Second order differentiating signal processor for a bar code scanner and signal processing method for using bar code scanners

摘要

A second order differentiating signal processor for a bar code scanner, wherein the second order differentiating signal processor is adapted to detect bar and space transitions in edges representing an input signal (220), the second order differentiating signal processor having an entire even order filter polynomial having further a first filter (104) receiving the input signal (220) and providing a filtered signal; a first output channel (126) terminating with a first filter having a complex pole pair having a first cutoff frequency and a first attenuation ratio, the first output channel (126) receiving the filtered signal and the first derivative (226) of the input signal (220 ) generated; anda second output channel (128), parallel to the first output channel (126), terminating with a second filter having a complex pole pair having the first cutoff frequency and the first attenuation ratio, the second output channel (128) receiving the filtered signal and the second derivative (228) of the input signal (220); wherein the first filter (104) is a second order low pass filter and the second filter is a second order high pass filter; and wherein the cut-off frequency and the attenuation ratio of the low-pass filter and the high-pass filter are substantially equal.