November 3, 2010 | 1
In yet another instance of science imitating science fiction, researchers are inching toward the sort of three-dimensional "telepresence" technology that Princess Leia used to contact Obi-Wan Kenobi in Star Wars. And whereas Leia’s warning came recorded on a droid, these real-life holograms could one day be broadcast live from one place to another, enabling more lifelike videoconferencing or even telesurgery.
The researchers had demonstrated in 2008 the capacity to write and rewrite 3-D holograms onto a photorefractive polymer using a laser, but doing so took several minutes per image. In the new study, published in the November 4 issue of Nature, the images can be rewritten every two seconds. (Scientific American is part of Nature Publishing Group.) The researchers consider the roughly 100-fold improvement good enough to call their system "quasi-real-time," but a similar speed boost will be needed before the hologram can display fluid motion, which requires a frame rate of several dozen images per second.
"We can take objects from one location and show them in another location in three dimensions," study co-author Nasser Peyghambarian of the University of Arizona said in a teleconference announcing the advance. Unlike 3-D movies such as Avatar, which are stereoscopic (having two perspectives), the researchers’ holograms encode as many as 16 different viewpoints of an object using 16 cameras arranged in a semicircle.
A pulsed laser writes that information into an array of holographic pixels, or hogels, which convey three-dimensional depth by showing different sides of the object depending on the viewer’s angle to the hologram—no special eyewear is needed. It can be used to provide full parallax, Peyghambarian said; viewers can move not only from side to side but also up and down to see different perspectives.
At present the system can handle color, but only by writing separate red, green and blue holograms at different angles. And the prototype system is rather small, just 10 centimeters on a side. Peyghambarian notes that the resolution, size and power consumption of the device will need to improve before real applications are within reach. "I don’t think you can see these in your living rooms in your houses in less than seven to 10 years," Peyghambarian said, adding that moving from the lab to production of devices seems feasible. "I don’t think there’s any fundamental physics that would prevent us from getting there," he said.
Photo of a monochromatic hologram depicting a fighter jet: University of Arizona