[mythtv-users] OT: 3D TV

Daniel Kristjansson danielk at cuymedia.net
Mon Jan 11 19:22:21 UTC 2010


On Mon, 2010-01-11 at 16:41 +0000, Vitani wrote:
> 2010/1/11 Justin Johnson <justin.johnson3 at gmail.com>
>         the TV has some device that communicates with the glasses to
>         allow different frames to be shown to different eyes.
> 
> Seriously? The TV sends a signal to the glasses? Meaning the glasses
> need batteries? Really? That's baaaad.
> 
> Why can't they do it the same as 3D in cinemas with polarised(?)
> lenses?

Some do, but it is more expensive to implement. LCD screens are
inherently polarized. So you need to either apply a large film
precision aligned to alternate rows to the LCD (expensive), or
change the tech to alternate polarization on the row level
(expensive), or use a technology like DLP projection.

LCD's work by blocking light using polarization. Normally
you have one large plane of a single polarization, and then
you twist each active element (pixel) up to 90 degrees, to
block out light. There is a wikipedia article that covers
the details of the different technologies, but you can probably
guess why this means shutter glasses can be implemented at
practically no additional cost while "doing it right" brings
the cost of the display into the $10k range.

DLP's just use mirrors and a color wheel, there is no inherent
polarization. So doing circularly polarized stereo projection
in a theatre just means you need a DLP capable of running color
at 48 Hz and new color wheel with twice as many filters. In a
big system like that you can also use multiple LCD's, but they
of course need to be precision aligned when the projector is
installed in the theater.

PS You want circular polarization as opposed to linear so that
tilting your head slightly doesn't dim the image.

-- Daniel



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