U3.6 Fingerprint

U3.6 Fingerprint

Uses ridges on the skin, Ridges = lines. Valleys = Spaces between
Major and Minor features
1. 3 Major Features
  1. Arch, Loop, Whorl
    1. Major features used to classify fingerprints so they are more easily searchable
      1. Only look in or compare to Arch records etc.
2. Minor features = Minutiae
  1. Minutiae are the distinguishing features
    1. Ridge endings and burifications in fingerprint pattern
    2. Most algorithms are based on munutiae
Fingerprint processing involves several steps
1. Image is captured by sensor
  1. noise is reduced IE:dirt, dryness, scars. definition against the valleys is enhanced
    1. Image is binarised = reduced to black or white
      1. 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
1. Mature technology, lots of development, investment and research. Takes up 2/3 of Biometric Market
2. Easy to use, non intrusive
3. High levels of accuracy, low error rates, low FMR, low FNMR
4. Long term stability of FP over a lifetime
5. Ability to enrol multiple fingers
Disadvantages
1. Inability to Enrol some users IE elderly, manual workers, thin fingerprints (Asian)
2. Accuracy affected by skin condition
3. Association with forensic applications
  1. Privacy issues with users
Sensors
1. Optical
  1. Oldest / most mature
    1. Finger placed on glass and Image taken using optical device (camera)
      1. Not much further development
2. Ultrasound
  1. Uses ultrasound for capturing images
    1. Un affected by dirt grease moisture etc
      1. Better than optical but can only operate between 10c -32 c. Mainly used indoors
3. Chip Based
  1. Capacitive
    1. Most widely used chip based sensor
  2. E-field
    1. reads sub surface of skin, not affected by skin surface issues
  3. Direct Optical Scanning
    1. Robust fibre optic sensor
  4. Thermal
    1. Uses the fingers natural heat, no optic or light source required

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	Created by Craig Parker over 10 years ago