A new glasses-free 3-D display would use lasers to create giant images outdoors for electronic billboards, stadium events, and rock shows, researchers say.
The illusion of 3-D comes from how our two eyes see two slightly different views of the world because they are separated by about 6.4 centimeters. The brain fuses those images into a 3-D model of the world.
Whereas a 2-D display shows only a single flat image, 3-D displays present a different image to each eye. Nowadays, 3-D movies and TVs show each eye a different image either using polarized glasses or using glasses that coordinate with the TV to shutter one eye then the other.
Recently, engineers have developed glasses-free 3-D displays that use screens whose pixels send light in specific directions, as opposed to conventional 2-D display pixels, which send light in all directions. As such, these so-called autostereoscopic displays can project a different image into each of the viewer's eyes.
Now engineers in Austria have developed a laser-based autostereoscopic display based on lasers that may potentially have much greater resolution and brightness and could lead to huge displays to feature 3-D images outdoors.
The prototype, developed by scientists at startup company TriLite Technologies in Neutal, Austria, and the Vienna University of Technology, is made of a three by five grid of 3-D pixels, or "trixels." Each trixel is made up of three laser diodes, a microscopic lens, and a rotating microelectromechanical systems (MEMS) mirror. The mirror deflects the laser beams so that viewers see different images on their left and right eyes. Each trixel is slightly less than 1 cubic centimeter in size.
"There is something magical about walking around and seeing completely different patterns on one and the same screen depending on the direction you are looking at it," says researcher Jörg Reitterer, an electrical engineer at TriLite Technologies and a doctoral student at the Vienna University of Technology.
The prototype uses is only red lasers and has just 15 pixels. But everything starts small.Photo: Vienna University of Technology
The pixels in previous large autostereoscopic displays could only send light to some of the viewing zones in front of those displays and not others. This limited the resolution and brightness of the 3-D images seen in any one of those zones. In contrast, each trixel in this new display sends light to all its viewing zones, potentially leading to much greater resolution and making it bright enough for use even in sunlight. In addition, instead of the relatively limited number of viewing zones that other autostereoscopic displays are limited to, the new system can theoretically have thousands of viewing zones, Reitterer says.
One potential concern is that lasers can damage eyes. However, Reitterer says the lasers in their display scan back and forth so rapidly that any point they shine on receives relatively little light energy—an amount similar to that given off by the LED screens in New York City’s Times Square.
In this first prototype, the Vienna team only used red laser diodes due to the limited availability of green and blue laser devices. They are now working on a second prototype to display full-color images using trixels that each have red, blue, and green laser diodes , and Reitterer says that scaling up to a display with many trixels is not a problem. TriLite plans to finish the second prototype by the middle of this year, with a commercial launch scheduled for 2016.
The engineers detailed their findings in the 3 November issue of the journal Optics Express and will present their first prototype at the Photonics West conference in February in San Francisco.
Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum. He has written for Scientific American, The New York Times, Wired, and Science, among others.