As far back as the 1930s, in the context of biometric research, people recognized that the blood vessels at the back of the eye might be unique in pattern and offer a means of individual identification. Retinal scanning technology has been around as an alternative means for personal identification since the mid-1970s. Retinal scanning analyzes the layer of blood vessels at the very back of the eye. These blood vessels form a pattern that is totally random and unique, just like fingerprints. Tales abound about various uses of dead people's fingers being used to falsify fingerprints as though the individual were still alive. There is no known way to replicate a retina, however, and the retina of a dead person would deteriorate rapidly, eliminating the need to prove the retina is from a live person.
Retinal scanning involves the use of a low-intensity light and an optical coupler to read the blood vessel patterns. There is a certain amount of discomfort in that the individual who is being scanned must focus on a particular point within the optics of the scanner and remain focused for approximately 10 seconds. Naturally, those who wear glasses have to remove them for the scanning.
Minimal discomfort aside, retinal scanning has been used almost exclusively in high-risk security areas such as military installations. The state of Illinois uses retinal scans to prevent welfare fraud. The Japanese use retinal scans at automated teller machines.
New uses appear to be on the horizon. For instance, media reports have indicated that retinal scans are being considered for student identification. This is due to their accuracy and mobility; obviously, there is no real concern that students will be likely to bring in dead fingers to attempt to falsify their true identity. Advantages include eliminating the social stigma associated with certain programs such as receiving free lunch at school. By giving everyone a retinal scan, the haves could be distinguished from the have-nots in an unobtrusive manner. The device could also be used in the library and at social events to keep outsiders away. Similarly test takers could be verified as to identity quickly and easily; no more paid test takers for college or graduate school entrance exams.
One problem with retinal scans is that the retina changes over time. This necessitates periodic updates to the database to keep the scanning current. As an alternative to retinal scans the iris of the eye has been used. The iris does not change. Iris scans video the colored area of the eye and record the unique pattern present. Iris scanning allows the individual being scanned to be as far as several feet away from the device. Obviously, cataracts and lens replacement surgeries would have to be considered, but these conditions affect a relatively small proportion of the population.
Alternatives to retinal scanning include fingerprint scanners, which are in use around the world. These rely on a template being created with the first scan. All subsequent scans are compared against the template on file. To eliminate the possibility of a fake or dead finger, infrared light can be used to verify that there is a pulse within the finger itself.
According to an April 12, 2004, article in Business Week, experts at the University of Leicester have developed a high-speed identification system based on the shape and features of the ear. A preliminary study of 1,500 ears has shown that no two ears are identical. The study did not mention whether identical twins were part of the group. If the ear is unique, it would be expected that the ears of "identical" twins would be different.
The progression from fingerprints to other physical characteristics for purposes of individual identification speaks to ongoing efforts to come up with a simple, direct method that defies compromise. Retinal scan appears to be the most likely candidate. Of course, the possibility of someone wearing contact lenses that display the retinal pattern of another individual comes to mind. That may be a meaningless concern, but criminal minds sometimes come up with ingenious ways to "beat the system."
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