IEC TR 62977-3-2:2016

Electronic display devices - Part 3-2: Evaluation of optical characteristics - Mura

IEC TR 62977-3-2:2016, which is a Technical Report, provides an optical measuring method of mura for electronic displays. It defines general measuring procedures for mura measurement and an evaluation method of electronic displays.

General Information

• Status: Withdrawn
• Publication Date: 06-Jan-2016
• Withdrawal Date: 30-Mar-2016
• ICS: 31.120 - Electronic display devices
• ICS: 31.260 - Optoelectronics. Laser equipment
• Technical Committee: TC 110 - Electronic displays
• Drafting Committee: PT 62977-3-2 - TC 110/PT 62977-3-2
• Current Stage: WPUB - Publication withdrawn
• Start Date: 18-Mar-2016
• Completion Date: 14-Feb-2026

Standards Content (Sample)

IEC TR 62977-3-2 ®
Edition 1.0 2016-01
TECHNICAL
REPORT
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Electronic display devices –
Part 3-2: Evaluation of optical characteristics – Mura
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IEC TR 62977-3-2 ®
Edition 1.0 2016-01
TECHNICAL
REPORT
colour
inside
Electronic display devices –
Part 3-2: Evaluation of optical characteristics – Mura

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.120; 31.260 ISBN 978-2-8322-3118-0

– 2 – IEC TR 62977-3-2:2016 © IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Standard measuring conditions . 8
4.1 Standard measuring conditions . 8
4.1.1 Standard measuring environmental conditions . 8
4.1.2 Standard measuring darkroom conditions . 8
4.2 Light measuring device (LMD) . 8
4.3 Measuring setup . 9
4.4 Test signal . 9
4.5 Measuring conditions . 10
5 Standard evaluation method . 10
5.1 Measurement data processing method . 10
5.2 Measurement data processing flow . 10
5.2.1 General . 10
5.2.2 Median filter process . 11
5.2.3 Transformation to opponent colour space from CIE XYZ . 12
5.2.4 Convolution with the contrast sensitivity function (CSF) of the human
visual system . 12
5.2.5 Transformation to CIE XYZ from the opponent colour space . 12
5.2.6 Transformation to CIELAB from CIE XYZ . 12
5.2.7 a* correction . 13
5.3 Mura evaluation method . 13
5.3.1 General . 13
5.3.2 Lightness mura evaluation . 13
5.3.3 Chroma mura evaluation . 15
5.3.4 Mura evaluation . 16
5.3.5 Measurement report . 16
6 Actual example . 17
6.1 General . 17
6.2 Evaluation objects . 17
6.3 Subjective evaluation . 17
6.4 Evaluation by the method indicated inthis document using apparatus. 18
6.5 Correlation between subjective evaluation and mura evaluation value . 19
Annex A (informative) S-CIELAB model . 20
A.1 General . 20
A.2 S-CIELAB model . 20
A.3 Spatial sensitivity function model (two-dimensional CSF model). 20
Annex B (informative) Type of mura . 24
B.1 General . 24
B.2 Classification of mura . 24
Annex C (informative) Use case of a mura evaluation value . 26
C.1 General . 26

C.2 Example of a use case of a mura evaluation value . 26
Annex D (informative) Various mura measurement methods . 27
D.1 General . 27
D.2 Comparison of mura evaluation standards . 27
Bibliography . 28

Figure 1 – Measuring layout . 9
Figure 2 – Example of input signal . 10
Figure 3 – Measurement data processing flow adopting the S-CIELAB model . 11
Figure 4 – Concept diagram of real-space information integration . 14
Figure 5 – 3 × 3 neighbourhood domain . 15
Figure 6 – Evaluation objects in a dark room . 17
Figure 7 – CSF filter images in opponent colour space . 18
Figure 8 – Correlation of mura evaluation value and ITU-R subjective evaluation
values . 19
Figure A.1 – Flowchart of S-CIELAB calculation . 20
Figure A.2 – Two-dimensional CSF model . 21
Figure A.3 – Examples of the convolution of a two-dimensional CSF filter for illusion . 23
Figure B.1 – Classification of mura by forms and/or causes . 25

Table 1 – Example of reported criteria of two-dimensional LMD . 9
Table 2 – Example of measurement results for a display screen uniformity . 16
Table 3 – ITU-R quality and impairment scales . 17
Table 4 – Subjective evaluation results . 18
Table 5 – Evaluation results by apparatus . 19
Table A.1 – Parameters for each axis of the opponent colour space . 21
Table C.1 – Example of a use case of a mura evaluation value . 26
Table C.2 – Example of subjects to evaluate . 26
Table D.1 – Comparison chart of various mura measurement standards . 27

– 4 – IEC TR 62977-3-2:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRONIC DISPLAY DEVICES –
Part 3-2: Evaluation of optical characteristics – Mura

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
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indispensable for the correct application of this publication.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 62977-3-2, which is a technical report, has been prepared by IEC technical
committee 110: Electronic display devices.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
110/674A/DTR 110/701A/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 62977 series, published under the general title Electronic display
devices, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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
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– 6 – IEC TR 62977-3-2:2016 © IEC 2016
INTRODUCTION
Electronic displays, for example liquid crystal displays (LCDs), plasma display panels (PDPs),
organic light emission displays (OLEDs), and so on, have grown popular as displays for high-
quality images. It is therefore increasingly important to measure the image quality of
electronic displays. One factor degrading the image quality is non-uniformity, known as ‘mura’.
The mura is classified into three types. The first is luminance mura, the second is colour mura.
The third is called merely “mura” and includes luminance mura and colour mura
simultaneously. It is impossible to recognize luminance mura and colour mura as completely
separate objects.
Various measurement methods about luminance mura and colour mura have been reported in
various academic conferences. There are also some standards for these mura. For example,
uniformity of luminance and chromaticity are specified in IEC IEC 61747-30-1, SEMU (SEMI
mura) is specified in SEMI D31-0213 and uniformity measurement is specified in IDMS
ver.1.03 sec. 8. However there is no report which clearly provides the quantitative method for
the mura that is called merely “mura” (see Annex D).
Therefore the majority of electronic display manufacturers are still using the limit sample for
visual inspection.
This Technical Report, which intends to verify one mura measurement method, shows the
detailed mura measurement method and its inspection experiment results.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is
claimed that compliance with this document may involve the use of a patent.
IEC takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the IEC that he/she is willing to negotiate licences
either free of charge or under reasonable and non-discriminatory terms and conditions with
applicants throughout the world. In this respect, the statement of the holder of this patent right
is registered with IEC. Information may be obtained from:
Sony Corporation
1-7-1 Konan, Minato-ku, Tokyo, 108-0075 Japan
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those identified above. IEC shall not be held responsible for
identifying any or all such patent rights.
ISO (www.iso.org/patents) and IEC (http://patents.iec.ch) maintain on-line database of patents
relevant to their standards. Users are encouraged to consult the databases for the most up to
date information concerning patents.

ELECTRONIC DISPLAY DEVICES –
Part 3-2: Evaluation of optical characteristics – Mura

1 Scope
This part of IEC 62977, which is a Technical Report, provides an optical measuring method of
mura for electronic displays. It defines general measuring procedures for mura measurement
and an evaluation method of electronic displays.
2 Normative references
The following documents, in whole or in part, are referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
Void.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
lightness mura
luminance unevenness whose lightness differs partially from the background lightness of a
display screen with the exception of pixel defects
3.2
chroma mura
colour unevenness whose chroma differs partially from the background of a display screen
with the exception of pixel defects
3.3
mura
both luminance and colour unevenness whose lightness and chroma differ partially from the
background of a display screen with the exception of pixel defects
Note 1 to entry: In general, lightness mura and chroma mura exist simultaneously. Mura evaluation shows the
degree of screen uniformity considering how both lightness mura and chroma mura affect human perception.
3.4
lightness edge area
ratio of lightness gradient area that is rapidly changed lightness to whole screen area
3.5
lightness mura area
area of uneven lightness that is bright or dark regions against the background of a display
screen
3.6
maximum lightness difference
*
maximum lightness difference from the average L of a whole display screen

– 8 – IEC TR 62977-3-2:2016 © IEC 2016
3.7
chroma edge area
ratio of the chroma gradient area that is rapidly changed from the chroma to the whole screen
area
3.8
chroma mura area
area of uneven chroma that is coloured regions against the background of a display screen
3.9
maximum chroma
*
maximum C value in a whole display screen
3.10
opponent colour space
three dimensions that are described as w/k, r/g, and b/y channels
Note 1 to entry: The w/k channel is a luminance component. The r/g and b/y channels are a chromaticity
component of red to green, blue to yellow, respectively.
4 Standard measuring conditions
4.1 Standard measuring conditions
4.1.1 Standard measuring environmental conditions
The standard measuring environmental conditions specified in IEC 62341-6-1:2009, 5.1, should
be applied. [1]
4.1.2 Standard measuring darkroom conditions
The standard measuring darkroom conditions specified in IEC 62341-6-1:2009, 5.2, should be
applied. [1]
4.2 Light measuring device (LMD)
The LMD used for measurements of the displays should be checked for the following criteria
and specified accordingly:
• sensitivity of the measured quantity;
• errors caused by veiling glare and lens flare (i.e. stray light in optical system);
• errors caused by camera noise (i.e. dark charge noise of a charge coupled device (CCD));
• timing of data-acquisition and aliasing-effects;
• linearity of detection and data conversion;
• resolution when using a two-dimensional LMD.
A two-dimensional LMD such as a CCD area detector should be used for these measurements.
When using a two-dimensional LMD, it should be calibrated, so that the measurement results
correspond to those by the point-measurement LMD.
A two-dimensional LMD measures a map of luminance and/or colour coordinate values over
the measurement area of the screen. The specification of the LMD used should be noted in
the report as shown in Table 1 for example.
___________
Numbers in square brackets refer to the Bibliography.

It is important to avoid moiré and flicker effect when using a two-dimensional LMD. If a moiré
pattern appears in the image, the measuring conditions specified in IDMS version 1.03 Sec.
8.2 should be applied. The measuring condition specified in IDMS ver. 1.03 A4.2.1 should be
applied to avoid the flicker effect. [3]
NOTE 1 The point-measurement LMD measures the luminance and/or colour coordinate at each measurement
point on the screen. A two-dimensional LMD measures the map of luminance and/or colour coordinate over the
measurement area of the screen.
NOTE 2 A point-measurement LMD usually has higher sensitivity than a two-dimensional LMD. A two-dimensional
LMD measures the uniformity of the measuring area more easily than a point-measurement LMD.
Table 1 – Example of reported criteria of two-dimensional LMD
CCD resolution (measurement points)
980 × 980
2 2
Luminance range 0,05 cd/m to 100 000 cd/m (with ND filter)
Wavelength range 380 nm to 780 nm
System accuracy Luminance variation ±3 %
Colour coordinates (x, y)
±0,005
Colorimetric filters CIE1931 matched colour filters

4.3 Measuring setup
The measuring layout is shown in Figure 1.
The LMD should be set at a proper field angle and distance to be able to take the whole
screen area.
Display screen
Display screen
LMD
LMD
Screen
centre
Centre line
Measuring distance
Measuring distance
(a) Side view (b) Top view
IEC
Figure 1 – Measuring layout
4.4 Test signal
A full white or gray signal is input into a display. The input signal level is determined by an
evaluator and it should be noted in the measurement report.
The signal level should be specified at 0 %, 20 %, 50 %, 100 % of full white (see Figure 2).

– 10 – IEC TR 62977-3-2:2016 © IEC 2016
(a) 100 % of (b) 50 % of (c) 20 % of (d) 0 % of
full white  full white  full white  full white

IEC
Figure 2 – Example of input signal
4.5 Measuring conditions
The measuring conditions are as follows:
a) The shutter speed (exposure time) of the LMD should be determined so as to be
synchronized with the display (or backlight) scan timing.
b) The diaphragm stop of the LMD should be determined so as to obtain the proper
saturation level of the charged capacity of the image sensor (CCD, complementary metal
oxide semiconductor (CMOS)).
The evaluator should specify the factors of noise in the measuring conditions and strive to
minimize those effects on the measurement data.
5 Standard evaluation method
5.1 Measurement data processing method
The measurement data should be outputted as three maps of CIE tristimulus values (X, Y, Z)
using the two-dimensional LMD constructed in a CCD area detector and with CIE 1931
matched colour filters.
5.2 Measurement data processing flow
5.2.1 General
The measurement data processing flow is shown in Figure 3. The data is processed based on
the S-CIELAB model (see Annex A).

XYZ
Median filter
process
w/k r/g b/y
Fourier Fourier Fourier
Transform Transform Transform
Multiplication Multiplication Multiplication
CSF filter CSF filter CSF filter
Inversed Inversed Inversed
Fourier Fourier Fourier
Transform Transform Transform
w/k r/g b/y
XYZ
*
CIELAB a correction
* *
L C
Maximum
Lightness Lightness mura Chroma edge Chroma Maximum
lightness
edge area area area mura area chroma value
difference
Lightness mura Chroma
evaluation
mura evaluation
Mura
evaluation
IEC
Figure 3 – Measurement data processing flow adopting the S-CIELAB model
5.2.2 Median filter process
The measurement data should be processed with a median filter to eliminate the noise of the
LMD or the measuring conditions or any other factors.
It is recommended to consider which filter size should be used in accordance with the noise
level. The amount of median filtering will affect the spatial frequency analysis. To minimize its
impact, a small window size should be selected. For example, a (3 × 3) pixels or (5 × 5) pixels
window size minimizes this impact. By selecting these sizes, the elimination of t
...