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: I built one too!
by Neolander on Tue 10th Jul 2012 10:42 UTC in reply to "I built one too!"
Neolander
Member since:
2010-03-08

I once worked in an acoustics lab where people detected tapping and dragging motion using a flat surface (regular table) with a few cheap piezo microphones stuck on it and a computer program.

It's crazy that modern touchscreens use something as complicated, unreliable and expensive as capacitive sensing, when so many simpler approaches exist...

Edited 2012-07-10 10:53 UTC

Reply Parent Score: 2

RE[2]: I built one too!
by Laurence on Tue 10th Jul 2012 13:42 in reply to "RE: I built one too!"
Laurence Member since:
2007-03-26

I'm not convinced that a microphoned approach would be any more reliable than capacitive sensing. In fact I'd wager it would be far less reliable as it would be subject to outside interference. It's one thing having such a technique work in lab conditions, but when you're at a noisy train station and the phone is in your pocket or trying to detect multi-touch gestures under such environments. Certainly in the for former scenario, you could run the risk of triggering all sorts of false positives. Sure, with enough code you could account for most scenarios, but then you'd create something more complex then detecting the variable voltage change from a persons fingers.

Reply Parent Score: 2

RE[3]: I built one too!
by Alfman on Tue 10th Jul 2012 14:26 in reply to "RE[2]: I built one too!"
Alfman Member since:
2011-01-28

Just to entertain the idea and play devil's advocate here:

If the system relies on the speed of sound reaching sensors, I suspect that's usually fairly constant in most environments. I'd expect the air density to be consistent across the surface, windspeeds of 15+ MPH (sorry, Km/H) would be unusual and that's still only about 1% error against the speed of sound.

Tuning the sensors to a specific frequency should be trivial, and one could even implement frequency hopping and/or multi-spectral tones which are unlikely to be duplicated in any natural environment.

Whether it is superior or not to capacitive touchscreens somewhat misses the point that it may be "good enough" and far more affordable. It could work on natural surfaces too, like walls and floors.


Edit:
Thinking about it further, it should be possible to compensate for the wind-speed issues as well by pairing up the microphones with speakers and detecting the sound waves from the other microphones. This could additionally help automatic calibration and maybe even adhoc placement of the microphones on arbitrary surfaces without any frame at all.

With an appropriate sensor array, I think an acoustic system might be made to work in 3 dimensions. Capacitive sensors can't really do that.

Edited 2012-07-10 14:38 UTC

Reply Parent Score: 3

RE[3]: I built one too!
by Neolander on Tue 10th Jul 2012 15:07 in reply to "RE[2]: I built one too!"
Neolander Member since:
2010-03-08

I'm not convinced that a microphoned approach would be any more reliable than capacitive sensing. In fact I'd wager it would be far less reliable as it would be subject to outside interference. It's one thing having such a technique work in lab conditions, but when you're at a noisy train station and the phone is in your pocket or trying to detect multi-touch gestures under such environments. Certainly in the for former scenario, you could run the risk of triggering all sorts of false positives. Sure, with enough code you could account for most scenarios, but then you'd create something more complex then detecting the variable voltage change from a persons fingers.

Outside noise is not necessarily that much of an issue. If you stick the piezos inside of the device's casing, they will be far, far more sensitive to finger tapping and friction on the device's casing than to outside noise, since there's a lot of acoustic reflection going on at the air-casing interface. That, and acoustic power decreases as the square of the distance that is travelled from the source. To see how big the difference is, just gently tap the surface of a microphone when recording sound : you should get a peak that is far more intense than anything you were recording, even for a very gentle tap.

Pockets are indeed an issue, but on this front microphones are just as bad as capacitive touchscreens, which will also run amok if you forget to turn off your phone before putting it in your pocket. One specific pitfall of acoustic sensing is friction on the back or the sides of the device during device use though. Accounting for these could indeed require complex noise cancellation systems.

Edited 2012-07-10 15:09 UTC

Reply Parent Score: 1

RE[2]: I built one too!
by Alfman on Tue 10th Jul 2012 14:11 in reply to "RE: I built one too!"
Alfman Member since:
2011-01-28

Is this how some of the marker whiteboards work?

It's a standard whiteboard, nothing electronic in it, used with special markers and a detector on the side. It records everything written on the whiteboard to a program.

I've seen this same system hooked up to projection screen and used to interact with a windows desktop.

Reply Parent Score: 2

RE[3]: I built one too!
by Neolander on Tue 10th Jul 2012 15:13 in reply to "RE[2]: I built one too!"
Neolander Member since:
2010-03-08

Is this how some of the marker whiteboards work?

It's a standard whiteboard, nothing electronic in it, used with special markers and a detector on the side. It records everything written on the whiteboard to a program.

I've seen this same system hooked up to projection screen and used to interact with a windows desktop.

There's a simple way to test this hypothesis : tap the whiteboard with your finger. If the surface is soft, you are likely dealing with a resistive touchscreen. If nothing happens, the system likely detects the stylus in particular, which is generally done using Wacom-like inductive sensors. If your finger tap is indeed detected, you may be onto something there...

Reply Parent Score: 1

RE[2]: I built one too!
by phti on Tue 10th Jul 2012 14:25 in reply to "RE: I built one too!"
phti Member since:
2012-06-02

well, that might have worked in a lab, but think about real life: noise interferences and all the problems that a "cheap piezo" would have when exposed to daily heavy usage.
capacitive sensing is not at all unreliable, just take a look at how well it works on an ipad or similar devices. by now it's the best technology we came up with for touch surfaces. too bad it's still expensive and not usable on large surfaces.

Reply Parent Score: 1

RE[3]: I built one too!
by Neolander on Tue 10th Jul 2012 15:32 in reply to "RE[2]: I built one too!"
Neolander Member since:
2010-03-08

I've already discussed the issue of noise in another reply, so I'll just explain what makes capacitive touchscreens so unreliable as compared to all other touchscreen techs : their sensitivity to water. If your screen becomes humid for any reason (rain, sweat, freshly washed hands...), the device will start become unresponsive or register false positives in a matter of minutes. Since when do we build mobile devices that can't stand a few drops of one of the most widespread chemicals of planet Earth ?

And there is a reason why the tech is so expensive and sensitive to external perturbations too : it requires ridiculously complex hardware by its very nature. As if resistive touchscreens and their need for fine-tuned mechanical properties weren't complicated enough, the best which hardware engineers could come up with as a successor was a fine mesh of transparent electrodes stuck in the tiny space between a LCD and a protective plate, following the tiny capacitance difference induced by the presence or absence of a human finger milimeters away while shielding itself from its direct electromagnetic environment somehow ? Honestly, if they just wanted to come up with something bizarre enough that it would create tons of jobs in R&D and stimulate the economy, they could have stated the goal right away...

Edited 2012-07-10 15:35 UTC

Reply Parent Score: 2