Re: [xml-dev] Holographic XML

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

Greetings.

[physics niggling]

On 2010 Sep 7, at 17:12, David wrote:

> First off, physical holography (on film() requires 3D not 2D film.   The holographic pattern is encoded in a "thickness" of film" and cant be done like normal photography on purely 2D film.

I don't think that's the case.  A hologram is stored on 2-d film.  Perhaps you're conflating this with holographic storage?  The wikipedia article on that[1] is a bit garbled, but points to [2], which makes it clearer that '3-d' holographic storage is effectively a lot of 2-d stores stacked on top of each other, only one of which is read at a time.

[[ In case anyone's interested: the way that photographs work is that they store the intensity of the light at each point in the plane of the film or sensor.  But that's not all the information that's in the light field at that point -- phase information is missing.  What a hologram does is to store the intensity _and_ phase information present in the field, in a particular plane (ie, 2-d structure) intersecting the field, in such a way that both can be resurrected at a later stage.  The fact that you now have the complete reconstructed field to play with is what allows you to focus at different points in the image, or look at it from different angles. ]]

Best wishes,

Norman


[1] http://en.wikipedia.org/wiki/Holographic_storage
[2] http://en.wikipedia.org/wiki/3D_optical_data_storage

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