Tucked away in the Sound and Vision department of Harrods is a 42in LCD television set. As a not-for-sale display model, it draws only the occasional glance from the tourists and Christmas shoppers packing the store. Despite its unexceptional looks, though, this item of hardware may offer the answer to that great unsolved problem of technology: three-dimensional television.

The LG True 3-D television is one of a new generation of screens that can create a 3-D image without the viewer having to wear irritating colour-filtering goggles. And unlike previous prototype 3-D televisions, which have been small and have provided only modest picture quality (because a lot of detail is lost in the process of adding apparent depth to 2-D images), it can be manufactured in conventional television sizes to provide pictures of impressive clarity.

Philips is also getting in on the 3-D act. Last week the Dutch company showcased a 56in Quad Full-HD screen, which it claims has a resolution four times higher than that of a conventional Full HD television. “Even allowing for the reduction in quality as a result of adding the 3-D effects, this screen still delivers footage in high definition,” said Bjorn Teuwsen of Philips 3D Solutions. Impressively, this would make it the first television screen to be both 3-D and HD.

Both the LG and the Philips prototypes achieve their 3-D effect through the use of transparent cylindrical lenses known as lenticules; according to those who have viewed both, the Philips makes far better use of that technology.

A sheet of tiny lenticules is fixed onto a high-resolution LCD display in such a way that each eye sees a slightly different view of each image pixel. The effect is akin to those 3-D plastic postcards that look a bit like a hologram if you view them at the correct angle. The underlying design for this was first conjured up by Sir Charles Wheatstone, a Victorian inventor, way back in 1840.

The results are impressive, but with one striking drawback: watching the screen can sometimes make you feel seasick. This is a perennial difficulty, explains Neil Dodgson, an expert on 3-D screens at Cambridge University. “Film-makers have traditionally tended to overdo 3-D effects in order to show off the technology,” he says. “If the two sets of muscles in your eyes [focus and orientation] are overworked as a result of keeping up with the 3-D, your brain receives conflicting signals and you begin to feel sick. You need to be a skilled film-maker to avoid giving your audience nausea.”

The big question is: assuming the public has an appetite for 3-D films, where will the content come from?

There are three principal sources. The first is footage originally created on a computer. “It’s fairly straightforward to make computer-animated 3-D content,” says Dodgson. And it’s no problem for advertisers to magic up 3-D footage of, say, a beer bottle that spookily seems to float towards you.

A 3-D version of the children’s computer-animated film Chicken Little enjoyed a successful run in 2005, although it was restricted to the few cinema screens equipped with the required 3-D digital projector. There are still only about 1,500 of them world-wide. Out in the UK next February is Bolt, a 3-D animated Disney film about a dog – voiced by John Travolta – that believes it has superpowers.

The process is more complicated when it comes to live-action films, though. Footage must be “shot in stereo, usually with cameras that have multiple lenses, to achieve the stereoscopic effects”, says Teuwsen, adding: “This gives an astonishing 3-D effect, no doubt about it, but the result is more suited to the cinema than the small screen.”

Few film-makers have so far embraced the idea of shooting with stereoscopic cameras, but the numbers are growing. Tim Burton is one director to give it a whirl: he is making a version of Alice in Wonderland in 3-D, starring Johnny Depp and Helena Bonham Carter. Another is James Cameron, the director of Terminator and Titanic. His next big movie, Avatar, was shot in stereo, and there are plans to release an accompanying 3-D game. As with all the 3-D cinema releases, an Avatar spin-off game would probably use the type of technology that requires you to wear 3-D glasses.

There is huge potential for the games industry in the technology. Plugged into a suitable games-playing PC, the new screens can create a convincing 3-D effect (most existing PC games are already 3-D-compatible).

Another area in which 3-D can add realism is sporting events. The NBA (National Basketball Association, which runs American basketball) is experimenting with filming basketball matches with stereo cameras.

The widest-ranging, most exciting source of future 3-D material, however, will be conventional 2-D films converted into a format that works on the new 3-D screens. This is eminently possible, according to experts. Ben Nicholls, a director of PPC, an advertising postproduction company based in London, says: “There’s no reason you couldn’t recreate Casablanca in 3-D, though it would be a challenge because the footage is complex. Having said that, the conversion technology is growing more powerful all the time.”

To be clear, this is not - at least for now - a matter of popping a regular DVD into a special 3-D disc player, then sitting back to savour Ingrid Bergman’s luscious pout as it looms towards you.

The conversion process is painstaking and requires powerful equipment and skilled technicians to reengineer the footage. “A good print of any classic film could be converted into 3-D if there was enough will to do so,” says Nicholls. This is because video captured on 35mm film stock is of such high quality that any loss of resolution should be unnoticeable on a relatively small screen. “If it’s done badly, the results can look a bit like cardboard cutouts,” he adds, “but if it’s done well it can give you a genuine taste of the 3-D movie experience without being in a cinema.”

One fly in the ointment will be the stiff cost of the first generation of commercial 3-D screens. Philips’s smaller, 42in screen costs around £5,000 and is not sold on the high street, as it’s intended for advertising display in shops, bars and showrooms. And when it goes on sale to trade customers in mid2009, the 56in Philips Quad Full-HD panel is expected to cost an eyewatering £9,000 (though we should remember that conventional flat-panel televisions also cost unfeasibly large sums just a few years ago).

In the meantime, if you’re in a bar watching a television and you notice a beer bottle floating toward you, you will at least know why. Either you’re witnessing the latest in TV technology, or it’s high time you went home.

I CAN SEE THE FUTURE - AS LONG AS I KEEP STILL

Is it really possible to view 3-D footage without wearing the kind of cardboard glasses that make you look like Timmy Mallett? I was sceptical, knowing that 3-D technology had always relied on seeing a split picture through colour filters to give the illusion of depth, writes Emma Smith. So would this new optical trick produce the same effect?

Last week, at a special viewing of one of Philips’s new screens, I found out. As Pinocchio’s nose grew out further and further towards my own during a clip from the animated Disney film, it seemed unsettlingly real. A boxing match was rendered even more brutal as the 3-D effect appeared to put the viewer almost inside the ring, and when a leggy dancer high-kicked out of the screen, I had to stop myself ducking.

There’s one problem: move your head just slightly to one side and the 3-D effect can slip frustratingly out of focus. The viewer must sit in one of six zones - or “sweet spots”; move between zones and the effect blurs. For a fully fledged couch potato, that level of immobility might not be too taxing, but for a fidgety film-watcher like me it was distracting. (Philips says its new Quad Full-HD screen has bigger sweet spots, which should reduce the problem.)

Perhaps even more impressive is the ability to make computer games appear in three dimensions, so that in Lego Indiana Jones, for example, you get the sensation of travelling through the landscape, with Indy’s whip flicking dramatically off the screen.

By overdoing it, 3-D films have sometimes induced motion sickness. The trailer for Bolt, Disney’s new 3-D animation, gives an indication that the genre is coming of age: it avoids the temptation of making 3-D the main attraction and tumbling from one big effect to the next. Soon you find yourself simply taking it for granted and cooing over a cute hamster, so fluffy you want to reach out and stroke it.

TAKE YOUR BRAIN TO ANOTHER DIMENSION

How do we see in 3-D? Three-dimensional objects appear at a slightly different angle to each eye. The brain processes the two views, works out the difference between them and translates the information into a 3-D image.

What does a 3-D TV look like? Like a standard flatscreen television. However, it actually sends out not one but multiple views. As long as you’re sitting in one of several “sweet spots” within a 135-degree viewing angle, each eye will pick up a separate view. This effect mimics the angular differences produced by a three-dimensional object and fools the brain.

How is the effect achieved? There is a layer of convex lenses over the screen, each one scarcely bigger than the individual pixels that make up the panel. When a suitably processed signal passes through them, the lenses produce multiple sets of paired images aimed at up to six “sweet spots”. If you are within a sweet spot, the brain interprets the paired images as 3-D.