Researchers described a novel
tabletop display system that allows multiple viewers to simultaneously view a
hologram showing a full 3D image as they walk around the tabletop, giving
complete 360-degree access. To be commercially feasible in a range of
applications -- from medicine to gaming to media -- the hologram challenge is
daunting. It involves scaling an electronic device to a size small enough to
fit on a table top, while making it robust enough to render immense amounts of
data needed to create a full-surround 3D viewing experience from every angle --
without the need for special glasses or other viewing aids. In the past,
researchers interested in holographic display systems proposed or focused on
methods for overcoming limitations in the combined spatial resolution and speed
of commercially available, spatial light modulators. Representative techniques
included space-division multiplexing (SDM), time-division multiplexing (TDM)
and combination of those two techniques. Researchers from the 5G Giga
Communication Research Laboratory, Electronics and Telecommunications Research
Institute, South Korea took a different approach. They devised and added a
novel viewing window design.
To implement such a viewing
window design, close attention had to be paid to the optical image system. With
a tabletop display, a viewing window can be created by using a magnified
virtual hologram, but the plane of the image is tilted with respect to the
rotational axis and is projected using with two parabolic mirrors. "But
because the parabolic mirrors do not have an optically-flat surface, visual
distortion can result. We needed to solve the visual distortion by designing an
aspheric lens. As a result, multiple viewers are able to observe 3.2-inch size
holograms from any position around the table without visual distortion. Building
on these advances, the team hopes to implement a key design feature of
strategically sizing the viewing window so it is closely related to the
effective pixel size of the rotating image of the virtual hologram. Watching
through this window, observers' eyes are positioned to accept the holographic
image light field because the system tilts the virtual hologram plane relative
to the rotational axis. To enhance the viewing experience the team hopes to
design a system in which observers can see 3.2-inch holographic 3D images
floating on the surface of the parabolic mirror system at a rate of 20 frames
per second. Test results of the system using a 3D model and computer-generated
holograms were promising.
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