IEC 62595 2 1 Edition 1 0 201 6 04 INTERNATIONAL STANDARD Display l ighting unit – Part 2 1 Electro optical measuring methods of LED backlight unit IE C 6 2 5 9 5 2 1 2 0 1 6 0 4 (e n ) ® colour ins i[.]
I E C 62595-2-1 ® Edition 201 6-04 I N TE R N ATI ON AL STAN DAR D colour i n si de Di spl ay l i g h ti n g u n i t – IEC 62595-2-1 :201 6-04(en) Part 2-1 : El ectro -opti cal m easu ri n g m eth od s of LE D backl i g h t u n i t TH I S P U B L I C ATI O N I S C O P YR I G H T P R O TE C TE D C o p yri g h t © I E C , G e n e va , Sw i t z 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 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 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 Abo u t th e I E C The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes International Standards for all electrical, electronic and related technologies Ab o u t I E C p u b l i c a t i 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 EC C atal og u e - webstore i ec ch /catal o g u e E l ectro ped i a - www el ectro ped i a org 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 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 EC pu bl i cati on s search - www i ec ch /search pu b I E C G l o ssary - s td i ec ch /g l ossary 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 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 EC J u st Pu bl i s h ed - webstore i ec ch /j u stp u bl i s h 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 Cu s to m er S ervi ce Cen 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 62595-2-1 ® Edition 201 6-04 I N TER N ATI ON AL STAN DAR D colour i n si de Di spl ay l i g h ti n g u n i t – Part 2-1 : El ectro -o pti cal m easu ri n g m eth od s o f LED backl i g h t u n i t INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 31 20; 31 260 ISBN 978-2-8322-3299-6 Warn i n g ! M ake su re th at you obtai n ed th i s pu bl i cati on from an au th ori zed d i stri bu tor ® Registered trademark of the International Electrotechnical Commission –2– I EC 62595-2-1 :201 © I EC 201 CONTENTS FOREWORD Scope N ormati ve references Terms, definitions and abbreviations Terms and defin i tions Abbreviations General measu remen t condi ti ons Stan dard atm osph eric condi ti ons for LED BLU M easu ri ng setu p Warm-u p tim e M easu remen t meth ods El ectrical measu remen t m eth ods Conditions Cu rren t Vol tage Power consu mption Optical measu remen t methods Conditions 2 Lu m inance Lu m in ance u ni form i ty or n on-u niformi ty Spectral power distri bu ti on 5 Chrom aticity Colour u ni formi ty An g u lar lu ance u n iform i ty 1 An g u lar colou r u ni form i ty 1 M easurement meth ods of bl ock-wise BLU s 1 Bi bliog raph y Fi gu re Fi gu re Fi gu re Fi gu re Fi gu re – – – – – Example of measu rin g setu p for LED BLU Example of warm-u p characteristic of BLU Defin i tion of zeni th an gl e θ an d azimu th ang le ϕ Examples of m easurement poin t layou t An gu lar lu minance u niform i ty measurement 1 Fi gu re – Example of checkerboard pattern (8 seg m en ts × seg men ts) for blockwise BLU Fi gu re – Example of sin g le block wh i te pattern Fi gu re – Example of sin g le block black pattern Fi gu re – Example of incoheren t poin t spread fu nction I EC 62595-2-1 :201 © I EC 201 –3– I NTERNATI ONAL ELECTROTECHN I CAL COMMI SSI ON DISPLAY LIGHTING UNIT – Part 2-1 : Electro-optical measuring methods of LED backlight unit FOREWORD ) Th e I n tern ati on al El ectrotech n i cal Com m i ssi on (I EC) i s a worl d wi d e org an i zati on for stan dard i zati on com pri si n g al l n ati on al el ectrotech n i cal com m i ttees (I EC N ati on al Com m i ttees) Th e obj ect of I E C i s to prom ote i n tern ati on al co-operati on on al l q u esti on s cern i n g stan dard i zati on i n th e el ectri cal an d el ectron i c fi el ds To th i s en d an d i n ad di ti on to oth er acti vi ti es, I EC pu bl i sh es I n tern ati on al Stan d ards, Tech n i cal Speci fi cati on s, Tech n i cal Reports, Pu bl i cl y Avai l abl e Speci fi cati on s (PAS) an d G u i d es (h ereafter referred to as “I EC Pu bl i cati on (s) ”) Th ei r preparati on i s en tru sted to tech n i cal com m i ttees; an y I EC N ati on al Com m i ttee i n terested i n th e su bj ect d eal t wi th m ay parti ci pate i n th i s preparatory work I n tern ati on al , g overn m en tal an d n on g overn m en tal org an i zati on s l i si n g wi th th e I EC al so parti ci pate i n th i s preparati on I EC col l aborates cl osel y wi th th e I n tern ati on al Org an i zati on for Stan d ard i zati on (I SO) i n accordan ce wi th d i ti on s d eterm i n ed by ag reem en t between th e two org an i zati on s 2) Th e form al deci si on s or ag reem en ts of I EC on tech n i cal m atters express, as n earl y as possi bl e, an i n tern ati on al sen su s of opi n i on on th e rel evan t su bj ects si n ce each tech n i cal com m i ttee h as represen tati on from al l i n terested I EC N ati on al Com m i ttees 3) I EC Pu bl i cati on s h ave th e form of recom m en d ati on s for i n tern ati on al u se an d are accepted by I EC N ati on al Com m i ttees i n th at sen se Wh i l e al l reason abl e efforts are m ade to en su re th at th e tech n i cal ten t of I EC Pu bl i cati on s i s accu rate, I E C can n ot be h el d respon si bl e for th e way i n wh i ch th ey are u sed or for an y m i si n terpretati on by an y en d u ser 4) I n ord er to prom ote i n tern ati on al u n i form i ty, I EC N ati on al Com m i ttees u n d ertake to appl y I EC Pu bl i cati on s tran sparen tl y to th e m axi m u m exten t possi bl e i n th ei r n ati on al an d reg i on al pu bl i cati on s An y di verg en ce between an y I EC Pu bl i cati on an d th e correspon d i n g n ati on al or reg i on al pu bl i cati on sh al l be cl earl y i n di cated i n th e l atter 5) I EC i tsel f d oes n ot provi d e an y attestati on of form i ty I n d epen d en t certi fi cati on bodi es provi d e form i ty assessm en t servi ces an d , i n som e areas, access to I E C m arks of form i ty I EC i s n ot respon si bl e for an y servi ces carri ed ou t by i n d epen d en t certi fi cati on bodi es 6) Al l u sers sh ou l d en su re th at th ey h ave th e l atest edi ti on of th i s pu bl i cati on 7) N o l i abi l i ty sh al l attach to I E C or i ts di rectors, em pl oyees, servan ts or ag en ts i n cl u d i n g i n d i vi du al experts an d m em bers of i ts tech n i cal com m i ttees an d I EC N ati on al Com m i ttees for an y person al i n j u ry, property d am ag e or oth er d am ag e of an y n atu re wh atsoever, wh eth er di rect or i n d i rect, or for costs (i n cl u d i n g l eg al fees) an d expen ses ari si n g ou t of th e pu bl i cati on , u se of, or rel i an ce u pon , th i s I EC Pu bl i cati on or an y oth er I EC Pu bl i cati on s 8) Atten ti on i s d rawn to th e N orm ati ve referen ces ci ted i n th i s pu bl i cati on U se of th e referen ced pu bl i cati on s i s i n di spen sabl e for th e correct appl i cati on of th i s pu bl i cati on 9) Atten ti on i s d rawn to th e possi bi l i ty th at som e of th e el em en ts of th i s I EC Pu bl i cati on m ay be th e su bj ect of paten t ri g h ts I EC sh al l n ot be h el d respon si bl e for i d en ti fyi n g an y or al l su ch paten t ri g h ts I n tern ati onal Standard I EC 62595-2-1 has been prepared by I EC Tech nical Commi ttee 1 0: El ectronic display devices Th is first editi on cancels and repl aces th e first edi ti on of I EC 62595-2 pu blished in 201 Th is edition consti tu tes a technical revision Th is edi tion inclu des th e followin g sig ni fican t technical chang es wi th respect to the previous edition : a) b) c) d) ch ang ed th e series ti tle in order to cover fron tl ig h t u nit; added the detai led measu remen t procedu res particu larl y for block-wise BLU ; del eted An nex A; revised Fig ure an d Fig ure and som e edi torial errors –4– I EC 62595-2-1 :201 © I EC 201 The text of th is standard is based on the foll owi ng docu men ts: FDI S Report on voti n g 1 0/731 A/FDI S 1 0/743A/RVD Fu ll informati on on the votin g for the approval of thi s stan dard can be fou nd in the report on votin g i ndicated i n the above table Th is pu blication has been drafted in accordance wi th the I SO/I EC Directi ves, Part A l ist of al l parts in th e I EC 62595 seri es, pu blish ed u n der the g en eral ti tl e unit, can be fou nd on the I EC website Display lighting Fu tu re standards in th is seri es wi ll carry the new g eneral title as cited above Titles of existi ng standards in th is series wil l be updated at th e ti me of the next edition The com mi ttee h as decided that th e ten ts of th is pu bl icati on wi ll remain u nchan ged u n ti l th e stabil ity date in dicated on th e I EC websi te u nder "h ttp://webstore iec ch" in the data related to the specific publ ication At th is date, the publ ication will be • recon firmed, • withdrawn , • replaced by a revised edi ti on , or • amended A bi li ngu al versi on of th is pu blicati on may be issu ed at a later date I M P O R TAN T – Th e ' c o l o u r i n s i d e ' th at it tai n s u n d erstan d i n g co l o u r pri n ter of co l o u rs i ts wh i ch ten ts log o a re U s e rs on t h e c o ve r p a g e o f t h i s p u bl i c at i o n co n s i d ered shoul d to th ere fo re be p ri n t u se fu l th i s for i n d i cates th e d ocu m en t c o rre c t u si ng a I EC 62595-2-1 :201 © I EC 201 –5– DISPLAY LIGHTING UNIT – Part 2-1 : Electro-optical measuring methods of LED backlight unit Scope Th is part of I EC 62595 speci fies th e standard m easurement condi tions and m easu ring methods for determi ni ng th e el ectrical and optical param eters of LED backli gh t u n its for li qu id crystal displays Normative references The following docu men ts, in wh ole or in part, are n orm ati vel y referenced in this docu m en t and are indispensabl e for i ts application For dated references, on ly the edition cited appli es For u ndated references, th e latest edition of th e referenced docu men t (inclu din g an y amendm ents) appl ies Liquid crystal display devices – Part 30-1: Measuring methods for liquid crystal display modules – Transmissive type I EC 61 747-30-1 , I EC 62595-1 -2, Display lighting unit – Part 1-2: Terminology and letter symbols Terms, definitions and abbreviations 3.1 Terms and definitions For th e purposes of th is docu men t, th e terms and defin i tions g iven in I EC 62595-1 -2 apply 3.2 BLU FOV LMD LSF Abbreviations backl ig h t un it field of view li gh t m easu ring device li gh t spread fu nction General measurement conditions 4.1 Standard atmospheric conditions for LED BLU U nless otherwise specified, al l tests and measu remen ts for LED BLU shal l be carried ou t after su fficient warm-u p time (see 3) , u n der the stan dard en viron men tal ditions, at a temperatu re of 25 °C ± °C, a relati ve hu m idity of 25 % to 85 %, and an atmospheric pressu re of 86 kPa to 06 kPa When different en vi ron men tal conditions are u sed, th ey shal l be noted in th e detai l specification (see I EC 61 747-30-1 ) To be pu bl i sh ed –6– 4.2 I EC 62595-2-1 :201 © I EC 201 Measuring setup Fi gu re shows a typical setup of a BLU , lu m in ance meter, power sou rce, block troll er, vol tm eters an d cu rren t meters for el ectro-optical m easu remen ts for LED BLU Block control signal Measurement distance LMD (Luminance meter) Power supply (for block-wise BLU) FOV BLU Sample stage Block control signal (for block-wise BLU) Power supply I Ammeter V Voltmeter IBLU I Isignal Vsignal I V VBLU BLU V IEC Figure – Example of measuring setup for LED BLU 4.3 Warm-up time The lu mi nance of LED backligh ts is affected by th e transient temperatu re beh avi ou r of LED ou tpu t as in Fi gu re I t takes a certai n ti me for LEDs u n til their junction temperatu re reaches th e steady state Lu ance measurem en t shall be carried ou t and recorded u ntil th e flu ctu ati ons of lu m inance measu red at an appropriate poi nt (u sually at the cen tre poin t) of the BLU become less th an the ran g e speci fied in I EC 61 747-30-1 u nless otherwise specifi ed The lu m in ance m easu rem ent shall be carried ou t as in 2 All measu rin g di tions sh all be kept constan t during the m easu rem en ts Chrom aticity measuremen t shall be carri ed ou t in the same m ann er as in the above, u n less otherwise specified The chrom atici ty measu rem en t shall be carri ed ou t as i n 5 The above m easu remen ts can be cu stomized between the cu stom er and the supplier, depending on vari ou s BLU sizes, appl icati ons, and so on I EC 62595-2-1 :201 © I EC 201 –7– ,4 Relative luminance ,2 ,0 0,8 0,6 0,4 0,2 0,0 10 20 30 40 50 60 Ti me (mi n) IEC Figure – Example of warm-up characteristic of BLU Measurement methods 5.1 5.1 Electrical measurement methods Conditions The BLU shal l be placed in th e measu remen t arran g emen t an d i t sh al l be assu red that al l requ ired condi tions are fu l filled After applying th e ini ti al el ectrical dri ving di ti ons (i e analogu e inpu t vol tage(s) or dig i tal inpu t sig nals) of the BLU an d wai tin g during the warm-u p ti m e speci fied in i n order to reach the steady state, th e m easu rem ent of the electrical qu an ti ties of interest shal l be started 5.1 Current The measu remen t of inpu t cu rren t sh ou ld be performed u nder standard measuri ng condi ti ons usin g the current m eter sh own in Fi gu re 5.1 Voltage The measu remen t of inpu t vol tag e sh ou ld be performed u nder stan dard measu ri ng condi tions usin g the voltage m eter sh own in Fig u re 5.1 Power consumption The measu remen t of power consu mption shou ld be carried ou t u nder the stan dard m easu ri ng condi tions in , u sing a power meter, or calcu lated by the measured val u es of voltag e and currents i n and For block-wise BLU s, th e power consu m ption of the control sig nal shal l be considered 5.2 5.2.1 Optical measurement methods Conditions The LED BLU to be measu red sh ou ld be placed i n th e measu rem en t arrang emen t an d i t sh all be assu red th at all requ ired condi tions are fu l fi lled –8– I EC 62595-2-1 :201 © I EC 201 After appl ying the in i ti al electrical driving condi tions to the BLU and waiting du rin g the warmu p ti me speci fi ed in in order to reach the steady state, the m easu remen t of the optical quan ti ties of in terest shall be started The measu rem ent of this stan dard sh ou ld be carried ou t at variou s ang les between the BLU and the LMD A polar coordi nate system ( θ, ϕ ) , wi th th e zen ith denoted by θ and th e azim u th den oted by ϕ sh ou ld be considered (see Fig u re 3) y BLU 2:00 x φ 3:00 9:00 θ LMD 6:00 z IEC Figure – Definition of zenith angle θ and azimuth angle ϕ 5.2.2 Luminance The measuremen ts shou ld be carried ou t in the dark room under the standard m easu ring conditions an d for th e desig n viewing directions, as follows: a) Posi tion the BLU b) Adju st th e LM D to the speci fied vi ewing di rection , accordi ng to ang les θ and ϕ c) Su ppl y the valu e of the in pu t sig nals to the BLU Then m easu re the BLU at position p i to obtain the lu m inance L vi ( θ, ϕ (I n case of i = 0, th e posi tion im pli es th e centre of the acti ve area of the BLU ) ) The LMD sh ou ld be carefu l ly checked before m easu remen ts, considering the fol lowing elemen ts: • sensitivi ty of th e measu red qu an ti ty to the m easu rin g l ig h t; • errors caused by veiling g lare and lens flare (i e , stray lig ht in an optical system) ; • ti g of data-acqu isi tion, low-pass fi ltering and aliasing -effects; • l i nearity of detecti on and data-con version; • m easu remen t size and fi eld of view (FOV) To ensu re l um i nance accu racy for the inten ded LED sou rces, a broad ban dwidth LMD shou ld be cali brated usi ng a spectrom eter wi th a ban dwidth n m or l ess The lu mi nance of BLU sh ou ld be measu red by synchron izing the LMD with th e BLU refresh rate, or in tegrati ng th e measu red lum in ance over a nu mber of fram es I EC 62595-2-1 :201 © I EC 201 –9– N OTE I SO/CI E 9476 [1 ] i s avai l abl e for referen ce to th e LM D eval u ati on proced u res 5.2.3 Luminance uniformity or non-uniformity Lu m in ance u niformi ty, U, or lu minance non-un i form ity, NU, i s a calcu lated valu e of h ow well th e lu minance remains constant over th e surface of the active area of the BLU , and it is closel y related to lu minance m easu remen t itsel f The lu m in ance un i form ity or non-un iform ity m easu rem ent is sensitive to th e testin g posi tions Typical l ayou ts of measu rem ent poin ts over th e BLU surface are sh own in Fi gu re [2] Lum in ance n on-u n i formity, NU, is usu all y calcu lated using the followin g equation : NU = L vM − L va L va One of the followin g four equ ations is also used widely in display indu stries U= Lvm , L vM U= LvM , L vm L vM − L vm , L vM NU = NU = L vM − L vm L va wh ere L vM is the maximu m lu m in ance valu e of all measu remen t poin ts in Fi gu re 4; L vm is the minimu m lu m in ance; and L va is the averag e l u minance calcul ated as: L va = N L vi N i =1 ∑ wh ere N i s the nu m ber of m easu remen t poin ts; and L vi is l u ance of the ith measuremen t poin t Typical measu rem en t procedu res of l um inance u niform i ty U are as follows At first, speci fied inpu t current and vol tage are su pplied to th e BLU to be measured Secondl y, l u ance is m easu red at each poi n t on the BLU on ei th er fi ve (positions p , p 1 , p , p , an d p 23 ) or ni ne (positi ons p , p , p 1 , p , p , p , p , p 21 , and p 23 ) points This measu rem en t is carri ed out usu all y at normal an g le; however, oth er ang les can also be consi dered for certain pu rposes N u m bers i n squ are brackets refer to th e Bi bl i og raph y – 10 – I EC 62595-2-1 :201 © I EC 201 H p p 20 p p p 11 p 12 p 13 p p 14 p p 19 p 18 p 17 16 p 15 10 V 10 V 10 V p 10 p p p p p 21 p 24 p 22 p p 23 V p 10 H 10 H 10 H IEC Figure – Examples of measurement point layout 5.2.4 Spectral power distribution A spectral power distribu tion of BLU , SBLU ( λ ) is m easu red u sing a spectrom eter or an equ ivalent optical instru m en t The m easu ri ng procedu res are i n accordance with 2 and To ensu re l um in ance accu racy for the in tended LED sou rces, a broad bandwidth LMD sh ou ld be cal ibrated using a spectrom eter with a bandwidth nm or l ess 5.2.5 Chromaticity CI E 931 chromaticity coordin ates (I EC 60050-845:1 987, 845-03-28 [3] and I SO 1 664-1 [4]) , the BLU su rface of the active area are obtained u sin g the tristim u lu s values, X Y Z calcu lated from m easured spectral power distribu tion S( λ ) g iven i n (see I EC 62595-1 -2) The correlated colou r temperatu re (CCT) can also be u sed x y z on , , , , N OTE Correl ated col ou r tem peratu re (CCT) i s d efi n ed i n I EC 60050-845: 987, 845-03-50 Th e cal cu l ati on m eth od from th e m easu red ch rom ati ci ty d ata i s speci fi ed i n CI E pu bl i cati on 5: 2004 [5] Robertson ’ s [6] proced u re i s avai l abl e for an actu al com pu ti n g prog ram Th is m easu remen t is carried ou t u su al ly on on th e axis n orm al to the su rface of th e BLU , h owever, other ang les can also be considered for certain purposes 5.2.6 Colour uniformity Colou r un i formi ty shoul d be evalu ated using CI E 976 ch romatici ty (I EC 60050-845:1 987, 845-03-53 [3] and I SO 1 664-5 [7]) di fferences between the cen tre and the other poin ts on th e BLU su rface, u sing th e followi ng equ ation : ∆ u’v’ = Max [ { ( u’ i – u’ cen tre + v’ i – v’ cen tre ) ( ) } /2 ] i = , 2, , Another equ ation u sed is as fol lows: ∆ u’v’ = Max wh ere [ { ( u’ i – u’ j + v’ i – v’ j u’ = x / –2 x + y +3 v’ = 9y / –2 x + y +3 x, y , z are CI E 931 ) ( ); ( ); ( ) } /2 ] i,j = , 2, , chromaticity coordin ates The same measu remen t poin ts as shown in shou ld be u sed I EC 62595-2-1 :201 © I EC 201 5.2.7 – 11 – Ang ular luminance uniformity An gu lar performance of th e LED BLU directly affects the wh ole display performances The lu mi nance valu es at ang les (0°, 0°) , ( θ, 0°) , ( θ, 90°) , ( θ, 80°) and ( θ, 270°) in th e polar coordin ate system defin ed i n shou ld be m easu red as in Fi gu re Measu remen t at additi onal an g les shou l d be carried ou t if n ecessary The measurements shou ld be carried ou t at each poin t of the BLU shown in Fi gu re y BLU 2:00 x 3:00 ( 9:00 θ θ θ, 90 °) θ θ 6:00 ( (0 °, 0°) ( θ, θ, °) LMD 80°) z ( θ, 70°) IEC Figure – Angular luminance uniformity measurement 5.2.8 Ang ular colour uniformity The ang u lar colou r u n iformi ty of the BLU affects th e wh ole display an gu lar performance The ang les can be sel ected in th e same man ner as th e ang u lar lu m inance u n iformi ty g iven in I t shou ld be in accordance wi th 6, to obtai n the chrom atici ty differences between the norm al ang le and the other four ang les 5.2.9 5.2.9.1 Measurement methods of block-wise BLUs General A block-wise BLU is a seg men ted BLU which is di vided two-dim ensionall y for synchronization wi th an LCD panel for th e pu rpose of local dim m ing Lu minance of each block is optimall y troll ed by m odu lati ng LED arrays Th e block seg men tation is determined dependi ng u pon th e whole display design Su bcl ause speci fi es the fu ndamen tal measurin g methods for th e block-wise BLU , assu m ing basical l y direct-li t BLU s The block segmen tation of the block-wise BLU an d how to trol the LED array for dim ming the bl ocks shall be reported A sim il ar measuri ng meth od to block segm entation in direct-li t BLU s in can be appl ied to edge-l it BLU s N OTE Detai l s of th e m easu ri n g m eth ods m ay be si dered i n th e fu tu re – 12 – 5.2.9.2 I EC 62595-2-1 :201 © I EC 201 Checkerboard pattern Checkerboard pattern is u sed for measuri ng the block-wise BLU An exam ple of ch eckerboard test pattern is sh own in Fig u re The stray lig ht shou ld be m in i mized u sing an appropriate m eth od such as fru stu m (see I SO 9241 -305 [8]) IEC Figure – Example of checkerboard pattern (8 segments × segments) for block-wise BLU 5.2.9.3 Single block white pattern Onl y a sing le block is turn ed ON to m easu re th e l ig h t spread fu nction , i e the optical leakag e or optical noise in the n ei g hbouring bl ocks i n th e block-wise BLU An exampl e of a si ng le block whi te pattern (cen tre) is shown i n Fig ure IEC Figure – Example of single block white pattern 5.2.9.4 Single block black pattern Onl y a sing le bl ock is tu rned OFF as a black pattern , which is u sed for measuring the li gh t di ffu sion , the lig h t leakag e characteristic in a block and for eval uating the optical noise in a sing le block i n the bl ock-wise BLU An example of a sing le block black pattern (centre) is sh own in Fi gu re The stray lig ht shou ld be m in i mized u sing an appropriate m eth od su ch as fru stu m (see I SO 9241 -305 [8]) I EC 62595-2-1 :201 © I EC 201 – 13 – IEC Fi g u re – E xam p l e o f s i n g l e b l o ck b l ac k p atte rn 5.2.9.5 I n c o h e ren t p o i n t s p re ad fu n cti o n Wh en a sing l e block tu rns on and the rest of the blocks tu rn off as in 3, the li gh t spread fu ncti on (LSF) is defined as a spatial lu minance profile spreading ou twards An example of LSF is sh own in Fi g ure Based on LSF, imag e si gnals of the LCD are control led for optimizin g im ag e qual ity IEC Fi g u re – E xam p l e o f i n co h e ren t p o i n t sp re ad fu n cti o n I n order to m easure the LSF, a sing le ON -block wh ite pattern as in Fi gu re shall be applied Al thou g h LSF is a tin u ou s fu nction , the measu remen t of the distribu ti on profile of this fu ncti on shall be carried ou t at predeterm in ed positions The valu es between the posi tions shou ld be i nterpolated The procedu res for th e measu remen t are as fol lows: a) b) c) d) Select th e block under test Determin e th e posi tion and n u mber of measuring poin ts M easu re the l u ance of each positi on as shown in 2 (lu m in ance measu ring meth od) I n terpolate between the posi tions i f necessary The resu l ts of each procedu re shall be reported The posi tion and nu mber of measu rem en t poin ts can be determ ined by manu facturers Measu remen t poin t size and field of vi ew (FOV) , which are determ ined by an aperture size of th e LMD and measurem en t distance from BLU to LMD, sh al l be carefu ll y selected and reported The m easuremen t point size shoul d be sam e or sm all er than the distance between measu rem en t poin ts, to avoid overlap The FOV of the LMD shou ld be su fficien tly smaller th an the ang l e which is formed by the imum block of BLU All the measu remen t condi ti ons are g iven i n 2 (lu mi nance measurin g methods) – 14 – 5.2.9.6 I EC 62595-2-1 :201 © I EC 201 Evaluation of optical noise Optical noise is th e am ou nt of li gh t leaki ng from ON -blocks to adjacen t bl ocks An appropriate block-wise checkerboard pattern sh all be u sed to m easure the optical n oise, for example the pattern shown in Fi g u re The procedu res for th e measu remen t are as fol lows: a) Select th e block u nder test b) Determ in e the posi tion of the measu rin g poin ts i n the OFF-block (u sually at the centre of th e block) c) M easu re th e l u ance of each measu rin g poin ts as shown in 2 (lu m in ance measu ring m ethod) I f onl y one size black bl ock does not g ive mu ch in formation , a series of sm aller blocks wi th stray l ig h t compensation shou ld be consi dered The resu lts of each procedu re shall be reported The position of measu remen t poin ts can be determined by manu factu rers The measu rem ent poi n t size an d field of view (FOV) , wh ich are determ ined by th e aperture size of the LMD an d th e measurem ent distance from the BLU to the LMD, shall be carefu l ly selected and reported The measurement poin t size sh ou ld be same as or sm al ler than the distance between measu rem en t poin ts, to avoid overlap The FOV of the LMD shou ld be su fficiently smaller th an the ang le wh ich is formed by the m inim um block of th e BLU and th e measu remen t distance All th e measu remen t diti ons are shown in 2 (lu mi nance m easu ri ng m eth od) 5.2.9.7 Optical noise evaluation in a sing le block Optical noise usi ng a sin gl e bl ock test pattern as sh own i n Fig u re is defi ned as the am ou n t of lig ht leaking from al l th e rem aini ng ON -blocks to a sin g l e OFF-block I t sh all be measured as follows: a) Select th e block u nder test b) Determ in e the posi tion of the measurin g poin ts i n the OFF-block (u sually at the centre of th e block) c) M easu re th e l u ance of each measurin g poin ts as shown in 2 (lu m in ance measu rin g m ethod) The resu l ts of each procedu re shall be reported The posi tion of measu rem en t points can be determ i ned by manu factu rers M easu remen t point size and fi eld of view (FOV) , wh ich are determ ined by the apertu re size of the LMD and the measu rem en t distance from the BLU to the LMD, sh al l be careful l y selected an d reported The measuremen t point size shou ld be same as or smal ler than the distance between measu rem ent poin ts, to avoid overlap The FOV of the LMD shou ld be su fficien tl y smal ler th an the ang le wh ich is formed by the m in imu m block of the BLU and the measu rem en t distance All th e measuremen t conditions are shown in 2 (lu minance m easu ri ng m eth ods) Other test patterns sh oul d be used if n ecessary 5.2.9.8 Optical sig nal-to-noise ratio in a block-wise BLU Optical si gnal-to-noise (S/N ) is the ratio of lu mi nance caused by an optical leakag e from an adjacent block to the lu m inance of th e block i tsel f (si gn al) I t sh al l be measu red as foll ows: I EC 62595-2-1 :201 © I EC 201 – 15 – a) Select th e block u nder test according to or b) M easu re th e l u mi nance wh en all the blocks are ON as sig nal level c) Determ in e the position of m easuring poin ts, corresponding to or as noise level d) M easu re lu m in ance of each measu ring poin ts as shown in 2 (lu ance measu rin g method) e) Calcu late the block-wise optical sig nal-to-noise ratio u si ng th e above l um in ance valu e according to or The resu lts of each procedu re shall be reported The posi tion of measu rem en t poin ts can be determ ined by manu factu rers M easu remen t poin t size and fi eld of vi ew (FOV) , wh ich are determ in ed by the apertu re size of the LMD and the measu rem ent distance from the BLU to the LMD, sh al l be carefu l ly selected an d reported The measu remen t poin t size shou l d be sam e as or smaller th an the distance between the measu rem en t points, to avoid overlap The FOV of the LMD shou ld be su fficien tl y smal ler th an th e angl e which is formed by the mini mu m block of BLU and the measuremen t distance All the m easu rem en t conditions are sh own in 2 (l u minance measuring method) Other test patterns sh oul d be used if n ecessary 2.9.9 B l o ck- b y- b l o ck u n i fo rm i t y The lu mi nance, col our, LSF, and opti cal sig n al-to-noise ratio may vary bl ock-by-block u nder certain test pattern ditions Block-by-block u n iformi ty sh ou ld be calcu lated usin g the sim il ar formu lae shown in an d I nstead of the m easu rem en t points shown in Fi gu re 4, the poi n t of each block (u sual ly the cen tre) shou ld be u sed in this m easu remen t – 16 – I EC 62595-2-1 :201 © I EC 201 Bibliography [1 ] I SO/CI E 9476:201 4, Characterization of the performance of Illuminance Meters and Luminance Meters [2] I EC 61 747-1 , Liquid crystal and solid-state display devices – Part 1: Generic 845: Lighting specification [3] I EC 60050-845, International Electrotechnical (available at http://www electropedia org ) [4] I SO 1 664-1 :2007, [5] CI E pu blication 5:2004, [6] ROBERTSON A R , Computation of correlated color temperature, J Opt Soc Am 58, 968, p 528-1 535 [7] I SO 1 664-5:2009, Vocabulary – Part Colorimetry – Part : CIE standard colorimetric observers Colorimetry temperature and distribution Colorimetry – Part 5: CIE 976 L*u*v* Colour space and u', v' uniform chromaticity scale diagram [8] I SO 9241 -305:2008, Ergonomics of human-system laboratory test methods for electronic visual displays _ interaction – Part 305: Optical INTERNATIONAL ELECTROTECHNICAL COMMISSION 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