Abstract
Camera-based photoplethysmography (cbPPG) is a novel measuring technique that permits the remote acquisition of cardiovascular signals using video cameras. Research still lacks in fundamental studies to reach a deeper technical and physiological understanding. This work analyzes the employment of polarization filtration to (i) assess the gain for the signal quality and (ii) draw conclusions about the cbPPG signal's origin. We evaluated various forehead regions of 18 recordings with different color and filter settings. Our results prove that for an optimal illumination, the perpendicular filter setting provides a significant benefit. The outcome supports the theory that signals arise from blood volume changes. For lateral illumination, ballistocardiographic effects dominate the signal as polarization's impact vanishes.
Highlights
Camera-based photoplethysmography is an optical measuring technique that allows the remote acquisition of cardio-respiratory signals using common video cameras [1, 2]
We evaluate the benefit of polarization filtration for Camera-based photoplethysmography (cbPPG) using wavelengths in the red, green and blue color range
We evaluated the differences between the three wavelengths for each region of interest (ROI) and filter setting
Summary
Camera-based photoplethysmography (cbPPG) is an optical measuring technique that allows the remote acquisition of cardio-respiratory signals using common video cameras [1, 2]. The underlying principle is similar to the one in regular photoplethysmography (PPG) where backscattered light from superficial skin layers, which is modulated by physiological processes, is captured and converted into signals [3]. CbPPG and PPG function with light in the visible and near-infrared spectrum. In contrast to PPG, cbPPG can be operated without a dedicated light source using ambient light [4, 5]. CbPPG could be applied in contact with the skin, we give priority to the remote setting in which the subject is not disturbed by any instrumentation
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