Re: [xml-dev] Holographic XML

[Norman Gray <norman@astro.gla.ac.uk>]

David, hello.

[drifting off topic, though that was always going to be likely...]

On 2010 Sep 8, at 12:12, David wrote:

> Regardless of what Wikipedia says, I've actually made holograms before.   The old fashioned way with lasers and film.

Me too!  But the new-fangled way, about 25 years ago, calculating the holographic interference pattern, printing it onto paper and thence onto film, and illuminating it with a laser to recover the image.

I had a chat with a colleague about this at lunchtime, during which we both realised that we knew somewhat less about the really detailed mechanics of holography than we had thought.  But you can work quite a lot of it out.

I think you and I might both be right, though.  I've just been looking at the wikipedia page on holography, which mentions [1] different media used for recording the fringe pattern, and in passing mentions 'thick' and 'thin' holograms, with the difference being the diffraction regime in the two cases (Bragg, and Raman-Nath, diffraction).  Thus it appears that the fringe pattern is a 2-d pattern, and that a thin hologram will work, albeit inefficiently, but that for detailed physics reasons the 3-d extent of the hologram itself is important. (I hadn't known that!).

All the best,

Norman


[1] http://en.wikipedia.org/wiki/Holography#Holographic_recording_media

-- 
Norman Gray  :  http://nxg.me.uk
School of Physics and Astronomy, University of Glasgow, UK