SENS ING AMER ICAS, INC.
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SENS ING AMER ICAS, INC.
1
SENS ING AMER ICAS, INC.
LightingTechnologies,Principle,andMeasurement
SENS ING AMER ICAS, INC.
1
Lighting Technologies Principle and Measurement2 ColorRenderingProperties
2 ColorTemperature
2 LightDistribution
2 TotalLuminousFlux
2 Mura(Nonuniformity)
Color-Rendering Properties3 Fluorescent,naturalwhite,&LEDs
Color Temperature6 ColorTemperature
7 DifferencesfromColorTemperatureMeasured
UsingaPhotographicColorimeter
Light Distribution9 Lightsources
9 HowtoMeasureLightDistribution
10 LightDistributionMeasurementDevice
Total Luminous Flux
11 Luminousflux
11 HowtoMeasureTotalFlux
12 TotalFluxMeasurementDevice
Mura13 Mura
13 MuraStandards
13 SEMU
13 JEITA
13 CurrentMeasurementMethods
14 Sensorwithsensitivityneartothatofthe
humaneye
14 High-resolutionCCD
14 LowsensitivityerrorperCCDpixel
14 MeasurementDevice
14 ExampleMeasurementResults
Contents
SENS ING AMER ICAS, INC.
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Color Rendering Properties
Learnwhatcolor-renderingpropertiesareandseeforyourselfthe
relationshipbetweencolor-renderingindexesandhowsamples
lookunderdifferentlightsources.
Color Temperature
Learnthecorrelationbetweencolorandtemperature,and
seethedifferencefromcolortemperaturesmeasuredusinga
photographiccolormeter.
Light Distribution
Learnwhatlightdistributionisfromreal-lifeexamplesandsee
howtomeasureit.
Total Luminous Flux
Learnwhattotalfluxisandseehowtomeasureit.
Mura (Nonuniformity)
Learnaboutmurastandardsandcurrentmeasurementmethods.
Also,seesomeexamplesofmeasurementresultsobtainedusing
ameasuringinstrument.
LIGHTING TECHNOLOGIES, PRINCIPLE, AND MEASUREMENT
LIGHTIN
GTECHN
OLO
GIES,PRIN
CIPLE,AND
MEASUREM
ENT
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Totheeye,theyallseemwhitebutthenaturalwhitefluorescent
lamphasaslightlyhighercolor temperatureandlooksslightly
bluish.
Wemeasuredthethreelightsourcesbymountingaluminanceadapteronthe
KonicaMinoltaSpectroradiometerCS-2000.Ifyoucomparethemeasured
pointsonthexychromaticitydiagramatright,youcanseethatthetonesare
similarandinthevisiblerange.
COLOR-RENDERING PROPERTIESSincelongago,manhascomparedcolorsbyarrangingobjectsside-by-sideandlookingatthemundernaturallight
(sunlight).Althoughtorches,candles,incandescentlampsandotherlightsourcesarealsousedforillumination,ithasalways
beenthestandardpracticetocomparecolorsundernaturallight.
Inadditiontofluorescentlamps,LEDs(lightemittingdiodes)haverecentlybeenadoptedasilluminatinglamps.When
comparinghowobjectslookunderthesenewtypesoflampsagainsthowtheylookundernaturallight,howcloselythey
matchiscalledthe“color-renderingproperty.”Alampthatproducesahuesimilartothatofnaturallightissaidtohavea
good(high)color-renderingproperty.
Today,appliancestoresoffermanytypesoflamps(incandescent,fluorescent,LED,etc).Further,fluorescentlampsandLED
lampscomeintoneslike“white,”“warmwhite,”etc.
Intheexampleshere,weilluminatedanobjectwithaD50fluorescentlampwithgoodcolor-renderingproperty,afluorescent
lampthatwaslabeledas“Naturalwhite”andanLEDlamp.
2000
1500
250030003500
40004500
10000
D55
A
B
CD65
D75
520
510
500
490
480
470460
450
530
540
550
560
570
580
590
600
610620
650
380~440
680~780
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.000.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
Thehuechangesunderdifferentlightintg
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Next,let’silluminaterawmeatwiththethreelightsources
andseehowthemeatlooks.
UndertheD50fluorescentlamp,themeatandtheplatelook
liketheyactuallydo,butunderthenaturalwhitefluorescent
lamp,thecolortemperatureisslightlyhigherandboththe
meatandtheplatelookslightlypaler.UndertheLEDlamp,
everythingisdarker.
•Theluminanceatthesamplesurfacewasadjustedtobe
about1600luxforallthreelightsources.
•Whenasampleisilluminatedwithdifferentlightsources,
thecolormaylookdifferent.
•Thedifferenceinlampperformanceiscalledusinga“color-
renderingindex.”
•Thisindexindicateshow15testcolorslookundera
particularirradiatedlight.
•Whencomparingalightsourceagainstastipulated
referencelightsource,anindexof100isthebest.
*Becauseofitslowcolor-renderingindex,theLEDlampusedthis
timemadethemeatandplatelookdark,butthemeatandplatecanlook
fresherwithanLEDlamphavingahighercolor-renderingindex.
X
Y
Correlatedcolor
temperature
D50 fluorescent lamp
0.3407
0.3518
5173
Natural white fluorescent lamp
0.3372
0.3496
5308
LED lamp
0.3465
0.3662
5004
SpectraldistributionofD50fluorescentlamp,naturalwhitefluorescentlampandLEDlampRelativeintensity
aD50 Naturalwhitefluorescentlamp fluorescentlamp LEDlamp
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Weobtainedthefollowingcolor-renderingindexesfromthespectraldistributionmeasuredwithaSpectrophotometerCS-
2000modifiedforluminancemeasurement.ItcanbeeasilycomputedusingtheDataManagementSoftwareCS-S10wfor
theCS-2000.
Raisthe“meancolor-renderingindex.”Itistheaverageofindexes
R1~R8andisarepresentativevalueofcolor-renderingindexes.
R9~R15aretermed“specialcolor-renderingindexes,”withparticular
interestoftenbeingshowninR9(highlyvividred)andinR15.
R9isusedforevaluationofthereproductionofred,andthebig
differencesinvaluesbetweenthethreetypesoflightsourcesalsogive
anindicationofhowmuchthecolorofthemeatseenunderthedifferent
lightsourceswillvary.
D50 fluorescent lamp
Natural white fluorescent lamp
LED lamp
Ra
91
79
68
R1
94
89
65
R2
91
89
74
R3
86
54
79
R4
90
82
68
R5
93
81
65
R6
89
72
62
R7
90
86
81
D50 fluorescent lamp
Natural white fluorescent lamp
LED lamp
R8
90
76
54
R9
77
16
-39
R10
78
40
36
R11
93
63
61
R12
81
55
31
R13
93
92
66
R14
92
70
88
R15
91
92
59
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COLOR TEMPERATURE
Asyouknow,thetwinkling(fixed)starsintheevening
skyhaveafaintcolor.Itisalsoknownthatthesurface
temperatureofbluishstarsishigherthanthesurface
temperatureofreddishstars.
Blacksmithsjudge
thetemperature
ofahotironfrom
itscolor(red).This
shouldgiveyouan
ideathatsomesort
ofcorrelationexists
betweencolorand
temperature.
Anidealradiator(blackbody)absorbsallexternal
electromagneticradiationandre-emitstheradiation.Asthe
temperatureofablackbodyincreases,itchangescolorinthe
orderofred→yellow→white→bluewhite.
Ifthischangeincolorduetotemperatureisplottedonanxy
chromaticitydiagramasshowntotheright,itlookslikethe
blackcurvedlineinthelowercenterofthediagram.Thisline
iscalledthe“blackbodylocus”andthecolortemperatureson
thislinearecalled“absolutecolortemperatures.”
Butnotallexistinglightsourcesareonthisblackbodylocus.
Infact,mostlightsourceshavingawhitechromaticitypoint
areslightlyoffofthisblackbodylocus.Insuchcases,the
colortemperaturecanbeobtainedusingtheisotemperature
linesdrawnacrosstheblackbodylocus.Thecolor
temperatureisthenreferredtoas“correlatedcolor
temperature.”
red→yellow→ white→bluewhite
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Colortemperatureandcorrelatedcolortemperatureare
generallyusedasanindextorepresentcolorswithinarange
ofwhite(reddishwhite,yellowishwhite,whiteandbluish
white)andcanbemeasuredwithourChromaMeterCL-200/
CL-200A(forilluminanceandchromaticitymeasurement),
ChromaMeterCS-200(forluminanceandchromaticity
measurement),SpectroradiometerCS-2000/2000Aand2D
ColorAnalyzerCA-2000.
DIFFERENCESFROMCOLORTEMPERATUREMEASUREDUSINGAPHOTOGRAPHICCOLORIMETER
Photographiccolorimeters
areseparatefromtheabove
industrial-grademeasuring
instruments.Althoughthey
claimtomeasurecolor
temperature,thepurposeisto
determinetheappropriatefilter
valuesfortakingpictures.The
colortemperaturetakenwith
suchcolorimetersiscalled“photographiccolortemperature.”
Althoughthesensorsoftheindustrialinstrumentsdescribed
earlierareintendedtocloselymatchthesensitivityofthe
humaneye,thesensorsofphotographiccolorimetersare
similartothesensitivityofcolorphotographicfilm.
Fig.1belowontheleftshowsthesensitivityofthehuman
eye,andFig.2belowontherightshowsthesensitivity
ofcolorphotographicfilm.Youcanseethattheyare
completelydifferent.
Becauseofthis,if,forexample,thecolortemperatureof
thesamelightsourcewasmeasuredwithaChromaMeter
andaphotographiccolorimeter,theresultwouldbetwo
completelydifferentvalues.
Whenmeasuringcolortemperatureforpurposesother
thantakingpictures,anindustrialmeasuringinstrumentis
needed.
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Asareference,thegraphsbelowshowtheresultsofacomparisonbetweenthecorrelatedcolortemperatureofawhiteLED,
coloredLEDandfluorescentlamp(warmwhite,naturalwhiteanddaylightwhite)measuredusingourSpectroradiometer
CS-2000+Luminanceadapterandthecolortemperaturemeasuredusingaphotographiccolorimeter.Thehorizontalaxisis
thecorrelatedcolortemperaturemeasuredusingourSpectroradiometerandtheverticalaxisisthedifferenceinmeasured
valuesbetweenthespectroradiometerandphotographiccolorimeter.
Youcanseethattherearewidedifferencesinmeasuredvalueswithsomelightsources.Thecorrelatedcolortemperature
measuredusingtheSpectroradiometeris,inprinciple,neartothetruevalue.Butitshouldbenotedthatthisisjustone
example.Itisnotguaranteedthatthesameresultswouldbeobtainedifadifferentphotographiccolorimeterwereusedor
evenifthesamesampleweremeasuredusinganotherphotographiccolorimeterofthesamemodelasthatusedthistime.
Relatedstandard:JISZ8725MethodsforDeterminingDistributionTemperatureandColorTemperatureorCorrelatedColorTemperatureofLightSources
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LIGHT DISTRIBUTION
Alllightsourcesemitlight,butinwhatdirection(angle)that
lighttravelsandhowstrongitisarecollectivelydescribedas
the“lightdistribution.”
Lightdistributionpropertiesareusedtodeterminewhatlight
sourcewouldbegoodfor,forexample,astronglydirectional
lightoradiffusedlight.Withlightingfixturesandthelike,
theyaresimilarlymeasuredandevaluatedtogetherwithlight
sources,shades,backgrounddeflectorpanels,etc.
“Lightdistribution”isdefinedinJISZ8113“Lighting
Vocabulary.”Thatdefinitionreads:“theangularchangeor
distributionofluminosityofprimarylightsources,secondary
lightsources(includinglighttransmissionandreflectionof
opticalmaterials,etc.)andlightingfixtures.”Asexamples,
Fig.1ontheleftaboveshowsthemeasuredlightdistribution
ofabulletLEDandFig.2ontherightaboveshowsthesame
forasurfacemountedLED.
Withfluorescentfixtures,thelightdistributionactually
includestheeffectofpartsotherthanthebulb.
Onemethodforcategorizinglightdistributionisthe
internationalmethod.Itdefinesthelightdistributionas
theratioofupwardmovingfluxfromthelightsourceto
thedownwardmovingflux.Inthiscategory,thefixture’s
configurationcanbeaddressedandaroughideaofthe
utilizationfactor,animportantfactorinlightingdesign,can
beunderstood.
HOWTOMEASURELIGHTDISTRIBUTION
Lightingdistributionmeasurementisbasicallydividedinto
twoapproaches.Oneistopositionsensorsacertaindistance
fromasampleandmeasurethelightdistribution.Inthis
case,resultsareobtainedbymeasuringfrommultiplepoints
concentricallylocatedaroundthesample
LIGHTD
ISTRIBUTION
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Theotherapproachistomeasuredistributionatdifferent
distancesfromthesampleusingameasuringdevice
consistingofaCCDsensorandanopticalsystemwithan
extremelywide-anglelenssimilartoafisheyelens.
LIGHTDISTRIBUTIONMEASUREMENTDEVICE
Konica-Minoltacreatedacustomizedlightdistribution
measurementdevicewithamovingsensortomeet
customers’needs.Inaddition,threetypesofsensorscan
beused:spectroradiometricsensor,colorimetricsensorand
luminancesensor.
Illustration
Merits
Demerits
Moving Sensor
•Anglepitchandsensordistancecanbefreely
set.
•Lessexpensivethanastationarysensor
setup
•Longtimerequiredtocompleteall
measurements
Stationary Sensor
•Shorttimerequiredtocompleteall
measurements
•Moreexpensivethanamovingsensorsetup
•Restrictedbysampleshapeandsize
Source:TextbookforLightingFundamentalsClass,Illumi-natingEngineeringInstituteofJapan
LIGHTD
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TOTAL LUMINOUS FLUXLuminousfluxisavalueforevaluatingtheradiantfluxbasedonthespectralluminousefficiencyfunctionofthehumaneye
andthemaximumluminousefficacy.Totalfluxistheluminousfluxradiatedinalldirectionsfromalightsourceanditisused
asameasureofbrightnessforlightingfixtures.ItsunitsareLumens(lm).
Theterms“luminosity”and“brightness”areoftenheardtoexpressaquantityoflight.Bothofthesetermsincludethe
meaningofdirectionality.Totalfluxdoesnothaveanyconnotationofdirectionality.
ΦV=Km・∫Φe(λ)V(λ)dλ
ΦV:Luminousflux
Km:Maximumluminousefficacy
φe(λ):Radiantflux
V(λ):Spectralluminousefficiency
<Examples>
Sunlight:Approx.3.6×1028lm
37Wfluorescentlamp(White):Approx.3,100lm
95Wwhiteincandescentbulb:Approx.1,520lm
Totalfluxisusedincalculationswhendesigninglightingfixtures.“Luminousefficacyofalamp,”obtainedbydividingthe
luminousfluxbytheelectricalpower(powerconsumption),hasalsobeenusedfromanecologicalperspectiverecently.
HOWTOMEASURETOTALFLUX
Therearetwowaystomeasuretotalflux:byusinganintegratingsphereorbylightdistributionmeasurement.Theintegrating
spheremethodplacesasamplelightsourceinanintegratingsphere(aspherethatishollowwiththeinnerwallpainted
ahighlydiffusivewhitecolor)andreceivingthelightwithasensor.Inthiscase,thesensormustbecalibratedagainsta
referencelightsource.
Withthelightdistributionmeasurementmethod,thesensorismovedconcentricallyaroundthesampleatasetdistance,and
thelightingdistributionismeasured.
TOTALLUM
INO
USFLUX
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TOTALFLUXMEASUREMENTDEVICE
Konica-MinoltaSensingofferscustomizedintegratingsphereandlightdistributionmeasurementsystemstomeetcustomer
needs.(ContactKonica-MinoltaSensingformoreinformation.)
Fortheintegratingspheremethod,spheresizesfrom6to40inchesindiameterareavailable.
Approach
Illustration
Merits
Demerits
Integrating Sphere
•Measurementscanbedoneinashortamount
oftime.
•Simplestructure
•Sensormustbecalibratedagainstareference
lightsource.
•Self-absorptioncausedbydifferencesin
shapefromthereferencelightsourcemustbe
compensatedforinmeasurements.
Light distribution measurement
•Lightdistributionpropertiescanalsobe
understood
•Longtimerequiredtocompleteall
measurements
•Notsuitedforsamplesthatradiatelightinall
directions
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MURA
Withthelargerprojection
TVsandprojectorsof
recentyears,uneven
luminanceandchromaticity
indisplayedimagesreadily
standout.“Mura”isaterm
usedtodescribethenonuniformityperceivedwhenaperson
looksatadisplay.
Luminancecross-section(Luminancedistributionofdisplay
seeninasingledimension)Perceivedunevenpoints,inthe
abovediagram.
Unevenluminanceandchromaticityareeachbelieved
tobecausedbymultiplefactorssuchascontrast,area,
etc.Addtothistheverybigfactorofhumanvisionandit
becomesverydifficulttodefineitclearly.
MURASTANDARDS
1. SEMU
Despitethedifficultyofdefiningmura,the“SEMU”definition
wasstandardizedin2002.Shortfor“SEMIMuraUnit,”itwas
standardizedasaunitofmeasurementbySEMI*.Itapplies
notonlytoLCDsbutalsotoFPDs.Measurementrequires
a2-dimensionalcolorimeterthatnotonlyrequiressample
luminancetobemeasuredbutalsothesizeofthemura
area.
*AcronymforSemiconductorEquipmentandMaterials
International,anonprofitindustrialorganizationtowhich
world-prominentmanufacturersofsemiconductors,flatpanel
displaysandassociatedmaterialsbelong.
2. JEITA
EIAJED-2810“MeasuringMethodsforOrganicELDisplay
Modules”releasedin2000bytheJapanElectronicsand
InformationTechnologyIndustriesAssociation(JEITA)
containsmethodsformeasuringluminanceuniformityand
whitechromaticityuniformity.However,theyarebasedon
measuredluminanceandchromaticityvaluesofanH3x
V3(9points)displayarea;thereforethemethodsarenot
effectiveformeasuringmuraoutsideofthese9points.
CURRENTMEASUREMENTMETHODS
Currentlytherearenostandardizedrulesformeasuring
mura,buttoobtainsomesortofobjectiveevaluation,itis
bettertoperform2-dimensionalmeasurementsofluminance
andchromaticityusingCCDsensors.A2-dimensional
colorimeterforthispurposerequiresthefollowingfunctions
andperformance.
SENSORWITHSENSITIVITYNEARTOTHATOFTHEHUMAN
EYE
OrdinarycolorCCDshavedifferentsensitivitiesthanthe
humaneyedoes,makingitdifficulttomeasureluminance
andchromaticitycorrectly.
HIGH-RESOLUTIONCCD
Witharesolutionof200×200,forexample,theluminance
variationsofsmallareascannotbecaptured.
MURA
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LOWSENSITIVITYERRORPERCCDPIXEL
IfmuraoccursinthesensitivityofindividualCCDpixels,theluminancedistributionandchromaticitydistributioncannotbe
accuratelymeasured.
MEASUREMENTDEVICE
Konica-Minoltadevelopedthe2DColorAnalyzerCA-2000Awitharesolutionof980x980,withsensorsensitivitynearto
thatofthehumaneyeandminimalsensitivityerrorperCCDpixel.Thedrivesoftwareincorporatesafunctionforaccentuating
mura.Thisfunctionobtainstheaveragemuraofanareaofaset
sizearoundeachmeasurementpointandusesittosmooththe
data.Itdisplaystheratioofeachmeasurementpointdataand
averageddataas2-dimensionalresults.Therefore,whensample
luminanceisuniform,itaccentuatesanywherewithinthedisplay
whereluminanceisloworhigh.
EXAMPLEMEASUREMENTRESULTS
A:Luminancecross-sectionB:MovingaverageofAC:A/B
MURA