Invisible – but Perceptibly Perfect

OSRAM’s new SFH 7060 sensor produces invisible light – at least to humans. But that’s all it needs to work miracles. Its optical sensor is equipped with five light-emitting diodes and a highly sensitive photodiode, enabling it to measure bodily functions such as pulse and blood oxygen levels. And it does all that with exceptional signal quality and low energy consumption. It’s no wonder that the sensor is ideal for smartwatches and fitness bracelets.

A Whole New Level of Fitness Tracking

How does it take measurements? The sensor’s light-emitting diodes send light to the skin. If it meets with blood and the surrounding tissue, a certain amount of the light is absorbed. The amount of light not absorbed is reflected back to the sensor.

The photodiode can measure how much light comes back, making it possible to determine heart rate, pulse, and oxygen saturation.

Figure 1
The sensor SFH 7050 is emitting green, red or infrared light, which irradiates skin or tissue and is absorbed or reflected. The amount of the reflected light registered by the detector varies with the amount of blood in the arteries (photoplethysmography). The measurement is carried out with green light on the wrist, with red or infrared wavelengths at the finger.

Figure 2
The periodicity of the detector signal I + corresponds to the pulsation of the amount of blood in the arteries. The ratio of the minimum and maximum signal values (Imin/Imax) is relevant for the determination of the oxygen saturation of the blood (pulse oximetry).

Figure 3
The absorption behavior of blood – or more precisely of the blood pigment hemoglobin (Hb) – changes at oxygen uptake (oxyhemoglobin or HbO2).  By measuring the absorption of red and infrared light, the oxygen saturation of the blood can be determined.

Three sensor variations are currently available: one specializing in measuring heart rate and pulse (SFH 7051) and two with different capacities for measuring pulse, heart rate, and blood oxygen levels (SFH 7050, SFH 7060).

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