Tiny gratings in a visual display could beam images in different directions.
Forget 4G — the future of mobile technology is 3D. Researchers in California have built a prototype three-dimensional (3D) display using a method that might one day be developed to create videos that dance above a tablet, mobile phone or wrist watch and can be viewed from a range of angles.
Holography, the gold standard for 3D display, reconstructs the light that bounces off an object at every angle.
A hologram uses a complicated pattern on a plane so that light passing through it diffracts and interferes to produce a life-like image. But, so far, moving holograms — like the ethereal video of Princess Leia in Star Wars (George Lucas, 1977) — remain in the realm of science fiction. This is because it takes much too long to calculate and produce these shifting patterns for any viewing angle.
Now physicist David Fattal and his colleagues at Hewlett-Packard Laboratories in Palo Alto have developed a sort of 'hologram-lite' approach. It uses simple diffraction — not interference — to create 3D images that can be altered at video speeds, as the authors report in the current issue of Nature.
"It's almost like breaking down a hologram into several finite pieces," Fattal says. It involves etching linear grooves — diffraction gratings — onto a thin glass slab (see image below). Light from light-emitting diodes is then sent sideways through the slab, and some of it is scattered out of the slab in a direction determined by the spacing and orientation of the grooves. The grooves are grouped into circular patterns, each of which sends a light ray out of the slab in a particular direction.