Osram Opto Semiconductors GmbH of Regensburg, Germany has expanded its portfolio of optical sensors for the optical measurement of pulse rates and the oxygen saturation level of blood.
Offering what is claimed to be excellent signal quality and low energy consumption, the main market segment for the new SFH 7060 includes wearable mobile devices such as smart watches and fitness armbands for continuously monitoring fitness levels. The integrated optical sensor contains five light-emitting diodes with three different wavelengths and one high-sensitivity photodiode.
Picture: The new integrated SFH 7060 optical sensor for measuring pulse rate and blood oxygen levels, containing a photodiode, three green LEDs, one red LED and one infrared LED.
As a development of the SFH 7050 optical sensor (introduced in fall 2014), the SFH 7060 performs the same functions but with improved power consumption and signal quality. The SFH 7060 consists of three green LEDs, one red LED, one infrared LED and one large-format photodiode, which is optically separated from the emitters by an opaque barrier. It works by shining light into the skin. Different amounts of this light are absorbed by blood and the surrounding tissue. The light that is not absorbed is reflected to the detector. Absorption measurements with different wavelengths are used to determine the pulse rate and the saturation level of oxygen in the blood.
Efficient and reliable pulse measurements
Green light is best for measuring the pulse at the wrist. The SFH 7060 is equipped with three green LEDs with a wavelength of 530nm based on Osram's latest high-efficiency UX:3 chip technology. At their optimum operating point at a current of 20mA, they are particularly efficient and typically deliver an optical output of 3.4mW at a voltage of 3.2V per chip, says the firm. The higher light output, compared with the SFH 7050, results in better signal quality and more stable pulse measurements, it adds. The lower power consumption also means longer battery life in the device.
More accurate blood oxygen measurements
Oxygen saturation in the blood is calculated from the different absorption rates of red (660nm) and infrared (940nm) light. The quality of the measurements depends to a large extent on the achievable signal-to-noise ratio and on the linearity of the photodetector. The integrated photodiode, with its active surface of 1.3mm x 1.3mm, meets these requirements, says Osram. In addition, the distance between the two transmitters and the photodiode in the SFH 7060 is greater than in the SFH 7050, so the light penetrates deeper into the skin before it is reflected to the detector, leading to more stable signals and a better signal-to-noise ratio. As in the case with its predecessor, the wavelength of the red transmitter is specified with a very narrow tolerance of ±3nm to ensure accurate measurements.
The new sensor is Osram Opto's latest addition to its portfolio for fitness tracking applications, designed to meet all the latest requirements. "The market for fitness tracking is growing at a rapid pace, and some of the requirements that the components have to meet are also changing rapidly," says product marketing manager Christoph Goeltner. "We are working very closely with our customers so that we are always in a position to offer suitable products continuously and quickly." Users can now choose between a highly efficient solution designed for pulse rate measurements, an extremely compact sensor for combined pulse rate and blood oxygen measurements, and a slightly larger version with the same features but with significantly improved functionality, says the firm.
