Digitizing circuit for a laser scanner including positive peak detectors

摘要

A circuit for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges includes a differentiator for differentiating the analog signal to generate a first derivative signal of the analog signal. An inverter inverts the first derivative signal to generate an inverted signal and a peak detector detects amplitude peaks of the first derivative signal and the inverted signal and generates a first peak signal corresponding to the first derivative signal and a second peak signal corresponding to the inverted signal. An adder sums the first peak signal and the first derivative signal to generate a first sum signal. The adder also sums the second peak signal and the inverted signal to generate a second sum signal. A comparator compares the first sum signal with the inverted signal and compares the second sum signal with the first derivative signal to generate pulse signals indicative of the edges of the analog signal. A controller, in response to the pulse signals, generates a digital signal corresponding to the indicia being scanned.