As with the cinematic stereoscopy systems we described in Part One of this feature, the 3D image has to be broken down into two 2D images, one designed for the left eye, one designed for the right. A sequential system does this by displaying frames for these two images alternately at a smooth 60 frames per second. Active LCD shutter glasses, communicating with the 3D source via an infrared link, work at the same speed, alternately blocking light coming into the left eye, then the right, so that the left eye only sees the frames targeted at the left eye, while the right eye only sees the frames targeted at the right.
Existing versions of this technology, as used in Samsung and Mitsubishi 3D-capable DLP displays, don't actually display either the left-side or right-side view at a full 60fps per eye. Instead, each image is presented as a 'checkerboard' pattern, effectively halving the resolution of the image, but in a less perceptible way than halving the resolution on either the horizontal or vertical axis would do, and so reducing the sort of bandwidth you need to display two full HD images at 60fps each. Panasonic's proposed system does things differently, streaming and displaying a full 1080p image for each eye. This means that Panasonic's system, of all the systems currently being outlined, is the only one that will give you movies in full 1080p 3D. Interestingly, nVidia's 3D Vision gaming platform is based on sequential 3D technology, and is supposed to run at 1080p at 120Hz or at 60Hz with TVs that support the 'checkerboard' format.
The second system relies on good old polarization. Here both left-eye and right-eye images are displayed simultaneously, with alternate horizontal or vertical lines - depending on the exact system used - carrying the image for the left eye, then the right. These alternating lines are then polarized by a system of lenses or micro-polarizers, and directed to the correct eye using the same kind of passive, polarized lenses used in, say, current RealD cinema presentations. LG has an interesting spin on the same idea, which uses a combination of polarizing lenses and a special anti-reflection coating to, effectively, run a stereoscopic display from a single LCD screen. In the future, it's hoped that OLED technology may allow the light to be polarized during transmission, removing the need for lenses altogether. Researchers at the Japan Advanced Institute of Science and Technology are working on just such a system right now.
Finally, we come to the system that throws away those damn glasses altogether. Lenticular 3D displays use a system of rod-like lenses of the sort you might recognise from those weird moving pictures found on children's stickers, birthday cards and bookmarks. Placed diagonally over the image, the lenses effectively deliver slightly different views to each eye, providing a 3D image without any need for polarizing lenses or filters. Now, lenticular systems have been around for a while, and the problem has always been that the 3D effect only works from a sweet spot. As soon as you moved out of that sweet spot, the image lost its 3D characteristics and its clarity. The new lenticular systems get around this, however, by providing 3D 'views' for up to nine different - and larger- sweet spots. In theory, this should make it workable within the average family home.