
Hitachi demos 3D real-world object projector - evo_9
http://www.physorg.com/news/2011-10-hitachi-demos-3d-real-world-projector.html
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wxs
I believe the writeup is misrepresenting how this works. It states that the
system projects "on to" the object, however given that their example is an
egg, which has a Lambertian (matte) surface, you would not be able to present
different projections to viewers at different angles.

From the diagram, it looks like they're projecting onto a glass screen in
front of the object, and it appears to be superimposed on the object using the
same approach as the Pepper's ghost box [1].

Of course I may be mistaken. This is just an educated guess.

And regardless, this sounds like a really cool technology.

[1] <http://en.wikipedia.org/wiki/Peppers_ghost>

EDIT: From the Google Translate of the Japanese press-release, this looks
correct, they are using a half-silvered mirror so you can see the egg-through
the mirror and also the projection reflected on the mirror

" Hitachi, respond to these needs, aiming to represent the object close to the
actual images from nature, using a half mirror for combining multiple lenses
and translucent, the image information captured in real-space projection of 24
units has enabled it to be displayed".

~~~
meatsock
<http://en.wikipedia.org/wiki/Pepper%27s_ghost>

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jxcole
This isn't the same as holographic 3D like the article claims. It is true that
it will look different from different angles, but that isn't all that
impressive. You could say that a television is sort of like a painting that
moves. If you were to take a painting and then wrap it into a cylindrical
shape, that wouldn't make it 3D, it would just make it differently shaped.

Likewise, this technology just projects onto on oddly shaped object. It
doesn't magically add any of the depth feeling that you get from, for example,
watching a movie with 3D glasses.

The reason this is so difficult is that when you view a real object, it
reflects light in all directions so that your eyes actually see two different
images when you look at it from two different angles (your two eyes, or any
other arbitrary viewing angle).

Imagine that you were trying to make a projector that no human would be able
to distinguish from a real window. Imagine that you had the requirement that
the user would have to be able to look in different directions out the window
and get different views just like a normal window would. What you would have
to do is create pixels that can project different colors in different
directions and maintain complete control over which color was projected in
each direction. In short, you must create a pixel that will look different
depending on which direction you view it from.

If you think of it this way, you basically would have to control each pixel as
a series of subpixels, each subpixel pointing in a specific direction. To make
it realistic, you would probably need thousands of subpixels for each pixel,
increasing the requirement for number of pixels by thousands of times and
decreasing the required minimum size by thousands of times. Also, you have to
make the subpixels point in only one direction.

And that, my friends, is almost impossible.

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wxs
No no, see my comment. They don't project directly onto the object, and they
use a number of projectors, each of which will correspond to an "angle" that
you see. Sure they might not have enough pixels to mimic exactly what you see
in the real world, but they can probably get decently close.

Also, with regard to your comment about making pixels look different depending
on the angle, there's an alternate approach to this using stacked LCDs that's
getting interesting results.

<http://web.media.mit.edu/~mhirsch/hr3d/>

