Spectral Radiance Calibrations

1 Page 1 NBSMeasurementServices: A111D2b33fim U.S.DepartmentofCommerce NationalBureauofStandards Open at page → 2 Page 2 CenterforRadiationResearch TheCenterforRadiationResearchisamajorcomponentoftheNationalMeasurementLaboratory intheNational BureauofStandards. TheCenterprovidestheNationwithstandardsandmeasurementservicesforionizing radiat... Open at page → 3 Page 3 RESEARCH INFORMATION CENTER NBSMEASUREMENT SERVICES: Z%. SPECTRALRADIANCECALIBRATIONS'^ JamesH.Walker RobertD.Saunders AlbertT.Hattenburg CenterforRadiationResearch NationalMeasurementLaborator NationalBureauofStandards... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:87-619800 NationalBureauofStandardsSpecialPublication250-1 Natl.Bur.Stand.(U.S.),Spec.Publ.250-1,68pages(Jan.1987) CODEN:XNBSAV Commercialproducts—materialsandinstruments—areidentified... Open at page → 5 Page 5 PREFACE Thecalibration andrelatedmeasurement servicesoftheNationalBureau ofStandardsareintendedtoassistthemakersandusersofprecision measuringinstruments inachievingthehighestpossiblelevelsof accuracy,quality,andproductiv... Open at page → 6 Page 6 ABSTRACT: This report describes themeasurement methods and instrumentation usedintherealizationandtransferoftheNBSscaleof spectral radiance. Theapplicationofthebasicmeasurement equation to both blackbody andtungsten stri... Open at page → 7 Page 7 TABLEOFCONTENTS INTRODUCTION 1 SCALEDERIVATIONANDTRANSFER:AGENERALDESCRIPTION 2 MEASUREMENTAPPARATUS 5 1.GoldPointBlackbody 5 2.VariableTemperatureBlackbody 5 3.LampSources 10 a.VacuumLamps 10 b.Gas-filledLamps 10 4.Spec... Open at page → 8 Page 8 LISTOFTABLESANDFIGURES TABLEI. SpectralRadianceUncertainty (%) 24 FIGURE1.SpectralRadianceApparatus 6 FIGURE2.VariableTemperatureBlackbodySchematic .....7 FIGURE3.CentralSectionofVariableTemperatureBlackbody 9 vi Open at page → 9 Page 9 INTRODUCTION Spectralradiance, denotedL^,isdefinedastheradiantfluxatagiven point, direction, andwavelengthperunitofprojectedarea,solidangle, andwavelengthinterval.Mathematically, where$istheradiantflux,Aisthesurfaceareaa... Open at page → 10 Page 10 variabletemperatureblackbodyisdeterminedbynearlydirectcomparisonto thegoldpointblackbody, thewavelengthrangehasbeenextendedto2400 nm,accuracy estimates havebeenmorerigorously evaluated, andthe instrxjtment hasbeenincorpo... Open at page → 11 Page 11 where R(A^,A) is the spectral responsivity function of the spectroradiometer anddependsontheinstrumentwavelengthsettingA^and onthewavelength Aofthemeasuredradiation, isthespectralradiance ofthesource,cos^-dwisanelementof... Open at page → 12 Page 12 radiance variationsoverwandAgenerallywillnotbeweightedequallyby theinstrumentresponsivity ,andthevariationofspectralradiance over wavelength foranon-blackbody sourcewillnotbeaknownfunction. The errors duetothevariationso... Open at page → 13 Page 13 greater thanintheshortwavelengthregion. Bothcomparisons require a highdegree ofresponselinearityinthespectroradiometer forthevalid determination ofthosesignalratioswhichdepartsignificantly fromunity. MEASUREMENT APPARATU... Open at page → 15 Page 15 PYROMETER CONTROL DETECTOR GRADIENTOBSERVATION WINDOW CARBON-BLACK 0 REMOVABLE WINDOW GRAPHITETUBE FIGURE 2.VariableTemperatureBlackbodySchematic 7 Open at page → 16 Page 16 ofahighdensitygraphitetube,whichisresistivelyheatedinan,argon atmosphere. Electric current issuppliedtpthegraphite tubethrough water-cooledelectricalconnections ateachend Thetubeissurroundedby adouble-walledgraphiteradia... Open at page → 17 Page 17 ZZ] CI FIGURE 5.Centra!SectionofVoriab TemperatureBlackbody 9 Open at page → 18 Page 18 oftheobservationholeisabout0.03sr.Themeasuredpartialreflectivity ofthegraphiteis0.02sr Themeasuredtemperaturegradientoverthe lengthoftheviewingcavityislessthan1K.Experimental investigations ofpossible absorption ofradiat... Open at page → 19 Page 19 radiance temperatureof2620K(at655nm)for2to3hours. Eachlampis examinedforthevariationsinspectralradiancewithtime,withposition within thecentral area,andwithangleofemission. Theamountand orientation ofpolarization arealsod... Open at page → 20 Page 20 Theentrance, intermediate, andexitslitsareadjustablefrom0.01to3.0 mmasaunit,resultinginanearlytriangular-shapedspectralresponsivity function. c.Detectors . Twointerchangeable detectorsareusedtocoverthewave- lengthrangeof... Open at page → 21 Page 21 computer. Allmeasurement signals aremultiplexed intothedigital voltmeterthroughtheinterfacescanner, andtheinstrumentsareremotely programmed andcontrolled through interface modules. Allinstrument settings andsignaloutputs... Open at page → 22 Page 22 Theresponsivltyfactorisobtainedbyspectrallyscanningacontinuous sourcestandard ofspectralradiancewithnarrow (0.1 nun)slits. To determinetheslit-scatteringfunction,anintegratingsphereirradiatedby ahigh-poweredlaserisspectr... Open at page → 23 Page 23 0-56andCS0-52)bothindicateanintegratedscatteredlightcontribution oflessthan0.2%^t225nm.Theslitscatteringfunctioncalculatedfrom thisresultandtheknownsourcedistributions andresponsivityfactor is -9 lessthan10 atwavelengths... Open at page → 24 Page 24 aretypicallyoperatedatnearequalityinthePbSspectralregion. Polarization Thepolarization propertiesofthespectroradiometer andthegas- filledlampsaremeasuredwiththeaidofsheet (linear) polarizers positionedinmotorizedrotating... Open at page → 25 Page 25 indifferent radiometer whenanideallinearpolarizer isrotated inthe sourcebeam. Thecorrectionfactorrequiredtoreducethesignalratioof Eqn. 8toavaluewhichwouldbeobtainedwithapolarization-indifferent radiometer is (1+Bp^)'^ wh... Open at page → 26 Page 26 PROCESSOFREALIZATIONANDTRANSFER Theprocessofrealizationandtransferconsistsofthetemperature determination ofthevariabletemperatureblackbody(VTBB)atareference wavelength, aspectralradiancecomparisonoftheVTBBandthegas-fille... Open at page → 27 Page 27 determinationcanbeperformedatanywavelengthwithinthesignal-to-noise limitations oftheinstrument. Atpresent, theyaredoneatawavelength setting Aqof654.6nm(locationofaconvenientthorium line), where a longhistory ofvacuumlamp... Open at page → 28 Page 28 ordertodiscloseanyapparentshiftsinthescale.Recalibration ofafew lampswhichareretainedatNBSfortherealisationofotherradiometricor photometricscalesprovidefurtherchecksonscalestability. DATAANALYSISANDUNCERTAINTIES Thesigna... Open at page → 29 Page 29 measurements andtheestimatedsystematicerrorinboththemeasured and theprovidedquantities (e.g., temperatureofmeltinggold).Uncertainties obtained fromobserved imprecision andfrompublished values ofthe physicalconstantsareba... Open at page → 30 Page 30 M^,signalratiooftheVTBB-testlampcomparison(0.16to1.27%) M^,signalratiooftheGPBB-VTBBcomparison(0.2%) s^,size-of-sourcecorrectionfortheVTBB-testlampcomparison(0.1%) e„,effectiveemissivityoftheVTBB(0.1%) a d,correctionforl... Open at page → 31 Page 31 vacuum(0.2ma)andgas-filled (1ma)lamps, andinthemeasured spectral responsivity function. Theuncertainties intheratiosduetowavelength setting andcurrentareassessedatanumberofwavelengthsbymeasurement ofthechangeinsignalrati... Open at page → 32 Page 32 TABLEI SPECTRALRADIANCEUNCERTAINTY (%) Source Wavelength (nm) of Error , 225 250 350 655 900 1550 2400 (s) Au . 1,,43 1..29 0..92 0,.49 0,.36 0,.21 0.,13 M(r) r 0..60 0..52 0..37 0..23 0..20 0..11 0.12 (r) 1.,27 0..61 0.... Open at page → 33 Page 33 thecalibrationmethod, thelamppositioning, orientation, targetareaand solidangle, anddependenceuponlampcurrent. Atypical reportwith attachment isshowninAppendixA.Inadditiontotheuncertainties which applyattheconclusionofth... Open at page → 34 Page 34 [7]Quinn.T.J. andLee.R.D. VacuumTungstenScripLampswithImproved Stability asRadiance Temperature Standards: Temperature, Its MeasurementandControlinScienceandIndustry, (InstrumentSociety ofAmerica,Pittsburgh: 1972),Vol.4,... Open at page → 35 Page 35 roKMMBIin (UV.U4i) U.S.DEPARTMENTOFCOMMERCE NATIONALBimCAOOFSTANDAMSS Saithersburg, HD20899 REPORTOFCALIBRATION LAMPSTANDARDOFSPECTRALRADIANCE Requestedby DepartmentofTheNavy CommandingOfficer NavalReMorkFacility NorthIs... Open at page → 36 Page 36 REPORTOFCALIBRATION DepartmentofTheNavy LAMPQ93 Thepolarization measiirementsat655nm,describedinparagraph II of theenclosed document, ehonedthatthedegree of polarization was0.0020. Thedirectionofpolarization ofthe larger... Open at page → 37 Page 37 REPORTOFCALIBRATION Department o-fTheNavy LAMPQ93 TABLEI MeasuredValuesofSpectralRadianceandBlackbodyTemperature •for093at40.370amperes Wavelengthinair SpectralRadiance BlackbodyTemperature (nm) (Wcm-*sr"*) K(IPTS-6B) 22... Open at page → 38 Page 38 REPORTOFCALIBRATION Department o-fTheNavy LAMPQ93 TABLEXI SummaryofEstlm&tsdUnc*rtaint1•inParccntofSpsctralRadianceValuas VAVELENCTH <nm) SOURCEOFUNCERTAINTY 225 250 350 654.6 ?00 1550 2400 1)Blackbodyquality 0.2? 0.24 0... Open at page → 39 Page 39 REPORTOFCALIBRATION DepartmentofTheNavy LAMPQ93 LMIFNO.QfS UHSDl>iUAMM liHFCOlEOrr41.171iXPCRES l.iX1.1KHTUCETilEl * — — I.S • m 9 m •« • t t . t a . 1 1 C . t a . I .1.9 H . a . 0-1.1« « • m -I.S; ^ ; m « • m m m m « —«... Open at page → 40 Page 40 REPORTOFCALIBRATION DepartmentofTheNavy LAMPQ93 UUPMO.QfS UHBDi«(S4.iNH LIMPCURBCXT40.970IHPUES 0.4I0.0HHTilCHUU 4 f — o.s t % I t t I i-0.5* • I . t D -1.1 « -i.s« • * m m m m • m -M — 4 * « * 4 -1.1 -0.1 -1.4 -0.4 -0.2... Open at page → 41 Page 41 REPORTOFCALIBRATION DepartmentofTheNavy LAMPQ93 lAHPNO.on liHEDl> NH liMPCUIEENT40.171iHFCIES l.iXI.IKMTilCCTUU 4 f 4 « l.i « I.S -I.S« -1.1 >LS — — 4— -S -4 -I -2 -1 I 1 2 I 4 S StemsnonsrtciricDscniNCdNCREisiNC e,(CLCv... Open at page → 42 Page 42 REPORTOFCALIBRATION Department o-fTheNavy LAMPQ93 lARPNO.Sf3 llHBOi* NH LiMFCUBIEXT41.371iMFElES l.iI0.1MHTUCniRU « « « 1.1* * I.S 4 % I i •« • • • • I - * C . t D-I.SI 4 •1.14 4 m m m m m m » m -I.S4 4 4 I—— I « -4 4 --... Open at page → 43 Page 43 REPORTOFCALIBRATION Department o-fTheNavy LAMPQ93 lAHPNO.on IDtfiDl>iSl.im LIMPCUEKEKT41.371iXPUCS 1.4It.lMMTUCETUU 4 4 f 4 4 4 4 4 4 1.1 -I.S« •1.1 « •I.S 4 -5 -4 Ij -2 -1 I I t 1 4 '5 SECIECSriOKSPECIFIEDSEniNCdNCIE&SI... Open at page → 44 Page 44 LAMPSTANDARDSOFSPECTRALRADIANCE 1984 I.Introduction andLampDescription Standards o-fspectralradiance areissuedbytheNationalBureau ofStandardstocoverthespectralrange225nmto2400nm. Bas-filled tungsten filamentlamps (Genera... Open at page → 45 Page 45 L((nax)—L(n)in) p= L(max)+L(min) andthedirectionofpolarization ofthelargercomponent,L(max),are determined. L(max)andL(min)arethemaximumandminimumreadingsofa polarization-indifferent radiometer whenanideal linearpolarizer... Open at page → 46 Page 46 B.Conditions Thevalues o-fspectralradiance measured -forthetestlampare associated withaspecifictargetareaonthefilamentsurfaceandMith aspecificsolidangle oftheradiationemitted fromthetargetarea. Thesevalues ofspectralradi... Open at page → 47 Page 47 IV.Mappinq Translationalandrotationalmapping aboutthealignedposition areperformedoneachtestlampat654.6nm. Thevariationinspectral radiance ismeasuredasthe-filament istranslated horizontally and vertically alonglineswhichi... Open at page → 48 Page 48 VI.References CID"TheInternational PracticalTemperatureScale o-f196B", Metrologia, Vol.5,p.35-44(1969). 122 Kostkowski , H.J., D.E, Eriminy, andA.T. Hattenburg, "High-Accuracy Spectral Radiance Calibration o-fTungsten-St... Open at page → 49 Page 49 TypicalSp TABLE I SAMPLEOFDATAANDUNCERTAINTIES RadianceValuesandEstimatedUncertainties (Percent) SpectralRa^i (Wcm'sr~ ) Wavelength (nm) 654.6 800 1550 BlackbodyTempera t (KIPTS-68) SOURCEOFUNCERTAINTY 1)Blackbodyquality... Open at page → 51 Page 51 on J PreparedbythestaffsoftheOpticalRadiationarnjtheRadiometricPhysicsSections ofNBStoreportonitemsofinterestinopticalradiationmeasurements Iryjuiriesmay bedirectedtoRobenLBooker,B30eMetrologyBIdg.NBS.Washinoion.DC20234... Open at page → 52 Page 52 ThePASCALfacilityincorporatesalloftheusualelementsrequiredforprecision temperature-based radiometry. Theyareconfiguredinalineararrangement,dominatedbya heavytrussbridgestructure7.3alongsupportingapairofgroundl^s-inchdiam... Open at page → 53 Page 53 CablesfromallequipmenthousedIntheinstrumentcarriagearebundledandpassed throughthebottomofthecarriage,wheretheyrldpinasmoothtroughbetweentherails asthecarriagepassesbackandforth. Allcontrolandmeasurementcablesfromthecar-... Open at page → 54 Page 54 EvaluationandEstimation",whichisnowavailable. Inquiriesconcerningthistechnique anditspossibleuseinerrorevaluationandestimationshouldbedirectedto: Dr.JackJ.Hsla RoomA317,MetrologyBuilding NationalBureauofStandards Washing... Open at page → 55 Page 55 AppendixC.MeasurementofInstrumentandSourcePolarization Themeasurement ofsourcepolarizationandthedetermination ofits effectonthemeasurementofspectralradianceiscarriedoutwithasheet polarizer mountedinamotorizedrotatingmoun... Open at page → 56 Page 56 thereference directionforpolarization tobeinwhateverdirection the radiometerpolarizance lies,thusforcingthe45°componenttovanish. The referencedirectionwasdeterminedtobehorizontalbysimplyobservingthe effect ofahand-heldpo... Open at page → 57 Page 57 Thevariousmeasurements thenleadtoequations ofthefollowing forms . Nopolarizer: V=R •L=RL (4a) oo Polarizer#1:V(^)=R •P •L=RL(s+BdC) (5a) oo Bothpolarizers: V(<f>,4>')-R •P •P'-L (6a) =RL(ss'+Bs'dC+dd'CC'+Bd'fC'+dd'SS'+Bd... Open at page → 58 Page 58 (8a) where, asalways, wehaveneglectedcircularpolarization, and axe givenby p^ =p-cos27andP2 =p-sin27, where 7isthedirection of polarization measuredfromthereferencedirectionoftheradiometerand p isthedegreeofpolarization,... Open at page → 59 Page 59 ofresponseandonlylinearpolarization. Ifweapplythisequationboth tothemeasurement ofanunknownsourceandtothemeasurement ofa spectralradiancestandardusedtocalibratetheradiometerweobtain: =L^[V/V^][(l+Bp^)/(l+Bp^)] (12a) s s... Open at page → 61 Page 61 DETAILEDPROCEDURESFORROUTINESPECTRALRADIANCECALIBRATIONS A.LampPreparation 1.VisualInspection Thelampthatisissuedasaspectralradiancestandard isaspeciallymadelampfromGeneralElectricdesignated type30A/T24/13. Uponunpacking... Open at page → 62 Page 62 CmMakeasmalldotwithamarkingpenontherearofthe lampenvelopeatthepointwherethelaserbeam strikes. *****»******»»»»*»*»»»*«****»*«*««#»*» » CAUTION * «***«»«**»«*»******««*»»**»*»*****»»»**»* «Greatcareshouldbetakentoavoid »... Open at page → 63 Page 63 ffl.A-fter3minutes,rinseof-ftheacidwithcoldwater, cleano-fftheetchingwaxwithxylene,andwashthe entirelampenvelopeandnozzlewithSparkleenand hotwater. ThendrythoroughlywithKimwipestore- moveanywaterspots. » CAUTION * -it***... Open at page → 64 Page 64 Turnonthelampandletitstabilize -For20minutes. ****************************************** * CAUTION * ****************************************** »Mhenturningalamponoroffthe *currentshouldbeslowlyincreasedor* *decreased. A... Open at page → 65 Page 65 6)Repeatsteps3)to5)untilthelaserbeamis centeredontheobjectivelensMhiletheimage ofthefilamentnotchiscenteredinthefield ofview. i.Positiona"blockingfinger"onthe45degreeplane mirroronthespectroradiometer.Rotatethearrow 2deg... Open at page → 66 Page 66 position,andperformsthecalculationstodeterminethe ratiosofthetestlampreadingstothereferencelamp readings. ) a.Testlempsaresetatacurrenttogivethemaradiance temperatureofabout2470Kat654.6nm.(Thiscurrent isusuallybetween38a... Open at page → 67 Page 67 polarizersareusedtodoanautomatedcharacterization at654.6nm.Thecomputerprogramusedtoperformthese measurements is"TWOPOL.JW". b.Useonepolarizertocharacterizethepolarization of thetestlamp.Thecomputerprogramusedtoperform th... Open at page → 68 Page 68 g.Throw208Vbreakeronthewallbehindthespectrorad- iometertoONposition(Up), h .DepressyellowbuttononC.A.T.controlunituntil meterreadsabout30andcheckthatthetopofthe blackbodyhousingiscoolandthatthecoolingwater isflowing. (If... Open at page → 69 Page 69 a.Thespectroradiometer detectorsignalisconvertedto ananalogvoltagewhichisdisplayedonastrip-chart recorder. b.Thefullscalesignalisbiasedtoabout5%o-fits originalvalueandthenisamplifiedbya-factor o-f10 sothatonedivisiononth... Open at page → 70 Page 70 4)Thespectroradiometer ispositionedinfrontofa shutterpositionandtheDVMreadingisrecorded. 5)ForeachsourcethemeanofthethreeDVMreadings iscalculatedandtheshutterreadingissubtracted fromit. 6)Theresultingsignaliscorrectedfor... Open at page → 71 Page 71 2)Returnto654.6nm,positionthephotomultiplier tubeanddeterminetheblackbodytemperatureby comparingitsoutputtotheoutput o-fthestandard lamp. 3)Setatthetestwavelength,positionthePbSdetec- torandcomparetheoutput-fromthetestla... Open at page → 72 Page 72 n-Readover"EndofDayCheckList"(locatedonK-6Pot) andperformth<enecessaryoperations. 1)Turnofftheblackbody. a)Throwmainbreakeronbackwalltooff. b)Turnoffcoolingwater. c)CloseblackbodywindowandturnoffArgonflow attheblackbodya... Open at page → 73 Page 73 f . g Run"FLANAL-1"tocalculatethefollowingstatistics 1)Numberofmeasurements ateachwavelength 2)Rangeforrepeatmeasurements 3)Meanvalue 4)Standarddeviationofthemean andtostorethewavelength,meanspectralradiance, andmeanblac... Open at page → 74 Page 74 NBS-n4AIREV.2-8C) U.S.DEPT.OFCOMM. BIBLIOGRAPHICDATA SHEET(Seeinstructions) 1.PUBLICATIONOR REPORTNO. NBS/SP-250/1 2.PerformingOrgan.ReportNo 3,PublicationDate January1987 4.TITLEANDSUBTITLE NBSMEASUREMENTSERVICES: spect... Open at page → 75 Page 75 PUBLICATIONS INTHESP250SERIESFROMTHECENTERFORRADIATIONRESEARCH SP250-1 NBSMeasurement Services: SP250-12 SpectralRadianceCalibrations J.H.Walker,R.D.Saunders, andA.T.Hattenburg SP250-2 NBSMeasurementServices: SP250-13 Fa... Open at page → 76 Page 76 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 Open at page →