Self-contained, passive, non-contact, photoplethysmography: Real-time extraction of heart rates from live view within a Canon Powershot

Abstract

Photoplethysmography (PPG) is the detection of blood flow or pressure by optical means. The most common method involves direct skin-contact measurement of light from an LED. However, the small color changes in skin under normal lighting conditions, as recorded by conventional video, potentially allow passive, non-contact, PPG. A variety of methods have been applied to extract heartrate from such a video. In another paper submitted to this conference by the same authors, a new processing algorithm based on autocorrelation is shown to be effective without needing extensive video preprocessing to enhance the signal. That method was implemented using floating-point arithmetic in MatLab to analyze complete videos. However, the algorithm’s structure suggested that it might be possible to create a simplified, integer-only, approximation that is entirely incremental: updating a heart rate estimate as each frame is captured. This new, simplified, incremental algorithm allows a reprogrammed Canon PowerShot camera to function as a stand-alone, passive, non-contact, PPG device. The incremental integer algorithm and implementation are explained and evaluated in this paper.