IEC TR 62977-2-5:2018

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.

General Information

• Status: Published
• Publication Date: 12-Nov-2018
• 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: 13-Nov-2018
• Completion Date: 01-Nov-2018

Overview

IEC TR 62977-2-5:2018 is a Technical Report from the International Electrotechnical Commission (IEC) that specifies conditions and measurement methods for the optical characteristics of transparent direct‑view displays. It covers both transparent LCD and OLED display modules and defines how to measure both on‑screen properties (the displayed image) and through‑screen properties (objects seen behind the display). This report is part of the IEC 62977 series on electronic display devices and provides standardized test setups, ambient lighting conditions, and measurement positions to ensure repeatable optical characterization of transparent displays.

Key topics and technical requirements

The document organizes measurement guidance into two main groups-through‑screen (transparent) properties and on‑screen (displayed) properties. Major technical topics include:

• Measuring conditions and setup

  • Standard environmental and ambient illumination conditions
  • Darkroom and ambient lighting spectra
  • Standard measurement positions and instrument conditions

• Through‑screen optical metrics

  • Hemispherical transmittance factor (specular included/excluded)
  • Transmitted haze (under hemispherical and direct illumination)
  • Directional transmittance factor
  • Degree of clear distinction (metrics such as purity and clarity using stripe patterns)
  • Colour variation caused by the transparent display

• On‑screen optical metrics

  • Ambient contrast ratio and contrast measurement in ambient light
  • Display ambient colour measurement
  • Contrast and colour coordinates with background illumination (including methods for white and collimated directional background sources)

The report references related test procedures (for example IEC 62341 parts on OLED measurement methods) and includes figures and tables detailing measurement geometries and sample configurations.

Practical applications and users

IEC TR 62977-2-5:2018 is useful for anyone needing consistent, repeatable optical characterization of transparent displays:

• Display manufacturers developing transparent LCD or OLED modules
• Test and calibration laboratories performing optical performance verification
• System integrators specifying transparent displays for retail, automotive HUDs, AR windows, signage, or architectural applications
• Procurement and QA teams defining acceptance criteria and comparing supplier claims
• R&D teams evaluating tradeoffs between transparency, haze, and on‑screen visibility

Using this standard helps ensure objective comparisons of transmittance, haze, clarity, colour shift and ambient contrast-critical for user experience in transparent display applications.

Related standards

• IEC 62341-6-4:2017 - OLED displays: measuring transparent properties
• IEC 62341-6-2 - OLED displays: visual quality and ambient performance
• Other parts of the IEC 62977 series on electronic display devices

Keywords: IEC TR 62977-2-5:2018, transparent displays, measurements of optical characteristics, transmittance, haze, clarity, purity, ambient contrast ratio, LCD, OLED.

Standards Content (Sample)

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

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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

– 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

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

– 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
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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.

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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– 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

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.

– 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.

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
H
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
V
– 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.

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 applied.
a) Apparatus:
1) light measuring device that can measure luminance or spectral radiance;
2) driving power source;
3) driving signal equipment;
4) integrating sphere with ports and a stabilized light source (see Figure 3), which is as
follows:
i) The light source in the integrating sphere has a smooth broadband spectrum
approximating CIE standard illuminant D65 [4]. The integrating sphere has a
photopic optical detector which monitors the relative luminance level m inside the
sphere. The monitor is fitted with baffles to prevent light from the light source or
the sample port from falling on it directly. The spectral characteristics of the light
source are kept constant during measurements on a transparent display. The
measurement conditions are such that the transparent display temperature does
not increase while measurements are made.
ii) The integrating sphere may be of any diameter as long as the total port area does
not exceed 4,0 % of the internal area of the sphere. It is recommended that the
diameter of the integrating sphere be not less than 150 mm so that specimens of a
reasonable size can be used. When the diameter of the integrating sphere is
150 mm and the diameters of the sample, compensation and light trap ports are
30 mm, the ratio of the total port area to the internal area of the sphere is 3,0 %.
For specular included measurements, a port plug or diffuse white standard with
similar reflectance to the inner wall can be used to fill the port. A sphere geometry
may also be used instead of the configuration illustrated in Figure 3
(see IEC 62341-6-4:2017, Annex A). If the integrating sphere does not have a
compensation port, and placing the display at the sample port significantly
changes the spectral distribution of the light in the sphere, the alternate sphere
method in IEC 62341-6-4:2017, Annex A shall be used. In addition, if it is
necessary to measure the hemispherical transmittance factor with the display on,
then the alternate sphere method is used.
iii) It is recommended to use a sample port with a diameter of between 30 mm to
75 mm. If a compensation port is used, the sample and compensation ports of the
integrating sphere are circular and of the same size. The compensation port is
positioned at an angle of less than 1,57 rad (90°) from the sample port. The
sample port, compensation port and light trap port will not lie on the great circle of
the sphere. The ports are designed in such a way that samples placed at the port
lie at nearly the same surface as the inner sphere wall.
iv) The surfaces of the interior of the integrating sphere and the baffles are of
substantially equal luminous reflectance which is 90 % or more and does not vary
by more than ±3 %. The sphere wall reflectance can be determined relative to a
known reflection standard using the method described in IEC 62341-6-4:2017,
Annex A.
– 12 – IEC TR 62977-2-5:2018 © IEC 2018
v) Using this instrument, the repeatability standard deviation is 0,2 % or less. The
within-laboratory reproducibility over long time intervals does not exceed the
repeatability by a factor of 3.
vi) The flat sample is held against the sample port so that the normal of the sample is
within 2° of the normal of the sample port. The sphere interior provides uniform
illumination on the screen, with the screen receiving a constant luminance over its
hemispherical inclination angles. This criterion is often satisfied when the sphere's
internal light source dominates the illuminance inside the sphere compared to any
sample contribution.
vii) The LMD is aligned normal to the centre of the sample port at an approximate
distance of 0,5 m. The measurement field is focused on the sample port plane.
b) Standard measuring environmental conditions:
1) darkroom conditions;
2) standard setup conditions.
5.1.3 Measuring method
The method is similar to ASTM D1003 [5], and analogous to ISO 13468-1 [6]. This method
assumes that the transmission properties of the transparent display are not affected by the
illumination level on the display.
NOTE This method also assumes that the transmission properties are invariant to the rendered colour on the
display, and allows the transmission properties to be measured with the DUT in the maximum transparent state.
a) If the integrating sphere has a light trap port, place a port plug or diffuse white standard at
the port. Turn on the integrating sphere light source and allow the light source and LMD to
stabilize. The measurement configuration in Figure 3 is set up in a dark room, and ingress
of external light into the integrating sphere is prevented.
b) If the integrating sphere has a compensation port, place the back side of the transparent
display against that port.
c) Measure the luminance L or spectral radiance at the sample port, and record the
ref
monitor detector value m .
ref
d) Place the back side of the transparent display against the sample port. If the integrating
sphere has a compensation port, place a light trap at that port. Measure the transmitted
, and record the monitor detector
luminance (or spectral radiance) at the sample port L
di/0
value m .
di/0
e) Calculate the luminous hemispherical transmittance factor with specular included T
di/0
using Formula (1):
Lm
di/0 ref
T ⋅ (1)
di/0
Lm
ref di/0
f) Repeat the readings for L , m , L , and m , making additional readings with the
ref ref di/0 di/0
specimen in positions selected to determine uniformity.
g) Carry out the procedure three times, and use the average of the three calculated results
as the luminous hemispherical transmittance factor value.
h) All details are required to be recorded for identification of the test specimens and the
source of the specimens (type of light source used, information of transparent display).
=
Optical
monitor
Light-trap
port
Sample
Black
Detector
glass
"Exit port"
(sample port)
Compensation port
White
standard
IEC
Figure 3 – Side view of measuring concept for the hemispherical
transmittance factor measurement with specular included or excluded
5.2 Transmitted haze
5.2.1 General
Two different measuring methods are specified for transmitted haze. The measuring method
for transmitted haze under hemispherical illumination is specified in 5.2.2. In addition, the
measuring method for transmitted haze with directly incident light is specified in 5.2.3.
5.2.2 Transmitted haze under hemispherical illumination
5.2.2.1 Purpose
The purpose of this method is to measure the amount of haze transmitted to the viewer from a
transparent display back-illuminated with hemispherical illumination.
NOTE This method was originally specified for transparent OLED displays.
5.2.2.2 Measuring conditions
For this measurement, the following conditions are applied.
a) Apparatus:
1) light measuring device that can measure luminance or spectral radiance;
2) driving power source;
3) driving signal equipment;
4) integrating sphere with ports and a stabilized light source (see Figure 3), which is as
follows:
i) The light source in the integrating sphere has a smooth broadband spectrum
approximating CIE standard Illuminant D65 [4]. The integrating sphere has a
photopic optical detector which monitors the relative luminance level m inside the
sphere. The monitor is fitted with baffles to prevent light from the light source or
the sample port from falling on it directly. The spectral characteristics of the light
source are kept constant during measurements on a transparent display. The
measurement conditions are such that the transparent display temperature does
not increase while measurements are made.

– 14 – IEC TR 62977-2-5:2018 © IEC 2018
ii) The total port area of the integrating sphere does not exceed 4,0 % of the internal
area of the sphere. It is recommended that the diameter of the integrating sphere
be not less than 150 mm so that specimens of a reasonable size can be used.
When the diameter of the integrating sphere is 150 mm and the diameters of the
sample, compensation and light trap ports are 30 mm, the ratio of the total port
area to the internal area of the sphere is 3,0 %. If the integrating sphere does not
have a compensation port, and placing the display at the sample port does not
significantly change the spectral distribution of the light in the sphere, the monitor
detector is used to compensate for change in the sphere illuminance due to the
presence of the display at the sample port.
iii) The sample port and light trap port are centred on the same optical axis as the
LMD. The diameter of the sphere z , and the light trap port diameter d are sized
s LT
such that the opening of the light trap port subtends θ = 8° from the centre of the
LT
sample port. The LMD is positioned a distance z away from the sphere,
LMD
producing a measurement field of diameter d focused at the sample port, where
mf
d = z d /(z + z ) and d is the projected measurement field diameter at
mf d pmf LMD s pmf
the light trap port. The LMD and sphere are set up in such a way that the angular
gap (annulus) ξ = θ /2 – arctan[d /(2 z )] between the projected measurement
LT pmf s
field diameter d and the light trap port diameter gives ξ = 1,3°. When the above
pmf
requirements are satisfied, the maximum angle φ that any measured light ray can
have relative to the normal is less than 3°. Ensure that the LMD measurement field
is contained within the image of the light trap port area.
A detailed illustration of the specular excluded and transmitted haze geometry is
given in Figure 4.
b) Standard measuring environmental conditions:
1) darkroom conditions;
2) standard set-up conditions.
5.2.2.3 Measuring method
The method is similar to that of ASTM D1003 [5] and analogous to that of ISO 14782 [7].
This method assumes that the transmission properties of the transparent display are not
affected by the illumination level on the display.
NOTE This method also assumes that the transmission properties are invariant to the rendered colour on the
display, and allows the transmission properties to be measured with the DUT in the maximum transparent state.
a) Place a port plug or diffuse white standard at the light trap port. Turn on the integrating
sphere light source and allow the light source and LMD to stabilize. The measurement
configuration in Figure 3 is set up in a dark room, and ingress of external light into the
integrating sphere is prevented.
b) If the integrating sphere has a compensation port, place the back side of the transparent
display against that port.
c) Align the LMD normal to the sample port and focus the measurement field at the centre of
the port. Measure the luminance L at the centre of the sample port, and record the
monitor detector value m .
d) Place the back side of the transparent display against the sample port. If the integrating
sphere has a compensation port, place a light trap at that port.
e) Measure the transmitted luminance L through the display at the centre of the sample port,
and record the monitor detector value m .
f) Replace the port plug or diffuse white standard at the light trap port with a light trap. If the
integrating sphere has a compensation port, place the port plug or the diffuse white
standard at that port. Measure the transmitted luminance L through the display at the
centre of the sample port, and record the monitor detector value m .
g) Remove the transparent display from the sample port. Measure the luminance L at the
centre of the sample port, and record the monitor detector value m .
h) The luminous hemispherical transmittance factor with specular excluded T is given
Q,de/0
as:
L Lm
mL
32 1
 (2)
T −
Q,de/0
L m Lm m
14 13 2
where each variable is associated with the measurement configuration list in Table 2.
i) The percentage of luminous hemispherical transmitted haze H is determined by:
de/0

Lm Lm
42 31
(3)

H =100%× −
de/0
L m Lm
2 4 13
Table 2 – Measuring conditions of the ports
Measured Sample port Light trap port Compensation port
Luminance
L White reference Display sample
L Display sample White reference Light trap
L Light trap White reference
L Display sample Light trap White reference
j) All details are required to be recorded for identification of the test specimens and the
source of the specimens, such as type of light source used, information on transparent
display.
Sphere
LMD
Sample
ξ
port
Light trap
port
φ
d d d
pmf θ mf sp
LT
Z
Z
LMD
S
IEC
Figure 4 – Schematic arrangement of haze measurement
5.2.3 Transmitted haze with directly incident light
5.2.3.1 Purpose
The purpose of this method is to measure the transmitted haze with directly incident light for a
transparent display module. This method is equivalent to that in 5.2.2 [5, 7].
NOTE This method was originally specified for transparent LCD displays.
=
– 16 – IEC TR 62977-2-5:2018 © IEC 2018
5.2.3.2 Measuring conditions
For this measurement, the following conditions are applied.
a) Apparatus (see Figure 5):
1) light measuring device that can measure luminance or spectral radiance;
2) driving power source;
3) driving signal equipment;
4) integrating sphere with ports and a stabilized light source which is as follows:
i) The light source and the photometer is used in conjunction with a filter to provide
an output corresponding to the photopic standard luminous efficiency V(λ) (as
defined in IEC 60050-845 [8]). V(λ) is identical to the colour-matching function y(λ)
specified in CIE S 014-1/E:2006 [9] under CIE standard illuminant D65 [4]. By
measuring the spectral power distribution of the light source using the detector in
advance, the measured spectral information is used to determine the equivalent
result for a D65 light source. The output of the photodetector is proportional to the
incident flux, to within 1 % of the incident flux, over the range used. The spectral
and photometric characteristics of the light source and photometer are kept
constant during measurements.
ii) The light source and its associated optical system produce a parallel light beam,
no ray of which makes an angle of more than 0,05 rad (3°) with the beam axis.
This beam is not vignetted at either port of the integrating sphere.
iii) The design of the instrument is such that the reading is zero in the absence of the
light beam.
iv) The integrating sphere used to collect the transmitted light may be of any diameter
(but preferabl
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