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1、Extractfrom:D.Maltoni,D.Maio,A.K.Jain,S.PrabhakarHandbookofFingerprintRecognitionSpringer,NewYork,20032.6:FingerprintScannersandtheirFeatures(extract)(Copyright2003,SpringerVerlag.AllrightsReserved.)2.6FingerprintScannersandtheirFeatures69•Mosaicking:Theenhancedtransla
2、tionvectorsproducedbytherelaxationstageareusedtoregisterandsuperimposetheslices.Finally,eachpixelofthereconstructedoutputimageisgeneratedbyperformingaweightedsumoftheintensitiesofthecor-respondingpixelsintheslices.2.6FingerprintScannersandtheirFeaturesSeveralfingerprin
3、tscanners,basedonthesensingtechnologiessurveyedinSection2.4,arecommerciallyavailable.Certainly,themaincharacteristicsofafingerprintscannerdependonthespecificsensormountedwhichinturndeterminestheimagefeatures(dpi,area,anddy-namicrange),size,cost,anddurability.Otherfeatu
4、resshouldbetakenintoaccountwhenafingerprintscannerhastobechosenforaspecificapplication.•Interface:FBI-compliantscannersoftenhaveanalogueoutput(e.g.,RS-170)andaframegrabberisnecessarytodigitizetheimages.Thisintroducesanextracostandusuallyrequiresaninternalboardtobemount
5、edinthehost.Ontheotherhand,innon-AFISdevices,theanalogue-to-digitalconversionisperformedbythescannerit-selfandtheinterfacetothehostisusuallythroughasimpleParallelPortorUSBconnection.•Framespersecond:Thisindicatesthenumberofimagesthescannerisabletoac-quireandsendtotheho
6、stinasecond.Ahighframerate(e.g.,largerthan5frames/sec)bettertoleratesmovementsofthefingeronthesensorsandallowsamorefriendlyinteractionwiththescanner.Itcanalsoprovideanaturalvisualfeedbackduringtheacquisition.•Automaticfingerdetection:Somescannersautomaticallydetectthep
7、resenceofafin-gerontheacquisitionsurface,withoutrequiringthehosttocontinuallygrabandprocessframes;thisallowstheacquisitionprocesstobeautomaticallyinitiatedassoonastheusersfingertouchesthesensor.•Encryption:AsdiscussedinChapter9,securingthecommunicationchannelbetweenthe
8、scannerandthehostisaneffectivewayofsecuringasystemagainstattacks.Forthispurpose,somecommercialscannersimplementstate-
