Continuous Real-time Heart Rate Monitoring from Face Images

A real-time monitoring method of heart rate (HR) from face images using Real-time Pulse Extraction Method (RPEM) is described and corroborated for the theoretical efficacy by investigating fundamental mechanisms through three kinds of experiments; (i) measurement of light reflection from face covered by copper film, (ii) spectroscopy measurement and (iii) simultaneous measurement of face images and laser speckle images. The investigation indicated the main causes of brightness change are both the green light absorption variation by the blood volume changes and the face surface reflection variation by pulsatory face movements. RPEM removes the motion noise from the green light absorption variation and the effectiveness is ensured by comparing with the pulse wave of the ear photoplethysmography. We also applied RPEM to continuous real-time HR monitoring of seven participants during office work under non-controlled condition, and achieved HR measured rate of 44 % to the number of referential ECG beats while face is detected, with RMSE = 6.7 bpm as an average result of five days.