Yi He

TL;DR: In this paper, the authors describe a heart rate sensor based on optical measurements of color response of human blood, which can include light source circuitry including a first light emitting diode (LED), a second LED to output a second source light signal to the target measurement site, a first current pulse driver communicatively coupled to the first LED to modulate the first source light signals output from the second LED at a first predetermined frequency, and a second current pulse driven by the driver at a second predetermined frequency.