Upgrading Security - The Drinking Water - page 270

Hand and finger geometry recognition systems can be used in several dif-
ferent types of applications, including access control and time and attendance
tracking. Although time and attendance tracking can be used for security
purposes, it is primarily used in operations and payroll areas (e.g., clocking
in and clocking out). In contrast, access control applications are more likely to
be security related. Biometric systems are widely used for access control and
can be used to protect various types of assets, including entryways, comput-
ers, and vehicles. Because of their size, however, hand and finger recognition
systems are primarily limited to use in entryway access control applications.
Biometric Iris Recognition
The iris is the colored or pigmented area of the eye surrounded by the sclera
(the white portion of the eye); it is a muscular membrane that controls the
amount of light entering the eye by contracting or expanding the pupil (the
dark center of the eye). The dense, unique patterns of connective tissue in the
human iris were first noted in 1936, but it was not until 1994, when algorithms
for iris recognition were created and patented, that commercial applications
using biometric iris recognition began to be used extensively. Currently, two
vendors are producing iris recognition technology—the original developer
of these algorithms as well as another company that has developed and pat-
ented a different set of algorithms for iris recognition.
The iris is an ideal characteristic for identifying individuals because it is
formed in utero , and its unique patterns stabilize around eight months after
birth. No two irises are alike—neither an individual's right and left irises nor
the irises of identical twins. The iris is protected by the cornea (the clear cov-
ering over the eye); therefore, it is not subject to the aging or physical changes
(and potential variation) that are common to some other biometric measures,
such as the hand, fingerprints, and the face. Although some limited changes
can occur naturally over time, these changes generally occur in the melanin
of the iris and therefore affect only the eye's color, not its unique patterns.
Because iris scanning uses only black and white images, color changes do
not affect the effectiveness of the scan. Barring specific injuries or surgeries
directly affecting the iris, the unique patterns of the iris remain relatively
unchanged over an individual's lifetime.
Iris recognition systems employ a monochromatic, or black and white,
video camera that uses both visible and near-infrared light to take a video of
an individual's iris. Video is used rather than still photography as an extra
security procedure. The video is used to confirm the normal continuous fluc-
tuations of the pupil as the eye focuses, which ensures that the scan is of a
living human being and not a photograph or some other attempted hoax. A
high-resolution image of the iris is then captured or extracted from the video
using a device often referred to as a frame grabber . The unique characteristics
identified in this image are then converted into a numeric code, which is
stored as a template for that user.