3-D (three-dimensional) glasses provide depth and a sense of three dimensions to two-dimensional images. They reached a height of popularity during the 1950s with the advent of 3-D feature films.
Traditional 3-D glasses have one red acetate lens, usually over the left eye, and one blue acetate lens encased in white cardboard frames.
3-D glasses work by presenting two slightly different perspectives of the same image. To take advantage of traditional red-and-blue 3D glasses, one version of the image is filmed in red, the other in blue. The 3-D glasses present a different perspective to each eye, tricking the brain into forming one three-dimensional image.
Polarized 3-D glasses don't have colored lenses. Instead, they use dark lenses to restrict the passage of polarized light to the eye, creating the same three-dimensional illusion.
Charles Wheatstone invented 3-D anaglyphs in 1838, paving the way for the eventual development of 3-D entertainment. "Bwana Devil," released in 1952, was the first color 3-D feature film.