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Browse Prior Art Database

Scanner Data Stream Non-label Eliminator

IP.com Disclosure Number: IPCOM000109025D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Cato, RT: AUTHOR [+2]

Abstract

The article describes a method for eliminating most of the non-label data from the serial data stream produced by a scanner head. This method differs from other candidate select hardware in that it eliminates data that is NOT a part of ANY known bar code signals. Thus, this method is NOT bar code dependent, unlike the candidate select hardware in use today. In addition, this method will not eliminate possible label candidates that have a reduced margin or quiet zone size.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Scanner Data Stream Non-label Eliminator

       The article describes a method for eliminating most of
the non-label data from the serial data stream produced by a scanner
head.  This method differs from other candidate select hardware in
that it eliminates data that is NOT a part of ANY known bar code
signals.  Thus, this method is NOT bar code dependent, unlike the
candidate select hardware in use today.  In addition, this method
will not eliminate possible label candidates that have a reduced
margin or quiet zone size.

      The data from a scanner head is high speed and contains mostly
non-useable data with real label data occasionally buried amongst it.
There is no known (practical) micro-processor available today that
can handle the worst-case data rate from high-performance scanner
heads.  Specialized hardware is designed to pre-filter the data
before it reaches the micro-processor.  Commonly known as candidate
select hardware, it reduces the amount of data that must be processed
by a micro-processor.  In the past, this hardware has been bar code
dependent; it is designed to "look" for data with the characteristics
of a single or extremely limited selection of symbol types.  This
makes the simultaneous reading of different bar's codes or
auto-discriminating between different bar code types impossible.  The
scanners available today that perform this function do "decode on the
fly", a different and much less flexible and less patchable
architecture.

      The solution to the problem described here concentrates on
eliminating data that is known bad, rather than specifically looking
for data that is very probably good.  Briefly stated, if any adjacent
elements (bars or spaces) within 16 video transitions have a ratio of
8 to 1 or 1 to 8, all the elements between those pairs are eliminated
from the data stream.

      All the bar codes known and used today allow adjacent elements
to have ratios of 4 to 1 or less.  The minimum practical bar code
lengths for all types of symbols have more than 16 elements.  The
only instance where ratios of greater than 4 are allowed is between
the first bar and the margin or quiet zone.

      The ratios between elements are tested digitally using the
counts that represent the element widths.  Two tests are done:  8 to
1 and 1 to 8.  In the 8 to 1 test, the last count is
shifted by three, mu...