www.fingerprints.com1
Evaluation_WetFingers.doc
1SensorEvaluation–WetFingerSensitivity:FPC1011Cvs.FPC1011F
WewanttostudythedifferencesbetweenFPC1011CandFPC1011Fwithrespecttowetfingerprints.
Foraslightlywetfinger–i.e.dippedinwater,andquicklydriedonapapertowel,beforeplacedonthe
sensorwegetnormalfingerprintsforbothsensortypes:
Figure1:FPC1011Cvs.FPC1011Fwithaslightlywetfinger.
Wenotethatthegeneralimagequalityisgood,andthattheFPC1011Fimageissomewhatdarkerthan
theFPC1011Cimage.Thisisnormal,andduetodifferencesincoatingmaterial.
Iflargeamountofwaterisappliedtothefinger(i.e.dippedinwaterandnotwipedoffwithapaper
towel),theimagedeteriorates(simplybecausethefingeritselfisverywet,sothatwaterfillsthe
fingerprintvalleys,effectivelyremovingthepatternsinthefinger).
Anumberoftestswereperformedwherelargeamountsofwaterwereappliedtoafingerandthento
oneoftwosensortypes.Notethatwedidnotseeabuildupofwateroverasequenceofimages.The
amountofblurrinessintheimagesisdirectlydependentontheamountofwateronthefingerand/or
sensor.Theimagesonthenextpagewerecapturedduringtheseexperiments.
www.fingerprints.com2
Evaluation_WetFingers.doc
Figure2:ImagesfromanFPC1011Cforverywetfingers.Morewaterisaddedforeachimage.
Figure3:ImagesfromanFPC1011Fforverywetfingers.Morewaterisaddedforeachimage.
Itisimportanttonotethatthewaterapplicationcannotbeperformedidenticallyforthetwodifferent
sensortypes.Sinceasmallvariationofwatercanmakeabigdifferenceinimagequality,itisdifficult
tomakeafaircomparisonbetweenthetwosensortypeswithahumanfinger.
Itisourexperience,bothfromearlierexperimentsandinthistest,thattheFPC1011CandFPC1011F
behavessimilarlyforallfingertypes,drytosweatytoverywetfingers.
FPC1011FhasadifferentcoatingthatgivesanimagethathasaslightlyhighercontrastthanFPC1011C
(foranyfinger).Thismeansthattheimagecontainsmoreinformationandisbetterinsomesense.Itis
notnecessaryforgeneralusage,butitispossibletoadjusttheparametersforimagecaptureon
FPC1011FsothatitgeneratesimageswithacontrastidenticaltotheFPC1011Csensor(withdefault
parameters).SettingADCRef=3andDrivC=100onFPC1011Fwilldothat.(DefaultisADCRef=2,
DrivC=127.)
|
|
