Three- dimensional (3D) anaglyph glasses are pieces of eyewear designed to convert specially encoded two-dimensional (2D) images into three dimensions. They feature one red and one blue or cyan, lens to filter different parts of the anaglyph image reach which eye. Thanks to their simplicity and low cost, 3D anaglyph glasses remain ubiquitous in 2011, even though superior 3D vision technology exists.
The human visual processing system uses the differences between the images captured by the right and left eyes to perceive depth. With a regular 2D image, there is only one "eye," usually in the form of a camera lens, capturing the original image, eliminating the information necessary to create depth cues. To capture a 3D image, content creators typically use two cameras running at the same time to capture the image from two slightly different angles, mirroring what two eyes do. The images are then combined together using any of a number of technologies, such as anaglyph, to then be decoded when the viewer sees the image.
In an anaglyphic 3D image, one of the two capture devices has a red filter over its lens and the other has a blue or cyan, which is close to turquoise, filter over its lens. Those tinted images are superimposed over the other and printed. When the viewer wears a pair of 3D anaglyph glasses, the colored lenses direct the two different images to each of his eyes, and his brain then merges the two images into one 3D image.
3D anaglyph glasses are typically quite cheap. The cardboard versions frequently are packed into movies, books, and even cereal boxes as giveaways. For those who need a higher quality 3D image, 3D anaglyph glasses with plastic or glass lenses are also available, albeit at higher cost. The best of these glasses not only filter color but also make up for the human eye's differing ability to resolve different colors, giving a more accurate view of the decoded 3D image.
Anaglyph technology has been around since the 1850s. When images were produced in black and white, it was an excellent technology since the compromises in color fidelity required by the wearing of colored lenses were a non-issue. With modern full-color images, anaglyph 3D is much less suitable as the colors that it uses to encode 3D information are also present in the actual image. Anaglyph 3D glasses have been gradually being replaced by polarized glasses or glasses with liquid crystal display (LCD) shutters, both of which prevent one eye from seeing the other eye's image. In addition, 2011 saw the first wide release of glasses-free 3D applications on handheld video games and cell phone screens.