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From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.graphics
Subject: Re: 3d Computer Generated Holography
Message-ID: <46900038@uxe.cso.uiuc.edu>
Date: 31 Aug 89 19:24:00 GMT
References: <441@ctycal.UUCP>
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Nf-ID: #R:ctycal.UUCP:441:uxe.cso.uiuc.edu:46900038:000:1736
Nf-From: uxe.cso.uiuc.edu!mcdonald    Aug 31 14:24:00 1989



>If the holograms in your museum are white-light viewable transmission
>holograms, they almost definitely have no vertical parallax.  That's

There seem to be two different kinds in the display:

Single color (nominally) reflection with white light shining on them.
There are deep red ones and light green ones. These are full three
dimensional images of small objects, plus one which is not a hologram at all
but rather two different holographic mirrors, one on top of another,
one of them flat and one curved, so the viewer sees two reflections
of himself. The green one show color fringes rather badly, but all
are very nicely full 3D.

The transmission ones appear not to be holograms at all, in the usual sense.
They are holographic images of two different images of the same (large)
subject, made with an ordinary camera, and put onto the holographic
film so that if you stand in the right place the 1st order diffraction
images of one picture reaches your right eye, the 1st order of the 
other reaching your left eye. You move your head right or left and 
see the spectrum of the light source. Put your head in the wrong spot and you 
can get different orders into each eye. These are NOT a success.

It would seem wrong to call something "a hologram of such and such an
object" if the viewer cannot refocus his eye on different distances
in that object , and cannot look at different views: above, below,
left, right. By this criterion, the second of the above are not
holograms of the original subjects - they are holograms
of flat photographics prints (or transparencies).

I have never seen holograms illuminated by white light that looked
remotely as good as ones illuminated by a HeNe or Ar or Kr laser.

Doug McDonald