What many of us may be unaware of though is that an LED is also a photodiode, and can even be persuaded to generate usable quantities of power. [Voltative] takes a look at this phenomenon with a ...

Eindhoven University of Technology has made a photodiode with such low noise (<10-6mA/cm2 dark current) and wide dynamic range (<150dB), that it can optically detect a heartbeat at a distance of 1.3m.