The iris is an internal organ of the eye — perhaps the only internal organ of the body that is routinely visible from outside — and its patterns are resolvable with good video cameras from distances of up to about a meter. The iris is located behind the cornea of the eye, and behind the aqueous humour, but in front of the lens. Though we have other biometric traits we go for iris technology because of its uniqueness. This is because iris patterns have a high degree of randomness in their structure. This is what makes them unique.

The main principle of this system depends on the algorithm which encode the iris pattern into an abstract mathematical description called an "Iris Code," which is the bar-code like bit stream This process relies upon two-dimensional wavelets (mathematical functions that are like restricted Fourier components, i.e. sine waves multiplied by Gaussian envelopes to give them locality) which is given as follows

The result of the wavelet analysis is that any piece of an iris can be said to have a certain phase. The phase coordinates of every part of the iris are quantized to just two bit accuracy — i.e. only the identity of a quadrant of the complex plane is encoded as the representation for each small piece of structure seen in the iris. This "phase sequence" allows an iris pattern to be encoded in a total of 512 bytes worth of information. Whenever a person presents his/her eye to a camera, its Iris Code is computed within a second or less, and then this is compared with all previously enrolled Iris Codes in the relevant database to see whether any of them match. An important point is that the person does not need to assert any identity; the algorithms are powerful enough (and fast enough) to discover their identity, if they have been seen before and enrolled. The speed of database search is about 100,000 Iris Codes per second.

This ability to be recognized without having first to assert an identity — e.g. by swiping a card, or by typing in a name or a PIN number — is one potential advantage of iris identification for persons who have limited use of arms or hands. This "hands-free" use of iris recognition is possible because the probability of False Matches is so low i.e. about 1/1,200,000 so that the algorithms can "afford" to search large databases exhaustively, rather than just answering a single yes/no question about a claimed identity. In many millions of Iris Code comparisons that have been done in tests by independent laboratories (e.g. the UK’s NPL Labs), so far there has never been a single False match reported.

As with almost every new technology that seeks to find its place in everyday life, iris recognition has both the potential to be a convenience enhancer (including an access enhancer), but also the potential to be an obstacle or excluder if improperly configured or installed without consultation and guidance from disabled persons. Because it allows hands-free, automatic, rapid and reliable identification of persons, it can facilitate access for persons unable to engage in the standard mechanical transactions of access.

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