Abstract
Ultrasound has been trialed in biometric recognition systems for many years, and at present different types of ultrasound fingerprint readers are being produced and integrated in portable devices. An important merit of the ultrasound is its ability to image the internal structure of the hand, which can guarantee improved recognition rates and resistance to spoofing attacks. In addition, ambient noise like changes of illumination, humidity, or temperature, as well as oil or ink stains on the skin do not affect the ultrasound image. In this work, a palmprint recognition system based on ultrasound images is proposed and experimentally validated. The system uses a gel pad to obtain acoustic coupling between the ultrasound probe and the user’s hand. The collected volumetric image is processed to extract 2D palmprints at various under-skin depths. Features are extracted from one of these 2D palmprints using a line-based procedure. Recognition performances of the proposed system were evaluated by performing both verification and identification experiments on a home-made database containing 281 samples collected from 32 different volunteers. An equal error rate of 0.38% and an identification rate of 100% were achieved. These results are very satisfactory, even if obtained with a relatively small database. A discussion on the causes of bad acquisitions is also presented, and a possible solution to further optimize the acquisition system is suggested.
Highlights
The use of biometric systems is continuously expanding in a wide variety of civilian applications where authentication based on behavioral or physiological characteristics is often replacing classical methods based on ID cards, passwords, or tokens
Capacitive sensors have been mainly tested for authentication based on fingerprint [5] and, more recently, there is a growing research interest in biometric systems based on photoacoustic sensors [6,7]
The simplest way to generate an ultrasonic 1D image is the amplitude mode (A-mode); it consists of transmitting a wave from a source and receiving reflected echoes after they have propagated in a medium
Summary
The use of biometric systems is continuously expanding in a wide variety of civilian applications where authentication based on behavioral or physiological characteristics is often replacing classical methods based on ID cards, passwords, or tokens. The optical approach is generally relatively cheap thanks to the use of low-cost visible-band cameras, and can provide high-resolution images It is the most exploited, as it allows the acquisition of several biometrics, including face, fingerprint, iris [1], and palmprint [2]. In order to provide a good propagation of the ultrasound wave, both the transducer and the hand were submerged in a water tank during acquisition Even though this modality allowed to excellent recognition results to be obtained, such a wet system is not suitable for practical application because it is not acceptable to users.
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