Retina
Recognition
Retina scan based personal identification (PI) exploits the uniqueness of the vascular pattern of the retina in defining it's biometric. To date, the only vendor producing retina scan systems is EyeDentify, Inc. A retina scanner illuminates, through the pupil, an annular region of the retina (the retina is located inside and at the rear of the eye) with infrared (IR) light and records the reflected vasculature contrast information. The fovea centered annular region is approximately ten degrees off the visual axis of the eye [1]. Retina scanning is considered an exceptionally accurate and invulnerable biometric technology and is established as an effective solution for very high security environments. Even so, the technology is difficult to utilize because it requires well-trained, cooperative, and patient users for proper performance to be achieved. Because of this, and the fact that many people shy away from devices that interact with their eyes, retina scanning is thought to be fairly intrusive [2]. This is remarkable since no user contact is required for retina scanning.
In the 1930's two ophthalmologists discovered that each eye possesses a unique pattern of blood vessels. Later, in the 1950's, another physician studying maternal (identical) twins found their retina patterns unique as well [1] [2]. Moreover, barring disease and severe injury, the retina's vascular patterns are stable throughout one's lifespan. In retina scanning, the intensity of IR light reflected from an annular region of the retina is measured. One of the primary reasons for an annular scan (as opposed to some other, i.e. raster, etc.) is the reduction of light noise arising from corneal reflections. The width and diameter of a retina scanner's annular region of measurement is chosen to, given the worst-case scenario (a very small pupil), allow for the collection of an adequate set of data. In other words, there should always be sufficient reflected light and contrast detail to support the PI performance requirements.
Retina scanning based PI results in a highly accurate and secure system. Retina scanning possesses each of the four characteristics that make up a good biometric. It works well in both user verification and user identification modes. Additional advantages include small template size and good operational speed. However, retina scanning is generally perceived to be intrusive and unfriendly (even though no physical contact is required). This is due (in part) to: (a) the perception that eye scanning devices may be harmful, and (b) the devices are so difficult to use that high FRRs are the norm. In some applications high FRRs may be accepted as a necessary inconvenience for high security, but they would most likely be intolerable to the general public in a retail environment. Retina scanners are costly with respect to other physical security and/or biometric based systems. Still, if a PI system developer requires absolute security, even at the expense of high FRRs, this technology should be considered. Also, if a PI system requires user "identification mode" over large template databases, this technology may be one of only two options (the other is iris scanning) for the PI system developer.
[1] A. Jain, R. Bolle, S. Pankanti, editors, "BIOMETRICS Personal Identification in Networked Society," Kluwer Academic Press, Boston, 1999.[2] International Biometric Group, http://www.biometricgroup.com. Last accessed: 30 July 2001.