Osram Opto Semiconductors has expanded its sensor portfolio for wearable products with the introduction of the SFH 7051 integrated optical sensor specifically designed for heart rate monitoring. Consuming very little power to maximize battery life, the sensor targets fitness trackers, smart watches and other wearables.
The SFH 7051 consists of a large-format photodiode and three green LEDs with a wavelength of 530 nanometers (nm). It is used for monitoring heart rate by measuring the volume of blood passing through blood vessels. With its green emission spectrum, the SFH 7051 is suited for measuring pulse rate at the wrist.
The green emitter chips are based on the latest high-efficiency UX:3 chip technology from Osram Opto Semiconductors. The sensor uses three of these chips so that they can operate at the optimum current of 20 milliamperes (mA). At this operating current, the efficiency of the emitters is particularly high, said Osram.
The SFH 7051 produces an optical output of 3 x 3.4 milliwatts (mW) at a current of 20 mA and a voltage of 3.2 V. With an area of 1.7 mm2, the photodiode is small enough to enable the sensor to be compact, but sensitive enough to provide the required signal quality, said Osram. The device offers a low capacitance of only 11 picofarads, which ensures short switching times and high measurement frequency.