Tony Lee: Fingerprint Readers


Nov 30, 2013 (4 years and 7 months ago)


Tony Lee

ECE 4007

James & Koblasz

Medical Workstation


Fingerprint Reader Technology


Fingerprints are unique characteristics that have been used to identify individuals, however only recently
has this method of
identification been a
pplied to user access control. Since fingerprints patterns vary
from person to person even in twins, it is one of the primary biometrics used in authenticating a person.
There are a couple of methods used to measure and analyze finge
rprints which include optically capturing
the ridge pattern, capacitive analyzing the ridge pattern, and the current state of the art method is to
optically analyze the
blood vessels on the finger. Other sensors such as thermal, pressure, and radio
ncy are used in conjunction with the aforementioned methods by various companies and designers
for improved security and validity.

Commercially Available Products

The cheapest commercially available product would be the Eikon Solo priced around $12 depe
nding on
location. The Eikon is a swipe imaging type of fingerprint reader with a 144 pixel wide scanning array.
It is rated to image a fingerprint swipe of upto 25 cm per second, has an image resolution of 508 DPI, dots
per inch, records fingerprints as

an 8
bit gray scale array allowing 256 different shades of gray, and
a USB 2.0 interface


While the top of the line product offered by the same company is the
EikonTouch 700 which is priced around $100. The EikonTouch 700 different from the

Solo in that the
entire fingerprint is captured at once. A 256 x 360 photo
sensitive array that can capture 5.5 frames per
second is used. It offers the same DPI, gray scale depth, and interface however, features between 56
bit USB data encryption a
s well as 256

bytes of on
board data storage


There are many other
commercially available products which offer different methods of authentication and features

the focus of this review
is to balance functionality and economic feasibility for
the design project.

Technology utilized in

Fingerprint Readers

Capacitive Sensors: The premise of capacitive fingerprint analysis is that skin acts as a capacitor plate
with ridges and valleys having different capacitances when measured. The fin
gerprint reader is
comprised of an array of “cells”, each cell represents a pixel to form an image. Each
cell is essentially
two parallel plates connected to an inverting operational amplifier that grounds the non
inverting input
and is connecte
d to an in
put reference voltage


The output of the op
amp is connected to an analog
to digital converter which defines the color depth of each cell.

Optical Sensors: The premise of optical fingerprint analysis is that photosensitive diodes, photosites,
ce differing output

signals when exposed to the ridges and valleys of a fingerprint. The image of
the fingerprint is created by an array of CCDs, Charge Coupled Devices. A CCD is similar to the “cell”
described in the capacitive sensor with the primary
difference is that a CCD is comprised of a light
emitting diode, photosite, and op
mp instead of conductive plates


The output of the photosite is
similarly connected to an analog to digitial converter which defines the color depth of each pixel.

The State

Although fingerprints are unique to everyone the vulnerability the fingerprint is that it’s reproducible with
various methods allowing circumvention and false user access. The technology currently being
developed utilizes the same pr
emise of optical sensors with the key difference in that the fingerprint itself
isn’t being analyzed but, blood vessels beneath the skin is imaged. This is accomplis
hed by using near
infrared LED

instead of a standard

broad spectrum


Another differen
ce in the system is that the
intensity of the near
infrared LED has to be adjusted to p
roduce viable pattern


The capture and
analog to digital conversion of the blood vessel pattern is similar to previous methods. There are
experimental setups that
utilize this technology and are currently being researched further meaning there
are no commercially available products that currently utilize this method yet.


Nagasaka, et al.
, “
Finger identification method and apparatus,” U.S. Patent

8 103 064, December 17,

[2] T. Harris. (2
02, Sept. 24). How Fingerprint Scanners Work. [Online].

] 360Biometrics. (2012, Jan
. 24).
Fingerprint Scanner. 360Biometrics
.com. [Online]. Available:

[4] H
. (2010, Oct.) Hybrid Finger Scanner and Multi
modal Biometric Authentication
Technology. NEC Technical Journal. [Online]. 5(3), Available:

[5] AuthenTec. (2012, Jan. 24). Specifications. [Online]. Available:

[6] S. Han, Z. Zu, C. Sun. The recognition based on band tree for blood vessel of ocular fundus. presented
at Mechatronics and Automation, 2009. [Online]. Available:

[7] S. Mil’shtein, V. Oliyil Kunnil, C. McPherson, A. Pillai. (2011) Handheld Imaging System for
Contactless Tri
ModalBiometric Identification. American Journal of Biomedical

Engineering. [Online].
1(2), Available: