Zusammenfassung der Ressource
U3.6 Fingerprint
- Uses ridges on the skin, Ridges =
lines. Valleys = Spaces between
- Major and Minor features
- 3 Major Features
- Arch, Loop, Whorl
- Major features used to classify fingerprints
so they are more easily searchable
- Only look in or compare to Arch records etc.
- Minor features = Minutiae
- Minutiae are the
distinguishing features
- Ridge endings and burifications
in fingerprint pattern
- Most algorithms are based
on munutiae
- Fingerprint processing
involves several steps
- Image is captured by sensor
- noise is reduced IE:dirt, dryness, scars.
definition against the valleys is enhanced
- Image is binarised =
reduced to black or white
- Thinning is performed = reduction of ridges
down to a single pixel to help detect ridge
endings and burifications in the pattern
- Ridges are traced,endings are found at
termination points of the ridges and
burifications are found at the junction of lines
- Extracted features consists of the sequence of bits
representing for each minutuae, type of minutiae
(ridge or burification) its location and direction
- Matching is done by comparing extracted
features against the reference template
- Like comparing the shape of 2 graphs, if the graphs are similar
enough according to the tolerance threshold the result is a match
- Some FP recognition can be done without
the minutiae instead using pattern matching
- Advantages
- Mature technology, lots of
development, investment and research.
Takes up 2/3 of Biometric Market
- Easy to use, non intrusive
- High levels of accuracy, low
error rates, low FMR, low FNMR
- Long term stability of
FP over a lifetime
- Ability to enrol
multiple fingers
- Disadvantages
- Inability to Enrol some users IE elderly,
manual workers, thin fingerprints (Asian)
- Accuracy affected
by skin condition
- Association with
forensic applications
- Privacy issues with users
- Sensors
- Optical
- Oldest / most mature
- Finger placed on glass and Image
taken using optical device (camera)
- Not much further development
- Ultrasound
- Uses ultrasound for capturing images
- Un affected by dirt grease moisture etc
- Better than optical but can only operate
between 10c -32 c. Mainly used indoors
- Chip Based
- Capacitive
- Most widely used
chip based sensor
- E-field
- reads sub surface of
skin, not affected by
skin surface issues
- Direct Optical
Scanning
- Robust fibre optic
sensor
- Thermal
- Uses the fingers natural heat,
no optic or light source required