Fingerprints identification systems are accepted gradually in the world. However, they can be fooled by artificial fingers (replicas) and this fact is reported in the literatures and the Internet. Therefore, life recognition is desired for unattended fingerprint identification. We look at the color changes in a series of fingerprint images acquired during the course of an input action. As we press a finger upon an input device, a fingerprint area gradually increases and its color changes. This is due to the blood movements induced by a finger deformation. A fingerprint sensor based on scattered-light detection can detect this information on the blood movement inside a finger more clearly than a conventional sensor using a prism. In order to extract more information from a finger-tip, we consider an input device equipped with light sources emitting in different narrow wavelength bands, namely a multi-spectral fingerprint sensor. In experiment, we used two LEDs emitting in the visible light and turned them at the same time. From a series of fingerprint images captured by a CMOS camera, we extracted the characteristic of color change of live finger. However, there are not characteristic such as them by replica. This difference can be utilized to reject replicas for fingerprint identification.
Masashi Kurita, Katsuki Tai, Ichiro Fujieda, "Multi-Spectral Imaging of Fingerprints for Secure Biometric Systems" in Proc. IS&T 13th Color and Imaging Conf., 2005, pp 251 - 255, https://doi.org/10.2352/CIC.2005.13.1.art00046