EN ISO/IEC 15416:2001

SLOVENSKI STANDARD
01-oktober-2003
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Information technology - Automatic identification and data capture techniques - Bar code
print quality test specification - Linear symbols (ISO/IEC 15416:2000)
Informationstechnik - Verfahren der automatischen Identifikation und Datenerfassung -
Testspezifikationen für Strichcodedruckqualität, Lineare Symbole (ISO/IEC 15416:2000)
Technologies de l'information - Techniques d'identification automatique et de capture des
données - Spécifications pour essai de qualité d'impression des codes a barres -
Symboles linéaires (ISO/IEC 15416:2000)
Ta slovenski standard je istoveten z: EN ISO/IEC 15416:2001
ICS:
01.080.50 *UDILþQLVLPEROL]DXSRUDERY Graphical symbols for use on
WHKQLþQLKULVEDKY information technology and
LQIRUPDFLMVNLWHKQRORJLMLLQ telecommunications technical
WHOHNRPXQLNDFLMDKWHUY drawings and in relevant
XVWUH]QLWHKQLþQLSURL]YRGQL technical product
GRNXPHQWDFLML documentation
35.040 Nabori znakov in kodiranje Character sets and
informacij information coding
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO/IEC 15416
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2001
ICS 01.080.50; 35.040 Supersedes EN 1635:1997
English version
Information technology - Automatic identification and data
capture techniques - Bar code print quality test specification -
Linear symbols (ISO/IEC 15416:2000)
Technologies de l'information - Techniques d'identification Informationstechnik - Verfahren der automatischen
automatique et de capture des données - Spécifications Identifikation und Datenerfassung - Testspezifikationen für
pour essai de qualité d'impression des codes à barres - Strichcodedruckqualität, Lineare Symbole (ISO/IEC
Symboles linéaires (ISO/IEC 15416:2000) 15416:2000)
This European Standard was approved by CEN on 20 October 2001.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/IEC 15416:2001 E
worldwide for CEN national Members.

CORRECTED  2002-03-27
Foreword
The text of the International Standard from Technical Committee ISO/IEC/JTC 1 "Information
technology" of the International Organization for Standardization (ISO) has been taken over as a
European Standard by Technical Committee CEN/TC 225 "Bar coding", the secretariat of which
is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by June 2002, and conflicting national
standards shall be withdrawn at the latest by June 2002.
This document supersedes EN 1635:1997.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg,
Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of the International Standard ISO/IEC 15416:2000 has been approved by CEN as a
European Standard without any modifications.
INTERNATIONAL ISO/IEC
STANDARD 15416
First edition
2000-08-15
Information technology — Automatic
identification and data capture
techniques — Bar code print quality test
specification — Linear symbols
Technologies de l'information — Techniques d'identification automatique et
de capture des données — Spécifications pour essai de qualité
d'impression des codes à barres — Symboles linéaires
Reference number
ISO/IEC 15416:2000(E)
©
ISO/IEC 2000
ISO/IEC 15416:2000(E)
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ii © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
Contents Page
Foreword.vi
Introduction.vii
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Symbols and abbreviated terms .3
4.1 Abbreviations.3
4.2 Symbols .3
5 Measurement methodology.4
5.1 General requirements.4
5.2 Reference reflectivity measurements.5
5.2.1 Measurement wavelength(s).5
5.2.2 Measuring aperture.5
5.2.3 Optical geometry.6
5.2.4 Inspection band .7
5.2.5 Number of scans.7
5.3 Scan reflectance profile .7
5.4 Scan reflectance profile assessment parameters.8
5.4.1 Element determination .9
5.4.2 Edge determination .9
5.4.3 Decode .10
5.4.4 Symbol contrast (SC) .10
5.4.5 Minimum reflectance (R ).10
min
5.4.6 Edge contrast (EC).10
5.4.7 Modulation (MOD).10
5.4.8 Defects .10
5.4.9 Decodability.10
5.4.10 Quiet zone check .11
6 Symbol grading.12
6.1 Scan reflectance profile grading.12
6.1.1 Decode .12
6.1.2 Reflectance parameter grading.12
6.1.3 Decodability.13
6.2 Expression of symbol grade.13
7 Substrate characteristics.13
Annex A (normative) Decodability.14
A.1 Two-width symbologies .14
A.2 Edge to similar edge decodable symbologies ((n, k) symbologies) .14
Annex B (normative) Example of symbol quality grading .16
B.1 Individual scan reflectance profile grading .16
B.2 Overall symbol grade .17
Annex C (informative) Symbol grading flowchart.18
Annex D (informative) Substrate characteristics.19
D.1 Substrate opacity.19
D.2 Gloss .19
D.3 Over-laminate.19
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ISO/IEC 15416:2000(E)
D.4 Static reflectance measurements.19
D.4.1 Prediction of Symbol Contrast (SC).20
D.4.2 Prediction of Minimum Edge Contrast (EC ) and Modulation (MOD) .20
min
D.4.3 Acceptability of measured and derived values.22
Annex E (informative) Interpretation of the scan reflectance profile and profile grades.23
E.1 Significance of scan reflectance profiles.23
E.2 Interpretation of results.23
E.3 Matching grades to applications.24
E.4 Alphabetic grading .25
Annex F (informative) Guidance on selection of light wavelength .26
F.1 Light sources.26
F.2 Effect of variations in wavelength.27
Annex G (informative) Guidance on number of scans per symbol.28
Annex H (informative) Example of verification report .29
Annex I (informative) Comparison with traditional methodologies .30
I.1 Traditional methodologies.30
I.2 Correlation of Print Contrast Signal with symbol contrast measurements.30
I.3 Guidance on grading for applications also specifying PCS .31
Annex J (informative) Process control requirements.32
J.1 Process control for repetitive printing .32
J.2 Number of scans.32
J.3 Bar width deviation.33
J.3.1 Two-width symbologies .33
J.3.2 (n, k) symbologies .33
J.3.3 Average bar width gain/loss .33
Bibliography .34
iv © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission)
form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC
participate in the development of International Standards through technical committees established by the
respective organization to deal with particular fields of technical activity. ISO and IEC technical committees
collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in
liaison with ISO and IEC, also take part in the work.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
International Standard ISO/IEC 15416 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information
technology, Subcommittee SC 31, Automatic identification and data capture techniques.
Annexes A and B form a normative part of this International Standard. Annexes C to J are for information only.
© ISO/IEC 2000 – All rights reserved v

ISO/IEC 15416:2000(E)
Introduction
The technology of bar coding is based on the recognition of patterns encoded in bars and spaces of defined
dimensions according to rules defining the translation of characters into such patterns, known as the symbology
specification.
The bar code symbol must be produced in such a way as to be reliably decoded at the point of use, if it is to fulfil its
basic objective as a machine readable data carrier.
Manufacturers of bar code equipment and the producers and users of bar code symbols therefore require publicly
available standard test specifications for the objective assessment of the quality of bar code symbols, to which they
can refer when developing equipment and application standards or determining the quality of the symbols. Such
test specifications form the basis for the development of measuring equipment for process control and quality
assurance purposes during symbol production as well as afterwards.
The performance of measuring equipment is the subject of a separate International Standard, ISO/IEC 15426.
This International Standard is intended to be substantially equivalent in technical content to EN 1635 and ANSI
standards X3.182 - 1990 and ANSI/UCC5 on which it has been based. It should be read in conjunction with the
symbology specification applicable to the bar code symbol being tested, which provides symbology-specific detail
necessary for its application.
There are currently many methods of assessing bar code quality at different stages of symbol production. The
methodology provided in this specification is not intended as a replacement for any current process control
methods but gives essential additional quality information. This methodology provides a basis for grading the
quality of bar code symbols in relation to their expected performance when read and therefore gives symbol
producers and their trading partners a universally standardized means for communicating about the quality of bar
code symbols after they have been printed. It also provides symbol producers with information enabling them to
adjust their production process.
Alternative methods of quality assessment may be agreed between parties or as part of an application
specification.
vi © ISO/IEC 2000 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 15416:2000(E)
Information technology — Automatic identification and data
capture techniques — Bar code print quality test specification —
Linear symbols
1 Scope
This International Standard
� specifies the methodology for the measurement of specific attributes of bar code symbols;
� defines a method for evaluating these measurements and deriving an overall assessment of symbol quality;
� gives information on possible causes of deviation from optimum grades to assist users in taking appropriate
corrective action.
This International Standard applies to those symbologies for which a reference decode algorithm has been defined,
and which are intended to be read using linear scanning methods, but its methodology can be applied partially or
wholly to other symbologies.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 7724-2:1984, Paints and varnishes — Colorimetry — Part 2: Colour measurement.
EN 1556:1998, Bar coding — Terminology.
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in EN 1556 and the following apply.
3.1
bar
A dark element corresponding to a region of a scan reflectance profile below the global threshold.
3.2
bar reflectance
The lowest reflectance value of an individual bar element in the scan reflectance profile of that element.
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ISO/IEC 15416:2000(E)
3.3
decodability
The proportion of the available margin (between the ideal dimension of an element or combination of elements and
the relevant reference threshold) that has not been consumed by the element or combination of elements,
calculated for the element or combination of elements deviating most from its ideal dimension.
3.4
decode
Determination of the information encoded in a bar code symbol.
3.5
edge contrast
The difference between bar reflectance and space reflectance of two adjacent elements.
3.6
element reflectance non-uniformity
The reflectance difference between the highest peak and the lowest valley in the scan reflectance profile of an
individual element or quiet zone.
3.7
global threshold
The reflectance level midway between the maximum and minimum reflectance values in a scan reflectance profile
used for the initial identification of elements.
3.8
gloss
The propensity of a surface to reflect a proportion of incident light in a specular manner.
3.9
inspection band
The band (usually from 10 % to 90 % of the height of a bar code symbol) across which measurements are taken
(see Figure 2).
3.10
measuring aperture
A circular opening which governs the effective sample area of the symbol, and the diameter of which at 1:1
magnification is equal to that of the sample area.
3.11
modulation
The ratio of minimum edge contrast to symbol contrast.
3.12
(n, k) symbology
A class of bar code symbologies in which each symbol character is n modules in width and is composed of k bar
and space pairs.
3.13
peak
A point of higher reflectance in a scan reflectance profile with points of lower reflectance on either side.
3.14
sample area
The effective area of the symbol within the field of view of the measurement device.
3.15
scan reflectance profile
Plot of variations in reflectance with linear distance along a scan path.
2 © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
3.16
scan path
The line along which the centre of the sample area traverses the symbol, including quiet zones.
3.17
space
A light element corresponding to a region of a scan reflectance profile above the global threshold.
3.18
space reflectance
The highest reflectance value of an individual space element or quiet zone in the scan reflectance profile of that
element or quiet zone.
3.19
two-width symbology
A bar code symbology in which symbol characters consist only of narrow and wide elements the widths of which
are in a constant ratio to each other.
3.20
valley
A point of lower reflectance in a scan reflectance profile with points of higher reflectance on either side.
3.21
vertical redundancy
The property of a bar code symbol whereby there exist multiple possible scan paths as a result of the symbol being
significantly higher than the height of a single scan line.
4 Symbols and abbreviated terms
4.1 Abbreviations
EC: Edge contrast
EC : Minimum value of EC
min
ERN: Element reflectance non-uniformity
ERN : Maximum value of ERN
max
GT: Global threshold
MOD: Modulation
PCS: Print contrast signal
RT: Reference threshold
SC: Symbol contrast
SRD: Static reflectance difference
4.2 Symbols
A: Average achieved width of element or element combinations of a particular type
e: Width of widest narrow element
© ISO/IEC 2000 – All rights reserved 3

ISO/IEC 15416:2000(E)
E: Width of narrowest wide element
th
e:i edge to similar edge measurement, counting from leading edge of symbol character
i
K: Smallest absolute difference between a measurement and a reference threshold
k: number of element pairs in a symbol character in a (n, k) symbology
M: Width of element showing greatest deviation from A
m: Number of modules in a symbol character
N: Average achieved wide to narrow ratio
n: number of modules in a symbol character in a (n, k) symbology
R : Bar reflectance
b
R : Dark reflectance
D
R : Light reflectance
L
R : Space reflectance
s
R : Maximum reflectance
max
R : Minimum reflectance
min
RT : Reference threshold between measurements j and (j+1) modules wide
j
S: Total width of a character
V: Decodability value
V : Decodability value for a symbol character
C
X: Nominal narrow element dimension
Z: Average achieved narrow element dimension
5 Measurement methodology
5.1 General requirements
The measurement methodology defined in this standard is designed to maximize the consistency of both reflectivity
and bar and space width measurements of bar code symbols on various substrates. This methodology is also
intended to correlate with conditions encountered in bar code scanning hardware.
Measurements shall be made with a single light wavelength and a measurement aperture of a diameter defined by
the application specification or determined in accordance with 5.2.1 and 5.2.2.
Whenever possible, measurements shall be made on the bar code symbol in its final configuration, i.e. the
configuration in which it is intended to be scanned. If this is impossible, refer to annex D for the method to be used
for measuring reflectance for non-opaque substrates.
The sampling method should be based on a statistically valid sample size within the lot or batch being tested. A
minimum grade for acceptability shall be established prior to quality control inspection. In the absence of a
4 © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
sampling plan defined in formal quality assurance procedures or by bilateral agreement, a suitable plan may be
based on the recommendations in ISO 2859 or ISO 3951.
5.2 Reference reflectivity measurements
Equipment for assessing the quality of bar code symbols in accordance with this standard shall comprise a means
of measuring and analysing the variations in the diffuse reflectivity of a bar code symbol on its substrate along a
number of scan paths which shall traverse the full width of the symbol including both quiet zones. The basis of this
methodology is the measurement of diffuse reflectance from the symbol.
All measurements on a bar code symbol shall be made within the inspection band defined in accordance with 5.2.4.
The measured reflectance values shall be expressed in percentage terms either with reference to the reflectance of
a barium sulphate or magnesium oxide reference sample complying with the requirements of ISO 7724, which shall
be taken as 100 %, or by means of calibration and reference to recognised national standards laboratories for
samples illuminated at 45° with the diffusely reflected light being collected perpendicular to the surface.
5.2.1 Measurement wavelength(s)
The peak light wavelength used for measurements should be specified in the application specification to suit the
intended scanning environment. When the wavelength is not specified in the application specification,
measurements should be made using the wavelength of light that approximates most closely to the wavelength
expected to be used in the scanning process. Refer to annex F for guidance on the selection of the wavelength of
light.
5.2.2 Measuring aperture
The nominal diameter of the measuring aperture should be specified by the user application specification, to suit
the intended scanning environment. When the measuring aperture diameter is not specified in the application
specification, Table 1 should be used as a guide. In an application where a range of X dimensions will be
encountered, all measurements shall be made with the aperture appropriate to the smallest X dimension to be
encountered.
In the absence of a defined X dimension, the Z dimension shall be substituted.
The effective measuring aperture diameter may vary slightly from its nominal dimension due to manufacturing
tolerances and optical effects. Note that the measured width of some of the narrow elements may be smaller than
the measuring aperture diameter.
Table 1 — Guideline for diameter of measuring aperture
X Dimension Aperture diameter Reference
mm mm number
0,075 03
0,100�X<0,180
0,125 05
0,180�X<0,330
0,250 10
0,330�X<0,635
0,635 < X 0,500 20
NOTE The aperture reference number approximates to the measuring aperture
diameter in thousandths of an inch; this reference number is used for consistency
with the ANSI standard X3.182.
© ISO/IEC 2000 – All rights reserved 5

ISO/IEC 15416:2000(E)
5.2.3 Optical geometry
The reference optical geometry for reflectivity measurements shall consist of:
a) a source of incident illumination which is uniform across the sample area at 45° from a perpendicular to the
surface, and in a plane containing the illumination source that shall be both perpendicular to the surface and
parallel to the bars, and
b) a light collection device, the axis of which is perpendicular to the surface.
The light reflected from a circular sample area of the surface shall be collected within a cone, the angle at the
vertex of which is 15°, centred on the perpendicular to the surface, through a circular measuring aperture, the
diameter of which at 1:1 magnification shall be equivalent to that of the sample area.
NOTE Figure 1 illustrates the principle of the optical arrangement, but is not intended to represent an actual device.
This reference geometry is intended to minimise the effects of specular reflection and to maximise those of diffuse
reflection from the symbol. It is intended to provide a reference basis to assist the consistency of measurement. It
may not correspond with the optical geometry of individual scanning systems. Alternative optical geometries and
components may be used, provided that their performance can be correlated with that of the reference optical
arrangement defined in this section.
1 - Light sensing element
2 - Aperture at 1:1 magnification (measurement A = measurement B)
3 - Baffle
4- Sample
5 - Light source
Figure 1 — Reference optical arrangement
6 © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
5.2.4 Inspection band
The area within which all measurement scan paths shall lie shall be contained between two lines perpendicular to
the height of the bars of the symbol, as illustrated in Figure 2. The lower line shall be positioned at a distance
above the average lower edge of the bar pattern of the symbol, and the upper line at the same distance below the
average upper edge of the bar pattern of the symbol. This distance shall be equal to 10 % of the average bar
height, or the measuring aperture diameter, whichever is greater. The inspection band shall extend to the full width
of the symbol including quiet zones.
1 - Inspection band (normally 80 % of average bar height)
2 - 10 % of average bar height, or aperture diameter if greater, above inspection band
3 - 10 % of average bar height, or aperture diameter if greater, above average bar bottom edge
4 - Quiet zones
5 - Scanning lines
6 - Average bar bottom edge
Figure 2 — Inspection band
5.2.5 Number of scans
In order to provide for the effects of variations in symbol characteristics at different positions in the height of the
bars, a number of scans shall be performed across the full width of the symbol including both quiet zones with the
appropriate measuring aperture and a light source of defined nominal wavelength. These scans shall be
approximately equally spaced through the height of the inspection band. The minimum number of scans per symbol
should normally be ten, or the height of the inspection band divided by the measuring aperture diameter, whichever
is lower. Refer to annex G for guidance on the number of scans.
The overall quality grade of the symbol is determined by averaging the quality grades of the individual scans, in
accordance with clause 6.
5.3 Scan reflectance profile
Bar code symbol quality assessment shall be based on an analysis of the scan reflectance profiles. The scan
reflectance profile is a plot of reflectance against linear distance across the symbol. If scanning speed is not
constant, measuring devices plotting reflectance against time should make provision to compensate for the effects
© ISO/IEC 2000 – All rights reserved 7

ISO/IEC 15416:2000(E)
of acceleration or deceleration. If the plot is not a continuous analogue profile, the measurement intervals should
be sufficiently small to ensure that no significant detail is lost and that dimensional accuracy is adequate.
Figure 3 is a graphical representation of a scan reflectance profile. The vertical axis represents reflectance and the
horizontal axis linear position. The high-reflectance areas are spaces and the low-reflectance areas are bars. The
high-reflectance areas on the extreme left and right are the quiet zones. The important features of the scan
reflectance profile can be determined by manual graphical analysis or automatically by numerical analysis. For
example, the highest reflectance point on the scan reflectance profile in Figure 3 is approximately 82 % and the
lowest is approximately 10 %.
Figure 3 — Scan reflectance profile
5.4 Scan reflectance profile assessment parameters
The scan reflectance profile parameters described in 5.4.1 to 5.4.9 shall be assessed for compliance with this
standard. Figure 4 is the same scan reflectance profile as Figure 3 with certain features indicated.
8 © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
Figure 4 — Features of scan reflectance profile
5.4.1 Element determination
To locate the bars and spaces, a global threshold shall be established. The global threshold shall be the
reflectance value midway between the highest and lowest reflectance values measured in the scan reflectance
profile, or:
GT = (R +R )/2
max min
where: R represents the highest reflectance value
max
R represents the lowest reflectance value
min
Each region above the global threshold shall be regarded as a space and the highest reflectance value in the
region shall be designated the space reflectance, R . Similarly, the region below the global threshold shall be
s
regarded as a bar, and the lowest reflectance in the region shall be designated the bar reflectance, R .
b
5.4.2 Edge determination
An element edge shall be defined as being located at the point where the scan reflectance profile intersects the
mid-point between R and R of two adjacent regions, i.e. where the reflectance value is (R +R )/2. If more than
s b s b
one point satisfying this definition exists between adjoining elements, then the edge position and the element
widths will be ambiguous and the scan reflectance profile will fail to decode in accordance with 5.4.3. The quiet
zones and intercharacter gaps, if any, are considered to be spaces.
© ISO/IEC 2000 – All rights reserved 9

ISO/IEC 15416:2000(E)
5.4.3 Decode
The symbology reference decode algorithm shall be used to decode the symbol using the element edges
determined in 5.4.2. This algorithm may be found in the symbology specification.
5.4.4 Symbol contrast (SC)
Symbol contrast is the difference between the highest and lowest reflectance values in a scan reflectance profile.
SC = R -R
max min
5.4.5 Minimum reflectance (R )
min
Rmin is the lowest reflectance value in the scan reflectance profile. R shall not be higher than 0,5R .This
min max
parameter is intended to ensure that R shall not be too high, and to ensure an adequate margin between
min
background and bar reflectances, especially when the value of R is high.
max
5.4.6 Edge contrast (EC)
Edge contrast is the difference between the R and R of adjoining elements including quiet zones. The lowest
s b
value of edge contrast found in the scan reflectance profile is the minimum edge contrast, EC .
min
EC = R -R
s b
5.4.7 Modulation (MOD)
Modulation is the ratio of the minimum edge contrast to symbol contrast.
MOD = EC /SC
min
5.4.8 Defects
Defects are irregularities found within elements and quiet zones, and are measured in terms of element reflectance
non-uniformity.
Element reflectance non-uniformity within an individual element or quiet zone is the difference between the
reflectance of the highest peak and the reflectance of the lowest valley. When an element consists of a single peak
or valley, its reflectance non-uniformity is zero. The highest value of element reflectance non-uniformity found in the
scan reflectance profile is the maximum element reflectance non-uniformity. Defect measurement is expressed as
the ratio of the maximum element reflectance non-uniformity (ERN ) to symbol contrast.
max
Defects = ERN /SC
max
5.4.9 Decodability
The decodability of a bar code symbol is a measure of the accuracy of its production in relation to the appropriate
reference decode algorithm. Bar code scanning equipment can generally be expected to perform better on symbols
with higher levels of decodability than on those with lower decodability.
Rules governing the nominal dimensions for each bar code symbology are given in particular symbology
specifications. The reference decode algorithm allows reasonable margin for errors in the printing and reading
processes by defining one or more reference thresholds at which a decision is made as to the widths of elements
or other measurements.
The decodability of a scan reflectance profile is the fraction of available margin which has not been consumed by
the printing process and is thus available for the scanning process. When calculating the decodability value V for a
scan reflectance profile, regard shall be had to the measurements required by the reference decode algorithm in
10 © ISO/IEC 2000 – All rights reserved

ISO/IEC 15416:2000(E)
the relevant symbology specification. In the following paragraph the term "measurement" shall be taken to refer
either to a single element width, in symbologies which use these directly in the reference decode algorithm (e.g.
"Code 39"), or to the combined width of two or more adjacent elements, in symbologies using edge to similar edge
measurements for decoding (e.g. "Code 128").
The decodability value is calculated with reference to:
a) the average achieved width (referred to in the formula below as A) for measurements of a particular type (e.g.
narrow elements, or bar + space combinations nominally totalling 2 (or 3, or 4 .) modules) in the scan
reflectance profile;
b) the reference threshold applicable to measurements of the same type as A (referred to in the formula below as
RT);
c) the actual measurement showing the greatest deviation from A in the direction of the reference threshold,
(referred to in the formula below as M).
The general form of the formula for calculating V is as follows:
V = absolute value of ( (RT - M) / (RT - A) ).
where: (RT - M) represents the remaining margin not used by printing variation,
(RT - A) represents the total theoretical margin based on the ideal measurement of the element(s).
Figure 5 illustrates this principle. The shaded area represents the range within which measurements of the same
type as A (e.g. narrow elements) fall. All measurements are taken from 0.
Figure 5 — Principle of decodability measurement
More specific formulae applicable to either two-width symbologies or (n, k) symbologies are defined in annex A.
Reference should also be made to the symbology specification for the particular computation of decodability unique
to each symbology.
NOTE Depending on the symbology and its reference decode algorithm, the decodability measurement may or may not be
indicative of bar width gain or loss, but does not provide sufficient information on this for process control. Consequently, for
purposes of symbol production process control, measurement of bar width gain or loss should also be performed (see annex J),
although this measurement does not enter into the symbol grading process.
5.4.10 Quiet zone check
The average narrow element width, Z, shall be calculated and revised quiet zones determined based on this
dimension. R , ERN of the quiet zones, and R of the q
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