Detecting pulse rate with a webcam

October 5, 2010

MIT Media Lab student Daniel McDuff, who collaborated on the pulse-monitoring system, demonstrates a version of the device built into a mirror that displays his pulse rate in real-time at the bottom. (Melanie Gonick)

MIT-Harvard graduate student Ming-Zher Poh has demonstrated a system that can extract accurate pulse measurements from ordinary low-resolution webcam imagery.

The system measures slight variations in brightness produced by the flow of blood through blood vessels in the face. Public-domain software is used to identify the position of the face in the image, and then the digital information from this area is broken down into the separate red, green and blue portions of the video image.

The system produced pulse rates that agreed to within about three beats per minute with the rates obtained from the approved monitoring device, and was able to obtain valid results even when the subject was moving a bit in front of the camera. In addition, the system was able to get accurate pulse signals from three people in the camera’s view at the same time.

Poh continues to work on developing the capability to get blood pressure and blood-oxygen measurements from the same video images. Extracting such data from optical imagery should work, he says, since conventional blood oxygen sensors already work by using optical detection, although they use a dedicated light source rather than ambient lighting.

More info: MIT news