The Iris
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.
