On 23/12/2013 01:58 PM, scott wrote:
>> [No, I do not mean volumetric displays. I mean a display where you
>> compute the interference patterns of an optical wavefront, then use some
>> kind of display device to produce that pattern.]
>
> A friend from university did this:
>
> http://lightblueoptics.com/videos/holographic-laser-projection-technology/
>
> Judging by the (lack of) recent updates it didn't really take off.

Indeed.

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. (Assuming 
your printer doesn't try to interpolate or otherwise alter the precisely 
computed pixel patterns!)

> FWIW before this, his research project at university was to modify a CD
> burner to burn holograms onto a CD. I guess the "pixel pitch" on a CD is
> enough for it.

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

>> I did see a demo of a commercial offering which is supposed to be coming
>> to market soon - but it uses eye-tracking to slash the amount of
>> processing power required. (I.e., it won't actually work in the real
>> world and so will never be commercially viable.)
>
> Yes, eye tracking always introduces further issues. One demo I saw,
> which I'm surprised hasn't taken off, is to use the video feed from a
> camera as an environment map texture. This demo was running on a laptop
> using the inbuilt webcam and the way shiny surfaces reflected your face
> and what was behind you in the room was very believable.

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.)

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