Welcome to the STEREO Learning Center

How does 3d work?

Most human beings use what is known as binocular vision to perceive depth and see the world in 3D. The binocular vision system relies on the fact that we have two eyes, which are approximately 3 in apart. This separation causes each eye to see the world from a slightly different perspective. The brain fuses these two views together. It understands the differences and uses them to calculate distance creating our sense of depth and ability to gauge distance.

A simple way to understand this principle is to hold your thumb up at arms length and close one eye. Then try closing the other eye. As you switch between open eyes you should see your thumb "jumping" back and forth against the background. 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.

3D Viewing

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 then correlate these images automatically because each eye sees only one of the images.

There are many ways to view 3D images:

Stereo Pairs (stereoscope: separate display for each eye)
Shutter glasses (most common method)
Color filter glasses (used in some old 3D movies)
Polarizing glasses (used in some modern 3D movies)

Stereo pairs

Typical stereo pair images are two separate images of the same object taken a few inches apart. In this method, the two images are not interlaced but rather presented side by side (left eye image on left and right eye image on right). The images are directly viewable using parallel "free-viewing" glasses which allow each eye to only see its correstponding image.

LCD shutter glass method

In the LCD shutter glass 3D display, the left and right images are alternated rapidly on the monitor screen. When the viewer looks at the screen through shuttering eyewear, each shutter is synchronized to occlude the unwanted image and transmit the wanted image. Thus each eye sees only its appropriate perspective view. The left eye sees only the left view, and the right eye only the right view.

Color filter glasses

Color filter glasses are one of the oldest methods of viewing 3D images or movies. The system works by feeding different images into your eyes. The different color filters allow only one of the images to enter each eye, and your brain does the rest. There are two color filter systems: Red/Blue and Red/Green.

Polarizing glasses

This method is more comonly used in today's 3D movie projections. The audience must wear special glasses which have two polarizing lenses which have their polarization directions adjusted to be 90 degrees different. This makes is possible that left eye sees it's picture without problems but everything ment to right eye (sent out at different polarization) seems to be black. Same applies also to right eye.