Light of an LED can be used for heart rate monitoring in wearable applications. OSRAM Opto Semiconductors offers LEDs especially designed for the use in fitness tracking, health monitoring or similar applications such as the Firefly E1608.
This application note provides a short introduction into the general use of LEDs for wearable applications, with a focus on heart rate monitoring. Furthermore, it contains information on how to handle and process the Firefly E1608 for an appropriate implementation of the LED.
LEDs as a light source for heart rate monitoring
With each cardiac cycle, the heart pumps blood through the circulatory system of the human body. Arteries periodically dilate and constrict as blood flows through and the arteries increase or decrease in volume with every heartbeat. To detect this change in volume caused by the pressure pulse, the skin is illuminated with an LED and the amount of light either transmitted or reflected to a photodetector is measured afterwards (See Figure).