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OpticalsafetyofLEDlighting
1stEdition,July2011
1.
BackgroundWiththephasingoutofincandescentlampsintheEuropeanUnionaswellassimultaneouslyinmanyothercountries,theintroductionofmanynewLEDbasedlightsources(lamps,modules)andluminaires,raisesthequestion
as towhether the spectral characteristicsof the LED and Energy
Saving fluorescent lamps
(CFLintegrated)aregoodenoughtoreplacetraditionalincandescentlamps.Theseconcernsaregenerallyraisedbygroupsofpeoplewithahighsensitivityforcertainradiationontheirskinoreyes,especiallyforradiationintheUVandbluepartofthespectrum.Thisdocumentwillfocusonwhite
lightsourcesandtheiruse inhouseholds.2.
SummarystatementItisoftenemphasizedthatLEDbasedlightsourcesaredifferentfromtraditionallampsinthattheycontainhigherproportionsofbluewavelength
lightandarethusmore likelytocauseproblemssuchasblue lighthazard.
Confronted with this question, the European Lighting Industry
represented by ELC &
CELMA,presentsadetailedevaluationofthephotobiologicalsafetyofcommonLEDlightsourcesfordomesticuseincomparisontotraditionallamps.Thefocusisonwhitelightsourcesusedinhouseholds.Tosummarize
thekey findings,LEDsources (lampsorsystems)and luminairesaresafe
totheconsumerwhenusedas intended. Intermsoftheir
levelofphotobiologicalsafety,LED
lampsarenodifferentfromtraditionaltechnologiessuchasincandescentlampsandfluorescenttubes.TheportionofblueinLEDisnotdifferent
from theportionofblue in lampsusingother technologies at the same
colour
temperature.AcomparisonofLEDretrofitproductstothetraditionalproductstheyareintendedtoreplacerevealsthattherisklevelsareverysimilarandwellwithintheuncriticalrange.Nevertheless,
looking straight into bright, pointlike sources (LEDs, but also
other strong pointlike
lightsources,likeclearfilamentordischargelampsandincludingthesun)shouldbeprevented.However,whenpeople
happen to look into a bright light source accidentally, a natural
protective reflex occurs
(peopleinstinctivelyclosetheireyesorlookawayfromthesource).Itneedstobementionedthatblue
lightexposure is importanttohumanbeings.Blue
lightwithapeakataround460480nmregulatesthebiologicalclock,alertnessandmetabolicprocesses.Innaturalconditions,outdoordaylightfulfilsthisfunction.Yet,peoplespendmostofthedayindoors(officesetc.)andareoftenlackingthenecessaryblue
lightexposure.Blueandcoolwhite lightsourcescanbeusedtocreate
lightingconditionssuchthatpeoplewillreceivetheirdailyportionofbluelighttokeeptheirphysiologyintunewiththenaturaldaynightrhythm.Duetothehighlyflexibleapplicationpossibilities,LEDbasedlightsourcesareparticularlywellsuitedforthatpurpose.
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3. LEDandopticalsafetyOpticalsafety refers to
theprevention1ofhazards throughoptical radiation (electromagnetic
radiationofwavelengthsrangingfrom100nmto1mm).Effectsontheeyesaswellastheskinareconsidered,alsoforthosepeoplewithahighersensitivity.Inresponsetotheconcernsraisedbythelastgroup,Annex1providesmoredetailedconsiderationsforthisspecificgroup.Commonly
discussed hazards affecting the eye are blue light hazard (BLH) and
agerelated
maculardegeneration(AMD)whichcanbeinducedoraggravatedbyhighintensitybluelight.Whenlookingdirectlyintoabrightlightsource,aphotochemicaldamagetotheretina(bluelighthazard)canoccur,dependingontheintensityinvolvedandthetimeofexposure.Peoplearefamiliarwiththisphenomenonfromlookingatthesun.Topreventretinaldamages,appropriatespectaclesmustbewornwhenobservingasolareclipse,forinstance.Onabrightandsunnyday,however,anaturalreflexoccurs(eyelidclosereflex,aversion)thatprotectstheeyefrombeingharmed.Furthermore,UV(ultraviolet)mayaffecttheeye,causingcataractorphotokeratitis
(sunburn of the cornea); IR (infrared) radiation can induce IR
cataract (also known
asglassblowerscataract);andradiationofallwavelengthsatextreme
intensitiescan leadtoretinalthermalinjuries.Optical
radiationcanalsoaffect theskincausing forexamplesunburns,or,
inseverecases,cancersuponlongterm UV exposure. There exist certain
groups of patients, e.g. suffering from lupus
orphotodermatoses,whoareparticularlysensitivetoUV(andsometimesalsobluelight)radiation.Notethattheabovementionedeffectsarepredominantly
causedbynatural sun light; someof
themcanneverbeevokedbyartificiallighting.Nevertheless,theopticalsafetyofartificiallightsourcesneedstobeguaranteedand
lightsensitivepatients areprovidedwith appropriate lamps that are a
good and safe alternative toincandescentlamps.4.
PhotobiologicalriskassessmentandconclusionsThephotochemicalblue
lighthazard canbeevaluatedon thebasisof the standardEN62471.The
latterclassifieslightsourcesintoriskgroups0,1,2and3(from0=noriskthroughto3=highrisk).Thesunwouldbe
classified as being in the highest risk group. CELMA and ELC member
companies ensure that
theirproductscomplywiththephotobiologicalsafetystandard.Riskscanbeallocatedtotheriskgroupsaccordingtodifferentmeasurementcriteria:Onemethodmeasures
the distance atwhich an illuminance of 500 Lux is attained (a
typical value forgeneral
lightingpurposes).AccordingtoEN62471,the500Luxcriterionmustbeusedfor
lamps intendedfor general lighting (including lamps for lighting
offices, schools, homes, factories, roadways,
orautomobiles).Asecondcriterionmeasuresphotobiologicalsafetyfromadistanceof200millimetres.The200millimetrecriterion
is tobeused forallother lamps (including forexample lamps
forsuchprofessionalusesas filmprojection, reprographic processes,
sun tanning, industrial processes,medical treatment and
searchlightapplications).It is fundamentallypurposeful tomake
thisdistinctiononedoesnot look intoaceiling luminaire in theoffice
fromadistanceof200millimetres,butpossibly incertain
industrialapplicationsworkersmightberequired to look into
lightsources
fromashort200mmdistance,e.g.duringqualitycontrolprocesses.
Insuchcasesspecialinstructionsareneededtopreventeyedamage.When
light sourcesareplaced ina luminaire, theRG classification can
changeby theopticsused in theluminaire:
1.
IncasealuminaireintegratealightsourceclassifiedRG0orRG1,nonewtestsarenecessary
1ExposurelimitsdefinedinthestandardEN62471areinEuropeanregulation(directive2006/25/CE)
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2. Incasea luminaire isnot intendingtochangean integrated
lightsourcewithclassificationRG2orRG#3,nonewtestsarenecessaryandproductinformationshallindicatethementionedRGclass.
3.
IncasealuminaireischangingtheoriginalcharacteristicsoftheusedlightsourceRG2orRG3inanyform,anewmeasurementisneededtoclassifytheluminaire.
4.1ConclusionsonbluelightemissionEvaluationatadistanceproducing500Lux:Takingthe500Luxcriterionasthemeasurementbasis,noneoftheLEDproductsbelongstoriskgroup2.ThiswasalsoconfirmedbyastudyoftheFrenchagencyforfood,environmentalandoccupationalhealth&safety(ANSES)in2010whichfoundthatevenhighoutputdiscreteLEDsareclassifiedintoriskgroups0or1ifthe500Luxcriterionisapplied.LEDcomparedtootherlightsourcesWith
regard to photo biological safety, LED is not fundamentally
different to lamps using
traditionaltechnologies,suchasincandescentorfluorescentlamps.TheportionofbluelightinLEDisnothigherthantheportionofbluelightinlampsusingothertechnologiesatthesamecolourtemperature(seefigure2
inannex 3with the blue hazard irradiance values EB of awide range
of productswith comparable
ColourTemperature).IfLEDretrofitproductsareobservedincomparisontotheproductswhichtheyareintendedto
replace (e.g. LEDMR16 vs.HalogenMR16,ora LED retrofitwith screwbase
vs. frosted
incandescentlamp),itappearsthattheriskgroupratingsaresimilar.
Figure1:relativespectralpowerofvariouslightsources
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PrecautionarymeasureswithregardtochildrenThelensofachildseyefiltersbluelightlessefficientlythananadultslens.Childrenarethusmoresensitivetobluelighthazard.Therefore,atplacesfrequentedbychildrenparticularcaremustbetakentoensurethatlampsandluminairesarechosenandinstalledinsuchawayastoavoidpeoplelookingdirectlyintothelightsource.ItisnotnecessarythatLEDs(orbluelightingeneral)areavoidedinanenvironmentwithchildrenpresent,forthereasonsstatedabove.Ifusedacrossabroadsurfaceorarea,inawaywhichdoesnotproduceglare,even"pure"bluelightiscompletelyharmless;regardlessofwhetheritistheblueindaylightorproducedbyLEDsorotherlightsources.GuidanceforpeoplewithhighsensitivityforbluelightTheabovestatementsarevalidforhealthypeopleinthegeneralpublic.Peoplewithhighlysensitiveskinoreyes
for blue lightmay bewise to investigate alternative light sources
that operate on amore specificradiation band not covered by the
applied action curves that cover a broad range of radiations.
Thecomparativedatagiven intheannexesofthispaperservetogiveguidance
inselectingthebestavailabletypeoflightsourceforagivensensitivity.ThebiologicalimportanceofbluelightItneeds
tobementioned thatblue lightexposure is important
tohumanbeings.Blue lightwith apeakaround 460480nm regulates the
biological clock, alertness and metabolic processes. CELMAELC
hasinstalledaspecialworkinggrouptotranslatethesefindingsintopracticalapplicationnormsandstandards.In
natural conditions, outdoor daylight fulfils this function. Yet,
people spend most of the day
indoors(officesetc.)andareoftenlackingthenecessarybluelightexposure.Blueandcoolwhitelightsourcescanbeusedtocreate
lightingconditionssuchthatpeoplewillreceivetheirdailyportionofblue
lighttokeeptheir physiology in tune with the natural daynight
rhythm. Due to the highly flexible
applicationpossibilities,LEDbasedlightsourcesareparticularlywellsuitedforthatpurpose.
4.2Conclusionsonultravioletradiation(UV)LED based light sources
do not emit any UV radiation (unless specifically designed for that
particularpurpose).Therefore,theyarenotharmfultopeoplewithaspecificsensitivityforcertainUVradiationandcanbring
relief tocertaingroupsofpatients. In this respect,LEDbased light
sourcesprovideadvantagesovertraditionalincandescent,halogenandCompactFluorescentlamps.FormoredetailsseeAnnex2.4.3Conclusionsoninfraredradiation(IR)In
contrast tomost other light sources, e.g. halogen and incandescent
lamps, LEDs hardly emit IR
light(unlessspecificallydesignedtoemitacertaintypeof
IR).Foravailabletypesof indoor lightsourcesthe
IRradiationisnotpowerfulenoughtoposeanyriskstohuman.
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Annex1:EffectsofopticalradiationoneyesandskinPotentialeffectsontheeyeCommonly
discussed hazards affecting the eye are blue light hazard (BLH) and
agerelated maculardegeneration (AMD)which can be induced or
aggravated by high intensity blue light.
Furthermore,UV(ultraviolet)may affect the eye, causing cataract or
photokeratitis (sunburn of the cornea); IR
(infrared)radiationcaninduceIRcataract(alsoknownasglassblowerscataract);and,radiationofallwavelengthscanleadtoretinalthermalinjuriesatextremeintensities.Togivealittlemorebackgrounddetails:
Bluelighthazard(BLH)isdefinedasthepotentialforretinalinjuryduetohighenergyshortwavelength
light.Atveryhighintensities,bluelight(shortwavelength400500nm)canphotochemicallydestroythephotopigments
(and some other molecules) which then act as free radicals and
cause
irreversible,oxidativedamagestoretinalcells(uptoblindness).Forsuchan
injuriouseffecttooccur,threefactorsarecritical:first,thespectralirradiancedistribution(relevantistheproportionthatfallsintotheactionspectrum
forblue lighthazard, inmathematical terms: the integrated spectral
irradiancedistributionweightedwiththeactionspectrum);second,theradiance(athigherradiance,morephotonsare
likelytohitphotopigments and causedamages); and, third,
thedurationofexposure (at longerexposure,effects
increasesteadily).Forexample,whengazingdirectlyatthesun,theretinacanbe
injuredveryrapidlydue to theenormous radiance. Incontrast,even
though for thesky the relativeproportionofblue light
inrelationtothesky ismuchhigher,there
isnoriskofretinaldamagesbythescatteredskylightastheradianceistoolow.
Agerelatedmaculardegeneration (AMD) isaconditionofvisual
impairmentofthecentralvisualfield(macula) predominantly in elderly
people. Blue light can progress AMD. According to the
currentscientific literature,
lipofuscin,amoleculemoreandmoreaccumulating
intheretinalcellswithage,
isdestroyedbybluelightcausingoxidativedamages.NotethattheprevalenceofAMDisnothigherwithhigherexposuretobluelightinyoungeryears,e.g.,inprofessionalsworkingpredominantlyoutsidesuchassailorsorfarmers.Asforblue
lighthazard,thespectral
irradiancedistributionandradiancearetherelevant factors
influencingAMD.Butdifferent than inblue
lighthazard,AMDcannotbecausedbyaonetimeacuteabovethresholdexposure
to lightbut is instead influencedby longtermexposure
toblue(andalsogreen&yellow),possiblyevenatlowerdoses.Butnotethatbluelightisnotthemainriskfactor,instead,intherecentmedicalliterature,geneticfactors(ERCC6gene)andenvironmentalfactorsincludingage,smoking,hypertensionanddietarediscussedtocause/influenceAMD.
Cataractisadisorderthatdevelopsoverlifetime.Whenpeopleareborn,thecrystallinelensesarefullytransparent
for light. Due to natural aging and the absorption of UV radiation,
the lenses turnopaque/yellowobstructing thepassageof
light.Thesevere formof thisage relatedproblem
iscalledcataract.Asasideeffect,whenturningyellowthelensservesasabluelightfilter,and,thus,asakindofnaturalprotectionfortheretinawhenpeoplegrowolder.Inseverecases,surgicalremoval(aphakia)orreplacement
(pseudophakia)of the
lensmaybecomenecessary.Suchpatientsaswellaschildrenareoftenmoresensitivetobluelightthanhealthyadultsare.
PotentialeffectsontheskinOpticalradiation,particularlyUVcanbeharmfultotheskin.Byfarthemosthazardoussourcetoconsideristhe
sun.Sunburns (UVerythema)and skincancersdue to longtermexposure to
the sunarewellknownproblems caused by radiation. Moreover, patients
with autoimmune diseases such as lupus
orphotodermatosescanbehighlysensitivetoUVradiation,andsometimesalsoblue
light.There
isconcernamongsomepatientswhosufferfromsuchsensitivitiesthatphasingoutoftheknownincandescentlampswillleavethemwithoutlampsforindoorusethatarelowinradiationofUVandbluelight.
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Annex2:GeneralspectralcomparisonoflightsourcesusedinhouseholdsInthissection,spectraldataofdifferenttypesoflightsources(LED,CFLi,halogen)aregraphicallypresentedandevaluatedqualitatively
(aquantitativeevaluationwill follow inAnnex3). Focusof interest
ison
thespectralirradianceintheblueandultravioletpartofthedifferenttypesoflightsourcesincomparisontothetwogoldenstandardsoflightingformostconsumers:daylightandincandescentlamps.Irradiancespectralmeasurementsweredonetoobtainthespectraofanumberofcommonlightsources,allatasimilaroverallilluminancelevelof500luxandinaccordancewiththeinternationalstandardEN62471.Forreference:500
lux isalsothe light levelused inawiderangeof indoorworkplace
lightingapplicationssuchasofficelighting;inhomelightingvariesbetween50lux(TVcorner)to500lux(dinnertable,kitchen).Outdoor
lightingconditionsareamultipleof indoor lighting:5000 lux
(overcastsky) to50.000 lux
(sunnyday).Note1:Themeasuredsourcesarepresentedagainsta
logarithmicscaleas the
linearscalewouldnotbeshowingwellthedifferencesbetweenthevariouscurves.Note2:Theareaunderthespectralcurvesofthelightsourcesisameasureoftheenergyinaparticularpartofthespectrum(egblueemission).Wheninterestedinaparticularrisk,asbluelighthazardoremissionofactinicUV,theareaneedstobespectrallyweightedbytheactioncurveforbluelighthazardoractinicUV,respectively(formoredetailsontheBLHandactinicUVactioncurvesseeAnnex4).LEDspectralcharacteristicsInFigure1
top,different LED sourcesare compared toan incandescent
lampanddaylight.White LEDstypicallyshowapeak intheblue
(ataround450nmwhenaroyalblueLED
isused)andmorebroadbandemissioninthegreen/yellowpartofthespectrum.Nexttothebluepeak,adipisvisibleataround490nmthatalsofallsundertheBLHactioncurve(indicatedherebythebluehorizontalbar).ThebluepeakoftheLEDlampsiscompensatedbythedip,thereforethetotalblueoutput(givenbytheareaunderthecurve!)ofLEDof2700Kiscomparabletoanincandescentlampof2700K.Energysavers(compactfluorescentintegrated)spectralcharacteristicsIn
Figure 1 middle, spectra of two common types of energy savers (or
CFLi, Compact FluorescentIntegrated)areshownandcomparedtoan
incandescent
lampanddaylight.Typicalenergysaversspectracontainmultiplesharppeaksanddips.Again,whenconsideringtheareaunderthecurvetodeterminetheblueirradiance,peaksanddipsleveleachotherout.Notethatthehighpeaksareverynarrowandthereforedonotcontributethatmuchtotheblueirradiance(asitmightintuitivelyseemfromthegraphs).Onthelefthandside,thespectralcurvesextendslightlyintotheactinicUVactionspectrum.Butnotethatconsideringthat
thedataareplottedagainsta logarithmicaxis, theenergy in
theactinicUVpart isvery low
(!)andclearlybelowtheemissionsofnaturaldaylight.
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Figure2:Acollectionofspectrafromdifferentcommonlightsourcesisshown,togetherwitharepresentativedaylightspectrumscaledtothesameilluminancelevel.TheUVActinicandBLHactioncurves(asdefinedine.g.EN62471,seeannex4.3)areindicatedbythebrownandbluebars,respectively,thecolorintensityillustratestheeffectiveness
1E06
1E05
0,0001
0,001
0,01
0,1
1
200 400 600 800spe
ctralir
radian
cedis
tributiona
t500
lux
(W/m
nm)
wavelength(nm)
LEDlampsversusIncandescent&daylightLEDA606W2700KE27MV
LEDMR167W40D2700KGU10MV
LEDK6012W2700KE27MV
IncandA6060W2700KfrostedE27MV
LEDMR167W40D4200KGU10MV
Daylight6500KActinicUV Blue lightHazard
1E061E050,0001
0,001
0,01
0,1
1
200 400 600 800
spectral
irrad
ianced
istributiona
t500
lux
(W/m
nm)
wavelength(nm)
CFLorEnergySaving(ES)lampsversusincandescent&daylight
ESbulbT608272620KE27MV
ESburner8W8272700KE27MV
IncandA6060W2700KfrostedE27MV
Daylight6500K
ActinicUV Blue lightHazard
1E061E050,0001
0,001
0,01
0,1
1
200 400 600 800spe
ctralir
radian
cedis
tributiona
t500
lux
(W/m
nm)
wavelength(nm)
Halogenlampsversusincandescent&daylightHaloA6028WMVburner2700KE27MVHaloA6040WLVburner2830KE27MVHaloMR1645W24DIRC2850KGU5.3LVHaloCaps28W2800KUVblockG9MVR7shalogen500WwithoutcoverglassR7shalogen500WwithcoverglassIncandA6060W2700KfrostedE27MVDaylight6500KActinicUV
Blue lightHazard
1
2
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HalogenspectralcharacteristicsIn Figure 1 bottom, various
halogen lamp types are compared to an incandescent lamp and
daylight.Halogenlampspectralcurvesshowasimilarshapeasincandescentlamps:thecurvescontinuouslyincreasetowardshigherwavelengthsandbenddownwardagainintheIR.Halogenlampscanthereforeofferagoodalternativetotheincandescentlamps.Thegreen
linerepresentsahalogen lampwithan infraredcoating
(IRCcurveclearlybendsdownwards
intheIR).ThepurplelineshowsthattheUVfilteringquartzindeedeffectivelyfilterstheUV,bringingitclosetothe
incandescentcurve.TheothertypesshowmoreUVoutputthan incandescent
lamps,especiallythe500Wdoubleended lamp,butthat
lampshouldbealwaysusedwithasuitablecoverglass (flood
light)orsleeve(inuplighter);withthecoverglassthelampisclosetotheIncandescentcurve.Notethat,comparedwithdaylight,theUVoutputofall
lamps israther low,asthescale is
logarithmicnotlinear.SummaryEventhoughthespectraofLED,CFLi,halogenand
incandescent lampshavedifferenttypicalshapes,theproportionofblue
lightdoesnotvarymuchbetween
lampsofdifferenttechnologieswithasimilarcolourtemperature)andisalwayssignificantlylowerthantheblue(orUV)emissionofdaylight.Foralllampsintendedforgenerallightingapplications,theUVemissioniswellbelowtheexposurelimitsasdefinedinEN62471.LEDsusedforgenerallightingarefreeofUV(asideveryspecialtypesthataredesignedtoemitUV).
Legendforthevariouslamptypesshowninfigure1(seealsoAnnex5foramoredetaileddescription):
Halo:halogen lamps,canbe
lowvoltage(12V,3000K)ormainsvoltage(230V,2800K).Halogen lamps
canbeacapsule (caps)orreflector (MR16)operated inaspecialhalogen
lampholderor theycanbeintegrated into theoutlineof the known
incandescent lamps as a replacement for those lamps (E27MV).
FluoES:EnergySaver(popularname)orCompactFluorescentIntegrated(CFLI,technicalname),canbejustthefluorescenttube(burner)orhaveasecondshell(bulb)
Incand:Incandescentlamp,consideredbythemarketasthegoldenstandard.
LED:replacementalternativesaretaken:forincandescentbulbs,andHalogenreflectorlamps(MR16)or
T8fluorescenttubes
Daylight:theofficialCIEdaylightcurveof6500Kistaken
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Annex3:BluelightradiationdataoflightsourcesWhenevaluating the
riskofblue lighthazardposedbyLED (andother) light sources, two
fundamentallydifferentcasesneedtobeconsidered:CaseA:LookingatanilluminatedsceneInthevastamountofcases,humanslookatanilluminatedscene:Typicallydaylightilluminatesthesceneryand
adirect view into the light source, the sun, is avoided.Or, in
indoor lighting, artificial light
sourcesilluminatetheroomwhileluminairespreventadirectviewofthelightsourceprimarilytoavoidglare.Inthecaseof
lookingatan illuminatedscene,the(geometrical)propertiesofthe
lightsourcesuchasthesizeoftheareafromwhichtheradiationisemitted(measureofthedensityofradiation~=radiance)arenotrelevant.
Instead, the irradiance which refers to the radiation hitting a
surface (scene) is the
relevantproperty.CaseAcangenerallybeconsideredsafe.Togiveanexample,
lookingat thescatteredbluesky (highblueirradiancebut lowradiance)
iscompletelysafe,andsoareartificial lightsources,containingway
lessblueirradiancethandaylight.CaseB:LookingatalightsourceWhenevaluatingphotobiologicalrisks(basedonEN62471)themoreseverecaseof
lookingdirectly
intoalightsourceisconsidered.Ineverydaysituations,thisrarelyhappens.ButnotethatthestandardEN62471wasoriginallydeveloped
toprotectworkersparticularly in the lighting industry,as lighting
installersor insimilar fields. Itmayhappen that suchprofessionals
look into light sources several times aworking
dayaccumulatingexposuretoseveralseconds.
Inthissituation,theblueradiance isthecriticalfactorforBLH(the
higher the radiance in the relevant action spectrum, the higher the
likelihood that light
hitsphotopigments(withsufficientenergy)andcausesdamages.Lookingstraightatalightsource(caseB)isalsoingeneralsafefordiffuseandwarmwhitelightsources,likefrostedorwhitediffusinglamps.Yet,cautionisadvisableforcoolwhiteorblue,bright(highintensity),pointlikelightsource,forinstanceanincandescentfilament,electricarcoranLEDdie,evenanLEDdiebehindthelensofadirectionallamp.Suchpointlikesourcesareprojectedontheretinaasaconcentratedlightspotandcandamagethatspotontheretinawhentheintensityishighenoughandthespectrumcontainsbluelightincongruencewiththebluelighthazardactionspectrumcurve.Bothcasesareherediscussedinmoredetail:DataoncaseA:Lookingatanilluminatedscene(irradiance)InAnnex2anoverviewisgivenofthespectraldataofvariouslightsourcesindirectcomparisonwitheachother.Fromthesespectra,thebluehazardirradiancevaluesEBwerecalculatedusingthestandardbluelighthazard(BLH)actioncurve.InFigure2(nextpage)anoverview
isgivenoftheEBvaluesofthedifferent lamptypes. It
isclearthatallsourcesofasimilarcolourtemperature(TcinKelvin)haveasimilarEBvalue.Thisisbecausetheblueportionhasafixedrelationtotheothercolourstomakethecolourwhite.
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Figure3:ComparisonofEBvaluesofthedifferentlamptypesanddaylight.Inorder
tobetter comparewith theeffectofdaylight, itmustbenoted
thatdaylightnormallyprovidesilluminancelevelsthataremuchhigherthan500lux.Figure3showsthecomparisonoftheEBofanumberof
light sourcesat500 lux, comparedwithdaylightat5000 lux,which isan
average value
formoderatelatitudes.Sometypicallamps@500luxcomparedwithoutdoorlighting@5000lux
Figure4:comparisonof irradiancevaluesofsome lamptypesat500
lux(typicalfor indoor)withdaylightat5000
lux(typicalforoutdoorlighting)Theactualoutdoorilluminancevaluecanvaryoverawiderange,upto50.000luxforasunnysummerdayonmoderatelatitudesandeven100.000luxattropicallatitudes.Thisshowsthatthequantityofbluelightofanyindoorgenerallightingcomparedtooutdoorconditionsislowtoverylow.
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DataoncaseB:Lookingatalightsource(radiance)InordertocomparethelightsourcesforcaseB,werefertothestandard(EN62471)asdescribedabove.Inthesestandardsadifferenceismadebetweenlargesourcesandsmallsources.Theimageofasmallsource(4,000,000
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Theresultsareplottedinthenexttwofigures:BlueLightRadianceLBofdiffusesources
Figure5:BlueLightradianceLBforseveralcommonlowluminancelightsources:incandescentlamps,fluorescentlamps,andtheirLEDreplacements.Asareference,alsoaclearincandescentlampisplottedBlueLightRadianceLBofsometypicalpointlikesources
Figure6:BlueLightRadianceLBforseveralhighluminancelightsources:halogenlamps,highintensitydischargelamps,andtheirLEDreplacements.(note:scalediffersfromFigure4)
010002000300040005000600070008000900010000
L B(W
/msr
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ConclusionsonBlueLightRadiancefigures:- Theblue light radiance
LBofdiffuse light sources is relatively low.Assigning the light
source to risk
groups (EN 62471)based on the LB values, reveals thatmostof them
fall intoRG 0, at higher
colortemperature(4000K)somemayjustfallinRG1withmaximumexposuretimesofmorethananhour.Pleasenotethatthisexposuretimereferstoaclosedirectgazeintothesource.Innormalconditionsofuse,wheredistancesaremuchbigger
than themeasuring conditionof200mm to the source, this
iscompletelysafe.Inaddition,inareflexivereactionhumansturnawayfrombrightlightsources,sothatsuchexposuretimesarenotreachable.
-
AllpointlikelightsourcesevaluatedherefallinRG1andareconsideredtobesafebythestandardanddonot
requireadditionalwarningmarkings,butprolongeddirect viewingdirectly
into these
sourcesmustbeavoidedespeciallyatshortdistances.Maximumexposuretimesforthelampsshownhereare200secor
longer,butasalreadymentionedearlier,peoplewillclose theireyesor
lookaway
insuchcases(instinctiveaversionreaction).ThisholdsforthehighluminanceLEDsources
justasmuchasforthehighluminancelightsourcesthatarelongeronthemarket.
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Annex4:Terminologyexplainedquantity symbol unit explanation
irradiance Erad W/m
radiantpowerperareaarrivingonacertainplane
illuminance E lux
irradiance,spectrallyweightedwiththephotopiceyesensitivitycurve
bluehazardirradiance
EB W/m irradiance,spectrallyweightedwiththebluehazardcurve
radiance Lrad W/msr
radiantintensityperareaemittedfromasource
luminance L cd/m
radiance,spectrallyweightedwiththephotopiceyesensitivitycurve
bluehazardradiance LB W/msr
radiance,spectrallyweightedwiththebluehazardcurve
Table3:overviewofunitsofmeasurerelevantinthisarticle
Radiant flux, irradiance,radiant
intensityandradiancerefertoradiationacrossallwavelengths.Luminousflux,illuminance,luminousintensityandluminancegivetheanaloguedimensions,butlimitedtothevisiblespectrum
(spectrally weighted with the visual sensitivity curve of the human
eye to light of differentwavelengths).
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Table4:overviewrisksgroups(takenfromEN62471:2006)
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PrinciplesbehindmeasurementsEN62471:relevancylarge/smallsources:
EN62471:differentmethodsformeasuringsmall/largesources
large source (radiance of source relevant)
small source (irradiance at pupil relevant)
very short exposure (< .25 s)small (point) source min =
0,0017 rd (~0.1)due to intrinsic unsharpness
intermediate exposure (10 s 100 s)small source eff = 0,011 rd
(~0.63)due to rapid eye movement
long exposure (> 10000 s)small source eff = 0,1 rd (~ 5.7)due
to task oriented eye movement
the smallest image that can be formed on the retina of a still
eye is limited to a minimum value, min = 1,7 mrad (at exposure <
0,25 seconds = blink ref lex time)
1 1,7mrad 2 11 mrad @ 200mm
pure source radiance worst case
11 mrad
r=200mm
r@500lx=distance producing 500lx
measurementFOV
at times greater than about 0,25 seconds, rapid eye movements
begin to smear the image of point-like source over a larger angle,
called eff = 11 mrad
a light source subtending an angle less than 11mrad is defined
as a small source
3 11 mrad @ 500lx 4 100 mrad
at > 100 seconds, the image is further spread due to task
depended eye movements,resulting in an maximal angular subtense max
= 100 mrad (taken at exposure times > 10000 s)
Eye movements & angular subtense
Measurement Field of View @ 200mm & @ distance producing 500
lx
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ActinicUVandBlueLightHazardactionspectrumTheactioncurvesforUVandBluehazardaregivingaweightingfactortothespectralradiationintherelevantpartofthespectrum:
Bymultiplyingtheactioncurvevalueswiththe(normalized)spectraldataofUVand/orlightsources,comparativefactorsareobtainedtocomparethesesourcesonthementionedhazards.
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Annex5:OverviewoflampsdiscussedinthispaperThelampdatapresentedinthispaperarerepresentativefortheportfoliooftheELCcompanies
Usedproductnameindocument Technology Shape
WattageColourtemperatureTc[K]
HaloA6028WMVburner2700KE27MV Halogen230V A60bulb 28
2700HaloA6040WLVburner2830KE27MV Halogen12V A60bulb 40
2830HaloMR1645W24DIRC2850KGU5.3LV Halogen12VIRcoated MR16reflector
45 2850HaloCaps28W2800KUVblockG9MV Halogen230VUVreduced capsule 28
2800HaloA6025W2600KE27MV Halogen230V A60bulb 25
2600ESbulbT608272620KE27MV CompactFluo T60bulb 11
2620ESburner8W8272700KE27MV CompactFluo bendedtubes 8
2700IncandA6060W2700KfrostedE27MV Incandescent A60bulb 60
2700LEDA606W2700KE27MV LED A60bulb 6 2700LEDMR167W40D2700KGU10MV
LED MR16reflector 7 2700LEDMR167W40D4200KGU10MV LED MR16reflector 7
4200LEDK6012W2700KE27MV LEDremotephosphor K60bulb 12 2700TLD18W/840
Fluorescent26mm Tube 18 4000T554W/6500K Fluorescent16mm Tube 54
6500T524W/4000K Fluorescent16mm Tube 54 4000T524W/17000K
Fluorescent16mm Tube 24 15000TLED11W/4000K LEDtube26mm Tube 11
4000LEDlamp6500K350lm LED A60bulb 6 6500R7shalogen500W Halogen230V
doubleended 500 2700
Disclaimer:WhileELC/CELMAhavemadeeveryattempttoensuretheaccuracyoftheinformationcontainedherein,ELC/CELMAdonotacceptresponsibilityorliabilityforanyusageofthisdata.