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.
Криминалистика на пръстови отпечатъци, включително търсене и откриване на пръстови отпечатъци. Обхватът на търсенето на пръстови отпечатъци: (1) центърът за престъпна дейност; (2) важният индекс на местопрестъплението и околностите му; (3) елементите, които престъпниците може да са докоснали; (4) различните смъртоносни оръжия и предмети, оставени от престъпника на местопроизшествието.
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.
Генетични проблеми
Може ли пръстовите отпечатъци да са наследени?
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."
Как се формират пръстовите отпечатъци?
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.
Метод на наблюдение
Според различните наследени методи, пръстовите отпечатъци могат да бъдат разделени на три категории:
Първата категория е патентният отпечатък, който е целевият отпечатък. Линиите могат да се видят с зрение. Например, ръчно потопена боя, кръв, инкандо други елементи се прехвърлят, обикновено отпечатани върху картата с пръстов отпечатък, за да станат основни данни;
Thesecondtypeisplasticprint,whichreferstothesoftSubstances,suchasfingerprintsimprintedoncandlesandclaybyhandcontact;
Thethirdtypeislatentprint,whichisafingerprintthatistransferredbythebody’snaturalsecretionssuchassweat.Thelinesarenoteasytofindvisually,andarethemostcommonfingerprintsinthecrimescene.Latentfingerprintsareoftenleftafterthefingersfirsttouchgrease,sweatordust,andthentouchacleansurface.Althoughthesefingerprintscannotbeseenwiththenakedeye,theycanbeprocessedbyspecialmethodsandusingsomespecialchemicalreagents.Revealtheselatentfingerprints.
Физически метод
Ако отпечатъците от пръсти са отляво върху повърхността на неабсорбиращи материали като метали, пластмаси, стъкло, плочки и др., обикновено могат да се използват физически методи. Появяват се отпечатъци от пръсти.
(1)Метод на прах, изберете прах с голям цветен контраст и го поръсете, за да извлечете пълни пръстови отпечатъци;
(2)Метод с магнитен прах, използвайте фини частици железен прах с магнити Като четка, плъзнете назад и напред, за да разкриете отпечатъци от пръсти.
(3)Lasermethod.Withthedevelopmentoflasertechnology,ourcountryuseslasertodisplayfingerprints.Thedisplaydeviceusesanargonionlaser.Laserscandisplayfingerprintsbecausethereisalwaysalayerofsweatandfattyacidsonthesurfaceofhumanfingers,whichleavesinconspicuousfingerprintsaftertouchingobjects;withlaserlight,sweat,fattyacids,etc.willproducecolorfluorescence,andthefingerprintswillbeclear..Useadedicatedfingerprintcameratotakeclearfingerprintphotos.Afterthephotoisenlarged,itbringsalotofconveniencetotheappraisalwork.
Химичен метод
Ако отпечатъците от пръсти са отляво върху повърхността на абсорбираща мита, освен като хартия, карти, кожа, дърво и т.н., те трябва да бъдат химически обработени, преди да бъдат показани в лабораторията.
Iodinefumigationmethod-theuseofiodinecrystalstoheattogeneratesteam,afteritreactswiththegreaseofthefingerprintresidue,yellow-brownfingerprintswillappear,whichmustbetakenimmediatelyorfixedbychemicalmethods;
Ninhydrinmethod-spraythereagentonthespecimen,andafterreactingwiththeaminoacidsinbodysecretions,itwillshowapurplefingerprint;
Silvernitratemethod-nitricacidAfterthesilversolutionreactswiththesodiumchlorideintheresidualsweat,itwillproduceblackfingerprintsinthesun;
Fluorescencereagentmethod—fluoresceinando-phthalaldehydequicklyinteractwiththeproteinorfingerprintresiduesTheactionofaminoacidsproduceshighlyfluorescentfingerprints.Thisreagentcanbeusedonthesurfaceofcoloredobjects.
Three-secondgluemethod-thecyanoacrylateisvaporized,andtheresidualsubstancesonthefingerprint,suchasaminoacidsandglucose,willreactwiththevaporizedglueandmakethefingerprintappear.
(1) Метод за наблюдение на дишането: Наблюдавайте дишането върху повърхността на гладък обект;
(2)Visualobservationmethod:Observewithacertainlightandangle.Withthehelpofbacklighting,fingerprintscanoftenbedisplayed.Thisisbecausefingerprintsareoftenstainedwithdust,whichabsorbslightandappearsdark.
(3) Метод на наблюдение с лупа: наблюдавайте под определена светлина и ъгъл с лупа;
(4) Метод на ултравиолетово наблюдение: наблюдавайте с характеристиките на травиолетови лъчи;
(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.
Принципи на разпознаване
Разпознаване на пръстови отпечатъци
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.
PatternArea
(PatternArea)Thepatternareareferstotheareaonthefingerprintthatincludestheoverallcharacteristics,thatis,itcanbedistinguishedfromthepatternareathatthefingerprintbelongstoWhichtype.Somefingerprintrecognitionalgorithmsonlyusethedatainthepatternarea.Aetex'sfingerprintrecognitionalgorithmusestheobtainedcompletefingerprintinsteadofjustthepatternareaforanalysisandrecognition.
Основна точка(Основна точка)Основната точка е разположена в прогресивния център на модела на пръстовия отпечатък. Използва се като отправна точка за четене на пръстов отпечатък и съпоставяне на пръстов отпечатък.
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. Класификация - Има няколко типа възли, като най-типичните са крайни точки и точки на бифуркация
A.Крайни точки(Край)-astripedroadendтук.
Б. Бифуркация-astriperoaсе разделя на две или повече линии тук.
C.Ридж Дивергенция-Две паралелни линии са разделени тук.
D.DotorIsland(DotorIsland)-особено кратка линия, така че става точка.
E.Заграждение-След като ивицата е разделена на две, незабавно се обединява в една и като малък пръстен, оформен по този начин, се нарича точка на спиране.
F.ShortRidge(ShortRidge)-модел,който е къс тон в края, но не става точка.
2.Orientation-thenodecan faceacertaindirection.
3.Кривина ---опишете скоростта, при която посоката на зърното се променя.
4.Позиция(Позиция)-позицията на възела се описва от (x,y)координати,които могат да бъдат абсолютни или относителни спрямо триъгълна точка или точка на характеристика.
Как да получите
Първо, технология за оптично разпознаване
Theuseofopticaltechnologytocollectfingerprintsistheoldestandmostwidelyusedtechnology.Putyourfingerontheopticallens,andusetheprismtoprojectthefingeronthechargecoupleddevice(CCD)undertheilluminationofthebuilt-inlightsource,andthenformtheridges(thelineswithacertainwidthanddirectioninthefingerprintimage),whichareblackandvalleys.Theline(theconcavepartbetweenthelines)isawhitedigitizedmulti-grayfingerprintimagethatcanbeprocessedbythefingerprintdevicealgorithm.
Второ,технология за разпознаване на температурен сензор
Itsadvantageisthatfingerprintimagescanbeacquiredwithin0.1s,andthesensorhasthesmallestvolumeandarea,whichisusuallyTheso-calledslidingfingerprintreaderadoptsthistechnology.Thedisadvantageis:subjecttotemperaturelimitations,afteralongtime,thefingerandthechipareatthesametemperature.
3.Полупроводникова силициева сензорна технология (капацитивна технология)
SemiconductorcapacitancesensorisbasedonthecapacitancevalueformedbytheridgeandridgeofthefingerprintandthesemiconductorcapacitancesensingparticlesThesizeisdifferenttodeterminewhichpositionisthecrestandwhichpositionistheyu.Itsworkingprocessistopre-chargethecapacitivesensingparticlesoneachpixeltoacertainreferencevoltage.Whenthefingertouchesthefingerprintperformanceofthesemiconductorcapacitor,becausetheridgeisconvexandtheridgeisconcave,accordingtotherelationshipbetweenthecapacitancevalueandthedistance,differentcapacitancevalueswillbeformedattheridgeandtheridge.Thenusethedischargecurrenttodischarge.Becausetheridgeandyuhavedifferentcapacitancevalues,theirdischargespeedsarealsodifferent.Thepixelsunderthecrest(highcapacitance)dischargemoreslowly,whilethepixelsundertheridge(lowcapacitance)dischargefaster.Dependingonthedischargerate,thepositionsoftheridgesandridgescanbedetectedtoformfingerprintimagedata.
Четири.Ултразвукова технология
Ултразвуковата честота, използвана от ултразвуковата технология, е 1×104Hz-1×109Hz, енергията се контролира до такава степен, че да не уврежда човешкото тяло (същата интензивност като медицинската диагноза). Продуктите с ултразвукова технология могат да постигнат най-добрата точност. Изисква по-малко чистота предлагане и самолети, но времето за събиране ще бъде значително по-дълго от гореспоменатите два вида продукти и е скъпо и не може да се използва за идентификация с пръстов отпечатък на живо.
Importantconcepts
AsanewITtechnologyfield,fingerprintrecognitiontechnologyhasmanynewconcepts.Understandingtheconceptoffingerprintidentificationtechnologyhelpstounderstandfingerprintidentificationtechnologyaccurately.
Identificationsystem
Afterthedevelopmentofthefingerprintidentificationsystemfrommanualidentificationtomachineidentification,itenterstheautomaticidentificationstage,whichiscalledtheautomaticfingerprintidentificationsystem(AFIS).Atypicalautomaticfingerprintidentificationsystemincludesafront-endsubsystemthatinteractswithpeople-automaticfingerprintacquisitionequipment,aback-endsubsystemthatcompletesfingerprintimageprocessingandfeaturevalueextraction,andadatabasesubsystemforfingerprintlibrarystorage.Whenthebackgroundsubsystemisusedinthefingerprintregistrationprocess,itcanbecalledthefingerprintregistrationsubsystem.Whenitisusedinthefingerprintidentificationprocess,itiscalledthefingerprintidentificationsubsystem.
Registrationmatching
Fingerprintregistrationisalsocalledfingerprintregistration.Thisistheprocessofextractingfingerprintfeaturevaluesfromthefingerprintimage,formingafingerprintfeaturevaluetemplate,combiningitwiththeperson'sidentityinformation,andstoringitinthefingerprintidentificationsystem.Itisequivalenttoreportinganaccountforfingerprints.Therefore,whenregisteringfingerprints,itisnecessarytoensurethecorrectcorrespondencebetweenfingerprintsandidentityinformation.Inparticular,itisveryimportanttopreventimpostersandavoiderrorsintheassociationoffingerprintsandidentityinformationwhenthegovernment,associations,companiesandotherunitsperformfingerprintregistration.Therefore,inthistypeoffingerprintapplication,theprocessoffingerprintregistrationrequirestheparticipationofon-sitesupervisors.Itevencollectsthesupervisor’sfingerprintsintothesystemasacomponentoftheregistrant’sfingerprintfeaturevaluetemplatetoshowtheimportanceofresponsibilitiesandprovideabasisforfollow-upresponsibilityaudits.
Identificationandverification
Identificationandverificationisnotaprobleminthefieldoffingerprintrecognitionalgorithms,butaprobleminthefingerprintrecognitionsystem.Fingerprintrecognitionreferstomatchingfingerprintfeaturevaluesin1:Nmode.Itistheprocessofidentifyingaspecificfingerprintfrommultiplefingerprinttemplates.Theresultis"Yes"or"No."Sometimesinformationabout"whois"isgiven.
Fingerprintverificationreferstomatchingfingerprintfeaturevaluesin1:1mode.Itisaprocessofmatchingthefingerprintfeaturetemplatetobecomparedwithanotherfingerprintfeaturetemplatethatexistsinadvance.Theresultis"isitright".Either1:1modeor1:Nmodecanbeusedinasystem,whichdependsonthecharacteristicsandrequirementsoftheapplicationsystem.Sometimesyoucanalsoconvertthe1:Nmodetothe1:1modetoimprovethesystemsecurityandcomparisonspeedasrequiredbythebusinessmodel.
Предимства:
1.Пръстовите отпечатъци са различна характеристика на човешкото тяло и тяхната сложност е достатъчна, за да осигури достатъчно функции за идентификация.
2.Ако искате да увеличите надеждността, трябва само да регистрирате повече пръстови отпечатъци и да идентифицирате повече пръсти, до десет, и всеки пръстов отпечатък не е един и същ.
3.Сканирането на пръстови отпечатъци е бързо и много удобно за използване.
4.Когато чете пръстов отпечатък, потребителят трябва да докосне пръста си и да получи пръстовия отпечатък директно с главата.
5.Свържете се с най-надеждния начин за разчитане на човешките биологични характеристики.
6.Главата за улавяне на пръстови отпечатъци може да бъде по-миниатюризирана и цената ще бъде по-ниска.
Недостатъци:
1.Някои хора или определени групи имат малко функции на пръстови отпечатъци и по-трудно за изобразяване.
2.В миналото използването на пръстови отпечатъци в криминални досиета е карало някои хора да се страхуват от „записване на пръстови отпечатъци“.
3.Infact,thefingerprintidentificationtechnologycannotstoreanydatacontainingthefingerprintimage,butonlystoretheencryptedfingerprintcharacteristicdataobtainedfromthefingerprint.
4.Всеки път, когато се използва пръстов отпечатък, пръстовият отпечатък на потребителя ще остане върху главата за улавяне на пръстовия отпечатък и следите от пръстов отпечатък могат да се използват за копиране на пръстови отпечатъци.
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.
Ако приемем, че има 100 пръста с различни идентификатори в библиотеката за пръстови отпечатъци и всеки пръст е регистриран с 3 пръстови отпечатъка, има общо 300 пръстови отпечатъка в библиотеката за пръстови отпечатъци. Ако приемем, че P1представлява ID на пръстовия отпечатък1, регистрираният пръстов отпечатък три пъти е P1-F< sub>1,P1- F2,P1-F3.FNMR се отнася за сравняване на 3 пръстови отпечатъка от същия пръст в базата данни за пръстови отпечатъци по двойка, а именно P1-F1иP1-F2съответства,P1-F1иP1 -F3съвпадение,P1-F2съвпадение P1-F3 ,P1-F2съвпада с P1-F1,P1- F3съвпада с P1-F1, P1-F3 съвпада с P1-F2 ,Има 6 метода за съпоставяне. Направете 6 вида съвпадения за всичките 100 пръста вътре, общо 6×100=600 съвпадения. На теория 600 съвпадения могат да бъдат съпоставени правилно и процентът на успеваемост на съвпадението е 100%. Всъщност, тъй като изображението на отпечатъка от три пръста на един и същ пръст не може да бъде абсолютно еднакво, има проблем при съпоставянето на подобни Да предположим, че сме задали приликата на успешното съвпадение на>90%, тоест, когато приликата е по-голяма от 90%, това означава, че съвпадението е успешно. Тогава откриваме колко пъти приликата е над 90% от 600 съвпадения. Тази стойност представя броя успешни съвпадения, които се приемат за 570. Останалото 600 пъти посочват броя пъти, когато няма успешно съвпадение, което е 600-570= 30 пъти. Степента на неуспех при съвпадение е 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.