Two-dimensional (2D) glasses enable a viewer to watch a three-dimensional (3D) movie like a regular two-dimensional movie. It does this by altering the images accessible to the eye. Without 3D glasses a three-dimensional film looks blurry, because there are two major images that are projected onto the screen in slightly different places. 3D glasses allow one of these images into each eye and blocks the opposite image in order to created the three dimensional effect. 2D glasses create their effect by blocking and allowing the same image in each lens. They can be purchased or made out of two pairs of 3D glasses.
The glasses work with passive polarized 3D, which is the kind typically exhibited in a movie theater. Early versions of the glasses have not been able to accommodate IMAX theater 3D, which creates images with a different kind of technology. They also have not worked for some kinds of television 3D.
If the kind of 3D glasses used in movie theaters will work on a television, then the 2D glasses are claimed to work as well. These are known as passive 3D TVs. The glasses will not work on televisions made to display 3D with more complex battery-powered glasses. These sets use a different kind of display known as active shutter.
2D glasses have the appearance of regular glasses for vision correction. They are claimed to have the same effect on the viewer as watching a 2D movie. Some glasses have been made so that it is possible to switch to 3D for select scenes.
It is possible to make 2D glasses using two pairs of 3D glasses, such as the type distributed at movie theaters. The first step is to remove one lens each from opposite sides of the glasses. Then to make each pair 2D, the lenses would be re-inserted into the opposite pair of glasses. Each pair of glasses will accept and reject one projected image. Though the images in each pair of glasses will be slightly different, the difference should not be dramatic enough to be noticeable to a viewer.
2D glasses are often marketed for people who get headaches from watching 3D for long periods. They can be used by individuals who wish to view a movie in 2D, but who are with companions who prefer 3D. The glasses can also be useful for those who live in areas where there may only be a 3D option available for certain movies.