IEC TR 62977-1-31:2021

IEC TR 62977-1-31 ®
Edition 1.0 2021-04
TECHNICAL
REPORT
colour
inside
Electronic displays –
Part 1-31: Generic – Practical information on the use of light measuring devices
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IEC TR 62977-1-31 ®
Edition 1.0 2021-04
TECHNICAL
REPORT
colour
inside
Electronic displays –
Part 1-31: Generic – Practical information on the use of light measuring devices

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120; 31.260 ISBN 978-2-8322-9716-2

– 2 – IEC TR 62977-1-31:2021 © IEC 2021
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 10
4 General information on LMDs for photometry and colorimetry . 10
4.1 General . 10
4.2 Photometry and colorimetry for electronic displays . 10
4.3 LMDs for luminance and chromaticity measurements . 11
4.3.1 Configuration of LMDs . 11
4.3.2 Input optics of LMDs . 13
4.3.3 Electronic system of LMDs . 13
4.3.4 Calibration of LMDs . 14
4.3.5 Maintenance of LMDs . 14
4.4 Setup conditions for measurement . 14
4.4.1 LMDs . 14
4.4.2 DUTs . 14
4.4.3 Environment . 14
5 Influence of LMD properties on luminance and chromaticity measurements . 14
5.1 General . 14
5.2 Repeatability . 15
5.2.1 General . 15
5.2.2 Example of the repeatability of an LMD. 15
5.3 Accuracy . 16
5.3.1 General . 16
5.3.2 Example of the accuracy of an LMD . 16
5.3.3 Linearity . 16
5.3.4 Range change . 17
5.4 Luminance range . 17
5.5 Spectral properties of the spectroradiometer . 17
5.5.1 General . 17
5.5.2 Wavelength accuracy and spectral bandwidth . 17
5.6 Spectral properties of the filter-type luminance meter and colorimeter . 23
5.6.1 General . 23
5.6.2 Spectral responsivity . 23
5.6.3 Methods to reduce the measurement difference . 25
5.7 Angular response of LMDs . 26
5.7.1 General . 26
5.7.2 Subtended angles . 26
5.7.3 Consideration of the input optics . 27
5.8 Measurement field . 28
5.8.1 General . 28
5.8.2 Number of pixels within the measurement field . 29
5.9 Polarization . 29

5.9.1 General . 29
5.9.2 Polarization dependence of LMDs. 30
5.10 Temporal synchronization . 31
5.10.1 General . 31
5.10.2 Temporal synchronization of the LMD and DUT . 31
6 Influence of LMD properties on measurements of the optical characteristics of
electronic displays . 32
6.1 General . 32
6.2 Contrast ratio . 32
6.2.1 General . 32
6.2.2 Calculated influence of LMD properties on the contrast ratio
measurements . 32
6.3 Electro-optical transfer function (EOTF) . 35
6.3.1 General . 35
6.3.2 Calculated influence of the LMD properties on the EOTF measurements . 35
6.4 Chromaticity gamut area . 36
6.4.1 General . 36
6.4.2 Calculated influence of LMD properties on the chromaticity gamut area
measurements . 36
6.5 Viewing direction characteristics . 38
6.5.1 General . 38
6.5.2 Calculated influence of the LMD properties on the viewing direction
characteristics measurements . 38
6.5.3 Measurement field at an oblique direction . 40
6.6 Spatial uniformity . 41
6.6.1 General . 41
6.6.2 Calculated influence of LMD properties on uniformity and non-uniformity

measurements . 41
6.7 Response time . 43
6.7.1 General . 43
6.7.2 Measurement of the response time . 43
6.8 Flicker . 46
6.8.1 General . 46
6.8.2 Measurement method of the flicker . 46
6.8.3 Low-pass filter of LMDs . 47
Annex A (informative) Photometry and colorimetry . 49
A.1 General . 49
A.2 Photometry . 49
A.3 Colorimetry . 49
A.3.1 General . 49
A.3.2 Standard colorimetric observer . 50
A.3.3 Tristimulus values . 50
A.3.4 Chromaticity diagram and colour space . 50
Annex B (informative) Method for reducing the measurement difference of
colorimeters . 53
B.1 General . 53
B.2 Matrix calibration methods for colorimeters . 53
B.2.1 Matrix calibration process 1: RGB calibration . 53
B.2.2 Matrix calibration process 2: RGBW calibration . 54

– 4 – IEC TR 62977-1-31:2021 © IEC 2021
Annex C (informative) Input data in Clause 5 and Clause 6, and calculation methods
in 5.8 and 6.5 . 56
C.1 General . 56
C.2 Characteristics of DUTs . 56
C.2.1 Spectral radiances of the DUTs . 56
C.2.2 Directional characteristic of the DUT . 57
C.2.3 Temporal modulation characteristics of the DUT . 57
C.2.4 EOTF characteristics of the DUTs . 57
C.2.5 Uniformity characteristics of the DUTs . 58
C.3 Characteristics of the filter-type LMDs . 59
C.3.1 Spectral responsivities of the filter-type LMDs . 59
C.3.2 Specifications of filter-type LMDs . 61
C.4 Influence of the number of pixels within the measurement field . 63
C.5 Validity of the viewing direction dependence obtained by a simplified method . 64
Annex D (informative) Instabilities of DUTs in measurement . 66
D.1 General . 66
D.2 DUT instabilities . 66
Bibliography . 68

Figure 1 – Block diagrams of three types of LMDs . 12
Figure 2 – Example of configurations for the input optics and detector . 12
Figure 3 – Example of input optics for the luminance meters . 13
Figure 4 – Block diagram of a typical electronic system . 13
Figure 5 – Examples of the repeatability of an LMD as a function of luminance . 15
Figure 6 – Examples of the accuracy of an LMD as a function of luminance . 16
Figure 7 – Calculated relative luminance difference as a function of wavelength error . 19
Figure 8 – Calculated relative luminance difference as a function of spectral bandwidth . 20
Figure 9 – Calculated chromaticity differences as a function of wavelength error . 21
Figure 10 – Calculated chromaticity differences as a function of spectral bandwidth . 22
'
Figure 11 – Calculated relative luminance difference as a function of f . 24
'
Figure 12 – Calculated chromaticity differences as a function of f . 25
1 , xyz
Figure 13 – Angular aperture and measurement field angle . 27
Figure 14 – Calculated relative luminance difference and chromaticity difference as a
function of the angular aperture . 27
Figure 15 – Diagram of light rays in object space telecentric and non-telecentric optical
design . 28
Figure 16 – Calculated chromaticity difference as a function of the number of pixels . 29
Figure 17 – Measured luminance variation as a function of the rotation angle of the
polarizer . 30
Figure 18 – Calculated relative luminance differences as a function of sampling period . 32
Figure 19 – Total measurement times for 0,3 % repeatability (2σ) in three LMDs . 36
Figure 20 – Calculated relative difference, ΔGA , by spectroradiometers . 37
xy
Figure 21 – Calculated relative difference, ΔGA , by colorimeters . 38
xy
Figure 22 – Cone of light rays for calculating the tristimulus values measured by an
LMD with the angular aperture, α, and an optical axis at an inclination angle, θ . 39
LMD
Figure 23 – Calculated luminance and chromaticity dependence as a function of the
inclination angle for the 2°, 6°, and 10° angular apertures . 40
Figure 24 – Measurement field and test pattern . 41
Figure 25 – Calculated non-uniformity difference by the filter-type colorimeters . 43
Figure 26 – Measurement setups for response time measurements . 44
Figure 27 – Response curves measured at different sampling rates . 44
Figure 28 – Measured response subjected to various low-pass filterings . 45
Figure 29 – Measured response curves switched from the 10 % to 90 % level . 46
Figure 30 – Schematic measured temporal luminance modulation of the LCD with a

common voltage offset . 47
Figure 31 – Conceptual pseudo-temporal luminance modulation . 48
Figure 32 – Simulated luminance modulations with and without high frequency noise . 48
Figure C.1 – Spectral radiances . 56
Figure C.2 – Inclination angle dependence . 57
Figure C.3 – Temporal modulation of the luminance . 57
Figure C.4 – EOTF characteristics . 58
Figure C.5 – Spectral responsivity of the colorimeter . 61
Figure C.6 – Repeatability of three LMD models . 62
Figure C.7 – Three positions of a circular measurement field relative to the RGB
stripes . 63
Figure C.8 – Configuration to measure DUT emission by the LMD at the inclination
angle, θ . 64
LMD
Figure C.9 – Inclination angle dependence calculated by two methods using an LMD

with an angular aperture of 10° . 65
Figure D.1 – Changes of luminance and chromaticity after switching the grey levels . 66
Figure D.2 – Changes of luminance after switching from the black to grey level . 67

Table 1 – DUT characteristics for the calculations . 33
Table 2 – Calculated results of the contrast ratio by three LMDs . 34
Table 3 – Calculated durations of the EOTF measurements . 36
Table 4 – Chromaticity gamut area of three DUTs . 37
Table 5 – Non-uniformity of DUTs . 42
Table 6 – Rise times calculated from a measured response subjected to various low-
pass filterings . 45
Table 7 – Rise times measured by LMDs of various V(λ) fidelities . 46
Table C.1 – Measured luminance and chromaticity at the nine positions of DUT-1 . 58
Table C.2 – Measured luminance and chromaticity at the nine positions of DUT-2 . 59
Table C.3 – Specifications of filter-type LMDs . 62
Table D.1 – Luminance and chromaticity transition . 66
Table D.2 – Luminance changes in two measurements . 67

– 6 – IEC TR 62977-1-31:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRONIC DISPLAYS –
Part 1-31: Generic –
Practical information on the use of light measuring devices

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
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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.
IEC TR 62977-1-31 has been prepared by IEC technical committee 110: Electronic displays. It
is a Technical Report.
The text of this Technical Report is based on the following documents:
DTR Report on voting
110/1258/DTR 110/1281A/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 62977 series, published under the general title Electronic displays,
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.
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.

– 8 – IEC TR 62977-1-31:2021 © IEC 2021
INTRODUCTION
Measurements of the optical characteristics of electronic displays are primarily affected by three
factors: measuring procedures, displays (devices under test: DUTs), and light measuring
devices (LMDs), for which there are many international standards supporting consistent and
comparable measurements. Most of them, however, provide only limited information on LMDs,
making it difficult to appropriately select and use the LMD for the measurement objective. The
purpose of this document is to provide best practices and suggestions which are missing in the
standards.
This document addresses how the major properties of a typical LMD affect the measurement
results. It is often impractical and unnecessary to consider the influences of all properties of
LMDs and all characteristics of DUTs as well as their interactions and influences on the
measurement results. Therefore, the multiple interaction effects that exist are beyond the scope
of this document. Due to the rapid innovation and abundance of LMDs, covering all types of
LMDs is also outside the objectives of this document.

ELECTRONIC DISPLAYS –
Part 1-31: Generic –
Practical information on the use of light measuring devices

1 Scope
This part of IEC 62977 provides practical information on light measuring devices (luminance
meters, colorimeters, and spectroradiometers) with luminance measuring optics for the
characterization of electronic displays.
2 Normative references
There are no normative references in this document.
3 Terms, definitions, and abbreviated terms
3.1 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:
• ISO Online browsing platform: available at http://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
NOTE CIE Electronic international lighting vocabulary (e-ILV) is also available at http://cie.co.at/e-ilv.
3.1.1
repeatability
closeness of agreement between indications or measured quantity values
obtained by replicated measurements over a short period of time using a specific LMD under
conditions specified by the LMD manufacturer
Note 1 to entry: Repeatability of an LMD is usually expressed numerically by statistical quantities, such as standard
deviation, variance, or coefficient of variation (relative standard deviation) under the specified conditions of
measurement.
Note 2 to entry: The influence on measurement repeatability caused by fluctuations of the measured light source and
by the measurement procedure is assumed to be negligible when the manufacturer specifies the repeatability of an
LMD. Manufacturers often specify the type of light source and measurement conditions used for determining the
repeatability of an LMD.
Note 3 to entry: Measurement precision is the closeness of agreement between indications or measured quantity
values obtained by replicate measurements on the same or similar objects under specified conditions. Measurement
repeatability is measurement precision under a set of repeatability conditions of measurement that includes the same
measurement procedures, same operators, same measuring system, same operating conditions, same location, and
replicate measurements on the same or similar objects over a short period of time. Measurement reproducibility is
measurement precision under a set of reproducibility conditions of measurement that includes different locations,
operators, measuring systems, and replicate measurements on the same or similar objects [1], [2] .
____________
Numbers in square brackets refer to the Bibliography.

– 10 – IEC TR 62977-1-31:2021 © IEC 2021
3.1.2
accuracy
difference between a measured quantity value and an accepted reference value
when using a specific LMD under conditions specified by the LMD manufacturer
Note 1 to entry: This term is a quantity with a numerical value and is usually expressed as a range specification.
Note 2 to entry: The accepted reference value is a value that serves as an agreed-upon reference for comparison,
and which is derived as:
a) a theoretical or established value, based on scientific principles;
b) an assigned or certified value, based on experimental work of some national or international organization;
c) a consensus or certified value, based on collaborative experimental work under the auspices of a scientific or
engineering group;
d) (when a), b) and c) are not available) the expectation of the (measurable) quantity, i.e. the mean of a specified
population of measurements [3].
Note 3 to entry: The influence on measurement accuracy caused by fluctuations of the measured light source and by
the measurement procedure is assumed to be negligible when the manufacturer specifies the accuracy of an LMD.
Manufacturers often specify the type of light source and other measurement conditions used for determining the
accuracy of an LMD.
Note 4 to entry: Measurement accuracy is the closeness of agreement between a measured quantity value and the
true quantity value of a measurand [1], [2]. The accuracy of measurement is not a quantity value while the accuracy
of an LMD is a quantity value; thus, the term "accuracy" conventionally used for the specification of LMDs means
something different than that used for measurement.
3.2 Abbreviated terms
CIE Commission Internationale de l’Éclairage (International Commission on Illumination)
CMF colour-matching function
DUT device under test
EOTF electro-optical transfer function
LCD liquid crystal display
LED light emitting diode
LMD light measuring device
ND neutral density
OLED organic light emitting diode
PWM pulse width modulation
RGB red, green, and blue
RGBW red, green, blue, and white
Vsync vertical synchronizing signal
4 General information on LMDs for photometry and colorimetry
4.1 General
Clause 4 describes the principles of photometry and colorimetry, configuration, calibration, and
maintenance of LMDs, as well as setup conditions for measurement.
4.2 Photometry and colorimetry for electronic displays
Photometry is the measurement of quantities referring to radiation as evaluated according to a
given spectral luminous efficiency (see IEV 845-25-013). Colorimetry is the measurement of
colour stimuli based on a set of conventions (see IEV 845-25-014). Details on the calculation
formulae and specific conditions applied to electronic display measurement are shown in
Annex A.
4.3 LMDs for luminance and chromaticity measurements
4.3.1 Configuration of LMDs
The configurations of three types of LMDs are described as follows:
1) Luminance meter
A luminance meter is an instrument for measuring luminance (see IEV 845-25-021). A block
diagram of the setup of a typical luminance meter is shown in Figure 1a): it consists of input
optics, a detector unit for measuring the luminance, L , and an electronic system. An
v
example of the configuration of the input optics and the detector unit is shown in Figure 2a),
where a lens is used for the input optics. The input optics collects the light emitted from the
DUT and converges it onto the detector. An optical compensation filter is arranged in front
of the detector. The combination of the spectral characteristics of the filter, input optics, and
detector approximates the spectral luminous efficiency function, V(λ). A neutral density (ND)
filter can be inserted into the optical path, for example when the LMD's dynamic range is
insufficient and results in detector saturation. The detector receives the light and converts
the optical signal to an electronic one, from which the electronic system calculates the
luminance, L , as in [4], indicates it on an instrument display, and/or sends the result to an
v
external system.
2) Colorimeter
A colorimeter is an instrument for measuring colorimetric quantities, such as the tristimulus
values of a colour stimulus (see IEV 845-25-022). A block diagram of the most common
setup for a colorimeter is shown in Figure 1b): it is conceptually similar to a luminance meter.
A colorimeter has a detector unit for measuring the tristimulus values instead of one for the
luminance. A colorimeter for both luminance and chromaticity measurements employs the
same type of input optics as the luminance meter, as described in 4.3.1 1). An example of
the configuration of the input optics and the detector unit is shown in Figure 2b), where the
detector unit has three pairs of optical compensation filters and detectors. The input optics
is connected to the detector unit by a three-branch optical fibre. The combined spectral
characteristics of those components approximates the CIE colour-matching functions
(CMFs). The electronic system calculates the tristimulus values, X, Y, and Z, where Y is
practically identical to L (see Annex A).
v
3) Spectroradiometer
A spectroradiometer is an instrument for measuring radiometric quantities in narrow
wavelength intervals over a given spectral region (see IEV 845-25-007). A block diagram of
the general setup of a spectroradiometer is shown in Figure 1c). A spectroradiometer for
spectral radiance measurements, and luminance and chromaticity calculations therefrom,
employs the same type of input optics as the luminance meter, as described in 4.3.1 1). An
example of the configuration of the input optics and the spectrometer is shown in Figure 2c),
where the input optics is connected to the spectrometer by an optical fibre. The example
spectrometer consists of an input slit, a grating, for example a concave grating [5], and an
array detector, where the output of the detector is related to the spectral radiance of the
DUT. The obtained spectral radiance, L (λ), is converted to the luminance, L , or tristimulus,
e v
values, X, Y, and Z, using V(λ) or CMFs data, which are often stored in look-up tables [6],
[7].
– 12 – IEC TR 62977-1-31:2021 © IEC 2021

a) Luminance meter b) Colorimeter

c) Spectroradiometer
Figure 1 – Block diagrams of three types of LMDs

a) Luminance meter b) Colorimeter

c) Spectroradiometer with spectrometer using grating and array detector

Figure 2 – Example of configurations for the input optics and detector

4.3.2 Input optics of LMDs
An LMD has an input optics system which collects the light emitted or reflected from a DUT.
There are various types of imaging as well as non-imaging input optics, for example fixed-focus
lens, variable-focus lens, and optical fibre. For luminance measurements, imaging optics is
often used. Figure 3 shows an example of the input optics with an imaging lens, an aperture
stop (aperture), a field stop, and a detector behind the field stop, together with the DUT and
detector. Related optical properties are described in the following sentences. The aperture stop
is an opening that defines the area over which the average optical emission is measured (see
IEV 845-25-086). The entrance pupil is a virtual image of the aperture stop as viewed from the
object space, and its position and size depend on the measurement distance. The angular
aperture is the angle subtended by the entrance pupil. The field stop which is positioned on the
image plane limits the measurement field of the DUT. The measurement field angle is the angle
subtended by the measurement field at the entrance pupil.

Figure 3 – Example of input optics for the luminance meters
4.3.3 Electronic system of LMDs
An LMD has an electronic system for processing the electronic signal from the detector [8] in
order to deliver the measured values. Among the various types of systems, Figure 4 shows a
typical one consisting of an analogue circuit amplifying the signal from the detector, an A/D
converter converting the amplified signal into a digital signal, a data processor converting the
digital signal to the measurement value, and a system controller controlling the whole system
including the memory, display, and interface of the external devices.

Figure 4 – Block diagram of a typical electronic system

– 14 – IEC TR 62977-1-31:2021 © IEC 2021
4.3.4 Calibration of LMDs
Luminance meters and colorimeters are usually calibrated to a reference source with a light
source and a plane diffuser, which are traceable to a national standard recognized by a national
authority as the basis for assigning quantity values to other measurement standards [1], [2].
These light sources are often incandescent lamps, for example tungsten-halogen lamps,
designed to approximate the CIE standard Illuminant A. It is sometimes possible to use other
types of light sources, for example LEDs, for LMDs specifically designed for display
measurement. For a spectroradiometer, the wavelengths are usually calibrated to a light source
emitting one or more line spectra, and the spectral radiance is calibrated to the reference source
described above [9]. The temporal stability of these light sources is strictly managed by
manufacturers to meet their specifications.
4.3.5 Maintenance of LMDs
The performance of LMDs depends on ambient conditions, especially temperature and humidity.
Careful storage, handling, and operation of LMDs are recommended in accordance with
instructions provided by the manufacturer. Since deterioration caused by ageing is inevitable,
periodic inspections, adjustments, and calibration by the manufacturer are recommended.
4.4 Setup conditions for measurement
4.4.1 LMDs
Most LMDs are unstable immediately after switching the power on, and they therefore need
some warm-up time to achieve their specified accuracy and repeatability. Most optical
instabilities are due to thermal effects and thus have a long time constant. Checking the
measurement stability before regular measurements is recommended in order to verify the
appropriate warm-up time.
4.4.2 DUTs
Short-term instabilities in the optical output of DUTs are often caused by their electronic system
while long-term instabilities are mostly caused by thermal effects which can have long time
constants. Measured instabilities of DUTs are exemplified in Annex D. Checking for such DUT
instabilities is recommended in order to adapt the measurement procedure accordingly. The
combined long-term stability of the LMD and DUT can be confirmed by comparing the results
measured with the same settings at the beginning and at the end of the measurement session.
4.4.3 Environment
For consistent and comparable measurements, environmental conditions should meet the
requirements of the LMDs and DUTs. Carefully checking the environmental conditions
described in the respective instruction manuals before measurement is recommended.
5 Influence of LMD properties on luminance and chromaticity measurements
5.1 General
Clause 5 describes the LMD properties disclosed by the manufacturer or required by the display
measurement standards, and their influence on the luminance and chromaticity measurement
results. This information is helpful for the selection and use of the LMD suitable for the
measurement objectives [10]. Some input data for calculations are shown in Annex C.

5.2 Repeatability
5.2.1 General
Repeatability of an LMD
...