Introduction - If you have any usage issues, please Google them yourself
Face recognition [1], the least intrusive biometric technique
in terms of acquisition, has been applied to a wide range
of commercial and law enforcement applications. State-ofthe-
art face recognition systems perform with high accuracy
under controlled environments, but performances drastically
decrease in practical conditions such as video surveillance
of crowded environments or large camera networks. The
main problems are due to changes in facial expressions,
illumination conditions, face pose variations, and presence
of occlusions.