Remote Physiological Signal Acquisition and Analysis: Contactless Photoplethysmography and Specular Reflection Vascular Imaging

In this thesis, I describe the remote acquisition of physiological signals using contactless remote photoplethysmography (rPPG), and the novel specular reflection vascular imaging (SRVI). rPPG is a contactless extension of reflection photoplethysmography, which captures the variations in skin optical properties due to changes in the primary light absorber in blood - hemoglobin. I used rPPG (embodied in a consumer smartphone) to investigate various physiological phenomena, including ischemia, Mayer waves, venous outflow, and characteristics of glabrous vs. non-glabrous skin. Despite its value, photoplethysmography is limited by sensitivity to melanin concentration, and therefore has performance limitations in acquisition from subjects with darker skin tones. To address this limitation, SRVI was proposed to leverage specular reflection for acquisition of skin displacements caused by mechanical pulsations in blood vessels. SRVI is insensitive to melanin concentration since acquisition is restricted to the very surface of the skin. SRVI was capable of capturing carotid artery and jugular vein waveforms.