3-D without four eyes

New glasses-free 3-D devices are about to hit the market, and their backers are hoping they\´ll make 3-D spectacles as obsolete as Smell-O-Vision. These gadgets, described as "autostereo" to distinguish them from the kind requiring eyewear, will include not only game consoles like the one I\´ve been playing with but also cameras, cellphones, and tablet computers. Among the first will be autostereo 3-D TVs, just now hitting stores in Japan, and Nintendo\´s 3DS handheld games console, due for release worldwide early next year. To perceive three dimensions, a person\´s eyes must see different, slightly unaligned images. In the real world, the spacing between the eyes makes that happen naturally. On a video screen, it\´s not so simple; one display somehow has to present a different and separate view to each eye. Some systems handle this challenge by interspersing the left and right views; they\´re called multiplexed. Others, called sequential, alternate left and right views. Whatever the approach, the displays then use optical or technological tricks to direct the correct view to the correct eye. For example, the bulkiest glasses used with currently available 3-D TVs are active-shutter glasses. They contain a set ofminiature LCD panels that synchronize with the large LCD screen in the TV. When the main screen is showing an image destined for your right eye, a liquid-crystal shutter in the left lens of the glasses makes that lens opaque, and vice versa. This sequential system switches between images meant for each eye dozens of times a second, creating a smooth 3-D effect. It works well. In theory, at least. According to a survey of 1400 Americans by the market research firm Interpret, a quarter of gamers got headaches from 3-D, a fifth complained of eyestrain, and one in six said that they felt disoriented or dizzy after playing. In a similar survey of 2000 Americans by the market research firm NPD Group, over half said that having to wear glasses would discourage them - - from upgrading to 3-D altogether. And the glasses aren\´t cheap. Hightech 3-D specs cost US $100 or more, and a pair bought from, say, Sony typically won\´t work with a Panasonic or LG Electronics TV.