The setup for carrying out experiments is shown in Fig. 1. In our experiments, the facial area of a subject was illuminated by an illumination system which consists of two similar light-emitting diodes (LED) of the model H2A3-530 by Roithner LaserTechnick, operating at a wavelength of 530 nm. The optical power of both LEDs was 60 mW, providing an illuminated area of 30×60 cm2 at a distance between the subject face and video cameras, which was about 2 m. The duration of each measurement was 15 s. The illuminating light was linearly polarized. The direction of illumination was at a small angle with the direction of observation provided by the video systems. For video recording of the light reflected from the subject’s face we simultaneously used two video systems: a digital monochrome camera for blood pulsation imaging and a digital infrared camera for thermography imaging. A digital infrared camera system (FLIR A315, FLIR Systems Inc., USA) was used for thermography imaging. Parameters of the infrared camera system during recording were the following: spatial resolution 320×240 pixels, temperature accuracy measurement 0.05 °C, and temporal resolution 9 Hz.
English : headache