IEC 63145-22-20:2024
(Main)Eyewear display - Part 22-20: Specific measurement methods for AR type - Image quality
Eyewear display - Part 22-20: Specific measurement methods for AR type - Image quality
IEC 63145-22-20:2024 specifies the standard measuring conditions and measurement methods for determining the image quality of augmented reality (AR) type eyewear displays. This document applies to see-through type (AR glasses) eyewear displays using virtual image optics.
See-through type displays (VR glasses), contact lens-type displays, and retina direct projection displays are out of the scope of this document.
The content of the corrigendum 1 (2024-09) has been included in this copy.
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IEC 63145-22-20 ®
Edition 1.0 2024-02
INTERNATIONAL
STANDARD
colour
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Eyewear display –
Part 22-20: Specific measurement methods for AR type – Image quality
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IEC 63145-22-20 ®
Edition 1.0 2024-02
INTERNATIONAL
STANDARD
colour
inside
Eyewear display –
Part 22-20: Specific measurement methods for AR type – Image quality
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.180.99; 31.120 ISBN 978-2-8322-8131-4
– 2 – IEC 63145-22-20:2024 © IEC 2024
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 (quantity symbols or unit symbols) . 7
4 Standard measuring conditions . 8
4.1 Standard environment conditions . 8
4.2 Power supply . 8
4.3 Warm-up time . 8
4.4 Dark room condition . 8
5 Measurement systems . 8
5.1 Standard coordinate system . 8
5.2 Measurement equipment . 9
5.2.1 General . 9
5.2.2 Light measuring device (LMD) . 9
5.2.3 Stage conditions . 9
5.2.4 Setup conditions . 10
6 Background and see-through real scene conditions . 10
6.1 General . 10
6.2 Ambient background . 11
6.3 Raster pattern (or grille pattern) targets . 11
6.4 Crosshair pattern target . 12
7 Test patterns of the virtual image. 13
7.1 General . 13
7.2 Checkerboard pattern . 13
7.3 Solid colour patterns . 13
7.4 Raster patterns . 13
7.5 Measuring points . 13
8 Measurement methods . 13
8.1 Preparation . 13
8.2 Luminous transmittance and spectral transmittance with an ambient diffuse
illumination . 14
8.2.1 General . 14
8.2.2 Measuring conditions . 14
8.2.3 Measuring procedures . 14
8.2.4 Calculation . 14
8.2.5 Report . 16
8.3 Parameters related to virtual images . 16
8.3.1 Ambient contrast ratio . 16
8.3.2 Ambient chromaticity and chromaticity gamut area . 18
8.3.3 Static image resolution . 20
8.3.4 Secondary image effect . 22
8.3.5 Flicker . 24
8.4 Parameters related to see-through real scene . 26
8.4.1 See-through FOV . 26
8.4.2 Variations in luminance and chromaticity of see-through real scenes . 29
8.4.3 Real rectangular scene distortion. 32
8.4.4 Real local geometric distortion . 34
8.4.5 Ratio of Michelson contrast of the real scene . 36
8.4.6 Luminance ratio of virtual image versus background . 37
8.4.7 Monocular positioning accuracy . 38
Bibliography . 41
Figure 1 – Spherical coordinate system . 9
Figure 2 – Three-dimensional Cartesian coordinate system . 9
Figure 3 – Example of the ambient background . 11
Figure 4 – Example of the setting for a raster pattern target . 12
Figure 5 – Example of the setting for a crosshair pattern target . 12
Figure 6 – Variation of Michelson contrast (i.e. luminance modulation) with line width . 21
Figure 7 – Example of a secondary image . 23
Figure 8 – Temporal contrast sensitivity function . 25
Figure 9 – Example of the see-through FOV . 28
Figure 10 – Measuring points of the real scene (origin at the centre B , corresponding
to the optical axis of the DUT) . 29
Figure 11 – Example of a real local geometric distortion . 35
Figure 12 – Schematic diagram of the positioning measurement . 39
Table 1 – Letter symbols (quantity symbols or unit symbols) . 7
Table 2 – Temporal contrast sensitivity function . 25
Table 3 – Example of the angle deviation of the 9 points and the distortions . 34
– 4 – IEC 63145-22-20:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EYEWEAR DISPLAY –
Part 22-20: Specific measurement methods for AR type –
Image quality
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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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shall not be held responsible for identifying any or all such patent rights.
IEC 63145-22-20 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
110/1580/FDIS 110/1599/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.
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 63145 series, published under the general title Eyewear display,
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, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document 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 – IEC 63145-22-20:2024 © IEC 2024
EYEWEAR DISPLAY –
Part 22-20: Specific measurement methods for AR type –
Image quality
1 Scope
This part of IEC 63145 specifies the standard measuring conditions and measurement methods
for determining the image quality of augmented reality (AR) type eyewear displays. This
document applies to see-through type (AR glasses) eyewear displays using virtual image optics.
See-through type displays (VR glasses), contact lens-type displays, and retina direct projection
displays are out of the scope of 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 of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 63145-1-2, Eyewear display – Part 1-2: Generic – Terminology
IEC 63145-20-10:2019, Eyewear display – Part 20-10: Fundamental measurements – Optical
properties
IEC 63145-20-20:2019, Eyewear display– Part 20-20: Fundamental measurements – Image
quality
ISO 9241-302, Ergonomics of human-system interaction – Part 302: Terminology for electronic
visual displays
ISO/CIE 11664-1, Colorimetry – Part 1: CIE standard colorimetric observers
ISO/CIE 11664-5, Colorimetry – Part 5: CIE 1976 L*u*v* colour space and uʹ, vʹ uniform
chromaticity scale diagram
CIE 015:2018, Colorimetry
3 Terms, definitions, abbreviated terms and letter symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 63145-1-2,
IEC 63145-20-10, IEC 63145-20-20 and ISO 9241-302 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
NOTE 1 Terms related to eyewear displays will be defined in specific projects.
NOTE 2 Additional terms can be found in IEC TR 63145-1-1 [1] .
3.2 Abbreviated terms
2D two-dimensional
AR augmented reality
CIE Commission Internationale de l’Eclairage (International Commission on Illumination)
CPD cycles per degree
DUT device under test
FOV field of view
LMD light measuring device
ppd pixel per degree
3.3 Letter symbols (quantity symbols or unit symbols)
The letter symbols for eyewear display are shown in Table 1.
Table 1 – Letter symbols (quantity symbols or unit symbols)
Definition Symbol
Measuring point of virtual image
P
i
(i = 0 at the centre)
Measuring point of real scene target
B
i
(i = 0 at the centre)
Luminance of a position (x, y, z) in a direction (α, Ψ) on the eyewear
−2
L (x, y, z, α,Ψ)
(cd m )
v
display
Spectral radiance of the virtual image at P point under ambient
i
-1 −2 −1
L (λ, i)
(W sr m nm )
Amb
illumination
Spectral radiance of the virtual image at P point under dark
i -1 −2 −1
L (λ, i)
m nm )
(W sr
D
background
−2
L
Average luminance (spatial) (cd m )
av
CIE 1931 chromaticity coordinates at P x , y
i i i
A
Chromaticity gamut area
xy
CIE 1976 chromaticity coordinates at P u’ , v’
i i i
Chromaticity deviation ∆u’v’
C
Luminance ratio
vb
CR
Ambient contrast ratio
A
Spectral transmittance of the DUT at P point
T(λ, i)
i
-1 −2 −1
L (λ)
Spectral radiance of the illumination background
(W sr m nm )
s
CIE standard spectral luminous efficiency for photopic vision V(λ)
Wavelength interval ∆λ (nm)
___________
Numbers in square brackets refer to the Bibliography.
– 8 – IEC 63145-22-20:2024 © IEC 2024
4 Standard measuring conditions
4.1 Standard environment conditions
Unless otherwise specified, all tests and measurements for eyewear displays shall be carried
out after sufficient warm-up time for illumination sources and the DUT (see 4.3), under the
following standard environmental conditions:
• temperature: 22°C to 28°C,
• relative humidity: 25 % to 85 %,
• atmospheric pressure: 86 kPa to 106 kPa.
When different environmental conditions are used, they shall be reported in detail in the
specification.
4.2 Power supply
In order to stabilize the performance of the DUT, the power supply for driving the DUT shall be
adjusted in accordance with the specification of the DUT.
4.3 Warm-up time
The optical performances of the DUT are affected by the transient temperature behaviour of the
device. It takes a certain time for the DUT and LMD until their performances reach the steady-
state. All measuring conditions shall be kept constant during the measurements. If the
luminance output is not within a ±3 % variation, it shall be reported.
4.4 Dark room condition
The luminance contribution from the background of the test room reflected off the measurement
space shall be less than 1/20 of the minimum luminance output from the DUT. If this condition
is not satisfied, then background luminance can be subtracted, and it shall be reported.
5 Measurement systems
5.1 Standard coordinate system
A spherical coordinate system (α and Ψ angles) shall be used in the measurements, as shown
in Figure 1. The polar axis is vertically oriented. The angles measured in the vertical half-planes
of data are elevation angles, denoted as α, and the horizontal angles to the half-plane are
azimuth angles, denoted as Ψ. A geographic coordinate chart can be used to express the
spherical coordinates of the virtual image produced by the DUT. Refer to IEC 63145-20-10:2019,
Clause 5.
The origin direction (α = 0, Ψ = 0) of the spherical coordinate system is coincident with the
optical axis of the DUT. When performing measurements simulating eye rotation, the centre of
the spherical coordinate system should be 10 mm behind the LMD entrance pupil.
To indicate the positional relationship between the designed eye point of the DUT and the
entrance pupil of the human eye or LMD, a Cartesian coordinates system (x, y, z) is used, as
shown in Figure 2.
The origin of the Cartesian coordinates system should be located at the centre of the entrance
pupil of the eye, which is matched with the eye point of the DUT. The manufacturer or supplier
should provide the eye point position.
Figure 1 – Spherical coordinate system
NOTE The drawing shows an example of adjusting the eye pupil to the eye point, which is the origin position.
Figure 2 – Three-dimensional Cartesian coordinate system
5.2 Measurement equipment
5.2.1 General
The configurations and operating conditions of the equipment should comply with the structures
specified in each item. To ensure repeatable measurements, the requirements shall comply
with IEC 63145-20-10. Otherwise, the differences shall be noted in the report.
5.2.2 Light measuring device (LMD)
The LMDs shall refer to the requirements in IEC 63145-20-10 unless otherwise specified in
each item.
5.2.3 Stage conditions
5.2.3.1 General
The stage shall be used to realize the coordinate system specified in 5.1. The stage shall be
constructed with the equivalent of a biaxial goniometer and an orthogonal three-axis translation
stage.
– 10 – IEC 63145-22-20:2024 © IEC 2024
5.2.3.2 Goniometer
Refer IEC 63145-20-10:2019, 5.2.2.2.
A biaxial goniometer shall be assembled to be capable of measuring azimuth (horizontal) and
elevation (vertical) angles in the spherical coordinate system as in Figure 1. Examples of the
five-axis stage are shown in IEC 63145-20-10:2019, Figure 4. The angular accuracy should be
no less than 0,1°. The goniometer can be pivoted at the centre of the entrance pupil of the LMD,
or 10 mm behind the entrance pupil, or both, to simulate eye rotation.
5.2.3.3 Translation stage
Refer to IEC 63145-20-10:2019, 5.2.2.3.
An orthogonal three-axis translation stage assembles with an adequate range to cover the
measuring distance such as the eye-box volume, and if necessary to cover the interpupillary
distance for binocular DUTs, as in the example shown in IEC 63145-20-10:2019, Figure 4. The
translation accuracy should be no less than 0,05 mm.
5.2.4 Setup conditions
Refer to IEC 63145-20-10:2019. 5.2.3.
The DUT shall be mounted on a stable platform to ensure image stability. The LMD position
relative to the DUT shall be moved by using a five-axis system (a biaxial goniometer and three-
axis orthogonally translation stage). The LMD installed on the biaxial goniometer, as in the
example in IEC 63145-20-10:2019, Figure 4 a), shall be consistently pivoted around its pupil
centre (eye point) or about the centre of the eyeball rotation for each set of measurements. The
optical axis of the DUT, which is decided by a manufacturer or a supplier, shall be adjusted to
the optical axis of the LMD and shall be aligned with the z-axis of the orthogonal three-axis
translation stage. The aspect of the virtual image of the DUT shall be adjusted to the x- and y-
axes of the orthogonal three-axis translation stage.
For the measuring condition from an anterior view, when the DUT does not suppose the change
of gaze angle (eye rotation), the origin of a biaxial goniometer shall be assumed as the entrance
pupil of the eye (i.e. eye point of the DUT), not the rotation centre of the eyeball (eye movement).
When the origin of the biaxial goniometer does not match the eye point, the coordinate
correction shall be required, and it shall be reported. When the DUT supposes the change of
the gaze angle, detailed information such as the position of the rotation centre shall be specified
by the manufacturer or the supplier and reported.
For the measurement of a see-through real scene, the real scene pattern target shall be set at
a distance specified by the manufacturer or supplier, and the optical axis of the LMD shall be
adjusted to be consistent with the normal line of the pattern target. The DUT installed on the
biaxial goniometer as in the example in IEC 63145-20-10:2019, Figure 4 b), can be pivoted
around its eye point (pupil rotation) or about the centre of the eye.
6 Background and see-through real scene conditions
6.1 General
The virtual image quality of AR type eyewear displays will be significantly affected by the
background and see-through real scene conditions. The test background and see-through real
scene shall comply with the specified luminance level and illuminant conditions in each item,
as well as the distance, which are provided by the manufacturer or the supplier.
6.2 Ambient background
Ambient background is a background condition to test the characteristics of the DUT under
ambient illumination conditions. Figure 3 is an example of the ambient background setup.
Uniform spherical illumination using a hemisphere, or a full integrating sphere with a stable light
source, is used to generate the full-field background illumination. The solid angle of the full field
shall be no less than the see-through FOV of the DUT. The luminance variation within the full
field should be less than 2 % as measured by tilting the LMD over the full field. If this is not
achieved, the background luminance should be corrected in the measurement at each direction,
and the correction method and corrected variation value should be reported.
Figure 3 – Example of the ambient background
The relative spectral distribution of the light source shall comply with CIE illuminants, such as
CIE Illuminant A, D50, or D65 as in CIE 015, and be reported. However, when a
spectroradiometer is applied, the source can be a continuous smooth spectral power distribution
of at least 380 nm to 780 nm, and the results can be obtained by calculating with the above CIE
illuminants. The background luminance and its applied illuminant shall be specified by the
manufacturer or the supplier. Some example cases of background luminance include indoor
−2 −2 −2
lighting (30 cd m to 500 cd m ), outdoor sunlight (2 000 cd m for overcast sky, and
−2
15 000 cd m for clear sky), but the application cases are flexible, and not specified in this
document. The light from the surrounding scene consists of different components in actual use
cases. In this document, ambient illumination with a diffuse profile is considered [2] to [4].
6.3 Raster pattern (or grille pattern) targets
The raster pattern targets are used to determine the Michelson contrast of the real scene for
AR type eyewear displays at a direction (α, Ψ) in front of the viewer. The pattern can be
implemented by setting a horizontal (or vertical, or both) raster pattern plate in front of the light
output port of a uniform source, such as an integrating sphere or hemisphere or generated by
a non-transparent display. The raster pattern plate can be composed of black (non-transparent)
) can be calculated
and transparent stripes with the same width, and the angular frequency (f
CPD
from the black and white line-pairs of the raster pattern at a given distance which should be far
enough from the DUT (e.g., more than 20 times of the measured pattern dimension) as shown
in the example in Figure 4. The angular resolution shall be specified by the manufacturer or the
supplier, for example of 60 cycles per degree, 30 cycles per degree, 15 cycles per degree, and
10 cycles per degree at the viewing location (eye point). The relative spectral distribution and
luminance of the light output port shall be specified by the manufacturer or the supplier or as in
6.2.
– 12 – IEC 63145-22-20:2024 © IEC 2024
Figure 4 – Example of the setting for a raster pattern target
NOTE Display pixelation can cause non-uniformities within the grille. These variations will be smoothed out in the
analysis.
6.4 Crosshair pattern target
The crosshair pattern target shall be used to test the geometric distortions of the real scene
through AR type eyewear displays as well as the positioning accuracy of the virtual image to
align with the real scene point at a direction (α, Ψ). The pattern is composed of a bright crosshair
(cross) sign with a width provided by the manufacturer or the supplier, which can be achieved
by setting a transparent cross plate in front of the light output port of a uniform source, as shown
in the example in Figure 5.
NOTE 1 Crosshair pattern target is a transparent cross sign on a black plate target (made of metal or glass). It is
commonly used in orientation and target alignment. Its width is considered relative to the test distance, and its line
width is at a given distance, which is close to the minimum resolvable line width of the virtual image.
NOTE 2 In some cases, a crosshatch pattern with a width given by the manufacturer or the supplier can be applied.
Figure 5 – Example of the setting for a crosshair pattern target
7 Test patterns of the virtual image
7.1 General
The following test patterns shall be specified by the manufacturer or the supplier, and the
applied test pattern shall be noted in the report. When other test patterns are applied, they shall
be noted in the report.
NOTE Unlike a flat panel display with clearly visible edges display, the boundary of the display area is not clear,
and the choice of test pattern can affect the measurement results.
7.2 Checkerboard pattern
Refer to IEC 63145-20-10:2019, 5.3.2.
7.3 Solid colour patterns
Refer to IEC 63145-20-10:2019, 5.3.3.
7.4 Raster patterns
Refer to IEC 63145-20-20:2019, 5.3.4.
7.5 Measuring points
Refer to IEC 63145-20-20:2019, 5.4.
8 Measurement methods
8.1 Preparation
AR type eyewear displays to be measured (DUT) shall be placed in the measurement
arrangement specified in Clause 5. The eye point of the DUT shall be specified by the
manufacturer or supplier (see IEC 63145-20-10:2019, Annex B). The eye point and the entrance
pupil of the LMD shall match the origin position (x = 0, y = 0, z = 0, α = 0, Ψ = 0).
The DUT adjustable conditions which are related to optical properties shall be specified by the
manufacturer or supplier. Some DUTs use image processing, and if a setting for the image
processing is adjustable, the default setting specified by the manufacturer or supplier shall be
applied and reported.
The entrance pupil of the LMD shall be centred to be consistent with the designed eye point of
the DUT at the origin position (x = 0, y = 0, z = 0). An alignment pattern with a crosshair at the
centre position can be used for adjustment of the origin (α = 0, Ψ = 0) of the LMD.
NOTE 1 In case the pivoting point of the LMD is 10 mm behind the entrance pupil, this pivoting point can be used,
instead of the entrance pupil, to match the origin position of the measurement.
For the measurement of virtual images, a raster pattern target, specified in 7.4 with a high
resolution can be provided by the manufacturer or supplier, and can be applied to adjust the
virtual image focus.
For the measurement of real scenes, a raster pattern target as specified in 6.3 with a high
angular resolution which depends on the distance of the pattern target and provided by the
manufacturer or supplier, can be applied to the adjustment of the real scene focus.
The optical quantities of the LMD, such as luminance and spectral radiance, shall be calibrated
against traceable standards under the same conditions (for example entrance pupil size and
measurement field angle, and focus distance in some structures).
– 14 – IEC 63145-22-20:2024 © IEC 2024
The optical quantities at different measuring points (directions) shall be measured at the steady-
state after the required time specified in 4.3.
NOTE 2 Some eyewear displays have eye-tracking capabilities for optimizing the image. The gaze direction of the
LMD will agree with the gaze direction as detected by the DUT for a true eye, if applicable.
8.2 Luminous transmittance and spectral transmittance with an ambient diffuse
illumination
8.2.1 General
The purpose of this method is to measure the spectral transmittance of an AR type eyewear
display in given directions, to determine the virtual image quality under the ambient diffuse
illumination conditions, and the see-through real scene quality.
8.2.2 Measuring conditions
a) Setup: an ambient background shall be applied as specified in 6.2. The optical axis of the
DUT is set at the normal of the output port. The LMD shall be installed to match the entrance
pupil of the LMD with the DUT’s eye point and the optical axis between the LMD and DUT.
b) Light measuring devices (LMDs): a spectral radiance meter shall be applied as specified in
5.2.2.
c) Test patterns: the full screen solid colour patterns as specified in 7.3 shall be applied.
d) Measuring points: the points (directions) to be measured on the virtual image as specified
in IEC 61345-20-20:2019, 5.4, or the specified points (directions) on the real scene in each
point to be measured. The LMD is adjusted to focus on the measuring points.
8.2.3 Measuring procedures
The spectral transmittance of the DUT at the measuring point, such as the measuring point P
i
(i = 0 to 8) of the virtual image specified in IEC 63145-20-20:2019, 5.4, shall be measured as
follows:
a) The LMD is focused on the measuring point.
b) In a dark background, the DUT is applied with the full screen patterns, such as black and
white patterns, then the spectral radiance of the virtual image at point P , L (λ, i) and
i D,K
L (λ, i), is measured, respectively.
D,W
c) Turn on the illuminating source of the integrating sphere until it is stable in the light output
(luminance variation less than 1 %). Apply full screen patterns, such as black and white
patterns, to measure the spectral radiance at point P , L (λ, i) and L (λ, i),
i Amb,K Amb,W
respectively, for the combination of the virtual image and the background illumination.
d) Remove the DUT, and then measure the spectral radiance of the output port of the
illuminating sphere, L (λ, i).
e) For a binocular AR type eyewear display, repeat steps a) to c) to determine the spectral
transmittance of another ocular, if applicable.
8.2.4 Calculation
The spectral transmittance at the point P (i = 0 to 8) can be calculated as follows.
i
An example of the DUT with the white pattern is as follows:
L ()λi,,− L ()λi
Amb,W D,W
T ()λi, =
(1)
W
L ()λi,
where
T (λ, i) is the spectral transmittance at point P (i = 0 to 8) for the DUT with the white
W i
pattern;
L (λ, i) is the spectral radiance at point P (i = 0 to 8) under the diffuse illumination for the
Amb,W i
DUT with the white pattern;
L (λ, i) is the spectral radiance at point P (i = 0 to 8) under the dark background for the
D,W i
DUT with the white pattern;
L (λ, i) is the spectral radiance of the output port of the illuminating sphere.
The luminous transmittance, T (i) (i = 0 to 8), of the DUT under the diffuse illumination can be
W
calculated as follows:
S()λ T (λ,i)V()λ∆λ
∑
W
Ti()=
(2)
W
S()λV()λ∆λ
∑
where
S(λ) is the relative spectral radiance of the diffuse illumination (see 6.2);
V(λ) is the CIE standard spectral luminous efficiency function for photopic vision
(see ISO/CIE 23539 [8]);
Δλ is the spectral interval of the calculation.
An example of the DUT with the black pattern is as follows:
L ()λλ,,i −L ()i
Amb,K D,K
T ()λ,i =
(3)
K
L ()λ,i
where
T (λ, i) is the spectral transmittance at point P (i = 0 to 8) for the DUT with the black
K i
pattern;
L (λ, i) is the spectral radiance at point P (i = 0 to 8) under the illumination for the DUT
Amb,K i
with the black pattern;
L (λ, i) is the spectral radiance at point P (i = 0 to 8) under the dark background for the
D,K i
DUT with the black pattern.
The luminous transmittance, T (i) (i = 0 to 8), of the DUT under the diffuse illumination can be
K
calculated as follows:
S()λ T (λ,i)V()λ∆λ
∑ K
Ti()=
(4)
K
S()λV()λ∆λ
∑
NOTE In many cases, the DUT has substantially the same spectral transmittance, which is independent of the
displaying patterns. The measurement can be simplified to display the off-state only.
– 16 – IEC 63145-22-20:2024 © IEC 2024
8.2.5 Report
The following items shall be reported:
– diffuse illumination background: luminance level and relative spectral distribution (type of
the illuminant);
– measurement locations (directions) and focusing distance of the LMD;
– light output non-uniformity of the integrating sphere;
– luminous transmittance and spectral transmittance of the DUT applied with the white pattern
at each point;
– luminous transmittance and spectral transmittance of the DUT applied with the black pattern
at each point;
– eye point (eye relief) and the position of the z-axis;
– type of LMD and the entrance pupil size;
– correction methods for the measurement, if necessary, for example, the correction of the
luminance non-uniformity or the angle shall be applied.
8.3 Parameters related to virtual images
8.3.1 Ambient contrast ratio
8.3.1.1 General
The purpose of this method is to determine the ambient contrast ratio at the centre, sides and
corners of the virtual image for an AR type eyewear display by using the checkerboard patterns
under an ambient illumination background. The ambient illumination conditions can be provided
by the manufacturer or the supplier. If the eyewear display has ambient detection capability for
adjusting the luminance level of the virtual image, the ambient detection should be set in
accordance with the product specification.
8.3.1.2 Measuring conditions
a) The setup and light measuring devices (LMDs) shall be applied as in 8.2.2.
b) Test patterns: the checkerboard patterns with centre white and centre black shall be applied.
c) Measurement locations: nine points as shown in IEC 61345-20-10:2019, 5.4, are applied. H
and V represent the horizontal and vertical angles of the FOV for the virtual image.
8.3.1.3 Procedures
The spectral transmittance T (λ, i) of the white blocks and T (λ, i) of the black blocks at point
W K
P (i = 0 to 8) for the DUT with checkerboard patterns can be obtained as in 8.2.
i
In the dark background, apply 5 × 5 checkerboard patterns as shown in IEC 61345-20-10:2019,
5.3.2, with centre white and centre black, respectively, to measure the spectral radiance of the
virtual image at point P (i = 0 to 8), L (λ, i) and L (λ, i).
i D,K D,W
8.3.1.4 Calculation
a) Ambient luminance level L and relative spectral distribution S(λ) of the illumination
s
background defined in 6.2, shall be specified by the manufacturer or supplier.
b) Ambient contrast ratio of the DUT at point P (i = 0 to 8) can be calculated as follows:
i
Li
()
Amb,W
CR (i)= (5)
A
Li
()
Amb,K
where
L (i) is the luminance at point P (i = 0 to 8) under the illumination for the DUT with
Amb,K i
the black block; it is the total luminance measured from the LMD (both the virtual
image and ambient background illumination);
L (i) is the luminance at point P (i = 0 to 8) under the illumination for the DUT with
Amb,W i
the white block; it is the total luminance measured from the LMD (both the virtual
image and ambient background illumination).
L i=683· L (λ,i)+∆T (λ,iL)· ()λ ·V()λλ·
() (6)
( )
Amb,W ∑ D,W W s
where
T (λ, i) is the spectral transmittance of the white block;
W
L (λ, i) is the spectral radiance at point P (i = 0 to 8) under the dark background for the
D,W i
DUT with the white block;
L (λ) is the spectral radiance of the specified standard illumination background, given
s
in Formula (7).
LS· ()λ
s
L ()λ =
s
(7)
683· S()λV· ()λ ·∆λ
∑
where
L is the ambient luminance of the illumination background (see 6.2).
s
L i=683· L ()λλ,iT+ (),iL· (λ) ·V()λλ·∆
() ( ) (8)
∑
Amb,K D,K K s
where
T (λ, i) is the spectral transmittance of the black block;
K
L (λ, i) is the spectral radiance at point P (i = 0 to 8) under the dark background for the
D,K i
DUT with the black block.
Finally, the averaged ambient contrast ratio, CR , is given as:
A,av
CR = CR ()i (9)
∑
A,av A
i=0
NOTE L (i) and L (i) can be measured directly instead of measuring L (λ, i), L (λ, i), T (λ, i) and
Amb,W Amb,K D,W D,K W
T (λ, i), when the specified standard illumination background is applied in the measurement.
K
– 18 – IEC 63145-22-20:2024 © IEC 2024
8.3.1.5 Report
The following items shall be reported:
– ambient illuminating conditions: the luminance level and relative spectral distribution;
– ambient contrast ratio of the DUT at each point;
– ambient contrast ratio at the centre, and averaged ambient contrast ratio;
– test patterns;
– eye point (eye relief), and the position of the z-axis;
– type of LMD and the aperture size;
– correction methods fo
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