3D TOUCHLESS FINGERPRINTS: COMPATIBILITY WITH LEGACY ROLLED IMAGES
Yi Chen
1
, Geppy Parziale
2
, Eva Diaz-Santana
2
, and Anil K. Jain
1
1
Michigan State University
Department of Computer Science and Engineering
East Lansing, Michigan, 48824
2
TBS Holding AG
Schindellegistrasse 19
CH-8808, Pfaeffikon, Switzerland
ABSTRACT
Fingerprints are traditionally captured based on contact of the
finger on paper or a platen surface. This often results in partial
or degraded images due to improper finger placement, skin
deformation, slippage and smearing, or sensor noise from wear
and tear of surface coatings. A new generation of touchless
live scan devices that generate 3D representation of finger-
prints is appearing in the market. This new sensing technol-
ogy addresses many of the problems stated above. However,
3D touchless fingerprint images need to be compatible with
the legacy rolled images used in Automated Fingerprint Iden-
tification Systems (AFIS). In order to solve this interoperabil-
ity issue, we propose a unwrapping algorithm that unfolds the
3D fingerprint in such a way that it resembles the effect of
virtually rolling the 3D finger on a 2D plane. Our prelimi-
nary experiments show promising results in obtaining touch-
less fingerprint images that are of high quality and at the same
time compatible with legacy rolled fingerprint images.
1. INTRODUCTION
An automated fingerprint authentication system consists of
three components, namely, image acquisition, feature extrac-
tion and matching. Among the three, image acquisition is
often considered the most critical as it determines the finger-
print image quality, which has a large effect on the system per-
formance [1]. Traditionally, fingerprint images are acquired
by pressing or rolling a finger against a hard surface (e.g.,
glass, silicon, polymer) or paper (e.g., index card). This often
results in partial or degraded images due to improper finger
placement, skin deformation, slippage and smearing, or sen-
sor noise from wear and tear of surface coatings.
A number of companies are developing touchless sensing
technology that performs “finger imaging” as opposed to con-
ventional “finger printing” [2, 3]. That is, the sensor images a
finger from different views using a multi-camera system and
reconstructs a contact-free 3D representation of the finger-
print. Touchless sensing technology provides an idea solu-
tion to the intrinsic problems of the contact-based technology
as stated above and results in repeatable and high quality im-
age acquisition. In addition, the reconstructed 3D fingerprint
gives a much larger, nail-to-nail representation of the finger-
print, compared to conventional contact-based fingerprints.
3D touchless fingerprints, however, need to be compati-
ble with the conventional contact-based 2D rolled fingerprint
images used in Automated Fingerprint Identification Systems
(AFIS). In order to make 3D touchless fingerprints interop-
erable with current AFIS systems, we introduce a simulated
rolling procedure which essentially unwraps the 3D touch-
less fingerprints into 2D such that the resulting 2D finger-
prints are comparable with legacy rolled fingerprints. This
is a very challenging task because the simulated rolling pro-
cedure must not introduce distortions other than those com-
patible with the physical deformation of skin due to rolling.
As a result, we propose “Equidistance Unwrapping” to min-
imize the distortion during unwrapping while preserving the
“ground-truth” of the fingerprint.
The rest of the paper is organized as follows: Section 2 de-
scribes the procedure for 3D reconstruction of touchless fin-
gerprints. Section 3 describes various unwrapping methods to
unfold the 3D fingerprint to 2D, specifically, the cylindrical-
based parametric unwrapping and the proposed non-parametric
unwrapping method. In Section 4, we compare the two un-
wrapping methods by showing the final unwrapped images.
Compatibility of the unwrapped and conventional rolled im-
ages is also shown on a small database. Conclusions and fu-
ture work follow in Section 5.
2. 3D RECONSTRUCTION OF TOUCHLESS
FINGERPRINTS
Touchless fingerprinting is essentially a remote sensing tech-
nique used to capture the ridge-valley pattern. While it is not