Dynamic Exposure Controlling and Suppression for Highly Robust Remote-PPG in Fitness

Camera-based heart-rate monitoring in fitness is compromised by various factors like motion interference and illumination changes. Body motions induced by running significantly change the skin reflections and thus distort the photoplethysmographic (PPG) signals measured by a camera. In this work, we proposed a skin-reflection controlled auto-exposure system to improve the consistency of skin reflections during running. To further increase the motion robustness, we incorporated the continuous exposure time traces obtained from the camera sensor in PPG-extraction using the framework of discriminative PPG signature. Results show that the measurement coverage of heart rate (reference ±5 bpm) has been significantly improved from 67.85% to 76.60% from the fixed exposure time to the skin-controlled exposure time, and further improved to 81.12% by suppressing exposure changes in PPG extraction.