Apple was in a patent dispute over this feature with Massimo. Their workaround is to calculate blood oxygen on the iPhone, using the sensors from Apple Watch.
The Apple Watch hardware is otherwise the same. The back of the watch shines light of a specific wavelength into your skin and measures the reflected light. Heart rate sensing uses green (525 nm) and infrared (850–940 nm) light; blood oxygen sensing added a red light at 660 nm in 2020.
The iPhone will now calculate the ratio of absorbed red to infrared light, then apply calibration constants from experimental data to estimate blood oxygen saturation.
Interesting that a small change like that is enough to not make it infringe the patent anymore. I guess you have to be really careful when writing patents to cover as much implementation variations as possible.
mikestew•1h ago
Sounds like my wife’s AW6, which used to have this feature but doesn’t after sending it in for battery replacement (Apple replaces the Watch with a refurb), will continue to not have this feature anymore. IOW, watch that had this feature, doesn’t after battery replacement.
I’m curious why this isn’t settled. Apple has surely floated an offer, and it would appear that Apple isn’t going to budge on this. Were I in charge at Massimo, I’d think some money is better than no money.
brandonb•2h ago
The Apple Watch hardware is otherwise the same. The back of the watch shines light of a specific wavelength into your skin and measures the reflected light. Heart rate sensing uses green (525 nm) and infrared (850–940 nm) light; blood oxygen sensing added a red light at 660 nm in 2020.
The iPhone will now calculate the ratio of absorbed red to infrared light, then apply calibration constants from experimental data to estimate blood oxygen saturation.
More detailed writeup on how the technology works is here: https://www.empirical.health/metrics/oxygen/
echoangle•1h ago