Just how does Nintendo plan on offering glasses-free 3D on the upcoming Nintendo 3DS handheld? Since the company already sources its DSi LCD panels from Hitachi, one good guess is that they'll use that firm's so-called interactive autostereoscopic display technology. Already seen in the KDDI Hitachi WOOO phone last year, the system uses a microlens array of tiny convex lenses lined up in columns across the underlying LCD panel. Because the gamer's eyes look at the display from slightly different angles, different pixels can show slightly different content suited to each eye, creating a parallax effect.
The downside to the system is that, since only roughly half the pixels are seen by each eye, you need a relatively high resolution LCD panel in order for the end result to be smooth rather than blocky. Hitachi have already built demo systems using 5-inch WXGA 1280 x 768 panels, however; the DSi XL, for comparison, uses twin 4.2-inch displays.
Because the Hitachi system uses round microlenses rather than regular lenticular bars, the 3D effect is possible when viewing the display from above or below the regular angle of vision, not just when tilting it left and right. Of course, Nintendo haven't made any announcements regarding 3D panel suppliers, nor which technology the Nintendo 3DS might use, but the one main drawback about the Hitachi system - that filming real-life 3D content for the display is time consuming - wouldn't perhaps be such an issue when you're dealing with computer generated gaming graphics.
Hitachi 3D phone demo: