Level determination for optical character reader

摘要

Optical information on a card is read by an image sensor and then converted to a video signal represented by a digital signal of several bits through the use of an amplifier and an A - D converter. A reference level is determined by scanning a reference portion which is preferably provided along one edge of the card. The video signal is quantized by comparing with three sliced levels corresponding to 0.5, 0.75 and 0.85 times the reference level. The quantized information is applied to a recognition station.