> I also found a website with software for computing interference
> patterns. They claim that if you take something like a 600 DPI laser
> printer and print the pattern onto a transparency, you can shine a laser
> pointer through it and get a very fuzzy, very grainy hologram.

Oooh that sounds interesting, might have to give that a go. I got one of 
those cheap $20 green laser pointers, if you focus it it's enough to 
light a match or melt your name into anything plastic :-)

> CD? Perhaps not; CDs don't use visible light, they use infra-red, so the
> dot pitch might not be small enough.

Well if a 600dpi print just about works, then by my rough estimations a 
CD should be about 20000 dpi. Maybe not perfect, but it works.

> A DVD, on the other hand, uses a
> red laser, so it certainly ought to be able to do a red-light hologram
> without difficulty. (Provided you can convince the drive to put the dots
> where you want them!)

You can't without modifying the drive. IIRC they had to bypass pretty 
much the whole signal path and just drive the laser directly (well not 
quite, but you get the idea).

> When I was at university, we were told that several companies had 3D TV
> technology that was "nearly ready for market". That was ten years ago.
> (I suppose they were probably talking about the laughably primitive
> lenticular lens technology that you occasionally see in shops and stuff.)

10 years ago the company I used to work for was already selling a laptop 
and mobile phone with a parallax barrier 3D screen (that could be 
switched between 2D and 3D mode). That technology has developed into the 
dispay in the Nintendo 3DS and LG Optimus 3D today. That type of 3D is 
fine for single-user applications (because no glasses are needed), but 
for multi-viewer it obviously doesn't work.

Post a reply to this message