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