I E C 62 5-5-1 ® Edition 201 7-05 I N TE RN ATI ON AL S TAN D ARD colour i n sid e F l e xi bl e d i s pl a y d e vi ce s – IEC 6271 5-5-1 :201 7-05(en) P art 5-1 : M e as u ri n g m eth od s of opti cal pe rform an ce T H I S P U B L I C AT I O N I S C O P YRI G H T P RO T E C T E D C o p yri g h t © I E C , G e n e v a , S wi tz e rl a n d 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 I EC copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or your local I EC member National Committee for further information IEC Central Office 3, rue de Varembé CH-1 21 Geneva 20 Switzerland Tel.: +41 22 91 02 1 Fax: +41 22 91 03 00 info@iec.ch www.iec.ch Ab ou t th e I E C The I nternational Electrotechnical Commission (I EC) is the leading global organization that prepares and publishes I nternational Standards for all electrical, electronic and related technologies Ab o u t I E C p u b l i ca ti o n s The technical content of IEC publications is kept under constant review by the IEC Please make sure that you have the latest edition, a corrigenda or an amendment might have been published I E C Catal og u e - webstore i ec ch /catal og u e The stand-alone application for consulting the entire bibliographical information on IEC International Standards, Technical Specifications, Technical Reports and other documents Available for PC, Mac OS, Android Tablets and iPad I E C pu bl i cati on s s earch - www i ec ch /search pu b The advanced search enables to find IEC publications by a variety of criteria (reference number, text, technical committee,…) It also gives information on projects, replaced and withdrawn publications E l ectroped i a - www el ectroped i a org The world's leading online dictionary of electronic and electrical terms containing 20 000 terms and definitions in English and French, with equivalent terms in additional languages Also known as the International Electrotechnical Vocabulary (IEV) online I E C G l os sary - s td i ec ch /g l oss ary 65 000 electrotechnical terminology entries in English and French extracted from the Terms and Definitions clause of IEC publications issued since 2002 Some entries have been collected from earlier publications of IEC TC 37, 77, 86 and CISPR I E C J u st Pu bl i s h ed - webstore i ec ch /j u stpu bl i sh ed Stay up to date on all new IEC publications Just Published details all new publications released Available online and also once a month by email I E C C u stom er S ervi ce C en tre - webstore i ec ch /csc If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csc@iec.ch I E C 62 5-5-1 ® Edition 201 7-05 I N TE RN ATI ON AL S TAN D ARD colour i n sid e F l e xi bl e d i s pl a y d e vi ce s – P art 5-1 : M eas u ri n g m eth od s of opti cal pe rform an ce INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 31 20 ISBN 978-2-8322-4354-1 Warn i n g ! M ake s u re th a t you ob tai n ed th i s p u b l i cati on from an au th ori zed d i stri b u tor ® Registered trademark of the International Electrotechnical Commission –2– I EC 6271 5-5-1 : 201 I EC 201 CONTENTS FOREWORD I NTRODUCTI ON Scope Norm ative references Terms, definitions and abbreviated term s Terms and definitions Abbreviated terms Structure of m easuring equipm ent Measuring configuration – Display m ounting General Display mounting for uniformity m easurements Display mounting for viewing direction measurements Light m easuring device 1 Light source configurations General Uniform hem ispherical diffuse illum ination 3 Directed source illum ination Standard m easuring conditions 5 Standard m easuring environmental conditions 5 Standard lighting conditions 5 Dark room conditions 5 2 Standard am bient illum ination spectra 5 Standard illum ination geometries Diffuse reflectance standard Standard setup conditions Adjustment of display m odules Starting conditions of m easurem ents 3 Conditions of measuring equipm ent Standard locations of measurem ent field Optical measuring m ethods in dark room conditions Lum inance and its uniformity General Measuring equipment Screen centre lum inance m easuring method Lum inance uniformity measuring method Lum inance uniformity definition and evaluation 20 Contrast ratio 20 General 20 2 Measuring equipment 20 Measuring method 20 Definition and evaluation 20 Chrom aticity, colour uniform ity, and colour gamut area 21 General 21 Measuring equipment 21 3 Screen centre chrom aticity m easuring m ethod 21 Screen centre colour gam ut and colour gamut area measuring method 22 I EC 6271 5-5-1 : 201 I EC 201 –3– Colour uniformity measuring method 24 6 Peak white field correlated colour temperature 25 General 25 Measuring equipment 25 Measuring method 25 Viewing direction dependence 25 General 25 Measuring equipment 25 Measuring method 26 Definition and evaluation 27 6 Cross-talk with display in bent state 28 6 General 28 6 Measuring equipment 28 6 Measuring m ethod 29 Optical measuring m ethod under am bient illum ination 31 Reflection measurem ents 31 General 31 Measuring conditions 32 Ambient contrast ratio 35 General 35 2 Measuring conditions 36 Measuring m ethod 36 Ambient display colour 36 General 36 Measuring conditions 37 3 Measuring m ethod 37 Ambient colour gam ut volum e 38 General 38 Measuring conditions 38 Measuring method 38 4 Reporting 40 Annex A (informative) Calculation m ethod of am bient colour gam ut volum e 42 A Purpose 42 A Procedure for calculating the colour gamut volume 42 A Surface subdivision m ethod for CI ELAB gamut volume calculation 44 A 3.1 Purpose 44 A 3.2 Assumptions 44 A 3.3 Algorithm 44 A 3.4 Software example execution 45 Bibliograph y 49 Figure – Exam ple of the coordinate system used for a convex display of a constant radius of curvature about the y -axis Figure – Top view example of how a convex display can be rotated within the measurement field Figure – Top view example of display m ount that rotates in the x-z plane for viewing direction measurem ents 1 Figure – Optical characteristics of a spot photom eter, colorim eter, or spectroradiometer –4– I EC 6271 5-5-1 : 201 I EC 201 Figure – Example of the relationship between measurem ent field diameter and inclinations angles Figure – Exam ple of reflection m easurem ent geom etries for spherical illumination Figure – Exam ple of convex display illuminated by a directed light source Figure – Exam ple of convex display illuminated by a ring light source Figure – Standard m easurem ent positions Figure – Test pattern used for % area window m easurements Figure 1 – Examples of the colour gam ut as represented in two com m on chrom aticity diagrams 23 Figure – Example of contrast ratio dependence on viewing direction 27 Figure – Cross-talk pattern with diagonal % white window boxes on grey background 29 Figure – Cross-talk pattern with diagonal % black window boxes on grey background 30 Figure – Cross-talk pattern with perpendicular % white window boxes on grey background 30 Figure – Cross-talk pattern with perpendicular % black window boxes on grey background 31 Figure – Example of the range in colours produced by a display 40 Figure A – Anal ysis flow chart for calculating the colour gam ut volum e 42 Figure A – Graphical representation of the colour gamut volum e for sRGB in the CI ELAB colour space 43 Table – I nput signals for CI ELAB, CI E 931 and CI E 976 U CS colour gam ut measurements 22 Table – Exam ple of CI E 976 U CS chrom aticity non-uniform ity 24 Table – Exam ple form at used for reporting viewi ng direction perform ance 28 Table – Eigenvalues M1 and M2 for CI E daylight I llum inants D50 and D75 33 Table – An exam ple of minimum colours required for gam ut volume calculation of a 3-primary 8-bit display 39 Table – Measured tristim ulus values for the m inim um set of colours 41 Table – Calculated white point in the dark room and ambient illumination conditions 41 Table – Colour gam ut volum e in the CI ELAB colour space 41 Table A – Tristimulus values of the sRGB prim ary colours 43 Table A – Example of sRGB colour set represented in the CI ELAB colour space 43 Table A – Example of sRGB colour gam ut volum e in the CI ELAB colour space 44 I EC 6271 5-5-1 : 201 I EC 201 –5– INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON F L E XI B L E D I S P L AY D E VI C E S – P a rt -1 : M e a s u ri n g m e th o d s o f o p ti c a l p e rfo rm a n c e FOREWORD ) The I nternati on al Electrotechni cal Comm ission (I EC) is a worl d wid e organization for stan dardization com prisin g all n ation al el ectrotechnical comm ittees (I EC National Comm ittees) The object of I EC is to prom ote internati onal co-operation on all q uestions concerni ng stand ardi zati on in the el ectrical an d electronic fi elds To this en d and in additi on to other acti vities, I EC pu blish es I nternational Stan dards, Techn ical Specificati ons, Technical Reports, Publicl y Avail abl e Specificati ons (PAS) an d Gu ides (h ereafter referred to as “I EC Publication(s)”) Th ei r preparation is entrusted to tech nical comm ittees; any I EC N ational Comm ittee interested in the subj ect dealt with m ay partici pate in this preparatory work I nternational, governm ental an d n on governm ental organ izations l iaising with th e I EC also participate i n this preparation I EC collaborates closel y with the I ntern ational Organi zation for Stand ardization (I SO) in accordance with conditions determ ined by agreem ent between th e two organi zati ons 2) The form al decisions or ag reem ents of I EC on tech nical m atters express, as n early as possible, an i nternati onal consensus of opi nion on the rel evant subjects since each technical com m ittee has representati on from all interested I EC N ational Com m ittees 3) I EC Publications have the form of recom m endations for intern ational use an d are accepted by I EC National Com m ittees in that sense While all reasonable efforts are m ade to ensure that th e tech nical content of I EC Publications is accu rate, I EC cann ot be h eld responsi ble for th e way in which th ey are used or for an y m isinterpretation by an y en d u ser 4) I n order to prom ote intern ational u niform ity, I EC National Com m ittees und ertake to apply I EC Publications transparentl y to the m axim um extent possible i n their national an d regi on al publicati ons Any d ivergence between an y I EC Publication and the correspondi ng national or regi on al publicati on sh all be clearl y in dicated in the latter 5) I EC itself d oes n ot provi de an y attestation of conform ity I n depend ent certificati on bodies provi de conform ity assessm ent services and, in som e areas, access to I EC m arks of conform ity I EC is not responsi ble for an y services carri ed out by ind ependent certification bodi es 6) All users shou ld ensure that th ey h ave the l atest editi on of thi s publicati on 7) No liability shall attach to I EC or its directors, em ployees, servants or ag ents inclu din g in divi du al experts an d m em bers of its tech nical com m ittees and I EC Nati on al Com m ittees for any person al i nju ry, property d am age or other dam age of any n ature whatsoever, wheth er di rect or indirect, or for costs (includ i ng leg al fees) and expenses arisi ng out of the publ ication, use of, or relian ce upon, this I EC Publicati on or any other I EC Publications 8) Attention is drawn to the N orm ative references cited in th is publ ication Use of the referenced publ ications is indispensable for the correct applicati on of this publication 9) Attention is drawn to the possibility that som e of the elem ents of this I EC Publication m ay be the su bject of patent rig hts I EC shall not be held responsibl e for identifyi ng any or all such patent ri ghts I nternational Standard I EC 6271 5-5-1 has been prepared by I EC technical com mittee 1 0: Electronic display devices The text of this I nternational Standard is based on the following documents: FDI S Report on votin g 1 0/859/FDI S 1 0/870/RVD Full information on the voting for the approval of this I nternational Standard can be found in the report on voting indicated in the above table This docum ent has been drafted in accordance with the I SO/I EC Directives, Part A list of all parts of the I EC 6271 series, published under the general title Flexible display devices, can be found on the I EC website –6– I EC 6271 5-5-1 : 201 I EC 201 The comm ittee has decided that the contents of this docum ent will rem ain unchanged until the stability date indicated on the I EC website under "http://webstore iec.ch" in the data related to the specific document At this date, the docum ent will be • • • • reconfirm ed, withdrawn, replaced by a revised edition, or amended A bilingual version of this publication may be issued at a later date I M P O RT AN T th at it – Th e co n ta i n s u n d e rs t a n d i n g c o l o u r p ri n t e r of ' co l ou r c o l o u rs i ts in si d e' wh i ch c o n te n ts l og o a re U s e rs on th e cover c o n s i d e re d sh ou l d p ag e to t h e re fo re of th i s be p ri n t p u b l i cati on u s e fu l th i s fo r i n d i c ate s th e d o cu m e n t c o rre c t u si ng a I EC 6271 5-5-1 : 201 I EC 201 –7– INTRODUCTION This part of I EC 6271 was designed for the standardization of measuring m ethods and detailed setup conditions that are used to characterize the optical performance of flexible display devices The surface conditions and shape of flexible displays can change depending on the application For exam ple, a sm art watch may have a fixed convex display, a cell phone or TV a fixed concave display, and a bendable display m ay have either a concave or convex shape with a variable radius of curvature Up to now, all of these displays would usuall y be characterized in their flat state H owever, since it is possible that mechanical stress induced by bending the display can change its optical characteristics, the display should be measured in its designed bent state This ensures that the display’s optical performance is representative of its intended application This docum ent specifies the necessary conditions and methods to measure the optical perform ance of a display in a bent state –8– I EC 6271 5-5-1 : 201 I EC 201 F L E XI B L E D I S P L AY D E VI C E S – P a rt -1 : M e a s u ri n g m e th o d s o f o p ti c a l p e rfo rm a n c e S cop e This part of I EC 6271 specifies the standard m easuring conditions and m easuring m ethods for determ ining the optical performance of flexible displays in the dark or under am bient illum ination This document mainl y applies to display m odules that are bendable about one axis The display is m easured in a static m echanical state The m easuring m ethods apply to monochrome or colour displays with a single radius of curvature of 35 mm or greater N o rm a t i ve re fe re n c e s The following docum ents are referred to in the text in such a way that som e or all of their content constitutes requirements of this docum ent For dated references, onl y the edition cited applies For undated references, the latest edition of the referenced docum ent (including an y am endm ents) applies I EC 60050-845, International Electrotechnical Vocabulary – Part 845: Lighting (available at < http://www electropedia org > ) I EC 61 966-2-1 , Multimedia systems and equipment – Colour measurement and management – Part 2-1: Colour management – Default RGB colour space – sRGB IEC 6271 5-1 -1 , Flexible display devices – Part 1-1: Terminology and letter symbols IEC 62341 -6-2: 201 5, Organic light emitting diode (OLED) displays – Part 6-2: Measuring methods of visual quality and ambient performance I EC 62679-3-1 : 201 4, Electronic paper displays – Part 3-1: Optical measuring methods IEC TR 62728, Display technologies – LCD, PDP and OLED – Overview and explanation of differences in terminology CI E 5: 2004, Colorimetry 3 T e rm s , d e fi n i t i o n s a n d a b b re vi a t e d t e rm s T e rm s a n d d e fi n i t i o n s For the purposes of this document, the terms and definitions given in I EC 6271 5-1 -1 and I EC TR 62728 appl y ISO and I EC maintain term inological databases for use in standardization at the following addresses: • I EC Electropedia: available at http://www electropedia org/ • I SO Online browsing platform: available at http: //www iso org/obp – 38 – ZQ, amb = 683 ∫λ I EC 6271 5-5-1 : 201 λ λ λ LQ,amb ( ) z ( ) d where -x( λ ) , Error! Bookmark not defined -y( λ ) , and CI E 5: 2004) -z( λ ) I EC 201 (41 ) are the colour m atching functions (see The am bient 931 CI E x and y chromaticity coordinates for the display at the desired colour state Q under the standard daylight illum ination conditions are: x Q, amb = y Q, amb = XQ, amb XQ, amb + YQ,amb + Z Q,amb YQ, amb XQ, amb + YQ, amb + Z Q,amb (42) (43) Report the effective tristimulus values and CI E 931 chrom aticity coordinate for the rendered display colour Q , the CI E illum inants and illum inance values used in the calcul ations, and the m easuring conditions 7 Am bi en t col ou r g am u t vol u m e G en eral The purpose of this m ethod is to m easure the am bient colour gamut volum e of a flexible display module under defined ambient illumination conditions The m ethod uses the basic characteristics of the display m easured by the m ethods in other clauses/subclauses to estim ate the performance under typical indoor or outdoor lighting environments The display chrom aticity coordinates measured under dark room conditions may also be used to determine the dark room colour gamut volume This colour gam ut volume shall be com pared to the I EC sRGB standard (I EC 61 966-2-1 ) colour gamut volum e with a D65 white point This m ethod is lim ited to display modules with RGB primaries NOTE I f a display exhi bits significant photolum inescence, then the am bient colou r gam ut volum e calculation is onl y valid for the sam e illum ination spectra an d geom etry used to m easure th e refl ection coefficients M easu ri n g d i ti on s The illuminance conditions shall be as follows: – The standard ambient illumination conditions for an indoor room and clear sky daylight shall be used Additional illum ination conditions may also be used, depending on the application – Except for the standard am bient illumination cond itions, all other conditions are the standard conditions M easu ri n g m eth od The am bient colour gamut volume will be calculated from the effective ambient tristim ulus values determined for each displayed colour following the procedures in The measurements and calculations shall be consistentl y perform ed for a % box window colour on a % grey level background The ambient colour gam ut volum e with ambient illumination will be represented by the convex hull of display colours m easured within the CI ELAB colour space for the defined indoor and outdoor lighting conditions The volume of that colour space under standard am bient display illumination is determined by the following procedure: I EC 6271 5-5-1 : 201 I EC 201 – 39 – a) Appl y a % box window pattern, for at least eight defined colours The colours shall uniforml y sam ple the display’s colour capability For exam ple, a three-primary display shall be m easured for at least red, green, blue, cyan, yellow, m agenta, black and 00 % grey level white (see Table 5) Each colour (except black) is displayed at its m axim um signal level b) The effective am bient tristimulus values shall be determined following the procedure in I f it can be shown that the spectral reflection coefficients are invariant to the displayed colour at m aximum signal level, then a com mon hemispherical diffuse spectral reflectance or directed spectral reflectance factor can be used for all the colours at maxim um signal level Table – An example of minimum colours required for gamut volume calculation of a 3-primary 8-bit display Colour 8-bit Digital signal level Red Red = 255, Green = 0, Blue = Green Red = 0, Green = 255, Blue = Blue Red = 0, Green = 0, Blue = 255 Yellow Red = 255, Green = 255, Blu e = Magenta Red = 255, Green = 0, Blue = 255 Cyan Red = 0, Green = 255, Blue = 255 White Red = 255, Green = 255, Blu e = 255 Black Red = 0, Green = 0, Blue = c) The ambient tristim ulus values shall be transformed into the three-dimensional CI ELAB colour space (see CI E 5: 2004) Additional three-dim ensional uniform colour spaces may also be used, and identified in the test report Each colour point can be plotted on the L* , a* , and b* axes of the CI ELAB colour space by referencing the peak white daylight tristim ulus values ( XW, day , YW , day and ZW , day ) and using the following transform ation form ulae: L* = 1 × f(YQ, day / YW, day ) − [ × [ f(Y (44) ] )] a* = 500 × f( XQ, day / XW, day ) − f(YQ, day / YW, day ) (45) b* = 500 (46) Q, day / YW, day ) − f( ZQ, day / Z W, day where t1 / t > ( / 29 ) f( t ) = 29 16 otherwise ( ) t + 1 (47) An example of the am bient colour gam ut volum e in the CI ELAB uniform colour space is given in Figure – 40 – I EC 6271 5-5-1 : 201 I EC 201 CI ELAB Colour space 00 80 L* 60 40 20 –1 00 –50 a* 50 00 –1 00 –1 50 –50 50 00 b* IEC NOTE Figu re shows an exam ple of th e ran ge in colou rs produced by a display as represented by th e CI ELAB colou r space Figure – Example of the range in colours produced by a display Calculate the colour gam ut volume corresponding to the possible range of am bient display colours as represented in the CI ELAB colour space See Annex A for a detailed description of the anal ysis recommended to calculate the colour gam ut volum e Other gam ut calculation methods may be used if they yield the sam e results as the reference m ethod described in Annex A NOTE This docum ent evalu ates a displ ay am bient perform ance with th e CI ELAB m odel More advanced col ou r appearance m odels are needed to evalu ate a display appearance when the backgroun d is considered 7.4.4 Reporting The CI ELAB colour gamut volum e shall be reported in the test report along with the characteristics of the standard am bient illum ination that were used I f additional colour spaces are used, they shall be reported as well Report the spectral reflectance factors The measured ambient tristim ulus values shall all be reported as illustrated in Table Table shall indicate the original effective tristimulus values, i e , the tristimulus values shall not be normalized to 00 For each ambient illumination condition a separate table is required The CCT and white CI E 931 chromaticity coordinates, in the dark room and ambient conditions, shall be reported in a form sim ilar to Table The percent of colour gamut volume relative to the I EC sRGB standard colour space (I EC 61 966-2-1 ) with a D65 white point shall be reported in a form described by Table I EC 201 I EC 6271 5-5-1 : 201 – 41 – T a b l e – M e a s u re d t ri s t i m u l u s v a l u e s fo r th e m i n i m u m s e t o f c o l o u rs X Col ou r Y Q, am b Z Q, a m b Q, a m b Red Green Blue Yellow Magenta Cyan White Black This is requi red for the gam ut volum e calculati on un der the specified am bient illum ination conditi on (see Tabl e 5) T ab l e – C a l cu l ate d wh i te p o i n t i n am b i e n t i l l u m i n ati o n Col ou r White S u rro u n d t h e d a rk ro o m an d co n d i ti on s x y CCT Dark room I ndoor or outdoor condition Tabl e – C ol ou r g am u t vol u m e i n th e C I E L AB c o l o u r s p a c e C o l o u r G a m u t Vo l u m e Am bient illum ination Percent relati ve to sRGB (8, 21 x1 ) Dark room % I ndoor or outdoor condition % – 42 – I EC 6271 5-5-1 : 201 I EC 201 Annex A (informative) Calculation method of ambient colour gamut volume A.1 Purpose The purpose of this method is to describe a procedure to calculate the colour gamut volum e of scattered colour points in the three-dimensional CI ELAB colour space A.2 Procedure for calculating the colour gamut volume The procedure shall be as follows (see Figure A ): Start Measure the spectral radiance of colour Calculate/measure gradation of colour between black and the others Convert all XYZ to CIELAB Define tetrahedrons in CIELAB hull Calculate and sum the volume of tetrahedrons End IEC Figure A.1 – Analysis flow chart for calculating the colour gamut volume ) Measure at least the red, green, blue, cyan, magenta, yellow, black and white colours of the display under the standard indoor or outdoor illum ination conditions according to Table A provides an example using sRGB prim aries under dark room illumination conditions and with the white lum inance ( Y) norm alized to 00 %: I EC 6271 5-5-1 : 201 I EC 201 T a b l e A x Col ou r – 43 – – T ri s t i m u l u s v a l u e s o f t h e s R G B p ri m a ry c o l o u rs y Q Q X Y Z Q, a m b Q, am b Q, am b Red 0, 640 0, 330 41 , 239 21 , 264 , 933 Green 0, 300 0, 600 35, 758 71 , 51 1 , 91 Bl ue 0, 50 0, 060 8, 048 7, 21 95, 053 Cyan 0, 225 0, 329 53, 806 78, 736 06, 973 Magenta 0, 321 0, 54 59, 287 28, 483 96, 986 Yellow 0, 41 0, 505 76, 998 92, 781 3, 853 Bl ack 0, 000 0, 000 0, 000 0, 000 0, 000 White 0, 31 0, 329 95, 046 00, 000 08, 906 2) Convert all colours points into the CI ELAB colour space using Formulae (43) to (46) See Table A and Figure A for an exam ple of the sRGB colour set in the CI ELAB colour space T a b l e A – E xa m p l e o f s R G B c o l o u r s e t re p re s e n t e d i n t h e C I E L AB c o l o u r s p a c e a* b* L* Red 80, 05 67, 223 53, 233 Green -86, 88 83, 86 87, 737 Blue 79, 94 -1 07, 854 32, 303 Cyan -48, 084 -1 4, 28 91 , 1 Magenta 98, 250 -60, 833 60, 320 Yellow -21 , 561 94, 488 97, 38 Black 0 White 0 00 Col ou r Green (–86, 2; 83, 2; 87, 7) Yellow (–21 , 5; 94, 4; 97, ) White (0 00) L* Cyan (–48, ; –1 4, ; 91 , ) 90 80 70 60 50 40 30 20 Black (0; 0; 0) 10 –80 –60 –40 –20 20 40 a* F i g u re A – G p h i c a l Red (80, ; 67, 2; 53, 2) Magenta (98, 2; –60, 8; 60, 3) Blue (79, 2; –1 07, 8; 32, 3) 60 re p re s e n t a t i o n i n t h e C I E L AB 80 –1 00 –50 b* IEC o f t h e c o l o u r g a m u t v o l u m e fo r s R G B co l ou r s p a ce – 44 – I EC 6271 5-5-1 : 201 I EC 201 3) Compute the colour gam ut volume by adding up all the tetrahedrons contained within the displayed colour points and report as a percentage of the volum e compared with the sRGB colour gam ut volume An example of a display in a dark room with the sRGB colour gam ut volume calculated in the CI ELAB colour space is provided in Table A T a b l e A – E x a m p l e o f s RG B c o l o u r g a m u t vol u m e i n t h e C I E L AB c o l o u r s p a c e C o l o u r g a m u t vo l u m e A A Total 8, 21 x Percent relati ve to sRGB 00 % S u rfa c e s u b d i vi s i o n m e t h o d fo r C I E L AB g a m u t vo l u m e c a l c u l a t i o n P u rp o s e This algorithm accepts an arbitrary set of gam ut corner cases specified in CI E 931 XYZ tristim ulus values The m inim um set of colours would be red, green, blue, cyan, m agenta, yellow, black and white For devices that not have a well-behaved convex hull shape in the CI ELAB colour gamut volum e profile, m an y more sampled colours will be needed to accurately determ ine the colour gamut volume value The XYZ values are arranged in the rows of the input variable P, with a minim um of eight colour corner cases required The output value is the calculated colour gam ut volume A As s u m p t i o n s I t is assumed that the colour gam ut in the CI E XYZ colour space will be defined as the convex hull of given corner cases The colour gamut in the CI ELAB colour space will be this convex hull, normalised in the CI E XYZ space by the corner case with the m aximum luminance (taken as the white point), and translated into the CI ELAB colour space where it will no longer be entirel y convex A Al g o ri t h m a) Obtain the convex hull (see N ote ) of the colour corner points in P Store the tessellation of the surface of this hull in T I nitialise a total volum e v to b) Calculate the average of the points P to be used as a gam ut m id-point and store in P m c) For each triangular surface tile in T: ) Let s equal the number of edges that have extents (see Note 2) in L* , a*, b* coordinates greater than 2) I f s = then calculate the volume defined between the vertices of the surface tile and P m Add this volume to v 3) I f s = then calculate the m id-points in the CI E XYZ space and subdivide the triangular tile into four sub-tiles defined by each corner vertex with the two nearest m id-points and the three m id-points Repeat three times for each triangular sub-tile 4) I f s = or then calculate the mid-point in the CI E XYZ space of the edge with the largest extents in CI ELAB and subdivide the triangular tile into two sub-tiles along the line between the m id-point and opposite vertex Repeat three times for each triangular sub-tile NOTE Where the corner poi nts are th e stand ard RGBCMYKW NOTE Extents are used rather th an l en gth as they are faster to calcul ate d) Return the total volume now contained in v I EC 6271 5-5-1 : 201 A.3.4 I EC 201 – 45 – Software example execution In order to execute the Matlab program below, the following com mand is executed with the corresponding sRGB data loaded into memory: >> P = GetGamutCorners('sRGB') Default D65 white is used P= 0, 41 0, 770 0, 357 0, 538 0, 80 0, 592 0, 950 0, 21 0, 927 0, 71 0, 787 0, 072 0, 284 , 000 8 0, 01 0, 38 0, 1 , 069 0, 950 0, 969 , 089 where the data matrix corresponds to the following tristim ulus coordinates as exemplified by Table A : YK YR YY YG YC YB YM YW XK XR XY XG XC XB XM XW ZK ZR ZY ZG ZC ZB ZM ZW The CI ELAB colour gamut volum e is obtained by executing the following comm and: >> CI ELabVol_subd(P) ans = 8, 21 x1 _ Matl ab is the trad e nam e of a product supplied by MathWorks® This inform ation is gi ven for the conveni ence of users of this docum ent and does not constitute an en dorsem ent by I EC of th e product nam ed Equi val ent products m ay be used if they can be shown to lead to th e sam e results – 46 – I EC 6271 5-5-1 : 201 I EC 201 CI E L abVo l _s ub d m func t i o n [ v] = C I E Lab Vo l _s ub d( P) % E ac h r o w o f P c o n t ns XYZ t ri - s t i mu l us val ue s o f gamut c o rne r po i nt s % T he D ga mut i s de fi ne d as t he c o nve x hul l o f t he s e po i nt s i n XYZ s pa ce % T he s u rfa ce i s re c urs i ve l y s ub di vi de d wn t o a t hr e s ho l d s cal e i n CI E LAB % and t he vo l u me ma de by e ach s urfa ce t i l e t o a ce nt r al po i nt i s s umme d t hre s h=1 ; % C I E L ab s u bdi vi s i o n t hr e s ho l d % Ge t t he hul l de fi ne d by t he po i nt s T =co nvhul l n( P ) ; % Ge t t he whi t e p o i nt ( t ake n as t he pri mary wi t h t he maxi mu m Y) [ W, i ] =max( P( : , ) ) ; W=P( i , : ) ; % No r mal i s e t he gamut t o t he whi t e po i nt Pn=P / ( re p mat ( W, s i z e ( P, ) , ) ) ; % ge t t he mi d- po i nt Pm=me an ( Pn ) ; % add- o n t he C I E L ab po i nt s Pn=[ Pn, XYZ Lab( Pn ) ] ; Pm=[ Pm, XYZ Lab( Pm) ] ; % cal cul at e an d s um t he La b vo l ume o f e a ch s urf ace t i l e t o t he mi d- p o i n t v=0 ; fo r n=1 : s i z e ( T , ) , v=v+ S u bDLabVo l ( Pn ( T ( n , : ) , : ) , Pm, t hre s h) ; e nd % % s ub- fun ct i o ns % XYZ L ab co n ve rt s XYZ va l ue s a rra nge d i n co l u mns t o L* a* b * fun ct i o n [ t ] = XYZ Lab ( t ) i =( t >0 0 8 ) ; t ( i ) =t ( i ) ^ ( / ) ; t ( ~ i ) =7 * t ( ~ i ) + / 1 ; t =[ 1 * t ( : , ) - , 0 * ( t ( : , ) - t ( : , ) ) , 0 * ( t ( : , ) - t ( : , ) ) ] ; e nd % Re c urs i ve func t i o n t o de vi de up t he s u rfa ce t i l e t he n re t urn t he vo l ume fun ct i o n [ v ] = S ubDLab Vo l ( vp, c , t h ) % Ge t t he max e xt e nt o f e ac h e dge ( qui c ke r t han l e n gt h c al cu l at i o n ) m=max( ab s ( vp- ci rc s hi ft ( vp, ) ) , [ ] , ) ; % C o un t ho w ma ny e dge s have e xt e nt s l arge r t han t he t hre s ho l d s =s um( m>t h) ; i f ( s ==0 ) , % n o e dge s l a rge r: re t urn t he vo l ume v=ab s ( de t ( vp( : , : ) – re p ma t ( c ( , : ) , , ) ) / ) ; e l s e i f ( s ==3 ) , % al l e dge s l arge r : di vi de t i l e i n fo ur % ge t e dge mi d- po i nt s i p=( vp ( : , : ) + ci rc s hi ft ( vp( : , : ) , ) ) / ; % cal cul at e CI E La b po i nt s o f t he mi d- p o i nt s i p=[ i p , XYZ La b( i p) ] ; I EC 6271 5-5-1 : 201 I EC 201 – 47 – % and c a l l re c urs i ve l y fo r e a ch s ub - t i l e v=S u bDLab Vo l ( [ vp ( , : ) ; i p( : , : ) ] , c , t h) ; v=v+ S u bDL abVo l ( [ vp( , : ) ; i p( : , : ) ] , c, t h) ; v=v+ S u bDL abVo l ( [ vp( , : ) ; i p( : : , : ) ] , c , t h) ; v=v+ S u bDL abVo l ( i p, c , t h) ; e l s e % o n e o r t wo e dge s l ar ge r : s pl i t t he t i l e o n t he l a rge s t e dge % s hi ft t he o r de r s o - has t he l a rge s t e xt e nt [ m, i ] =max( m) ; vp=c i r cs hi ft ( vp, - i ) ; % cal cu l at e t he mi d- po i nt o f - an d t he CI E Lab p o i n t i p=( vp ( , : ) + vp ( , : ) ) / ; i p=[ i p , XYZ La b( i p) ] ; e nd e nd end % and c al l re c urs i ve l y fo r t he t wo s ub - t i l e s v=S u bDLab Vo l ( [ vp ( [ ] , : ) ; i p] , c, t h) ; v=v+ S u bDL abVo l ( [ vp( : , : ) ; i p] , c, t h) ; Ge t Gamut Co rne rs m func t i o n [ P ] = Ge t Gamut Co rne rs ( P , wh) % GE T PRI M re t urn s a s e t o f c o l o ur co rne r p o i nt s b as e d o n a s t an dard ga mut % i np ut s t r i ng mus t c o n t n o ne o f: % ' s RGB ' , ' Re c7 ' , ' E BU' , ' NT S C' % o pt i o n al l y o n e o f % ' D5 ' , ' D5 ' , ' D6 ' , ' D7 ' , ' I l l A' , ' I l l E ' i f i s c har ( P) i f na rgi n< wh=P ; end i f s t rfi nd( P, ' s RGB' ) | | s t rfi nd( P, ' Re c ' ) p ri m=[ , 3 ; , ; , ] ; e l s e i f s t rfi n d( P, ' E BU' ) p ri m=[ , 3 ; , ; , ] ; e l s e i f s t rfi n d( P, ' NT S C' ) p ri m=[ , 3 ; , ; , ] ; else e rro r( ' no n- va l i d co l o ur p ri mary s p e c i fi c at i o n' ) ; end P=pri m; e nd i f i s c har( wh) i f s t rfi nd( wh, ' D5 ' ) wh=[ , ] ; e l s e i f s t r fi n d( wh, ' D5 ' ) wh=[ 3 , ] ; e l s e i f s t r fi n d( wh, ' D6 ' ) wh=[ , ] ; e l s e i f s t r fi n d( wh, ' D7 ' ) wh=[ 9 , ] ; – 48 – e nd I EC 6271 5-5-1 : 201 e l s e i f s t rfi n d( wh, ' I l l A' ) wh=[ 4 7 , ] ; e l s e i f s t r fi n d( wh, ' I l l E ' ) wh=[ 3 3 , 3 3 ] ; else wh=[ , ] ; di s p l a y( ' De fa ul t D6 whi t e us e d' ) ; end e nd wh=[ wh, - s um( wh) ] / wh( ) ; P=[ P, - s um( P, ) ] ; P=P * re pmat ( ( wh/ P ) ' , , ) ; % P=[ KRYGC BMW] ' P=[ 0 ; P( , : ) ; s um( P( : , : ) ) ; P( , : ) ; s um( P ( : , : ) ) ; P( , : ) ; s um( P( [ ] , : ) ) ; s u m( P ) ] ; I EC 201 I EC 6271 5-5-1 : 201 I EC 201 – 49 – Bibliography [1 ] D H ertel, Viewing direction m easurements on flat and curved flexible E-paper displays J Soc I nformation Display, V 21 , p 239–248 (201 3) [2] J.-H Chong, et al, Method to m easure optical performance of flexible OLED display, Soc I nform ation Display Symposium Digest Tech Papers, V 45, p 83-1 86 (201 4) [3] I nternational Committee for Display Metrology, I nform ation Display M easurements Standard, Ver 03, (201 2) [4] D Hertel, E F Kelley, and J Penczek, Measuring the optical perform ance of flexible displays under hemispherical diffuse illumination Soc I nform ation Display Sym posium Digest Tech Papers, V 46, (201 5) [5] E F Kelley, M Lindfors, and J Penczek, Display daylight am bient contrast m easurement m ethods and daylight readability, J Soc I nform ation Display, V 4, p 01 9-1 030 (2006) [6] AN SI /I ESN A RP-1 -04, Am erican N ational Standard Practice for Office Lighting, I lluminating Engineering Society of N orth Am erica (I ESN A), (2004) [7] Using m odel in ASTM G1 97, “Standard Table for Reference Solar Spectral Distributions: Direct and Diffuse on 20º Tilted and Vertical Surfaces”, (2008) [8] The I ESN A Lighting H andbook: Reference and Application, 9th Ed (2002) [9] B P Dehm low and K A Brostad, “Reflection-mode diffraction and m atrix displays”, Proc Of the SPI E, Vol 3363 (Cockpit Displays V), pp 21 7-224 (1 998) [1 0] CI E Publication No 44, Absolute Methods for Reflection Measurem ent, Comm ission I nternationale de l’Eclairage (I nternational Comm ission on I llumination), 979 reprinted 990 For example of sampling sphere, see the Sharp-Little method [1 ] E F Kelley, “Diffuse reflectance and am bient contrast measurem ents using a sam pling sphere”, Proc Third Am ericas Display Engineering and Applications Conf (ADEAC 2006), Soc I nform ation Display, Atlanta, GA, U SA, pp -5, Oct 24-26, (2006) _ INTERNATIONAL ELECTROTECHNICAL COMMISSI ON 3, rue de Varembé PO Box 31 CH-1 21 Geneva 20 Switzerland Tel: + 41 22 91 02 1 Fax: + 41 22 91 03 00 info@iec.ch www.iec.ch