Editing Iris recognition (section)

== Operating principle ==
[[File:IriScan model 2100 iris scanner 1.jpg|thumb|A, now obsolete, IriScan model 2100 iris recognition camera]]
{{multiple image
 | total_width = 400
 | image1 = Pier2.3 SecuriMetrics iris scanner (cropped).jpg
 | image2 = Pier2.3 rear view.jpg
 | footer = Iris scanner PIER 2.3 ('''P'''ortable '''I'''ris '''E'''nrollment and '''R'''ecognition) from SecuriMetrics 
}}

First the system has to localize the inner and outer boundaries of the iris (pupil and limbus) in an image of an eye. Further subroutines detect and exclude eyelids, eyelashes, and specular reflections that often occlude parts of the iris. The set of pixels containing only the iris, normalized by a [[Rubber Sheet Model|rubber-sheet model]] to compensate for pupil dilation or constriction, is then analyzed to extract a bit pattern encoding the information needed to compare two iris images.

In the case of Daugman's algorithms, a [[Gabor filter|Gabor wavelet]] transform is used. The result is a set of complex numbers that carry local amplitude and phase information about the iris pattern. In Daugman's algorithms, most amplitude information is discarded, and the 2048 bits representing an iris pattern consist of phase information (complex sign bits of the Gabor wavelet projections). Discarding the amplitude information ensures that the template remains largely unaffected by changes in illumination or camera gain, and contributes to the long-term usability of the biometric template.

For identification (one-to-many template matching) or verification (one-to-one template matching),<ref>{{Cite web|url=https://www.msite.com/|title=MSite - Biometric Access Control for Construction Sites|website=www.msite.com}}</ref> a template created by imaging an iris is compared to stored templates in a database. If the [[Hamming distance]] is below the decision threshold, a positive identification has effectively been made because of the statistical extreme improbability that two different persons could agree by chance ("collide") in so many bits, given the high [[entropy]] of iris templates.