Blood movement inside a finger causes color changes in a fingerprint image during a fingerprint input action. We
consider models to relate this information to the stiffness of a collective blood vessel in a finger. In the simple resistor
model, finger area is regarded as voltage and the color change was regarded as current. We define its resistance as the
ratio of these two quantities according to Ohm's law. However, experiments show that this resistance value increases
as the force applied to a finger increases. Second, we consider the variable resistor model to account for this force
dependency. We assume that the driving force decreases the cross-section of the blood vessel and that stress and strain
are related by Young's modulus. Experiments by six participants show reasonably good fittings for the extracted
signals and the model's predictions. The correlation coefficient between the extracted parameter and the average blood
pressures of the participants was 0.75.
When a finger is pressed against a flat plate and deformed, blood inside the finger moves away from the deformed
area. This causes the finger to change its appearance from reddish to white. As the finger leaves the plate, the blood
comes back and it looks reddish again. We have proposed to use this color change to distinguish genuine fingers from
artificial ones for un-attended fingerprint identification systems. This blood-related signal may reflect the stiffness of
the peripheral blood vessels and therefore it may be correlated with some health conditions such as blood pressure. In
experiments, we used a fingerprint sensor based on scattered light detection. Because the spectra of the light scattered
by the deformed fingers showed large changes mostly in the green portion, an LED emitting at 525 nm at peak strength
was used. First, we compared series of fingerprint images acquired during a normal input action and those obtained
while a rubber band occluded the blood flow. The occluded finger required a larger force to exhibit a similar change
for these pixel values than the finger without the rubber band. Second, we analyzed fingerprint images recorded by six
volunteers. We defined some indices based on the pixel values of the fingerprint images and the pressure applied to
the fingers. The correlation coefficient of one of such indices and the average blood pressure of the participants was
0.86. Although the number of the subjects is small, this initial result is encouraging.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.