Linked by Thom Holwerda on Tue 10th Jul 2012 01:24 UTC
Microsoft "Microsoft and Perceptive Pixel Inc. (PPI) today announced that they have entered into a definitive agreement under which Microsoft will acquire PPI, a recognized leader in research, development and production of large-scale, multi-touch display solutions." Yes, Jeff Han is now a Microsoft employee. This demo still amazes me - from 2006. Before the iPhone. Before Android. Before the iPad. Remember that the next time you wind up in a discussion about who supposedly invented what.
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RE[5]: I built one too!
by Neolander on Wed 11th Jul 2012 20:27 UTC in reply to "RE[4]: I built one too!"
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Regarding night clubs, I don't know if that would be enough to perturbate an acoustic touchscreen, but I agree that doing the experiment with a prototype would be a good idea...

I think that tap amplitude and tune are not very important for this design, however, as long as the following conditions can be met :
1/It can be assumed that the acoustic properties of the screen are uniform and there are some absorbers on the sides to address the problem of reflections
2/It is still possible for the mics to detect a reproducible signal that is reasonably far above the noise level

That is because, for the design which I have seen at least, finger position tracking is based on sound propagation delays, not attenuation or wave shape. If we detect a pulse on mic 1 at a time t1, on mic 2 at time t2, and on mic 3 at time t3, we can measure t2-t1 and t3-t1, then deduce spatial positioning information using such calbration data as the speed of sound inside of the screen material and the well-known mic network geometry.

I would gladly draw you a sketch that explains this in more details, but my main computer is currently undergoing repairs and cellphones are not very good for that kind of things.

Since we are only interested in the direct signal flowing from the impact region to the mics without undergoing reflections, rubber casing should not be a problem. In fact, they could even help addressing the problem of reflections and the one of friction on the back and the sides of devices that I mentioned above.

To conclude, I am not sure that acoustic touchscreens could play the same role as capacitive touchscreens either. The guys who worked on them at that lab preferred to market them as a path towards cheap large touchscreens (such as touch-sensitive shopwindows). I was just playing with the idea in thoughts experiments to see what would be the advantages and drawbacks, and found that it might work surprisingly well in that scenario, with much simpler hardware than the capacitive electrode mesh insanity. But I'd probably need to build a prototype (which is way beyond my knowledge of embedded electronics) in order to test some of the potential issues that have been raised here.

Edited 2012-07-11 20:43 UTC

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