The 3D format has had something of a renaissance in recent years, but
the technology still has some way to go before the potential of
"real-life" multiperspective 3D can be realized. The Camera Culture
group at the MIT Media Lab is developing a new 3D video projection
system that doesn't require glasses and provides different users
different perspective angles of the same object. The team sees it not as
a final answer, but as a transitional system that sits between current
technologies and true holographic video.
In one form or another, 3D projection systems have
been around almost as long as the cinema itself. The trick has always
been to come up with something practical and economical – preferably
without the glasses, nausea, and headaches. Over the decades, the Bijous
and Odeons of the world have seen two-color systems, polarized light
systems, mechanical shutters and multiple projectors systems come and go
as each fell short of the mark.
The MIT approach was to come up with a glasses-free video projection
system with a wide vision angle, ultra-high resolution, yet is
mechanically simple and doesn't require elaborate installations, as well
as being cheaper than conventional holographic systems of comparable
quality. The idea is that it will act as a short term, intermediate
solution until a more mature technology can be developed, while making
it attractive as a transitional technology for users of more
conventional 2D systems.
The MIT system doesn't
just produce an illusion of parallax – it creates an actual shift in
perspective for multiple viewers looking at the image from different
angles, as if were looking at real objects. In addition, it provides
better resolution and contrast than conventional 2D video.
The heart of the projector is a pair of flat panels of liquid-crystal
modulators that act like tiny liquid-crystal displays (LCD) set between
the backlight source and the lens. The first bank of LCDs produces light
patterns at particular angles. This pattern passes through the second
bank, but only at these angles. These then pass through a series of
lenses that are arranged in the same manner as a Keplerian telescope.
The patterns then pass through a transparent projection screen made up
of lines of vertical lenses, a bit like the striated transparent sheets
found in children’s books and toys that shift between a pair of images.
These resolve the patterns into a 3D image that shifts as one moves from
one of eight points of view to another.
The modulators refresh the image 240 times every second, which is less
than that of modern televisions, but ten times that of standard-speed
film. The system requires a lot of bandwidth to work, but it also opens
the possibility of the system displaying ultra-high resolution video.
Part of the reason for this is that the MIT system uses data compression
algorithms that concentrate on reproducing the edges of the images
rather than the body of objects, because edges change more as an object
moves or turns. The algorithm also produce a brighter image with
stronger contrast by generating something closer to “true black,” which
is not possible for LCDs.
Another way the image is improved is by how the light patterns
interfere with one another. By manipulating this, the system can gain
higher resolutions, though this requires some prodigious real-time
calculations. In addition, the MIT system doesn't simply enlarge the
image, which reduces the field of vision in 3D projections. Instead, the
system spreads out the pixels from one another.
The team sees the technology as having applications in collaborative design and medical imaging as well as in entertainment.
The video below explains the basics of the technology
Source: MIT
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