Electronic displays devices - Part 2-5: Transparent displays - Measurements of optical characteristics

IEC TR 62977-2-5:2018(E) describes the conditions and measuring methods for determining the displayed properties (on-screen) and the through-screen properties of transparent direct­view­type liquid crystal displays (LCDs) and those of organic light emitting diode (OLED) displays.

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Status
Published
Publication Date
12-Nov-2018
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
13-Nov-2018
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IEC TR 62977-2-5
Edition 1.0 2018-11
TECHNICAL
REPORT
colour
inside
Electronic display devices –
Part 2-5: Transparent displays – Measurements of optical characteristics
IEC TR 62977-2-5:2018-11(en)
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IEC TR 62977-2-5
Edition 1.0 2018-11
TECHNICAL
REPORT
colour
inside
Electronic display devices –
Part 2-5: Transparent displays – Measurements of optical characteristics
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120; 31.260 ISBN 978-2-8322-6189-7

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 62977-2-5:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

4 Measuring conditions ....................................................................................................... 7

4.1 Standard measuring environmental conditions ........................................................ 7

4.2 Standard lighting conditions .................................................................................... 7

4.2.1 Darkroom conditions ........................................................................................ 7

4.2.2 Ambient illumination conditions ........................................................................ 7

4.2.3 Ambient illumination spectra ............................................................................ 8

4.3 Standard setup conditions ....................................................................................... 9

4.3.1 Starting conditions of measurements ............................................................... 9

4.3.2 Standard measuring positions .......................................................................... 9

4.3.3 Conditions of measuring equipment ................................................................. 9

5 Measuring methods of transparent properties ................................................................ 11

5.1 Hemispherical transmittance factor with specular included .................................... 11

5.1.1 Purpose ......................................................................................................... 11

5.1.2 Measuring conditions ..................................................................................... 11

5.1.3 Measuring method ......................................................................................... 12

5.2 Transmitted haze .................................................................................................. 13

5.2.1 General ......................................................................................................... 13

5.2.2 Transmitted haze under hemispherical illumination ........................................ 13

5.2.3 Transmitted haze with directly incident light ................................................... 15

5.3 Directional transmittance factor ............................................................................. 18

5.3.1 Purpose ......................................................................................................... 18

5.3.2 Measuring conditions ..................................................................................... 18

5.3.3 Measuring method ......................................................................................... 19

5.4 Degree of clear distinction of see-through objects ................................................. 20

5.4.1 General ......................................................................................................... 20

5.4.2 Purity ............................................................................................................. 20

5.4.3 Clarity (measurement method using a stripe pattern with a rigid width.) ......... 23

5.4.4 Clarity (Measuring method using a stripe pattern with gradually changed

width) ............................................................................................................ 26

5.5 Colour variation caused by a transparent display .................................................. 28

5.5.1 Purpose ......................................................................................................... 28

5.5.2 Measuring conditions ..................................................................................... 28

5.5.3 Measuring method ......................................................................................... 28

6 Measuring methods of on-screen properties .................................................................. 30

6.1 Ambient contrast ratio ........................................................................................... 30

6.1.1 Purpose ......................................................................................................... 30

6.1.2 Measuring conditions ..................................................................................... 30

6.1.3 Measuring method ......................................................................................... 31

6.2 Display ambient colour measurement .................................................................... 32

6.2.1 Purpose ......................................................................................................... 32

6.2.2 Measuring conditions ..................................................................................... 32

6.2.3 Measuring method ......................................................................................... 32

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IEC TR 62977-2-5:2018 © IEC 2018 – 3 –

6.3 Contrast ratio and colour coordinate with the incident illumination originating

from objects behind the screen ............................................................................. 33

6.3.1 Purpose ......................................................................................................... 33

6.3.2 Measuring method with white light source ...................................................... 35

6.3.3 Measuring method with collimated or directional light source ......................... 37

Bibliography .......................................................................................................................... 39

Figure 1 – Measurement points ............................................................................................... 9

Figure 2 – Layout diagram of measurement setup ................................................................. 10

Figure 3 – Side view of measuring concept for the hemispherical transmittance factor

measurement with specular included or excluded ................................................................. 13

Figure 4 – Schematic arrangement of haze measurement ..................................................... 15

Figure 5 – Schematic arrangement of the apparatus (TOP view) ........................................... 17

Figure 6 – Side view of measuring concept for the hemispherical transmittance factor

measurement with specular included or excluded ................................................................. 20

Figure 7 – Measuring configuration for purity measurement .................................................. 22

Figure 8 – Test patterns for purity measurement ................................................................... 22

Figure 9 – Measuring system and its configuration ................................................................ 24

Figure 10 – Example reference object and its configuration .................................................. 25

Figure 11 – Luminance curve of reference object .................................................................. 25

Figure 12 – Definition of test parameters .............................................................................. 26

Figure 13 – Reference object and its configuration................................................................ 27

Figure 14 – The relationship between stripe frequency and Michelson contrast ratio ............. 28

Figure 15 – Measuring configuration ..................................................................................... 29

Figure 16 – Geometry of the transparent display and the bright background object ............... 34

Figure 17 – Case with bright background .............................................................................. 35

Figure 18 – Measurement configuration for transparent display with background object ........ 37

Table 1 – Standard ambient conditions ................................................................................... 8

Table 2 – Measuring conditions of the ports .......................................................................... 15

Table 3 – Measurements ....................................................................................................... 18

Table 4 – Measured example for purity ................................................................................. 23

Table 5 – Example of reported specification of two dimensional LMD .................................... 23

Table 6 – Working example for colour variation index ........................................................... 30

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– 4 – IEC TR 62977-2-5:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRONIC DISPLAY DEVICES –
Part 2-5: Transparent displays –
Measurements of optical characteristics
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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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 62977-2-5, which is a technical report, has been prepared by IEC technical

committee 110: Electronic display devices.
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IEC TR 62977-2-5:2018 © IEC 2018 – 5 –
The text of this technical report is based on the following documents:
Draft TR Report on voting
110/919/DTR 110/935B/RVDTR

Full information on the voting for the approval of this technical report 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 62977 series, published under the general title Electronic 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

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understanding of its contents. Users should therefore print this document using a

colour printer.
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– 6 – IEC TR 62977-2-5:2018 © IEC 2018
ELECTRONIC DISPLAY DEVICES –
Part 2-5: Transparent displays –
Measurements of optical characteristics
1 Scope

This part of IEC 62977 describes the conditions and measuring methods for determining the

displayed properties (on-screen) and the through-screen properties of transparent

direct-view-type liquid crystal displays (LCDs) and those of organic light emitting diode (OLED)

displays.
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 62341-6-4:2017, Organic light emitting diode (OLED) displays – Part 6-4: Measuring

methods of transparent properties

IEC 62341-6-2, Organic light emitting diode (OLED) displays – Part 6-2: Measuring methods

of visual quality and ambient performance
3 Terms and definitions
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
transparent display module

display module which can show the information on the screen and allow objects behind the

display to be viewed through the screen
3.2
on-screen property
image quality attributes when the intended information is on the display panel
3.3
through-screen property

image quality attributes when the intended information is behind the display panel and is

viewed through it
3.4
transmittance

ratio of the transmitted radiant or luminous flux to the incident flux in the given conditions

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IEC TR 62977-2-5:2018 © IEC 2018 – 7 –
3.5
transmitted haze

percent of transmitted light that is scattered more than 2,5° from the direction of the incident

beam
3.6
clarity

measure based on luminance modulations from stripe patterns to represent the degree of

clear distinction of see-through objects
3.7
purity

ratio of luminance which is measured in a 0,2° region to luminance of total transmitted light in

a transparent display panel to represent the degree of clear distinction of see-through objects

3.8
colour shift

change in chromaticity of the reference object when viewed through a transparent display

device
3.9
contrast ratio offset

change in contrast ratio of the reference object when viewed through a transparent display

device
4 Measuring conditions
4.1 Standard measuring environmental conditions
Measurements are carried out under the standard environmental conditions:
– temperature: 25 °C ± 3 °C,
– relative humidity: 25 % to 85 %,
– atmospheric pressure: 86 kPa to 106 kPa.

When different environmental conditions are used, they are noted in the measurement report.

4.2 Standard lighting conditions
4.2.1 Darkroom conditions

The luminance contribution from unwanted background illumination reflected off the test

display shall be less than 1/20 of the display's black state luminance. If this condition is not

satisfied, then background subtraction is required and it shall be noted in the test report. In

addition, if the sensitivity of the light measuring device (LMD) is inadequate to measure at

these low levels, then the lower limit of the LMD shall be noted in the test report.

4.2.2 Ambient illumination conditions

Ambient lighting conditions will make a large impact on the performance of a transparent

display. For observers who watch a transparent display, various ambient conditions are

suggested based on previous research. Table 1 shows the standard indoor and daylight

ambient illumination conditions.
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– 8 – IEC TR 62977-2-5:2018 © IEC 2018

Uniform hemispherical diffuse illumination is used to simulate the background lighting in a

room or the hemispherical skylight incident on the display, with sun occluded. The detailed

information to simulate those ambient conditions is described in IEC 62341-6-2 [1] and in

IDMS [2].
Table 1 – Standard ambient conditions
Design screen Recommended
Indoor and daylight illumination environment
illuminance illumination geometry

Up to 200 lx (mostly) General building areas (ISO 9241-307 [3]) 60 % hemispherical,

40 % directional at 45°

Up to 300 lx (mostly) General machine work, rough assembly work, (general) 60 % hemispherical,

museum (ISO 9241-307), office environment
40 % directional at 45°

Up to 500 lx Medium assembly and decorative work, simple inspection, 60 % hemispherical,

counters, libraries, (mostly) educational areas, control rooms
40 % directional at 45°
(ISO 9241-307)
Up to 750 lx Fine work, technical drawing (ISO 9241-307) 60 % hemispherical,
40 % directional at 45°

Up to 1 000 lx Precision work, quality control, inspection, medical examination 60 % hemispherical,

and treatment (ISO 9241-307)
40 % directional at 45°
Up to 1 500 lx High-precision work (ISO 9241-307) 60 % hemispherical,
40 % directional at 45°

> 1 500 lx Special workplaces in the medical area (ISO 9241-307) 60 % hemispherical,

40 % directional at 45°

80 000 lx The daylight contrast ratio and colour is calculated using a 15 000 lx hemispherical,

combination of hemispherical diffuse illumination (with specular
65 000 lx directional at 45°
included) and directional illumination incident on a display surface
in a vertical orientation
4.2.3 Ambient illumination spectra

The ambient performance of the display can be significantly impacted by the spectral

distribution of the illumination source. Unless it is specified otherwise, the source illumination

closely approximates CIE Illuminant D65 [4]. The source illumination used for measuring the

display reflection and transmission properties has a spectrally smooth and broadband

emission. Spectral reflection and transmission measurements can then be used to predict the

ambient display performance for any desired illumination spectra.

When evaluating the display's ambient indoor performance, it is recommended to use the

same spectral distribution for the hemispherical and directional source illumination. Light

source spectra approximating CIE Illuminant A, Illuminant D50, and Illuminant D65 are

recommended for indoor applications. In order to simulate outdoor applications, Illuminant

D50 is recommended for the directional illumination, and Illuminant D75 is recommended for

hemispherical illumination.
___________
Numbers in square brackets refer to the Bibliography.
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IEC TR 62977-2-5:2018 © IEC 2018 – 9 –
4.3 Standard setup conditions
4.3.1 Starting conditions of measurements

Measurements will be started after the displays and measuring instruments achieve stability.

The display under test (DUT) will be turned on first and operated for at least 30 min prior to

the measurement. Some display technologies may need a loop of colour patterns rendered on

the screen during the warm-up period. Sufficient warm-up time has been achieved when the

luminance of the test feature to be measured varies by less than ± 3 % over the entire

measurement period for a given display image.
4.3.2 Standard measuring positions

Luminance, radiance distribution and/or tristimulus values may be measured at several

specified positions on the DUT surface; see Figure 1. Unless otherwise specified,

measurements are carried out in the centre of each circle. Care is taken that the measuring

spots on the display do not overlap.

Any deviation from the above-described standard positions is added to the detail specification.

H/2 H/10
P P P
1 5 2
P P P
8 0 6
P P P
4 7 3
IEC
Figure 1 – Measurement points
4.3.3 Conditions of measuring equipment

General conditions of the measuring equipment specified in IEC 62341-6-2 are adopted.

Three different LMDs may be applied to the measurements of the light transmitted and/or

reflected by the DUT: a luminance meter, a colorimeter or a spectroradiometer. If measuring

segmented displays, the measurement field area is located completely inside a single

segment, and does not include any of its surroundings.

For DUT which is not equipped with its own source of illumination, an external light source

which has the same size as that of the DUT is used. Assemble the back light source with the

transparent display module to ensure that there is no light leakage.
V/10 V/2
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– 10 – IEC TR 62977-2-5:2018 © IEC 2018

Measure the following parameters of the light source in the plane of the DUT at P and other

relevant positions from P to P (Figure 1); measure and specify:
1 8
a) spectrum of emission;
b) luminance L;
c) temporal stability of the luminance L(t).
The general conditions of the measurement are as follows:

1) The standard measurement setup is shown in Figure 2. The LMD is a luminance meter,

colourimeter, or a spectroradiometer capable of measuring spectral radiance over at least

the 380 nm to 780 nm wavelength range, with a maximum bandwidth of 10 nm for smooth

broadband spectra. For light sources that have sharp spectral features, like LEDs and

fluorescent lamps, the spectroradiometer's maximum bandwidth is less than 5 nm. The

spectral bandwidth of the spectroradiometer is an integer multiple of the sampling interval.

For example, a 5 nm sampling interval can be used for a 5 nm or 10 nm bandwidth. Care

is taken to ensure that the device has enough sensitivity and dynamic range to perform

the required task.
Acceptance area
Field of view
Angular field of
view
Angular aperture
Measurement
field
Measurement-field angle
IEC
Figure 2 – Layout diagram of measurement setup

2) The LMD is focused on the image plane of the transparent display for on-screen

performance and on the image plane of the background for transmission performance.

The LMD is aligned perpendicularly to its surface, unless stated otherwise.

3) The relative uncertainty and repeatability of all the measuring devices is maintained by

following the instrument supplier's recommended calibration schedule.

4) The LMD integration time is an integer number of frame periods, synchronized to the

frame rate, or the integration time is greater than 200 frame periods.

5) When measuring matrix displays, the LMDs are set to a measurement field that includes

more than 500 pixels. If smaller measurement areas are necessary, equivalence to
500 pixels is confirmed.

6) The angular aperture is less than or equal to 5°, and the measurement field angle is less

than or equal to 2° (see Figure 2). The measuring distance and the aperture angle may be

adjusted to achieve a measuring field greater than 500 pixels if setting the above aperture

angle is difficult.

7) Display modules are operated at their design field frequency. When using separate driving

signal equipment to operate a panel, the drive conditions are noted in the performance

report.
Any deviations from these conditions are noted in the performance report.
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IEC TR 62977-2-5:2018 © IEC 2018 – 11 –
5 Measuring methods of transparent properties
5.1 Hemispherical transmittance factor with specular included
5.1.1 Purpose

The purpose of this method is to measure the transmitted light, including the specular

component, through a transparent display.
NOTE This method was originally specified for transparent OLED displays.
5.1.2 Measuring conditions
For this measurement, the following conditions are appl
...

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