Explainer: Facial Thermography
In the mid-1990s, it was demonstrated by scientist Francine J. Prokoski that facial thermograms are unique to individuals, and that methods and systems for positive biometric identification using facial thermograms could be developed.
Thermograms, generally, are visual displays of the amount of infrared energy emitted, transmitted, and reflected by an object, which are then converted into a temperature, and displayed as an image of temperature distribution.
Infrared energy, and infrared light itself, is electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at 700 nanometres (nm) to 1 mm. This range of wavelengths corresponds to a frequency range of approximately 430 THz down to 300 GHz, and includes most of the thermal radiation emitted by objects near room temperature.
Infrared light is emitted or absorbed by molecules when they change their rotational-vibrational movements. These movements can be observed through spectroscopy, which is the study of the interaction between matter and radiated energy.
Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by way of a prism. Later the concept was expanded greatly to comprise any interaction with radiative energy as a function of its wavelength or frequency. Spectroscopic data is often represented by a spectrum, which is a plot of the response of interest as a function of wavelength or frequency.
Facial thermography works by detecting heat patterns created by the branching of blood vessels that are emitted from the skin. These patterns, known as thermograms, are highly unique. As a consequence, identical twins have different thermograms.
Thermography works very much like facial recognition, except that an infrared camera is used to capture the images. Prokoski however found that facial thermogram technology capability is inherently more accurate and more robust over varying lighting and environment conditions than is the use of video images.
The technology involves the use of biosensor data for uniquely and automatically identifying individuals. Due to the connectedness of the physiological systems of the human body, elemental shapes can in general be derived from any biological sensor data which can be presented as an image. The elemental shapes and their locations provide an identification capability.
Biosensors which produce very detailed localized data, such as high-resolution infrared imagers, can result in unique identification of an individual from the determination of elemental shapes and their distribution. The market for such devices and services includes all facilities which seek to restrict access to physical areas, distribution systems or information files.
Thermograms as a mechanism of biometric identification are advantageous since the technology is non-intrusive. While not used prolifically, electronic thermography is increasing used as non-ionizing, noninvasive alternative for medical diagnostics. It is believed that vascular heat emissions that present on the human face can provide physiologic indicators of underlying health or disease. General thermography has been used to attempt to diagnosis breast cancers, through efficacy of using the technology for that purpose has been questioned as scientifically suspect.