Sergey Dryga wrote:

> Randy Boulter <wrb <at> isp.com> writes:
>>
>>I have been tasked with doing a conceptual design for a device that tracks 
> 
> finger movement using a sensor
> 
>>device mounted to the finger.  Does anyone have experience with this or 
> 
> something similar?  Or thoughts or
> 
>>ideas? 
> 
> 
> How about using a (ultra)-sound source at the finger and 3 microphones to 
> triangulate the position.  Something like this was used for DNA sequence 
> readout from autoradiographs using a pen as pointing device. The resolution was 
> in sub-mm range (IIRC).
> 
> Another option is to use 3 sound transducers and microphone on the finger to 
> find position, similar to GPS, only with ultrasound.

This method works quite well. We had an old 3-d digitizer that used
a pen that snapped (electric arc) and 3 mics with about a 0.5 meter
spacing, and it covered the 1/2 meter cube quite well.

With 4 external sources, (to get better closure on the RMS position
error), and phase measurements, one could get very good accuracy,
if a continuos high sample rate was required.

Sounds to me like you're looking to do performance art, so there is
no budget available to use the optimal technology.

Robert
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