You can check a person’s vital signs — pulse, respiration and blood pressure — manually or by attaching sensors to the body. But a student in the Harvard-MIT Health Sciences and Technology program is working on a system that could measure these health indicators just by putting a person in front of a low-cost camera such as a laptop computer’s built-in webcam. So far, the graduate student has demonstrated that the system can indeed extract accurate pulse measurements from ordinary low-resolution webcam imagery. Now the student is working on extending the capabilities so it can measure respiration and blood-oxygen levels. 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.
In tests, the pulse data derived from this setup were compared with the pulse determined by a commercially available FDA-approved blood-volume pulse sensor. The big challenge was dealing with movements of the subject and variations in the ambient lighting. But researchers were able to adapt signal-processing techniques originally developed to extract a single voice from a roomful of conversations, a method called Independent Component Analysis, in order to extract the pulse signal from the ‘noise’ of these other variations. 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.
More information:
http://web.mit.edu/newsoffice/2010/pulse-camera-1004.html
More information:
http://web.mit.edu/newsoffice/2010/pulse-camera-1004.html