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1. WO2000016240 - FAST EDGE DETECTION SYSTEM TOLERANT OF HIGH DEGREE OF INTERSYMBOL INTERFERENCE

Publication Number WO/2000/016240
Publication Date 23.03.2000
International Application No. PCT/US1999/021121
International Filing Date 13.09.1999
Chapter 2 Demand Filed 31.03.2000
IPC
G06K 7/10 2006.01
GPHYSICS
06COMPUTING; CALCULATING OR COUNTING
KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
7Methods or arrangements for sensing record carriers
10by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
G06K 7/14 2006.01
GPHYSICS
06COMPUTING; CALCULATING OR COUNTING
KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
7Methods or arrangements for sensing record carriers
10by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
14using light without selection of wavelength, e.g. sensing reflected white light
G06T 5/00 2006.01
GPHYSICS
06COMPUTING; CALCULATING OR COUNTING
TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
5Image enhancement or restoration
CPC
G06K 7/10851
GPHYSICS
06COMPUTING; CALCULATING; COUNTING
KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
7Methods or arrangements for sensing record carriers, ; e.g. for reading patterns
10by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
10544by scanning of the records by radiation in the optical part of the electromagnetic spectrum
10821further details of bar or optical code scanning devices
10851Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device
G06K 7/14
GPHYSICS
06COMPUTING; CALCULATING; COUNTING
KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
7Methods or arrangements for sensing record carriers, ; e.g. for reading patterns
10by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
14using light without selection of wavelength, e.g. sensing reflected white light
G06K 7/1452
GPHYSICS
06COMPUTING; CALCULATING; COUNTING
KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
7Methods or arrangements for sensing record carriers, ; e.g. for reading patterns
10by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
14using light without selection of wavelength, e.g. sensing reflected white light
1404Methods for optical code recognition
1439including a method step for retrieval of the optical code
1452detecting bar code edges
Applicants
  • PSC SCANNING, INC. [US]/[US]
Inventors
  • COLEMAN, Edward, P.
  • COLLEY, James, E.
  • O'DONNEL, Patrick, M.
Agents
  • VANDERLAAN, Christopher, A.
Priority Data
60/100,26814.09.1998US
NOT FURNISHED13.09.1999US
Publication Language English (EN)
Filing Language English (EN)
Designated States
Title
(EN) FAST EDGE DETECTION SYSTEM TOLERANT OF HIGH DEGREE OF INTERSYMBOL INTERFERENCE
(FR) SYSTEME DE DETECTION RAPIDE DES CONTOURS POUVANT FONCTIONNER A DES TAUX ELEVES DE BROUILLAGE INTER-SYMBOLES
Abstract
(EN)
A system (fig. 1 and fig. 5) 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 (fig. 2). The offset is determined by a fast adaptive peak detector provided by attenuating an 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).
(FR)
L'invention concerne un système (figure 1 et 5) et un procédé permettant d'améliorer la précision de la détection de contours dans des conditions de brouillage inter-symboles (ISI) élevé. Le premier signal dérivé amplifié et filtré est décalé dans les deux directions de manière égale afin de générer des décalages positifs et négatifs qui servent d'entrées respectivement à des détecteurs de crête négatifs et positifs (figure 2). Le décalage est déterminé au moyen d'un détecteur de crête adaptatif rapide obtenu par atténuation et couplage en courant alternatif ce premier signal dérivé à l'alimentation positive afin de faire fonctionner un détecteur de crête, avec un temps d'attaque bref, de sorte que sa sortie est presque réglée sur la première crête du premier signal dérivé. En revanche, ce détecteur de crête présente un temps de descente suffisamment long pour maintenir le seuil à un niveau à peu près constant dans l'étiquette. Les crêtes sont qualifiées si la crête en question diffère en amplitude de la crête précédemment qualifiée par la quantité décalée. Par conséquent, les crêtes sont qualifiées si leur profondeur de modulation dépasse un seuil, quel que soit le niveau absolu des crêtes (cette technique de qualification est appelée sélection par porte de la profondeur de modulation).
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