On 28 Sep 2005 at 22:17, Damon Hamm wrote:
>  Reflecting
> the beams back from a mirror seams too hard to calibrate, but I'm open
> to ideas.

Retroreflective sheeting works well. You can get high quality stuff 
with sticky backing in red/white stripes meant for truck trailers.

You will need to modulate your beam so you can have something to 
distinguish it from ambient light and reflections.

Cheers,

Bob

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