Developed in the 1980s, retinal scanning is one of the most well-known biometric technologies, but it is also one of the least deployed.
Retinal scans map the unique patterns of a person’s retina. The blood vessels within the retina absorb light more readily than the surrounding tissue and are easily identified with appropriate lighting.
A retinal scan is performed by casting an unperceived beam of low-energy infrared light into a person’s eye as they look through the scanner’s eyepiece. This beam of light traces a standardized path on the retina.
Once the scanner device captures a retinal image, specialized software compiles the unique features of the network of retinal blood vessels into a template. Retinal 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 is typically one of the smallest of any biometric technology.
Retinal scan is a highly dependable technology because it is highly accurate and difficult to spoof, in terms of identification. The technology, however, has notable disadvantages including difficult image acquisition and limited user applications. Often enrollment in a retinal scan biometric system is lengthy due to requirement of multiple image capture, which can cause user discomfort. However, once user is acclimated to the process, an enrolled person can be identified with a retinal scan process in seconds.
Retinal scan technology 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 a 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.
Because retinal blood vessels are more absorbent of log-energy infrared light than the rest of the eye, the amount of reflection varies during the scan. The pattern of variations is converted to computer code and stored in a database.
Retinal scans should therefore not be confused with another ocular-based technology, iris recognition, which is described as the process of recognizing a person by analyzing the random pattern of the iris.
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 retinal scan technology 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. – Rawlson King