Fingerprint Analysis

1

• Fingerprint Analysis
• (part 1)
• Pavel Mrázek

2
What is fingerprint

• Ridges, valleys
• Singular points
• Core
• Delta
• Orientation field
• Ridge frequency

3
Fingerprint classes

4
Small scale Minutia

• 150 types in theory
• 7 used by human experts
• 2 types for the machine
• Ending
• Bifurcation

5
Minutia examples

6
Sensing

• Traditional (off line) rolled ink impression
  paper scan
• Plus big area
• Minuses
• Inconvenient
• Distortion
• Too much/little ink

7
Sensing

• Optical sensors

8
Sensing

• Optical sensors

• Good large area possible, good image quality,
  contactless scanning available
• Bad size

9
Sensing

• Silicon sensors
• Capacitive
• Electric field
• Thermal

10
Sensing

• Silicon sensors

• Good image quality, small form factor
• Price proportional to size

11
Sensing

• Silicon sensors
• Area
• Swipe

12
Fingerprint types

13
Minutia detection overview
14
Orientation field

• Orientation field (or ridge flow) estimation
• Crucial step before image enhancement
• Various methods
• Gradient-based
• Gabor filters
• FFT

15
Orientation estimation

• Gradient direction
• local characteristics
• same ridge orientation, opposite gradients
• more global view needed
• Classical solution Structure tensor(second
  moment matrix, interest operator)
• start from a 2x2 matrix(positive semidefinite)
• safe to average information

16
Orientation estimation

• Structure tensor
• Local
• Larger scale average componentwise(Gaussian
  window, linear/nonlinear smoothing)
• 2 nonnegative eigenvalues
• both small backgroung / low contrast
• one big, one small regular ridge area
• both big multiple orientations (core, delta,
  scar)

17
Orientation estimation

• Structure tensor
• system of 2 orthogonal eigenvectors
• shows dominant direction

18
Orientation estimation
19
Orientation estimation
20
Orientation estimation

• Problematic images

• Solution
• Enforce smoothness
• Use prior knowledge

21
Orientation model
22
References

• Maltoni et al. Handbook of Fingerprint
  Recognition. Springer 2003.
• Maltoni. A tutorial on fingerprint recognition.
  In LNCS 3161, Springer 2005.
• Hong, Wan, Jain. Fingerprint image enhancement
  algorithm and performance evaluation. IEEE PAMI
  1998.
• Zhou, Gu. A model-based method for the
  computation of fingerprints orientation field.
  IEEE TIP 2004.
• Weickert. Coherence enhancing shock filters. DAGM
  2003.
• Contact mrazekp -at- cmp.felk.cvut.cz