Science News

Glasses-free 3D displays

Wed, 20th Mar 2013

Chris Smith

Engineers at Hewlett-Packard have come up with a way to deliver 3D images on mobiles, televisions and tablet computer screens without the need 3D gogglesfor users to don a daft pair of tinted glasses.

We see the world in three dimensions because we have two eyes that are separated by about 6cm. Each eye sees, and feeds to the brain, a slightly different but overlapping view of the world. The brain stitches these two inputs together to create the three dimensional experience we perceive.

To recreate this effect using a flat screen, two separate images need to be fed to each eye individually.

Traditionally, this has been done using polarised light and a set of glasses that selectively filter the images destined for each eye.

An alternative approach sends two images from a screen but needs the users head to be in a very limited set of positions in order to appreciate the 3D image. The disadvantages of such systems are obvious.

But HP Laboratories scientist David Fattal and his team have developed a clever way around the problem, creating what's known as an autostereoscopic display.

Their solution is to use microscopic etching techniques to produce a matrix of tiny gratings that can sit atop the display pixels and control precisely the direction taken by light rays leaving the screen surface. A computer is used to turn the pixels on an off in the right order to create the 3D illusion.

In this way a much larger number of viewing zones - presently 14 but 64 should be feasible - can be created, giving users the perception of smooth stereoscopic images.

Using this technology, tilting a mobile phone displaying an image of someone's face, for example, would allow an observer to see around the back of the subject's head.

The manufacturing technique is actually quite simple, and David Fattal estimates that it will be available in the marketplace within 2 years.

More problematic, though, will be pursuading video producers to shoot their footage using the 14, or even 64, different cameras that will be needed to supply the multiple iamge sources the system requires to render the images!

As Cambridge University computer scientist Neil Dodgson puts it in an accompanying commentary in Nature, where the research is published, "All that remains is the more nebulous question of whether humans want or need 3D displays..."


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Comparison with "tinted" specs is a bit of a straw man comparison though. Cross-polaroid or, better, switched LCD glasses are the common way used on 3D TVs. However, it would certainly be better if the need for glasses could be eliminated. The method proposed is simple though I expect that the higher (64 position) system will be what will be necessary to gain market acceptance. It would be interested to see how effective it is. At present the extra realism you gain from having 3D is not great and, of course, for much programme material it is not adding anything useful at all. This system also would not get around the problem of the brain having to compensate for the parallax effect from the 3D not correlating with the focus of the eye. It gives some people a headache apparently. The only true way to do it is using holography but I think this is a long way off. graham.d, Thu, 21st Mar 2013

I have seen a demonstration of a 3D display that operated without glasses, using a lenticular lens over the flat screen.

You had to remain in one of a few optimum viewing zones - directly in front of the screen, or at a few specific angles on either side of the centerline. Other positions looked blurry, or confused your visual system.

This demonstration system never went into volume production, partly due to the lack of content in this format. and wearing 3D glasses gave a better 3D effect, once these systems became available to the public.

Perhaps this new glassless system might have more success for niche applications?

The standards for compressing and presenting video content have been updated to allow multiple viewpoints - but most content providers are just providing two viewpoints (left eye/right eye). Providing tens of viewpoints will demand much more communications bandwidth for mass-market applications. evan_au, Fri, 22nd Mar 2013

You're right, the lens-based system offers a very restricted set of viewing positions. The improvement offered by this system is that the scale of the gratings is sufficiently tiny to mean that it's relatively easy to create a large number of such viewing positions, making it much harder to mis-position the head and therefore miss the effect.

I think the issue will be more what Professor Dodgson says, whether the public really want 3D displays. And to be honest, despite having a 3D button on my telly, the sexy looking 3D glasses pack that came with the screen remains barely used. Now that might be because donning the specs is a faff, or, more likely, that the benefit we achieve from said viewing experience is insufficiently large to make me (and the family) want to bother. Perhaps this new non-glasses system will change that?

Alternatively, I wonder whether - in the same way that a PDF of a research paper feels hard to read on-screen and is better printed out - we are just so habituated to seeing 2D on screens that 3D seems "weird" so we don't take to it? chris, Sun, 24th Mar 2013

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