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

Facial recognition analyzes the geometry and features of the face such as distance between eyes and nose shape, not blood vessels in the eye.

The retina is a light-sensitive layer at the back of the eye that contains a dense network of blood vessels forming a pattern unique to each individual. A retinal scanner uses low-intensity infrared light directed through the pupil to map this vascular pattern, making it one of the most accurate biometric identifiers available.

An iris scan captures the textured, colored ring surrounding the pupil, not the blood vessel layer behind it.

Signature kinetics measures the behavioral dynamics of how a person writes their signature, such as speed and pressure, and has no relation to the eye.