[sdiy] OT: Laser Microphones?

[James Patchell]

I have built a laser based microphone.....

Well, actually it was a motion control system with a laser interferometer 
for the feedback element....

It is amazing how sensitive it is to any sort of vibrations...although, it 
was a pretty noisey microphone (a block of granite is not the best thing to 
use to make a microphone).

Your biggest problem is going to be in how to convert the deflection into a 
signal.  You could use an interferometer, but I suspect your S/N would be 
very poor, not to mention bulky.  I would imagine there are other ways as 
well, but I know very little about optics.


At 01:23 AM 9/1/2003 -0400, Glen wrote:
>Does anyone know of any internet links regarding laser-based microphones,
>other than those designed for surveillance? It just seems to me that
>someone would have tried to make a microphone that used a laser, and use it
>for "normal" high fidelity recording purposes. Unfortunately, all the
>information I can find is related to bouncing a laser off someone's window,
>to listen to conversations on the other side of the window.
>
>Couldn't the beam be bounced off a reflective membrane mounted very close
>to the laser, and then analyze the reflected beam, to record sounds in the
>same room as the laser? I'm wondering what advantages there might be to
>laser pickup of the membrane's vibrations, compared to magnetic (dynamic),
>or electrostatic (condenser) pickup of the membrane's vibrations.
>
>It shouldn't be as prone to pickup of stray magnetic fields as a dynamic
>mic, and therefore should work well around CRT's and other magnetic
>devices. I think it might also offer the potential to have less background
>hiss than a typical condenser, and have a potentially large dynamic range.
>
>Does anyone know of any attempts to create such a microphone?
>
>later,
>Glen

         -Jim
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