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How Does a Nintendo 3DS Work With No Glasses?

The Nintendo 3DS handheld game console launched in 2011 to much fanfare. People were excited at the prospect that Nintendo had finally solved the difficult puzzle of delivering 3-D graphics without the use of any special glasses. Other electronic devices had achieved this already, but sold poorly, meaning that the 3DS stood to be the first glasses-free 3-D device to reach a mass audience. Nintendo put considerable effort into the design and came up with an interesting solution.

Depth Perception
- To see in 3D, you need to look at two slightly different images at the same time, each depicting the same view from a slightly different angle. In nature, this is no problem: Your eyes sit a couple of inches apart, their different viewing angles enabling depth perception. On a flat electronic screen, however, the illusion of depth is created with two images projected onto the screen simultaneously, viewed through a filter so that your left eye sees one image and your right eye sees the other. Most 3-D graphics technologies so far have relied on glasses to do this filtering. The old-style red and blue glasses used color absorption. Subsequent innovations used polarization instead, allowing for better picture quality. Newer glasses work differently. The screen shows alternating images for the left and right eyes at a fast frame rate, and the glasses respond to radio signals from the projector, darkening each lens variably to produce a 3-D effect.
Parallax Barrier
- The Nintendo 3DS eliminates the need for glasses by incorporating the image filter into the screen itself. This filter, called a ̶0;parallax barrier,̶1; consists of a series of very thin bars running vertically across the screen. These bars block precisely half the screen ̵2; sort of like looking through a window whose blinds are tilted halfway shut. However, the bars use very precise spacing that takes advantage of the different angles at which your eyes view the screen. They block half the screen from your left eye, and the other half of the screen from your right eye. The result is that you can see the entire screen, but in a series of alternating vertical ribbons that, respectively, only one of your eyes can view.
Spliced Images
- The 3DS puts two images on its screen simultaneously. One image goes to the ribbons that only your left eye can see, and the other image goes to the ribbons that only your right eye can see. These two interspersed images create the illusion of depth on the flat screen̵2;and thus the 3-D effect. The 3DS needs a very high horizontal resolution so that each vertical ribbon is too narrow for you to notice the discontinuity between the left-eye image ribbons and the right-eye image ribbons. To that end, the 3DS upper screen runs at a total resolution of 800 by 240 pixels ̵2; or 400 by 240 for each eye. Only the upper screen of the 3DS has 3-D graphics. The lower screen remains a two-dimensional touchpad.
Limitations
- For the three-dimensional effect to work, you must hold the 3DS at exactly the correct distance away from your face. The device comes with a slider so that you can adjust this distance to suit your comfort level. You also must point the 3DS directly at you, rather than tilting it off to one side. These limitations pose problems for players who move their 3DS around while they play. Nintendo has said it will reduce these problems in future versions of the 3DS. As of September, 2011, the 3DS had sold only about 4.3 million units worldwide ̵2; impressive numbers in absolute terms, but well below Nintendo̵7;s expectations.

Nintendo DS