See that teensy Tinkerbell-shaped light above? That's not CGI -- that's a real floating display, and it's completely touchable too. Mid-air plasma displays aren't that prolific yet, but they're not exactly new either. However, floating lights created using existing techniques can usually burn skin, since every "voxel" (a pixel in 3D space) is made by heating molecules with nanosecond lasers. In order to make them safe to touch, a team of researchers from the University of Tsukuba, Utsunomiya University, Nagoya Institute of Technology and the University of Tokyo, used lasers that fire bursts of plasma every few femtoseconds instead.
A femtosecond is one millionth of one billionth of a second, whereas a nanosecond is one billionth of a second. These shorter pulses can't damage your skin, making the final product touchable. In addition, the objects can respond in real time (e.g., a heart can break in two when touched), as well as give off haptic feedback. At this point, the researchers' femtosecond lasers can only render images up to eight cubic millimeters in size, with resolutions reaching up to 200,000 voxels per second. They're hoping to scale the technology up in the future, though, to become more useful to potential customers. Who knows -- this might be the beginning of interactive holograms, mid-air billboards and maybe even floating touchscreen computers like Tony Stark's.
[Image credit: Yoichi Ochiai/University of Tsukuba]