IEC 62715-5-3:2017

Flexible display devices - Part 5-3: Visual assessment of image quality and defects

IEC 62715-5-3:2017(E) provides the framework and procedures for performing the visual assessment of flexible display devices.
Visual assessment stipulated in this document is applicable to flexible display modules in the following states:
- initial states and ageing states under standard ambient conditions,
- mechanically or environmentally stressed conditions,
- states after mechanical endurance test(s), after environmental endurance test(s) and after a combination of mechanical and environmental endurance tests.
Visual assessment is performed by comparing a test sample to a limit sample or to a set of grade samples. This document provides the framework and procedures for visual assessments that use a limit sample or a set of grade samples. This document describes the framework and procedure that are followed while preparing limit samples and a set of grade samples. This document also describes visual assessment when limit samples and grade samples are not available for the same type of defect.
This document provides sets of test patterns that can be used in visual assessments.

General Information

• Status: Published
• Publication Date: 09-May-2017
• ICS: 31.120 - Electronic display devices
• Technical Committee: TC 110 - Electronic displays
• Drafting Committee: WG 8 - TC 110/WG 8
• Current Stage: PPUB - Publication issued
• Start Date: 26-May-2017
• Completion Date: 10-May-2017

Overview

IEC 62715-5-3:2017 - Flexible display devices - Part 5-3: Visual assessment of image quality and defects - defines a standardized framework and procedures for the visual assessment of flexible display devices. The standard covers assessments in multiple states: initial and ageing under standard ambient conditions, during or after mechanical and environmental stress, and after combined endurance tests. Visual inspection is performed by comparing a Device Under Test (DUT) to a limit sample or a set of grade samples, and the document also provides guidance when such comparison samples are not available. The standard includes recommended test patterns to support consistent visual evaluations.

Key topics and technical requirements

• Scope of assessment: Applicable to flexible display modules in initial, aged, stressed, and post-endurance-test conditions.
• Assessment methods: Comparative judgment using a limit sample or a set of grade samples; procedures for cases without comparison samples.
• Test setup and driving conditions: Requirements for how displays are driven and prepared for visual evaluation.
• Observers and procedures: Guidance on selecting and managing observers for repeatable visual results.
• Ambient and lighting conditions: Standard environmental conditions and lighting setups for consistent visual inspection.
• Viewing geometry: Defined viewing geometries (designed, standard usage, and rigorous) to replicate real-world and laboratory viewing angles.
• Test charts / test patterns: Full-screen, periodic, tone and colour gradation, cross-talk, electro-optical defect charts, static image resolution, and natural/synthetic images. (Includes example input signal levels for 8-bit systems.)
• Assessment after stress tests: Specific procedures for visual inspection during and after mechanical and environmental stresses.
• Judgement criteria: Procedures for ranking or judging defects, including use of Neutral Density (ND) filters and methods for mechanical defects.
• Reporting: Required and recommended reporting elements to ensure traceable, consistent results.

Applications and who should use it

IEC 62715-5-3 is intended for:

• Display manufacturers and module integrators for quality control and production acceptance
• R&D teams developing flexible, foldable or wearable displays to validate image quality
• Test laboratories and certification bodies performing visual image-quality assessments
• Failure analysis and QA engineers assessing defects such as mura, color non-uniformity, cross-talk and mechanical deformation

Use cases include end-of-line inspection, acceptance testing after environmental/mechanical endurance, supplier qualification, and creation of contract or product specifications.

Related standards

• IEC 62715 series (other parts covering flexible display device requirements)
• IEC 62341-6-2 and IEC 61747-20-3 (referenced guidance on visual assessment procedures for electronic displays)

Keywords: IEC 62715-5-3, flexible display devices, visual assessment, image quality, display defects, limit sample, grade samples, test patterns, viewing geometry, ambient lighting.

Standards Content (Sample)

IEC 62715-5-3 ®
Edition 1.0 2017-05
INTERNATIONAL
STANDARD
colour
inside
Flexible display devices –
Part 5-3: Visual assessment of image quality and defects
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC 62715-5-3 ®
Edition 1.0 2017-05
INTERNATIONAL
STANDARD
colour
inside
Flexible display devices –
Part 5-3: Visual assessment of image quality and defects

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120 ISBN 978-2-8322-4298-8

– 2 – IEC 62715-5-3:2017 © IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Procedures of visual assessment [2][3] . 9
4.1 General . 9
4.2 Setup of displays and driving conditions . 9
4.3 Observers for visual assessment [4][5]. 9
4.4 Ambient conditions for visual assessment . 9
4.4.1 Standard environmental conditions . 9
4.4.2 Standard lighting conditions . 9
4.5 Viewing geometry . 10
4.5.1 General . 10
4.5.2 Designed viewing geometry . 12
4.5.3 Standard usage viewing geometry . 12
4.5.4 Geometry for rigorous assessment . 12
5 Test charts (test signals) . 13
5.1 General . 13
5.2 Full-screen patterns . 13
5.3 Periodic patterns . 15
5.4 Tone and colour gradation patterns . 16
5.5 Test chart for cross-talk . 19
5.6 Test chart for electro-optical defects . 20
5.7 Test chart for static image resolution . 20
5.8 Natural and synthetic images . 21
6 Visual assessment during and after stress tests . 21
6.1 General . 21
6.2 Number of duplicate and reference DUTs . 21
6.3 Procedures of visual assessment after exposure to environmental stress . 22
6.4 Procedures of visual assessment after exposure to mechanical stress . 22
7 Criteria for judgments . 22
7.1 General concept . 22
7.2 Judgment using a limit sample . 22
7.3 Ranking using a set of grade samples . 22
7.4 Preparation of a limit sample or a set of grade samples . 23
7.4.1 General . 23
7.4.2 Procedures . 23
7.4.3 Affirmation of end-user true needs . 23
7.5 Judgments without a limit sample or a set of grade samples . 24
7.5.1 General . 24
7.5.2 Procedures . 24
7.6 Assessment using an ND (neutral density) filter . 24
7.6.1 General . 24
7.6.2 Procedures . 24
7.7 Assessment method for mechanical defects . 25

8 Reporting. 25
8.1 Requirements for reporting . 25
8.2 Recommendations for reporting . 25
Annex A (informative) Ranking of mura defect using ND filter . 26
Bibliography . 27

Figure 1 – Illustrative viewing geometries of flexible display devices . 11
Figure 2 – Example test patterns . 15
Figure 3 – Examples of periodic patterns . 16
Figure 4 – Example test charts for tone and colour reproduction . 18
Figure 5 – Examples of a test chart displayed on the screen of deformed DUTs . 19
Figure 6 – Cross-talk patterns window boxes on grey background diagonal from the
position at P . 20
Figure 7 – Monoscopic pattern for assessment of ultra high definition screen . 21

Table 1 – Example of the set of input signal levels for an 8-bit system . 13
Table 2 – Other input signal levels for an 8-bit system . 14
Table A.1 – Example of ranking of mura defect using an ND filter . 26

– 4 – IEC 62715-5-3:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FLEXIBLE DISPLAY DEVICES –
Part 5-3: Visual assessment of image quality and defects

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62715-5-3 has been prepared by IEC technical committee 110:
Electronic display devices.
The text of this International Standard is based on the following documents:
FDIS Report on voting
110/844/FDIS 110/867/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62715 series, published under the general title Flexible display
devices, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 62715-5-3:2017 © IEC 2017
INTRODUCTION
This part of IEC 62715 was developed in response to demands for the standardization of the
general rules and detailed procedures that are used in the visual assessment of flexible
display devices.
Visual assessment is an essential means for evaluating flexible display devices and is
intended to complement objective display measurements [1] . The advantages of visual
assessment are as follows:
a) It is speedy, e.g. defects are instantly recognized by a human observer.
b) It allows the evaluation of various device shapes and allows evaluation from various
directions and distances, which can lead to higher sensitivity for detecting defects.
c) It completely covers the area of even the largest display, allowing identification and
selection of regions of interest for objective measurements.
d) It is sensitive, e.g. for some defects, visual assessment is the most sensitive means of
detection.
e) It corresponds to the perception of humans.
f) It can detect unexpected changes or defects that can be overlooked by predetermined
measurements with equipment.
Visual assessment is a necessary first step for specifying types of measurements and the
regions of interest for measurements.
Evaluation results from visual assessment depend on the observer, region of interest for the
assessment, lighting and geometrical conditions of the assessment, criteria in making
judgments, and various other factors. Therefore, it is important to standardize the general
rules, including the terms, conditions, criteria and reporting of results from visual assessments.
Regarding the procedures for visual assessment of electronic display devices, the following
standards can be consulted: IEC 62341-6-2 [6] and IEC 61747-20-3 [7].
Visual assessment is usually performed by comparing a test sample with a limit sample or a
set of grade samples. This document stipulates the framework and procedures to be used in
the assessments; it also describes the preparation of a limit sample or a set of grade samples.
This document also applies when a limit sample or a set of grade samples are not available
for the same type of defect. Concerning defects of flexible display devices, many kinds of
defects can be observed. Even within the same category of defect, factors, such as the shape,
size, luminance, colour, gradation of the edge, width of the edge, solitary or repetitive,
position in the display area, can differ. Therefore, in most cases, it is practically impossible to
prepare the same type of limit sample or comparison samples for visual assessment.

___________
Numbers in square brackets refer to the Bibliography.

FLEXIBLE DISPLAY DEVICES –
Part 5-3: Visual assessment of image quality and defects

1 Scope
This part of IEC 62715 provides the framework and procedures for performing the visual
assessment of flexible display devices.
Visual assessment stipulated in this document is applicable to flexible display modules in the
following states:
– initial states and ageing states under standard ambient conditions,
– mechanically or environmentally stressed conditions,
– states after mechanical endurance test(s), after environmental endurance test(s) and after
a combination of mechanical and environmental endurance tests.
NOTE Visual assessment under the mechanical or environmental stress is usually difficult to do, but this
document can be applied when it is possible.
Visual assessment is performed by comparing a test sample to a limit sample or to a set of
grade samples. This document provides the framework and procedures for visual
assessments that use a limit sample or a set of grade samples. This document describes the
framework and procedure that are followed while preparing limit samples and a set of grade
samples. This document also describes visual assessment when limit samples and grade
samples are not available for the same type of defect.
This document provides sets of test patterns that can be used in visual assessments.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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.
IEC 61747-30-1, Liquid crystal display devices – Part 30-1: Measuring methods for liquid
crystal display modules – Transmissive type
IEC 62715-1-1, Flexible display devices – Part 1-1: Terminology and letter symbols
IEC 62715-6-1, Flexible display devices – Part 6-1: Mechanical stress test methods
IEC 62715-6-2 , Flexible display devices – Part 6-2: Environmental testing methods
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62715-1-1 and the
following apply.
___________
Under preparation. Stage at the time of publication: IEC/AFDIS 62715-6-2:2017.

– 8 – IEC 62715-5-3:2017 © IEC 2017
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE In cases where the terms and definitions are duplicated between this document and IEC 62715-1-1, the
definitions in this document take precedence.
3.1
visual assessment
process in which human visual observation is used to evaluate image quality by detecting and
classifying defects or by recognizing any adverse changes in image quality
3.2
grade sample
sample that represents a specific level of defect or deterioration in image quality
Note 1 to entry: Grade samples are usually prepared as grades 1 to 3 or grades 1 to 5, ranging from best to
poorest.
3.3
limit sample
sample that represents a specific type of defect or deterioration in image quality that
corresponds to an acceptance limit for a certain product
Note 1 to entry: Limit samples are applicable to defects that can be tolerated to a certain extent (e.g. uniformity
defects, point defects). They can be either one sample providing the maximum acceptable defect level or a set of
samples providing variations in defect level. The variations should represent a classification range for the strength
or number of the specific defect, thus providing a reference for an acceptable defect level.
3.4
ND filter
nutral density filter
optical filter that reduces the intensity of all wavelengths of light equally, giving no changes in
hue of color rendition
3.5
paired comparison method
psychophysical method involving a choice between two simultaneously presented stimuli that
exhibit greater or lesser image quality, or an attribute thereof, in accordance with a set of
instructions given to the observer
3.6
single stimulus method
psychophysical evaluation method inspecting only the objective sample without comparison,
in accordance with a set of instructions given to the observer
3.7
psychophysical method
method for examining something relating to the physical stimuli and sensory response
Note 1 to entry: ISO 20462-3:2012, 3.12 [3] defines the psychophysical method as an "experimental technique for
subjective evaluation of image quality or attributes thereof”.
3.8
reference stimulus
image provided to the observer for the purpose of anchoring or calibrating the perceptual
assessments of test stimuli
Note 1 to entry: The plural is reference stimuli.

[SOURCE: ISO 20462-3:2012, 3,15, modified – last part of definition deleted] [3]
3.9
observer
individual performing the subjective evaluation task in a psychophysical method
[SOURCE: ISO 20462-3:2012, 3.9] [3]
4 Procedures of visual assessment [2][3]
4.1 General
Procedures for assessment of image quality are described in Clause 4. The following items
are covered;
• image defects, such as subpixel defects, clustered defects, line defects, and mura,
• physical defects, such as scratch, abrasion, dent, and change in gross
• image quality, such as change in luminance, colour, or distortion.
Especially the changes of these items before and after the environmental and/or mechanical
stress tests are described.
NOTE Classification of defects and the naming and definitions of defects are described in IEC 62341-6-2 [6] and
IEC 61747-20-3 [7].
4.2 Setup of displays and driving conditions
Turn on the power supply and pattern generator and warm up for stabilization. Supply the
driving voltage and pattern to the display module as specified for each assessment. The
warm-up time of the device under test (DUT) and illumination shall be sufficiently long to
obtain a stable signal, which is necessary for visual assessment. It is recommended that when
the display is first turned on, it should be operated for at least 30 min.
4.3 Observers for visual assessment [4][5]
Observers shall be periodically trained for visual assessment by a qualified person using a
document of specified procedures and grade samples. Qualified persons are certified by each
organization based on their criteria. The criteria may be discussed by the customer(s) and the
provider(s). To ensure effectiveness, grade samples shall be maintained by a qualified person.
Observers should adapt to lighting conditions for a period of 10 min or more before beginning
an assessment session.
4.4 Ambient conditions for visual assessment
4.4.1 Standard environmental conditions
Visual assessment shall be carried out under standard environmental conditions: a
temperature of 23 °C ± 3 °C, a relative humidity of 45 % to 75 % and a pressure of 86 kPa to
106 kPa. When other environmental conditions are used, they shall be noted in the report.
4.4.2 Standard lighting conditions
4.4.2.1 General
Dark room conditions shall be used for the visual assessment of the image quality of
emissive-type displays in operational states. Controlled external lighting shall also be used for
the visual assessment of the emissive- and reflective-type displays and for physical damage
to both the display types.
– 10 – IEC 62715-5-3:2017 © IEC 2017
4.4.2.2 Dark room conditions for emissive-type display modules
The luminance contribution from background illumination reflected off the test display shall be
small enough for visual assessment. It is recommended that the luminance contribution from
background illumination reflected off the test display be less than or equal to 0,01 cd/m or
less than 1/20 of the display’s full screen black luminance.
It should be noted that, in case of mura defect in a black background, even low level of
background illumination can hinder the detection of mura.
To avoid the emitted light from the display being reflected back onto the display, the clothes
of the observer(s) and walls of the room shall be sufficiently dark.
4.4.2.3 Lighting conditions for reflective-type display modules
For reflective-type displays modules, visual assessment shall be carried out in a dark room,
as described in 4.4.2.2, however the display shall be illuminated by higher than 500 lx of
diffuse broadband illumination, such as hemispherical lighting.
Lighting conditions for visual assessment have several functions:
1) lighting is necessary for viewing reflective displays,
2) the spectral distribution, lighting geometry and display surround have to be specified so
that viewing conditions for visual assessment are reproducible,
3) lighting geometry has to be designed carefully so that lighting does not interfere with the
assessment of the display. For example, specular reflections of the light source by the
display into the field of view should be avoided because they can create a glare that can
hide defects that confound the observer.
4.4.2.4 Light conditions for assessment of physical damages
Physical damages shall be assessed using external lighting for both emissive-type display
and reflective type display devices.
The average illuminance on the display area shall be between 500 lx and 1 000 lx, as
measured at the display surface. The other illumination condition can be selected based on
the requirement of the customers, but the illuminance on the display shall not be less than
100 lx. Care shall be taken to block direct viewing of the light source by the observer. Either a
fluorescent light with the illuminant of FL1 illustrated in CIE 15 or other fluorescent lights can
be used [8].
Physic
...