Designation:D5626–94(Reapproved2006)AnAmericanNationalStandardStandardTestMethodsforU.S.PostalServiceOpticalMeasurementsforSmallAreas1ThisstandardisissuedunderthefixeddesignationD5626;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1ThesetestmethodsdealwiththemeasurementofopticalpropertiesimportanttoautomaticequipmentusedbytheUnitedStatesPostalService,suchasopticalcharacterrecog-nition(OCR)readersandbarcodereaders.Thesetestmethodscanbeusedtoexaminefinishedmailpiecesbearingaddressinformation,aswellastheunconvertedmaterialsintendedtobesubsequentlyusedinmailpiececonstruction.Thesetestmethodsarelimitedtotheuseofasingleinstrument,theU.S.PostalServiceEnvelopeReflectanceMeterModel2(ERM-2),2designedforusewithmailpiecesandmaterialsintendedformailpiececonstructionsuchaspaperandpaper-likesyn-theticsandinks.1.2Thesetestmethodscoverexaminationofsmallareas,measuring0.152by0.254mm(0.006by0.010in.).Thisenablesmeasurementofthereflectancecharacteristicsofregionsassmallastheinkedportionofasingleprintedcharacterorasinglebarinabarcodepattern.1.3Thesetestmethodsdealwiththemeasurementoffourdifferentopticalpropertiesimportanttoautomaticmailhan-dling,asfollows:1.3.1BackgroundReflectance(see11.1)—Thesetestmeth-odscoverthedeterminationoftherelativereflectancefactorofsmallareasofaspecimenthatdonotcontainprintingorapparentshow-throughofprinting,andsoarerepresentativeofthebasematerial.1.3.2PrintReflectanceDifferenceandPrintContrastRatio(see11.2)—Thesetestmethodscharacterizethedifferenceinreflectancebetweentheenvelopematerialandthecharactersprintedupontheenvelopewithink.1.3.3PrintShowThrough(see11.3)—Thesetestmethodscharacterizethedifferenceinreflectancebetweentheenvelopematerialbackedwithanunprintedinsertandtheenvelopematerialexaminedinaregionwhereitcoversaprintedcharacteron...
