Background Statement for SEMI Draft Document 4999A
New Standard: TEST METHODS FOR OPTICAL PROPERTIES OF
ELECTRONIC PAPER DISPLAYS
Notice: This background statement is not part of the balloted item. It is provided solely to assist
the recipient in reaching an informed decision based on the rationale of the activity that preceded
the creation of this Document.
Notice: Recipients of this Document are invited to submit, with their comments, notification of
any relevant patented technology or copyrighted items of which they are aware and to provide
supporting documentation. In this context, “patented technology” is defined as technology for
which a patent has issued or has been applied for. In the latter case, only publicly available
information on the contents of the patent application is to be provided.
Background
Since electronic paper displays are reflective and bistable displays, illumination conditions and measuring
geometries affect the results of optical properties measurements. As electronic paper displays are
increasing in popularity, suitable standardized measurement methods should be proposed to evaluate the
optical performance of electronic paper displays.
Review and Adjudication Information
Group:
Date:
Time &
Timezone:
Location:
City,
State/Country:
Leader(s):
Task Force Review
e-Paper Displays Task Force
Feb. 23, 2012
1:30 p.m. & GMT+8
Committee Adjudication
Taiwan FPD Committee
March, 2012
1:30 p.m. & GMT+8
Rm.223, Bldg. 16, 321, Kuang Fu Rd, Sec. 2 Rm.223, Bldg. 16, 321, Kuang
Fu Rd, Sec. 2
Hsinchu, Taiwan
Hsinchu, Taiwan
Hsiu-Ju Tsai (ITRI, sarahtsai@itri.org.tw)
Tzeng-Yow Lin (CMS/ITRI)
Hsin-Hong Chen (AUO,
Jia-Ming Liu (TDMDA)
HsinHong.Chen@auo.com)
Hsin-Tao Huang (E Ink, hsintaoh@eink.com)
Catherine Chang
Standards Staff: Catherine Chang (cchang@semi.org)
(cchang@semi.org)
This meeting’s details are subject to change, and additional review sessions may be scheduled if necessary. Contact
Standards staff for confirmation.
Telephone and web information will be distributed to interested parties as the meeting date approaches. If you will
not be able to attend these meetings in person but would like to participate by telephone/web, please contact
Standards staff.
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DRAFT
SEMI Draft Document 4999A
New Standard: TEST METHODS FOR OPTICAL PROPERTIES OF
ELECTRONIC PAPER DISPLAYS
1 Purpose
1.1 Electronic paper displays use reflective technology to create images and need no power to hold images because
of their bistable nature. Since there are more and more applications of electronic paper displays on the market
nowadays, such as e-Book readers, electronic shelf labels, and e-Signage, it is necessary to standardize the test
methods for measuring optical properties of electronic paper displays.
2 Scope
2.1 This standard is applicable to measurement for optical properties of electronic paper displays under diffuse or
directional illumination.
NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their
use. It is the responsibility of the users of the Documents to establish appropriate safety and health practices, and
determine the applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 This standard is suitable for use with electrophoretic displays, cholesteric-LCDs, and MEMs-based interference
displays, which are reflective and bistable electronic paper displays.
4 Referenced Standards
4.1 CIE Standard1
CIE 15:2004 3rd edition — Colorimetry
4.2 VESA Standard2
VESA 2.0 — Flat Panel Display Measurements Standard
4.3 IEC Standard3
IEC 61747-6-2 — Measuring Methods for Liquid Crystal Display Modules – Reflective Type
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 Abbreviations and Acronyms
5.1.1 DUT — Display Under Test
5.1.2 LMD — Light-Measuring Device
5.2 Definitions
5.2.1 bistability — ability to hold the image without applied power.
5.2.2 contrast ratio — ratio of the reflectance factor of the white state to that of the black state.
5.2.3 ghosting — an image sticking phenomenon of the previous image on the screen after the image is changed.
1
International Commission on Illumination, http://www.cie.co.at/
2
Video Electronics Standards Association, http://www.vesa.org/
3
International Electrotechnical Commission, 3 rue de Varembé, Case Postale 131, CH-1211 Geneva 20, Switzerland; Telephone:
41.22.919.02.11, Fax: 41.22.919.03.00, http://www.iec.ch
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
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5.2.4 lightness — brightness exhibited by the electronic paper display relative to a perfect reflecting diffuser under
the same illumination.
5.2.5 lightness range — lightness difference between the white state and the black state of a display.
5.2.6 reflectance factor — ratio of the reflected luminous flux from the electronic paper display to that from a
perfect reflecting diffuser under the same measurement geometry.
5.2.7 threshold-based viewing angle — the angle at which the DUT displays lightness range larger than or equal to
threshold value of lightness range.
6 Summary of Test Method
6.1 The test methods provide procedures for measuring the optical properties of electronic paper displays by using a
spectrophotometer or colorimeter under diffuse or directional illumination. The key steps include:
6.1.1 Measuring the spectral reflectance factors of the reference white standard, black standard, and DUT with a
spectrophotometer.
6.1.2 Measuring the CIE tristimulus values of the reference white standard, black standard, and DUT with a
colorimeter.
6.1.3 Measuring the ghosting index by measuring the spectral reflectance factors or the CIE tristimulus values of
the four test points on the full-screen white.
6.1.4 Evaluating the angular optical performance either through measuring the lightness range at designated
incidence angles, viewing angles, and azimuth angles or through measuring the threshold-based viewing angle.
6.1.5 Measuring the bistability by measuring the spectral reflectance factors or the CIE tristimulus values of DUT at
two different time.
7 Environmental Conditions
 Temperature: (25 ± 3) ℃
 Humidity: 25 % to 85 % RH
 Illumination of surrounding: dark room ≦ 1 lx
 No reflection or low reflection objects of surroundings
When different environmental conditions are used, they shall be noted in the report.
8 Apparatus
8.1 Light Source
8.1.1 Use a tungsten halogen lamp (CIE standard illuminant A) as a light source. When different light sources are
used, they shall be noted in the report.
8.2 Light-Measuring Device (LMD)
8.2.1 For a spectral reflection measurement, a spectrophotometer is used as an LMD and its wavelength intervals,
Δλ shall not be greater than 10 nm over the wavelength range from 380 nm to 780 nm.
8.2.2 For a filter photometric reflection measurement, a colorimeter (filter photometer) is used as an LMD.
8.3 Reflection Standards
8.3.1 For the spectral reflection measurement, one reference white standard and one reference black standard of
calibrated spectral reflectance factor RWS ( ) and RBS ( ) respectively for the same measurement geometry as in the
test configuration shall be used.
8.3.2 For the filter photometric reflection measurement, one reference white standard and one reference black
standard of calibrated CIE tristimulus values ( X WS , YWS , ZWS ) and ( X BS , YBS , Z BS ) respectively for the same
measurement geometry as in the test configuration shall be used.
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
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9 Measurement Geometry
9.1 Diffuse Illumination
9.1.1 Hemispherical Illumination
9.1.1.1 Use a light source with an integrating sphere, as a uniform diffuse light source, to illuminate DUT. Place the
LMD at the measurement port with an inclination angle of  D (recommend 8°) off the normal to the center of the
DUT. (See Figure 1.) The measurement area covers no less than 500 pixels and measurement field angle is 2° or less.
For the specular reflection excluded measurement, open the cover of the specular port during the test. For the
specular reflection included measurement, close the cover of the specular port during the test.
Figure 1
Hemispherical Illumination Measurement Geometry
9.2 Directional Illumination
9.2.1 Ring-light Illumination
9.2.1.1 Use a ring-light source to provide uniform directional illumination on the DUT over all azimuth angles at an
inclination angle of  S (recommend 45°). Place the LMD normal to the center of the DUT. (See Figure 2.) The
measurement area covers no less than 500 pixels and measurement field angle is 2 or less.
Figure 2
Ring-light Illumination Measurement Geometry
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9.2.2 Collimated Light Illumination
9.2.2.1 Use a collimated light source to provide directional illumination on the DUT at an inclination angle of  S .
Place the LMD at an viewing angle of  D . (See Figure 3.) The measurement area covers no less than 500 pixels and
measurement field angle is 2° or less.
Figure 3
Collimated Illumination Measurement Geometry
10 Procedure
10.1 Spectral Reflection Measurement
10.1.1 Set up the measurement geometry.
10.1.2 Warm up the light source.
10.1.3 Measure the spectral reflectance factors of the reference white standard, RWS ' ( ) with a spectrophotometer.
10.1.4 Measure the spectral reflectance factors of the reference black standard, RBS ' ( ) .
10.1.5 Refresh the DUT to erase the previous image, by displaying full-screen white and full-screen black
alternately for several times.
10.1.6 DUT displays the test pattern.
10.1.7 Measure the spectral reflectance factor of DUT at time t, R' ( , t ) .
NOTE 1: Time t starts from the time when UUT is triggered to display the test pattern.
10.2 Filter Photometric Reflection Measurement
10.2.1 Set up the measurement geometry.
10.2.2 Warm up the light source.
10.2.3 Measure the CIE tristimulus values of the reference white standard, X WS ' , YWS ' , and ZWS ' with a
colorimeter.
10.2.4 Measure the CIE tristimulus values of the reference black standard, X BS ' , YBS ' , and Z BS ' .
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10.2.5 Refresh the DUT to erase the previous image, by displaying full-screen white and full-screen black
alternately for several times.
10.2.6 DUT displays the test pattern.
10.2.7 Measure the CIE tristimulus values of DUT at time t , X ' (t ) , Y ' (t ) , and Z ' (t ) .
10.3 Ghosting Index Measurement
10.3.1 Follow spectral measurement procedure (10.1.1 ~ 10.1.5) or filter photometric measurement procedure
(10.2.1 ~ 10.2.5).
10.3.2 DUT displays the 2 × 2 checker-board test pattern (See Figure 4.), and then displays full-screen white.
Figure 4
2 × 2 Checker-board Test Pattern
Figure 5
Full-screen White Test Pattern with Four Test Points Marked
10.3.3 Measure the spectral reflectance factors or the CIE tristimulus values of the four test points, marked in the
Figure 5, on the full-screen white. D and W indicate the horizontal and vertical length of active area. The number
1~4 stand for the test points.
10.4 Angular Optical Performance Measurement
10.4.1 There are two ways to evaluate the angular optical performance for electronic paper displays. One is to
measure lightness range at some critical incidence angles, viewing angles, and azimuth angles. The other is to
determine the threshold value of lightness range first, and then obtain the threshold-based viewing angle at which
the DUT displays lightness range larger than or equal to the threshold value.
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
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10.4.2 Recommend to use hemispherical or collimated light illumination measurement geometry to evaluate the
angular optical performance of the DUT.
10.4.3 Illuminate the display at an inclination angle of  S and place the LMD at a viewing angle of  D for azimuth
angles  = 0°, 90°, 180° and 270°.
10.4.4 Follow spectral or filter photometric measurement procedure (10.1 or 10.2) to derive lightness ranges at
designated incidence angles, viewing angles, and azimuth angles.
10.5 Bistability Measurement
10.5.1 Follow spectral measurement procedure (10.1.1 ~ 10.1.7) or filter photometric measurement procedure
(10.2.1 ~ 10.2.7).
10.5.2 Record two data at different time, t1 and t2. Time t1 is less than 10 seconds, and t2 is more than 5 minutes.
11 Calculations
11.1 CIE Tristimulus Values
11.1.1 Spectral Reflection Measurement
11.1.1.1 Calculate the spectral reflectance factor at the time t , R( , t )
 R ( )  RBS ( ) 
(1)
R( , t )  R' ( , t )  RBS ' ( )   WS
  RBS ( )
 RWS ' ( )  RBS ' ( ) 
Where RWS ( ) and R BS ( ) are the calibrated spectral reflectance factors of the reference white standard and the
reference black standard respectively.
11.1.1.2 Calculate CIE tristimulus values at the time t , X (t ) , Y (t ) , Z (t )
 R(, t )  S ( )  x ( )  
Y (t )  k   R( , t )  S ( )  y ( )  
X (t )  k 


Z (t )  k 

(2)
R( , t )  S ( )  z ( )  

k
100
 S ( )  y( )  

where
S ( ) : the relative spectral power distribution of the illuminant
x ( ) , y ( ) , z ( ) : color matching functions of CIE 1931 standard colorimetric observer
R( , t ) : spectral reflectance factor of the DUT at time t
 : wavelength interval
 : wavelength range from 380 nm to 780 nm
11.1.2 Filter Photometric Reflection Measurement
11.1.2.1 Calculate CIE tristimulus values at time t , X (t ) , Y (t ) , Z (t )
 X  X BS 
X (t )  X ' (t )  X BS '  WS
  X BS
 X WS ' X BS ' 
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 Y  YBS 
Y (t )  Y ' (t )  YBS '  WS
  YBS
 YWS 'YBS ' 
(3)
 Z  Z BS 
Z (t )  Z ' (t )  Z BS '  WS
  Z BS
 ZWS ' Z BS ' 
Where X WS , Y WS , Z WS and X BS , Y BS , Z BS are the calibrated CIE tristimulus values of the reference white
standard and the reference black standard respectively.
11.2 Reflectance Factor
reflectance factor R(t ) 
Y (t )
Yn
(4)
Where Yn is the tristimulus value of the light reflected from a perfect reflecting diffuser illuminated by the same
light source as the DUT.
11.3 Contrast Ratio
contrast ratio CR(t ) 
Rw (t )
RB (t )
(5)
Where Rw (t ) and RB (t ) are the reflectance factors of the DUT’s white state and black state respectively.
11.4 CIELAB Color Space Coordinates
L* (t )  116 R(t )1/ 3 16

b (t )  200 R(t )

16
a* (t )  500 ( X (t ) X n )1 3  R(t )1/ 3 16
*
1/ 3
 (Z (t ) Z n )1 3
(6)
Where X n , Z n are the tristimulus values of the light reflected from a perfect reflecting diffuser illuminated by the
same light source as the DUT.
11.5 Lightness Range
lightness range LR(t ) LW* (t ) L B* (t )
(7)
11.6 Ghosting Index
ghosting index GI  Max( L*1, L*2 , L*3 , L*4 )  Min( L*1, L*2 , L*3 , L*4 )
(8)
where
L*1 , L2* , L3* , and L4* are the lightness values of the four test points in Figure 5.
Max( L*1 , L*2 , L*3 , L*4 ) is the maximum lightness value among L*1 , L2* , L3* , and L4* .
Min( L*1, L*2 , L*3 , L*4 ) is the minimum lightness value among L*1 , L2* , L3* , and L4* .
11.7 Bistability

L* (t1)  L* (t 2)
bistability  1 

L* (t1)


  100 %


(9)
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Document Number: 4999A
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12 Reporting Results
Table 1 Report Sample of Reflection Test Data
electronic paper Display Model No.
 A  D65  _________
Illuminant
 Spectrophotometer
 Colorimeter
 _________
LMD
 Diffuse Illumination:
 di : 8° de : 8°
 _________
 Directional Illumination
 45°a : 0° 45°x : 0°
 _________
Measurement Geometry Type
White State
Reflectance factor R (%)
t = _________s
Black State
Contrast Ratio ( CR )
L*
White State
a*
b*
CIELAB
Color Space
L*
Black State
a*
b*
Lightness Range ( LR )
Ghosting Index ( GI )
Bistability
t1 = _________ s
t 2 =_________ min
White State
Black State
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Table 2 Report Sample of Angular Optical Performance Test Data
electronic paper Display Model No.
Illuminant
LMD
Measurement Geometry Type
 A  D65  _________
 Spectrophotometer
 Colorimeter
 _________
 Diffuse Illumination:
 Directional Illumination
S
D

S

Threshold-based
Viewing Angle
LR
Angular Lightness Range
t = _________ s
Threshold-based Viewing Angle
Threshold LR = _________
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NOTICE: Semiconductor Equipment and Materials International (SEMI) makes no warranties or representations as
to the suitability of the Standards and Safety Guidelines set forth herein for any particular application. The
determination of the suitability of the Standard or Safety Guideline is solely the responsibility of the user. Users are
cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other relevant literature,
respecting any materials or equipment mentioned herein. Standards and Safety Guidelines are subject to change
without notice.
By publication of this Standard or Safety Guideline, SEMI takes no position respecting the validity of any patent
rights or copyrights asserted in connection with any items mentioned in this Standard or Safety Guideline. Users of
this Standard or Safety Guideline are expressly advised that determination of any such patent rights or copyrights,
and the risk of infringement of such rights are entirely their own responsibility.
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