Abstract
Conventional fingerprint sensors that are deployed in real-life applications lack the ability to peer inside a finger beyond the external surface. Subsurface information can provide complimentary biometric characteristics associated with the finger. The subsurface fingerprints can also be employed when the quality of the external/surface fingerprints is affected. One of the most promising technologies for imaging below the surface of an external fingerprint is full-field optical coherent tomography (FF-OCT). However, the FF-OCT can be expensive and cumbersome, despite its proven ability for biometric use. In this paper, we describe the design and implementation of a compact, mobile and cost-effective FF-OCT sensor that is stable and easy to use. The newly designed sensor, being $30 \,\,cm \,\,\times \,\,30 \,\,cm \,\,\times \,\,10 \,\,cm$ in size, comprises of a dedicated silicon camera, stable Michelson interferometer and a bright Near-Infra-Red (NIR) light emitting diode. It enables recording of $1.7 \,\,cm \times 1.7 \,\,cm$ images of subsurface finger features, such as internal fingerprints and sweat ducts. We show the employability of the newly designed sensor for different applications. Specifically, we validate its usefulness by capturing subsurface fingerprints of 585 subjects leading to 3510 unique fingerprints. The resulting accuracy of 0.74% as Equal Error Rate ( $EER$ ) indicates the backward compatibility of the proposed sensor with the existing commercial off-the-shelf algorithms. Thanks to the large fingerprint database collected in this work we determined the most useful imaging depth for the fingerprint matching purposes to be around $100~\mu m$ . As an additional advantage, the sensor could be readily used in other applications with little or no modification, such as $in ~vivo$ skin imaging.
Highlights
Fingerprint sensing is indispensable in many security oriented applications, such as access control to buildings and various devices, as well as border control [1]
Using the biometric analysis on large fingerprint database, described below in Section IV, we show in Fig. 10a that Equal Error Rate (EER) is lowered approximately 3 times when binning is performed on subsurface images and Failure To Enroll (FTE) - 22 times
Unlike the previous works, where the full-field optical coherent tomography (FF-Optical Coherence Tomography (OCT)) sensor was constructed on a bench top, the newly designed OCT sensor is mobile and costeffective
Summary
Fingerprint sensing is indispensable in many security oriented applications, such as access control to buildings and various devices, as well as border control [1]. Light coming back from the reference and the sample arms was recombined by the same beamsplitter and reimaged onto the camera with the objective and tube lenses (L4 and L5, respectively, in Fig. 2) in 4 − f configuration It effectively performed 1 : 1 imaging since the objective and the tube lenses had the same focal length of 10 cm. For subsurface fingerprint imaging on a large scale (database collection), 13 FF-OCT images were acquired at different depths by stepping the reference reflector every 50 μm between the acquisitions, resulting in images acquired in the range of 0 μm to 600 μm. High spatial resolution achieved with the sensor allows imaging the so called level 3 features of the fingerprints [6], such as sweat ducts, as is demonstrated in this article in Fig. 6 and 7, which can be used for the recognition purposes.
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