MOTM

http://www.youtube.com/watch?v=3DFmXvFbWuc

Note that when Terry mentions "..the E350 is the filter..." this is 
referring to what is used to drive the galvos (the E350 is a VCO in 
reality). Normally, envelope-detected audio is used as the "filter" and the 
galvos are swept by quadrature triangles (like a CRT raster sweep).

For those interested in replicating this setup: I will ask what galvos he is 
using and what they cost/where to buy. Note several important things:

a) in the US, this sort of laser projector CANNOT be used in public unless 
under very STRICT requirements.
b) professional "off the shelf" XY galvo pairs w/drive electronics and power 
supply can run $1500. The galvos can require 3A peak each, and the moving 
mass/inertia is large. The galvos are usually mounted on 1/4 in steel plates 
(called optical plates) and then inside a matte black steel box weighing 
10kg/25lbs to keep vibration 'errors' to a minimum. The box keeps spurious 
laser deflections from "flying around the room" . These galvos are also very 
fast and very accurate: they can move to 30,000 individual positions per 
second (the mirrors usually have 45-55 degrees total travel) at 0.05 degree 
accuracy.

Thanks again to Terry Ahrens for setting this up and making the videos.

Paul S.