IEC 62679-3-3:2016

Electronic paper displays - Part 3-3: Optical measuring methods for displays with integrated lighting units

IEC 62679-3-3:2016(E) specifies the standard measurement conditions and measurement methods for determining the optical performance of electronic paper display (EPD) devices which have an operating integrated lighting unit (such as a front light). The scope of this document is restricted to EPDs using segmented or matrix structures with either monochromatic or colour type displays. The measurement methods are intended for EPDs operated in a reflective mode with the integrated lighting unit (ILU) turned on in a dark or indoor ambient lighting environment. Colour systems beyond three primaries are not covered in this document.

General Information

• Status: Published
• Publication Date: 05-Sep-2016
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 17.220.01 - Electricity. Magnetism. General aspects
• ICS: 31.120 - Electronic display devices
• ICS: 31.260 - Optoelectronics. Laser equipment
• Technical Committee: TC 110 - Electronic displays
• Drafting Committee: WG 7 - TC 110/WG 7
• Current Stage: PPUB - Publication issued
• Start Date: 15-Dec-2016
• Completion Date: 06-Sep-2016

Standards Content (Sample)

IEC 62679-3-3
®

Edition 1.0 2016-09
INTERNATIONAL
STANDARD

colour
inside


Electronic paper displays –
Part 3-3: Optical measuring methods for displays with integrated lighting units
IEC 62679-3-3:2016-09(en)

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IEC 62679-3-3

®


Edition 1.0 2016-09




INTERNATIONAL



STANDARD









colour

inside










Electronic paper displays –

Part 3-3: Optical measuring methods for displays with integrated lighting units



























INTERNATIONAL

ELECTROTECHNICAL


COMMISSION





ICS 31.120; 31.260 ISBN 978-2-8322-3616-1



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


® Registered trademark of the International Electrotechnical Commission

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CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms, definitions and abbreviated terms . 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 8
4 Standard measuring conditions . 8
4.1 Standard environmental measuring conditions . 8
4.2 Viewing direction coordinate system . 8
4.3 Standard lighting conditions . 9
4.3.1 General comments and remarks on the measurement of electronic
paper displays . 9
4.3.2 Dark room conditions . 9
4.3.3 Standard indoor ambient illumination spectra . 9
4.3.4 Standard illumination geometries . 10
4.4 Adjustment of the EPD . 11
4.5 Standard conditions of measuring equipment . 11
4.6 Working standards and references . 11
4.7 Standard locations of measurement field . 11
4.7.1 Matrix displays . 11
4.7.2 Segment displays . 12
5 Optical measuring methods . 12
5.1 Reflection measurements . 12
5.1.1 General . 12
5.1.2 Measuring conditions . 12
5.1.3 Measuring the hemispherical diffuse reflectance . 13
5.1.4 Measuring the reflectance factor for a directed light source . 15
5.2 Display photometric uniformity in a dark room . 16
5.2.1 Purpose . 16
5.2.2 Measuring equipment . 16
5.2.3 Measurement method . 16
5.2.4 Definitions and evaluations. 17
5.3 Dark room contrast ratio . 17
5.3.1 Purpose . 17
5.3.2 Measuring equipment . 17
5.3.3 Measurement method . 17
5.3.4 Definitions and evaluations. 17
5.4 Contrast ratio under indoor illumination . 18
5.4.1 Purpose . 18
5.4.2 Measurement conditions . 18
5.4.3 Measurement method . 18
5.5 Cross-talk . 19
5.5.1 Purpose . 19
5.5.2 Measuring equipment . 19
5.5.3 Greyscale matrix displays. 19
5.5.4 Black and white (two-level) matrix displays . 21

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IEC 62679-3-3:2016 © IEC 2016 – 3 –
5.6 Display colour, colour gamut, and colour gamut area . 22
5.6.1 Purpose . 22
5.6.2 Measuring equipment . 22
5.6.3 Measurement method . 22
5.6.4 Display colour gamut . 22
5.6.5 Display colour gamut area . 23
5.7 Display colorimetric uniformity in a dark room . 25
5.7.1 Purpose . 25
5.7.2 Measuring equipment . 25
5.7.3 Measurement method . 25
5.7.4 Definitions and evaluations. 26
5.8 Display colour under indoor illumination . 26
5.8.1 Purpose . 26
5.8.2 Measurement conditions . 26
5.8.3 Measurement method . 27
5.8.4 Definitions and evaluations. 27
5.9 Colour gamut volume under indoor illumination . 28
5.9.1 Purpose . 28
5.9.2 Measurement conditions . 28
5.9.3 Measurement method . 28
5.9.4 Definitions and evaluations. 29
5.9.5 Recording . 30
5.10 Viewing direction dependence in a dark room . 30
5.10.1 Purpose . 30
5.10.2 Measuring conditions . 31
5.10.3 Measuring method . 31
5.10.4 Definitions and evaluations. 31
Annex A (informative) Calculation method of daylight colour gamut volume . 34
A.1 Purpose . 34
A.2 Procedure for calculating the colour gamut volume . 34
A.3 Surface subdivision method for CIELAB gamut volume calculation . 36
A.3.1 Purpose . 36
A.3.2 Assumptions . 36
A.3.3 Algorithm . 36
A.3.4 Software example . 36
Bibliography . 41

Figure 1 – Representation of the coordinate system used to specify the viewing or
measurement orientation . 9
Figure 2 – Standard measurement positions . 12
Figure 3 – Window pattern for cross-talk measurement . 20
Figure 4 – Example representation of the same primary colours in the CIE 1931 (left)
and CIE 1976 (right) chromaticity diagrams . 22
Figure 5 – Example of evaluation results for the colour gamut area on the a*b* plane
of the CIELAB colour space . 25
Figure 6 – An example of the range in colours produced by an sRGB display as
represented by the CIELAB colour space . 29
Figure 7 - Example of contrast ratio dependence on viewing direction . 32

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Figure A.1 – Analysis flow chart for calculating the colour gamut volume . 34
Figure A.2 – Graphical representation of the colour gamut volume for sRGB in the
CIELAB colour space . 35

Table 1 – Eigenvalues M and M for CIE daylight Illuminant D50 . 14
1 2
Table 2 – Input signals for CIELAB and CIE UCS u’v’ colour gamut area
measurements . 24
Table 3 – Example data of in-plane colour non-uniformity . 26
Table 4 – Example of minimum colours required for gamut volume calculation of a 3-
primary 8-bit display . 29
Table 5 – Measured tristimulus values for the minimum set of colours (see Table 4)
required for gamut volume calculation under the specified indoor illumination
conditions . 30
Table 6 – Calculated white point in the darkened room and indoor ambient condition . 30
Table 7 – Colour gamut volume in the CIELAB colour space . 30
Table 8 – Example format used for recording viewing direction performance . 33
Table A.1 – Tristimulus values of the sRGB primary colours . 35
Table A.2 – Example of sRGB colour set represented in the CIELAB colour space . 35
Table A.3 – Example of an sRGB colour gamut volume in the CIELAB colour space . 36

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IEC 62679-3-3:2016 © IEC 2016 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ELECTRONIC PAPER DISPLAYS –

Part 3-3: Optical measuring methods for displays
with integrated lighting units

FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard 62679-3-3 has been prepared by IEC technical committee 110:
Electronic display devices.
The text of this standard is based on the following documents:
CDV Report on voting
110/723/CDV 110/780/RVC

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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A list of all parts in the IEC 62679 series, published under the general title Electronic paper
displays, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication 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.

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IEC 62679-3-3:2016 © IEC 2016 – 7 –
ELECTRONIC PAPER DISPLAYS –

Part 3-3: Optical measuring methods for displays
with integrated lighting units



1 Scope
This part of IEC 62679 specifies the standard measurement conditions and measurement
methods for determining the optical performance of electronic paper display (EPD) devices
which have an operating integrated lighting unit (such as a front light). The scope of this
document is restricted to EPDs using segmented or matrix structures with either
monochromatic or colour type displays. The measurement methods are intended for EPDs
operated in a reflective mode with the integrated lighting unit (ILU) turned on in a dark or
indoor ambient lighting environment. Colour systems beyond three primaries are not covered
in this document.
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 for 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 62679-1-1, Electronic paper displays – Part 1-1: Terminology
IEC 62679-3-1:2014, Electronic paper displays – Part 3-1: Optical measuring methods
IEC 61966-2-1, Multimedia systems and equipment – Colour measurement and management
– Part 2-1: Colour management – Default RGB colour space – sRGB
CIE 15, Colorimetry
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62679-1-1,
IEC 60050-845, and the following 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
3.1.1
ILU
integrated lighting unit
light source integrated into an EPD device to provide supplementary illumination to
compensate for the lack of adequate ambient illumination

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3.1.2
ambient contrast ratio
contrast ratio of a display with both hemispherical diffuse and directional illumination incident
onto its surface used to simulate real lighting environments
Note 1 to entry: In this document, the ambient contrast ratio is determined with the ILU turned on in addition to the
ambient illumination incident on the display.
3.1.3
colour gamut volume
single number corresponding to the largest possible range of display colours (including all
possible mixtures of the primaries, white W and black K), described as a volume in a three-
dimensional colour space such as CIELAB
3.2 Abbreviated terms
CCT correlated colour temperature
CIE International Commission on Illumination
CIELAB CIE 1976 (L*a*b*) colour space
DUT device under test
EPD electronic paper display
ILU integrated lighting unit (e.g. a front lightguide plate)
LMD light-measuring device
RGB red, green, blue
SID Society for Information Display
sRGB a standard RGB colour space as defined in IEC 61966-2-1
4 Standard measuring conditions
4.1 Standard environmental measuring conditions
Optical and electro-optical measurements shall be carried out under standard environmental
conditions, at a temperature of 25 °C ± 3 °C, at a relative humidity of 25 % to 85 %, and at a
pressure of 86 kPa to 106 kPa. When different environmental conditions are used, they shall
be noted in the report.
4.2 Viewing direction coordinate system
The viewing direction is the direction under which the observer looks at the point of interest
on the device under test (DUT). During the measurement, the light-measuring device (LMD)
simulates the observer, by aiming the LMD at the point of interest on the DUT from the
viewing direction. The viewing direction is defined by two angles: the angle of inclination θ
(relative to the surface normal of the DUT) and the angle of rotation φ (also called azimuth
angle) as illustrated in Figure 1. Although the azimuth angle is measured in the counter-
clockwise direction, it is related to the directions on a clock face as follows: φ = 0° is the 3
o'clock direction ("right"), φ= 90° the 12 o'clock direction ("top"), φ = 180° the 9 o'clock
direction ("left") and φ = 270° the 6 o'clock direction ("bottom").

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IEC 62679-3-3:2016 © IEC 2016 – 9 –
Z
θ
Y
12:00
φ
X
9:00 3:00
6:00

IEC
NOTE The viewing/measurement direction is specified by the angle of inclination and the angle of rotation
(azimuthal angle) in a polar coordinate system.
Figure 1 – Representation of the coordinate system used to specify
the viewing or measurement orientation
4.3 Standard lighting conditions
4.3.1 General comments and remarks on the measurement of electronic paper
displays
EPDs are often used as reflective displays, where the ambient external light reflected from the
active area is modulated. When there is insufficient external light, an ILU can be turned on to
provide an internal source of light for the optical modulation and display of information. This
document considers two cases: when the ILU is the only light source, and when it
supplements indoor ambient illumination. For these cases, an EPD with an operating ILU can
be treated as an emissive display, and any ambient lighting is a separate additive reflected
signal.
The measurement methods in this document are performed with the ILU turned on.
Subclause 4.3 describes a selection of standard lighting conditions for measuring the
performance characteristics of EPDs. EPDs may also be measured under other illumination
and detection geometries in addition to the standard geometries.
A warm-up time may be necessary for both the ILU and the illumination light source. The light
signal shall remain stable to within ±5 % over the course of the complete measurement.
4.3.2 Dark room conditions
EPDs are intended to be measured under controlled lighting conditions. Unwanted
background illumination shall be minimized, typically by illuminating the display in a dark room.
The dark room spectral radiance contribution from the background illumination, that is the
measured spectral radiance reflected off the DUT, shall be not more than 1/100 of the
spectral radiance from the device black state with the illumination source on. If this condition
is not satisfied, then background subtraction is required and it shall be noted in the report. In
addition, if the sensitivity of the LMD is inadequate to measure at these low levels, then the
lower limit of the LMD shall be noted in the report.
Unless stated otherwise, the standard background lighting conditions shall be those of the
dark room.
4.3.3 Standard indoor ambient illumination spectra
The following illumination conditions are specified for optical and electro-optical
measurements of reflective displays under indoor ambient illumination. A combination of two

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1
illumination geometries is generally used to simulate ambient indoor illumination [1, 2] .
Uniform hemispherical diffuse illumination will be used to simulate the background lighting in
a room, with any rays from luminaires or sunlight blocked from directly illuminating the screen. A
directed light source in a dark room will simulate the effect of directed illumination on a
display by a luminaire in a room.
The following illumination conditions shall be used to simulate indoor display viewing
environments:
• Uniform hemispherical diffuse illumination – Use a spectrally smooth broadband light
source to photometrically approximate CIE standard illuminant A, CIE standard
illuminant D65, or CIE illuminant D50 as defined in CIE 15. Better accuracy can be
obtained by performing spectral measurements. For spectral measurements, a
spectrally smooth broadband light source (such as an approximation to CIE standard
illuminant A) shall be used. A measurement of the spectral reflectance factor using a
broad light source (such as illuminant A) enables the indoor photopic and colour
characteristics to be calculated later for the desired reference spectra (for example
CIE illuminant D65). The performance characteristics shall be calculated using 300 lx
for an indoor reading environment [3]. The actual hemispherical diffuse reflectance
factor measurement may require higher illumination levels for better measurement
accuracy. The results
...