Digital circuit for a laser scanner using a first derivative signal and a comparison signal

摘要

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 analog signal. A comparison signal generating circuit generates a comparison signal and an output circuit, coupled to the differentiator circuit and to the signal generating circuit, compares the first derivative signal and the comparison signal to generate an output signal indicating a change in the intensity of the reflected light. An output controller, coupled to the output means, controls passage of the digital output signal.