2021-07-08 11:59 AM
90% more or less of IR is absorbed per meter, whereas only 29% is absorbed for 500nm (https://www.britannica.com/science/seawater/Acoustic-properties). For underwater automation, it would be useful to have a TOF sensor that works at a different frequency.
2021-07-09 08:22 AM
One reason ST picked 940nm was there was less of it at sea-level. Turns out water-vapor in the upper atmosphere absorbs a lot of 940nm. So you are correct.
But I'm guessing a different laser is out of the question.
ST can sell this sensor inexpensively because the cell-phone industry buys them by the millions and millions. (Over 1.5 billion sold.)
Producing a special purpose part that would only sell in the few-hundreds of thousands would only make economic sense if we could sell it for 10 to 20 times the cost of this sensor. And it would be huge risk.
So, as cool as that sensor would be, I don't think think one could make the economic case for it.
Bummer,