Master Thesis - Department of Computer Science
Master Thesis - Department of Computer Science
Master Thesis - Department of Computer Science
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Prior to Matching<br />
Sensor Level Feature Level<br />
Abstract Level<br />
(i) Majority Voting<br />
(ii) Behavior Knowledge<br />
Space<br />
(iii) AND Rule<br />
(iv) OR Rule<br />
(i) Weighted Summation<br />
(ii) Concatenation<br />
Information Fusion in Biometrics<br />
(i) Sum Rule<br />
(ii) Product Rule<br />
(iii) Max Rule<br />
(iv) Min Rule<br />
(v) Weighted Sum<br />
Combination<br />
Approach<br />
Dynamic<br />
Classifier<br />
Selection<br />
After matching<br />
Rank Level Measurement Level<br />
(i) Highest Rank<br />
(ii) Borda Count<br />
(iii) Logistic<br />
Regression<br />
Class−conscious<br />
Approach<br />
Class−indifferent<br />
Approach<br />
(i) Decision Template (DT)<br />
(ii) Demster−Shafer (DS)<br />
(iii) Neural Network (NN)<br />
(i) k−NN<br />
(vi) Logistic Classifier (LOG)<br />
Decision<br />
Level<br />
Fusion<br />
(ii) Decision Trees<br />
(iii) SVM<br />
Classification<br />
Approach<br />
(iv) Linear Discriminant Classifier (LDC)<br />
(v) Quadratic Discriminant Classifier (QDC)<br />
Figure 2.11: Summary <strong>of</strong> approaches to information fusion in biometric systems.<br />
For example, the face images obtained from several cameras can be combined<br />
to form a 3D model <strong>of</strong> the face.<br />
• Feature level: Feature level fusion refers to combining different feature vec-<br />
tors that are obtained from one <strong>of</strong> the following sources: multiple sensors for<br />
the same biometric trait, multiple instances <strong>of</strong> the same biometric trait, multi-<br />
ple units <strong>of</strong> the same biometric trait or multiple biometric traits. When feature<br />
vectors are homogeneous, a single resultant feature vector can be calculated as a<br />
weighted average <strong>of</strong> the individual feature vectors. In case <strong>of</strong> non-homogeneous<br />
features, we can concatenate them to form a single feature vector which is not<br />
possible for incompatible feature sets. Attempts by Kumar et al. [66] in com-<br />
bining palmprint and hand-geometry features and by Ross and Govindarajan<br />
37