A photoplethysmographic imaging system with supplementary capabilities

We perform a temporal and spectral analysis of simulated and experimental photoplethysmographic signals. We obtain technical requirements for an advanced photoplethysmographic imaging system able to add photoplethysmographic waveform and oximetry maps to the conventional measurements. The imaging system is centered on measuring the pulsatile signals produced by diffuse reflectance on the inner layers of the skin. We consider controlled illumination conditions for the system, with visible and near infrared components. This work comprises backscattering evaluation, waveform analysis and spectral dependence of photoplethysmographic signal. We determine the resolution requirement for the system by evaluating the amplitude of the backscattered signal using Monte Carlo simulations. We determine the bandwidth limit for the signal acquisition by Fourier analysis from a set of plethysmographic waveforms. Finally, the spectral dependence of the system is obtained from experimental results. We establish the requirements for the photoplethysmographic imaging system, including the source, subject and detector conditions.