Thermal Infrared Imaging-Based Computational Psychophysiology for Psychometrics

Abstract

Thermal infrared imaging has been proposed as a potential system for the computational assessment of human autonomic nervous activity and psychophysiological states in a contactless and noninvasive way. Through bioheat modeling of facial thermal imagery, several vital signs can be extracted, including localized blood perfusion, cardiac pulse, breath rate, and sudomotor response, since all these parameters impact the cutaneous temperature. The obtained physiological information could then be used to draw inferences about a variety of psychophysiological or affective states, as proved by the increasing number of psychophysiological studies using thermal infrared imaging. This paper presents therefore a review of the principal achievements of thermal infrared imaging in computational physiology with regard to its capability of monitoring psychophysiological activity.

Figure 1

Pulse computation from thermal imaging data. (a) Collection point on the carotid arteriovenous complex, the frontotemporal region, and the wrist of the subject. (b) Temperature profile after removing frequency signals lower than 0.67 Hz (40 bmp) and higher than 1.67 Hz (100 bmp) (adapted from [9]).

Figure 2

Thermal imaging data. (a) Thermal image showing the thermal track of the airflow. (b) Raw temperature versus time profile for a region of interest close to the nose tip.

Figure 3

From the thermal IR image series to the cutaneous blood flow (CBF) images derived from thermal IR imagery. The series of IR images is converted into a series of IR-CBF images by applying computational models for bioheat exchange (adapted from [32]).

Figure 4

Computation of cutaneous blood perfusion from thermal image series. (a) Thermal image of healthy hand; (b) cutaneous perfusion computed from thermal imagery (in arbitrary units); (c) laser Doppler image (in arbitrary units). The overall distributions appear to be consistent, both images similarly showing the same high-perfusion and low-perfusion regions.

Figure 5

Emotional sweating and sudomotor response. The delivery of emotional pressure or stress stimulation (b) changes the rest of the (a) temperature distribution. The spotted dark signature is associated with the activity of the sweating glands.