Lindy,

On Fri, 1 Jul 2005 15:50:45 +0200, Lindy Mayfield wrote:

> Ever sort of moved it around fast on a wall and get cool designs?  I had the idea that one could do 
something like that and maybe create designs, text, pictures.  But the mechanical part of having something 
move that fast and in all directions seems to me to be the difficult part.

There used to be a show at the London Planetarium (and no doubt others) called "Laserium", which was music 
accompanying images on the dome drawn by laser - it was pretty impressive for the time (mid 80's I think).  
Their interpretation of War of the Worlds was amazing - I had never realised how intricate a drawing you can 
do like that.

> Maybe moving a mirror instead of the laser would be better, but again how to move it like that confuses me. 

Yup, that's what you do!  I saw this demonstrated many years ago (when lasers were "a solution looking for a 
problem") and some students had made a rudimentary oscilloscope using little mirrors mounted on piezo-electric 
"stalks" which bent in response to applied electricity, deflecting the mirror and the beam aimed at it.  
Having two (close together) at 90 degrees gave x-y scanning.  They didn't bother to turn the beam on and off, 
so there was always a retrace line when using it in ordinary 'scope time/amplitude mode, but mostly they used 
x-y mode and demonstrated lissajous figures, so problem.

Cheers,


Howard Winter
St.Albans, England


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