There is little doubt in anyone’s mind that 3D is the future. There are visionaries that see a future where a 3D image will be projected straight into your living room. However, that day is not here as watching 3D TV will require glasses for the foreseeable future.

As with all technology, change comes in steps and the 3D TV technology we have today which requires glasses is the most advanced form of it. 3D TVs are capable of outputting 200 Hz or more in order to display stereo displays. This is a huge leap from the standard 60 Hz display, refreshing images at a much faster rate.

These 3D TVs also sync with active liquid crystal shutter glasses which refresh at a high rate that is unnoticeable to the human eye. This tech is the best quality there is on the market for viewing as it eliminates ghosting caused by other forms of 3D.

While TV manufacturers are pushing this technology currently, many are also working on glasses-free 3D TVs or autostereoscopic sets. Glasses-free 3D TVs are a big challenge currently as many of the applications are not all that practical.

Lets take a look at the two most popular autostereoscopic (glasses-free 3D) technologies today:

Lens Cover (Parallax barrier, Lenticular lens)

This is your most basic type of “glasses-free” 3D technology. Its actually using a simple lenticular-based (hologram) trick that has existed for hundreds of years. Both parallax barrier and lenticular lens use a similar type of technology where a lens cover is placed over the LCD TV screen. The lens cover has tiny slits cut into it to “point” a pixel towards a certain direction.

The main difference between the two technologies is that parallax barrier makes use of a liquid crystal screen cover and lenticular primarily uses a cylinder shaped lens cover. Parallax barrier screen cover is slightly better as 2D and 3D mode can easily be toggled using current, which can make the liquid crystal screen cover passive.

Both technologies are easy to implement but yield the worst type of 3D quality. Since each of the stereo images is pointing to a specific eye, the viewer must sit at a specific “sweet spot.” Companies like Toshiba have tried to alleviate this issue by creating nine sweet spots using mutli-parallax barrier technology. However, the net result is just as unimpressive as it requires the viewer to remain completely motionless at that sweet spot.

Any sort of movement will cause immediate blurriness of the 3D image, as you are “focusing” the image with your head position and not with the TV. One major problem with this is that by human nature people will shift in their seats and crane their necks. Ultimately prolonged viewing in this manner will undoubtedly cause severe eye strain.

Camera Eye Tracking 3D Projection

This is probably by far the most promising type of glasses-free 3D technology. However, its all very experimental as it relies on tiny cameras tracking your eye location at all times. The 3D TV would calculate your eye’s position and project each of the 3D stereo images to that angle.

Manufacturers are demoing this technology at trade shows like CeBIT in rudimentary form. This technology allows viewers to move around the living room while maintaining 3D depth consistently. However, currently this technology can only work with a single viewer as the camera can only track one set of eyes.

This issue can be resolved with multiple cameras built into the display, or better technology capable of tracking more than one set of eyes. Although to be practical the TV would need to be able to track five or more sets of eyes.

There are other factors such as camera technology, as it needs to be able to track your eyes in various lighting conditions as well. I would say that practical application of this technology is at least a decade away.

Conclusion

Parallax barrier technology, which is used in Nintendo’s 3DS and Toshiba’s glasses-free 3D TVs are not practical for the living room as it requires users to remain “motionless” at uncompromising angles. Manufacturers can create thousands of “sweet spots” and the blurring will still happen at the tilt of your head. Also, creating more than ten sweet spots is not practical as it requires “cutting” more pixel angles into the crystal cover causing a reduction in resolution.

Camera eye tracking technology very well may be the key to motion autostereoscopic displays. However, the technology is severely limited currently and will probably be practical in 10 to 15 years.

It appears that consumers griping about wearing active shutter 3D glasses may have to wait a very long time for a viable alternative. As it stands, 3D technology that requires shutter glasses will probably remain as the best option on the market delivering the best quality visuals without ghosting, blurring and eye strain.

by Mike Ferro

original post: http://tech.blorge.com/Structure:%20/2010/10/07/tech-overview-why-glasses-free-3d-tvs-are-not-practical/