The iris is a part of the eye outside of the pupil that is made of collagen in a three-dimensional arrangement. This pattern can be imaged with light at certain wavelengths.
"It's like taking picture of sand dunes from space," he said. "It's a 3-D object."
The FBI's Iris Pilot program is being deployed by law enforcement officials in California, Texas and Missouri during the booking process. The U.S. Border Patrol and Department of Defense are also using iris scans, according to Stephen Fischer, an FBI spokesman.
The next step is collecting iris scans from photographs of people's eyes.
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"Iris images enrolled in the FBI Iris Pilot are primarily captured during the booking process in a controlled setting with a camera designed to capture the iris image," Fischer said in an email to DNews. "These cameras capture the iris image in near-infrared light. Research is currently being conducted on the extraction of iris images from high-resolution photographs."
People with brown eyes have more pigment than those with blue eyes, said Grother. That makes it tougher to capture iris information from photographs of brown-eyed folks.
Of course, anyone who blinks, squints or scrunches up their eyes will make it difficult for law enforcement to get a good scan.
Grother and other experts now are developing software to recognize iris patterns from several different camera angles, making it easier to use a hand-held device or smartphone.