The first approach simply involves measuring pixel values of specific points on the person's face, which are the compared to values in a database of scans of sober and inebriated people. Given that alcohol causes dilation of blood vessels in the surface of the skin hot spots on the face can be seen in the thermal imaging scans, which can be classified as drunk or sober regions. Similar technology has been used at international borders and elsewhere to ascertain whether a person was infected with a virus, such as flu or SARS.
In their second approach, the team assesses the thermal differences between various locations on the face and evaluates their overall values. They found that increased thermal illumination is commonly seen in the nose in an inebriated individual whereas the forehead tends to be cooler. This second system relies on the algorithm "understanding" what different parts of the face are present in the thermal image. The two techniques working in parallel could be used to quickly scan individuals entering public premises or attempting to buy more alcohol, for instance. The team points out, however, that the second technique does not need a thermal image of the sober person to determine whether that individual has been drinking.
AlphaGalileo Foundation thanks to Jon Reed for pointer