From: DecadentLinuxUserNumeroUno@decadentlinuxuser.org   
      
   On Sun, 14 Jan 2018 22:08:32 -0500, gfretwell@aol.com wrote:   
      
   >45 years ago I was in a bar in Chicago and they had a laser deal that   
   >plotted the 2 channels of the sound system as a Lissajous pattern on   
   >the back wall.   
   >I tried to make one using an old Neon laser and mirrors on speaker   
   >drivers about 40 years ago. It was almost working when the free used   
   >laser I had crapped out. Now that laser diodes cost less than a stick   
   >of gum I wanted to try again. What is the best way to steer the laser?   
   >Piezo crystal or some kind of mirror solution   
      
     My first laser disc player was an industrial unit that came out of a   
   "Dragon's Lair" upright video arcade game.   
      
    Inside of that was a HeNe laser tube on a mini light bench.  It went   
   through two mirrors before hitting the splitter/read head.  Both were   
   able to have their angle altered by the hardware  They were 45 degree   
   mirrors on a pivot in the center and had a magnet and a coil behind   
   them.  Electrical stimuluse in the coil moved the mirror.   
      
     I got a new, $2200 Pioneer LD player that year, so the old one   
   became a playtoy for me.   
      
     So, I piped a sine wave into one and music into the other and made   
   music patterns on the ceiling.  It was not able to snap the trace back   
   like an oscope does, but it did make great signatures on the   
   wallboard.   
      
     So anyway, a few years back I bought two more players on ebay, and   
   they were only $30 each.  I no longer have my LDs or the players.   
      
     But my point is you can likely find one of the old industrial   
   players and get the light table out of it.  It already points up at   
   the ceiling.   
      
     OR  you need a mirror (two) with a pivot right behind the reflection   
   surface.  Then a coil centered right over that pivot, and a magnet for   
   the coil to electro-motivate against. It has to be light in weight to   
   be responsive.   
      
     There are likely some pretty cheap didode laser light manipulators   
   out there already.  I mean damn cheap.  Most take music as a stimulus,   
   but I am sure single tone pure waveforms pumped into it would work   
   too.   
      
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