Digital 3-D is not your father's -- or your grandfather's -- 3-D.
Stereoscopic imaging has been around since the late 1890s but didn't make a mass appearance until the 1950s, with such horror classics as "House of Wax" and "It Came From Outer Space." This is what most people now associate with 3-D: rows of theater-goers wearing fold-out paper green and red glasses. The 1960s saw a revival of 3-D with titles that included "The Mask" and "Andy Warhol's Frankenstein." But the movement again faded with the lack of blockbuster movies.
The digital 3-D used in theaters and, soon, living rooms, works somewhat differently from its predecessor, which relied on filtering out segments of the color spectrum for the left and right eyes to create the 3-D illusion. For one thing, the image quality is much better, thanks to high-definition digital displays. These don't filter out color. Instead, they present two distinct, full color images to each eye. Two versions of digital 3-D use glasses that present different images to each eye. One is a pair of LCD lenses that alternately opens and closes the left and right lenses in tandem with the screen at speeds as high as 1/60th of a second. Another version uses polarized lenses that filter and separate left-eye and right-eye images.
There's a third method that doesn't require glasses at all: autostereoscopic displays. They create visual barriers between each pixel so that left-eye images are seen by only the left eye and vice versa. But these displays have "sweet spots" requiring that viewers be within a narrow range of the TV set to see the effect.
-- Alex Pham