On Wed, 28 Sep 2005 19:30:38 -0700, Bob Blick wrote:

> 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.

Or the circular plastic "reflectors" mounted on the rear and sides of vehicles, and on roadside posts.  Your 
local car accessory shop may have them (in the UK "Halfords" certainly would, perhaps in the bicycle section).  
They are a field of rectangular reflectors, which send the return beam back at the same angle it arrived, 
displaced a few mm.

Cheers,


Howard Winter
St.Albans, England


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