"Bloody Brilliant"! wrote someone in comments about this technology. Your heart rate could be measured by recording a video of your face. According to a published paper by Ming-Zher Poh in the IEEE Transactions on Biomedical Engineering, “During the cardiac cycle, volumetric changes in the facial blood vessels modify the path length of the incident ambient light such that the subsequent changes in amount of reflected light indicate the timing of cardiovascular events”. Then by applying Independent Component Analysis (ICA) on the color channels in video frames, it is possible to decompose the mixture of reflected signal with other sources of fluctuations in light. By tracking the tiny changes in reflected light that are not visible to the human eye, the heart rate can be calculated.
Based on this technology, they developed a new iPhone app that acts as a biosensor to measure your heart rate using your front iPhone camera. It is called Cardiio and here is how they describe it on their website:
“Every time your heart beats, more blood is pumped into your face. This slight increase in blood volume causes more light to be absorbed, and hence less light is reflected from your face. Using sophisticated software, your iPhone's front camera can track these tiny changes in reflected light that are not visible to the human eye and calculate your heart beat!”.
M.Z. Poh, D.J. McDuff and R.W. Picard, "Non-contact, automated cardiac pulse measurements using video imaging and blind source separation," Optics Express, vol. 18, no. 10, pp. 10762-10774, 2010. [link]
• M.Z. Poh, D.J. McDuff and R.W. Picard, "Advancements in non-contact, multiparameter physiological measurements using a webcam," IEEE Trans Biomed Eng, vol. 58, no. 1, pp. 7-11, 2011. [link]
• M.Z. Poh, D.J. McDuff and R.W. Picard, "A medical mirror for non-contact health monitoring," ACM SIGGRAPH Emerging Technologies, Aug 2011. [link]
Photo credit: cardiio.com