Science and Technology (S&T) Snapshots

March 11, 2009

The U.S. Department of Homeland Security’s Science & Technology Directorate (S&T) newsletter, S&T Snapshots, features stories about current research projects and opportunities with laboratories, universities, government agencies, and the private sector. 

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Fingers, Meet Photons

Soon Homeland Security’s virtual 3-D light technology will digitize your digits more accurately with less mess.

If only fingerprinting those of us who need a background check was as fun as finger painting, not just an inky drill: Press, press, roll. Repeat nine times. Wash, scrub, and dry. Return to desk to find a message: “One finger didn’t take. When can you return?” Grit teeth and grumble. Recent inkless routines are almost as cumbersome; you just don’t stain your IZOD or your iPod.

Well, in the future you will be able to kiss those frustrations goodbye. Thanks to the U.S. Department of Homeland Security, digital fingerprinting is already in place for international travelers coming to the United States. The Department's United States Visitor and Immigrant Status Indicator Technology (US-VISIT) program uses biometrics, in this case fingerprints, to verify the identities of non‑U.S. citizens entering the country. The current technology can capture up to four fingerprints at a time, making the biometric verification process more accurate and efficient. However, it still requires physical contact with a scanner.

Under a program managed by the Department’s Science and Technology Directorate (S&T), the future of fingerprinting—new 3‑D light technology—will be a hands-off affair that’s even quicker and —dare we say it?—fun.

Cleanliness and entertainment value were not goals; they were just happy accidents. The need was speed and accuracy. Following the 9/11 terrorist attacks, the U.S. government recognized the need for a better way to establish and verify identities of those who might try to do the country harm. In 2004, the Department of Justice’s National Institute of Justice (NIJ) sought advanced concepts under a program called Fast Rolled Fingerprint Capture. S&T and the University of Kentucky answered the call.

The goal: a machine that could capture all 10 fingerprints in high resolution in less than 10 seconds, without a human operator. This next generation technology ruled out procedures with inkpads or touch screens because they distort a finger’s actual shape. The fingerprints of about one in twenty people—roughly 5 percent of the population—are too worn or damaged to be captured using contact ink-rolled fingerprinting, according to the University of Kentucky; and the ink-rolled technique takes 5 to 10 minutes per person.

“What we wanted was great quality as efficiently as possible,” said Michael A. Matthews, a program manager in S&T’s Infrastructure and Geophysical Division.

S&T awarded a grant to the University of Kentucky's Center for Visualization and Virtual Environments, which had refined a technique called structured light illumination, where a pattern of dots or stripes is projected onto a curved or irregular surface. By calculating how the pattern warps over a curve, scientists can calculate an object’s exact shape—similar to how a flying bat uses sonar to distinguish foe from food—by comparing its readings from different angles.

This technology is not another finger scan. Using topological algorithms, software captures all of a finger’s tiny ridges recorded from three cameras and combines them into a single three-dimensional image. The 3‑D image is then “flattened” into a 2‑D virtual fingerprint that’s more precise than an ink-rolled print.

“We believe that these prints will eventually become the gold standard,” said Professor Laurence Hassebrook, the University of Kentucky’s principal investigator. Indeed, by capturing prints with depth information in 256 shades of grey, the structured-light fingerprinter will produce a higher quality of print. One of the benefits of this quality will be the ability to match prints with far greater accuracy.  

If you were to watch the composite images as a rapid series of stills, you’d swear the stripes had physically moved across your skin. They would ripple and warp; darken and brighten; widen and narrow, while traversing the unique contoured ridges that make you, you. But it’s all an illusion: The stripes never moved, any more than a cartoon ballerina in a flip book ever danced.

Can’t a bad guy fool the system by tilting his finger? Nope: The software knows what a fingerprint should look like. Like PhotoShop, it can automatically align the image.

The University of Kentucky’s system won’t be beaming bars and stripes forever. A project goal is to project a single, continuous composite pattern, and use more cameras to capture an entire hand at once, complete with the equivalent of rolled fingerprints. Because of the enormous technical challenge of this goal, a mature version of the technology remains a few years away.

There are many potential applications for this technology. The USA Patriot Act requires fingerprinting for all Hazardous Materials Driver’s Licenses, and many states are currently passing laws to require fingerprinting for everyone applying for a driver’s license.

Structured light fingerprinting won’t replace finger painting. But for accuracy and speed, it beats the old ways of fingerprinting, hands-down. 

Editor's Note (March 17, 2009): While the University of Kentucky project continues to work on a scanner technology that can image the whole hand at once, FlashScan3D has continued development of the structured light 3D scanning technology and has developed a two-step fingerprint reader that images four fingers, then the thumb. The FlashScan3D effort was funded by the Homeland Security Advanced Research Projects Agency (HSARPA) and S&T's Human Factors and Behavioral Sciences Division.