公开(公告)号：DE69941090D1

公开(公告)日：2009-08-20

申请号：DE69941090

申请日：1999-09-13

Applicant: DATALOGIC SCANNING INC

Inventor： COLEMAN EDWARD P ,  COLLEY JAMES E ,  O'DONNELL PATRICK M

IPC: G06K7/10 ,  G02B26/10 ,  G06K7/14 ,  G06K9/22 ,  G06K19/06 ,  G06T5/00

Abstract: A system and method for improving the accuracy of edge detection under high Inter-Symbol Interference, or ISI, conditions is disclosed. The amplified and filtered first derivative signal is offset by equal amounts in both directions to generate positive and negative offsets which serve as inputs to negative and positive peak detectors, respectively. The offset is determined by a fast adaptive peak detector provided by attenuating and AC-coupling the first derivative signal to the positive supply to drive a peak detector with a fairly short attack time, such that its output is nearly settled on the first peak of the first derivative signal, but having a decay time long enough to keep the threshold level approximately constant across the label. Peaks are qualified if the peak in question differs in amplitude from the previously qualified peak by the offset amount. Thus, peaks are qualified if their modulation depth exceeds a threshold, regardless of the absolute level of the peaks (such qualification strategy is referred to as modulation depth gating).