When 3D movies were first introduced in the '50s, projection methods were crude in comparison to the polished experience we enjoy on the silver-screens of today. Though 3D resurfaced in the '80s and '90s, not much about the technology had changed. Everyone remembers the 3D glasses of that era—flimsy cardboard, red-blue lenses—not exactly cutting edge gadgetry.
Fast Forward to 2011:
Thanks to new techniques that make use of high-definition digital projectors and much improved polarized lenses, the 3D illusion has been refined to a point where it is no longer the gimmicky experience we remember from earlier incarnations.
Anyone that’s seen the lush, immersive jungles in Avatar, or witnessed the thrilling action sequences in How to Train Your Dragon knows that 3D is probably here to stay.
Adapting the Technology:
With theater technology vastly improved, the main unanswered question for most manufacturers is how to best bring the cinema experience to your home theater.
To produce the illusion of 3D, a slightly different image must be presented to each eye. In perceptual science, this is called binocular disparity, which refers to the fact that each of our eyes sees the environment around us from a slightly different angle (giving us the perception of depth). In the cinema, our mind is tricked into a false illusion of depth with stereoscopic projectors and glasses that mimic the human visual system.
3D in the Cinema:
At the movie theater, stereoscopic systems alternately project a different image for the right and left eye in rapid succession. Film is shot at 24 frames per second, so the theater’s projector is actually displaying 48 different frames for every second of film.
- The sequence looks like this:
Frame-1 (Right), Frame-1 (Left), F-2 (Right), F-2 (Left)……F-24 (Right), F-24 (Left)
This happens so quickly that without a filtering system, our eye would perceive the two images as being overlaid on top of one another (take your 3D glasses off in the cinema to see this effect).
In order to complete the 3D illusion, projectors use a polarization filter so that all frames intended for the right eye are polarized in one direction, and all frames intended for the left are polarized opposite. Glasses are manufactured so that each lens will only allow frames with the correct polarization to pass through, thereby blocking the image intended for the opposite eye. Voila—3D!
Bringing it Home:
As you might have guessed, the methods previously described don’t work for television screens. Because a television cannot produce the two separately polarized image channels necessary for cinema style 3D, display manufacturers were forced to develop the active shutter system in order to bring 3D to living rooms.
- Active Shutter System:
The active shutter system shares the same delivery method as the cinema (Right-frame Left-frame in rapid succession), but ditches polarization for filtering images to the correct eye. Instead, shutter glasses synchronize with the television’s refresh rate, alternately blacking out either the left or right lens.
This happens quickly enough that the eye should not detect any visible flicker, and prevents one eye from seeing images meant for the other. Active shutter displays were the first to hit the market in late 2009, and have mostly dominated 3DTV sales to this point. - Drawbacks of Active 3D:
There are numerous downsides to the active shutter system for 3D televisions. Shutter glasses are expensive, most costing upwards of $100, and are more prone to failure than their polarized counterparts.
Shutter glasses are also much bulkier than theater glasses, and many owners report visible flicker, eye strain, and discomfort when worn for extended periods of time.
Passive 3D in the Home Theater?
One of this year’s most buzzed about topics following the CES 2011 trade show is the announcement that Sony and LG will be throwing their weight behind consumer oriented passive 3D systems, similar to what is found in movie theaters.
The new displays use polarized glasses, almost exactly like the ones you wear in movie theaters. Unlike shutter glasses, these require no batteries and have no electric parts prone to failure. More important is the fact that they’re lightweight and cost less than $2.00 a pair.
Check out this overview of 3D glasses techchnology.- The Downside of Passive 3D: With the current generation of Passive 3D televisions, the most notable drawback is that in order to produce a polarized image, each eye only receives half of the television’s full resolution. This means that for 1080p programming (like a Blu-ray disc), each eye only sees 540 lines of resolution.
- Format War or Peaceful Coexistence? The next year promises to be an interesting one in the world of 3DTVs. For now, active shutter displays dominate the market, but we expect passive technology to catch on very quickly. Resolution losses aren't as apparent as one might predict, and the ability to use inexpensive polarized glasses will be a boon to most consumers.
