They make the movie or television show you're watching look like a 3-D scene that's happening right in front of you. With objects flying off the screen and careening in your direction, and creepy characters reaching out to grab you, wearing 3-D glasses makes you feel like you're a part of the action - not just someone sitting there watching a movie. Considering they have such high entertainment value, you'll be surprised at how amazingly simple 3-D glasses are.
In this article, we'll take a look at the two most popular types of 3D glasses in use today. But first, let's take a look at something called binocular vision.
Binocular Vision
 Photo courtesy Dan Metz View-Master viewer |
To see how much of a difference the binocular vision system makes, have a friend throw you a ball and try to catch it while keeping one eye closed. Also try it in a fairly dark room or at night, where the difference is even more noticeable. It is much harder to catch a ball with only one eye open than with two eyes open. If you want to try a quick test of your binocular vision, visit this Web site.
The binocular vision system relies on the fact that our two eyes are spaced about 2 inches (5 centimeters) apart. Therefore, each eye sees the world from a slightly different perspective, and the binocular vision system in your brain uses the difference to calculate distance. Your brain has the ability to correlate the images it sees in its two eyes even though they are slightly different.
If you've ever used a View-Master or a stereoscopic viewer, you have seen your binocular vision system in action. In a View-Master, each eye is presented with an image. Two cameras photograph the same image from slightly different positions to create these images. Your eyes can correlate these images automatically because each eye sees only one of the images.
 Photo courtesy Dan Metz When you use a View-Master viewer, it's easy to see how your binocular vision system works. |
3D Viewing
In a movie theater, the reason why you wear 3D glasses is to feed different images into your eyes just like a View-Master does. The screen actually displays two images, and the glasses cause one of the images to enter one eye and the other to enter the other eye. There are two common systems for doing this:
Red/Green or Red/Blue 3D Glasses
Although the red/green or
red/blue system is now mainly
used for television 3-D effects,
and was used in many older 3-D
movies. In this system, two
images are displayed on the
screen, one in red and the other
in blue (or green). The filters
on the glasses allow only one
image to enter each eye, and
your brain does the rest. You
cannot really have a color movie
when you are using color to
provide the separation, so the
image quality is not nearly as
good as with the polarized
system.
 The red and blue lenses filter the two projected images allowing only one image to enter each eye. |
Polarization
At Disney World, Universal
Studios and other 3D venues, the
preferred method uses polarized
lenses because they allow color
viewing. Two synchronized
projectors project two
respective views onto the
screen, each with a different
polarization. The glasses allow
only one of the images into each
eye because they contain lenses
with different polarization.
 The polarized glasses allow only one of the images into each eye because each lens has a different polarization. |
There are some more complicated systems as well, but because they are expensive they are not as widely used. For example, in one system, a TV screen displays the two images alternating one right after the other. Special LCD glasses block the view of one eye and then the other in rapid succession. This system allows color viewing on a normal TV, but requires you to buy special equipment.
