January 2004

Table of Contents

Iris-Based Recognition:
Keep Your Eye on It!

A quick, simple, noncontact, noninvasive way to prove who you are can race you through customs, let you into restricted areas, or keep your children safe at school. It’s all in the eyes.

Stephanie vL Henkel


Let’s begin our look at iris-based recognition by seeing what it’s not. It’s not a “stealth” technology intended to identify suspicious behavior from a distance. It can’t be used for any sort of “profiling.” And it won’t work on anyone who hasn’t chosen to have his or her irises scanned and the images stored for reasons of security and convenience. So it’s strictly opt-in or opt-out.

Now let’s see what iris recognition is, beginning with a few facts about the eye. The white part is the sclera, the dark disc in the center is the pupil, and the colored circle between the sclera and the pupil is the iris. The iris begins to form in the third month of gestation and is for the most part complete by the eighth month. Even though pigmentation can continue to change for months after birth, color is not important in iris recognition. What are significant are features such as furrows, ridges, rings, freckles, and other elements of the patterns that make every iris unique—even your two eyes are not identical to each other. Short of trauma severe enough to cause blindness, your iris patterns will never change.

Conversely, fingerprints can be altered or even obliterated, and small children’s prints are extremely evanescent due to the volatility of the natural oils in juvenile skin. Identical twins can defy even their parents’ efforts to tell them apart by their faces, gestures, voices, and gaits. A stolen wallet contains everything the thief needs to pass as you. And we all know how easy it is to forget our PINs.

So let’s take a closer look at IriScan, an iris recognition, image storage, and template-matching system developed and marketed by Iridian Technologies. Then we’ll check out some examples of where it’s at work today.

IriScan Details
Iris recognition can be used in two modes. In verification mode, a live iris is compared with a scan that has previously been stored on a card. In identification mode, a live iris is compared with all scan records in a database. The former is a one-to-one match and generally used to prevent in-house security breaches. The latter, a one-to-many match, is more common in public facilities such as airports and border crossing points. Recognition (or rejection) takes only seconds in either mode.

To be scanned, you look from a distance of 5–24 in. into a monochrome CCD camera operating on NIR in the 700–900 nm band, invisible and safe to the human eye. To capture all the pattern details, the camera needs to resolve at least 70 pixels of iris radius. Even so, your iris is photographed in a few seconds. The image is first processed by software that localizes the inner and outer boundaries of the iris, as well as the eyelid contours, in order to extract only the iris portion. Mathematical software encodes the iris pattern by means of quadrature 2D Gabor wavelets in a process called demodulation. The result is a very compact yet complete description of the iris pattern, regardless of size and pupil dilation, in only 512 bytes. The phase sequence, called an IrisCode template, is immediately encrypted to eliminate the possibility of identify theft and to maximize security.

Figure 1. Identification mode, a one-to-many comparison, requires only a scan of a live iris that has been previously entered into a database.
When your stored IrisCode is subsequently compared to your eye, the decision threshold is automatically adjusted for the size of the search database to make sure there are no false matches. Further, some of the bits in the template determine if part of the data is corrupted by eyelashes, reflections, or contact lens boundaries, so that only valid data are compared. Decision thresholds take into account the amount of visible iris, and the matching operation compensates for any tilt of the iris. For verification, you hold up your card and look into the same sort of camera that created your IrisCode in the first place. For identification, just a gaze will do it (see Figure 1).

The IriScan at Work
So why would you—or anyone—want to have your iris scanned? In some cases, the IrisCode is a free pass to the head of the line. In others, it helps keep your child safe. And sometimes it’s a job requirement.

 Air Travel. CANPASS, a joint initiative of the Canada Customs and Revenue Agency and Citizenship and Immigration Canada, serves travelers at Vancouver (BC) International Airport. Passengers who have established their credentials of trustworthiness and stored their IrisCodes are allowed to clear customs quickly and without hassles. Open at present to citizens and permanent residents of the U.S. and Canada, the program will in time be extended to other visa-exempt countries and NAFTA business travelers.

Figure 2. Employees at JFK Airport gain access to the Terminal 4 tarmac by using verification mode, a one-to-one comparison. The live iris is read against a printed image made from the initial scan. No match, and the door won’t open.
At JFK Airport, employees who want access to the tarmac at Terminal 4, the international arrivals hall, have to match an iris to their IrisCode cards (see Figure 2). The card alone won’t let the door be opened; if there’s a mismatch, security personnel will be right on the scene.

 Schools. We’ve all read too many news stories about young children picked up at school in what amounts to an abduction by one parent estranged from the other. That’s unlikely to happen at the New Egypt school in Plumsted, NJ. Nor will the facility be entered by anyone who has no business there. Enrollment in the scan plan is required of school employees, and parents and other caregivers are invited to join. Nonparticipating parents must show an ID and wait for their particulars to be keyed into a computer before a child is released into their custody.

 Prisons. All staff members at the Lancaster County (PA) Prison must submit to a background check (we should hope so!) and store their IrisCodes. More than 1000 regular visitors have signed up too, which serves to speed up their admittance on visiting days. In a separate application, prison inmates are scanned at both booking and release to thwart identity fraud. According to prison officials, it’s working well.

Figure 3. New mothers at a German hospital are scanned in identification mode before they can take their babies home. The reason is to prevent baby-snatching.
 Hospitals. The City Hospital of Bad Reichenhall in Bavaria, Germany, is using iris recognition to prevent baby-stealing. Only authorized personnel, including new mothers, can get into the infant station (see Figure 3). Once the baby is released from the hospital, the mother’s IrisCode is removed from the system and she can’t get back into the secure newborn area.

At the University of South Alabama Hospitals in Mobile, iris recognition-enabled medical records management makes sure that only clinicians with approved access privileges can view medical information and associated reports. The system is part of the university’s strategy for compliance with the Health Insurance Portability and Accountability Act (which we all know as HIPAA).

We U.S. citizens have always rejected the idea of having to carry identity cards, but let’s face it—sooner or later nearly all of us have to produce some proof that we are who we say we are. There’s no single way to establish our bona fides that will suit everyone or even make sense for those who stay out of hospitals, prisons, schools, and airports. For those whose jobs demand a high level of security, though, and others who just want to sail through customs or control access to their school-age children, iris recognition is an extremely attractive technology. It’s noninvasive, noncontact, extremely accurate, and impossible to lose or forget. Give it some thought.

John Daugman, Ph.D., OBE, has researched and written extensively on iris recognition technology. Among the excellent papers available at his Web site is “How Iris Recognition Works.”

Stephanie vL Henkel is Executive Editor of Sensors.

For more information on IriScan, contact Talvis McLaughlin, Iridian Technologies, Moorestown, NJ; 856-222-3160, tmclaughlin@iridiantech.com.

For further reading on this and related topics, see these Sensors articles.

"Fingerprint Identification and Authentication," January 2003

Sensors Weekly
  What's New
  Product Picks

Questex Media
Home | Contact Us | Advertise
© 2009 Questex Media Group, Inc.. All rights reserved.
Reproduction in whole or in part is prohibited.
Please send any technical comments or questions to our webmaster.