E1311

blackbodysourcetoanuncertaintynotexceeding0.1°C.7.Procedure

7.1Mountatargetplateandorientthetargetincorrespon-dencewithsomeintegralhourmarkingonanimaginaryclock.Donotdivulgetheorientationtotheobserver.

NOTE4—Onlyoneobserveratatimeistobepresentduringthetesting.

7.2Optimallyfocusthethermalimagingsystemdirectlyonthetargetoronanopticalprojectionofthetarget.

7.3Adjustthethermalimagingsystemforquasi-linearoperation.

7.4Adjustthemonochromevideomonitorcontrolssothatthepresenceofnoiseisbarelyperceivablebytheobserver.7.5Makethedisplayluminanceandthelaboratoryambientluminancemutuallysuitableforvisualacuityandviewingcomfort.

7.6Advisetheobserverthatavisiblespotwilleventuallyappearinthemonitor’sdisplay.Instructhimtosignalwhenhecanperceivethespotandtociteitsorientationrelativetothe12hofaclock;forexample,1o’clock,2o’clock,3o’clock,etc.Refrainfromfurtherconversationduringthetestthatcouldconceivablyinfluenceorbiastheobserver.

7.7SetDT(thetemperatureofthetargetminusthenominaltemperatureofthebackground)equaltozero.

7.8IncreaseDTinpositiveincrementsnotexceeding0.1°Cevery60soruntiltheobserversignals.Iftheidentificationisincorrect,continueasbefore.

NOTE5—ToincreaseDTitiscustomarytofixthebackgroundtemperatureandraisethetargettemperature.

7.9Iftheobservercorrectlyidentifiestheorientationofthespot,recordthediameterofthetarget,thediameterortheheightandwidthoftheFOV,andtheobservationdistancenormaltothetargetplate.

7.10Measurethetemperaturedistributionofthetargetandthetargetbackgroundwithaninfraredspotradiometerreplac-ingthethermalimagingsystem.Thetargetshallbemeasuredinatleastthreelocations,uniformlyspaced.Thebackgroundshallbemeasuredattwozones:(1)adjacenttothetarget(thatis,zone1);(2)beyondzone1(thatis,zone2).Themeasure-mentsineachzoneshallbeuniformlydistributed,withthenumberofzone2measurementsequaltotwicethatofzone1(exceptforthespecialcaseof7.12).

7.11Calculatethemeantemperature,T,ofthetarget.Calculatetheweightedaverage,TB,ofthetargetbackground,inaccordancewith8.3.Provisionally,DT5T−TMDTD.RecordDTandTBistheB.

7.12Ifthetargetsizeandthefieldofviewofthespotradiometerarecomparable,makedoublethenumberofzone2measurements,inpairsconsistingoftwoadjacentlocations.Compareadjacenttemperaturereadings;thedifferencebe-tweenanytwoadjacentreadingsmustbelessthantheMDTD.OtherwisetheMDTDtestresultsareunacceptableforthisparticulartargetsize.

NOTE6—Thiscriterionisintendedtoguardagainstspuriousspots,thatis,falsetargets.

7.13Replacethetargetwithanotherofdifferentsize.Randomlyorientitinaccordancewith7.1andrepeatthetest(7.2through7.12).

7.14Repeatstep7.13oneormoretimes.

7.15Repeattheentiretest(7.1through7.14)withadiffer-entobserver.

7.16Repeatstep7.15oneormoretimes.8.Calculations

8.1CalculatetheangularsubtensesforrectangularFOVsasfollows:

uw5tan21~W/R!@deg#,or

(1)

5103W/R@mrad#;uh5tan21~H/R!@deg#,or

5103H/R@mrad#,

where:W5widthofFOV,

R5observationdistancenormaltocenterpointofFOV,H5heightofFOV,R>>W,and

R>>H.

NOTE7—uwmaybereferredtoasthehorizontalfieldofview,anddenotedHFOV;uhmaybereferredtoastheverticalfieldofview,anddenotedVFOV.

8.2CalculatetheangularsubtensesforcircularFOVsandtargetsasfollows:

u5tan21~D/R!@deg#,or(2)

5103D/R@mrad#,

where:

D5diameterofcircularFOVortarget,asappropriate,

R

5observationdistancenormaltocenterpointofFOVoroftarget,asappropriate,and

R>>D.

8.3Calculatetheweightedaverage,TB,ofthetargetback-groundasfollows:

6(xi1(yj

TB56m1nm

n

(3)

where:

5xi5yjm5n5m

5x(in

5y(j

temperaturemeasurementinzone1,i51,2,...m,

temperaturemeasurementinzone2,j51,2,...n,numberofzone1temperaturemeasurements,numberofzone2temperaturemeasurements,sumofallzone1temperaturemeasurements,andsumofallzone2temperaturemeasurements.

9.1.1Targetangularsubtense,

9.1.2Observationdistancetotarget,9.1.3FOV,9.1.4MDTD,

9.1.5(Weighted)backgroundtemperature,and9.1.6Probabilityofdetection.

9.2MDTDvaluesshouldrelatetoaprobabilityofdetectionofatleast50%.

9.3Whencomparingdifferentsystems,differenttargets,ordifferentangularsubtenses,onlyasingleprobabilityofdetec-tionshouldbeusedthroughout.

NOTE9—AplotofMDTDversustargetangularsubtenseisaconve-nientformforreportingthedataforagivensystemoragiventarget.

10.PrecisionandBias

10.1Precision—Insufficientdataareavailableuponwhichtoformulateaprecisionstatement.Notwithstanding,owingtothepartiallysubjectivenatureofthetest,repeatabilityandreproducibilityareapttobepoorandMDTDdifferenceslessthan0.2°Careconsideredtobeinsignificant.

10.2Bias—Theproceduresetforthinthistestmethodformeasuringtheminimumdetectabletemperaturedifferenceforthermalimagingsystemshasnobiasbecausetheminimumdetectabletemperaturedifferencecanbedefinedonlyintermsofatestmethod.11.Keywords

11.1infraredimagingsystems;minimumdetectabletem-peraturedifference;nondestructivetesting;thermalimagingsystems;thermography;infrared

NOTE8—Seventy-fivepercentofTBisweightedinthevicinityofthetarget.

8.4Calculatetheprobabilityofdetectionasshownbythefollowingillustration:

8.4.1Foragiventargetsize,theMDTDresultsobtainedwiththreedifferentobserversare0.5°C,0.6°C,1.0°C.Theobserverwhodetected0.5°Cwouldalsobecapableofdetect-ing0.6°Cand1.0°C.Similarlytheobserverwhodetected0.6°Cwouldalsobecapableofdetecting1.0°C.Hence,therespectiveprobabilitiesofdetectionare:for0.5°C,1⁄3533%;for0.6°C,2⁄3567%;for1.0°C,3⁄35100%.9.Report

9.1Reportthefollowinginformation:

TheAmericanSocietyforTestingandMaterialstakesnopositionrespectingthevalidityofanypatentrightsassertedinconnectionwithanyitemmentionedinthisstandard.Usersofthisstandardareexpresslyadvisedthatdeterminationofthevalidityofanysuchpatentrights,andtheriskofinfringementofsuchrights,areentirelytheirownresponsibility.Thisstandardissubjecttorevisionatanytimebytheresponsibletechnicalcommitteeandmustbereviewedeveryfiveyearsandifnotrevised,eitherreapprovedorwithdrawn.YourcommentsareinvitedeitherforrevisionofthisstandardorforadditionalstandardsandshouldbeaddressedtoASTMHeadquarters.Yourcommentswillreceivecarefulconsiderationatameetingoftheresponsibletechnicalcommittee,whichyoumayattend.IfyoufeelthatyourcommentshavenotreceivedafairhearingyoushouldmakeyourviewsknowntotheASTMCommitteeonStandards,100BarrHarborDrive,WestConshohocken,PA19428.