If I bounce the beam from a laser pointer off something that's moving, say, a window pane in a room with an ongoing conversation, the return beam will be frequency modulated. Any good ideas about how to recover this signal? This topic will get stranger.........
If I bounce the beam from a laser pointer off something that's moving, say, a window pane in a room with an ongoing conversation, the return beam will be frequency modulated. Any good ideas about how to recover this signal? This topic will get stranger.........
Visible is cheaper. Since I'm not spying on anyone, cheaper comes first.
However, it gets worse. I need to get the sounds from inside a strip of steel, which has an uneven surface and is going by at better than 50m/s.
The roar of the surface will swamp the signal in one beam, maybe if I use 3 or 4 and some sort of correlation technique? I think the DSP boys will be needed for this one.
Try looking up a michelson inferometer on Google. I think this is the sort of system that the laser microphones use. Rather than measuring the doppler shift they measure the interfearance between a reflected beam and a non-reflected beam. The sensor is a simple photodiode.
measuring something with a laser that is going 50m/s is going to be tough. Can you mount a sensor to the metal itself?