IEC 62341-6-2:2012

IEC 62341-6-2 ®
Edition 1.0 2012-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Organic light emitting diode (OLED) displays –
Part 6-2: Measuring methods of visual quality and ambient performance

Afficheurs à diodes électroluminescentes organiques (OLED) –
Partie 6-2: Méthodes de mesure de la qualité visuelle et des caractéristiques de
fonctionnement sous conditions ambiantes

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IEC 62341-6-2 ®
Edition 1.0 2012-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Organic light emitting diode (OLED) displays –

Part 6-2: Measuring methods of visual quality and ambient performance

Afficheurs à diodes électroluminescentes organiques (OLED) –

Partie 6-2: Méthodes de mesure de la qualité visuelle et des caractéristiques de

fonctionnement sous conditions ambiantes

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX X
ICS 31.260 ISBN 978-2-88912-893-8

– 2 – 62341-6-2 © IEC:2012
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviations . 6
3.1 Terms and definitions . 6
3.2 Abbreviations . 9
4 Structure of measuring equipment . 9
5 Standard measuring conditions . 9
5.1 Standard measuring environmental conditions . 9
5.2 Standard lighting conditions . 10
5.2.1 Dark-room conditions . 10
5.2.2 Ambient illumination conditions . 10
5.3 Standard setup conditions . 15
5.3.1 General . 15
5.3.2 Adjustment of OLED display modules . 15
5.3.3 Starting conditions of measurements . 16
5.3.4 Conditions of measuring equipment . 16
6 Visual inspection of static images . 17
6.1 General . 17
6.2 Classification of visible defects . 17
6.2.1 Classification scheme . 17
6.2.2 Reference examples for subpixel defects . 17
6.2.3 Reference example for line defects . 19
6.2.4 Reference example for mura defects . 19
6.3 Visual inspection method and criteria . 20
6.3.1 Standard inspection conditions . 20
6.3.2 Standard inspection method . 21
6.3.3 Inspection criteria . 23
7 Electro-optical measuring methods under ambient illumination . 24
7.1 Reflection measurements . 24
7.1.1 Purpose . 24
7.1.2 Measuring conditions . 24
7.1.3 Measuring the hemispherical diffuse reflectance factor . 25
7.1.4 Measuring the reflectance factor for a directed light source . 27
7.2 Ambient contrast ratio . 29
7.2.1 Purpose . 29
7.2.2 Measuring conditions . 29
7.2.3 Measuring method . 30
7.3 Ambient display colour . 30
7.3.1 Purpose . 30
7.3.2 Measuring conditions . 30
7.3.3 Measuring method . 30
7.4 Ambient colour gamut volume . 31
7.4.1 Purpose . 31
7.4.2 Measuring conditions . 32
7.4.3 Measuring method . 32

62341-6-2 © IEC:2012 – 3 –
7.4.4 Reporting . 33
Annex A (informative)  Measuring relative photoluminescence contribution from
displays . 35
Annex B (informative) Calculation method of ambient colour gamut volume . 38
Bibliography . 44

Figure 1 – Example of visual inspection room setup for control of ambient room
lighting and reflections . 10
Figure 2 – Example of measurement geometries for diffuse illumination condition
using an integrating sphere and sampling sphere . 13
Figure 3 – Directional source measurement geometry using an isolated source . 15
Figure 4 – Directional source measurement geometry using a ring light source . 15
Figure 5 – Layout diagram of measurement set up . 16
Figure 6 – Classification of visible defects . 17
Figure 7 – Bright subpixel defects . 18
Figure 8 – Criteria for classifying bright and dark subpixel defects . 19
Figure 9 – Bright and dark line defects . 19
Figure 10 – Sample image of line mura defect associated with TFT non-uniformity . 20
Figure 11 – Example of spot mura defect in a grey background . 20
Figure 12 – Setup condition for visual inspection of electro-optical visual defects . 22
Figure 13 – Shape of scratch and dent defect . 24
Figure 14 – An example of range in colours produced by a given display as
represented by the CIELAB colour space . 33
Figure A.1 – Scaled bi-spectral photoluminescence response from a display . 36
Figure A.2 – Decomposed bi-spectral photoluminescence response from a display . 36
Figure B.1 – Analysis flow chart for calculating the colour gamut volume . 38
Figure B.2 – Graphical representation of the colour gamut volume for sRGB in the
CIELAB colour space . 39

Table 1 – Definitions for type of scratch and dent defects . 24
Table 2 – Eigenvalues M and M for CIE Daylight Illuminants D50 and D75 . 26
1 2
Table 3 – Example of minimum colours required for gamut volume calculation of a 3-
primary 8-bit display . 32
Table 4 – Measured tristimulus values for the minimum set of colours (see Table 3)
required for gamut volume calculation under the specified ambient illumination
condition . 34
Table 5 – Calculated white point in the darkened room and ambient condition . 34
Table 6 – Colour gamut volume in the CIELAB colour space . 34
Table B.1 – Tristimulus values of the sRGB primary colours . 39
Table B.2 – Example of sRGB colour set represented in the CIELAB colour space . 39
Table B.3 – Example of sRGB colour gamut volume in the CIELAB colour space . 40

– 4 – 62341-6-2 © IEC:2012
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS –

Part 6-2: Measuring methods of visual quality and ambient performance

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 co-operation on all questions concerning standardization in the electrical and electronic fields. To
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
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.
International Standard IEC 62341-6-2 has been prepared by IEC technical committee 110:
Electronic display devices.
The text of this standard is based on the following documents:
FDIS Report on voting
110/338/FDIS 110/353/RVD
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.
A list of all parts of the IEC 62341 series, published under the general title Organic light
emitting diode (OLED) displays, can be found on the IEC website.

62341-6-2 © IEC:2012 – 5 –
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site 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.
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.
– 6 – 62341-6-2 © IEC:2012
ORGANIC LIGHT EMITTING DIODE (OLED) DISPLAYS –

Part 6-2: Measuring methods of visual quality and ambient performance

1 Scope
This part of IEC 62341 specifies the standard measurement conditions and measurement
methods for determining the visual quality and ambient performance of organic light-emitting
diode (OLED) display modules and panels. This document mainly applies to colour display
modules.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050 (all parts), International Electrotechnical Vocabulary
(available at )
IEC 60081, Double-capped fluorescent lamps – Performance specifications
IEC 61966-2-1, Multimedia systems and equipment – Colour measurement and management
– Part 2-1: Colour management – Default RGB colour space – sRGB
IEC 62341-1-2, Organic light emitting diode displays – Part 1-2: Terminology and letter
symbols
CIE 15:2004, Colorimetry
3 Terms, definitions and abbreviations
For the purposes of this document, the terms, definitions and abbreviations given in
IEC 62341-1-2 and IEC 60050-845:1987 as well as the following apply.
3.1 Terms and definitions
3.1.1
visual inspection
a means for checking image quality by human visual observation for classification and
comparison against limit sample criteria
3.1.2
subpixel defect
for colour displays, all or part of a single subpixel, the minimum colour element, which is
visibly brighter or darker than surrounding subpixels of the same colour. They are classified
depending on the number and configuration of multiple subpixel defects within a region of the
display
62341-6-2 © IEC:2012 – 7 –
3.1.3
dot defect
for monochromatic displays, all or part of a single subpixel, the minimum dot element, which
is visibly brighter or darker than surrounding dots. They are classified depending on the
number and configuration of multiple subpixel defects within a region of the display
3.1.4
bright subpixel defect
subpixels or dots which are visibly brighter than surrounding subpixels of the same colour
when addressed with a uniform dark or grey background
3.1.5
dark subpixel defect
subpixels or dots are visibly darker than surrounding subpixels of the same colour when
addressed with a uniform bright background (e.g. > 50 % full screen luminance)
3.1.6
partial subpixel defect
subpixel or dot with part of the emission area obscured such that a visible difference in
brightness is observed in comparison with neighbouring subpixels of the same colour
3.1.7
clustered subpixel defects
subpixel or dot defects gathered in specified area or within a specified distance. Also known
as “close subpixel defect”
3.1.8
unstable subpixel
subpixel or dot that changes luminance in an uncontrollable way
3.1.9
pixel shrinkage
reduction in the active emissive area of one or more subpixels (or dots) over time
3.1.10
panel edge shrinkage
reduction in the active emissive area from the edges of the display area over time
3.1.11
line defect
vertical or horizontal bright or dark line parallel to a row or column observed against a dark or
bright background, respectively
3.1.12
bright line defect
a line appearing bright on a screen displaying a uniform dark or grey pattern
3.1.13
dark line defect
a line appearing dark when displayed with a uniform bright or grey pattern
3.1.14
mura
region(s) of luminance and colour non-uniformity that generally vary more gradually than
subpixel level defects. For classification, the maximum dimension should be less than one
fourth of the display width or height

– 8 – 62341-6-2 © IEC:2012
3.1.15
line mura
variation in luminance consisting of one or more lines extending horizontally or vertically
across all or a portion of the display (such as may be caused by TFT threshold voltage
variation from laser induced crystallization)
3.1.16
colour mura
mura that appears primarily in only one colour channel and results in a local variation of the
white point (or CCT)
3.1.17
spot mura
region of luminance variation larger than a single pixel appearing as a localized slightly darker
or brighter region with a smoothly varying edge
3.1.18
stain mura
region of luminance variation larger than a single pixel appearing as clearly defined edge
bordering a region of brighter or darker luminance than surrounding regions
3.1.19
mechanical defects
image artefacts arising from defects in protective and contrast enhancement films, coatings,
mechanical fixturing, or other elements within in the active area of the display
3.1.20
scratch defect
defect appearing as fine single or multiple lines or scratches, generally light in appearance on
a dark background, and independent of display state
3.1.21
dent defect
localized spot generally white or grey in appearance on dark background and independent of
display state
3.1.22
foreign material
defect caused by foreign material like dust or thread in between contrast enhancement films,
protective films, or on emitting surface within the active area of the display
3.1.23
bubble
defect caused by a cavity in or between sealing materials, adhesives, contrast enhancement
films, protective films, or any other films within the visible area of the display
3.1.24
ambient contrast ratio
contrast ratio of a display with external natural or artificial illumination incident onto its surface
NOTE Includes indoor illumination from luminaires, or outdoor daylight illumination.
3.1.25
colour gamut boundary
surface determined by a colour gamut's extremes

62341-6-2 © IEC:2012 – 9 –
3.1.26
colour gamut volume
a single number for characterizing the colour response of a display device in a three-
dimensional colour space
NOTE Typically the colour gamut volume is calculated in the CIELAB colour space.
3.1.27
ambient colour gamut volume
number for characterizing the colour response of a display device, under a defined ambient
illumination condition, in a three-dimensional colour space
NOTE Typically the colour gamut volume is calculated in the CIELAB colour space.
3.2 Abbreviations
CCT correlated colour temperature
CIE International Commission on Illumination (Commission internationale de
l’éclairage)
CIELAB CIE 1976 (L*a*b*) colour space
DUT device under test
HD high definition
ISO International Organization for Standardization
LED light emitting diode
LMD light measuring device
LTPS low temperature polysilicon
OLED organic light emitting diode
PL  photoluminescence
QVGA quarter video graphics array
RGB red, green, blue
SDCM standard deviation of colour matching
sRGB a standard RGB colour space as defined in IEC 61966-2-1
TFT thin film transistor
TV  television
UV ultraviolet
4 Structure of measuring equipment
The system diagrams and/or operating conditions of the measuring equipment shall comply
with the structure specified in each item.
5 Standard measuring conditions
5.1 Standard measuring environmental conditions
Electro-optical measurements and visual inspection shall be carried out under the standard
environmental conditions, using at a temperature of 25 ºC ± 3 ºC, a relative humidity of 25 %
to 85 %, and pressure of 86 kPa to 106 kPa. When different environmental conditions are
used, they shall be noted in the visual inspection or ambient performance report.

– 10 – 62341-6-2 © IEC:2012
5.2 Standard lighting conditions
5.2.1 Dark-room conditions
The luminance contribution from the background illumination reflected off the test display

shall be ≤ 0,01 cd/m or less than 1/20 the display’s black state luminance, whichever is lower.
If these conditions are not satisfied, then background subtraction is required and it shall be
noted in the ambient performance 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 ambient performance report.
NOTE Unless stated otherwise, the standard lighting conditions shall be the dark-room conditions.
5.2.2 Ambient illumination conditions
5.2.2.1 Ambient illumination conditions for visual inspection
Ambient lighting conditions have a strong impact on the ability of the inspector to resolve
defects and large variations of light intensity in the visual field can lead to inspector fatigue
and a resulting loss of sensitivity to defects. Refer to ISO 9241-310 for general guidance on
optimal illumination conditions for visual inspection of pixel defects [1] .
For inspector comfort and consistency of inspection conditions an average ambient
illuminance of between 50 lx and 150 lx is suggested in the inspector’s work area. This
ambient illuminance may be measured, for example, with an illuminance meter facing directly
upward in a horizontal plane at the approximate eye level of the inspector. Care shall be
taken to use diffuse illumination, and diffuse textures in the inspection environment, to avoid
glare in the visual field of the inspector.
As shown in Figure 1, the display under test shall be placed to avoid direct illumination from
ambient room light sources. In addition, dark light-absorbing materials shall be used to cover
specular surfaces that may be viewed by the inspector in direct reflection from the display
surface. In any case, to limit degradation of the display contrast from ambient light, the
ambient illuminance incident from room light sources on the display surface measured with
the display off shall be < 20 lx. If ambient illuminance at the display surface is > 20 lx, it shall
be noted in the visual inspection report.

No directional No directional
Diffuse light source
sources sources
Baffle
Dark, light-
or
Walls or room absorbing
light shield
furnishings material
Inspector
Display device
IEC  84/12
Figure 1 – Example of visual inspection room setup
for control of ambient room lighting and reflections
—————————
Numbers in square brackets refer to the Bibliography.

62341-6-2 © IEC:2012 – 11 –
5.2.2.2 Ambient illumination conditions for electro-optical measurements
The following illumination conditions are prescribed for electro-optical measurements of
displays in ambient indoor or outdoor illumination conditions. Ambient indoor room
illumination, and outdoor illumination of clear sky daylight, on a display shall be approximated
by the combination of two illumination geometries [ 2 ]. Uniform hemispherical diffuse
illumination will be used to simulate the background lighting in a room, or the hemispherical
skylight incident on the display, with sun occluded. A directed source in a dark room will
simulate the effect of directional illumination on a display by a luminaire in a room, or from
direct sunlight.
Some displays can emit photoluminescence (PL) when exposed to certain light. The relative
impact of PL on the reflection measurement can be determined, and is described in Annex A.
An illumination condition that causes a significant reflection measurement error due to the
presence of PL should be treated carefully. If the same illumination spectral distribution and
illumination/detection geometry is used for the reflection measurements, and the calculation
of ambient contrast ratio and colour, then the PL can be incorporated into the reflection
coefficients. However, if the illumination spectra used in the calculations is significantly
different, then the reflected component must be measured separately from the PL component.
The latter case is not addressed in this document.
The following illumination conditions shall be used to simulate indoor and outdoor display
viewing environments:
Indoor room illumination conditions:
• Uniform hemispherical diffuse illumination – Use a light source closely approximating CIE
Standard Illuminant A, CIE Standard Illuminant D65, or fluorescent lamp FL1 as defined in
CIE 15. The use of an infrared-blocking filter is also recommended to minimize sample
heating from the illuminants. The UV region (< 380 nm) of all light sources shall be cut off.
If FL1 is used as a light source, the chromaticity tolerance area of the lamp shall be less
than 5 standard deviation of colour matching (SDCM, see IEC 60081). The fluorescent
lamp shall be stabilized, for example, by ageing for 100 hours, and not used beyond
2 000 hours. Additional sources may also be used, depending on the intended application.
For spectral measurements, if it can be demonstrated that the display does not exhibit
significant PL (< 1 % PL, see Annex A) for the selected reference source spectra, then a
spectrally smooth broadband source (such as an approximation to CIE Standard
Illuminant A) may be used to measure the spectral reflectance factor. Without significant
PL, a measurement of the spectral reflectance factor using a broad source (like Illuminant
A) enables the ambient contrast ratio and colour to be calculated later for the desired
reference spectra (for example D65). The indoor room contrast ratio shall be calculated
using 60 lx of hemispherical diffuse illumination (with specular included) incident on the
display surface for a typical TV viewing room, and 300 lx for an office environment [3].
The actual hemispherical diffuse reflectance factor measurement may require higher
illumination levels for better measurement accuracy. The results are then scaled to the
required illumination levels.
• Directional illumination- The same source spectra shall be used as with hemispherical
diffuse illumination. If a different spectral source is used, it shall be noted in the ambient
performance report. The presence of significant PL (see Annex A) shall also be
determined for the measured source, and the preceding limitations be applied when PL is
present. The indoor room contrast ratio or colour shall be calculated using directional
illumination of 40 lx incident on the display surface for a typical TV viewing room, and
200 lx for an office environment with the display in the vertical orientation. The actual
reflectance factor measurement may require higher illumination levels for better
measurement accuracy. The directed source shall be 35 ° above the surface normal
θ =35 °, θ =0 °, see Figure 3) and have an angular subtense of no more than 8 °. The
(
s d
angular subtense is defined as the full angle span of the light source from the centre of
the display’s measurement area.

– 12 – 62341-6-2 © IEC:2012
NOTE Other illumination levels may be used in addition to those defined above for calculating the ambient
contrast ratio under indoor illumination conditions. However, approximately 60 % of the total illuminance
should be hemispherical diffuse, and 40 % directional illumination.
Daylight illumination conditions:
• Uniform hemispherical diffuse illumination – Use a light source closely approximating
skylight with the spectral distribution of CIE Illuminant D75 [4]. Additional CIE daylight
illuminants) may also be used, depending on the intended application. An infrared-
blocking filter is recommended to minimize sample heating. The UV region (< 380 nm) of
the light source shall be cut off. For spectral measurements, if it can be demonstrated that
the display does not exhibit significant PL for a 7 500 K correlated colour temperature
(CCT) source, then spectral reflectance factor measurements can be made using a
spectrally smooth broadband source (such as an approximation to CIE Standard
Illuminant A). The contrast ratio or colour can be calculated later for the D75 Illuminant
spectra. The daylight contrast ratio and colour shall be calculated using 15 000 lx of
hemispherical diffuse illumination (with specular included) incident on a display surface in
a vertical orientation [4, 5 ]. The actual hemispherical diffuse reflectance factor
measurement may be taken at lower illumination levels.
• Directional illumination – The directional light source shall approximate CIE daylight
Illuminant D50) [4]. Additional CIE daylight illuminants may also be used, depending on
the intended application. The use of an infrared-blocking filter is recommended to
minimize sample heating. The UV region (< 380 nm) of the light source shall be cut off. If
it can be demonstrated that the display does not exhibit significant PL for a source
approximating Illuminant D50, then a spectrally smooth broadband source (such as an
approximation to CIE Standard Illuminant A) may be used for the reflectance factor
measurement. The ambient contrast ratio or colour can be calculated later with the D50
Illuminant spectra. The daylight contrast ratio or colour shall be calculated using 65 000 lx
for a directed source at an inclination angle of θ = 45 ° to the display surface (see
s
Figure 3) [4][,5]. The actual reflectance factor measurement may be taken at lower
illumination levels, and the contrast ratio and colour calculated for the correct illuminance.
The directed source shall have an angular subtense of approximately 0,5 °.
For daylight contrast ratio and colour calculations from spectral reflectance factor
measurements, the relative spectral distributions of CIE Illuminant A, lamp FL1, D65, D50 and
D75 tabulated in CIE 15 shall be used. Additional CIE daylight illuminants shall be determined
using the appropriate eigenfunctions, as defined in publication CIE 15.
5.2.2.3 Uniform hemispherical diffuse illumination
An integrating sphere, sampling sphere, or hemisphere shall be used to implement uniform
hemispherical diffuse illumination conditions. Two possible examples of the measurement
geometry are shown in Figure 2. If an integrating sphere that is at least seven times the
physical outer diagonal of the display is available, the display can be mounted in the centre of
the sphere (Figure 2, configuration A). For large displays, a sampling sphere (configuration B)
or hemisphere would be more suitable. In all cases, the configuration shall follow the standard
di/8 ° to di/10 ° illumination/detection geometry, where di is the standard notation for diffuse.

62341-6-2 © IEC:2012 – 13 –
Light
Specular Measurement port
source
Point
θ = 8°-10°
Baffle
θ
Display
θ
Reflectance
Lamp
Lamp
standard
8°-10°
Baffle
Sample port
Light
measuring
Display
Display
device
Configuration B (side view)
Configuration A (top view)
IEC  85/12
Figure 2 – Example of measurement geometries for diffuse illumination condition
using an integrating sphere and sampling sphere
a) The display is placed in the centre of an integrating sphere/hemisphere, or against the
sample port of a sampling sphere. The reflected luminance off the display from the sphere
shall be much greater than the luminance from the display-generated light. For displays
without significant PL, the reflected luminance from the sphere can be estimated with the
display turned OFF.
b) For daylight measurements with an approximate 7 500 K CCT light source, an infrared-
blocking filter is recommended to minimize sample heating. The colour temperature and
illumination spectra can be measured from the reflected light of a white diffuse reflectance
standard near the display measurement area (Figure 2, Configuration A), or the sampling
sphere wall adjacent to the sample port (Figure 2, Configuration B.). The type of light
source used, and its CCT, shall be noted in the ambient performance report.
c) The light measuring device (LMD) is aligned to view the centre of the display through a
measurement port in the sphere wall at an 8 ° (−0 °, +2 °) angle from the display normal.
The required LMD angle of inclination can also be realised by tilting the display within the
integrating sphere. The LMD is focused on the display surface.
d) The measurement port diameter shall be 20 % to 30 % larger than the effective aperture of
the LMD lens. Care needs to be taken to avoid any direct light from the sources, or any
bright reflections off any surface (other than the screen itself), from hitting the lens of the
LMD in order to minimise veiling glare contamination of the reflected luminance
measurement. The LMD shall be moved back from the hole so that the bright walls of the
sphere are not visible to the LMD. In addition, the sample port diameter will typically need
to be larger than 25mm in order for the luminance meter’s or spectroradiometer’s field of
view to be completely contained within the sample port.
e) The measurement port shall be bevelled away from the lens. The small diameter of the
bevel is toward the LMD, and the large diameter on the inside of the sphere.
f) The spectral irradiance or illuminance on the display can be measured using a white
diffuse reflectance standard with known hemispherical diffuse spectral reflectance factor
R(λ), or the photopically-weighted (or luminous) hemispherical diffuse reflectance factor R.
The white diffuse reflectance standard must be calibrated under uniform hemispherical
diffuse illumination in an integrating sphere. When an integrating sphere (configuration A)
or hemisphere is used, the white diffuse reflectance standard shall be placed on the
display surface. If t is the thickness of the white diffuse reflectance standard, then it shall
be placed on the surface a distance of 5*t to 7*t from the measurement area. The white
reflectance standard can also be placed adjacent and in the same plane as the display if
the sphere illumination is uniform over that distance. In the case of the sampling sphere,
the spectral irradiance can be determined by a measurement of the interior sphere wall
adjacent to the sample port.[6] The hemispherical diffuse spectral reflectance factor, or

– 14 – 62341-6-2 © IEC:2012
the luminous hemispherical diffuse reflectance factor, of the interior sphere wall can be
determined by comparing the spectral radiance (or luminance) of the wall with that of a
calibrated white diffuse reflectance standard placed at the sample port
(i.e. R = R *(L /L ).
wall std wall std
g) If a sampling sphere is used, the display measurement area shall contain more than 500
display pixels. It is recommended that the sampling sphere be at least six times larger
than the sample port diameter. If there is a significant distance between the display
emitting surface and the sample port entrance, then the size of the sample port may need
to be increased [7].
h) The illuminance across the display measurement area shall vary less than ± 5 % from the
average.
5.2.2.4 Directed source illumination
Directional illumination shall be simulated by an isolated directed source (Figure 3) at a
defined angle of inclination to the display surface normal, or ring light (Figure 4) centred about
the normal. This measurement shall be performed in a dark room, with all potential reflective
room surfaces having a matt black coating. Light from the isolated directed source that is
reflected off the display in the specular direction can be collected by a light trap to minimize
its contribution to stray light contamination. The isolated directed source is the preferred
directed source. If the display exhibits strong asymmetric scatter (matrix scatter [8]), then a
ring light shall be used.
a) Position the LMD normal (θ = 0 °) to the display, and focus on the display surface. The
d
isolated directed light source is aligned in the same vertical plane (φ = 0 °) as the display
s
normal and LMD, but at an inclination angle θ from the horizontal plane. The distance
s
between the display and directed source C can be adjusted so that the light source has
s
an angular subtense of ≤ 8 ° for indoor applications, or approx
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