Information technology -- Automatic identification and data capture techniques -- Effects of gloss and low substrate opacity on reading of bar code symbols

Users of bar code systems have experienced problems with poor read rates. These read rate problems can sometimes be attributed to spectral gloss from either the substrate or the image or both. In many bar code applications, the position and orientation of the scanner relative to the bar code symbol can be directly controlled by the operator. In these applications, the presentation of the bar code symbol to the reader will usually be manipulated by the operator to achieve optimal performance. However, in bar code applications using fixed position automated reading systems, the ability to control bar code symbol presentation to the reader and achieve optimised performance is diminished. Due to the very high volume of bar code marked items in today's supply chain, even a small reduction in read rate can represent significant logistics problems. Traditional gloss measurements are made at the angle that maximises specular reflection and do not provide results that can be used to predict performance at other angles. Moreover, many laser scanners use a retro-collective optical system that would correspond to a gloss meter using a zero degree angle of incidence, which is not commonly available. Present international bar code quality standards, such as ISO/IEC 15416, do not factor the impact of gloss from either the bar code image or substrate into quality grade ratings. Thus a Grade '4' label may be high gloss or low gloss. Low gloss labels and images tend to work well in all scanning systems, while high gloss labels and images may not. In the absence of industry specifications, users have no convenient reference to use when requesting suppliers to provide labels that will work well in their systems. ISO/IEC TR 19782:2006 provides a method for the measurement of gloss that will permit users to judge if the bar code symbol and substrate are suitably matched for the reading system used in their application. Low opacity of the substrate can degrade system performance because it may reduce the apparent contrast of the bar code symbol. ISO/IEC TR 19782:2006 therefore provides means for measuring the substrate opacity. The test method described in ISO/IEC TR 19782:2006 provides a means for the production of reproducible measurements. In specific applications, it may be necessary to correlate these measurements to practical performance. For example, a substrate backed by dark liquid may exhibit lower opacity than when measured dry. ISO/IEC TR 19782:2006 gives guidelines to deal with the effects of substrate gloss and/or low opacity on the performance of bar code symbols when scanned by reading and verification systems. It defines methods of measurement for gloss and opacity; it identifies conditions and values that present a risk of reading problems and provides recommendations to users on the specification of substrates and the set-up of scanning systems to minimize these problems. It also addresses the relationship between verification results and read performance when either or both of the factors are present. ISO/IEC TR 19782:2006 is intended for those who specify or implement labelling systems and those involved in the reading of bar code symbols on packages, components and other carriers of bar code symbols.

Technologies de l'information -- Techniques automatiques d'identification et de capture des données — Effets de la brillance et de la faible opacité du substrat sur la lecture des symboles de code à barres

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Status
Published
Publication Date
31-May-2006
Current Stage
6060 - International Standard published
Start Date
09-May-2006
Completion Date
01-Jun-2006
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TECHNICAL ISO/IEC
REPORT TR
19782
First edition
2006-06-01
Information technology — Automatic
identification and data capture
techniques — Effects of gloss and low
substrate opacity on reading of bar code
symbols
Technologies de l'information — Techniques d'identification
automatique et de capture des données — Effets de la brillance et de la
faible opacité du substrat sur la lecture des symboles de code à barres
Reference number
ISO/IEC TR 19782:2006(E)
ISO/IEC 2006
---------------------- Page: 1 ----------------------
ISO/IEC TR 19782:2006(E)
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ii © ISO/IEC 2006 – All rights reserved
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ISO/IEC TR 19782:2006(E)
Contents Page

1 Scope ..................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms and definitions........................................................................................................................... 1

4 Symbols and abbreviated terms ......................................................................................................... 2

5 Measurement procedures .................................................................................................................... 2

5.1 Effects of gloss and/or low opacity .................................................................................................... 2

5.2 Measurement of gloss.......................................................................................................................... 3

5.3 Measurement of opacity....................................................................................................................... 4

6 Test reports ........................................................................................................................................... 5

6.1 Test report for gloss............................................................................................................................. 5

6.2 Test report for opacity.......................................................................................................................... 5

7 Impact of gloss and opacity effects on verification .......................................................................... 5

Annex A (informative) Example of gloss measurement technique............................................................... 7

A.1 General description of set-up.............................................................................................................. 7

A.2 Test fixture............................................................................................................................................. 8

A.3 Example profiles – substrate and image............................................................................................ 8

A.4 Comparison of TAPPI T 425 Gloss measurements with gloss profile measurements................ 13

Annex B (informative) Reporting of gloss measurements........................................................................... 14

B.1 Recommendation for gloss profile measurement........................................................................... 14

B.2 Example of scan rate profile.............................................................................................................. 15

Annex C (informative) Opacity measurement................................................................................................ 17

C.1 Test Set-Up .......................................................................................................................................... 17

C.2 Measurement of Opacity for purposes of gloss determination ..................................................... 17

© ISO/IEC 2006 – All rights reserved iii
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ISO/IEC TR 19782:2006(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. In the field of information

technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of the joint technical committee is to prepare International Standards. 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.

In exceptional circumstances, the joint technical committee may propose the publication of a Technical Report

of one of the following types:

— type 1, when the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts;

— type 2, when the subject is still under technical development or where for any other reason there is the

future but not immediate possibility of an agreement on an International Standard;

— type 3, when the joint technical committee has collected data of a different kind from that which is

normally published as an International Standard (“state of the art”, for example).

Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether

they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to

be reviewed until the data they provide are considered to be no longer valid or useful.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.

ISO/IEC TR 19782, which is a Technical Report of type 3, was prepared by Joint Technical Committee

ISO/IEC JTC 1, Information technology, Subcommittee SC 31, Automatic identification and data capture

techniques.
iv © ISO/IEC 2006 – All rights reserved
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ISO/IEC TR 19782:2006(E)
Introduction

Users of bar code systems have experienced problems with poor read rates. These read rate problems can

sometimes be attributed to spectral gloss from either the substrate or the image or both.

In many bar code applications, the position and orientation of the scanner relative to the bar code symbol can

be directly controlled by the operator. In these applications, the presentation of the bar code symbol to the

reader will usually be manipulated by the operator to achieve optimal performance. However, in bar code

applications using fixed position automated reading systems, the ability to control bar code symbol

presentation to the reader and achieve optimised performance is diminished.

Due to the very high volume of bar code marked items in today's supply chain, even a small reduction in read

rate can represent significant logistics problems.

Traditional gloss measurements are made at the angle that maximises specular reflection and do not provide

results that can be used to predict performance at other angles. Moreover, many laser scanners use a retro-

collective optical system that would correspond to a gloss meter using a zero degree angle of incidence,

which is not commonly available.

Present international bar code quality standards, such as ISO/IEC 15416, do not factor the impact of gloss

from either the bar code image or substrate into quality grade ratings. Thus a Grade "4" label may be high

gloss or low gloss. Low gloss labels and images tend to work well in all scanning systems, while high gloss

labels and images may not. In the absence of industry specifications, users have no convenient reference to

use when requesting suppliers to provide labels that will work well in their systems. This Technical Report

provides a method for the measurement of gloss that will permit users to judge if the bar code symbol and

substrate are suitably matched for the reading system used in their application.

Low opacity of the substrate can degrade system performance because it may reduce the apparent contrast

of the bar code symbol. This Technical Report therefore provides means for measuring the substrate opacity.

The test method described in this Technical Report provides a means for the production of reproducible

measurements. In specific applications, it may be necessary to correlate these measurements to practical

performance. For example, a substrate backed by dark liquid may exhibit lower opacity than when measured

dry.
© ISO/IEC 2006 – All rights reserved v
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TECHNICAL REPORT ISO/IEC TR 19782:2006(E)
Information technology — Automatic identification and data
capture techniques — Effects of gloss and low substrate
opacity on reading of bar code symbols
1 Scope

This Technical Report gives guidelines to deal with the effects of substrate gloss and/or low opacity on the

performance of bar code symbols when scanned by reading and verification systems.

This Technical Report defines methods of measurement for gloss and opacity; it identifies conditions and

values that present a risk of reading problems and provides recommendations to users on the specification of

substrates and the set-up of scanning systems to minimize these problems. It also addresses the relationship

between verification results and read performance when either or both of the factors are present.

This document is intended for those who specify or implement labelling systems and those involved in the

reading of bar code symbols on packages, components and other carriers of bar code symbols.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO/IEC 19762-1, Information technology — Automatic identification and data capture (AIDC) techniques —

Harmonized vocabulary — Part 1: General terms relating to AIDC

ISO/IEC 19762-2, Information technology — Automatic identification and data capture (AIDC) techniques —

Harmonized vocabulary — Part 2: Optically readable media (ORM)

ISO/IEC 15415, Information technology — Automatic identification and data capture techniques — Bar code

print quality test specification — Two-dimensional symbols

ISO/IEC 15416, Information technology — Automatic identification and data capture techniques — Bar code

print quality test specification — Linear symbols

TAPPI T 425 om-01, Opacity of paper (15/d geometry, illuminant A/2°, 89 % reflectance backing and paper

backing)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 19762-1, ISO/IEC 19762-2 and

the following apply.
3.1
coaxial

pertaining to scanning systems in which the path of illumination from the light source to the symbol and the

path of collected light from the symbol are in the same axis
© ISO/IEC 2006 – All rights reserved 1
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ISO/IEC TR 19782:2006(E)
3.2
image

printed part of the symbol as opposed to the background (“printed” includes any method of creating a mark on

the substrate)
3.3
receiver

part of the optical system that collects the reflected light, focuses it onto the photodetector and outputs an

electrical signal proportional to the intensity of the light
4 Symbols and abbreviated terms
VM Volt Meter
mW Milliwatts
TT Thermal Transfer
TD Thermal Direct
λ wavelength
CTD Coated Thermal Direct
UNCTD Uncoated Thermal Direct
SUB Substrate
5 Measurement procedures
5.1 Effects of gloss and/or low opacity
5.1.1 Gloss

The performance of scanning equipment is highly dependent on the detection of adequate contrast between

the image and the substrate. Performance is degraded when an image or substrate, adversely affects the

Symbol Contrast due to its gloss. Note that Symbol Contrast can also be degraded by a high gloss low-opacity

substrate(see 5.1.2).

In coaxial reading systems, specular reflection can cause a problem when the incident angle is close to

normal with the result that the reflected light captured by the reader includes specular reflection. However, the

range of angles over which significant specular reflection occurs depends on characteristics of the material,

such as its gloss.

Materials with relatively high gloss will produce a higher amplitude of specular reflection over a narrower angle,

compared with matte materials. Matte materials tend to produce lower amplitude of specular reflection over a

wider angle.

In order for adequate contrast to be manifest, over reading angles that come close to and may even include

the normal, gloss may need to be controlled on a label for both the dark and light elements of the symbol.

The intensity of specular reflection as an indicator of the effect of gloss may be measured over a range of

angles and analysed as described in 5.2. There are several methods of obtaining a gloss profile. See Annex A

for examples.
2 © ISO/IEC 2006 – All rights reserved
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ISO/IEC TR 19782:2006(E)
5.1.2 Opacity

When a bar code symbol is printed on a substrate with low opacity, symbol contrast is reduced if the material

underlying the substrate is relatively darker than the substrate. Irregularities in the reflectance of the

underlying material can also affect either the defects or the modulation grade of the symbol when measured

according to ISO/IEC 15416 (or ISO/IEC 15415 for two-dimensional symbols).
5.2 Measurement of gloss
5.2.1 Three dimensional gloss profile

The 3-dimensional gloss profile is a plot of the amount of reflected light as a function of the angle of incidence

of illumination and the detection angle (when these are varied independently). Specular reflections occur

when the detection angle is equal to the angle of incidence within a range dependent on the material. For

most applications a simpler 2 dimensional plot will suffice (See section 5.2.2).
5.2.2 Two dimensional gloss profile

In many applications, the profile can be expressed as a 2-dimensional plot or family of 2-dimensional plots. A

2-dimensional plot can be used if either the angle of incidence of illumination or the detection angle are not

varied independently. For example, keeping the angle of incidence of illumination constant and varying the

angle of detection, a 2-dimensional plot shows how wide a range of detection angle would capture specular

reflection and its intensity.

As another example of a useful 2-dimensional plot, corresponding to a coaxial scanning system, the detection

angle could be maintained equal to the angle of incidence while both are varied simultaneously by tilting the

target surface (See example Figure A.2 produced using the set-up shown in Figure A.1).

5.2.3 Gloss profile measurement methods

The measurement of gloss profile is influenced by the angle over which the reflected light is collected. For

measuring gloss profile this angle should be fixed and small (≤ 6°) as illustrated in Figure 1. These

characteristics should be controlled for repeatable measurement.
Figure 1

The measurement of gloss depends on the spot size of the incident light and the angle of collection. Gloss

varies strongly with the angle of reflection of the incident light. On materials where the image becomes more

reflective at or near the specular angle than the background substrate, the contrast will be measured as a

negative value. For comparison in the selection of materials, it is preferable to have as small a range of

angles as possible, at which the Symbol Contrast is less than 20 %.

For comparison in the selection of materials, it is possible to use from the profile the ratio of reflectance

measured at 60° to reflectance measured at 90° for both the background substrate and image.

© ISO/IEC 2006 – All rights reserved 3
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ISO/IEC TR 19782:2006(E)
For the gloss profile, the reflectance of the substrate and of t
...

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