Fundamental limits of light-wave sensing for non-contact respiration monitoring.

An experimental testbed was constructed to rigorously assess the fundamental limits of light-wave sensing-an economic, non-contact vitals monitoring approach previously reported. We improve the testbed using lock-in amplification and demonstrate that a photodetector and a commonplace array of infrared LEDs are sufficient to detect respiratory motion and quantify respiration rate up to 2.5 meters away.