Under the Lid
Unlike the retina scans you see in the movies, which shine a bright light through the pupil to capture images of blood vessel patterns at the back of the eye, iris recognition uses a camera to take a photograph of the iris -- the colored portion of the eye.
During fetal development, the eye goes through a process called chaotic morphogenesis that gives each iris its unique appearance. "When the optic nerve comes out of the brain, it essentially pumps out the eyeball, which rips and tears. Striations in the iris are the result of that," says Neil Norman, founder of Human Recognition Systems (HRS).
Iris recognition systems are extremely accurate; they're 100,000 times less likely to produce a false match than facial recognition systems, Grother says. Other benefits: The matching process is very fast and, unlike faces, the eye doesn't change much with age.
NIST recently completed a study on the subject of iris recognition. While face photos on passports are generally replaced every five to 10 years, "the iris is good for decades," Grother says. And because each eye has a unique pattern, vendors offer dual-eye systems, such as the one used in Symantec's Vault, for even higher accuracy. "Ten fingerprints are the gold standard for identification. A pair of irises are at least equivalent to eight or 10 fingers, and maybe more," Grother says.
But accuracy also depends on the integrity of the data, he cautions. While iris recognition technology doesn't require physical body contact (which is considered a plus), it does require the cooperation of the individual, and the type of system used can greatly affect accuracy. "If I take the image with a cellphone camera, the error rate will be much worse," Grother says.
Iris recognition systems need to overcome environmental issues such as reflections, bright sunlight, thick eyeglasses, colored contact lenses and eye conditions that may cause dilation or other changes in the iris. Today, "state-of-the-art iris recognition systems can deal with all of these," says Brian Martin, director of biometric research at MorphoTrust, a developer of identity verification systems.
Functionally, iris recognition cameras aren't much different from digital SLR cameras, except that the light filters over the sensors allow near-infrared light to pass through instead of visible light, says Martin.
Iris recognition systems encode the entire eye structure, following an open standard. And because the process doesn't focus on detailed feature points, a grayscale 640-x-480-pixel image is sufficient. That's one reason why the recognition algorithms can speedily process data and respond quickly. "The old VGA format turns out to be all you need. High resolution is not needed, and in fact would slow things down," says Grother.
Sophisticated, high-end cameras capable of capturing images at distances of 2 meters can cost $30,000 or more, but other models suitable for business use that operate at close range may run as little as a few hundred dollars.