"When a viewer moves his head or the display, he or she will see a succession of different images," Fattal said. Each image is from a slightly different perspective, creating the illusion of 3D.
The glass layer, the LEDs and the LCD were all used with little modification. So any 3-D display using this design would be much cheaper to make than a true holographic system, which requires a complex systems of lasers.
HP's system also gives it an edge over some of the more complicated systems of mirrors used in other 3-D video displays. HoloAd, for example, is a big and bulky system that relies on projecting images onto glass – not very convenient for a mobile device. There are other complex systems involving exotic technologies such as bubbles and ultrasonic vibrations. None of these are practical for mobile devices.
A simpler system also reduces the computing power needed to create images and video.
Pierre Alexandre Blanche, an assistant research professor in the College of Optical Sciences at the University of Arizona, said that the use of gratings to control the light is a departure from previous attempts to build similar systems. Ordinarily, he said, engineers tried to control the light by putting lenses on top of the glass layer. "This is original, and could be interesting because the light can eventually be better controlled than with lenses," he wrote in an email.
Fattal added that the number of images could be boosted to 64, making the 3-D effect even smoother. And because the light beams that make up the image are all projected in specific directions, the viewing angle is big – approaching 180 degrees. That's an improvement over other attempts at 3-D holograms, many of which require the viewer to be directly in front of the image in order to see the illusion.
Having a wide view is an important characteristic for 3-D imaging on mobile devices, Fattal said, because a phone or tablet is more likely to be held at different angles at different times.
Raymond Beausoleil, an HP Fellow in the Intelligent Infrastructure Lab and a co-author on the paper thinks the first applications will likely be in signage or displays that help people visualize complex data.
"The point of the paper is that there is an approach to 3-D displays that is relatively easy to mock up and seems ideal for small form factor," he said.