Ams announced the launch of a new photodiode called TOPLED D5140 SFH 2202. Compared with existing standard photodiodes, this photodiode has superior performance, higher sensitivity to visible light in the green part of the spectrum, and also better linearity.These improved features significantly reduce the impact of ambient light interference, resulting in higher quality optical signals received, allowing smartwatches, activity trackers, and other wearables to more accurately measure heart rate and blood oxygen saturation (SpO2).
● The new TOPLED D5140 SFH 2202 photodiode is more sensitive and has excellent linearity than the standard photodiodes on the market;
● In complex ambient light conditions, a TOPLED D5140 SFH 2202 wearable will more accurately measure heart rate and blood oxygen saturation (SpO2);
● TOPLED D5140 SFH 2202 provides superior vital signs monitoring for wearable device manufacturers targeting the high end of the market.
Because TOPLED D5140 SFH 2202 is more sensitive to green light wavelengths, the system is able to operate at a lower LED intensity, saving power and helping to extend battery life while maintaining a highly accurate measurement that provides superior heart rate performance. The TOPLED D5140 SFH 2202 comes in a specially designed package with black sidewalls to minimize internal cross-talk, which further reduces optical measurement error and increases the stability of heart rate measurements.
The TOPLED D5140 SFH 2202 is up to 30 times more linear in the infrared spectrum than a standard photodiode thanks to optimisation of the photodiode chip manufacturing process, according to Imis Osram's internal benchmarks. In addition, the experimental data show that the sensitivity of photoplethysmography (PPG) is significantly higher at the wavelength of green light used for heart rate measurement. PPG measures heart rate by tracking the peaks and valleys of light absorption in blood vessels.
By using the highly linear TOPLED D5140 SFH 2202 in PPG systems, wearables manufacturers are able to enable their products to achieve higher SpO2 accuracy when the ambient light is strong or rapidly changing. For example, a typical example would be a user running or cycling through the shadows cast by tall buildings in a built-up urban area.
Florian Lex, ams Product Marketing Manager, said: "In the wearables market, high-end products create greater value for users by providing reliable vital sign measurement capabilities. "By eliminating the high nonlinearity of photodiodes that can interfere with the performance of SpO2 measurement circuits, Imis Osram can help wearables manufacturers differentiate and stay ahead of the curve in the highly competitive lifestyle technology market."
