Holographic video chat unveiled

Posted by Emma Woollacott

Star Wars-style holographic video chat is now a big step closer, with the development of a system that can project 3D moving images without the need for special glasses.

University of Arizona optical sciences professor Nasser Peyghambarian has developed a new type of holographic telepresence that allows the projection of a three-dimensional, moving image without the need for special eyewear such as 3D glasses or other auxiliary devices.

The system is a big improvement over computer-generated holograms, which place high demands on computing power and take too long to be generated to be practical for any real-time applications.

Peyghambarian says the technology is suitable for applications ranging from telemedicine and advertisingto pure entertainment.

"Holographic telepresence means we can record a three-dimensional image in one location and show it in another location, in real-time, anywhere in the world," said Peyghambarian, who led the research effort.

"Holographic stereography has been capable of providing excellent resolution and depth reproduction on large-scale 3D static images," the authors wrote, "but has been missing dynamic updating capability until now."

The system is based around a screen made from a new photorefractive material that can refresh holograms every two seconds, making it the first to achieve a speed that can be described as quasi-real-time.

The prototype device uses a 10-inch screen, but the team has already successfully tested a 17-inch version.

Currently, it can present in one color only, but Peyghambarian and his team have already demonstrated multi-color 3D display devices capable of writing images at a faster refresh rate, approaching the smooth transitions of images on a TV screen. These devices could be incorporated into a telepresence set-up in the near future, they say.

The image is recorded using an array of ordinary cameras, each of which views the object from a different perspective. The more cameras that are used, the more refined the final image.

That information is then encoded onto a fast-pulsed laser beam, which interferes with another beam that serves as a reference. The resulting interference pattern is written into the photorefractive polymer, creating and storing the image. Each laser pulse records an individual 'hogel' - a 3D pixel - in the polymer.

The hologram fades away by natural dark decay after a short time, or can be erased by recording a new 3D image, creating a new diffraction structure and deleting the old pattern.

"Let's say I want to give a presentation in New York. All I need is an array of cameras here in my Tucson office and a fast internet connection. At the other end, in New York, there would be the 3D display using our laser system," says
Peyghambarian.

"Everything is fully automated and controlled by computer. As the image signals are transmitted, the lasers inscribe them into the screen and render them into a three-dimensional projection of me speaking."

One of the system's biggest new achievements is full parallax: "As you move your head left and right or up and down, you see different perspectives. This makes for a very life-like image. Humans are used to seeing things in 3D," says Peyghambarian.