Click to viewHolography has just gained a fourth dimension, bringing the prospect of Star Wars-style holographic telepresence into the real world.
Ever since Emmett Leith and Juris Upatnieks made the first laser holograms in 1963, holography has been the future of three-dimensional imaging. Once created, a hologram can be illuminated to create a pattern of light waves that replicates the light reflected by the original object, generating a 3D image without the need for special glasses.
As such, holography seems an ideal medium for three-dimensional telepresence, like the famous "hologram" of Princess Leia in the first Star Wars movie. During its 2008 presidential election night coverage, CNN's coverage used what appeared to be holographic technology, with anchor Wolf Blitzer talking face-to-face with a virtual 3D correspondent, Jessica Yellin – but the impressive visuals were added to the camera feed rather than being projected live onto the studio floor.
By election night 2020 the pair might be able to have that face-to-face conversation, though, according to Nasser Peyghambarian at the University of Arizona in Tuscon. With colleagues and researchers at the Nitto Denko Technical Corporation in Oceanside, California, Peyghambarian has devised a holographic system that can handle near-real-time motion.
The key is a complex new plastic material the researchers have developed, which changes its refractive index when illuminated by laser light. Such photorefractive materials have been studied for years, but this is the fastest and most sensitive known, able to record and display a different holographic image every 2 seconds.
"They have taken it to a new level in sensitivity and area," says Joe Perry of the Georgia Institute of Technology in Atlanta, who was not involved with the work.
To demonstrate its potential for telepresence applications, Peyghambarian and colleagues photographed an object from 16 different angles with conventional video cameras. Computers then converted the video images into the form needed to make a hologram, and sent that information to a "receiver" some distance away using standard Ethernet communication protocols. The receiver contains a laser that interpreted the image data to "write" 100 holographic stripes into the 10-centimetre-square chunk of plastic over a period of 2 seconds. Next, a red, green and blue LEDs illuminated the plastic, recreating the phase, direction and amplitude of light waves reflected off the original object and forming a colour 3D holographic replica.
Rather like a rewritable DVD, writing a new hologram into the plastic erases the old one, allowing the researchers to create holographic video, albeit at a very low "frame rate".
The holographic images aren't detailed, but they have true depth (see video). Larger images and better colour and resolution would be needed for commercial systems, though. The time resolution would ideally be improved from 0.5 frames per second (fps) to 30 fps for telecommunication, but many potential applications in medical and industrial imaging could use the lower rates already achieved, said Peyghambarian.
An image like Princess Leia "is no longer science fiction, it is something you can do today", he said at a press conference. However, he added that commercial applications are at least seven to 10 years away.
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