Facial thermography detects heat patterns created by the branching of blood vessels and emitted from the skin. These patterns, called thermograms, are highly distinctive. Even identical twins have different thermograms. Developed in the mid-1990s, thermography works much like facial recognition, except that an infrared camera is used to capture the images.
The advantages of facial thermography over other biometric technologies are that it is not intrusive — no physical contact is required — every living person presents a usable image, and the image can be collected on the fly. Also, unlike visible light systems, infrared systems work accurately even in dim light or total darkness. Identification systems using facial thermograms were undertaken in 1997.