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3D HDTVs

Something wicked this way comes

Something big has been looming on the home-theater horizon. And now it's moving. Coming closer to your home. To your family. Chances are, you've at least heard the rumblings.

It's 3D home viewing, it's almost here.

Unfortunately, those "rumblings" you've heard have probably been little more than faint rumors. For the release of what is being billed as the most significant innovation -- if not full-out leap -- in home entertainment, a great deal of speculation and confusion has hopped aboard for the ride.

As you might expect, Vann's has entrenched itself in the rumors, press releases, debuts, announcements, and fan-fair, and here we have for you the short-and-sweet of it: 3D technology, how it works, who's offering it, and how you can get it.

Sorcery or stereoscopy?

As funny as it might seem, when it comes to seeing in three dimensions, the magic number is two. Whether it's seeing the world in 3D with your eyes or seeing a 3D image on a screen, both phenomena take advantage of the same fact: you have two eyes.

Humans, and other animals, have two eyes for a reason. If you haven't tried running an obstacle course with one eye closed, we don't suggest you try -- chances are you'd end up with a serious injury or two. You see, each eye by itself sees only a two-dimensional image, that is, an image with only height and width. In other words: no depth perception. Ouch. But pair two eyes up, and voilĂ , you've got 3D vision, a.k.a stereoscopy.

Not to dredge up memories of junior-high science class, but the wizard behind the scenes is something known as parallax. As you've probably noticed, your two eyes are situated slightly apart from one another. Accordingly, whenever you look at something, each eye sees the object or scene from a slightly different angle. (Try to thread a needle while constantly alternating between eyes to experience this effect.) This difference in perspective is parallax.

Now, when the incoming visual information received by each eye is sent to the brain, this uses its special, built-in visual processing abilities to meld the two slightly askew perspectives, making it possible for you to perceive depth and spatiality.

And, just as simply having two eyes -- and two slightly different perspectives -- allows you to see three dimensions in the real world, it also makes it possible to see television in 3D.

After all, that's what we're all really interested in, isn't it . . . 3D TV?

Three roads to 3D

While several approaches to reproducing 3D images have been developed, they all share one thing in common: you guessed it, parallax. Whether it's the old blue-and-red style 3D movies or the latest alternate-frame sequencing technology, they all achieve a 3D effect by taking advantage of the brain's natural image processing. In essence, all these technologies present different images to each eye.

(Oh, and something else that each technology has in common: each requires the use of technology-specific eyewear.)

Road No. 1: The Classic

Yes, while not as prevalent, they're still around: those old, blue-and-red 3D movies. Maybe you've been to a renovated local outdoor theater, or maybe you've caught one of the recent episodes of a major sitcom shown in 3D. In any case, the principle at work is pretty simple.

Each frame of an anaglyphic 3D movie (yes, that's the technical name) is actually composed of two, identical images, one superimposed over the other and situated slightly off-center. The only difference between the two is that the image shifted to the left is red, and the image to the right is blue.

When you push Play and put on the funny cardboard glasses with different color -- red and blue -- lenses, each eye sees only one of the two images, i.e. the image whose color corresponds to the color of that eye's lens. Because each image is slightly offset, and because each eye sees a slightly different angle of the scene, this technology is able to mimic the natural parallax difference between the two eyes.

Ta-da: 3D!

(Unfortunately -- in a nostalgic kind of way -- no new 3D HDTVs will be using this technology.)

Road No. 2: The Split

While the anaglyphic 3D method is based on the color (or wavelength) of light, the polarization 3D method uses the polarity, or orientation of light's waves to achieve parallax. In essence, however, they both achieve a 3D effect using very similar approaches.

As you might be aware, every frame that flashes on your TV's screen is written (or scanned) horizontally into the screen's many rows of pixels. Frames can be scanned onto the screen in one of two ways. While progressive scanning writes all of the rows at once in one big sweep across the screen, interlaced scanning writes all of the odd rows first, and then very quickly fills in the even rows. Thanks to interlaced scanning, polarization 3D is possible. But first, a word on polarization.

While light waves travel in a straight line overall, the ups and downs of the wave itself can vibrate with different orientations -- up, down, left, right, in a spiral . . . any direction perpendicular to the direction of the light wave. The term "polarization" refers to this property of light. While natural light has no polarity, all light waves can be polarized. In other words, all light waves can be made to vibrate in a particular direction as they travel through space, and the orientation of that vibration (polarity) affects how the light is seen. For example, when unpolarized sunlight reflects off a puddle or windshield, it acquires one type of polarization and appears brighter because all of the waves have the same, concentrated, polarity. Polarized sunglasses help reduce this type of glare by filtering out light with common reflective polarities. There are two important observations here: first, that the direction of a light wave's polarity can vary, and second, that polarized light can be filtered. These are the keys to polarization 3D technology.

Three-dimensional video produced using polarization technology has two different polarities -- one for each eye. And that's where interlaced scanning comes into play. Each half of the screen's horizontal scan lines -- odd and even -- has a different polarity. When you put on the special 3D viewing glasses for polarized displays, each lens lets only one of the two polarities through. Accordingly, the right eye sees only the pixel lines with one polarity, and the left eye sees only the pixels with the other polarity.

And, yes, you guessed it: the images shown by each set of pixels are slightly off-set, just as they would be if you were viewing the real scene with your two eyes. Accordingly, each eye has a slightly different perspective, and the brain combines these parallax views into a complete 3D image.

Road No. 3: The Flash

While still looking to parallax for its success, the third 3D home theater technology takes a slightly different approach to stereoscopy than its peers. Anaglyphic and polarization 3D technologies are described as "passive" because each technology's eyewear has no power source or moving parts. Alternate-frame sequencing 3D systems, on the other hand, are known as "active" systems because the required glasses participate, well, actively in bringing you a 3D, stereoscopic experience.

With alternate-frame sequencing (AFS), it's all in the name. This active 3D display technology operates by showing full frames on the screen, alternating showing them to each eye. In this case, one of the keys to understanding the technology will require examining how the video is filmed.

For AFS to work, not only do you need to have two eyes, but so does the camera that's used to film the video. Advanced AFS cameras actually have two lenses, set slightly apart from each other . . . just like human eyes. When a movie or TV show is filmed, two versions are recorded, each from a slightly different angle. Then, when the final movie is assembled, the individual frames of each version are shuffled together, frames from each version alternating one after the other. In order to separate these two versions for each eye, special liquid-crystal (LC) shutter glasses are required.

Unlike the glasses used in other 3D display technologies that have lenses with different color spectrums or polarities, the glasses used in AFS 3D have an active matrix of liquid-crystals, just like an LCD HDTV. Now, instead of working to let light pass through like an LCD's liquid crystals, the LC glasses used in AFS 3D are designed to completely block out light. When a frame from the version of the AFS video intended for the right eye flashes on the TV's screen, the left lens in the shutter glasses blackens, allowing only the right eye to see. Then, when the subsequent left-eye frame flashes on the screen, the right lens blackens, and only the left eye sees the image. This process happens hundreds of times per second, corresponding perfectly with the frames showing on-screen and the parallax with which the AFS camera recorded the video is made available to your eyes.

Finally, if you're wondering how the LC shutter glasses know when to open and close, most alternate-frame sequencing technologies use a wireless signal transmitted from the TV to communicate with the glasses, ensuring unique operation for each program you watch. Currently announced 3D HDTV models offer different transmitter configurations: 3D-ready HDTVs either sport built-in transmitters, or included separate transmitters with purchase; 3D-capable HDTVs require purchase of transmitters.

The Feature Presentation

All this talk of 3D-capable HDTVs begs the question: what are you going to watch once you have your new 3D HDTV on your wall?

Currently, 3D movie and television content is being developed for availability via a variety of sources.

First, several of the manufacturers planning 3D HDTV releases are also planning to introduce 3D-capable Blu-ray Disc players. Not only would these newest-generation players still be capable of playing DVD and Blu-ray video in 2D, but they will also be compatible with the new 3D video formats. Note: 3D content will only be available when a 3D Blu-ray movie is played in a 3D-capable Blu-ray player connected to a 3D HDTV.

Second, several new 3D-only television networks are purportedly in the making, but there are currently no concrete facts.

Finally, manufacturers are also preparing 3D video games for use with new 3D displays.

The technology is here, manufacturers are building 3D televisions and LC glasses, and studios are beginning to record 3D content, but the 3D home entertainment revolution is still just beginning to move forward. Accordingly, as of yet there are no cold, hard facts on the matter. However, in the side panel you'll find what we know right now. And you can be sure that we'll update this run-down as often as anything definitive emerges.

A Final Note

Don't worry: new 3D HDTVs are still fully compatible with standard-definition and non-3D HD viewing, so you can still watch all your favorite DVDs and 2D Blu-ray movies.

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