Spectral Reflectance

1 Page 1 NISTMeasurementServices: NATLINST.OFSTAND&TECHR.I.C. AlllDSM7blb7 M!ST REFERENCE FUBUCATIONSlj SpectralReflectance NIST Special Publication 250-48 P.YvonneBarnes EdwardA.Early AlbertC.Parr OpticalPropertiesofMaterials: B... Open at page → 2 Page 2 rhe NationalInstituteofStandardsandTechnologywasestablishedin1988byCongressto"assistindustryin thedevelopmentoftechnology ...neededtoimproveproductquality,tomodernizemanufacturingprocesses, toensureproductreliability ...... Open at page → 3 Page 3 NISTMEASUREMENTSERVICES: SpectralReflectance p.YvonneBarnes EdwardA.Early AlbertC.Parr OpticalTechnologyDivision PhysicsLaboratory NationalInstituteofStandardsandTechnology Gaithersburg,MD20899-0001 March1998 U.S.DEPARTM... Open at page → 4 Page 4 NationalInstituteofStandardsandTechnologySpecialPublication250-48 Natl.Inst.Stand.Techno!.Spec.Publ.250-48,153pages(Mar.1998) CODEN:NSPUE2 U.S.GOVERNMENTPRINTINGOFFICE WASHINGTON: 1998 ForsalebytheSuperintendent ofDocume... Open at page → 5 Page 5 PREFACE ThecalibrationandrelatedmeasurementservicesoftheNationalInstituteofStandards andTechnology areintendedtoassistthemakersandusersofprecisionmeasuring instruments inachieving thehighestpossible levelsofaccuracy, qua... Open at page → 6 Page 6 ABSTRACT Thisdocumentdescribestheinstrumentation, standards,andtechniquesusedat theNationalInstituteofStandardsandTechnologytomeasurespectralreflectanceover theultraviolet, visible,andnearinfraredwavelengthranges.Theorga... Open at page → 7 Page 7 TABLEOFCONTENTS Abstract iv 1.Introduction 1 2.Theory 4 2.1BasicDefinitionsandEquations 4 2.2MeasurementEquations 8 2.2.1BidirectionalReflectanceDistributionFunction 8 2.2.2Directional -HemisphericalReflectance 10 3.Refe... Open at page → 8 Page 8 AppendixA:SampleReportofTestforBidirectionalReflectanceDistributionFunction AppendixB:SampleReportofCalibrationforSpectralReflectance AppendixC:SampleReportofTestfor0°/45°ReflectanceFactor AppendixD:SampleReportofTestfor... Open at page → 9 Page 9 LISTOFFIGURES Figure2.1Geometryofincidentandreflectedelementaryradiantbeams 5 Figure3.1SchematicsoftheSTARRinstrument 13 Figure3.2ComponentsandopticalpathoftheSTARRsource 14 Figure3.3GoniometersystemoftheSTARRinstrument... Open at page → 10 Page 10 LISTOFTABLES Table1.1AvailableNISTStandardReferenceMaterialsandCalibration Servicesforspectralreflectanceandwavelengthstandards 2 Table3.1WavelengthrangesofcomponentsusedintheSTARRsource 15 Table3.2Wavelengthrangesofdete... Open at page → 11 Page 11 1.Introduction Spectralreflectancemeasurements provideimportantinformationaboutthe opticalpropertiesofmanymaterials.NISTstrivestoprovidethebestpossiblestandards fordiffuseandspecularreflectanceaswellasspecialservicesanda... Open at page → 12 Page 12 Table1.1AvailableNISTStandardReferenceMaterials*andCalibrationServicesfor spectralreflectanceandwavelengthstandards SRM Number Description 2003 2011 2023 2026 2015 2016 2044 1920a 38060S Specularreflectancestandards 1stS... Open at page → 13 Page 13 lawsofopticalreflection.Whilethismeasurement isclassifiedseparatelyfromBRDF,it isactuallyanotherspecificinstance[4,5,6]. 3.Spectraldirectional -hemispherical reflectancefactor,whichistheratioofthetotal reflectedradiantfl... Open at page → 14 Page 14 2.Theory 2.1BasicDefinitionsandEquations Thissection isconcernedwithstatingthebasicdefinitionsandderivingthe generalequationswhichspecifyreflectanceintermsofthebeamgeometryofboththe incidentandreflectedradiantflux. Inthe... Open at page → 15 Page 15 Figure2.1.Geometryofincidentandreflectedelementaryradiantbeams. Aconvenientflatsurfaceischosenasareferenceplanetorepresentthereflecting surface.Thenthepolarangles^areanglesfromthereference-planenormal,andazimuth angles^a... Open at page → 16 Page 16 , (2.5) Assumefurtherthatthescatteringpropertiesofthesampleareuniformand isotropicacrossthereferenceplane,sothatthescatteringfunctionSdoesnotdependon thelocationofthepointofobservation{x„y^,butstilldependsonthedistancerb... Open at page → 17 Page 17 (2.11) Now,thereflectedradianceintothesolidangleo)^is LiO„ <!>;)=jdl,(^., (I>^0. (I>r\Ed (2.12) which,usingeq(2,9),gives m,(p:) = ld£i(^„ (!>:)-m, <i>., e„ </>:) . (2.13) Expressingtheincidentirradianceintermsoftheincide... Open at page → 18 Page 18 d^r/d^Hd= — f • (218) Assuming,asbefore,thatZjisisotropicwithinthefullsolidangleofincidence<y„ can bebroughtoutoftheintegrals,leaving i?(^i,^z>i;^„^zJ,)= (7://25A)- jj/r(^„^z>i;^„^zJ,)-d/2i-d/2, . (2.19) 2.2MeasurementEq... Open at page → 19 Page 19 S;iA;a)-UX-a)dOiX;a) , (2.23) where cr)istheresponsivityofthedetectortotheincidentfluxd0j(A;d).Notethe explicitdependenceofthesevaluesonthewavelengthandpolarizationparameters.The incidentfluxintermsofirradiancedE^{A,\d)i... Open at page → 20 Page 20 Theregularreflectance p{0,, (f>;,6„(/);,A;o),forwhichthespecialconditions 65.=-6^and ^4 = -<^,apply,iseasilyobtainedfromeq(2.30)bymultiplyingbythesolidanglei?,, resultingin . (2.3,) 2.2.2Directional -Hemispherical Reflec... Open at page → 21 Page 21 Takingratiosforthesignalsmeasuredwiththesampleswithknownandunknown reflectances,eqs(2.33)to(2.37)become no SSRR O y\xA^ws_^xx^ws -"-wx -'*-ss i,wx 1^ /'wx/^ss "^wx"^ss^xx^^s ^i,xx l.WS 1,SS (2.37) Tosolveforthereflectanc... Open at page → 22 Page 22 3.ReferenceInstrument-STARR 3.1Description 3.1.1BasicInstrumentTheSpectralTri-functionAutomatedReferenceReflectometer (STARR) isdesigned toperformabsolutespectralmeasurements ofbidirectional, specular,anddirectional -hem... Open at page → 23 Page 23 Figure3.1.SchematicsoftheSTARRinstrumentshowingtopviews ofthemajorcomponents (a)andthegeometrical arrangements formeasuringtheincidentdirectionalflux (b),thereflecteddirectionalflux(c),andthereflected hemispherical flux(... Open at page → 24 Page 24 3.1.2SourceSystemThesourcesystemconsistsofanilluminator,amonochromator, a limitingaperture,acollimator,achopper,andapolarizer.Thecomponentsofthesource, aswellastheopticalpath,areshowninfigure3.2. Monochromator FilterWhee... Open at page → 25 Page 25 three600lines/mmruledgratingsblazedat200nm,400nm,and1000nm,anda 150lines/mmruledgratingblazedat4000nm.Thislastgratingisnotusedonaregular basis,butisreservedforfutureupgradesintothemid-infrared spectralregion.The monochro... Open at page → 26 Page 26 Thepolarizerisautomatedandcomputercontrolled.Thebeampassesthroughafinal bafflebeforeexitingthesourcesystem. 3.1.3Goniometer Thegoniometerusedtopositionthesampleforbidirectional reflectancemeasurements hasfourindependent... Open at page → 27 Page 27 achievedthroughhighprecisionmachiningofaheavy-dutystainlesssteelchassis.The resolutionandrepeatabilityoftherotationstagesare0.001°and0.01°,respectively. All fourstagesarefittedwithservomotorscontrolledbyafour-axismotionc... Open at page → 28 Page 28 sevenandone-halfdigitdigitalvoltmeterfortheSiandGedetectors. FortheInAs detector,theincidentbeamischoppedandtheoutputvoltageismeasuredwithalock-in amplifier.Theoutputsignalofthelock-inismeasuredwiththevoltmeter. 3.1.4Int... Open at page → 29 Page 29 Detector Figure3.5.Cross-sectionoftheintegratingsphereusedfor6°- hemisphericalreflectancemeasurementswiththeSTARR instrument. Table3.2Wavelengthrangesofdetectorsusedinthe STARRinstrument Detector Wavelengthrange[nm] Bidi... Open at page → 30 Page 30 3.2Calibration 3.2.1SourceSystemWavelengthcalibrationconsistedofcomparingthewavelength indicatedbythemonochromator tothetruewavelength. Thiswasaccomplishedby measuringtheemissionlinesofspectrallinesources[13,14]andtheabs... Open at page → 31 Page 31 600nmto0.5x 10'^ at400nm.Asimilarlevelofstrayradiationwasfoundat wavelengthslongerthanthatofthelaserandusingmethodswithfilters[17,18]. ThestabilityoftheXesourcewasmeasuredwiththebeamemergingfromthe sourceincidentontheSid... Open at page → 32 Page 32 3.2.3IntegratingSpheresCalibrationoftheintegratingspheressimplyrequiredthat theincidentbeambeperpendicular totheentranceportofthesphere,passthroughthe centerofthisportuponrotationofthesphere,andstrikethecenterofthesample... Open at page → 33 Page 33 samplesofthesametypearemeasuredinsequence. Therefore,theinstrumentsetupis performedoncepriortothebatchrun,andthenthesamplesaremeasured.Thespectral rangeofthemeasurementdeterminesthelampanddetectorcombination. Insomecases... Open at page → 34 Page 34 Figure3.6.SamplemountoftheSTARRgoniometer. thattheincidentbeamfallsonthecentersofboththealignmentjigandtheholeforthe detector.Theabsolutepositionoftherotationstageisrecordedtosetthepositionofzero rotationforthedetector.T... Open at page → 35 Page 35 overthetimeperiodofthemeasurement,theBRDFforafixedlinearpolarizationofthe incidentbeamisgivenby (3.1) where^istheincidentangle, 0^isthereflectedangle,Aisthewavelength,aisthe polarization, isthesignalfromtheincidentradian... Open at page → 36 Page 36 Thesignals,togetherwiththedistance,area,andangle,areusedineq(3.3)to calculateBRDF,fromwhichthereflectanceandreflectancefactorcanalsobecalculated byusingeqs(3.5)or(3.6),respectively. Equation(3.3)assumesthatthesourceisa p... Open at page → 37 Page 37 Figure3.7.Specularreflectanceasafunctionofwavelengthforthe SRMslistedinthelegend.Therelativeexpanded uncertainties ofthe reflectances, approximately 0.1percent,arewithinthesizesofthesymbols. 1.050 1.025 1.000 0.975 0.950... Open at page → 38 Page 38 0.40 0.28 0.26 ^ ' ' ' ' I I ' ' -80 -60 -40 -20 0 20 40 60 80 ReflectedAngle[°] Figure3.9.BRDFasafunctionofreflectedangleat632.8nmfora PTFEplaqueattheindicatedincidentangles.The relativeexpandeduncertaintiesoftheBRDF,le... Open at page → 39 Page 39 where isthereflectancefactorofthestandard, 5*^^and.S"^arethesignalsobtainedwith thesampleattheportandtheincidentbeamstrikingthesampleandwall,respectively, and andS^^arethesignalsobtainedwiththestandardatthesampleportandt... Open at page → 40 Page 40 1.05 1.00 0.95 00.90 o ^0.85 o 10.80 o §0.75 . I 0.70 ' ' 0.65 0.60 350400450500550600650700750800 Wavelength[nm] Figure3.10. 6°-hemispherical reflectance factorasafunctionof wavelength forthematerialslistedinthelegend.T... Open at page → 41 Page 41 Theestimatedstandarduncertaintyinthemeasurandyisthecombinedstandard uncertainty u^(y).Tofirstorder,andassumingthatthestandarduncertaintiesofeach inputquantityareuncorrelated, u^(y)isgivenbythelawofpropagationofuncertaint... Open at page → 42 Page 42 SiiA)=jR(A')-0^{X,A')-dA' and (3.13) S,(A)=\R(A')-fM;0,;A')-n,-0^(A,X'ydA' , (3.14) wheretheintegralsareoverallwavelengths A'. Thecomponentsofuncertainty associatedwithbidirectional reflectance are conveniently dividedam... Open at page → 43 Page 43 Table3.5Relativeexpandeduncertainties{k= 2)forthebidirectionalreflectanceofa whitePTFEplaque Componentof Relativeexpanded uncertainty Type uncertainty[%] Wavelength[nm] 200 400 800 1200 1600 Sourcestability A 0.20 0.20 0... Open at page → 44 Page 44 Table3.7Relativeexpandeduncertainties{k= 2)forthebidirectionalreflectanceof agreentile Componentof Relativeexpanded uncertainty Type uncertainty[%] Wavelength[nm] 400 500 600 700 OUUIL-CoLdUlllLj' A 090 0.02 0.02 004 TVC... Open at page → 45 Page 45 eq(3.14),therelativesensitivitycoefficientofthereflectedsignalduetotheincidentflux is1/(Pj.TheexpandedrelativestandarduncertaintyinBRDFduetoinstabilityofthe sourceisgivenintables3.5and3.7atselectedwavelengths. Themaximum... Open at page → 46 Page 46 jR(A')-0;{X,Z')drand (3.18) A-AA Si,s\W= j/?(A')-<^i(A,A')-dA'+ jRiZ')-0i(A,A')-dA' . (3.19) 0 A+AA A+AA '^r,bwW= Ji?(A')-/r(^')-A-<^i(^^')-dA' and (3.20) A-AA A-AA 00 5,^^,(^)= Ji?(A')-/,(;i')-A-^ia'^')-dA'+ Ji?(;i')-/r... Open at page → 47 Page 47 0.001°and0.01°,respectively.Assumingarectangularprobabilitydistributionforthese errors,thecombinedstandarduncertaintyintheangleofincidence is0.08°.Sincethe uncertainty inBRDFduetoanuncertainty inincidenceangle 9^dependsu... Open at page → 48 Page 48 ThesecondequationrelatesanysignalS{A)fromthereflectedfluxintheintegrating spheretotheincidentfluxC^A),andisgivenby SiA)=^iA)-R{Ji)-0(X) , (3.25) where istheresponsivityoftheintegratingsphereanddetectorandR(A)isthe reflec... Open at page → 49 Page 49 Table3.10 Relativeexpandeduncertainties {k= 2)forthe6°-hemispherical reflectanceofaPTFEplaque Componentof Relativeexpanded uncertainty Type uncertainty[%] Wavelength[nm] 200 400 800 1200 1600 0.40 0.40 0.08 0.08 0.08 0.0... Open at page → 50 Page 50 4.TransferInstrument-Spectrophotometers 4.1Description Twocommercial spectrophotometers, aVarian-Cary5EandaPerkin-Elmer Lambda19,^areusedastransferinstrumentsandarecalibratedwithprimaryreference standardsfromtheSTARRinst... Open at page → 51 Page 51 oppositesideofthesphere.Thesamplebeamisnearlycollimatedandentersthesphere througharectangularportapproximately30mmhighby20mmwide.Thesampleport isoppositethisentranceportandis22.5mmindiameter.Animageoftheexitslitofthe mon... Open at page → 52 Page 52 (a)Specularexcludedmode (b)Specularincludedmode Figure4.1.TopviewoftheIntegratingSphereAssemblyofthe Perkin-ElmerLambda 19transferspectrophotometer configuredforreflectanceoperatinginthespecular excluded(a)andspecularinc... Open at page → 53 Page 53 Table4.1Wavelengthsofemissionlinesandabsorptionbandsusedtocalibratethe wavelengthscaleoftheGary5Etransferspectrophotometer Source Wavelength[nm] Emissionlines Hg 253.65,334.15,435.83,546.07,1014.0, 1529.5 Dj 486.0,656.10... Open at page → 54 Page 54 Thepresenceofstraylightinthetransferspectrophotometers samplebeamwas checkedusinganumberofsolutionsandglassfihersthathavesharpcut-offabsorption featuresindifferentspectralregions.Thetechniquesformeasuringstrayradiationar... Open at page → 55 Page 55 1.0 0.5 0.4 V 0.3 ' ' I ' ' I— I ' ' I ' I ' I ' ' I ' I ' ' I ' ' 60075090010501200135015001650180019502100 Wavlength[nm] Figure4.2.Reflectanceasafunctionofwavelengthfortherare-earth mixturewavelengthstandardSRM1920a. T... Open at page → 56 Page 56 features,orothersthatcouldaffectthemeasurements, areobservedonthesample,anote ismadeinthecalibrationreport. Table4.3Standarduncertaintiesofspectralreflectancevalues forthetransferspectrophotometers inthevisible wavelengt... Open at page → 57 Page 57 References [I]JamesE.ProctorandP.YvonneBarnes,"NISTHighAccuracyReference Reflectometer-Spectrophotometer," J.Res.Natl.Inst.Stand.Technol.101,619 (1996). [2]StandardReferencesMaterialsCatalog 1995- 1996,NISTSpecialPublica... Open at page → 58 Page 58 [21]K.L.Eckerle,V.R.Weidner, J.J.Hsia,andK.Kafadar,"MeasurementAssurance ProgramTransmittance Standards forSpectrophotometric Linearity Testing: PreparationandCalibration," J.Res.Natl.Bur.Stand.(U.S.)88,25(1983). [22]C.L... Open at page → 59 Page 59 AppendixA REPORTOFTEST 38060SBidirectionalReflectanceDistributionFunction(BRDF) of OneWhiteTarget Submittedby: AnyCompany Attn:YuraCustomer AnyStreet AnyTown,AnyStateZipCode-0000 (SeeyourContractNo.000000-000DatedMonthDa... Open at page → 60 Page 60 REPORTOFTEST AnyCompany 38060SBRDF Sincetheilluminatedareaofthespecimenisnotapointsource,theaverageprojectedsolidangle oftheilluminatedareawasdeterminedforcomputingtheBRDFvalues.Thecircularreceiver aperturesubtendedahalf... Open at page → 61 Page 61 REPORTOFTEST AnyCompany 38060SBRDF TABLE1 WhiteTargetA ANGLEOFINCIDENCE: 0° WAVELENGTH:800nm ANGLEOFVIEWING [degrees] BRDF 60 40 0.300 20 0.300 0 0.310 -20 0.320 -40 0.340 -60 0.400 TestDate:MonthDay,Year NISTTestNo.:Div... Open at page → 62 Page 62 REPORTOFTEST AnyCompany 38060SBRDF TABLE2 WhiteTargetA ANGLEOFINCIDENCE:45' ANGLEOFVIEWING: 0" Wavelength [nm] BRDF 400 0.323 500 0.323 600 0.323 700 0.323 800 0.323 900 0.323 1000 0.323 TestDate:MonthDay,Year NISTTestNo... Open at page → 63 Page 63 AppendixB REPORTOFCALIBRATION 38060SSpectralReflectance ofa FirstSurfaceAluminumMirrorSRM2003 SeriesD Submittedby: AnyCompany Attn:YuraCustomer AnyStreet AnyTown,AnyStateZipCode-0000 (PurchaseOrderNo.00-0000-00datedMonth... Open at page → 64 Page 64 REPORTOFCALIBRATION AnyCompany 38060SSpectralReflectanceofaFirstSurfaceAluminumMirror SRM2003wascalibratedoverthewavelengthrangeof250nmto2500nmasfollows:50nm intervalsovertherangeof250nmto1000nm,100nmintervalsovertherang... Open at page → 65 Page 65 REPORTOFCALIBRATION AnyCompany 38060SSpectralReflectanceofaFirstSurfaceAluminumMirror Preparedby: Approvedby: P.YvonneBarnes OpticalTechnologyDivision PhysicsLaboratory (301)975-2345 RobertD.Saunders FortheDirector, Nati... Open at page → 66 Page 66 REPORTOFCALIBRATION AnyCompany 38060SSpectralReflectanceofaFirstSurfaceAluminumMirror Table1 FirstSurfaceAluminumMirror,SRM2003,SeriesD Wavelength[nm] Reflectance 250 0.883 300 0.901 350 0.904 400 0.903 450 0.899 500 0.8... Open at page → 67 Page 67 AppendixC REPORTOFTEST 38060S45°/0°ReflectanceFactor ofa WhiteDiffiiserTablet Submittedby: AnyCompany Attn:YuraCustomer AnyStreet AnyTown,AnyStateZipCode-0000 (ReferencePurchaseOrderNumber:00-0000-00datedMonthDay,Year) 1... Open at page → 68 Page 68 REPORTOFTEST AnyCompany 38060S45°/0°ReflectanceFactor Sincetheilluminatedareaofthespecimenisnotapointsource,theaverageprojectedsolidangle oftheilluminatedareawasdeterminedforcomputingthereflectancefactors.Thecircularrece... Open at page → 69 Page 69 REPORTOFTEST AnyCompany 38060S45°/0°ReflectanceFactor ReflectancefactorRasafunctionofwavelength /I for45°incidentangleand0°viewingangle ofthepressedPTFEplaque [nm]R(45°/0°) [nm]i?(45°/0°) [nm] i?(4570°) 380 1All 1.01 1 5... Open at page → 71 Page 71 AppendixD REPORTOFTEST 38060S6°/Hemispherical ReflectanceFactor of OneWhiteDiffuserPlateand OneAluminumDiffuserPlate Submittedby: AnyCompany Attn:YuraCustomer AnyStreet AnyTown,AnyStateZipCode-0000 (ReferencePurchaseOrde... Open at page → 72 Page 72 REPORTOFTEST AnyCompany 38060S6°/Hemispherical ReflectanceFactor 3.ResultsofTest TheaverageofthePTFEmeasurementsandtheabsolutereflectancefactor(relativetothatofa perfectdiffuser)ofthePTFEwasusedtoadjustthemeasuredreflect... Open at page → 73 Page 73 REPORTOFTEST AnyCompany 38060S67Hemispherical ReflectanceFactor Table1 67Hemispherical ReflectanceFactor Specimen:WHITEDIFFUSERPLATE Wavelength[nm] ReflectanceFactor 230 0.885 252 0.921 273.5 0.942 283 0.947 292.2 0.958... Open at page → 74 Page 74 REPORTOFTEST AnyCompany 38060S6°/Hemispherical ReflectanceFactor Table2 6°/Hemispherical ReflectanceFactor Specimen:ALUMINUMDIFFUSER Wavelength[nm] ReflectanceFactor 230 252 273.5 283 292.2 301.9 312.5 331.2 339.8 350 37... Open at page → 75 Page 75 AppendixE Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology [J.Res.Natl.Inst.Stand.Technol.101,619(1996)] NISTHighAccuracyReference Reflectometer-Spectrophotometer V... Open at page → 76 Page 76 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology Thistableislocatedinthecenterofalight-tightroom withblackwallsandceiling.Specialairfiltershavebeen incorporatedinto... Open at page → 77 Page 77 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology 3.SourceSystem Thelamphousing (Oriel7340Monochromator niuminator')containstwosources.A150Wultraviolet enhancedxenon... Open at page → 78 Page 78 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology passingthroughaperture"B"wasmeasuredanddesig- natedVb-Finally,thesignalduetolightpassingthrough bothaperturessimult... Open at page → 79 Page 79 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology Table2liststhecomponentsofrelativestandard uncertainty,therelativecombinedstandarduncertain- ties,andtheexpandedunc... Open at page → 80 Page 80 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology repeatabilityof0.01°.Thesearesmallcomparedtothe measuredreceiverangularrelativestandarduncertainty of0.09%,andinfac... Open at page → 81 Page 81 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology slightdifferences intheUVdatacouldeasilybedue toagingofthesampleordifferences incleaning techniques. Figure5showsth... Open at page → 82 Page 82 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology measurement historyanddemonstrated longterm stability.Theagreementbetweenthetwoinstruments is excellentexceptforthe... Open at page → 83 Page 83 Volume101,Number5,September-October 1996 JournalofResearchoftheNationalInstituteofStandardsandTechnology spectralregion.Second,whiletheindiumarsenide phododiodehasexcellentresponsivityandlinearity, itis onlyavailableinsi... Open at page → 85 Page 85 AppendixF JOURNALOFRESEARCHoftheNationalBureauofStandards Volume82,No. 1 ,July-August 1977 EstablishingaScaleofDirectional-Hemispherical Reflectance FactorI:TheVandenAkkerMethod WilliamH.Venable,Jr.,JackJ.Hsia,andVictorR... Open at page → 86 Page 86 hasbeenusedinthepastatNBS,improvinguponthe techniquesandprovidingthenecessarycorrections tomake themeasurementspreciseandaccuratetowithin±0.0015to thebestofourknowledge.Thisstephasbeencompletedand isreportedinthispaper.T... Open at page → 87 Page 87 Table II Datafromaninlercomparison betweenNRCandPTBofreflectance measurements onapressedBaSO^tablet[7](SpectralHemispherical- directional(0°)reflectancefactor). Reflectance Wavelength NRC PTB Difference (PTB-NRC) 370 0.9... Open at page → 88 Page 88 REFLECTOMETER SPHERE ^ REFLECTOMETER SAMPLEPORT RADIUS HEMISPHERE ASSEMBLYFLANGi REMOVEABLE TARGET SECTION POLISHED BEVELLEDPORT EDGE STAINLESSSTEEL PORTPLATE / (.6mmTHICK1^ ALUMINUM SPHERESHELL Figure I.Sphereusedformea... Open at page → 89 Page 89 Anadditionalmodificationmustbemadeintheoriginal VandenAkkerequationtotakeintoaccounttheeffecton oftheretroreflectance ofthespherewall.Thismodification, whichresultsinonlyasmalladjustmentppbutwhichgreatly complicates thef... Open at page → 90 Page 90 D.Determining theDirectional-Hemispherical Reflec- tanceFactorofStandardsandOtherSamples ThedihreflectancefactorF[Y ,X)asdetermined inthe precedingfourstepsisthedIhreflectancefactorofthesphere wallcoating.Thefinalstepist... Open at page → 91 Page 91 Rfromonedeterminationofreflectancetothenextandfrom theinabilitytomeasuretheaverage/?exactly.Thisgivesrise toarandomerror 8f whichisgivenby: 8f = 2(1- {rlR)^y 8R. (17) Asystematicerrorarisesfromanyerrorinmeasuringrand fro... Open at page → 92 Page 92 theVandenAkkerreflectanceofthespherewallinits entirety.Therandomerrorinpj,isobtainedfromeq(6)as Sp;=[((l-QtlQm-fffT +{{fiQm-f)fm ThesystematicerrorinPy isgivensimilarlyby: Ap;=[((i-QjQm-j)'f^f (24) (25) where gisonlythat... Open at page → 93 Page 93 therandomerrorinPoasgivenbyeq(26)is Sinceusingthedistancefromthecoatingsurfacetothe aluminumsubstrateasitsthickness isonlyaroughapproxi- mationintheregionsoftheportandofthetargetboundary,a systematicerrorwillbeintroduced... Open at page → 94 Page 94 TableVI ThirdDeterminationBaS04[16] Wavelength (nm) VandenAkker Reflectancepp p(6°,X) F(6°,) 400 0.9744 0.9695 0.9688 425 .9771 .9732 .9725 450 .9789 .9757 .9750 475 .9802 .9775 .9768 500 .9813 .9791 .9784 525 .9823 .980... Open at page → 95 Page 95 TableVIII CalculationoftheRandomErrorintheVandenAkkerReflectance Symbol ReferenceEquation Value Comments (a)SR (17) .8mm Uncertainty inpackingspherecoatingtoconstantra- dius. (b)Sf (17) 2X10"' CalculatedfromSRabove. (c)s... Open at page → 96 Page 96 COLLIMATEO RECEIVER COLLIMATEO BEAM COLLIMATEO SOURCE Figure6.Arrangementofknife-edgeapparatusformeasuring A',('y). mately700nm.Nodistinctionbetweenthemeasurements underdifferentspectralweightingswereobserved,indicating... Open at page → 97 Page 97 DRSusingthespecialmeasurementaccessoryapparatusfor thispurpose[12].Adiagramofthismeasurementaccessory isreproducedfromthatreferenceinfigure9.Thereflectance valuesweremeasuredforradiationpolarizedwiththeelectric vectorint... Open at page → 98 Page 98 1.5 81.4 uj 1.3- o 0= 1.2 aI.I 1.0 HALON Ng(P) cosr upperlimit straightline throughfirst - threepoints o Ng(r)/cosrlowerlimit I I 30 60 ANGLEOFVIEWINGY (DEG.) 90 Figure11.Anillustrationofthethreeassumptionsusedininterpre... Open at page → 99 Page 99 Fromeq(12)onecandetermineapropagation oferror formulafortherandomerror8p(6°, A.)as: 8p(6°,A.)=[8p„(A.)2+5yVc(6°, +8/Vc{X)^]"^ (36) Inthisformp„,NgandNa_areeachassumedtobe1,and errorscommontoNqandNqareignored,sincethesewi... Open at page → 100 Page 100 Tomakethemeasurements, thereceiverwasplacedinthe samplepositionandasignalNk proportional tothenormal illuminanceIronthesamplewasmeasured. (37) Thereceiverwasthenmovedtoapositionadistancedaway fromthesampleand,onthesamesc... Open at page → 101 Page 101 TableXI ReflectanceFactorofWorkingStandard 1 (RussianOpalClass,Polished) Wavelength (nm) F, , F,, '1.3 F, , '1.2 F,, 400 0.9793 0.9734 0.9738 0.9759 0.9753 423 0.9781 0.9739 0.9743 0.9756 0.9753 450 0.9803 0.9765 0.9779... Open at page → 102 Page 102 TableXIII ReflectanceFactorofWorkingStandard3 (PorcelainEnamel80-1) Wavelengtn (nm) ^3.8 3J ^3.2 400 0.7615 0.7573 0.7571 0.7591 0.7585 425 .7936 .7911 .7915 .7922 .7920 Qf\AO .ouiy .oUoU 4/5 .OVlZ 0A01 .oUol .8079 cnA .... Open at page → 103 Page 103 Therandomuncertainty intheF isgivenby S^cj = t:. (47) ThevaluesoiFc,iandF^.aappearintablesXI,XII,andXIII alongwiththeFcj.Theresultsofthesethreedeterminations arealsodisplayedbywayofsummaryinfigure16. V.Conclusions A.Prec... Open at page → 104 Page 104 WORKINGSTANDARDNO.I (RUSSIANOPALGLASS) •l«tRUN(BaS04) X 2"<*RUN(HALON) O RUN(BaS04) ^AVERAGE |«ta2fKlRUN •WORKINGSTANDARDNO.2 (VITROLITE) •. • •• 400 500 600 WAVELENGTH (nm) 700750 Figure 16.Reflectancefactordiffereruesf... Open at page → 105 Page 105 probablybeattributed totheimprecisionoftheNBSGE spectrophotometer. Theclashedlineatapproximately—0.004indicatesthe combinederrorforthiscomparison.SincetheNRCvalue differsfromthepresentNBSvaluebyovertwicethatamount, itisc... Open at page → 106 Page 106 where (f>r istheretroreflectedfractionofthereflectedflux <l>r=fr<i>i (A2) and (f>i isthediffuselyreflectedfraction (t>i=a-/Hi. (A3) Withthiemodel,thepowerbalanceequation,equation(3)of partIII.A.,takesonthefollowingform.... Open at page → 107 Page 107 wherepisthereflectanceofthespheresurface.(Notethat sincewearetreatingretroreflectance,aischosensothatitis centeredonaradiusinthedirectionofE,andthereforethe directionofincidenceisnormaltoa.)TheareaAoccupiedby thisspherei... Open at page → 108 Page 108 thediameteroftheeffectivelensareaisroughlyone-eighthof thediameterofthebead, itfollowsfromexpressions(A12) and(A16)thatacloselypackedarrayofsuchsphereswould haveareflectancefactorfor^ 1of F(/3)=6XlO^p, (A18) foraspecular... Open at page → 109 Page 109 signofthesystematicerrorsisnotknown,systematicerrors fromindependentcauseswillbeaddedinquadrature,andat eachpointintheanalysisatwhichitisdesirabletoestimatea totaluncertainty, thesystematicerrorandthetotalrandom errorwil... Open at page → 110 Page 110 TableCII Coefficient fortheexpansionofyVj(Fj/cosFinpowersoftheangleofincidenceFinradiansforthreedifferentspherecoatingsandthreedifferent assumptionsconcerningtheself-radiance distribution. Coating CurveType L "0 0 J ^L\J... Open at page → 111 Page 111 100mmby100mmandis11mmthick.ItismarkedV6-D1 foridentification.Thesidewhich ismeasured isflatand highlypolished. WorkingStandardNo.3—Thisstandard isaporcelain enamelonsteelplaquewhichwasmadearound1946by TheHarshawChemicalC... Open at page → 113 Page 113 856 J.Opt.Soc.Am./Vol.71.No.7/JuIy1981 AppendixG V,R.WeidnerandJ.J,Hsia Reflectionpropertiesofpressed polytetrafluoroethylene powder VictorR.WeidnerandJack J. Hsia RadiometricPhysicsDivision,NationalBureauofStandards,Was... Open at page → 114 Page 114 V.R.WeidnerandJ.J.Hsia Vol.71,No.7/July1981/J.Opt.Soc.Am. 857 Fig.1.TheNBSintegrating-sphere-coating apparatusshowingthe hemispheremanipulatorwiththeelectronicallycontrolledtamping headusedtopressthePTFEpowderintothehemi... Open at page → 115 Page 115 858 J.Opt.Soc.Am./Vol.71.No.7/July1981 V.R.WeidnerandJ.J.Hsia Table1.ReflectanceofPressedPTFEPowder(0.8 g/cm^)RelativetoThatofa10-mm-ThickLayerat EachWavelength Thickness RelativeReflectance (mm) 400nm 550nm 700nm 1 0.99... Open at page → 116 Page 116 V.R.WeidnerandJ.J.Hsia Vol.71,No.7/July1981/J.Opt.Soc.Am. 859 Table3.6°/HemisphericalReflectanceFactorofa10-mm-ThickPressedPTFEPowderRelativetoaPerfect Diffuser A A A (nm) p (nm) p (nm) p 200 0.962° 950 0.994 2140 0.964... Open at page → 117 Page 117 860 J.Opt.Soc.Am.A'ol.71.No.7/July1981 V.R.WeidnerandJ.J.Hsia Table4.Directional/Hemispherical ReflectanceFactorofPressedPTFEPowderfora10-mm-ThickCoating (RelativetoHemisphericalReflectanceat6°Incidence) Angle of Inciden... Open at page → 118 Page 118 V.R.WeidnerandJ.J.Hsia Vol.71,No.7/July1981/J.Opt.Soc.Am. 861 Table5.Directional/Directional ReflectanceFactor(BidirectionalReflectance)oflO-mm-ThickPressedPTFE Powder Angle AngleofIncidence of Viewing 300nm 600nm 1500nm... Open at page → 119 Page 119 AppendixH ReprintedfromAppliedOptics,Vol.24,page2225,July15,1985 Copyright©1985bytheOpticalSocietyofi^ericaandreprintedbypermissionofthecopyrightowner. Laboratoryintercomparisonstudyofpressedpolytetrafluoro- ethylenepowd... Open at page → 120 Page 120 Table I.Round-Robin 1;SpectralReflectanceofPressedPTFEPowder VVdVcicIlgtil (nm) 1 I 2 9 Laboratory 2 2 0 Q O 0 o 250 0.973 0.973 0.931 0.935 0.962 0.967 0.922 0.983 0.984 300 0.984 0.984 0.963 0.963 0.974 0.975 0.956 0.9... Open at page → 121 Page 121 TableII.RoundRobin2;SpectralReflectanceofPresssedPTFEPowder Wavelength Laboratory (nm) 1 1 o I 2 2 \3 3 4 5 5 200 0.959 0.963 0.948 0.946 0.947 0.959 0.960 0.888 0.963 0.961 250 0.972 0.974 0.966 0.967 0.968 0.972 0.972... Open at page → 122 Page 122 SomeofthevariationinreflectanceforthePTFE specimenslistedinTablesIandIIcanbeattributedto randomnoise.Atwavelengthsbelow250nmthenoise levelisapproximately±0.003.Inthenear-IRrangeof 2000to2500nm,thenoiseisashighas±0.010. T... Open at page → 123 Page 123 TableIII.DifferencesInSpectralReflectanceofPTFEObtainedfrom ManufacturersAandB W 1 tUW3vclGngtn iX^PnQIirPITIPtltiVlCaoUlCIlICllI/ (nm) differences uncertainty oUU +0.004 ±0.005 +0.003 ±0.005 0\J\J +0.002 ±0.005 DUU +0.0... Open at page → 124 Page 124 plungermadeforaslidingfitintothestainlesssteel cylinder.Theplungerisdesignedsothatwhenfully insertedintothecylinder,itjustreachestheplaneofthe cavityopening.Theplungersurfacecanberoughened bysandblasting ifacoarsersurfac... Open at page → 125 Page 125 Appendix I NISTTechnicalNote1413 45"" 1 0"" ReflectanceFactorsofPressed Polytetrafluoroethylene (PTFE)Powder p.YvonneBarnesandJackJ.Hsia RadiometricPhysicsDivision PhysicsLaboratory NationalInstituteofStandardsandTechnol... Open at page → 126 Page 126 NationalInstituteofStandards U.S.GovernmentPrintingOffice andTechnology Washington:1995 TechnicalNote1413 Natl.Inst.Stand.Technol. Tech.Note1413 23pages(July1995) CODEN:NTNOEF ForsalebytheSuperintendent of Documents U.S.... Open at page → 127 Page 127 TableofContents Abstract 1 1. Introduction 1 2. SamplePressingMethod 2 3. 45°/0°Reflectometer 3 4. Measurements 3 4.1 OperatorVariability 4 4.2 MaterialVariability 4 4.3 45°/0°ReflectanceFactorandUncertainty 4 5. Remarks... Open at page → 128 Page 128 ListofTables 1. OperatorVariability :EachlaboratoryreturnedtwopressedPTFE samples;alpha-numerics indicatethelaboratory(A-J)orthe sample(1 - 2).Thequantityreflectancefactorminustheaverage forthetwentysamplesisshownforeach... Open at page → 129 Page 129 4570"ReflectanceFactorsofPressed Polytetrafluoroethylene (PTFE)Powder p.YvonneBarnesandJackJ.Hsia RadiometricPhysicsDivision,NationalInstituteofStandardsandTechnology, Gaithersburg,MD20899,USA Abstract Pressedpolytetrafl... Open at page → 130 Page 130 Measurements [4].Althoughtheserequirementsspantheultraviolet,visibleandnear infraredspectralregions,mostoftherequestsforcalibrationare45°/0°reflectance factorsinthevisiblewavelengthregion. Thereflectancefactorofasampleis... Open at page → 131 Page 131 isprovidedinAppendixA.ThesafetyaspectsinhandlinganduseofPTFEpowder arelistedinReference8. 3.4570°REFLECTOMETER Theoverallinstrumentconsistsofasourcesystemanda4570°reflectometer [6,9,10]. Thesourcesystemconsistsofatungste... Open at page → 132 Page 132 indicatingagoodrepeatability. Therewasnospectraldependence. TheTypeB uncertainty[12]for k=2was0.0027forthevisiblespectralregion[6].The contributors toTypeBuncertaintywerereceiversystemnon-linearityandnon- uniformity,scat... Open at page → 133 Page 133 interpolatedbysplinefitforotherwavelengths.ThesevaluesarereportedinTable3 togetherwiththeexpandeduncertainties foracoveragefactorof2.These uncertaintiesincludethetypeBuncertainty, statisticalmeasurement uncertainty, oper... Open at page → 134 Page 134 [7]AmericanSocietyforTestingandMaterials:StandardPracticeE259-93,ASTM AnnualBookofASTMStandards06.01(1994)p.709 [8]E.I.DuPontDeNemoursandCompany,Inc.,FluorocarbonsDivision, TeflonFluorocarbonResins-SafetyinHandlingandUse... Open at page → 135 Page 135 Table1. OperatorVariability :EachlaboratoryreturnedtwopressedPTFE samples;alpha-numerics indicatethelaboratory(A-J)orthesample(1 - 2).The quantityreflectancefactorminustheaverageforthetwentysamplesisshownforeach sampleat... Open at page → 136 Page 136 Table2. MaterialVariability :PressedPTFEsamplesfromfourdrums,eachdrum wasmanufactured atadifferenttime.Thequantityreflectancefactorisshownforeach drumatthemeasurementwavelengths.ThemeanandTypeAuncertainty(k= 2)forthe mea... Open at page → 137 Page 137 Table3.45°/0°ReflectanceFactorsofPressedPTFEPowder(1g/cm^) wavGiGngin nGllGCianCG uncGriainiy fnml Factor k=2 380 1.002 0.017 390 1.003 0.017 400 1.005 0.016 410 1.006 0.016 420 1.006 0.015 430 1.007 0.015 440 1.007 0.01... Open at page → 138 Page 138 PLUNGER FUNNEL POWDER RECEPTACLE Figure1.PTFEpowderpresserdesignedtoproduceasamplewithspatial uniformityindensityandinappearance. 10 Open at page → 139 Page 139 Figure2. 45*/0"ReflectometerSystem (TopView) 11 Open at page → 140 Page 140 APPENDIXA. GeneralandAdvancePreparationInformationfor PressingPTFESamples a. PTFEpresser:SincetherearenocommerciallyavailablePTFEpressersthat metourspecifications,asimplePTFEpresserwasdesignedandfabricatedat NIST(Referto... Open at page → 141 Page 141 i. Laboratoryconditions:PTFEpowderiscontaminatedbyairborneparticles andsmokeduetotheelectro-staticcharge(seesec.dabove). j. Safety:ObtainaMaterialSafetyData(MSD)sheetfromthemanufacturerof PTFEpowder.Safetyprecautionsands... Open at page → 143 Page 143 Metrologia17,97-102(1981) metrologia ©bySpringerVerlag1981 NBS45°/NormalReflectometer forAbsoluteReflectanceFactors JackJ.HsiaandVictorR.Weidner NationalBureauofStandards,Washington,DC20234,USA Received:March25,1981 Abst... Open at page → 144 Page 144 grationwithrespecttonvariables. Ingeneral,the nomenclature (especiallythesymbols)usedhereisthat ofreference[11].There itismorecompletelydefined anddiscussed. Ifthere isnointeractionbetweenthewavelength dependence andtheg... Open at page → 145 Page 145 3.NBSReferenceSpectrophotometer The45°/normaI reflectometer isanaccessorytothe NBSreferencespectrophotometer forreflectance [15]. Thelightsource,monochromator, electronicsandother associatedequipment arelocatedinasystemc... Open at page → 146 Page 146 tweenthesurfacesofthelimitingapertureandthe sample isdeterminedwhenthesampleholderisturned 45°fromthenormalposition.Athinglassplate is placedoverthelimitingaperture.Thedistancebetween thisglassplateandaflatsurfaceatthesa... Open at page → 147 Page 147 madewithlightpolarizedparallelandperpendicularto theplaneofincidence.B(0°/d)'swerecalculated for eachpolarizationandtheaveragesobtained. AverageB(O°/0)'satthediscreteintervalswerefitt- edbytheleast-squaresmethod.Individu... Open at page → 148 Page 148 12.E.M.Sparrow,R.D.Cess:Radiationheattransfer (augmented edition) p.121.NewYork:McGraw- HillBookCompany,1978 13.F.E.Nicodemus (ed.):Self-studymanualonopti- calradiationmeasurements: Part I—Concepts, Chap.4and5p.97.Nat.Bu... Open at page → 149 Page 149 AppendixJ JournalofResearchoftheNationalBureauofStandards AWavelengthStandardfortheNear InfraredBasedontheReflectance OfRare-EarthOxides Volume91 Number5 September-October 1986 VictorR.Weidner, PatriciaY.Barnes,and Kenne... Open at page → 150 Page 150 JournalofResearchoftheNationalBureauofStandards trumand2"^ and 4'^ orderlinesofthe656.1nm linewiththenearinfraredgrating. Thespectrophotometer isequippedwithaninte- gratingspherediffusereflectance reflectometer. Thisdevi... Open at page → 151 Page 151 JournalofResearchoftheNationalBureauofStandards 700to2500nmspectralrangeandnoneshowed anypromiseatwavelengthsmuchbeyond2000 nm.Theoxidesofdysprosium, erbium,and holmiumwereselectedbecausetheirinfraredab- sorptionbandsocc... Open at page → 152 Page 152 JournalofResearchoftheNationalBureauofStandards nm.[3]Inadditiontothese,theabsorptionbandof 1-2-4trichlorobenzene at2152.60nm[4]wasalso measured. Thewavelengthscaleofthespectrophotometer wascalibrated atthebeginningofthe... Open at page → 153 Page 153 JournalofResearchoftheNationalBureauofStandards Thespreadofdatapointsinfigures3-1and3-2is indicatedbytheverticalbars.Theaverageofthe datapointswithintheverticalbarisindicatedby theopencircleonthebar.Alinearleast-squares... Open at page → 154 Page 154 JournalofResearchoftheNationalBureauofStandards specimenversusanuncoveredHalonSpecimen (100percent) isshowninfigure4.Thespectral transmittance ofthesapphirewindow isalso showninfigure4. Thedetermination ofthewavelengthso... Open at page → 155 Page 155 JournalofResearchoftheNationalBureauofStandards Table2.Tenmeasurementsofthereflectanceminimaforeach ofthreeabsorptionbandsataspectralbandwidthof4nm, showingthespreadofvaluesobtainedbythegraphicalloca- tionoftheminima.The... Open at page → 156 Page 156 JournalofResearchoftheNationalBureauofStandards Table3.Theadoptedwavelengthsofminimumreflectancefortherare-earthoxidemixtureat25°Candforspectralbandwidths (SBW)of2,3,4,5,and10nm. lare-earth Band SBW SBW SBW SBW SBW oxide... Open at page → 157 Page 157 JournalofResearchoftheNationalBureauofStandards Table4.Theobservedeffectsoftemperatureonthewave lengthsofminimumreflectancefor20°C,25°C,and30°C. Thetemperatureeffectsarenotrevealedbytheobserveddif- ferencesbecauseoflarge... Open at page → 158 Page 158 JournalofResearchoftheNationalBureauofStandards nmor10nm.Thereflectometer isa30cmdiame- terintegratingspherewithalead-sulfidedetector. Measurements arerecordedwiththewavelength drivesetatfixedwavelengths.Ateachwavelength... Open at page → 159 Page 159 JournalofResearchoftheNationalBureauofStandards formeasuringdiffusereflectance iftherequired wavelengthaccuracydoesnothavetobebetter than±1nm. Anuncertaintyof±1nmforthisnearinfrared wavelengthstandard islessaccuratethanc... Open at page → 163 Page 163 THESP250SERIESONNISTMEASUREMENTSERVICES' SP250-1 SpectralRadianceCalibrations PB87179883 SP250-2 FarUltravioletDetectorStandards PB87227609 SP250-3 RadiometricStandardsintheVacuumUltraviolet PB87227625 SP250-4 FrickeDosi... Open at page → 164 Page 164 h £ B o U 8 O00 co E3 _c <U_ Qg .o sz o\ o o ^ Q ^ >~"^ «->« eo , c> Ob 3 fi- ,IU<U .2>^ goO(§i Open at page →