Biometrics - How Does it Work?

In Hitachi's system, the finger is placed on a contact-less scanner. The system works by the transmission of near infra-red light into the finger from a set of LEDs in the scanner. The harmless near infra-red light penetrates into the finger and is partially absorbed by the haemoglobin in the bloodstream of the capillaries in the finger.

The resultant vein patterns, invisible to the naked eye, can be viewed through an image sensor sensitive to near-infrared light. Near-infrared light passes through the tissues of the human body and is blocked by pigments such as hemoglobin or melanin. As hemoglobin exists densely in blood vessels, near-infrared light shining through causes the veins to appear as dark shadow lines in the captured image.

This creates an image that can be captured by a CCD camera. The resultant well defined image is processed according to a special algorithm to create a finger vein pattern that is digitized and compressed ready for storage.