Regular Spectral Transmittance

1 Page 1 NBSMeasurementServices: Regular Spectral Transmittance NBS Special Publication 250-6 U.S.DepartmentofCommerce NationalBureauofStandards Open at page → 2 Page 2 CenterforRadiationResearch TheCenterforRadiationResearchisamajorcomponentoftheNationalMeasurementLaboratory intheNational BureauofStandards. TheCenterprovidestheNationwithstandardsandmeasurementservicesforionizing radiat... Open at page → 3 Page 3 NBSMEASUREMENTSERVICES: REGULARSPECTRALTRANSMITTANCE KennethL.Eckerle JackJ.Hsia KlausD.Mielenz VictorR.Weidner CenterforRadiationResearch NationalMeasurementLaboratory NationalBureauofStandards Gaithersburg,MD20899 U.S.... Open at page → 4 Page 4 LibraryofCongressCatalogCardNumber:87-619840 NationalBureauofStandardsSpecialPublication250-6 Natl.Bur.Stand.(U.S.),Spec.Publ.250-6,59pages(July1987) CODEN:XNBSAV Commercialproducts—materialsandinstruments—areidentifiedi... Open at page → 5 Page 5 PREFACE Thecalibration andrelatedmeasurement servicesoftheNationalBureau ofStandardsareintendedtoassistthemakersandusersofprecision measuringinstruments inachievingthehighestpossiblelevelsof accuracy,quality,andproductiv... Open at page → 6 Page 6 Abstract Thisdocumentation describesmeasurement services,instrumentation, standards, andmeasurementtechniquesforregularspectraltransmittance over thespectralrangeof200to2500nm. Itisdividedintothreeparts. Part Idescribest... Open at page → 7 Page 7 TABLEOFCONTENTS Paqe Abstract iv I.Measurement Services,PhilosophyandAvailableStandards 1 A.MeasurementPhilosophy 1 B.Description ofServices 1 C.StandardReferenceMaterials andMeasurementAssuranceProgram 3 II.ReferenceSpe... Open at page → 8 Page 8 TABLEOFCONTENTS(cont'd) Page III.TransferSpectrophotometer forRegularTransmittance 35 A.DescriptonoftheInstrument 35 1.WavelengthRange 35 2.BandwidthRange 35 3.PhotometricRange 35 4.TemperatureControl 36 5.DataAcquisitio... Open at page → 9 Page 9 TABLEOFCONTENTS(cont'd) Page LISTOFTABLES 1.CalibrationServicesforSpectrophotometry 2 2.StandardReferenceMaterialsforSpectrophotometry 4 3.Range,Source,Grating,DetectorandMeasurement Modefor WavelengthRanges 18 4.Wavelen... Open at page → 10 Page 10 LISTOFFIGURES Page Fig.1.DiagramPertainingtotheDefinitionofRegular Transmittance 6 Fig.2.SchematicofReferenceSpectrophotometer asUsedinthe Ultraviolet andVisible 10 Fig.3.SchematicofReferenceSpectrophotometer asUsedinthe... Open at page → 11 Page 11 I.Measurement Services,Philosophy andAvailableStandards A.MeasurementPhilosophy Regularspectraltransmittance measurements provideusefulinformation onthepropertiesofmanymaterials. NBSstrivestoprovidethebest possiblestanda... Open at page → 12 Page 12 Table 1 Calibration ServicesforSpectrophotometry Old New Instrument Number Number 7.8A 38060S R,T Spectrophotometric measurementservices (SpecialTestsonly)Transmittance and Reflectance. 7.8B 38010C T Spectraltransmittanc... Open at page → 13 Page 13 Withthetransferinstrument, surveyspectralscansareavailableona limitedbasisforapplications wheresuchsurveysofsamplesareneededbut highaccuracy isnotrequired. Forareducedfee,uncorrecteddigitalor analogdataareprovidedwithout... Open at page → 14 Page 14 Table2 StandardReferenceMaterialsforSpectrophotometry Special PublicationSRMNumber Description 260-51 930 GlassFiltersforSpectrophotometry 260-51 2030 GlassFilterforTransmittanceMeasurements 260-68 2031 Metal-on-Quartz F... Open at page → 15 Page 15 Transmission isthepassage(withoutchangeinwavelength) ofoptical radiationthroughtran-sparent ortranslucentmedia. Transmissionmaybe regular(withoutchangeindirection) ordiffuse(spreadingoutindifferent directions). Transmiss... Open at page → 16 Page 16 6 Open at page → 17 Page 17 andthesame. Letn=n(l+ik)bethecomplexindexofrefraction ofthe slabmedium, n'theindexofrefraction oftheinitialandfinalmedia,and 9'theangleofincidence. Undertheseconditions, theregularspectral reflectance oftheslabisgivenby:... Open at page → 18 Page 18 rapidlyoscillatinginterferencetermdependingon(t/x)inadditiontothe attenuationtermthatdeterminestheabsorptionofthefilterasafunction oftheattenuationcoefficient kandfilterthickness t.Asaconsequence, thetransmittance T(x,0'... Open at page → 19 Page 19 B.Instrumentation TheNBSreferencetransmittance spectrophotometer (RTS)hasbeen described indetailinpreviouspublications [1,2,3,4]. Abriefdescription oftheinstrument, practicalsuggestions foritsuse,andsomeofitslimi- tation... Open at page → 20 Page 20 10 Open at page → 21 Page 21 grooves/mmblazedat1250nmrespectively. Themonochrornator collimatinq andfocusingmirrorsareoff-axisparabolas,paraboloidal towithin0.1 fringeingreenlightandfreeofzones. Thesemirrorscanbemovedalonga railandadjustedbymicromet... Open at page → 22 Page 22 i5 Q.z2 Oq:<E XUJ^ OO Q. UTER 2>a: 4 — IRENT EQUEN NVERT OUNTE 'Willr o 50:00 -a s- S- rO O) -a 0) (/) in 03 S- cu 4-> (U o -l-> o O- o s- +J o cu Q. iA CU o (U s- ^- OJ s- <4- O a •r— 4-> rd E CU o C7) 12 Open at page → 23 Page 23 lock-inamplifierwherevoltageoutputisconvertedtoacurrent. Otherwise, theinstrument isoperated inthesamemannerasintheultraviolet and visible. 2.OpticalAlignment TheopticalalignmentoftheRTSisbasedonpre-determinedvaluesof th... Open at page → 24 Page 24 4.MeasurementCapabilities andRequiredSampleProperties Thefollowinginformation isprovidedtoacquaintuserswiththetypesof measurements thatcanbeperformedontheRTS.Alsolistedaretherequired propertiesofuser-submitted samplestha... Open at page → 25 Page 25 takentoavoidcontactwiththemetalfilm,sincescratchesandothermarks cangreatlydegradesuchafilter. d.MeasuredArea. Theusualprocedureforthevisiblespectralregionistomeasurean averagetransmittance overacentralareawhichissmallert... Open at page → 26 Page 26 polarizer inthespectrophotometer beamalongwiththefilter,andmeasure thetransmittance ofthecombinationwiththefilterrotated in45° incrementsaboutitsnormalwhilethepolarizerremainsfixed,orvice-versa. Forauniformnon-polarizing... Open at page → 27 Page 27 j .FiIterSize. FiltershavingthefollowingcommonsizescanbemeasuredontheRTS eithersinglyoringroupsoftwoorthree: 5.1cmX5.1cmsquare 3cmdiametercircular 1.3cmX1.3cmx5.7cmcuvette 1.1cmX3.05cmrectangle. (Othersizesoffiltersupto1... Open at page → 28 Page 28 Table3 Range,Source,Grating,DetectorandMeasurementModeforWavelengthRanges Wavelength Source Grating Detector Niode (nm) 200-400 DeuteriumArc 600l/mm,200nm PhotomuItiplier D.C. (28w) blaze 360-800 TungstenStripLamp 600l/m... Open at page → 29 Page 29 levelsofuncertaintythanthatformeasurementsmadewiththeRTS.) Unless thereisadefiniteneedforaqivenbandwidth, itisusuallybesttochoose thelargestbandwidthwhichcanprovidetheinformation aboutthefilter. Forfilterswithstrongspect... Open at page → 30 Page 30 TABLE4 Wavelengths ofAtomicEmissionLinesUsedforWavelength Calibrations intheUVandVisibleSpectrum a.Linesusedwiththe.25mmapertures L. 1CMIC 11I' rtuVC 1CI1U1 1 F1pmpn 1" wavc 1ci 1^L1 1 1nm 1 vnm ; *TJ •yj0\J Hpnc JOO•OUJ... Open at page → 31 Page 31 Table5 Wavelengths ofAtomicEmissionLinesandMolecularAbsorptionBands UsedforWavelengthCalibrations intheNearIRSpectrum ElementorChemical (nm) TypeofSpectra Rb 780.02 EmissionLine Rb 794.76 EmissionLine Hg 1013.98 Emission... Open at page → 32 Page 32 (uiu)N0ii3ad»03 SAiiiaav 22 Open at page → 33 Page 33 Theseuncertainties areupperboundsandmayberegardedashaving a99.7% confidence level(3aequivalent). Allupperboundsinthispublication will beequivalentto3auncertainties. 2.LinearityofthePhotometric Scale, Allmeasurements with... Open at page → 34 Page 34 .2 .4 .6 .8 1.0 Fig.5:Additivecorrection,aT,versustransmittance T(<^) Theshadedarearepresents±1standarddeviation. 24 Open at page → 35 Page 35 3.StabilityofSourceandDetectionSystem ThestabilityrequiredoftheRTSissuchthatafilterwithtrans- mittance0.5canbemeasuredwithastandarddeviationof0.00005. Two sourcesofinstabilityhavebeenfoundtodate. Oneisthephotomult i piie... Open at page → 36 Page 36 2.SampleAlignment. Thealignmentlaserisusedtoaidinpositioningthesamplesbymeansof threealignmentscrewsonthesamplewheelorslider. Withthewheel, samplesareusuallyalignednormaltothebeam,sothatthelaserlightis reflectedbackintot... Open at page → 37 Page 37 Thedarkreadingsareinterpolated intimeandsubtractedfromeachclear- spaceorfilterreadingbeforeanyfurtheranalysis, ^01 to5 Let t^ = 2 (6) bethetimehalf-waybetweentimestgiandto5atwhichreadings IqiandIqs aretaken. Toreducethen... Open at page → 38 Page 38 andanew iscalculatedusingEq,(9b). Thisprocess isrepeateduntil s2issufficiently small(lO"^^- TheI^-'sgivingthiss^areusedto calculatethetransmittance forthenthfilter. T=— , n=1,2,3 Thesamplestandarddeviation s^of is ^n = "... Open at page → 39 Page 39 andwhereI(vt)istheirexpectation value,obtainedfromaleast-squares fit ofthemeasureddataasalinearfunctionoftime. Thevalvesoperatingthetwoapertureshuttersareactuatedbythedata acquisition andcontrolsystemofthespectrophotomet... Open at page → 40 Page 40 wheredlisthephotometricerrorofthespectrophotometer definedbyEq. {15a). E.Uncertainties 1.Instrumental Bias BecauseofthespecialdesignoftheRTS,thecombinedsystematicerror introducedbythespectrophotometer itselfintomeasureme... Open at page → 41 Page 41 featuresaremeasured,theerrorcalculatedfromtheaboveformulawillbe included intherandomerrorquotedforthemeasurement. Straylight: Theerrorduetostraylightalsodependsonthe transmittance spectrumofthesample. Fromthemeasurements... Open at page → 42 Page 42 32 Open at page → 43 Page 43 valuesofnon-uniformity are0.1to0.5percentofthetransmittance (equivalent toa3asystematicuncertainty). Thermochromism becomes aproblemforthemeasurement ofcoloredfilters. Whensuchfiltersaremeasured, itisnecessarytomonitorth... Open at page → 44 Page 44 Table6 TypicalOver-allUncertainties forNBSReferenceSpectrophotometer Transmittance SourceofError T = 0.01 T=0.1 T = 1.0 A.InstrumentalBias(Systematic) 2.0X10-5 1.0X 10-'+ 1.0X 10-'+ B.RandomError \oXoLanaaruueviaLion^ 1.... Open at page → 45 Page 45 loweringtheenclosuretoensurethatturningtheliftmechanismresults in movementoftheenclosure. Theusualprecautions areobservedwhenusing chemicalsforstraylighttests. Otherprecautionstakenaretheusualones whenworkingwithelectric... Open at page → 46 Page 46 parameterdisplaymonitorscreen,whenthedensityexceeds4.5.Thissame message isdisplayed inthetransmittance modewhenthetransmittance isless than0.01%. Inordertomeasurehigherdensitiesthan4.5,specialphoto- etchednickelscreensar... Open at page → 47 Page 47 Table7 EmissionLinesandAbsorptionBandsUsedtoCalibrate theTransferSpectrophotometer WavelengthScale. EmissionLines: Hg:253.65nm,334.15nm,435.83nm,1014nm,1529nm. D2:486.0nm,656.10nm,1312.2nm,1968.3nm,2624.4nm. Note: Thelas... Open at page → 48 Page 48 TheD2linesareproducedbythedeuterium lampbuiltintothespectro- photometer, andareusedinautomatedday-to-daywavelengthscalechecks. In theUVandvisiblethe486.0nmand656.1nm linesareusedinthefirst gratingorder,andinthenearIRthey... Open at page → 49 Page 49 Thenon-linearity oftheleadsulfidedetectorwasdeterminedby comparingtransmittance measurements at770nm.Thefollowingdifferences werefound,andareappliedasnon-linearitycorrections formeasurements madewiththeleadsulfidedetecto... Open at page → 50 Page 50 4.Stability Thewavelengthscaleerrorwillremainconstantafterawarm-uptimeof approximately onehour,ifthetemperature oftheinstrumentremainsstable. Thephotometricscaledriftischeckedbyobservingchangesinthebaseline (100%)calibra... Open at page → 51 Page 51 2.MeasurementSequenceforTransmittance orAbsorbance Themeasurements arerecorded inthesequence: 100%,testsample,100%. Intheabsorbancemode,thesequence isthesameexceptthatthe100%becomes thezeroabsorbancecalibration. 3.DataRe... Open at page → 52 Page 52 used,theuncertaintyduetodriftwillnotexceed0.0015. Thedriftis linearandcanbeminimizedbyrecordingthe100%calibration atshortertime intervals andcorrectingforchangesinthiscalibration. Theestimated typicaluncertainties (3o)ar... Open at page → 53 Page 53 Table8 SummaryofEstimatedUncertainties inPercentofSpectral Transmittance ValuesforNBSTransferSpectrophotometer [A Representative Analysis(ThreeSigma)intheVisibleRegionfor TransmittancesintheRange.1-1.0] Wavelength Strayr... Open at page → 54 Page 54 REFERENCES 1.Mielenz, K.D.,Eckerle, K.L.,Madden,R.P.,andReader,J.,"New ReferenceSpectrophotometer", Appl.Opt.j2(7),1630(July1973). 2.Mielenz, K.D.,andEckerle, K.L.,"Design,Construction, andTesting ofaNewHighAccuracySpect... Open at page → 55 Page 55 References(cont'd) 11.CIEPublication No.17(E-1.1)1970,International LightingVocabulary , 3rdEdition,BureauCentraldelaCIE,Paris(1970). 12.Eckerle, K.L.,Venable, W.H.Jr.,andWeidner, V.R.,"Averaging SphereforUltraviolet, Vi... Open at page → 57 Page 57 APPENDIXA U.S.DepartmentofCommerce NAT[ONALBUREAUOFSTANDARDS GAITHERSBURG.MARYLAND20899 REPORTOFTEST for SpectralTransmittance of FourNeutralFilters Submittedby LaboratoryA (Authorization forthistestwasgiveninPurchaseOrd... Open at page → 58 Page 58 APPENDIXA REPORTOFTEST Page2 withtheelectricvectoroftheincidentradiationhorizontal (0°)and vertical(90°). Thesolidanglesubtendedatthesamplebythedetec- tionsystemwasapproximately 0.0027steradians. Theilluminatedarea onthe... Open at page → 59 Page 59 APPENDIXA Erroranalysisformeasurements oftransmittance usingthereference Thetransmittance Tofafilterrelativetoaircanbecalculated fromtheexpression whereT„isthetransmittance ofareferencefilter,andTnisthetrans- mittanceoft... Open at page → 60 Page 60 X I—I <u Q r— LU fO a. h- a. to CO ^s cy»0CM LlJ CO C\J 10 >0000 0000 0000 0000 0000 4J +-> +-> < • • • • 0000 4-) O) to (O S- •t-> •r" (O UJ O ^ ^ to CM to0 •r— 0 0)0 0toCM u CTt^ ^s CM CX)to0 toc—UJ LU CD r— 1 — CO fO... Open at page → 61 Page 61 -o o s- CU O «3 c -o +->o 1 — • Stan of iati E s_ -a £Z to . O) 03 +-> +J S- 000toLO o 'r—c 00«^CO0 CO (U 4- CO •sd-CMCMCM • tooo 000000 •I — 000000 CU CU 00000 vo ,— ^ o 00000 O -M i- 1—00000 4->O <00000 fO +->o LU fO t... Open at page → 63 Page 63 APPENDIX B U.S.DepartmentofCommerce NATIONALBUREAUOFSTANDARDS GAITHERSBURG.MARYLAND20899 REPORTOFTEST for SpectralTransmittance of OneTiffenNeutralDensityFilter Submittedby: Laboratory B (ReferencePurchaseorderNo.ABCdate... Open at page → 64 Page 64 APPENDIXB REPORTOFTEST Page2 Thedataforthetestfilterwerecorrectedforsmallvariations inthezerocalibrationandconvertedtoequivalentvaluesofspectral transmittance. Theresultsofthedatareductionarelistedintable1. 5.Uncertainti... Open at page → 65 Page 65 APPENDIXB TABLE 1 TIFFENN.D.FILTER60%#511 TRANSMITTANCE WAVELENGTH (NM) {%) 380 59.95 390 61.82 400 62.70 410 62.59 ' 420 62.42 430 62.33 440 62.22 450 62.37 460 62.56 470 62.57 480 62.57 490 62.56 500 62.60 510 62.60 52... Open at page → 67 Page 67 roilMNBS-l14A(REV.11-84) U.S.DEPT.OFCOMM. BIBLIOGRAPHICDATA SHEET(Seeinstructions) | NBS/SP-250/6 1.PUBLICATIONOR REPORTNO. 2.PerformingOrgan.ReportNo 3.PublicationDate July1987 4.TITLEANDSUBTITLE NBSMeasurementServices:... Open at page → 69 Page 69 I Open at page → 71 Page 71 PUBLICATIONS INTHESP250SERIESFROMTHECENTERFORRADIATIONRESEARCH SP250-1 NBSMeasurement Services: SP250-12 SpectralRadianceCalibrations J.H.Walker,R.D.Saunders, andA.T.Hattenburg SP250-2 NBSMeasurement Services: SP250-13 F... Open at page → 72 Page 72 U.S.DepartmentofCommerce NationalBureauofStandards Gaithersburg,MD20899 OfficialBusiness PenaltyforPrivateUse$300 Open at page →