Daniel McDuff, S. Gontarek, Rosalind W. Picard

Abstract

We present a new method for measuring photoplethysmogram (PPG) signals remotely using ambient light and a digital camera that allows for accurate recovery of the waveform morphology (from a distance of 3m). In particular, we show that the peak-to-peak time between the systolic peak and diastolic peak/inflection can be automatically recovered using the second order derivative of the remotely measured waveform. We compare measurements from the face with those captured using a contact finger-tip sensor and show high agreement in peak and interval timings. Furthermore, we show that results can be significantly improved using orange, green and cyan color channels compared to the tradition red, green and blue channel combination. The absolute error in inter-beat-intervals was 26ms and the absolute error in mean systolic-diastolic peak-to-peak times was 12ms. The mean systolic-diastolic peak-to-peak times measured using the contact sensor and the camera were highly correlated, ρ = 0.94 (p<0.001). The results were obtained with a camera frame-rate of only 30Hz. This technology has significant potential for advancing healthcare.