Iris recognition photographs the patterned ring around the pupil with near-infrared light and converts it into a mathematical template. A camera compares that template with an enrolled record. It is contactless and fast, but it needs a cooperative person positioned at the reader.
Iris recognition is not retina scanning. Retina imaging looks at blood vessels inside the eye and demands much closer alignment, which is why it stayed rare.
How the match is made
The reader isolates the iris, normalizes it for pupil size, and produces a template. Matching compares that template against enrolled records and returns a score, not a photograph.
Deployment questions to raise
Ask about enrollment time, performance with glasses or contacts, liveness checks against a printed image, and where the biometric template is stored.