in contrast due to ageing.