Re Virtual Objects have depth ?

[P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>]

Peter Abrahams post interested me as he seems to have similar ideas to some
of my own and has got further in trying them out although it seems with
negative results which seem to cofirm my doubts about the method. Some time
ago I saw a demonstration on TV where the real image from a hologram was
allowed to fall onto a rear projection type of material. Only a 2D slice of
the hologram was formed but as this was moved back and forth different
slices were obtained . It seemed to me that if this was done rapidly enough
the complete image would be obtained by persistence of vision and would
allow a projected enlarged image of a hologram to be produced which canot
otherwise be done . I then thought about the use of a 3D screen of smoke or
suspended particles in liquid . The problem is the image would be scattered
and degraded on the way through and if a lens was involved each plane as
well as a sharp image of part of the object would contain an unsharp image
of the rest.
  Projection of an actual object as opposed to a hologram this way may be
very old as the early magic lanternists projected images onto smoke screens
in the late 1700,s early 1800,s and one in particular Etiene Gaspard
Robertson from Belgium also projected puppets etc with an early episcope
type device although I am not shure if he combined the two together as he
also projected painted slides.
 As to using fluorescent material Leny Liptons book Foundation of the
Stereoscopic Cinema and another persons book The 3D Oscilloscope show
patent drawings for TV systems where two electron or UV light beams
scanning provide enough energy to excite the redsidual gas (mercury vapour
in the case of UV) just where the two intersect in a cathode ray tube
without the normal flat flourescent screen on the front. I dont know if
they got any further than patent drawings, devices like this are I believe
called Volumatic displays and have the disadvantage of producing
transparent images which reduces their realism.

                                                          P.J.Homer



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