Electronic displays - Part 3-1: Evaluation of optical performances - Colour difference based viewing direction dependence

IEC TS 62977-3-1:2019(E) specifies the evaluation method of the viewing direction characteristics of electronic display devices under dark-room conditions. More specifically, this document focuses on the evaluation of the viewing direction characteristics based on colour difference.
This document applies to colour matrix displays, which are based on transmissive or emissive technologies.

General Information

Status
Published
Publication Date
12-Feb-2019
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
13-Feb-2019
Ref Project

Buy Standard

Technical specification
IEC TS 62977-3-1:2019 - Electronic displays - Part 3-1: Evaluation of optical performances - Colour difference based viewing direction dependence
English language
31 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

IEC TS 62977-3-1
Edition 1.0 2019-02
TECHNICAL
SPECIFICATION
colour
inside
Electronic displays –
Part 3-1: Evaluation of optical performances – Colour difference based viewing
direction dependence
IEC TS 62977-3-1:2019-02(en)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2019 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC

copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org

The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,

variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English

committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.

and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary

details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and

once a month by email. French extracted from the Terms and Definitions clause of

IEC publications issued since 2002. Some entries have been

IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and

If you wish to give us your feedback on this publication or CISPR.
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
---------------------- Page: 2 ----------------------
IEC TS 62977-3-1
Edition 1.0 2019-02
TECHNICAL
SPECIFICATION
colour
inside
Electronic displays –
Part 3-1: Evaluation of optical performances – Colour difference based viewing
direction dependence
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120; 21.260 ISBN 978-2-8322-6515-4

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62977-3-1:2019  IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms, definitions and abbreviated terms ........................................................................ 7

3.1 General ................................................................................................................... 7

3.2 Abbreviated terms ................................................................................................... 7

4 Standard measuring equipment and coordinate system ................................................... 8

4.1 Light measuring device ........................................................................................... 8

4.2 Viewing direction coordinate system ....................................................................... 8

5 Measuring conditions ....................................................................................................... 9

5.1 Standard measuring environmental conditions ........................................................ 9

5.2 Power supply .......................................................................................................... 9

5.3 Warm-up time ......................................................................................................... 9

5.4 Standard measuring dark-room conditions .............................................................. 9

5.5 Standard set-up conditions ..................................................................................... 9

5.5.1 General ........................................................................................................... 9

5.5.2 Adjustment of display ...................................................................................... 9

6 Measurement methods .................................................................................................. 10

6.1 Measurement procedures ...................................................................................... 10

6.2 Test signals (test charts) ....................................................................................... 11

7 Calculation of chromaticity and colour difference ........................................................... 12

8 Reporting....................................................................................................................... 15

Annex A (informative) Perception of colour difference ......................................................... 19

Annex B (informative) Other attenuation factors .................................................................. 20

B.1 General ................................................................................................................. 20

B.2 Attenuation factors proposed ................................................................................ 20

Annex C (informative) Other parameters ............................................................................. 21

C.1 Measurement of half luminance angle ................................................................... 21

C.2 Measurement of gamma distortion from the viewing directions .............................. 21

Annex D (informative) Translation of RGB input signal to output colours ............................. 24

Annex E (informative) Simulation result of chromaticity error versus number of pixels

in the measurement area ...................................................................................................... 28

E.1 General ................................................................................................................. 28

E.2 Simulation conditions ............................................................................................ 28

E.3 Simulation result ................................................................................................... 29

Bibliography .......................................................................................................................... 31

θ and φ ................................................................. 8
Figure 1 – Illustration of viewing directions

Figure 2 – Measuring layout for horizontal viewing direction dependency .............................. 10

Figure 3 – Measuring layout for vertical viewing direction dependency .................................. 11

Figure C.1 – Test pattern for gamma measurement .............................................................. 22

Figure C.2 – Example of linear regression of log(△L ) versus log(△V ) in normal
j j

direction (0°) ......................................................................................................................... 23

Figure E.1 – Relative spectral radiance (left: LCD, right: OLED) ........................................... 28

---------------------- Page: 4 ----------------------
IEC TS 62977-3-1:2019  IEC 2019 – 3 –

Figure E.2 – Measuring area versus DUT pixels.................................................................... 29

Figure E.3 – Number of measuring pixels versus chromaticity error ...................................... 30

Table 1 – Measurement directions for TV in living rooms ...................................................... 11

Table 2 – Measurement directions for mobile displays .......................................................... 11

Table 3 – Input signal of 4 % window for viewing direction measurements ............................ 12

Table 4 – Attenuation factors ................................................................................................ 14

Table 5 – Parametric factors ................................................................................................. 15

Table 6 – Example of reporting format .................................................................................. 16

Table A.1 – Perception of colour difference ........................................................................... 19

Table B.1 –- Attenuation factors ............................................................................................ 20

Table C.1 – Worked-out example for gamma distortion from viewing direction ...................... 23

Table D.1 – Test colours ....................................................................................................... 24

Table D.2 – RGB translation values for 8-bit colour (BT.2020 colour reference) .................... 25

Table D.3 – RGB translation values for 10-bit colour (BT.2020 colour reference) .................. 26

Table D.4 – RGB translation values for 10 bit colour (BT.709 colour reference) .................... 27

Table E.1– DUT’s primary chromaticity and chromaticity area gamut (% NTSC) .................... 28

Table E.2 – Number of sub-pixels in the measurement area .................................................. 29

Table E.3 – Simulation result of chromaticity error (around 100 pixels) ................................. 29

---------------------- Page: 5 ----------------------
– 4 – IEC TS 62977-3-1:2019  IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRONIC DISPLAYS –
Part 3-1: Evaluation of optical performances – Colour difference based
viewing direction dependence
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

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

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.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC TS IEC 62977-3-1, which is a technical specification, has been prepared by IEC technical

committee 110: Electronic displays.
---------------------- Page: 6 ----------------------
IEC TS 62977-3-1:2019  IEC 2019 – 5 –
The text of this technical specification is based on the following documents:
Draft TS Report on voting
110/1003/DTS 110/1065/RVDTS

Full information on the voting for the approval of this technical specification 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 the parts in the IEC 62977 series, under the general title Electronic displays, can

be found on the IEC website.

Future documents in this series will carry the new general title as cited above. Titles of

existing standards in this series will be updated at the time of the next edition.

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.

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.
---------------------- Page: 7 ----------------------
– 6 – IEC TS 62977-3-1:2019  IEC 2019
INTRODUCTION

This document aims to provide a measurement method that determines the display angular

dependence after colour and white reference adaptation and provides an evaluation of

differences in a uniform colour space.

This document facilitates the cross-industry measurement of the viewing direction

dependence of colour displays. Several studies [6 to 9] have indicated that the contrast ratio

(CR > 10:1) is, from a visual quality point of view, not useful to determine the viewing direction

range for matrix displays. When colour differences are included in a viewing direction metric,

the correlation between the metric value and a visual assessment value is significantly

increased [10]. A more recent study [11] revealed that a metric, combining viewing-direction

related luminance degradation and colour deviation can accurately predict the relative change

in the visual assessment value. This information is the basis for the determination of the

viewing direction range, which has relevance from a visual quality point of view.

NOTE “Viewing direction range” is sometimes referred to as “viewing angle”. Although technically incorrect, for

legacy reasons the terms is considered equivalent.
———————
Numbers in square brackets refer to the Bibliography.
---------------------- Page: 8 ----------------------
IEC TS 62977-3-1:2019  IEC 2019 – 7 –
ELECTRONIC DISPLAYS –
Part 3-1: Evaluation of optical performances – Colour difference based
viewing direction dependence
1 Scope

This part of IEC 62977 specifies the evaluation method of the viewing direction characteristics

of electronic display devices under dark-room conditions. More specifically, this document

focuses on the evaluation of the viewing direction characteristics based on colour difference.

This document applies to colour matrix displays, which are based on transmissive or emissive

technologies.
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.
ISO 11664-1, Colorimetry – Part 1: CIE standard colorimetric observers
ISO 11664-4, Colorimetry – Part 4: CIE 1976 L*a*b* Colour space
ISO/CIE 11664-6:2014, Colorimetry – Part 6: CIEDE2000 Colour-difference formula
CIE 159, A colour appearance model for colour management systems: CIECAM02
CIE 168, Criteria for the evaluation of extended-gamut colour encodings
3 Terms, definitions and abbreviated terms
3.1 General
No terms and definitions are listed in this document.

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
3.2 Abbreviated terms
APL average pixel loading
CIE Commission Internationale de L’Eclairage (International Commission on
Illumination)
CIEDE2000 CIE 2000 delta-E colour difference system
CIELAB CIE 1976 (L*a*b*) colour space
CR contrast ratio
---------------------- Page: 9 ----------------------
– 8 – IEC TS 62977-3-1:2019  IEC 2019
DUT device under test
FWHM full-width-at-half-maximum
LMD light measuring device
LCD liquid crystal display
OLED organic light emitting diode
PDP plasma display panel
4 Standard measuring equipment and coordinate system
4.1 Light measuring device

The LMD shall be a luminance meter, colorimeter, or a spectroradiometer. For DUTs that

have a sharp spectral peak FWHM (i. e. smaller than 20 nm), such as laser displays, LCDs

with fluorescent lamp backlights, LEDs with narrow-peak phosphors, quantum-dot phosphors,

or narrow-spectrum OLEDs, a spectroradiometer should be used. A filter colorimeter should

generally not be used for light sources with sharp spectral peaks. If they are used, the

colorimeter shall be calibrated with a narrow bandwidth spectroradiometer to give the same

results for the specific spectrum. Report the spectroradiometer characteristics of the

spectroradiometer which is used for calibration. For light sources with sharp spectral peaks,

the maximum bandwidth of the spectroradiometer shall be ≤ 5 nm. The higher resolution

spectrometer produces a more accurate colour measurement, especially for lasers sources.

The spectroradiometer shall be capable of measuring spectral radiance over at least the 380

nm to 780 nm wavelength range, with a maximum bandwidth of 10 nm for smooth broadband

spectra (i.e. broad spectrum with no sharp spikes)[1].
4.2 Viewing direction coordinate system

The viewing direction is the direction under which the observer looks at the point of interest on

the device under test (DUT). During the measurement, the light-measuring device (LMD)

simulates the observer, by aiming the LMD at the point of interest on the DUT from the

viewing direction. The viewing direction is defined by two angles: the angle of inclination θ

(relative to the surface normal of the DUT) and the angle of rotation φ (also called azimuth

angle) as illustrated in Figure 1.
Figure 1 – Illustration of viewing directions θ and φ

Although the azimuth 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° the 12-

o'clock direction ("top"), φ = 180° the 9-o'clock direction ("left") and φ = 270° the 6-o'clock

direction ("bottom").
---------------------- Page: 10 ----------------------
IEC TS 62977-3-1:2019  IEC 2019 – 9 –

NOTE This coordinate system is defined by the angle of inclination and the angle of rotation (azimuth angle) in a

polar coordinate system.
5 Measuring conditions
5.1 Standard measuring environmental conditions
Measurements shall be carried out under the standard environmental conditions:
– temperature: 25 ºC ± 3 ºC
– relative humidity: 25 % to 85 %,
– atmospheric pressure: 86 kPa to 106 kPa.

When different environmental conditions are used, they shall be noted in the report.

5.2 Power supply
A driving power supply and driving signal equipment shall be used.
5.3 Warm-up time

Measurements shall start after the displays and measuring instruments achieve stability. The

DUT shall be turned on first and operated for at least 30 min prior to the measurement. Some

display technologies may require a loop of colour patterns rendered on the screen during the

warm-up period. Sufficient warm-up time has been achieved when the luminance of the test

feature to be measured varies by less than ±3 % over the entire measurement period (e.g.

uniformity measurements) for a given display image.
5.4 Standard measuring dark-room conditions

The luminance contribution from unwanted background illumination reflected off the test

display shall be less than 1/20 of the display’s black state luminance. The reflected

background luminance can often be estimated by turning off the display. When the reflected

background luminance and total (reflected plus black) luminance are greater than the

sensitivity of the LMD, then it is possible to calculate the black luminance by subtracting the

background luminance from the total luminance. If the reflected background luminance and

total luminance are similar to the sensitivity limit of the LMD, this shall be reported. In cases

where the display has a very low luminance black state, a stray light elimination tube (see

ISO 9241-305 [17]) should be used to minimize the contribution of the background

illumination [3]. This method can be used to estimate the reflected luminance from the black

state luminance.
NOTE Blackout curtains can be used to reduce the reflection from the DUT.
5.5 Standard set-up conditions
5.5.1 General

Standard set-up conditions are given below. Any deviations from these conditions shall be

reported.
5.5.2 Adjustment of display

The display shall be configured to the specified settings, and the settings recorded in the test

report. These settings shall be held constant for all measurements, unless stated otherwise. It

is important, however, to make sure that not only the adjustments are kept constant, but also

that the resulting physical quantities remain constant during the measurement. This is not

automatically the case because of, for example, warm-up effects or auto-dimming features.

Any automatic luminance or gain control shall be turned off. Otherwise it shall be noted in the

report. The ambient light (or brightness) control shall be turned off. If that is not possible, it is

---------------------- Page: 11 ----------------------
– 10 – IEC TS 62977-3-1:2019  IEC 2019

recommended to set it to turn on no lower than 300 lx to minimize the influence of the

brightness control. The state of the auto-light control shall be reported. In addition, if the

display exhibits image sticking and/or has an auto-dimming feature which reduces the display

luminance of a static image after a prolonged time, then at least an 8-s black frame shall be

rendered prior to rendering and measuring the desired test pattern. The measurements shall

before the dimming feature is triggered. When the display has the option to be
be completed

set for different viewing modes, the viewing mode shall be defined by the test specification

and used with consistency for all measurements. Additional viewing modes can also be

measured. The viewing mode used during testing shall be reported. The display should be

operated in a mode that does not have overscan.
6 Measurement methods
6.1 Measurement procedures

1) Render the specified test pattern with the required colour Q centred on the display screen.

Allow the luminance to stabilize.

2) Align the optical axis of the LMD in the specified direction relative to the display screen

and centred on the display screen.
3) Measure the tristimulus values X , Y , Z at the screen centre.
Q Q Q

4) Render the specified test pattern with the reference white pattern centred on the display

screen. Allow the luminance to stabilize.
5) Measure the tristimulus values X , Y , Z at the screen centre.
n n n
6) Repeat the measurement for additional colours.

7) Report the set-up conditions, the test pattern, the colour, and tristimulus values X , Y ,

Q Q
Z X , Y , Z at the specified colour Q, respectively.
Q n n n

To measure the viewing direction dependency, the centre of the screen is measured from the

horizontal, vertical, or diagonal viewing directions defined in each measurement method or

the relevant specification as shown in Figure 1. Instead of moving the LMD as indicated in

Figure 2a) and Figure 3a), the DUT can be tilted vertically or turned horizontally to be

measured as shown in Figure 2b) and Figure 3b). The recommended ranges of the direction

(θ) are shown in Table 1 and Table 2 for TV in living rooms and for mobile devices,

respectively. The horizontal and vertical measuring direction ranges shall be defined by the

supplier in the relevant specification, and shall be noted in the report. If the

customer/application requires additional direction ranges, they shall be applied and noted in

the report.
a) Motion of LMD (top view) b) Rotation of display (top view)
Figure 2 – Measuring layout for horizontal viewing direction dependency
---------------------- Page: 12 ----------------------
IEC TS 62977-3-1:2019  IEC 2019 – 11 –
a) Motion of LMD (side view) b) Tilt of display (side view)
Figure 3 – Measuring layout for vertical viewing direction dependency
Table 1 – Measurement directions for TV in living rooms
θ (degree) φ (degree)
Horizontal 0, ±15, ±30, ±45, ±60 0
Vertical 0, ±15, ±30 90
Diagonal 45 0, 45, 90, 135, 180, 225, 270 and 315
Table 2 – Measurement directions for mobile displays
θ (degree) φ (degree)
Horizontal 0, ±15, ±30, ±40, ±50 0
Vertical 0, ±15, ±30, ±40, ±50 90
Diagonal 30 0, 45, 90, 135, 180, 225, 270 and 315
6.2 Test signals (test charts)

The test pattern of the input video signal supplied to the DUT is a 4 % window area centred

on the screen with one of eleven test colours as described in Table 3The area outside the 4 %

window area shall be driven to the black level. The minimum DUT luminance with a 100 %

white input signal, i.e. R = G = B = 255 for an 8-bit signal, shall be 100 cd/m . The area

outside the 4 % window area shall be driven to the black level. If the 4 % window contains

fewer than 500 pixels, the window shall be chosen to contain at least 500 pixels. For

reference, see Annex E. Optionally, any additional test colours 12 to 15 in Table 3 may be

added.

NOTE The translation of the RGB input signal into output colours is described in Annex D.

---------------------- Page: 13 ----------------------
– 12 – IEC TS 62977-3-1:2019  IEC 2019
Table 3 – Input signal of 4 % window for viewing direction measurements
Colour Q 8-bit signal level (v) (BT2020 colour reference)
R G B
1 White 242 242 236
2 G
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.