Tech Brand Talk

How 3D Active Shutter Glasses Work

by Blogger ‎04-23-2010 03:04 PM - edited ‎09-22-2010 06:43 PM

One of the questions I often get is, "Why are the glasses for 3D TV's different from the ones in the theatre?". The answer really is all about the environment for playback.


First off, you need the glasses to separate the image going into the left and right eyes.  Just like the camera captures one image for each eye (see my previous post), the display system has to deliver one image for each eye.


So here's what happens in a theatre:


The room is completely dark. This is really important as the glasses only need to filter the image directly in front of you. You don't have to worry about windows or ambient light or people searching around for the remote.


3009i519EFA857ED09576You have two projectors delivering those left and right eye images. The images pass through polarizing filters that match up to the left and right eyes of your glasses, giving you a separate movie for each eye. Some digital projector systems can use a single lens and a special polarizer in the projector to achieve the same effect, but the result is the same.


The other important technical element is you are using an ultra-bright bulb to drive the picture. Some of those polarized lenses can cut the brightness of the picture by 40%-60%. You can adjust the brightness of that bulb up to compensate for the polarizing effect.


Making the bulb brighter generates a great deal of heat and the bulbs do not last as long. Because all that equipment is hidden and the extra price of operating it is spread over a large group of people, most of the technical and economic issues are not even evident to the audience.

 

Here's what happens in the home:

 

The TV displays the left and right images sequentially, one after another. The glasses blank the left and right eye in sync with an Infrared Pulse coming from the television. In this way, the polarizing effect does not dim the picture as much as the theatre scenario. We need that brightness to get a great picture in the home environment.

 

Active Shutter.jpgThe problem with alternately blanking the view of your left and right eye is that process can make prolonged viewing uncomfortable. That's why Sony built their glasses to blank only the TV image and not the rest of the light coming into your eye from the room around you.

 

The glasses are also designed to minimize reflection and light coming to your eyes from the sides and behind. We also make sure we use lots of IR emitters to send the signal to the glasses, so the sync remains rock solid. All of these little design elements help create a comfortable 3D viewing experience.

 

There are also plenty of techniques we implement into the television to ensure the comfortable experience. We use the extra frames available to us on a 240Hz system to make sure that we only get the left image to the left eye and the right image to the right eye. This is critical because if you see any image doubling or ghosting, it is the result of seeing part of the image meant for your right eye with your left eye or vice versa. This is commonly called crosstalk. The order we present the frames prevents this effect.

 

We also use LED Boost technology to make the picture brighter when showing a 3D frame, so we can have the same bright colour and excellent contrast you get on your 2D video.

 

It takes a long time to explain in text, so I made a YouTube video that shows the whole process in more detail:

 

http://www.youtube.com/watch?v=LAIiA0jOgTk

 

Next time, we'll look at some of the most common questions people are asking about 3D technology.

 


 

Comments
by Trusted Expert / Community Ambassador on ‎04-25-2010 10:35 PM

Thanks Brent for the insightful article on 3D.

 

In the article you mention that Sony's glasses will only blank the TV image and not the rest of the room.  Can you elaborate on this?  Are you saying that only a portion of the viewing area is actually blanked depending on the size and location of the TV with respect to the viewer?

 

Thanks.

by R_D(anon) on ‎04-27-2010 09:59 AM

Don't forget to add the fact there are many reported cases of individuals having seizures while these 'flickering' glasses.

 

Bad idea.

by R_D(anon) on ‎04-27-2010 10:00 AM

while wearing

 

oops!

by Trusted Expert / Community Ambassador on ‎04-27-2010 11:37 AM

I think the point he is trying to make is that you have less liklihood of seizures or other side effects from Sony products because they are of better quality and are synchronized tighter than competitive products.

by DanDaring(anon) on ‎04-28-2010 10:16 AM

Red lights at an intersection will produce seizures also, the frame rate of 3D tvs works in the same fashion. If you have a pre-existing condition like epilepsy, maybe you should use common sense and avoid a product that flashes multiple images in sequence.

 

People with heart conditions should probably avoid skydiving also...

by Trusted Expert / Community Ambassador on ‎04-28-2010 12:15 PM

There are warning labels for just about everything that has some sort of moving picture - video games, movies, etc.  Bright lights and fast moving picture all has the potential to cause seizures in those that are prone to them.  If you are not prone to seizures (ie. not epileptic), then you will probably have absolutely no issues using these products and will never experience any ill effects.

 

Just like with video games, some people tend to blow the potential dangers out of proportion.  The majority of people will be able to use these without any problems.

 

JB

by Recognized Expert / Community Ambassador on ‎04-28-2010 07:12 PM

I'm excited to this see this technology in the store and how it differs from the Samsung 3D setup. I'm someone who is eagerly awaiting this technology, and hopes it gains mass acceptance.

 

You mention in the video that the shutter glasses will be adjustable. Will they be adjustable enough to accomidate those of us who already wear prescription glasses? The Samsung system is FAR(very far) from being useful for me. My gasses are too wide, and the shutter glasses can't sit comfortably. Will the Sony glasses address this?

by sean09cbr(anon) on ‎05-11-2010 05:52 PM

 

I can only foresee this 3D TV becoming a fad which will fade away... like minidisc.
My gripe with 3D TV is that for it to be EFFECTIVE the picture would have to consume the majority of your line of sight and consume your peripheral visions to trick the brain in to thinking you are there... like the movie theatre does. 
Sitting 10' feet back from a 46-52" televisions hardly achieves the same goal. Not to mention the flicker on the television is much worse than the movie projectors and besides... who really wants to make a habit of wearing glasses and going cross eyed?

I can only foresee this 3D TV becoming a fad which will fade away... like minidisc.
My gripe with 3D TV is that for it to be EFFECTIVE the picture would have to consume the majority of your line of sight and consume your peripheral visions to trick the brain in to thinking you are there... like the movie theatre does. 
Sitting 10' feet back from a 46-52" televisions hardly achieves the same goal. Not to mention the flicker on the television is much worse than the movie projectors and besides... who really wants to make a habit of wearing glasses and going cross eyed?

 

by Exalted Expert / Community Ambassador on ‎01-15-2011 10:33 PM

Here's another option to avoid glasses... http://www.youtube.com/watch?v=Uef17zOCDb8

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