Wearable Photoplethysmographic Sensor Based on Different LED Light Intensities

Wearable photoplethysmographic sensors in the form of wristbands and watches have become increasingly popular in mobile healthcare. We propose a technique to cancel motion artifacts by using two reflective pulse signals from a single green LED, switched by a microcontroller between high and low light intensities. We accurately estimate motion artifacts by applying differential measurement and common-mode rejection. The performance was assessed for four different motion artifacts: artificial white noise, artificial color noise, and vertical/horizontal random movements of a hand. Under each different condition, we accurately cancelled out motion artifacts.