Design and Fabrication of 3D Fingerprint Targets

Abstract

Standard targets are typically used for structural (white-box) evaluation of fingerprint readers, e.g., for calibrating imaging components of a reader. However, there is no standard method for behavioral (black-box) evaluation of fingerprint readers in operational settings where variations in finger placement by the user are encountered. The goal of this research is to design and fabricate 3D targets for repeatable behavioral evaluation of fingerprint readers. 2D calibration patterns with known characteristics (e.g. sinusoidal gratings of pre-specified orientation and frequency, fingerprints with known singular points and minutiae) are projected onto a generic 3D finger surface to create electronic 3D targets. A state-of-the-art 3D printer (Stratasys Objet350 Connex) is used to fabricate wearable 3D targets with materials similar in hardness and elasticity to the human finger skin. The 3D printed targets are cleaned using 2M NaOH solution to obtain evaluation-ready 3D targets. Our experimental results show that (i) features present in the 2D calibration pattern are preserved during the creation of the electronic 3D target, (ii) features engraved on the electronic 3D target are preserved during the physical 3D target fabrication, and (iii) intra-class variability between multiple impressions of the physical 3D target is small. We also demonstrate that the generated 3D targets are suitable for behavioral evaluation of three different (500/1000 ppi) PIV/Appendix F certified optical fingerprint readers in the operational settings.Keywords-3D fingerprint targets, fingerprint reader evaluation, 2D calibration patterns, 3D printing, 2D pattern to 3D surface projection.

Universal 3D Wearable Fingerprint Targets: Advancing Fingerprint Reader Evaluations

“…2 (e)). Like previous fingerprint targets in [3], the universal fingerprint targets share a 3D geometry similar to a fingerprint surface, have mechanical properties similar to human skin, and are mapped with a fingerprint image, either real or synthetic. However, unlike previous fingerprint targets, the universal fingerprint targets are unique in that they incorporate the technically pertinent mechanical, optical, and electrical properties of the human skin within a single target (Table 1), making it possible for the universal fingerprint targets to be imaged by all major fingerprint sensing technologies in use (capacitive, contact-optical, contactless-optical).…”

“…This process is further broken down and expounded upon in the following steps. i) Inner Mold Surface -Using techniques similar to [3], a 2D fingerprint image is mapped onto a smooth 3D finger surface mesh S in a manner that retains the topology inherent to the 2D image ( Fig. 5 (a)).…”

“…(i) Error in Electronic Modeling of Fingerprint Mold -Arora et al [3] showed that the projection algorithm used to map 10. This is a coarse estimate based on the reported toughness of the digital ABS mold material [34].…”

“…Because the electronic fabrication of the fingerprint mold ( Fig. 4 (a)) uses the same 2D to 3D projection algorithm as [3], the same error will be encountered in our universal fingerprint target fabrication process.…”

“…Previous attempts to evaluate the fingerprint reader component have been predominantly undertaken by the FBI and constitute the Appendix F and PIV standards [17]. The Appendix F standard is comparatively stringent, requires pristine image capture, and is designed to facilitate eval- [3], (b) 3D fingerprint target printed using TangoPlus FLX 930 [4], (c) 3D fingerprint target printed using TangoBlackPlus FLX980 and then sputter coated with 30 nm titanium + 300 nm of gold [5], (d) our casted 3D fingerprint target using mixture of PDMS (Polydimethylsiloxane) and Pantone 488C color pigment [6] [7], and (e) our casted universal 3D fingerprint target using mixture of conductive PDMS, silicone thinner, and Pantone 488C color pigment [6] [8] [9]. 3D targets in (a), (b), and (c) were printed on a high resolution 3D printer (Stratasys Objet350 Connex).…”