HandHeld Entertainment Quick Check PC600 - Manual (Page 36)

In 1982 the American National Standards Institute, (ANSI) X3A1 Technical
Subcommittee with the assistance of other ANSI and industry committees and
bar code authorities, began studying the issue of bar code print quality in other
symbologies for all types of printing methods. Through the years, bar codes had
been printed that met the existing standards, but would not scan. More often bar
codes printed out of specified standards did scan.
This combined group knew that the existing specifications for quality control of
bar codes were evaluating criteria based on the way the human eye "viewed" the
bar codes. This was not the way any bar code scanner would "see" the bar
code. A bar code scanner is an optical device and does not incorporate human
eye optical properties when "looking" at a bar code. The ANSI X3A1 group
evaluated what factors were important to the many different types of bar code
scanners/decoders for high first read rates and readability. After eight years of
extensive testing, the American National Standard X3.182-1990 Bar Code Print
Quality Guideline was published. This document outlines quality parameters
based on the optics of bar code scanning systems.
The ANSI X3.182 document has also served as the basis for verification
standards EN1635, developed by the Commission for European Normalisation
(CEN) and ISO 15416, developed by the International Standards Organization
(ISO).
The ANSI X3.182 and CEN 1635 documents have since been superseded by
adoption of ISO/IEC 15416:2000 Information technology -- Automatic
identification and data capture techniques -- Bar code print quality test
specification -- Linear symbols document. Since the development of the ISO/IEC
standard, most industries and major users of bar codes have adopted it as the
measure of bar code symbol quality.
The following sections describe the ISO/IEC method of verification and provide
the fundamental calculations and methods used to determine ISO/IEC quality
grades.
The aperture size and light source of the verification device both have significant
impact on the symbol’s grade. The verification aperture must be matched to the
symbol’s X dimension for accurate results. Similarly, the light source must be
appropriate to the method of printing or marking. Customer or industry
specifications typically indicate both an aperture and light source for verification.
See “Wand/Mouse Aperture Selection” table on page 21 for selection criteria.
In order to evaluate symbol parameters, the ISO/IEC method requires the
creation of a “Scan Reflectance Profile,” that is, a record of the reflectance values
(00% to 100%) measured on a single line across the entire width of the bar code.
These values are charted to create an analog representation of the bar code.
Each Scan Reflectance Profile is graded on a number of parameters, defined
below. Some parameters are Pass/Fail, others are graded A, B, C, D, or F.
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