Fingerprint images captured by touch-less sensors are very
different from fingerprint images captured by traditional touchbased
sensors. Typically, such kind of images are more noisy,
the ridge pattern is less visible and the color of the sky
can significantly change. Moreover, defocusing problems as
well as blur effects due to the movements of the finger can
be present. For this reason, in a biometric system designed
for touch-less fingerprint images, the feature extraction and
image processing methods must be carefully selected and
tuned taking into account the presence of the specific noise
type related to the biometric samples.