A holographic display shows a 3D image of a man [center image above]. The image's three-dimensional nature becomes apparent when viewed from different angles [left and right images]. The display can update the hologram every 2 seconds. Faster refresh rates would make 3D telepresence possible. Images: University of Arizona
A holographic video system like the one Princess Leia uses in Star Wars is now one step closer to reality.
Researchers report today that they've built a holographic display that can show three-dimensional color images of a person in a remote location, with the images updated in almost real time -- a precursor to holographic telepresence.
This is the first time researchers demonstrate an optical material that can display "holographic video," as oppose to static holograms found in credit cards and product packages. The prototype looks like a chunk of acrylic, but it's actually an exotic material, called a photorefractive polymer, with remarkable holographic properties.
Nasser Peyghambarian and colleagues at the University of Arizona, in Tucson, designed the material -- a complex compound referred to as PATPD/CAAN, or polyacrylic tetraphenyldiaminobiphenyl/carbaldehyde aniline -- to refract and modulate light in a specific way useful for holography.
The breakthrough, which the researchers report in this week's Nature, is that the material can refresh a hologram every two seconds and give the effect of near real time updating. An early prototype built by the same group two years ago could refresh holograms only every 4 minutes.
Last year's blockbuster movie Avatar generated a lot of interest in 3D technologies. Several electronics manufacturers have demonstrated TV sets with 3D capabilities. But the technology used in movie theaters and TV sets, known as polarization stereoscopy, is different from holography.
Holograms are made with lasers and they use special materials capable of diffracting light in a way that looks to an observer as if it had been scattered by the real object itself.
Image of a fighter jet created on a new holographic display. Image: University of Arizona
Like ordinary displays, the new device is a matrix of picture elements, though in this case holographic pixels, known as hogels. As opposed to 2D pixels, hogels contain 3D information from various perspectives. Each hogel is written with a single 6-nanosecond laser pulse.
The technique is known as holographic stereography. It's been around for some time and is in fact used in large 3D static prints used in marketing materials. But the ability to dynamically update the image has eluded researchers -- until now.
Since its appearance in the original Star Wars film in 1977, 3D telepresence has been a source of fascination. But the absence of a large, updatable holographic recording medium prevented researchers from realizing the concept.
In their 3D telepresence demonstration, the researchers use 16 cameras to take two-dimensional pictures of a person's face at multiple angles. The cameras fire simultaneously every second, and a standard desktop PC converts the 16 views into hogel data and sends it to the laser recording system through an Ethernet link. Each image is 4 x 4 inches (about 10 x 10 centimeters), with 120 hogels. Once a hologram has been written, the laser uses the next available hogels to refresh the images every 2 seconds.
"The development seems like a nice and potentially important contribution to holography," says Paul Debevec, a computer scientist who leads the Graphics Laboratory at the University of Southern California's Institute for Creative Technologies, in Playa Vista. He was not involved in the project. "It seems that the authors have significantly improved the speed with which holograms can be written."
But he adds that the prototype is still small and "two orders of magnitude slower than useful video rates." Other 3D technologies, much simpler and cheaper, could work as telepresence systems, he says. His group developed one such system based on a spinning mirror that was capable of showing a full-size human face, with the image updated at 30 frames per second.
(My colleague Sally Adee tested the prototype; see her "holographified" face here.)
"With respect to 3D telepresence," Debevec says, "what they claim to have taken a step towards appears to be something our 3D teleconferencing system demonstrated two years ago."
Color holograms recorded on the new device. Images: Nature
Peyghambarian and his colleagues acknowledge that their device needs to be bigger and refresh faster. But they say that other 3D telepresence technologies demonstrated before required moving parts, complex projection systems, floating particles, or they were simply optical tricks or computer-generated special effects. In other words, they aren't true holograms.
Advanced holographic system, the researchers say, could find applications in telemedicine, prototyping, advertising, updatable 3D maps, and entertainment.
"As an example, in telemedicine and especially for brain surgery, surgeons at different locations around the world could use the technique to observe in three dimensions, in real time, and to participate in the surgical procedure," they write in the Nature paper.
The project also included scientists from Nitto Denko Technical Corp., in Oceanside, Calif., the research arm of a Japanese company that makes semiconductor and optical products.
Is this the technology that is going to bring Star Wars holographic telepresence to our homes?
After watching videos of the prototype, I'm underwhelmed. The researchers claim this is getting us close to holographic telepresence, but we're clearly still far, far away. Lightsabers might come first.
According to the researchers, the movie below "shows the concept of 3D telepresence." The device is displaying holograms of individuals located in a different room. Note that in the first hologram the man is smiling; the next time the hologram is refreshed, after several seconds, he's not smiling anymore. (Don't ask me about the second guy with the glasses at the end -- I don't understand why they show him if it's just a static image...)
This movie shows a series of 6-nanosecond laser pulses writing an image in about 2 seconds.
Videos: University of Arizona