Bringing 3D to your TV


  • Technology
  • Tuesday, 18 May 2010

There are a few different technologies for bringing 3D to your home and we’ll delve into them right now.

ALTHOUGH 3D-capable televisions are just coming out, the technology to bring it to you actually isn’t particularly new and has been floating around for nearly 10 years.

While it is theoretically possible to use the polarising filter technique to provide the image separation required for 3D on modern LCD-based HDTVs (but not plasma TVs) it’s actually impractical because the relatively small size of a HDTV compared with a movie screen means that if a large group were watching the same show on a single TV, the people watching from the sides would have problems viewing the 3D effects properly because polarising technology is so greatly affected by the angle of the glasses in relation to the screen.

In fact, it is this viewing angle problem that limits the use of other promising technologies that provide the stereoscopic effect without the need for special glasses.

For example, Sharp, Hitachi and even Philips have been selling similar panels based on a parallax barrier technology for quite a while now.

These so-called autostereoscopic displays work on an LCD panel with a special filter installed called a parallax barrier.

The parallax barrier is actually similar to those lenticular rulers we had in school which had special vertically aligned lenses which changed the image depending on which angle you tilted the ruler.

Similarly, these 3D displays interlace the left eye and right eye images in a series of alternating vertical lines.

If you numbered these columns from left to right, the left eye image would for example only be found in the even-numbered columns, while the right eye would be in the odd-numbered columns.

The job of the parallax barrier of course is much like Venetian blinds, but oriented vertically and with each alternate slat oriented in such a way so that only one eye would see the odd numbered columns while the even numbered columns can only be seen by the other eye.

Autostereoscopic displays are great because they work without special glasses, but the problem is the nature of the parallax barrier (much like a privacy filter at the bank ATM) means that there is a “sweet spot.”

This sweet spot is the area where the 3D effect can be seen and if your move out further in front, behind or to one side of this spot, the 3D effect would be lost completely.

Shutter glasses

As you can see, bringing 3D to your home HDTV is actually a little trickier than it seems.

However, manufacturers who are now bringing out 3D-capable HDTVs are exploiting an interesting capability of modern LCD (and plasma) panels — the relatively high refresh rates.

For example, the latest 3D-capable HDTVs actually can achieve refresh rates of up to 240Hz (480Hz for plasmas). This means that they can flash an image 240 times per second.

However, since most movie broadcasts only run at 24 or 30-frames per second, there’s a lot of the refresh rate left over.

This is where current 3D HDTV technology comes in — using the persistence of vision method, the left eye image can be flashed, quickly followed by the right eye image and so on.

The method to deliver each image to the appropriate eye is by using so-called LCD shutter glasses.

These glasses are synchronised to the refresh rate of the HDTV itself, and alternately darkens the left lens and then the right lens so that each eye only sees one alternate image at a time.

These alternating images flash so fast that the brain only sees a flicker-free 3D image.

The active shutter glasses method is by far the most popular technology used in HDTVs today and every major manufacturer — Samsung, LG, Panasonic and more — is rolling out HDTVs based on this.

This method has the advantage of allowing for a great 3D experience even when viewers are sitting at an extreme angle from the TV screen.

Of course, the drawback is that active shutter glasses are relatively expensive to make and to be able to view a movie in 3D, each person needs to have a pair.

Manufacturers like Samsung are currently bundling two pairs of glasses with their high-end 3D capable HDTVs, but if you need more, an extra pair could cost you as much as RM599 each.

Challenges

So I know what you’re thinking — since most of the HDTVs on the market are based on the same technology, can the active shutter glasses from one company work with a 3D-capable HDTV from another company?

Well, the answer is theoretically yes but currently a lack of standards means that the answer is no.

There are a couple of ways that manufacturers try to tie you in to their system.

For one, the all-important synchronisation of the shutter glasses with the HDTV’s refresh rate is achieved using either Bluetooth wireless technology or by using an infrared emmitter on the TV and and receiver on the glasses.

Obviously, you can’t buy a pair of shutter glasses which works via Bluetooth with a HDTV that synchronises via infrared and vice versa. Unfortunately, that’s only the half of it — even when both glasses and HDTV use the same sync technology, the left eye/right eye images can be reversed in their order.

For example, while Panasonic and Samsung share the same shutter glasses and sync technology, the left eye/right eye images are synched differently — you’d only be able to see the correct 3D effect if you turned the glasses upside down when viewing 3D content on the other manufacturer’s TV.

Content

The other major problem is that if you buy a 3D-capable HDTV right now, you’ll actually not be able to get much true 3D content on it at the moment.

This of course, is likely to change towards the end of the year when the first 3D Blu-ray discs start to appear — most notably James Cameron’s Avatar.

Right now though, early adopters will have to live with whatever bundled 3D film comes with their TVs or turning on a special mode on the TV which turns 2D content into 3D using an image processing algorithm.

Players

Did we mention that you also need new, 3D-capable Blu-ray players to play future 3D movies?

Yes, well you do — while a small number of current high-end Blu-ray players can theoretically be upgraded to support the just-ratified 3D Blu-ray standard, most Blu-ray players will unfortunately not be able to do so.

This means that if you buy a 3D HDTV, you’re also looking at the extra cost of buying a 3D-capable Blu-ray player to support it.

Sony PlayStation3 owners however, can rejoice — according to Sony, the PS3 only needs a firmware update to support the future 3D Blu-ray standard.

To buy or not to buy

So should you buy a 3D capable HDTV?

Well, being an early adopter is always a risky business, since a lot of things can change (prices, standards) from the time you buy to the time when it all becomes commonplace.

There are a number of good deals in the market right now, with some manufacturers offering the 3D HDTV along with glasses, a 3D-capable Blu-ray player and a movie to go with it.

However, I’d still say to hold on at least till the end of the year, when the standards will finally be settled upon and more content comes along. — TAN KIT HOONG

Related Stories: All you need to know about 3D

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