A retina scanner is a biometric device that identifies individuals by analyzing the unique patterns of blood vessels in their retinas. This technology uses low-intensity infrared light to capture detailed images of the retina, which are then compared to stored templates for verification. Retina scanners are often used for security purposes, such as in access control systems for secure facilities or in smartphones for user authentication. They provide a high level of accuracy and are considered more secure than other biometric methods, like fingerprint scanning, due to the complexity and uniqueness of retinal patterns.