Holographyforum.org / holowiki.org

Here's something to get your goat over the weekend:

http://hackaday.com/2009/08/06/tangible-holograms/

Great technology. Of course what spoils it is the idiots calling it holography. So they can't be as clever as they seem.

In ISDH, the chairman, Frank Fan, the co-chair of the conference, showed a large live video lenticular system. His talk on it is recorded here:

http://river-valley.tv/4d-fourier-trans ... olography/

(For some reason it is all theory, seemingly unrelated to this lenticular system. I guess it sounds more macho that way!) At the end you might hear me saying it is very interesting technology, but what is it doing in a holography conference? He insisted it was holography, and got Stanislovas from Geola to come on stage and support him. I feel holography should involve interference and diffraction of light at some stage.

Here's another example to consider: The use of a holographic directionally diffusion screen with at least two projectors to provide a three dimensional image. This was patented in the late '80s by Craig Newswanger, and developed since then by POC and Intrepid World Communications. The light that goes into the viewer's eyes is a holographic reconstruction in the classical sense, it's just that the holographic image reconstructed is a diffuser. The information that makes it interesting to look at is projected onto the hologram and focused onto the retinas with the diffuser function it gets as it diffracts through the hologram.

Is that holography? Cetrainly is wavefront reconstruction. It's a 3-D image.

Oh, I forgot. You are right in that there was a holographic diffusor in the system. But I think it is still stretching the definition of holography...

Kaveh ... about that presentation, I don't understand what the 4D fourier transform of the title has got to do with anything. Using HOEs to display integral images is all well and good, but you don't need a fourier transform to compute an integral image. Is there any more meat to it in the actual paper?

MfA - wonder if it has to do with the recent bout of graphics-meets-optics papers regarding light field rendering, such as acquiring a light field using a fly's-eye lens array and then refocusing. Like Ng's "Fourier Slice Photography."

g

That's pretty cute (but I have my doubts whether it is complete correct in the presence of occlusions). I still don't really see the need for it in the integral imaging display from the presentation though.

BTW, holograms can do the same thing with much less data (in the computer anyway, the resolution we need for holograms in real life is more a factor of the wavelength of light we get to play with than anything else).

Kaveh -

I watched some of his online presentation but found myself skipping around it. In your question you implied that you had seen it in person. What was it?

Gregg

Well, Greg, the presentation was high level theoretical stuff, so put me to sleep pretty quick, but he was showing a system of several dozen ccd cameras on a log rail (estimate 3m), each projecting real time to the back of a lenticular system with holographic diffusor. So you saw real time 3D. But too many distortions, and not really effective in this incarnation.

Thanks, Kaveh. So I suppose it is similar to the MERL system: http://www.merl.com/publications/TR2004-067/. Perhaps the theory-stuff led to a smart organization of the reconstructing rays, but that's another topic.

g