How 3-D TV Works

Active Glasses and 3-D-Ready Televisions

In the last few years, engineers have come up with a new way to create three-dimensional images in movies and on television sets. You still wear 3-D glasses with this method, but they don't use colored lenses. The method doesn't compromise the color quality of the image as much as anaglyph glasses do. It also doesn't require you to put a polarization film on your television screen. What it does do is control when each of your eyes can view the screen.

The glasses use liquid crystal display (LCD) technology to become an active part of the viewing experience. They have infrared (IR) sensors that allow them to connect wirelessly to your television or display. As the 3-D content appears on the screen, the picture alternates between two sets of the same image. The two sets are offset from one another similar to the way they are in passive glasses systems. But the two sets aren't shown at the same time -- they turn on and off at an incredible rate of speed. In fact, if you were to look at the screen without wearing the glasses, it would appear as if there were two sets of images at the same time.

The LCD lenses in the glasses alternate between being transparent and opaque as the images alternate on the screen. The left eye blacks out when the right eye's image appears on television and vice versa. This happens so fast that your mind cannot detect the flickering lenses. But because it's timed exactly with what's on the screen, each eye sees only one set of the dual images you'd see if you weren't wearing the glasses.

For several years, LCD and plasma screens weren't good candidates for this kind of technique. The refresh rates -- the speed at which a television replaces the image on the screen -- were too low for the technology to work without the viewer detecting a flicker from the glasses. But now you can find plasma and LCD displays with incredibly fast refresh rates.

The refresh rates are just one part of a television qualifying as 3-D ready. Learn more in the next section.