US Patent 10238305 Dynamic operation of optical heart rate sensors

An optical heart rate sensor includes an optical source configured to illuminate one or more blood vessels through a user's skin, an optical sensor configured to measure reflected illumination from the blood vessels, and one or more energy storage cells. A controller operates the optical source and optical sensor at a first rate of energy consumption during a first condition, and operates the optical source and optical sensor at a second rate of energy consumption during a second condition.