[mythtv-users] OT: 3D TV

Nicolas Will nico at youplala.net
Mon Jan 11 19:14:04 UTC 2010

On Mon, 2010-01-11 at 17:02 +0000, xavier hervy wrote:
> Vitani wrote:
> > 2010/1/11 Justin Johnson <justin.johnson3 at gmail.com 
> > <mailto: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?
> >   
> Because a TV can not send polarised images 

Well, there are 2 technologies for stereo viewing (so called 3D), and
both end up doing the same thing, sending different pictures with a
slightly different point of view to each eye.

Active stereo requires only one image production system. It
alternatively displays images for the right and left eye. Active glasses
are needed. Those glasses are in fact LCD shutter, blocking the view of
one eye when the displayed image is for the other eye. The glasses need
batteries for the LCD part. The TV needs to send a signal to the glasses
for proper synchronization. In order to "view" a perceived 24 fps, the
TV needs to have twice the frame rate, 48 fps, 24 for each eye.

Passive stereo works by using 2 image production systems, normally
projectors, with images superposed on top of each other. Each source has
its images going through circular polarizing glass, each image in one
direction, a source for each eye. The viewer wears glasses fitted with
circular polarizing glasses, filtering each source for each eye. The
glasses require no battery or any kind of synchronization.

Both methods achieve the same result successfully, without any viewing
angle problem. People tend to react differently, though. Some have
headache within various time frames with each methods. Personally I can
last for hours on a passive system when I can have a headache with 15 mn
on the active stuff. I'm working in an Oil and Gas Service company and
we have used both systems for years within large visualization room
showing geophysics and geology at very high resolutions (blended sets of
projectors). It's funny to see all that invade cinemas and now our
living rooms. NVIDIA used to propose home systems around the GeForce 3
generation, active, using CRTs. The 60Hz LCD panels killed it, but now
NVIDIA is relaunching something as 120 Hz panels/monitors are rolling
out (Samsung started it, I've played with a few, it's fun).


Obviously a simple TV will never be able to do passive, so active is the
way to go.

We better get used to the glasses, they will not go away. Systems
without glasses can be seen here and there, but the system that
separates the images for the left and right eyes is very imperfect and
is very limited in the angle of vision before it gets ugly and you get
sick. Optics and physics are so that not much can be expected there;
stereo requires a clean separation of both images.


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