Robust Imaging Photoplethysmography in Long-Distance Motion

Imaging photoplethysmography (IPPG) enables contactless physiological parameters monitoring using a regular video camera, which led to an increasing interest in video health monitoring. However, classical IPPG is unable to accurately measure heart rate over a long-distance motion. In this paper, an IPPG heart rate detection framework is proposed based on an adaptive-zoom system called adaptive-zoom IPPG (AZIPPG). It uses an automatic zoom lens to maintain the size of the sensitive area during long-distance motion. The data gathered from AZIPPG were compared with the output of blood volume pulse (BVP) devices and a classical IPPG system. The experimental results showed that AZIPPG achieved high accuracy and correlation in different environments featuring subjects engaged in static and long-distance walking. Actually, AZIPPG eliminates dramatic changes in the ROI, it also introduces image blurring. In this report, the presented theoretical and experimental results indicate that defocused image blurring dose not significantly affect the IPPG's intensity. The pulse data extracted from AZIPPG were comparable to those obtained from the PPG signal of a conventional BVP device. These findings may potentially advance progress in personal health care and telemedicine.