3-D video glossary

Types of 3D technology

• Active shutter: This technology requires glasses that electronically open and close liquid crystal lenses over each eye, synchronized with a 3-D video display. When this display presents a left eye image, the glasses cover the right eye so only the left eye sees the display, and vice versa for the other eye. This process is repeated more than a hundred times per second and is virtually undetectable to the user. Although movies in active shutter 3-D are extremely rare, the technology is often used for PC games in 3-D and 3-D education projection.

• Anaglyph: This is a very old 3-D technology that was once very popular in movie theaters. It creates the illusion of depth by having the two images (left and right eye) filtered in the color spectrum. By wearing the appropriately colored glasses, the eyes see the corresponding left or right eye image, and the visual cortex in the brain translates the difference in those images as depth. Anaglyph is a relatively inexpensive way to view 3-D video, but because images are composited into a single image from the original left and right eye information, they can appear washed out, because the process removes some of the color. Anaglyph 3-D can be viewed on any computer monitor or TV, and while it is most commonly used for home viewing of 3-D movies, some PC games also can be found in anaglyph.

• Passive polarized: This technology is most commonly found in theaters today. It requires light from the projector to be polarized so that it is filtered in a very specific way that does not alter the color. The light projects onto a screen that preserves this filtering upon reflection. Then, glasses with special lenses either block the polarized light or allow it to pass through, depending on the type and degree of polarization. By wearing these inexpensive, plastic glasses, each of the viewer’s eyes sees full-resolution, full-color 3-D images from the corresponding (right or left) projector. Some of today’s more advanced flat-screen technology incorporates a film layer that can polarize light in a similar manner as a theater projector and screen.

Key terms

• DLP Link: This is a communication protocol that uses the DLP chip inside DLP TVs and projectors. The DLP chip sends a flash of light in the transition between left and right images, and the glasses—recognizing this encoded white signal—sync to the image. These glasses do not require an emitter. The glasses work with Mitsubishi and Samsung DLP TVs and with 3-D-ready projectors.

• Hz: The hertz is a unit of frequency. In video parlance, it refers to the number of complete frames per second of video.

• Stereoscopic: Any technique capable of recording 3-D visual information or creating the illusion of depth in an image.

• XGA, SXGA: The Extended Graphics Array (XGA) refers to a display resolution of 1,024 x 768 pixels. The Super Extended Graphics Array (SXGA) refers to a standard monitor resolution of 1,280 x 1,024 pixels and is a step above XGA.