IEC 63145-20-20:2019

IEC 63145-20-20 ®
Edition 1.0 2019-09
INTERNATIONAL
STANDARD
Eyewear display –
Part 20-20: Fundamental measurement methods – Image quality
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IEC 63145-20-20 ®
Edition 1.0 2019-09
INTERNATIONAL
STANDARD
Eyewear display –
Part 20-20: Fundamental measurement methods – Image quality

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.180.99; 31.120 ISBN 978-2-8322-7352-4

– 2 – IEC 63145-20-20:2019 © IEC 2019
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/unit symbols) . 7
4 Standard measurement conditions . 7
4.1 Standard environmental conditions . 7
4.2 Power supply . 7
4.3 Warm-up time . 8
4.4 Dark room conditions . 8
5 Measurement systems . 8
5.1 Standard coordinate system . 8
5.2 Measurement equipment . 9
5.2.1 Light measuring device (LMD) . 9
5.2.2 Stage conditions . 11
5.2.3 Setup conditions . 11
5.3 Test patterns. 13
5.3.1 General . 13
5.3.2 Checkerboard pattern . 13
5.3.3 Solid colour patterns . 13
5.3.4 Test patterns for Michelson contrast . 13
5.4 Measurement points . 14
6 Measurement methods for image quality . 15
6.1 General . 15
6.2 Preparation . 15
6.3 Distortion . 15
6.3.1 General . 15
6.3.2 Procedure . 16
6.3.3 Calculation . 17
6.3.4 Report . 18
6.4 Colour registration error . 18
6.4.1 General . 18
6.4.2 Procedure . 18
6.4.3 Calculation . 19
6.4.4 Report . 19
6.5 Michelson contrast . 19
6.5.1 General . 19
6.5.2 Procedure . 19
6.5.3 Calculation . 20
6.5.4 Report . 20
6.6 Focal distance (dioptre) . 20
6.6.1 General . 20
6.6.2 Procedure . 21
6.6.3 Calculation . 22

6.6.4 Report . 22
6.7 FOV based on Michelson contrast . 22
6.7.1 General . 22
6.7.2 Procedure . 22
6.7.3 Calculation . 23
6.7.4 Report . 23
6.8 Eye-box based on Michelson contrast . 23
6.8.1 General . 23
6.8.2 Procedure . 23
6.8.3 Calculation . 24
6.8.4 Report . 25
Bibliography . 26

Figure 1 – Spherical coordinate system . 9
Figure 2 – Three-dimensional Cartesian coordinate system . 9
Figure 3 – Example of LMD structure . 10
Figure 4 – Examples of measurement setup. 12
Figure 5 – Example of 5 x 5 checkerboard pattern . 13
Figure 6 – Example of Michelson contrast test pattern . 14
Figure 7 – Measuring points for the centre- and multi-point measurement . 14

Table 1 – Letter symbols (symbols for quantities, and units) . 7

– 4 – IEC 63145-20-20:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EYEWEAR DISPLAY –
Part 20-20: Fundamental measurement methods –
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 co-operation on all questions concerning standardization in the electrical and electronic fields. To
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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 63145-20-20 has been prepared by IEC technical committee
TC 110: Electronic displays.
The text of this International Standard is based on the following documents:
FDIS Report on voting
110/1110/FDIS 110/1139/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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 "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.
A bilingual version of this publication may be issued at a later date.

– 6 – IEC 63145-20-20:2019 © IEC 2019
EYEWEAR DISPLAY –
Part 20-20: Fundamental measurement methods –
Image quality
1 Scope
This part of IEC 63145 specifies the standard measurement conditions and measurement
methods for determining the image quality of eyewear displays. This document is applicable
to non-see-through type (virtual reality “VR” goggle) and see-through type (augmented reality
“AR” glasses) eyewear displays using virtual image optics.
Contact-lens type displays and retina direct projection displays are out of the scope of this
document.
NOTE See IEC TR 63145-1-1 [1] for eyewear displays, ISO 9241-302:2008, 3.5.45, for see-through types.
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 63145-20-10:– , Eyewear display – Part 20-10: Fundamental measuring methods –
Optical properties
ISO 9241-302:2008, Ergonomics of human-system interaction – Part 302: Terminology for
electronic visual displays
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 63145-20-10 and
ISO 9241-302 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE 1 Terms related to eyewear displays will be defined in specific projects.
NOTE 2 Some terms relating to eyewear displays are given in IEC TR 63145-1-1 [1].
____________
Numbers in square brackets refer to the Bibliography.
Under preparation. Stage at the time of publication: IEC FDIS 63145-20-10:2019.

3.2 Abbreviated terms
AR augmented reality
CCD charge-coupled device detector
CPD cycles per degree
DUT device under test
FOV field of view
LMD light measuring device
VR virtual reality
3.3 Letter symbols (quantity symbols/unit symbols)
The letter symbols for eyewear displays are shown in Table 1
Table 1 – Letter symbols (symbols for quantities, and units)
Quantities Symbols and units
Measuring point (i = 0: centre) P
i
Luminance at P L (cd/m )
i vi
Distortion at the corner
δ (%)
vh
Colour registration error for primary colour ε (degree)
vh, colour
Michelson contrast C
m
Maximum luminance L (cd/m )
vM
Minimum luminance L (cd/m )
vm
Spatial frequency (CPD) f (1/degree)
CPD
Focal distance at P γ (m)
i i
Dioptre at P D (1/m)
i i
4 Standard measurement conditions
4.1 Standard environmental conditions
Unless otherwise specified, all tests and measurements for eyewear displays shall be carried
out after sufficient warm-up time for the illumination sources and DUT (see 4.3), under the
following standard environmental conditions:
• temperature 22 °C to 28 °C,
• relative humidity 25 % to 85 %, and
• 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 performances of the DUT, the power supply for driving the DUT shall
be adjusted according to the specification of the DUT.
NOTE When the DUT is driven by a battery, it is less susceptible to power supply fluctuations.

– 8 – IEC 63145-20-20:2019 © IEC 2019
4.3 Warm-up time
The optical performances of DUTs are affected by the transient temperature behaviour of the
device. It takes a certain time for the luminance output of the DUT to reach the steady state. If
the luminance output is not within a ±3 % variation, it shall be reported. All measuring
conditions shall be kept constant during the measurements.
NOTE If the measuring result does not become a steady state, it might be influenced by the output fluctuation of
the DUT and/or the fluctuation of the LMD such as noise.
4.4 Dark room conditions
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
To indicate the size and position of a virtual image, a spherical coordinate system of elevation
(latitude) and azimuth (longitude) shall be used in the measurements; the polar axis is
vertically oriented as shown in Figure 1. The angles measured in the vertical half plane of
data are elevation angles, denoted as α, and the horizontal angles to the half plane are
azimuth angles, denoted as Ψ. The origin direction (α = 0, Ψ = 0) of the spherical coordinate
system shall be coincident with the optical axis of the DUT.
To indicate the positional relationship among the eye-box, reference point on the DUT, eye
point and eye relief of the DUT, entrance pupil of the LMD and so on, a three-dimensional
Cartesian coordinate system (x, y, z) shall be used, as shown in Figure 2. Unless specified
otherwise, the eye point of the DUT is placed in the centre of the entrance pupil of the eye,
which is in the centre of the iris. The eye point defines the origin of the coordinate system.
The manufacturer or supplier of the DUT shall specify the distance between a reference point
on the DUT and the eye point. The eye relief is defined as the distance from the cornea of the
eye to the closest optical element of the DUT.
The origins of both the spherical coordinate system and the Cartesian coordinate system shall
be located at the eye point.
NOTE In the case of a binocular eyewear display, the left eye can be used as the origin of the Cartesian
coordinate system.
Figure 1 – Spherical coordinate system

NOTE This figure is an example of the eye pupil adjusting to the eye point, which is the origin position.
Figure 2 – Three-dimensional Cartesian coordinate system
5.2 Measurement equipment
5.2.1 Light measuring device (LMD)
5.2.1.1 General
The configurations and operating conditions of the equipment should comply with the
structures specified in each item. To ensure accurate measurements, the following
requirements shall be applied. Otherwise, the differences shall be noted in the report.
ISO/CIE 19476 [4] describes the LMD evaluation procedures.
The optics of an LMD (a spot LMD or a 2D imaging LMD) shall be equivalent to the human
eye, as shown in Figure 3. The LMD shall be equipped with an optical finder or a digital
viewfinder. The position of the entrance pupil (aperture) of the LMD shall be provided by the
manufacturer or the supplier. The entrance pupil size of the LMD should be set between 2 mm
and 5 mm, and shall be smaller than the light ray of the DUT. The LMD to measure the optical
characteristics such as luminance and colour shall be calibrated with the appropriate
photometric or spectrometric standards. The LMD should be carefully checked before
measurements, considering the following points:
• sensitivity of the measured quantity to the measuring light;
• errors caused by the veiling glare and lens flare (i.e., stray light in the optical system);
• timing of data-acquisition, low-pass filtering and aliasing-effects;
• linearity of detection and data conversion;
• measurement field size.
– 10 – IEC 63145-20-20:2019 © IEC 2019
NOTE See IEC TR 63145-1-1:2018, 6.2 [1].

Figure 3 – Example of LMD structure
5.2.1.2 Spectrometer-type LMD
When a spectrometer-type LMD such as a spectroradiometer is used, the wavelength range
shall be at least 380 nm to 780 nm, the spectral bandwidth shall be 5 nm or smaller, and the
wavelength accuracy shall be 0,3 nm or smaller.
5.2.1.3 Filter-type LMD for measuring luminance
When a filter-type LMD such as a luminance meter is used, to ensure the luminance accuracy
for the intended DUT light sources, its spectral responsivity should comply with the spectral
luminous efficiency for CIE photopic vision or it should be compared with a calibrated
spectrometer. The spectral mismatch correction factor can be applied, if necessary.
NOTE CIE-f ’ indicates the spectral mismatch function between the spectral responsivity of the filter-type LMD
and the CIE photopic luminous efficiency function. Details of the spectral mismatch correction factor are given in
ISO19476 [4].
5.2.1.4 Filter-type LMD for measuring colour
When a filter-type LMD such as a colorimeter is used to ensure the colour accuracy for the
intended DUT light sources, its spectral responsivity should comply with the CIE colour-
matching functions for the CIE 1931 standard colorimetric observer (see ISO 11664-1 [3]) or it
should be compared with a calibrated spectrometer. The colour correction factors can be
applied, if necessary. The filter-type LMD shall not be used for absolute colour quantities, but
for relative colour quantities such as colour uniformity.
5.2.1.5 2D imaging LMD
The 2D imaging LMD (using a two-dimensional sensor such as a CCD) is a kind of a filter-
type LMD. The performances of the 2D imaging LMD shall comply with 5.2.1.3 and 5.2.1.4.
The valid measurement field angle of the 2D imaging LMD shall be confirmed and the
peripheral image of the 2D imaging LMD shall confirm the absence of vignetting. The number
of pixels of the 2D imaging LMD should not be less than four times the sub-pixels number
within the measurement field.
NOTE 1 The measurement field of some 2D imaging LMDs is affected by the smaller entrance aperture.
NOTE 2 The 2D imaging LMD using a colour filter array might cause moiré.

5.2.2 Stage conditions
5.2.2.1 General
The stage shall be used to realize the coordinate system specified in 5.1. The stage should be
constructed with the equivalent of a biaxial goniometer and an orthogonal three-axis
translation stage.
5.2.2.2 Goniometer
A biaxial goniometer shall be assembled to be capable of measuring the azimuth (horizontal)
and elevation (vertical) angles in the spherical coordinate system as shown in Figure 1.
Examples of a five-axis stage are shown in 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.
5.2.2.3 Translation stage
An orthogonal three-axis translation stage is assembled 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 examples shown in Figure 4. The translation accuracy
should be no less than 0,05 mm.
5.2.3 Setup conditions
The DUT shall be mounted on a stable platform to ensure image stability. The LMD position
relative to the DUT shall be moved, and it can use a five-axis system (a biaxial goniometer
and orthogonal three-axis translation stage). Examples of a measuring setup are shown in
Figure 4. The eye point of the DUT shall match the origin of the biaxial goniometer. The
optical axis of the DUT which is decided by the 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.
To measure the conditions viewed from the front side, when the DUT does not suppose a
change of gaze angle (eye rotation), the origin of a biaxial goniometer shall be assumed as
the entrance pupil of the eye (eye point), not the rotation centre of the eyeball (eye
movement). When the origin of the biaxial goniometer does not match the eye point of the
DUT, the coordinate correction shall be required and shall be reported. When the DUT
supposes a change of the gaze angle, the detailed information such as the position of the
rotation centre shall be specified by the manufacturer or the supplier and shall be reported.
NOTE 1 The cornea position is about 3 mm in front of the iris position. Some optical designs are used based on
the cornea position.
NOTE 2 The rotation centre of the eyeball is located about 10 mm behind the iris.

– 12 – IEC 63145-20-20:2019 © IEC 2019

a) LMD mounted on a biaxial goniometer and orthogonal three-axis translation stage

b) DUT mounted on a biaxial goniometer and an orthogonal three-axis translation stage
NOTE 1 When the LMD is installed on the biaxial goniometer, the elevation stage is set on the azimuth stage.
NOTE 2 Some eyewear displays change their virtual image depending on their orientation.
Figure 4 – Examples of measurement setup

5.3 Test patterns
5.3.1 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 conventional display, the boundary of the display area is not clear, and the choice of test pattern
might affect the measurement results.
5.3.2 Checkerboard pattern
The checkerboard pattern as shown in Figure 5 should be used to measure the applicable
properties, and can be used for alignment of the DUT and LMD optics. The checkerboard
pattern with crosses whose example is specified in ISO 9241-305 [2], should also be used for
alignment of the DUT and LMD optics. Both patterns of white and black at the centre can be
used. Usually, a white and black checkerboard pattern is used, but a checkerboard pattern of
another colour (red, green, blue and so on) and black can be used if necessary.

NOTE The 5 x 5 checkerboard pattern is helpful in navigating across the virtual image and focusing
...