Hologram messaging coming of age
It has long been a staple of science fiction films - the idea that you could send a moving 3D representation of someone to any location, even on another continent.
Now, US researchers claim this fantasy is very close to reality.
A University of Arizona team says it has devised a system that can make a holographic display appear in another place and update it in near real-time.
The group tells the journal Nature that the development has huge potential.
"We foresee many applications, for example in manufacturing," said Professor Nasser Peyghambarian from Arizona's College of Optical Sciences.
"Car manufacturers or airplane manufacturers could look at holograms and design their systems in real time. They could look at 3D models and make changes as they go.
"Imagine a very complicated surgical procedure - then with this system surgeons around the world could participate. They could see the whole procedure in real-time and in 3D, and help out," he told BBC News.
Ever since the Princess Leia character was magically projected in 3D during the original Star Wars film, people have wondered if such a technology might really be possible.
The system demonstrated this week is far from the finished product, but it gives a very strong hint of what might be achievable with further refinements.
At its heart is a new plastic screen material that will record 3D holographic images time and time again, every two seconds.
In the set up described in Nature, 16 cameras recorded 2D images of objects and people from multiple angles That information was then sent to another location using a computer connection.
At the remote site, a laser was used to "print" the visual information on to the new photosensitive polymer. The 3D image composed of the 16 perspectives decays naturally, but the laser can write the next "frame" before it completely disappears.
The team previously gave an update on its work in a 2008 Nature paper. Back then, its 10cm-by-10cm, one-colour screen could only be updated every four minutes.
The new 45cm-by-45cm, multi-colour screen is re-written in a hundredth of the time.
No glasses are needed to see the images, merely some form of illumination.
And unlike "standard 3D" TV or films that produce a simple parallax effect in which each eye is offered one slightly different perspective on the same object, the scope of the holographic images is built from the many views of numerous cameras.
Theoretically, say the researchers, it should be possible to project a full 360-degree hologram, one where an individual standing on one side of the screen sees the front of a printed object while someone standing on the other side of the screen sees its rear.
So while it is not quite Princess Leia being projected in free space, the system could conceivably produce a very rounded telepresence.
The team concedes its prototype system has a lot of development ahead of it, but the researchers believe the first commercial products could be available in a few years' time.
One key advance needed is the ability to re-print the polymer at least 30 times a second. This would give a much more realistic sense of movement. The screen itself needs to be made much bigger and additional cameras would have to be incorporated to provide more detail and at significantly higher resolutions.
And all this would have large processing and bandwidth implications which would likely limit the system's use to high-end applications - certainly in the early stages of commercialisation.
"Coming up with improvements to the polymer is going to take some time, and also coming up with better lasers is going to take some time. In about two to three years, we should be able to do those aspects," said Professor Peyghambarian.
"And then transferring that into a product is going to take another three to four years. But I don't believe there is any physics that would prevent us from getting there."