A circuit for digitizing an analog electric signal generated from a photoelectronic conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions includes a differentiator circuit for generating a first derivative signal representing a first derivative of the...http://www.google.de/patents/US5408081?utm_source=gb-gplus-sharePatent US5408081 - Digital circuit for a laser scanner using a first derivative signal and a comparison signal
