Browse Prior Art Database

Self-Timed Bar Code Reader

IP.com Disclosure Number: IPCOM000099587D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Chu, HL: AUTHOR [+3]

Abstract

This article describes a bar code (BC) reader that gene- rates time reference (TR) pulses physically concurrent with the BC which makes it independent of scan speed fluctuations.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 65% of the total text.

Self-Timed Bar Code Reader

       This article describes a bar code (BC) reader that gene-
rates time reference (TR) pulses physically concurrent with the BC
which makes it independent of scan speed fluctuations.

      A BC is scanned serially.  The zeros and ones of a BC can be
recognized by knowing scan speed and bar/space dimensions, provided
that scan speed is constant across the scan of the BC.  In the case
where scan speed is not constant, at least one of the conditons
listed below has to be satisfied for a reliable detection.
1.   Scan speed fluctuations have to have a repeatable algorithm
which can be used by intelligent processing for a reliable detection
by compensating for it.
2.   BC design has sufficient run length encoding to provide adequate
criteria for intelligent processing.

      In the case where scan speed is not constant and neither of 1
or 2 above are satisfied, a TR for each bit position in the BC must
be generated physically concurrent with the BC.  The scheme disclosed
herein is based on this concept.  The situations where this scheme
would apply are hand-scanned BC applications, such as product BC
readers and stepper motor driven wafer and substrate handlers.  Also,
this scheme would apply to magnetic tape readers with magnetic
sensors.

      The scheme is code independent and scan speed independent.  It
does not impose restrictions on the number of consecutive ones and
zeros.  Thus, a higher code density can be achi...