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
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
04-Apr-2019
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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
IEC TR 62595-1-3:2019-04(en)
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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

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 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

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IEC TR 62595-1-3:2019  IEC 2019 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DISPLAY LIGHTING UNIT –
Part 1-3: Lighting units with arbitrary shapes
FOREWORD

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The main task of IEC technical committees is to prepare International Standards. However, a

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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.
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– 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.
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colour printer.
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IEC TR 62595-1-3:2019  IEC 2019 – 5 –
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.

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– 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
---------------------- Page: 8 ----------------------
IEC TR 62595-1-3:2019  IEC 2019 – 7 –
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
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– 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
...

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