Retina-scan technology utilizes the distinctive characteristic of the retina – the surface on the back of the eye that processes light entering through the pupil – for identification and verification. Developed in the 1980s, retina-scan is one of the most well-known biometric technologies, but is also one of the least deployed.
Retina-scan devices are used exclusively for physical access applications and are usually used in environments requiring exceptionally high degrees of security and accountability such as high-level government, military, and corrections applications.
Image Acquisition
Since the retina is small, internal, and difficult to measure without the proprietary hardware and camera systems specifically designed for retina imaging, image acquisition is a very difficult process.
In order for the unit to acquire retina images, the user first positions his or her eye very close to the unit’s embedded lens, with the eye socket resting on the sight. Beneath the lens, within the device itself, is an imaging component consisting of a small green light against a white background. The user views this light through the lens; when triggered, the light moves in a tight circle, measuring the retinal patterns through the pupil. In order for a retinal image to be acquired, the user must gaze directly into the lens, remaining perfectly still while focusing on the imaging component. Any movement defeats the image acquisition process and requires that the imaging process be triggered again. A small camera captures an image of the retina through the pupil. The acquisition of a single retina image takes 4 to 5 seconds under ideal condition.
During enrollment, between three and five acceptable images must be acquired. Since the first one or two images acquired are almost invariably rejected due to excessive movement, the enrollment process can be relatively lengthy. Including the time to trigger the process, respond to system prompts and acquire sufficient images, enrollments can easily take over 1 minute. Many users cannot enroll at all, even after several minutes. On the other hand, it is possible for highly acclimated users to be identified within 2 to 3 seconds – the identification process is much quicker.
Distinctive features
The retina’s intricate network of blood vessels is a physiological characteristic that remains stable throughout the life of a person. As with fingerprints and iris patterns, genetic factors do not determine the exact pattern of blood vessels in the retina. This allows retina-scan to differentiate between identical twins and provide robust identification. The retina contains at least as much individual data as a fingerprint, but, unlike a fingerprint, is an internal organ and is less susceptible to either intentional or unintentional modification. Certain eye-related medical conditions and diseases, such as cataracts and glaucoma, can render a person unable to use retina-scan technology, as the blood vessels can be obscured.
Template Generation and Matching
Once a device captures a retinal image, the software compiles the unique features of the network of retinal blood vessels into a template. Retina-scan algorithms require a high-quality image and will not let a user enroll or verify until the system is able to capture an image of sufficient quality. The retina template generated by the originator of the technology is a mere 96 bytes, one of the smallest of any biometric technology.
Retina-scan has robust matching capabilities and is typically configured to do one-to-many identification against a database of users. However, because quality image acquisition is so difficult, many attempts are often required to get to the point where a match can take place. While the algorithms themselves are robust, it can be difficult process to provide sufficient data for matching to take place. In many cases, a user may be falsely rejected because of an inability to provide adequate data to generate a match template.
Compiled By: Chaudhary Amit V.
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