Stereoscopic displays require glasses or other headgear to prevent each eye from seeing what the other eye should see. One class of these displays split the full image across the screen, with one half representing the left-side image and the other representing the right-side image, using polarisation matched with polarised glasses to present a 3D image. This is called area multiplexing and is the technique used in most 3D movies, which is why you need to wear the glasses to get the full 3D experience. The other class of stereoscopic displays uses a technique called time multiplexing, displaying the left- and right-side images in sync with glasses that block vision in the respective eye simultaneously. As the left-side image is displayed, the left lens of the glasses becomes transparent and the right lens becomes opaque, and vice-versa when the right-side image is displayed. This must occur at twice the speed of normal vision to eliminate flicker.
Autostereoscopic display, on the other hand, such as that used in certain 3D handheld consoles, don’t require glasses because they use an additional piece of hardware that directs the image towards the appropriate eye. Here, again, multiplexing is done either by time or by area, but it is more common to multiplex by area. The image is split into left and right sides again, but with autostereoscopic displays, each side of the image is divided into strips, and placed alongside one another, alternating between left and right sides. This diagram will help clarify.
Who knew it could be so hard to use your eyes?
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