Which type of scan is used on the eye to measure the layer of blood vessels?

Facial recognition analyzes external facial geometry and surface features, not internal eye structures or blood vessels.

A retinal scan uses a low-intensity infrared light beam to capture the unique vascular pattern of blood vessels located in the retina at the rear of the eye. This blood vessel pattern is highly unique to each individual and remains stable over time, making it one of the most accurate biometric identifiers available. The scan specifically targets the blood vessel layer, which is the defining characteristic that distinguishes it from other eye-based biometrics.

An iris scan captures the unique texture and color patterns of the iris - the visible colored ring around the pupil - not the blood vessel layer located in the retina.

Signature kinetics is a behavioral biometric that measures the dynamics and rhythm of how a person signs their name, having no relation to any part of the eye.