Abstract

Photoplethysmography (PPG) is a promising optical measurement method for daily patient monitoring for a wide range of physiological parameters. Nevertheless, this measurement technique remains sensitive to external disturbances, inter/intra- subject physiology, and sensor configuration. In order to study the behavior of these optical signals, we report an original bench based on PPG measurement and Diffuse Reflectance Spectroscopy (DRS). Thanks to this setup, we are able to investigate several sensor configurations in terms of source-detector distances and wavelengths at kHz acquisition rate. These measurements are multi-wavelength in the visible and near infrared range, synchronized and performed on up to eight configurable source-detector distances (three reported in this paper). An optical calibration suited for comparative measurements is also implemented. We additionally present the first results obtained on a representative and dynamic medium. This study highlights the dependence between the optical signal measurement and the configuration of the sensor. These first results demonstrate the interest of the development of our optical bench to study in depth the complex processes occurring in heterogeneous scattering environments such as biological tissues. This work paves the way for robust, quantitative, accurate and continuous monitoring of vital signs based on PPG, and opens perspectives for physiological measurements on persons and sensor development.

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