While screens that let you watch 3D without wearing glasses have actually been around in concept form for years, they’ve never really been more than ‘sci-fi’ prototypes designed to create a buzz at a show.

That changed dramatically at the CES when Toshiba announced that it will be launching glasses-free, big-screen 3D consumer TVs by next April at the latest.

A few other brands had prototype glasses-less 3D screens on show too, most notably Sony. But Toshiba was the only brand talking about anything coming to market in the remotely near future.

Everyone wants glasses-free 3D, of course. All the manufacturers know that. But the bottom line is that technically, it’s extremely difficult to achieve.

The technology currently used is broadly known as autostereoscopy. And as you would expect, it requires the screen to carry some form of optics system that enables different images to arrive simultaneously to each eye.

The most common solution to this problem is to use lenticular lenses. These have a distinctive grooved surface - created by their use of an array of cylindrical lenses - that allows them to subtly adjust the output angle of alternating lines of the picture so that each eye sees a slightly different image.

However, a big catch is that since the lenticular system is so based on optical angles, there’s usually a pretty defined ‘sweetspot’ you have to sit in in order to get a sharp 3D effect.

Lenticular lens detail

This is problematic enough if there’s just one viewer, but if you add a few more, all viewing from different angles, it becomes a huge issue. Experimenters with lenticular 3D technology have tried to get around this by using perpendicular lenticular sheets, but this makes each viewers’ sweet spot even smaller.

Toshiba has come up with an interesting extra innovation here, though. For its take is to replace each single pixel in the image with nine pixels, with each pixel designed to serve a different viewing point - giving you support for up to nine different 3D viewing positions.

Another glasses-free 3D technology that Sharp has been playing with is the so-called parallax barrier system. This uses switchable liquid crystals that can be used to control the direction that light emerges from an LCD panel. So the image arriving at each eye can be individually controlled by modulating the liquid crystal ‘barrier’. We’re seeing no signs, however, that this approach is as close to becoming a commercial reality as the lenticular method.

Glasses-free Toshiba 3D TVs

The ‘killer app’ of glasses-free 3D TVs is, of course, that you don’t need to wear glasses to enjoy 3D. But to be honest, nothing we’ve seen so far - and this includes the early Toshiba samples on show at the CES - makes the advantage of not wearing glasses trump the technology’s major flaws.

First, we’ve found glasses-free 3D pictures generally looking rather soft and blurred. Second, unless you use a really high-resolution screen - ideally 4k2k minimum - and extremely fine lenticular lenses, you are going to lose a significant amount of resolution versus an active 3D glasses system. Third, the 3D effect can break down if you’re not viewing it from within a pretty small area. And finally, you can clearly see vertical seams in the picture if you move around much at all while watching a lenticular 3D screen.

Again, to be fair, Toshiba has also introduced new technology in its large glasses-free 3D TVs that softens these seams, so they’re a bit less in your face. But even sudden appearance of a stripe of vertical blurring if you move your head to the wrong place is still mightily distracting.

For all these reasons, we really have our doubts about the quality of Toshiba’s glasses-free 3D ground-breakers. And tellingly, the two small glasses-free 3D TVs Toshiba has launched in Japan have sold unexpectedly poorly.

In fact, we have our doubts that glasses-free 3D will EVER become a reality - at least using any of the technologies currently being used. But it will nonetheless be interesting to see if Toshiba’s bold move accelerates the move of others along the glasses-free road.

Right, that’s it for 3D display technologies. Next week we’ll look at the different 3D source formats that are out there, and what part they might play in the eventual outcome of the 3D display war we’ve been looking at today.

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