2024
Tezis
Imaging photoplethysmography (iPPG) is a very promising method for evaluating hemodynamic parameters in vivo, especially for visualizing and quantifying changes in organ perfusion during surgical operations. An important element of the iPPG optical system is polarization filtering, usually implemented by means of two crossed linear polarizers. One of these polarizers is installed after the illuminator and serves to illuminate the organ under study with incoherent linearly polarized light. Another polarizer is attached to the camera lens. Its transmission axis is adjusted to be orthogonal with that of the first polarizer. Since red blood cells (RBC) are highly anisotropic, after interacting with them, the light acquires elliptical polarization. Such polarization filtration reduces the effect of both skin specular reflections and motion artefacts on the detected iPPG signal, thereby increasing the signal-to-noise ratio. However, such a scheme has a practical disadvantage due to the need to adjust the polarization filter, which is not always feasible in an operating room. Here we propose to implement polarization filtering using only one optical element, namely a circular polarizer combined with a linear one.