IEC TR 62595-1-3:2019

Display lighting unit - Part 1-3: Lighting units with arbitrary shapes

IEC TR 62595-1-3:2019 (E) focuses on common issues of light emission such as spatial uniformity of luminance and colour, and angular distribution of luminance and colour, from lighting units with arbitrary shapes like flexible lighting sources (FLSs). This document provides a model of light emission from a curved FLS and of light measurement on a curved FLS. Because the development of flexible liquid crystal panels is in progress (see the notes), the intent of this document is to provide guidance for the development of future measurement standards. This document is applicable to FLSs either as light sources, products or elements with arbitrary shapes of geometrical curvature having different spectral and spatial characteristics of light emission.
NOTE 1 Almost 20 years ago plastic LCDs were developed and used in a few applications.
NOTE 2 Flexible BLUs have been used for bendable LC panels in recent years.
NOTE 3 Recent transmissive and transflective flexible LCs require flexible BLUs.

General Information

• Status: Published
• Publication Date: 03-Apr-2019
• ICS: 31.120 - Electronic display devices
• ICS: 31.260 - Optoelectronics. Laser equipment
• Technical Committee: TC 110 - Electronic displays
• Current Stage: PPUB - Publication issued
• Start Date: 04-Apr-2019
• Completion Date: 29-Apr-2019

Overview

IEC TR 62595-1-3:2019 is a technical report published by the International Electrotechnical Commission (IEC) focusing on display lighting units with arbitrary shapes, primarily flexible lighting sources (FLSs). As the demand for flexible, stretchable, and conformable displays grows - particularly in electronics and wearable technology - it is crucial to address new challenges in the characterization and measurement of light emission from lighting units that are no longer flat, but exhibit various geometric curvatures.

This document provides a comprehensive framework for understanding and modeling the light emission properties of curved and flexible lighting units. It considers critical aspects such as spatial and angular uniformity of luminance and colour, and the implications of arbitrary shapes on measurement accuracy using current technologies. IEC TR 62595-1-3:2019 serves as a foundational guideline for developing future measurement standards, supporting the evolving requirements of innovative display and lighting applications.

Key Topics

• Flexible Lighting Units (FLSs): Covers the various forms of FLSs including foldable, bendable, rollable, and stretchable types. Flexible lighting units differ from traditional rigid lighting units due to their unique mechanical and optical characteristics.
• Optical Measurement Challenges: Highlights complexities in measuring optical quantities (such as luminance, luminance uniformity, chromaticity, and angular light distribution) on curved surfaces versus flat surfaces.
• Measurement Models and Methods:
  • Modeling and analyzing the projection of the measurement field (MF) on curved surfaces.
  • Geometrical characterization of FLSs with single and arbitrary curvatures.
  • Addressing the effects of curvature on depth of focus and measurement device accuracy.
• Spatial and Angular Characteristics: Examination of spatial uniformity, angular distribution of luminance and colour, and how display unit curvature influences perceived optical performance.
• Implications for Standards Development: Provides guidance for the development of future standards, especially for new generations of flexible liquid crystal panels and related display techniques.

Applications

IEC TR 62595-1-3:2019 is significant for a wide range of stakeholders in the electronics, display, and lighting industries, including:

• Manufacturers of Flexible Displays: Enables accurate evaluation of curved OLED and LED panels used in televisions, smartphones, advertising displays, and wearable devices.
• Automotive and Aerospace Sectors: Supports integration of flexible lighting units into vehicles and aircraft where lightweight, adaptive, and durable lighting or display elements enhance design and functionality.
• Healthcare and IoT Solutions: Provides a foundation for flexible light-based devices such as medical wearables or smart textiles where conformable and biocompatible lighting is essential.
• Measurement Equipment Developers: Offers insights into adapting or designing new luminance and chromaticity measurement devices capable of reliable performance on non-planar surfaces.
• Research and Development: Serves as an essential resource for academic and industrial research on next-generation flexible light sources and their standardization requirements.

Related Standards

Professionals applying IEC TR 62595-1-3:2019 will find value in consulting related international standards, including but not limited to:

• IEC 62715 Series: Focuses on flexible display devices, including terminology, measuring methods for optical performance, visual assessment, and mechanical/environmental testing (e.g., IEC 62715-1-1, 62715-5-1, 62715-6-1).
• IEC 62899 Series: Pertains to printed electronics, which encompass technologies crucial for flexible lighting unit manufacturing and integration.
• IEC TS 62715-5-2: Provides further measuring methods of optical characteristics from the vantage point for curved displays.
• JEITA Et4501: Addresses printed electronics – OLED elements relevant to FLS production.

By referencing IEC TR 62595-1-3:2019 alongside these standards, organizations can ensure comprehensive compliance and stay at the forefront of flexible lighting and display technology development.

Standards Content (Sample)

IEC TR 62595-1-3 ®
Edition 1.0 2019-04
TECHNICAL
REPORT
colour
inside
Display lighting unit –
Part 1-3: Lighting units with arbitrary shapes

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 [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
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 corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
IEC TR 62595-1-3 ®
Edition 1.0 2019-04
TECHNICAL
REPORT
colour
inside
Display lighting unit –
Part 1-3: Lighting units with arbitrary shapes

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120; 31.260 ISBN 978-2-8322-6721-9

– 2 – IEC TR 62595-1-3:2019  IEC 2019
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 7
4 Flexible lighting units . 8
4.1 General . 8
4.2 FLSs possessing arbitrary curvature . 9
5 Single-curvature FLS model. 10
6 FLS light emission directionality . 12
7 Measurement field projection on a curved FLS . 14
8 Discussion and conclusions . 17
Bibliography . 18

Figure 1 – Examples of curved FLS and curved display . 8
Figure 2 – FLS with an arbitrary curvature and measurement system . 9
Figure 3 – FLS element with curvature and change of measurement field contour due
to curvature . 10
Figure 4 – Curved FLS with convex and concave curvatures . 12
Figure 5 – Radiation pattern of FLSs with nearly Lambertian luminous intensities (n =
0,8, 1, 1,2) and collimated light intensities (n = 5, 10, 15) in a spherical coordinate
system . 13
Figure 6 – Radiation pattern profiles of FLSs with nearly Lambertian luminous
intensities (n = 0,8, 1, 1,2) . 13
Figure 7 – Confined flux in solid angles (θ = 0° to 90°) for intensity distributions with n
= 0,8, 1, 1,2 and 15 . 14
Figure 8 – LMD’s cone cross section nearly equal to that of the FLS’s diameter . 14
Figure 9 – Contour of projected measurement field’s cone cross section on a
cylindrical FLS . 15
Figure 10 – Contour of a cone’s cross section of the measurement field on a large
radius cylindrical FLS R = ∞ (flat) . 15
FLS
Figure 11 – Off-axis measurement and cone’s cross section contour on the DUT (right
half expanded and left half contracted) . 15
Figure 12 – Measurement field cone’s cross section contour on a cylindrical FLS
versus the angle between the LMD and DUT axes (δ) . 16
Figure 13 – Cross section of the measurement field (cone's cross section) with the
angle (δ) between the LMD and DUT axes, on a concave cylindrical FLS . 16

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DISPLAY LIGHTING UNIT –
Part 1-3: Lighting units with arbitrary shapes

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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 62595-1-3, which is a technical report, has been prepared by IEC technical
committee 110: Electronic displays.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
110/1018/DTR 110/1064/RVDTR
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.

– 4 – IEC TR 62595-1-3:2019  IEC 2019
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62595 series, published under the general title Display lighting
unit, 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.
INTRODUCTION
Recent developments in materials for flexible lighting sources (FLSs) with arbitrary shapes
such as organic light emitting devices (OLEDs) have boosted their fabrication process as well
as expanding their applications in various fields, for example electronic displays and wearable
display devices. Since FLSs can emit light in a curved and deformed shape even under
external stress, which is different from that of the devices with rigid substrates, these
characteristics and performances require new evaluation and measurement methods. This
document focuses on common issues of light emission from FLSs such as spatial uniformity of
luminance and colour, and angular distribution of luminance and colour. This document
delivers an archetype of a curved FLS's light emission and its measurement. The intent of this
document is to provide guidance for the development of future measurement standards.

– 6 – IEC TR 62595-1-3:2019  IEC 2019
DISPLAY LIGHTING UNIT –
Part 1-3: Lighting units with arbitrary shapes

1 Scope
This part of IEC 62595 focuses on common issues of light emission such as spatial uniformity
of luminance and colour, and angular distribution of luminance and colour, from lighting units
with arbitrary shapes like flexible lighting sources (FLSs). This document provides a model of
light emission from a curved FLS and of light measurement on a curved FLS. Because the
development of flexible liquid crystal panels is in progress (see the notes), the intent of this
document is to provide guidance for the development of future measurement standards. This
document is applicable to FLSs either as light sources, products or elements with arbitrary
shapes of geometrical curvature having different spectral and spatial characteristics of light
emission.
NOTE 1 Almost 20 years ago plastic LCDs were developed and used in a few applications.
NOTE 2 Flexible BLUs have been used for bendable LC panels in recent years.
NOTE 3 Recent transmissive and transflective flexible LCs require flexible BLUs.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
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
3.1 Terms and definitions
3.1.1
plane FLS
light emission from a flat surface
3.1.2
convex FLS
light emission from a convex curved surface
3.1.3
concave FLS
light emission from a concave curved surface
3.1.4
transparent FLS
FLS with transparent substrate that emits light from both front and back surfaces, or otherwise
from the inner or outer surfaces

3.1.5
foldable FLS
FLS bent over upon itself
3.1.6
bendable FLS
long or thin FLS forced from a straight form into a curved or angular one, or from a curved or
angular form into some different form
3.1.7
rollable FLS
FLS capable of rolling or being rolled
3.1.8
stretchable FLS
FLS capable of being stretched, or fabricated on a stretchable or elastic substrate
3.1.9
single-curvature surface emission FLS
FLS that possesses a single radius of curvature, whether negative or positive, along its length,
width or diagonal
3.1.10
white emission FLS
FLS with phosphor or any phosphor-like material converted white light emission
3.1.11
monochromatic emission FLS
FLS with a narrow band emission of light
3.1.12
chromatic emission FLS
FLS with polychromatic light emission
3.1.13
spatial characteristics
information on measurement point position, area, and size or images captured from spatial
view-points at successive time intervals that are shown together on a single picture
3.2 Abbreviated terms
ALD angular luminance distribution
BLU backlight unit
DLU display lighting unit
DUT device under test
FLS flexible light source
LCD liguid crystal display
LED light emitting diode
LMD light measuring device
MF measurement field
OLED organic light emitting diode
VLU virtual luminance uniformity

– 8 – IEC TR 62595-1-3:2019  IEC 2019
4 Flexible lighting units
4.1 General
Recent developments in materials for flexible lighting sources (FLSs) such as organic light
emitting devices (OLEDs) have expanded their applications in various fields, for example
electronic displays and wearable display devices. Their exceptional characteristics, i.e., the
flexibility of lighting units, have accelerated the usages of wearable devices.
FLSs are innovative elements with planar light emitting elements. FLSs have excellent surface
emission characteristics with mechanical durability as shown in the lighting and display
devices in Figure 1 [1] . Surface light emitting FLSs are applicable to the fields of display
lightings in the wearable, internet of things (IoT), and healthcare industries, and are expected
to be a large promising market [1 to 28].

a) White flexible FLS element for display b) Curved display
illumination (back or front)
Figure 1 – Examples of curved FLS and curved display
Nowadays the piecewise and roll-to-roll manufacturing approaches are being explored while
addressing problems in FLS durability, efficiency and luminance homogeneity. In addition, the
material research, plant construction, component technology and application are being
studied for future elements and products [12 to 16].
Since the flexible planar lighting units are thin, light-weight, and have geometrical
deformability, i.e., bending, rolling, folding, and stretching, these properties can benefit the
automobile and aircra
...