By Marissa Cevallos, Science News
A palm-sized Princess Leia pleading for help is no longer the stuff of science fiction.
Arizona researchers have created the first 3-D hologram movie that plays almost in real time, they report in the Nov. 4 Nature. It’s the fastest known demonstration of telepresence, where a 3-D hologram depicts a scene from another location.
The key to the invention is a new type of plastic that can refresh the hologram once every two seconds. While that’s too slow to watch the World Series in 3-D, the researchers estimated holographic TV could be coming in seven to 10 years.
“It is very very close to reality,” says physicist Nasser Peyghambarian of the University of Arizona in Tucson. “Something that was science fiction is something we can do today.”
Holograms are created when light bounces off a sheet of material with grooves in just the right places to project an image away from the surface, like on some credit cards. The image is even crisper when the illuminating light waves march in step, as they do in a laser.
Holographic video is already possible, albeit painfully slow—the U.S. military records enemy territory in 3-D, but refreshing each frame of the video can take an entire day. The Arizona team created a quicker way to play holographic video in 2008, but with that method each frame still took four minutes to generate. Now, after two years of optimizing the plastic, they’ve cut the time to just two seconds.
Sixteen cameras snap pictures of an object that are piped into a desktop PC, which processes the data. Then the computer shoots the holographic pixels, or “hogels,” electronically to another location. There, the hogels are transformed into an optical signal and transmitted by a laser onto a plastic screen, much like a projector shines light onto a white screen to play a movie.
When this light hits, the plastic screen undergoes chemical reactions that temporarily record the most recent set of images in the data stream.
A particular color of light illuminates the plastic and—voila! Light scatters in just the right way to recreate the original image. Then, the new plastic can be erased, creating a clean slate for the next image.
But unlike Princess Leia pleading for help, the new hologram can’t float in space. Instead, Leia’s image would appear to stick out from a screen’s surface. “Star Wars was a great movie and we got a lot of feedback because of Princess Leia,” says Arizona physicist Pierre-Alexandre Blanche. But the idea of a hologram hovering in mid-air is impossible. “You need a screen, a support to display the image.”
Within a few months, the Arizona team hopes to create holographic video on a tabletop, where laser light shines up from underneath a table.
Before holographic devices hit living rooms, though, the holograms need to be bigger and faster. The researchers will have to upgrade their 50 hertz laser to one that operates at faster gigahertz speeds, scale up the size of the screen, and miniaturize their instrumentation.
“But I don’t think there’s any fundamental physics that would prevent us from getting there,” Peyghambarian says. The exact technological route to holographic TV is still up in the air, as other scientists take different approaches to creating moving holograms.
“Each group is doing it in a slightly different way and there hasn’t emerged a single, universally agreed-upon way,” says Michael Bove of the MIT Media Lab. “Right now, each technology has some limitation.”
The new work is another step toward bringing holograms from fringe fascination to consumer acceptance, says Seth Riskin, manager of the holography initiative at the MIT Museum, which houses the world’s largest collection of holograms.
“Holography is coming into its own, finally,” says Riskin. “It’s kind of like a seed finally finding its soil. It’s been alone, floating there. It has a ground within to grow now.”