For anyone who grew up in the 1970s, it seemed that hardly a week went by without technologists unveiling another triumph of converting science fiction into fact. From moon-shots to microprocessors and mobile phones, nothing seemed beyond their power.
Since then the flow of truly astonishing breakthroughs seems to have tailed off. Quite why is a matter of debate. The end of the Cold War and its colossal military R&D budgets didn't help. Then there is the fact that scientists have increasingly run up against fundamental limits to what can be achieved in terms of power, speed and compactness. Yet every so often, scientists unveil something straight out of the sci-fi handbook. And last week, a team of researchers in the US demonstrated a classic example of the genre: a holographic projector.
Anyone who saw the original Star Wars in 1977 will recall the scene where a ghostly 3-D image of Princess Leia communicates her plea for help to Obi Wan Kanobi. Even when the film was made in the 1970s, many of the audience would have been aware of the basic technology involved. The idea of so-called holography dates back to the 1940s. By the 1960s it was being used to capture fixed 3-D images of objects in plates of glass. It has taken until now, however, to create a practical moving hologram projector.
The basic problem lies in finding a material that can act like the holographic equivalent of photographic film, and change in response to the moving image. Simple black and white film records just the different intensity of light falling on it at different places; colour film also records the varying hues. A hologram does more, however, capturing not just the intensity of the light, but also its phase - roughly speaking, the point in the light-wave's oscillation at which it strikes the object. This is affected by the shape of whatever the light strikes, and thus gives a way of capturing a precise 3D image of objects - if some means of recording this phase information can be found.
Over the years, scientists have developed many materials able to store the holographic information created when laser beams strike objects. The results are now routinely found on bank-notes, credit cards and passports. But all these are static images; to display a moving 3D hologram of the Star Wars variety requires a material that can be constantly refreshed, projecting the hologram of each successive position of the objects.
Now optical the physicist Professor Nasser Peyghambarian and his colleagues at the University of Arizona in Tucson have created a material that's up to the job. Known as a photorefractive polymer, it can record and display a new hologram every 2 seconds - which, while still not quite in real time, is a huge step in the right direction. Reporting their breakthrough in the current issue of the journal Nature, the team describes how it captures each image via 16 cameras arranged around the object. The data collected by the cameras is used to control two laser beams that combine to put the phase-based information onto the polymer. The image is then generated by shining light from another laser onto the polymer.
This may seem a lot of bother just to create the kind of 3D imagery already in cinemas and coming to homes via TVs. But the effect it generates is light-years away from anything available at the movies. For a start, it's not necessary to wear special glasses or sit in a specific spot to see the image. More importantly, a holographic image really is three dimensional, unlike a "3D movie" image. It's possible to walk right around the holographic image and see it from every viewpoint, just like the original object.
In short, it is just like the projector in Star Wars - which Professor Nasser Peyghambarian admits was his source of inspiration. "From day one", he told Nature, "I thought about the hologram of Princess Leia and whether it can be brought out of science fiction".
He and his colleagues are now looking to boost the refresh rate up to movie standards, and believe that full-size, high definition versions of the technology could be in homes within 10 years. Which is an intriguing prospect, as by then scientists might have unveiled a real-life version of that other famed example of technology from Star Wars, the robot C-3PO.
Versions of his diminutive chum R2-D2 can already be found trundling round homes and offices, performing simple tasks like vacuuming, polishing and mowing the lawn. Yet to go from a dustbin on wheels to a human-like android is a big step, in every sense. Negotiating steps and coping with constantly changing environments is a major challenge requiring lots of sensors, computing power and manoeuvrability.
Technologists are making slow but steady progress, however. Researchers at the Technical University of Munich have come up with a robot that can tidy up in the kitchen, while Mitsubishi has marketed Wakamura, a robotic companion for the elderly or disabled that can hold conversations and even call for help if it thinks something is wrong. But all this sophistication doesn't come cheap. The closest we've yet come to C-3PO - at least in terms of appearance - is Honda's Asimo, which costs £500,000, and doesn't do much apart from walk.
When director George Lucas announced his intention to re-release all six of the Star Wars series in 3D format, many fans were dismayed by his apparent intention to milk the franchise for all it was worth. Now they face the prospect of one day having to pay out all over again - this time for a holographic version with all their favourite characters played by robots.
Robert Matthews is visiting reader in science at Aston University, Birmingham, England