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The
Mark-I Holographic Video Display is capable of rendering full-color
25x25x25mm images with a 15° view-zone at rates over 20
frames per
second. The holographic image is generated using a three-channel
tellurium-dioxide Acousto-Optic Modulator (AOM). A holographic
fringe
pattern is sent through each channel of the AOM to modulate
red (HeNe),
green (double-YAG) and blue (HeCd) light. The three resulting
wavefronts
are combined using a Holographic Optical Element (HOE), to
produce one
horizontal line of the horizontal-parallax-only image. To
provide sufficient
resolution for the holographic diffraction pattern, each horizontal
line is 32K
samples per color. Since the holographic fringe pattern in
the AOM is
moving, a horizontal scanning mirror (18-sided spinning polygon)
is used
to scan out the horizontal line and make the image appear
stationary. A
vertical scanning mirror is used to produce 64 lines (at video
resolution)
in a raster scan fashion.
Each frame of the holographic image is 6-MBytes and needs
to provided
by a frame buffer as a 32K-sample horizontal by 64-line vertical
signal
simultaneously for red, green and blue. We are currently using
a Silicon
Graphics Onyx with an RE2 to be able to produce these patterns
in this
format at near video rates. The display can be run in two
modes, either
displaying pre-computed images at over 20 frames per second,
or in
interactive mode updating the image at over 2 frames per second.
In
interactive mode, a user can manipulate the image using several
dials,
and each new 6-MByte fringe pattern is computed on the fly.
User
operations include choosing new 3D objects, scaling and rotating
those
objects, and changing the lighting direction.
SELECTED REFERENCES:
The design of the Mark-I monochromatic and full color display
is detailed in the following papers:
P. St.-Hilaire, S.A. Benton, M. Lucente, and P.M. Hubel,
"Color images with the MIT holographic video display,"
in: S.A. Benton, ed., SPIE Vol. 1667, Practical Holography
VI (Feb., 1992), paper 1667-73, pp. 73-84.
Mary Lou Jepsen, "Holographic video: design and implementation
of a display system", S.M. Thesis, Department of Architecture,
Massachusetts Institute of Technology, 1989.
Joel S. Kollin, "Design and information considerations
for holographic television", S.M. Thesis, Department
of Architecture, Massachusetts Institute of Technology, 1988.
For information on computation and rendering of images on
the Mark-I display, see:
John
Underkoffler, "Towards Accurate Computation of Optically
Reconstructed Holograms", S.M. Thesis, Program in Media
Arts and Sciences, Massachusetts Institute of Technology, June
1991.
Mark Lucente and Tinsley Galyean, "Rendering
Interactive Holographic Images" Proceedings of SIGGRAPH
'95 (Los Angeles, CA, Aug. 6-11, 1995), pp. 387-394.
For
additional references, see our publications
page.
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