Retinal scans, available since 1985, are one of the most accurate performers, with low reject rates and nearly a zero percent false-accept rate. Users, however, are required to stand close to the device and focus on a target, which makes the systems unattractive. Iris eye measurement uses a camera to photograph the iris in the front of the eye. Unlike retinal vein patterns, which can change over time, the iris is unique and does not change during a person's lifetime. Like fingerprints, no two individual iris structures are alike.
Subjects can stand as far as three feet away from the camera.
In the area of behavioral biometrics are voice recognition technologies that provide telephone authentication. One, from Voton Corporation, Pleasanton, California, uses extraction and pattern-matching algorithms embedded on computer chips to analyze voices. Voice verification is favored by users. In addition, several states use voice recognition for parolees on home detention. Four new systems were introduced in 1996, making a total of 12 organizations working on advanced object-recognition techniques, including Harvard and MIT's Media Lab.