Internal fingerprint sensor enables more accurate ID
a ‘master template’ from which the surface regrows when it is damaged,” Auksorius said.
The new sensor uses a special variant of an imaging technology called optical coherence tomography (OCT). OCT is already used for medical imaging and works by analyzing an interference pattern created when a beam of light that travels through a biological sample, like a finger, is recombined with a reference beam of light.
Standard OCT systems gather 3D data and often require sophisticated lasers systems and light detectors, which can get expensive. Auksorius and Boccara simplified their system by using a modified version of OCT called full-field OCT, or FF-OCT, which was invented by their laboratory and developed in the early 2000s.
The main advantage of the FF-OCT system is that it can take a 2D image of the fingerprint directly, saving time and making the data processing simpler and cheaper. Because not everyone’s internal fingerprints are located at the same depth, the researchers also developed a method to first take an image of the fingertip at an angle. The first image was used to determine the depth of the internal fingerprint, and then a second image of the fingerprint itself was taken.
The system can also image sweat pores, which provide an additional means of identification.
Currently the system is about shoebox size and Auksorius is working to further shrink it. The biggest and most expensive element in the system — a specialized infrared camera — cost about $40,000, but the team recently acquired comparable images using a camera less than one fifth the cost. Auksorius estimates that a complete device using the new camera could be constructed for less than $10,000. While the price is still significantly higher than standard fingerprint sensors, Auksorius predicts that the new device could find a market dedicated to imaging problematic fingerprints or in areas where security is a particular concern.
“We showed that the internal fingerprints could be imaged with a relatively simple and inexpensive system,” Auksorius said. “Furthermore, recent results with the new camera show that the system can potentially be a commercially viable solution.”
The team has plans to soon test the device in Turkey, where 100 people will have their fingerprints scanned. They are also working to further improve the imaging speed and depth capabilities of the system.
— Read more in Egidijus Auksorius and A. Claude Boccara, “Fingerprint imaging from the inside of a finger with full-field optical coherence tomography,” Biomedical Optics Express 6, no. 11 (2015): 4465-71 (doi: 10.1364/BOE.6.004465)
