Heart Rate Monitoring Using Infrared Imaging

Image-based photoplethysmography (iPPG) is a non-invasive contactless optical measurement method that has been used for heart rate monitoring. In this technology, a light source illuminates the skin's surface, and a photodetector measures the volumetric variations of blood circulation. A light source outside the visible spectrum had to be employed to utilize iPPG without the blinding effect of the high-intensity visible light source. In this pilot study, we evaluated a contactless continuous pulse rate measurement using infrared (IR) light and a high-speed camera. The IR light illuminates the facial region, and the high-speed camera, capable of capturing video frames at a high frame rate, records the reflected light, extracting iPPG signals from the captured video frames. The developed algorithm was tested in ten experiments under two conditions when the participants rested and exercised. A wrist-worn pulse oximeter was used as a reference. The article explains the image extraction and signal processing implementation process and demonstrates the results of a signal processing pipeline. In addition, the results of detected pulse rates were compared to the pulse oximeter measurements.