More recently iris patterns have been used for identification purposes.The iris is thought to be the ideal part of the human body for biometric identification:
- It is well protected from damage and wear unlike fingerprints which can be altered over time
- The iris is flat, compared to the eyeball, and it's diameter is consistent from eye to eye. This makes measuring the patterns of the iris easier since the size itself falls within acceptable limits
- The iris has a very fine texture which is randomly created during embryonic development. As with fingerprints even twins have different iris patterns
- An iris scan is easy to accomplish as well established photographic techniques are all that is required. This also eliminates any direct physical contact between the person being scanned and the scanning equipment
- Algorithms already exist that virtually guarantee a zero percent false identification rate. This system is John Daugman's IrisCode
- Though changes in iris color can occur the patterns themselves are quite stable over many decades
As with the iris, the advantage with facial recognition is that standard photographic techniques can be used to record the human face. With the photograph an operator can extract the coordinates of facial features such as the distance between the center of pupils, the inside metric from the corners of eyes, the outside corner of eyes, the pattern of the hairline and the like.
From these measurements a list of twenty distances are calculated and placed into a set of formulas.
There are inherent problems with this though in that it is unlikely that any two pictures would be the same. Head rotation, tilt, lean, and scale all play a part. To counter these problems each set of distances is standardized to represent the face in a full frontal orientation. To get to this point of standardization computer programs first try to determine tilt, lean, and rotation and then, using angular calculations, determine the coordinates of the twenty points described above.
The advantages are;
- The subject is much less likely to know that their face is being scanned
- It is non-intrusive to the subject
- Lends itself to public settings such as airports and train stations.
- Is much non-intrusive to the public at large.