sormenjälki

Basictypes

Therearethreebasicshapesoffingerprintlines-whorl,archandloop.Itisthesubcutaneoustissueoppositetothetopofthefingerbelly.Thedifferentpressingdirectioncreatesthisdifferentshape.Studieshaveshownthatifsomeone’sfingeristallandround,thepatternoftheirfingerprintswillbespiral.Scientistshavebeenabletoreproducethemorecommonfingerprintsthroughthemodel,andcanalsorepeattheformationprocessofthelesscomplicatedrarefingerprints.

Fingerprintstructure

Fingerprints,alsocalledhandprints,havebroadandnarrowmeanings:fingerprintsinanarrowsenserefertothepatternofmastoidlinesonthepalmsurfaceofthefirstsectionofahumanfinger;Inabroadsense,fingerprintsincludefingerprints,knuckleprintsandpalmprints.Thereisaliteraldifferencebetweenfingerprintsandfingerprints,thatis,fingerprintsrefertothepapillarylinepatternonthepalmsurfaceofthefirstfinger,andfingerprintsarethemarksleftbythispapillarylinepattern.However,injudicialpractice,itiscustomarythatfingerprintsandTheconceptoffingerprintsisuniversal.

Theimprintsaremainlyduetothepresenceofalargenumberofsweatglandsandsebaceousglandsontheskinofhumanfingersandpalms(thinkofthesweatinyourpalmswhenyouarenervousorexcited).Aslongaslifeactivitiesexist,Sweatandsebumarecontinuouslydischarged.It'sabitlikeanatomicsealthathasinkconstantlypermeatingthesurfaceoftheprintedtext.Therefore,aslongasthefingerorpalmtouchesthesurfaceoftheobject,itwillautomaticallyleaveamarklikeanatomicseal.Ofcourse,thisismainlythereasonwhythefingersandpalmsthemselvescanleavefingerprints.Ifthefingersandpalmsarestuckwithotherliquid-likesubstances,suchasoilsontheheadandface(thisisthe"inkpad"youusemostoften),blood,andinktoholdfingerprints,theprincipleofleavingfingerprintsismorelikeanormallid.seal.

Fingerprintforensics,includingfingerprintsearchanddiscovery.Thescopeoffingerprintsearch:(1)thecriminalactivitycenter;(2)theimportandexportofthesceneanditssurroundings;(3)theitemsthatthecriminalsmayhavetouched;(4)thevariouslethalweaponsandobjectsleftbythecriminalsonthescene.

Andtheircomplexityissufficienttoprovideenoughfeaturesforidentification.Inadditiontobeingunique,fingerprintsarealsohereditaryandimmutable.Ithasnotbeenfoundthatdifferentpeoplehavethesamefingerprints,soeachperson'sfingerprintsarealsodifferent.Becausefingerprintsareuniquetoeveryone,fingerprintsleftbycriminalsatthesceneofcrimeshavebecomeimportantcluesforthepolicetopursuesuspectsinthepastfewhundredyears.Nowadays,fingerprintidentificationmethodshavebeencomputerized,makingtheidentificationprocessfasterandmoreaccurate.

Becauseeveryonehasdifferentgeneticgenes,fingerprintsarealsodifferent.However,althoughtheformationoffingerprintsismainlyaffectedbygenetics,therearealsoenvironmentalfactors(5%).Whenthefetusdevelopsinthemother'sbodyforthreetofourmonths,thefingerprintsarealreadyformed,andthefingerprintsofchildrenwillslightlychangeduringthegrowthperioduntiladolescence.Theshapeisonlysetataround14yearsold.Intheprocessofskindevelopment,althoughtheepidermis,dermis,andstromallayersallgrowtogether,thesoftsubcutaneoustissuegrowsfasterthantherelativelyhardepidermis.Somepeoplesaythatfingerprintswillchangeafterbonemarrowtransplantation,whichiswrong.Unlessitisskingraftingordamagethatreachesthebasallayer,fingerprintswillnotchange.

Formthefoundation

Duringthedevelopmentoftheskin,althoughtheepidermis,dermis,andstromallayersareallgrowingtogether,thesoftsubcutaneoustissuegrowsfasterthanthehardepidermis,soitwillTheepidermisproducesasteadystreamoftoppressure,whichforcestheslower-growingepidermistoshrinkandcollapsetowardtheinnerlayeroftissues,graduallybendandwrinkle,soastoreducethepressureexertedbythesubcutaneoustissuesonit.Inthisway,ontheonehand,itisforcedtoattackupwards,andontheotherhand,itisforcedtowithdraw,causingtheskintogrowtortuously,pitsanduneven,forminglines.Thisprocessofbendingandwrinklingfluctuateswithchangesintheupperpressuregeneratedbytheinnertissue,formingunevenridgesorfolds,untilthedevelopmentprocessisstopped,andfinallyshapedintoafingerprintthatwillnotchangetodeath.

Geneettiset ongelmat

Ovatko sormenjäljet ​​periytyneet?

Althoughtherearenotwoidenticalfingerprintsintheworld,thefingerprintsofidenticaltwinsarerelativelysimilar.Moreover,thepatternsofdifferentfingersofthesamepersonalsohavesimilarities.Thestudyfoundthattherearegenderdifferencesandethnicdifferencesinfingerprinttypeswithhighoccurrencerates.Forexample,inthefingerprintsofChineseandJapanese,theoccurrencerateofbucketpatternandskippatternisroughlythesame,accountingformorethan90%ofthetotal;inthefingerprintsofEuropeans,theoccurrencerateofskippatternishigher;inthefingerprintsofAmericans,Theappearancerateofbowpatternishigher.

Becausethefingerprintsofidenticaltwinsorthesameracearesimilar,itcanalsobesaidthatfingerprintscanbe"inherited".However,theformationoffingerprintsisnotonlyaffectedbygeneticgenes,butalsobyenvironmentalfactors.ProfessorKazuInoueofHokkaidoUniversityinJapanhasbeenengagedinanatomicalresearchforalongtime.Hesaid:"Thedetailsofhumanbodyalsovaryfrompersontoperson.Becausefingerprintsareveryconvenienttouse,theyarewidelyusedtoidentifyidentity."

Muodostettiinko sormenjälkiä?

Whenthefetusdevelopsto4months,ithasalreadyformedafingerprint.Beforethat,about10weeksofdevelopment,fingertipsandotherpartswilltemporarilyformalargeball-shapedbulge—justlikethepadofacat'spaw,whichplaysadecisiveroleintheformationoffingerprints.

Whenthebulgebeginstoshrinkandcollapse,wrinklesbegintoappearatthejunctionoftheepidermisandthedermis.Thisisthebudding"fingerprintmold".Thecellsgeneratedbythefingerprintmoldsqueezehardtothesurface,andwhenthefetusdevelopsto4months,itwillformfingerprintsontheepidermis.Researchsuggeststhatfingerprintsaredevelopedfromdenselyarranged"molds"onthebulgesurface.Therefore,theshapeandsizeoftheoriginalbulgedeterminestheshapeofthefingerprint.

Usesoffingerprints

Asweallknow,fingerprintshavethecharacteristicsof"differentandunchangingforlife".Longago,peopleusedhandprintsonpaperorwoodenboardstoidentifytheiridentity.Fingerprintshavebeenwidelyusedinareassuchasentryinspectionsandcriminalsearches.Fingerprintsarelinesformedbylinearlyarrangedprotrusionsanddepressionsontheepidermis,"akindofskinpattern".Humanhandsandfeetarecoveredwithskinlinesontheinside.Fingerprintsarewidelyusedinareassuchassearchingforcriminalstoidentifyidentities.Asweallknow,theBabyloniansandChinausedfingerprintstoverifytheidentityofapersonalongtimeago.

Usingfingerprintstoidentifyidentity,thisisbecausefingerprintsmeetthefollowingtwoconditions:

Firstofall,fingerprintsarenotthesame,andtherearenotwoidenticalfingerprints.Althoughidenticaltwinshaveahighdegreeofsimilarityintheirpatterns,theirdetailedfeaturesarenotexactlythesame,buttherearecertaindifferences(seeFigure1forfeaturepoints).Inaddition,thefingerprintsofdifferentfingersofapersonarealsodifferent.

Secondly,aperson’sfingerprintisinprinciplethesameforlife.Whenachildgrowsup,thefingerprintisonlyenlargedandthickened,anditspattern,numberoflinesandothercharacteristicsremainunchanged.

Figure2showsthethreetypesoffingerprints(skippattern,bucketpattern,bowpattern),andshowsasubcategoryofbucketpatternandbowpattern.Thepictureontherightshowstheinternalstructureoftheskin.Althoughthereareothertactileorgans,onlythepartsinvolvedinthetextareshownhere.

Thedermisislocatedinthelowerlayeroftheepidermis,andthejunctionbetweentheepidermisandthedermisisunevenandintricate.Theseconcavitiesandconvexitiesare"molds"andfinallyformfingerprintpatterns.Eveniftheepidermisiswornoff,aslongastheinnerdermislayerisnotdamaged,thesamefingerprintscanstillgrowaftertheinjury.Theclarityoffingerprintswillgraduallyblurwithage.In1880,Fulders,aBritishmissionaryanddoctorlivinginJapan,publishedthefirststudyonfingerprintsintheBritishacademicjournal"Nature",expoundingforthefirsttimethatfingerprintrecognitionisusedincriminalinvestigationandotherfields.Theapplicationof,createdaprecedentformodernfingerprintresearch,whichwasintroducedtoAsiain1900andwasputintopractice.

Peoplehavealwaysbelievedthatfingerprintscannotonlyhelppolicesolvecrimes,butalsoenhanceskinfriction.However,afterscientistsmeasuredtheinfluenceoffingerprintsonfriction,theycameupwithdifferentresults.

Thescientistsfirstaskedthevolunteerstopresstheirfingersontheglasstocalculatetheaveragefrictioncausedbythefingerprintsatthistime;then,theyaskedthevolunteerstograduallyincreasethepressureonthefingersandperformcalculations.Itturnedoutthatthefrictiondidnotincreaseasexpected.Furthermicroscopicexaminationrevealedthatthefingerprintslookedlikegulliesunderthemicroscope,withgapsbetweenthem.Comparedwithaperfectlysmoothfingersurface,thecontactareawasreducedbyabout1/3.Thisisabitsimilartorubber,andthefrictionvarieswiththecontactarea.Basedonthis,scientistsbelievethatfingerprintsactuallyreducefriction,makingtheskineasiertostretchanddeform,sothatitcanavoidskindamage.

Havainnointimenetelmä

Eri perinteisten menetelmien mukaan sormenjäljet ​​voidaan jakaa kolmeen luokkaan:

Ensimmäinen luokka onpatentinjälki,joka on kohdetulos. Viivoja voidaan nähdä näkemällä.Esimerkiksi käsin kastettu maali, veri, mustetta ja muita esineitä siirretään, tavallisesti tulostetaan sormenjälkikorttiin, jotta niistä tulee perustietoja;

Thesecondtypeisplasticprint,whichreferstothesoftSubstances,suchasfingerprintsimprintedoncandlesandclaybyhandcontact;

Thethirdtypeislatentprint,whichisafingerprintthatistransferredbythebody’snaturalsecretionssuchassweat.Thelinesarenoteasytofindvisually,andarethemostcommonfingerprintsinthecrimescene.Latentfingerprintsareoftenleftafterthefingersfirsttouchgrease,sweatordust,andthentouchacleansurface.Althoughthesefingerprintscannotbeseenwiththenakedeye,theycanbeprocessedbyspecialmethodsandusingsomespecialchemicalreagents.Revealtheselatentfingerprints.

Fyysinen menetelmä

Sormenjäljet ​​ovat imukykyisten materiaalien, kuten metallien, muovien, lasin, laattojen jne. pinnalla, fyysisiä menetelmiäyleensä käytetään. Sormenjälkiä tulee näkyviin.

(1)Puuterimenetelmä, valitse jauhe, jolla on suuri kontrastiväri, ja ripottele sitä täydellisten sormenjälkien poistamiseksi;

(2)Magneettinen jauhemenetelmä, käytä magneettiruuahiukkasiaAsaharjalla, pyyhkäise taaksepäin ja vielä kerran paljastaaksesi sormenjäljet.

(3)Lasermethod.Withthedevelopmentoflasertechnology,ourcountryuseslasertodisplayfingerprints.Thedisplaydeviceusesanargonionlaser.Laserscandisplayfingerprintsbecausethereisalwaysalayerofsweatandfattyacidsonthesurfaceofhumanfingers,whichleavesinconspicuousfingerprintsaftertouchingobjects;withlaserlight,sweat,fattyacids,etc.willproducecolorfluorescence,andthefingerprintswillbeclear..Useadedicatedfingerprintcameratotakeclearfingerprintphotos.Afterthephotoisenlarged,itbringsalotofconveniencetotheappraisalwork.

Kemiallinen menetelmä

Sormenjäljet ​​ovat imukykyisen hiukkasen, kuten paperin, korttien, nahan, puun jne. pinnalla, ne on käsiteltävä kemiallisesti ennen kuin ne voidaan paljastaa laboratoriossa.

Iodinefumigationmethod-theuseofiodinecrystalstoheattogeneratesteam,afteritreactswiththegreaseofthefingerprintresidue,yellow-brownfingerprintswillappear,whichmustbetakenimmediatelyorfixedbychemicalmethods;

Ninhydrinmethod-spraythereagentonthespecimen,andafterreactingwiththeaminoacidsinbodysecretions,itwillshowapurplefingerprint;

Silvernitratemethod-nitricacidAfterthesilversolutionreactswiththesodiumchlorideintheresidualsweat,itwillproduceblackfingerprintsinthesun;

Fluorescencereagentmethod—fluoresceinando-phthalaldehydequicklyinteractwiththeproteinorfingerprintresiduesTheactionofaminoacidsproduceshighlyfluorescentfingerprints.Thisreagentcanbeusedonthesurfaceofcoloredobjects.

Three-secondgluemethod-thecyanoacrylateisvaporized,andtheresidualsubstancesonthefingerprint,suchasaminoacidsandglucose,willreactwiththevaporizedglueandmakethefingerprintappear.

(1) Hengityksen tarkkailumenetelmä: Tarkkaile hengitystä sileän kohteen pinnalla;

(2)Visualobservationmethod:Observewithacertainlightandangle.Withthehelpofbacklighting,fingerprintscanoftenbedisplayed.Thisisbecausefingerprintsareoftenstainedwithdust,whichabsorbslightandappearsdark.

(3)Suurennuslasihavainnointimenetelmä:havainnoita tietyssä valossa ja suurennuslasilla;

(4)Ultraviolettihavainnointimenetelmä:tarkkaile ultraviolettilevyjen ominaisuuksien kanssa;

(5)Physicalandchemicalobservationmethod:Forpotentialfingerprintsthataredifficulttoobservewiththenakedeye,physicalandchemicaltreatmentsareneededtofindout.

(6)Cyanidegluemethod:firstprepareasolutionofcyanideglueandether,immersethefilterpaperofasuitablesizeinthesolution,takeitoutanddry,andcontactthefilterpaperwiththefingerprintfor5-60minutes.Thepartofthefingerprintclosetothepapervolatilizesduetotheeffectoftheglue,andthepatternappearsonthesurfaceofthefilterpaper.

Specialfingerprints

Peoplewithspecialdiseasesleave"specialfingerprints"atthescene,whicharemainlyseenincertaindiseasesthatcanchangethepatient'ssweat.Likediabetes,becausethesugarcontentinthesweatofthepatientincreases,ifalotofsweatleavesfingerprints,theremaybeaphenomenonofantsandbeesgatheredinsomenovelsorpuzzles.Also,asmentionedonTVsometimeago,somepeopleusedinferiorporcelainteacupstodrinkteaforalongtime,resultingincopperpoisoning,whichresultedinredsweats.Forpatientslikethis,iftheyleavefingerprints,theywillfindthatthefingerprintsarered.

InArgentina,usingfingerprintevidencetomakeawomanwhokilledhertwochildrenconfessedtoacrime,thisisthefirsttimethatmodernfingerprintinspectiontechnologyhasbeenadoptedbyacourt.

Withthedevelopmentofscienceandtechnology,fingerprintshavenewusesinmedicine.Somedoctorshavediscoveredthatcertaindiseasescanbedetectedbycheckingaperson'sfingerprintsandpalmprints.

Fingerprintshavebecomegoodfriendswithelectroniccomputers.

Manybusinessesalsousethecharacteristicsoffingerprintstodevelopsomehigh-techequipmenttoreflecttheconvenienceandsafetythatfingerprintsbringtolife,suchasfingerprintlocks,fingerprintaccesscontrol,fingerprintattendancemachines,fingerprintcollectionDevice,fingerprintsafe,networkfingerprintlogintechnologyandsoon.Accordingtothesurvey,manyhigh-endsmartcommunitiesinChinaareequippedwithfingerprintlocksandfingerprintaccesscontrol.Theearliestfingerprintsusedintheequipmentisthefingerprintattendancemachine.Inordertopreventthegenerationofcards,thecompany'spersonnelmanagershaveadoptedfingerprintattendancemachinesoneafteranother.Atthesametime,mycountry'sfirstnetworkfingerprintlogintechnologyproviderhaslaunchedabetaversion,whichisexpectedtosolvetheproblemofnetworkaccountsecurity.

Whatnewuseswillsmallfingerprintshaveinthefuture?Anewmazeisbeforeusagain,waitingforustoexploreandseek.

Animalfingerprints

Thestudyfoundthatinadditiontohumans,primatessuchasgorillas,chimpanzees,orangutansalsohaveskinpatternsonthehandsandfeet,andeventhearborealkoalaSkinpatternsarealsofoundonanimalsofitskind(Possumidae).Inaddition,spidermonkeysandcapuchinmonkeyslivinginSouthAmericahaveacurlytail,whichcandexterouslygraspobjects,andtheyalsohaveskinpatternsontheinsideoftheirtails.Itcanbeinferredfromthisthatitisalwayseasiertoformskinlinesontheskinwhereananimalisgrabbinganobject.

Tunnistamisen periaatteet

Sormenjälkien tunnistus

Readfingerprintimages,extractfeatures,savedataandcompare.Atthebeginning,theimageofthehumanfingerprintisreadbythefingerprintreadingdevice.Afterthefingerprintimageisobtained,theoriginalimagemustbepreliminarilyprocessedtomakeitclearer.Next,thefingerprintrecognitionsoftwareestablishesthedigitalrepresentationofthefingerprint-characteristicdata,aunidirectionalconversionthatcanconvertfromfingerprinttocharacteristicdatabutnotfromcharacteristicdatatofingerprint,andtwodifferentfingerprintswillnotproducethesameCharacteristicdata.

Somealgorithmscombinethenodeanddirectioninformationtogeneratemoredata,whichindicatestherelationshipbetweeneachnode,andsomealgorithmsalsoprocesstheentirefingerprintimage.Inshort,thesedata,usuallycalledtemplates,aresavedas1Krecords.Nomatterhowtheyarecomposed,thereisstillnostandardfortemplatesandnopublishedabstractalgorithms.Instead,eachmanufacturerdoesitsownthing.Finally,throughthemethodofcomputerfuzzycomparison,thetemplatesofthetwofingerprintsarecompared,andthedegreeofsimilaritybetweenthemiscalculated,andfinallythematchingresultofthetwofingerprintsisobtained.Fingerprintsareactuallymorecomplicated.

Unlikemanualprocessing,manybiometrictechnologycompaniesdonotdirectlystorefingerprintimages.Overtheyears,manydigitalalgorithmshavebeenproducedinvariouscompaniesandtheirresearchinstitutions(therelevantlawsoftheUnitedStatesbelievethatfingerprintimagesarepersonalprivacy,sofingerprintimagescannotbestoreddirectly).

Fingerprintrecognitionalgorithmsultimatelyboildowntofindingandcomparingfingerprintfeaturesonfingerprintimages.ThecharacteristicsoffingerprintsWedefinetwotypesofcharacteristicsoffingerprintstoverifyfingerprints:overallcharacteristicsandlocalcharacteristics.Generalfeaturesrefertothosefeaturesthatcanbedirectlyobservedbythehumaneye,including:basicpatternpatterns,loop,arch,andwhorl.Otherfingerprintpatternsarebasedonthesethreebasicpatterns.Relyingonthepatterntypetodistinguishfingerprintsisfarfromenough.Thisisonlyaroughclassification,butclassificationmakesitmoreconvenienttosearchforfingerprintsinlargedatabases.

Kuvioalue

(PatternArea)Thepatternareareferstotheareaonthefingerprintthatincludestheoverallcharacteristics,thatis,itcanbedistinguishedfromthepatternareathatthefingerprintbelongstoWhichtype.Somefingerprintrecognitionalgorithmsonlyusethedatainthepatternarea.Aetex'sfingerprintrecognitionalgorithmusestheobtainedcompletefingerprintinsteadofjustthepatternareaforanalysisandrecognition.

CorePoint(CorePoint)Ydinpiste sijaitsee sormenjälkikuvion etenevässä keskustassa. Sitä käytetään sormenjälkien lukemisen ja sormenjälkien täsmäytyksen viitepisteenä.

Triangularpoint(Delta)Thetriangularpointislocatedatthefirstbifurcationorbreakpointfromthecorepoint,orwherethetwostripedroadsconverge,isolatedpoints,orturningpoints,Orpointtothesesingularities.Thetriangularpointprovidesthestartingpointforcountingandtrackingfingerprintlines.

TypeLines(TypeLines)Thetypelinesarecrosslinesthatappearwherethelinessurroundingthepatternareabegintobeparallel.Thestylelinesareusuallyshortandinterrupted,butItsouterlinebegantoextendcontinuously.

Numberoffingerprints

(RidgeCount)referstothenumberoffingerprintsinthepatternarea.Whencalculatingthenumberoffingerprints,usuallyconnectthecorepointandthetrianglepointfirst,andthenumberofintersectionsofthislinewiththefingerprintlinecanberegardedasthenumberoffingerprints.LocalfeaturesLocalfeaturesrefertonodesonthefingerprint.Twofingerprintsoftenhavethesameoverallcharacteristics,buttheirlocalfeatures-nodes,cannotbeexactlythesame.Nodes(MinutiaPoints)Fingerprintlinesarenotcontinuous,smoothandstraight,butofteninterrupted,bifurcatedorDiscount.Thesebreakpoints,bifurcationpoints,andturningpointsarecalled"nodes."Itisthesenodesthatprovidefingerprintconfirmationnodecharacteristics

1. Luokittelu - Solmutyyppejä on useita, joista useimmat ovat päätepisteitä ja haarautumispisteitä

A.Endpoints(Ending)-astripedroadendshere.

B. Bifurkaatio-astriperoja jaettukaksi lisäviivaksi tässä.

C.RidgeDivergence-Kaksi rinnakkaista erillistä tässä.

D.DotorIsland(DotorIsland)-erityisen lyhyt linja,jotta siitä tulee piste.

E.Afterastripedroaded-jaettu kahdeksi,sulatetaan yhdeksi välittömästi,ja tällä tavalla muodostettua pientä rengasta kutsutaan kohdepisteeksi.

F.ShortRidge(ShortRidge)-kuvio, joka onlyhyt, mutta ei tule pisteeksi.

2.Suunta-niin voi osoittaa tiettyyn suuntaan.

3.Kaarevuus ---kuvaa nopeuttajossaraesuunta muuttuu.

4.Position(Position)-solmun sijaintia kuvaavat(x,y)koordinaatit,joka voi olla absoluuttinen tai suhteellinen kolmiopisteeseen tai ominaisuuspisteeseen.

Kuinka hankkia

Ensin optinen tunnistustekniikka

Theuseofopticaltechnologytocollectfingerprintsistheoldestandmostwidelyusedtechnology.Putyourfingerontheopticallens,andusetheprismtoprojectthefingeronthechargecoupleddevice(CCD)undertheilluminationofthebuilt-inlightsource,andthenformtheridges(thelineswithacertainwidthanddirectioninthefingerprintimage),whichareblackandvalleys.Theline(theconcavepartbetweenthelines)isawhitedigitizedmulti-grayfingerprintimagethatcanbeprocessedbythefingerprintdevicealgorithm.

Toinen,Lämpötilasensorintunnistustekniikka

Itsadvantageisthatfingerprintimagescanbeacquiredwithin0.1s,andthesensorhasthesmallestvolumeandarea,whichisusuallyTheso-calledslidingfingerprintreaderadoptsthistechnology.Thedisadvantageis:subjecttotemperaturelimitations,afteralongtime,thefingerandthechipareatthesametemperature.

3.Puolijohteiden piintunnistustekniikka (kapasitiivinen tekniikka)

SemiconductorcapacitancesensorisbasedonthecapacitancevalueformedbytheridgeandridgeofthefingerprintandthesemiconductorcapacitancesensingparticlesThesizeisdifferenttodeterminewhichpositionisthecrestandwhichpositionistheyu.Itsworkingprocessistopre-chargethecapacitivesensingparticlesoneachpixeltoacertainreferencevoltage.Whenthefingertouchesthefingerprintperformanceofthesemiconductorcapacitor,becausetheridgeisconvexandtheridgeisconcave,accordingtotherelationshipbetweenthecapacitancevalueandthedistance,differentcapacitancevalues​​willbeformedattheridgeandtheridge.Thenusethedischargecurrenttodischarge.Becausetheridgeandyuhavedifferentcapacitancevalues,theirdischargespeedsarealsodifferent.Thepixelsunderthecrest(highcapacitance)dischargemoreslowly,whilethepixelsundertheridge(lowcapacitance)dischargefaster.Dependingonthedischargerate,thepositionsoftheridgesandridgescanbedetectedtoformfingerprintimagedata.

Neljä.Ultraäänitekniikka

Ultraäänitekniikan käyttämä ultraäänitaajuus on1×10⁴Hz-1×10⁹Hz,energiaa hallitaan siinä määrin, että se ei vaurioitaihmiskehoa (sama voimakkuus kuin lääketieteellinen diagnoosi). hiekkalentokoneet,mutta sen keräysaika on huomattavasti pidempi kuin edellä mainitut kahdentyyppiset tuotteet,ja on kallis,eikä sitä voida käyttää elävien sormenjälkien tunnistamiseen.harvinainen.

Importantconcepts

AsanewITtechnologyfield,fingerprintrecognitiontechnologyhasmanynewconcepts.Understandingtheconceptoffingerprintidentificationtechnologyhelpstounderstandfingerprintidentificationtechnologyaccurately.

Identificationsystem

Afterthedevelopmentofthefingerprintidentificationsystemfrommanualidentificationtomachineidentification,itenterstheautomaticidentificationstage,whichiscalledtheautomaticfingerprintidentificationsystem(AFIS).Atypicalautomaticfingerprintidentificationsystemincludesafront-endsubsystemthatinteractswithpeople-automaticfingerprintacquisitionequipment,aback-endsubsystemthatcompletesfingerprintimageprocessingandfeaturevalueextraction,andadatabasesubsystemforfingerprintlibrarystorage.Whenthebackgroundsubsystemisusedinthefingerprintregistrationprocess,itcanbecalledthefingerprintregistrationsubsystem.Whenitisusedinthefingerprintidentificationprocess,itiscalledthefingerprintidentificationsubsystem.

Registrationmatching

Fingerprintregistrationisalsocalledfingerprintregistration.Thisistheprocessofextractingfingerprintfeaturevalues​​fromthefingerprintimage,formingafingerprintfeaturevaluetemplate,combiningitwiththeperson'sidentityinformation,andstoringitinthefingerprintidentificationsystem.Itisequivalenttoreportinganaccountforfingerprints.Therefore,whenregisteringfingerprints,itisnecessarytoensurethecorrectcorrespondencebetweenfingerprintsandidentityinformation.Inparticular,itisveryimportanttopreventimpostersandavoiderrorsintheassociationoffingerprintsandidentityinformationwhenthegovernment,associations,companiesandotherunitsperformfingerprintregistration.Therefore,inthistypeoffingerprintapplication,theprocessoffingerprintregistrationrequirestheparticipationofon-sitesupervisors.Itevencollectsthesupervisor’sfingerprintsintothesystemasacomponentoftheregistrant’sfingerprintfeaturevaluetemplatetoshowtheimportanceofresponsibilitiesandprovideabasisforfollow-upresponsibilityaudits.

Identificationandverification

Identificationandverificationisnotaprobleminthefieldoffingerprintrecognitionalgorithms,butaprobleminthefingerprintrecognitionsystem.Fingerprintrecognitionreferstomatchingfingerprintfeaturevalues​​in1:Nmode.Itistheprocessofidentifyingaspecificfingerprintfrommultiplefingerprinttemplates.Theresultis"Yes"or"No."Sometimesinformationabout"whois"isgiven.

Fingerprintverificationreferstomatchingfingerprintfeaturevalues​​in1:1mode.Itisaprocessofmatchingthefingerprintfeaturetemplatetobecomparedwithanotherfingerprintfeaturetemplatethatexistsinadvance.Theresultis"isitright".Either1:1modeor1:Nmodecanbeusedinasystem,whichdependsonthecharacteristicsandrequirementsoftheapplicationsystem.Sometimesyoucanalsoconvertthe1:Nmodetothe1:1modetoimprovethesystemsecurityandcomparisonspeedasrequiredbythebusinessmodel.

Edut:

1.Sormenjäljet ​​ovat eri ihmiskehon piirteitä, ja niiden monimutkaisuus on riittävä tarjoamaan riittävästi ominaisuuksia tunnistamiseen.

2.Jos haluat lisätä luotettavuutta, sinun tarvitsee vain rekisteröidä enemmän sormenjälkiä ja tunnistaa useampi sormenjälki, jopa kymmenen, ja kaikki sormenjäljet ​​eivät ole samat.

3.Sormenjälkien skannaus on nopeaa ja erittäin kätevää.

4.Kun käyttäjä lukee sormenjälkeä, käyttäjän on kosketettavasormea ​​ja sormenjälkien tunnistuspäätä suoraan.

5.Yhteystiedot ovat luotettavin tapa lukea ihmisbiologiset ominaisuudet.

6.Sormenjälkien sieppauspää voidaan pienentää pienemmäksi, ja hinta on alhaisempi.

Haitat:

1.Joillakin ihmisillä tai tietyillä ryhmillä on muutama sormenjälkiominaisuus, ja kuva on vaikeaa.

2.Aiemmin sormenjälkien käyttö rikosrekisterissä sai ihmiset pelkäämään "sormenjälkien tallentamista".

3.Infact,thefingerprintidentificationtechnologycannotstoreanydatacontainingthefingerprintimage,butonlystoretheencryptedfingerprintcharacteristicdataobtainedfromthefingerprint.

4.Aina kun sormenjälkiä käytetään, käyttäjän sormenjälki jää sormenjälkien sieppauspäähän, ja näitä sormenjälkiä voidaan käyttää sormenjälkien kopioimiseen.

FRRandFAR

FRR(FalseRejectionRate)andFAR(FalseAcceptanceRate)arethetwomainparametersusedtoevaluatetheperformanceoffingerprintrecognitionalgorithms.FRRandFARaresometimesusedtoevaluatetheperformanceofafingerprintrecognitionsystem,butthisisnotappropriate.Inadditiontotheperformanceofthefingerprintidentificationsystembeingaffectedbythefingerprintalgorithm,theimpactoftheperformanceofthefingerprintcollectiondeviceonFRRandFARcannotbeignored.

FRRiscommonlycalledfalserejectionrate,andthestandardnameisFNMR(FalseNon-MatchRate,mismatchrate).Itcanbeeasilyunderstoodastheprobabilityof"takingfingerprintsthatshouldbesuccessfullymatchedwitheachotherasfingerprintsthatcannotbematched".Theperformancemeasurementofthefingerprintalgorithmismeasuredundertheconditionofagivenfingerprintlibrary.ThefingerprintlibraryusedformeasurementisgenerallygivenbytheorganizerofFVC(InternationalFingerprintIdentificationAlgorithmCompetition).WhenFVCperformsthefingerprintrecognitionalgorithmperformancetest,thereisnoexternalfingerprintinput,anditusesastandardfingerprintimagelibrarytotest.Therefore,FNMRisatestvalueobtainedwithoutconnectingafingerprintcollectiondevice.Theotherparametersinthissectionarealsoderivedunderthispremise.

Oletetaan, että sormenjälkikirjastossa on 100 sormea, joilla on eri ID F₁, P₁- F₂, P₁-F₃. FNMR viittaa kolmen sormenjäljen vertailuun sormenjälkitietokannassa, eli P₁-F₁jaP₁-F₂, P₁-F₁ja P₁ -F₃Ottelu,P₁-F₂ottelu P₁-F₃ ,P₁-F₂vastaa P₁-F₁, P₁- F₃ vastaa P₁-F₁, P₁-F3 matchesP₁-F2 ,Tietoja on kuusi.Tee 6tyyppisiä tulitikkuja kaikille 100 sormelle, yhteensä 6 × 100 = 600 ottelua. Teoriassa 600 tulitikkua voidaan sovittaa oikein, ja yhteensovituksen onnistumisaste on 100%. lariteetti.Oletetaan, että asetamme onnistuneen vastaavuuden samankaltaisuuden>90%:iin, eli kun samankaltaisuus on suurempi kuin 90%,se tarkoittaa, että vastaavuus ononnistui. 600 kertaa osoittaa, kuinka monta kertaa ei ole onnistunut ottelu, joka on 600-570 = 30 kertaa. Vastaavuuden epäonnistumisprosentti on 30/600 = 5 %.

Forthefingerprintrecognitionalgorithm,whenthefingerprintdatabaseisconfirmed,thematchingfailurerateFNMRiscertain.Whenthefingerprintlibrarychanges,itsFNMRwillalsochange.Therefore,internationally,thefingerprintlibrarypublishedbyFVCisusedasaunifiedtestlibrary,andtheFNMRresultstestedinthetestlibraryareusedasastandardreferenceformeasuringtheperformanceoffingerprintalgorithms.

FARisgenerallycalledthefalserecognitionrate,anditsstandardnameisFMR(FalseMatchRate).FMRisthemostimportantparameterusedtoevaluatetheperformanceoffingerprintrecognitionalgorithms.Itcanbeeasilyunderstoodastheprobabilityof"takingfingerprintsthatshouldnotbematchedasmatchedfingerprints".

Alsotakethefingerprintlibraryinthepreviousparagraphasanexample.Matcheachfingerprintinthelibrarywithallotherfingerprintsexceptyourself.Thetotalnumberofmatchesis300×(300-1)=89700times.Intheory,thenumberofsuccessfulmatchesis6×100=600times,andthenumberoffailedmatchesshouldbe89700-600=89100times.Supposethatduetotheperformanceofthefingerprintalgorithm,thematchthatshouldhavefailedisjudgedasasuccessfulmatch,ifitisassumedthatthenumberofsucherrorsis100times.ThefalseacceptancerateFARis100/89100=0.11%.Thenumberofmatchingfailuresvariesduetothestrictnessofthesimilarconditions.Whenthefilterconditionthatmatchessuccessfully,thatis,thethresholdvalueincreases,theFARwilldecrease.

FARisalsorelatedtofingerprintlibrary.IntheFVCcompetition,thereare4fingerprintlibrariesfortesting,andtheaverageistaken.Oneofthefingerprintlibrariesisartificiallygeneratedtoeliminatetheeffectofdifferentfingerprintimagequalitycausedbydifferentcollectiondevicesontheperformanceofthealgorithm.

Inthesamefingerprintlibrary,forthesamealgorithm,athresholdneedstobesetasacriterionforjudgingsimilarity.Whenthesimilarityisgreaterthanthisthreshold,itmeansthematchissuccessful,otherwiseitmeansthematchfails.FNMRincreaseswiththeincreaseofthethreshold,thatis,thehigherthethresholdforjudgingsimilarity,thegreatertheprobabilitythatatruefingerprintisjudgedtobefalse.Conversely,theFMRdecreaseswiththeincreaseofthethreshold,thatis,asthethresholdforjudgingthesimilarityishigher,theprobabilityofjudgingthefakefingerprintastruewillbesmaller.FARisinverselyproportionaltoFRR.AccordingtothetestresultsoftheFVCcompetitionin2004,whentheFMRis1/1000,theFNMRisabout5/100.Thatis,inthefingerprintlibraryof100fingers,if1000matchesareperformed,amatchingerrormayoccur,thatis,anacknowledgment.After100matchesareperformed,theremaybe5matchfailures,thatis,theyarenotrecognized.

EER

EER(EqualErrorRate)meansequalerrorrate.Thisparameterisgenerallynotusedinordinaryoccasions.EERismainlyusedtoevaluatetheoverallperformanceoffingerprintalgorithms.Thatis,thetwoparametersofFARandFRRareunifiedintooneparametertomeasuretheoverallperformanceofthefingerprintalgorithm.FARandFRRaretwoparametersofthesamealgorithmsystem.Puttheminthesamecoordinate.FARdecreaseswiththeincreaseofthethreshold,andFRRincreaseswiththeincreaseofthethreshold.Sotheymusthaveintersections.ThispointisthepointatwhichFARandFRRareequivalentunderacertainthreshold.Itiscustomarytousethisvaluetomeasuretheoverallperformanceofthealgorithm.Forabetterfingerprintalgorithm,itishopedthatbothFARandFRRshouldbeassmallaspossibleunderthesamethreshold.

TranslateboththeFARandFRRcurvesdownward.Atthesametime,theintersectionpointERRalsoshiftsdownward.ThesmallertheEERvalue,thehighertheoverallperformanceofthealgorithm.

BecausethecorrespondingthresholdswhenFRRandFARintersectareverysmall,thatistosay,thesimilaritythresholdatthistimeislessthan30%.Thethresholdinactualuseisatleast80%,sotheEERvalueisnotusedinpopularoccasionstodescribetheperformanceofthefingerprintalgorithm,butonlyusedincompetitionrankings.

FRRisactuallyanimportantindicatorofsystemeaseofuse.SinceFRRandFARarecontradictorytoeachother,thismakesitnecessarytoweigheaseofuseandsafetyinthedesignofapplicationsystems.Aneffectivemethodistocomparetwoormorefingerprints,therebygreatlyimprovingsystemsecuritywithoutlosingeaseofuse.

Disapprovalrate

Thedisapprovalrateisgenerallyseldomused.Infingerprintrecognitionterms,itisarelativelyvagueterm.IntheWorldFingerprintAlgorithmCompetition,thereisaparametercalledtherejectionrate,sometimescalledtherejectionrate,whichisusedtomeasurethedegreeofpickinessofthefingerprintrecognitionalgorithmonthequalityofthefingerprintimage,usingREJENROLL.Express.Inagivennumberoffingerprints,suchas100fingerprintimages,fingerprintsthatcanbesuccessfullyregisteredorcalledfilecreation,ifitis99,thenREJENROLL=1%.ForthestandardfingerprintlibrarygivenbytheFVCcompetition,mostfingerprintalgorithmscanbesuccessfullyfiled,thatis,REJENROLLis0.00%.

Onanotheroccasion,therejectionrateisusuallyinterpretedastheprobabilitythatthefingerprintidentificationsystem(includingfingerprintcollectionequipment)willnotacceptfingerprintregistration.Inthiscase,thefactorsthatrejectregistrationaremoreaffectedbytheimagingcapabilitiesofthefingerprintcollectiondevice,inadditiontothealgorithmitself.Thebetterthequalityofthefingerprintimageoutputbythefingerprintcollectiondevice,thelowertherejectionrateofthefingerprintidentificationsystem,andthelowerthequalityofthefingerprintimageoutputbythefingerprintcollectiondevice,thehighertherejectionrate.

Time

Registrationtimeisanotherindicatorusedtomeasuretheperformanceoffingerprintalgorithm.Itreferstothetimefromtheinputofthefingerprintimagetothesuccessfulestablishmentofthefingerprintfile(successfulregistration).AccordingtotheresultsoftheFVCcompetition,thegeneralfingerprintalgorithmregistrationtimeiswithin0.5seconds,whichisalsooneofthequalificationsproposedbyFVCtoparticipateintheLIGHTgroupcompetitionalgorithm.

Thematchingtimeissometimescalledthecomparisonspeed,whichisusedtoindicatethetimerequiredforthefingerprintrecognitionalgorithmtocompleteamatch.Itisthetimefromthefingerprintimageinputtotheoutputofthematchingresult.Thematchingtimeofmostalgorithmsparticipatinginthealgorithmcompetitioniswithin0.3seconds.ThisparameterandtheminimumregistrationtimeconstitutetheentryconditionsfortheLIGHTgroup.

Becausethesetimesareallaffectedbythequalityofthefingerprintimagetobetested,theaveragevalueofmultiplefingerprintlibrariesisgenerallytaken,andtheaverageregistrationtimeandaveragematchingtimearegenerallyusedasthebasisformeasurement.

Technologyintroduction

Theresearchfrom"fingerprint"to"fingerprinttechnique"hasgonethroughalongprocess.Aftertheformationoffingerprinttechnology,ithasundergonethedevelopmentandtransformationfrommanualidentificationtechnologytoautomaticidentificationtechnology.Withthedevelopmentofcomputerimageprocessingtechnologyandinformationtechnology,fingerprintrecognitiontechnologyhasgraduallyenteredthefieldofITtechnology,combinedwithmanycomputerinformationsystems,andwidelyused.

Expertsreminded

ProfessorsfromtheNationalInstituteofInformaticsinJapanremindednetizensthatifyouposeaVsignwhentakingpictures,yourfingerprintsarelikelytobestolen.Inadditiontofingerprints,facialandirisrecognitionhasalsobeenappliedtomobilephoneauthentication.Someadministrativeagenciesandenterprisesarealsousingthisinformationforattendancemanagement.Previously,inordertoobtainpersonalbiometricinformation,itwasnecessarytoapproachthepersonforshooting.However,recentlysomebiologicalinformationhasbeencirculatedontheInternet,whichgreatlyreducesthethresholdforcriminals.