Abstract: An optical bar code scanning device for high data density bar code reading. The device utilizes a two channel arrangement for directing light reflected from the bar code being read onto two photodetectors in predetermined proportionate amounts. With a two channel system, it is possible to detect a bar edge independent of print contrast variations, resolution modulation or change of illumination by comparing the optical signal of one channel with the optical signal of the other. The bar edge is represented by the crossover point of the normalized outputs of the two channels.