A research team led by Dr. Ajay Kumar invents a 3-D fingerprint identification system of high efficiency and accuracy. Source: The Hong Kong Polytechnic UniversityA research team led by Dr. Ajay Kumar invents a 3-D fingerprint identification system of high efficiency and accuracy. Source: The Hong Kong Polytechnic UniversityA research team from The Hong Kong Polytechnic University (PolyU) has developed a system for 3-D fingerprint identification by adopting ground-breaking 3-D fingerprint minutiae recovery and matching technology, pushing contactless biometric technology into a new realm of speed and accuracy. The technology would be particularly useful in identification, crime investigation, immigration control, access security and forensic applications at an affordable cost.

Automated contact-based 2-D fingerprinting identification is commonly used by law enforcement agencies to identify people. However, contact-based acquisition of biometric scans by rolling or pressing fingers against a hard surface such as glass, silicon or polymer often results in partial or degraded images due to skin deformations, slippages or smearing. This produces images that are not fully useful for the identification. Non-contact fingerprint systems, on the other hand, avoid direct contact between the imaging sensor and the elastic surface of the skin, and can thus reduce inaccuracies due to problems associated with contact-based systems. Although there are emerging contactless 3-D systems, they tend to be very expensive and bulky due to their use of multiple cameras or structured lighting systems.

The research team led by Dr. Ajay Kumar, Associate Professor of the Department of Computing, overcomes the limitations of contact-based 2-D biometric scans and maximizes the advantages from the contactless 3-D systems.

The minutiae from the fingerprint ridges — such as ridge endings and bifurcations — are universally considered to be the most reliable of fingerprint details, ensuring that each fingerprint is unique. About 40-45 minutiae points can be recovered from a fingerprint, on average. The more minutiae points that are matched, the higher the confidence and reliability in the matching.

All fingerprinting systems commercially available today still recover the minutiae details in 2-D form, i.e., by locating the minutiae position and minutiae orientation in 2-D spaces. In Dr. Kumar's research, 3-D fingerprints are represented by minutiae height and minutiae orientation (i.e., gradient of minutiae ridges) in 3-D spaces on top of the representations in the 2-D spaces named above. This means the 3-D system can more uniquely represent fingerprints with the extra information given by describing two more measurements.

To achieve 3-D fingerprint minutiae recovery and matching, the team has shifted away from the standard use of multiple cameras in 3-D fingerprint identification systems to the innovative use of a single, low-cost digital camera coupled with a few LED light sources controlled by a computer. This allows researchers to efficiently acquire high-frequency information in 3-D fingerprints using advanced proprietary 3-D fingerprint template generation algorithms to recover 3-D minutiae features. With such 3-D minutiae details recovered, for the first time in the world, the PolyU research team has been able to accurately and reliably match 3-D fingerprints using its algorithms.

The compact size, its high accuracy of around 97 percent, reduced cost, faster processing time and reduced amount of equipment needed, render the system better than the currently used commercial 3-D counterparts. The contactless system is also more hygienic than contact-based 2-D systems, an added advantage in a world increasingly concerned about the inadvertent spread of disease. Given its ultimate practicality, the system is ripe for commercialization with several U.S. patents granted on its ground breaking technologies.

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