IEC 62977-3-9:2023

Electronic displays - Part 3-9: Evaluation of optical performance - Display sparkle contrast

IEC 62977-3-9:2023 specifies standard measurement conditions and methods for determining the sparkle contrast of direct-view displays which comprise display matrix elements to render real 2D images on a flat panel and an anti-glare layer. This document excludes measurement of sparkle, which is intentionally obtained by the specular reflection from reflecting flakes in coatings and paints.

General Information

• Status: Published
• Publication Date: 21-Jun-2023
• ICS: 31.120 - Electronic display devices
• ICS: 31.260 - Optoelectronics. Laser equipment
• Technical Committee: TC 110 - Electronic displays
• Drafting Committee: WG 13 - TC 110/WG 13
• Current Stage: PPUB - Publication issued
• Start Date: 30-Jun-2023
• Completion Date: 22-Jun-2023

Standards Content (Sample)

IEC 62977-3-9
®

Edition 1.0 2023-06
INTERNATIONAL
STANDARD

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Electronic displays –
Part 3-9: Evaluation of optical performance – Display sparkle contrast
IEC 62977-3-9:2023-06(en)

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IEC 62977-3-9

®


Edition 1.0 2023-06




INTERNATIONAL



STANDARD








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inside










Electronic displays –

Part 3-9: Evaluation of optical performance – Display sparkle contrast


























INTERNATIONAL

ELECTROTECHNICAL


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ICS 31.120; 31.260 ISBN 978-2-8322-7063-9




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® Registered trademark of the International Electrotechnical Commission

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– 2 – IEC 62977-3-9:2023 © IEC 2023
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, abbreviated terms and letter symbols . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 7
3.3 Letter symbols . 7
4 Standard measurement conditions . 9
4.1 Environmental conditions . 9
4.2 Dark room conditions . 9
4.3 Warm-up time . 9
4.4 Measurement coordinate systems . 9
4.5 Standard conditions for the measuring equipment . 10
4.5.1 General . 10
4.5.2 Conditions of measuring equipment . 11
4.5.3 Standard measurement locations . 12
4.6 Test pattern . 12
5 Measurement methods . 13
5.1 Purpose . 13
5.2 Equipment and conditions . 13
5.3 Measurement procedure . 13
5.4 Calculation . 14
5.5 Report. 14
Annex A (informative) Imaging and sampling conditions of sparkle pattern . 15
A.1 Oversampling . 15
A.2 Undersampling . 16
Annex B (informative) Filtering methods for removing periodic modulations from the
image . 17
B.1 General . 17
B.2 Filtering methods . 18
B.2.1 Filtering in spatial domain . 18
B.2.2 Filtering in frequency-domain . 20
Annex C (informative) Hardware parameters that affect the sparkle contrast . 21
C.1 LMD aperture setting . 21
C.2 LMD focus . 21
C.3 Condition to avoid aliasing . 22
Annex D (informative) Sparkle contrast measurement with display mock-up . 23
D.1 Display mock-up . 23
D.2 Measurement . 23
Annex E (informative) Calculation of sparkle contrast by the difference image method . 25
E.1 Statistical background . 25
E.2 Measurement procedure of the difference image method . 25
E.3 Calculation of sparkle contrast by the difference image method . 26
Annex F (informative) Calculation of sparkle contrast by the pixel power deviation
method . 27
F.1 Pixel power deviation description . 27

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IEC 62977-3-9:2023 © IEC 2023 – 3 –
F.2 Measurement procedure for the PPD method . 27
Annex G (informative) Elimination of low-frequency radiance variation from the sparkle
pattern . 29
G.1 General . 29
G.2 Normalization of the local average radiance of segmented sparkle pattern . 29
G.3 Calculating the mean or median value of the segmented sparkle pattern . 30
Bibliography . 31

Figure 1 – Cartesian coordinate system and spherical coordinate system for the
specification of the viewer's gazing (viewing) direction . 9
Figure 2 – Typical relative spectral response of a CCD detector array without IR-
blocking filter (B/W camera) and a luminance meter with a sensitivity according to
CIE V(λ) . 11
Figure 3 – Measurement setup . 13
Figure A.1 – Examples of sparkle image from the same DUT under different
measurement distances . 16
Figure B.1 – Display matrix element (grey square) in relation to the matrix of the
imaging LMD detector elements (squares according to LMD pixel pitch) for the case of
oversampling with an image sampling ratio of R = 3,5 . 18
S
Figure B.2 – Examples of sparkle patterns at R = 4,3 before applying an MWA filter
S
(left) and after applying an MWA filter (right) . 19
Figure B.3 – Electronic images of the DUT (i.e., display matrix elements with AGL, left)
and frequency components of that image used as basis for sparkle evaluation . 20
Figure C.1 – Example of the variation of the MTF of the imaging LMD under different
F‑numbers as a function of spatial frequency of LMD pixels . 21
Figure D.1 – Examples of display mock-ups . 23
Figure D.2 – Example of measurement configuration . 24
Figure G.1 – Example of the segmentation of the measurement field for the preparation
of the elimination of the low-frequency radiance variations from the sparkle pattern . 29

Table 1 – Letter symbols (quantity symbols and units) . 7
Table 2 – Distinguishing types of DUT, imaging conditions, number of involved images
and methods for suppression of display matrix modulations . 10
Table B.1 – Filtering method capabilities for removing artifacts related to display matrix
elements . 17

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ELECTRONIC DISPLAYS –

Part 3-9: Evaluation of optical performance –
Display sparkle contrast

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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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62977-3-9 has been prepared by IEC technical committee 110: Electronic displays. It is an
International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
110/1515/FDIS 110/1525/RVD

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 International Standard is English.

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IEC 62977-3-9:2023 © IEC 2023 – 5 –
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/publications.
A list of all parts in the IEC 62977 series, 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 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.

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ELECTRONIC DISPLAYS –

Part 3-9: Evaluation of optical performance –
Display sparkle contrast



1 Scope
This part of IEC 62977 specifies standard measurement conditions and methods for determining
the sparkle contrast of direct-view displays which comprise display matrix elements to render
real 2D images on a flat panel and an anti-glare layer. This document excludes measurement
of sparkle, which is intentionally obtained by the specular reflection from reflecting flakes in
coatings and paints.
2 Normative references
There are no normative references in this document.
3 Terms, definitions, abbreviated terms and letter symbols
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Terms and definitions
3.1.1
sparkle
visual phenomenon that becomes obvious as a random pattern extending across the display
area formed by a distribution of tiny patches (granules, dots) with varying luminance and
chromaticity (depending on the test pattern shown on the display) through the anti-glare layer
of the display, resulting in a visually disturbing pattern that is distinctly changing with viewing
direction
Note 1 to entry: In other fields, the term “sparkle” can refer to reflections from reflecting particles in effect coatings
[1].
Note 2 to entry: Sparkle looks like “speckle” [2] in the field of laser displays (coherent or partially coherent light),
however sparkle and speckle are different because the origins of both phenomena are quite different.
3.1.2
sparkle pattern
radiance distribution of sparkle
Note 1 to entry: The sparkle pattern can contain (1) periodic modulations caused by the display pixel matrix, (2)
non-periodic effects caused by, for example, pixel defects, and (3) low-frequency radiance variations caused by non-
uniformities of the backlight unit.

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IEC 62977-3-9:2023 © IEC 2023 – 7 –
3.1.3
sparkle contrast
S
P
quotient of the standard deviation of the radiance variation of the sparkle pattern in the
measurement field divided by its mean (average) value
3.1.4
anti-glare layer
AGL
scattering layer for the suppression of distinct (mirror) images of ambient light sources reflected
by smooth polished (display) surfaces
3.1.5
image sampling ratio
ISR
ratio of the pitch of display matrix elements multiplied by the magnification of the imaging lens
to the pitch of the elements of the detector array
Note 1 to entry: For the details, see Annex A.
Note 2 to entry: The display matrix element refers to a physical sub-pixel in the display products. In the display mock-
up, it means a fundamental element partitioned by the black matrix.
3.2 Abbreviated terms
A/D analog/digital
AGL anti-glare layer
CCD charge coupled device
CMOS complementary metal oxide semiconductor
DUT device under test
ISR image sampling ratio
LMD light measuring device
MWA moving window averaging
MTF modulation transfer function
PPD pixel power deviation
3.3 Letter symbols
The letter symbols are shown in Table 1.
Table 1 – Letter symbols (quantity symbols and units)
Quantities Symbols and units
Fundamental frequency of the periodic modulation of the display
f
(lp/mm)
0
matrix image
Measurement distance L (mm)
F-number (infinity) F# (-)
F#
Effective F-number (-)
E
Focal length f (mm)
Z
Image distance (mm)
L

Optical magnification m (-)

R
Image sampling ratio (ISR) (-)
S

Diameter of the airy disk of the LMD lens as projected on the DUT S (μm)

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Quantities Symbols and units
P
Pitch of the image of the display matrix elements (μm)
D

Dominant wavelength of the primary colour of the display λ (μm)
2
Standard deviation of the radiance variation of the sparkle pattern σ
(W/sr/m )
2
Mean radiance of the sparkle pattern μ
(W/sr/m )

S
Sparkle contrast (-)
P

Radiance matrix representing the image of the DUT L(x, y) (-)

Square convolution kernel K(s, t) (-)

*
Radiance matrix representing the filtered DUT image (-)
L (x, y)

Variables used during convolution s, t (-)
Number of LMD pixels in the square kernel per side given by the

k (-)
square of the closest odd integer

S
Sum of all weights used in the convolution matrix (-)
W
Standard deviation of the radiance variation of the sparkle pattern
2
σ
(W/sr/m )
1
from the image 1 which is used for the difference image method
Standard deviation of the radiance variation of the sparkle pattern
2
σ
(W/sr/m )
2
from the image 2 which is used for the difference image method
2
σ
Standard deviation of the radiance variation of the difference image (W/sr/m )
diff
2
Average background radiance used for the PPD calculation bg
(W/sr/m )
Average sample radiance within the pixel bin with coordinates i and
2
T
(W/sr/m )
ij
j, which is used for the PPD calculation
Average normalized sample radiance within the pixel bin with
2
nT
(W/sr/m )
ij
coordinates i and j, which is used for the PPD calculation
Average normalized sample radiance over all element bins contained
2
nT (W/sr/m )
ij
within area A, which is used for the PPD calculation
Average reference radiance within the element bin with coordinates i
2
R
(W/sr/m )
ij
and j, which is used for the PPD calculation
Horizontal dimension in units of elements of area A which is used for

u (-)
the PPD calculation
Vertical dimension in units of elements of area A which is used for

v (-)
the PPD calculation
Number of segments per side used for the elimination method of the

P (-)
low-frequency radiance variations from the sparkle pattern
Number of LMD pixels per side in the segment used for the

elimination method of the low-frequency radiance variations from the Q (-)
sparkle pattern
NOTE 1 L is a distance from the DUT to the principal point of the imaging lens along with the optical axis. The
1
principal point of the imaging lens can be determined experimentally by the method in section 17.5 of [3] .
NOTE 2 Z is a distance from the principal point to the image point of the imaging lens along with the optical
L
axis.

___________
1
 Numbers in square brackets refer to the Bibliography.

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IEC 62977-3-9:2023 © IEC 2023 – 9 –
4 Standard measurement conditions
4.1 Environmental conditions
Measurements shall be carried out under the standard environmental conditions:
– temperature: 25 °C ± 3 °C,
– relative humidity: 25 % to 85 % RH,
– atmospheric pressure: 86 kPa to 106 kPa.
When different environmental conditions are used, they shall be noted in the measurement
report.
4.2 Dark room conditions
The luminance contribution from ambient illumination reflected off the display shall be less than
1/20 of the lowest black level of the display. In the case of other dark room conditions, these
shall be reported.
4.3 Warm-up time
The measurements shall be carried out after the DUT radiance and LMD are sufficiently stable.
The radiance shall not vary by more than ±5 % over the entire measurement.
4.4 Measurement coordinate systems
The viewing direction is the direction under which the observer gazes at the point of interest on
the device under test (DUT). During the measurement, the imaging light measurement device
(LMD) simulates the observer, by aiming the LMD at the location of interest on the DUT from
the viewing direction. The viewing direction is defined by two spherical angles: the angle of
inclination θ (relative to the surface normal of the DUT) and the angle of rotation φ (also called
azimuthal angle) as illustrated in Figure 1. Although the azimuthal 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° is the 12-o'clock direction ("top"), φ = 180° the 9-o'clock
direction ("left") and φ = 270° the 6-o'clock direction ("bottom").

Figure 1 – Cartesian coordinate system and spherical coordinate system
for the specification of the viewer's gazing (viewing) direction

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4.5 Standard conditions for the measuring equipment
4.5.1 General
Measurement and evaluation of sparkle contrast can be performed during several stages of
display manufacturing and use. Table 2 gives the explanation of the structure of this document,
including the different measurements and their mutual relations. Combination of the display and
the anti-glare layer (AGL) is the measurement subject of this document. The main body of this
document only includes the typical measurement method which is commonly used for the
measurements of sparkle contrast. For the cases when the image of the display matrix elements
appears on the sparkle pattern, image filtering methods can be applied (see Annex B for
examples of filtering methods). Annex F specifies a sparkle measurement technique that
incorporates filtering after the images have been collected. Depending on the measurement
conditions, the image of the display matrix elements, or moiré pattern (sampling artefact, see
Annex A) can appear on the sparkle pattern. There are also cases where the image of the
display matrix is not shown on the captured image because of the low modulation transfer
function (MTF) condition of the imaging LMD (see Annex A).
During product development and optimization, the AGL (on a glass substrate or integrated into
or applied to polymer films) is usually available as a separate component. In this case, there
are two methods which can separate the random radiance variations that constitute sparkle
from the low-frequency radiance variations caused by the non-uniformity of the backlight by
using two different images. One is the difference image method in Annex E, the other is the
pixel power deviation in Annex F. These methods are intended to investigate the performance
of the AGL components under the fixed pitch of the display matrix elements. In the case where
only the performance of the AGL components is investigated, a display mock-up can be used
instead of intact displays. The details are introduced in Annex D.
NOTE The low-frequency radiance variations caused by the non-uniformity of the backlight can be removed by the
methods in Annex G, when the DUT is an inseparable combination of the display and the AGL.
Table 2 – Distinguishing types of DUT, imaging conditions, number of involved
images and methods for suppression of display matrix modulations
DUT Imaging Number and nature of images suppression of display matrix
modulation
Inseparable Wide-band Image number 1: sparkle pattern Image filtering in spatial domain
combination of display with display matrix modulation – MWA (B.2.1)
and AGL
Image filtering in frequency
domain (B.2.2)
Low-pass Image number 1: sparkle pattern No need for filtering applied to
(Annex A) without display matrix modulation the image (Annex A).
Separate AGL + intact Wide-band Image number 1: sparkle pattern Image filtering in spatial domain
display with display matrix modulation – MWA (B.2.1)
Separate AGL + Image filtering in frequency
display mock-up domain (B.2.2)
(Annex D)
Image number 1: sparkle pattern Difference image method
with display matrix modulation (Annex E)
Image number 2: sparkle pattern
(with the methods in Annex B, if
with display matrix modulation
necessary)
Image number 1: sparkle pattern PPD (Annex F)
with display matrix modulation
Image number 2: display matrix
image
Low-pass Image number 1: sparkle pattern No need for filtering applied to
(Annex A) without display matrix modulation the image (Annex A).
The configuration and the status of the components as agreed by the involved parties have to
be specified in the measurement report.

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IEC 62977-3-9:2023 © IEC 2023 – 11 –
Standard equipment conditions are given in 4.5.2. Any deviations from these conditions shall
be noted in the re
...