by Michael Keller

The eye is more than the window into the soul, it’s also the best identity card you can carry. A good photo of the colored part around the pupil called the iris contains so many unique features that researchers say it can tell who you are with an accuracy of about one in a billion people. Even the irises of identical twins are different because the finer points of its structure aren’t based on genetics alone.

These facts have made this single feature of the eye the subject of intense study in the world of biometric identification, which uses physical features like the face or palm and behavioral characteristics like how someone walks to figure out who a person is. And the technology is starting to be used around the world because iris scans can be done with a camera, require no contact with the subject and don’t carry the same stigma as being fingerprinted. For example, India’s Unique Identification Authority, a national government agency, is working to issue a national ID card that includes an iris scan to India’s 1.24 billion citizens in the next several years.

But projects like India’s and others happening around the world to identify individuals through their irises have at least one major limitation—subjects have to let their irises be photographed. Current technology needs to be close to the face and the lens has to be pointed almost straight at the eye.

That might be a slightly better situation for privacy advocates, but it’s just not good enough for biometrics researchers, companies and military and security officials. Several groups are working on what’s called long-range standoff iris recognition systems, which have to be neither close nor directly in front of the subject.

What’s this mean? Somewhere not too far off into the future, the advertisement-customizing, always-watching surveillance technology depicted in the 2002 film Minority Report will be a real thing.

Now a team working on standoff iris recognition at Oak Ridge National Laboratory (ORNL) is reporting that they have taken a significant step toward scanning wandering eyes.

“Historically, iris identification requires a full frontal shot to work,” says Chris Boehnen, ORNL’s Biometrics and Forensics Program Manager. “But you want a system to capture uncooperative irises like in Minority Report. Existing technology can’t do that.”

The major obstacle to realizing the Hollywood fantasy, Boehnen tells Txchnologist, is that when you take a picture of an iris in profile and compare it to a full frontal picture, the two angles make the eye look different. But a standoff system would need to match a person’s iris from almost any direction. “What we’re trying to do is use a corrective model to extract the iris pattern and make it look the same no matter whether the original picture was full frontal or off-angle,” he says.

Much of the work to give iris scanners more leeway for accidental eye movements or camera lenses that are slightly off-angle has involved mathematically adding a little fudge factor to processing software. But building in variance, Boehnen says, can accidentally cause a subject’s iris to match against one in a database that isn’t his or hers.

Instead, the ORNL team has developed image-preprocessing software that uses math and a biologically accurate 3-D model of the eye to take an off-angle picture of the iris and correct it. The result is that they have successfully been able to match pictures taken as much as 50 degrees from the side to ones taken straight on.

(The ORNL team’s off-angle iris recognition system can accurately warp an image of an iris from 50 degrees off-angle to straight on frontal. Courtesy Chris Boehnen/ORNL.)

They arrived at a highly accurate biological model by working with Dr. Ed Chaum, an ophthalmologist at the University of Tennessee-Memphis.

“Biologically, the eye is very complicated,” says ORNL researcher David Bolme. “To make iris recognition as accurate as possible, you must account for the refraction of light by the cornea and other things that weren’t known in the community.”

This part of the research made the team realize that some overlooked anatomy of the eye is actually important if attempting to ID people when they aren’t looking at the camera. The element, called the limbus, forms the border between the white of the eye and the clear cornea that forms a dome over the pupil, iris and lens. “The limbus is a really important area that everyone in the frontal iris recognition community has ignored,” Boehnen says. “But when you’re doing off-angle iris recognition, the limbus actually occludes a statistically significant amount of the iris surface.”

(Schematic of the eye via Wikipedia.)

Their system then uses advanced genetic algorithms as a brute force method of warping an off-angle picture to a full frontal one. With machine learning, the program generates random maps of the warped image and keeps tweaking them to improve recognition success. “Most state-of-the-art off-angle algorithms can match images well when they are taken less than 30 degrees off-angle,” Boehnen says. “As they get closer to 50 degrees off-angle, current technology fails without using our approach.”

His team is also making strides in another aspect of standoff iris recognition—distance. Current commercially available systems, like the ones being used in India and others, need to be held inches away from cooperative person’s face.

They are developing a multicamera, 12-megapixel system that can automatically acquire and scan a person’s iris from up to about 21 feet away. In the not too distant future, Tom Cruise will have nowhere to hide.

(A prototype of the multicamera standoff iris recognition system being developed at ORNL. Courtesy Chris Boehnen/ORNL.)

(This is what the above system sees. At about 21 feet away, the camera records an iris with a resolution of 200 pixels across. Courtesy Chris Boehnen/ORNL.)

Top gif: Minority Report eye scanner scene courtesy 20th Century Fox.