I know what you’re thinking, “I just bought my HDTV, what’s all this 3D business?” 3D is expected to be the next monumental breakthrough in the history of television. In this Tech Tip, I’ll cover the basics of 3D TV, including some of the different technologies and how they work.

How it works: three dimensional television (3D TV) uses a method known as stereoscopy to display two different images to your eyes so that they appear as one image. As your brain interprets what your eyes are seeing, it combines the two images while your eyes are still focusing on the source of the images behind them. This creates an illusion of depth to the viewer. The phrase, “There’s no such thing as a free lunch” holds true for fooling your brain, too. Long viewing sessions of stereoscopic images or video strains your eyes and can result in headaches. Worse yet, a small minority of people can’t see stereoscopic images or video at all due to any number of medical conditions that prevent their brains from being fooled.

Most of us are probably familiar with our first type of stereoscopy, the anaglyph lenses. Anaglyph lenses use contrasting colors (usually red and blue) to achieve the effect of stereoscopy by blocking the images colored to match the lenses so that each eye can only see one of set of images. With red and blue anaglyph glasses, your left eye sees only the blue light that doesn’t reflect off the red lens in front of you, and your right eye only sees the red light coming through the blue lens. The obvious drawback to the viewing experience provided by anaglyph lenses is that the image is tinted with both colors of the anaglyph lenses.

The second type of lenses used are much more modern and have even enjoyed moderate success in movie theaters: polarized lenses. Polarized lenses achieve the same effect as anaglyph glasses by restricting the images each eye gets to see using polarized filters. Half the images are allowed to get to one eye, half to the other, and they meet in 3D glory somewhere in the middle.

Our next type of 3D TV is the active method, as opposed to the passive method employed by anaglyph polarized lenses. Active lenses are more expensive than their passive cousins and get their name from the fact that they actively shut on and off at extremely high rates of speed to create the stereoscopic depth effect. However, they cannot work on their own and require a display capable of syncing with the glasses, and since they’re sitting on your face, they have to be wireless, which is accomplished via infrared technology. With active glasses synced to a 3D-ready television, your eyes are shown only the images they are supposed to see, using a method known as alternate-frame sequencing, to achieve a stereoscopic effect.

Only recently have LCD TVs and plasma displays been capable of flickering enough images at you per second to make this work. To be a 3D-ready TV, a display must be capable of display at least 120 frames per second (120 Hz) and needs a set-top-box that syncs with the glasses. The first requirement is satisfied rather easily these days, you can find 240 Hz displays in the wild already. The second requirement is what’s held 3D TV back so far; not many people are running out to purchase a set-top-box and a bunch of pairs of special glasses. Add the fact that there hasn’t been an industry standard, so manufacturers have their own stereoscopy methods that often are incompatible with each other.

The last kind of stereoscopy, and really, it’s the best kind, is known as autostereoscopy or Auto 3D. There are two major methods of accomplishing stereoscopy without glasses. The first is the parallax barrier. The parallax barrier is basically a filter that lays over the screen that tricks your eyes into focusing in front of the actual screen to create the same illusion of depth. You can see parallax barriers at work in Nintendo’s latest portable console, the 3DS.

The other autostereoscopic technology is the lenticular lens method that works by laying tiny magnifying lenses over a particular set of images. Lenticular printing has been around for quite awhile and is the method using to make printed images appear to change as you turn them back and forth.

Unfortunately, technological limitations prevent both of these methods from being implemented in large screens at this time.

A number of things need to go right for 3D TV to take off, but chief among them is the fact that the glasses have to go. Nobody wants to buy a set of glasses just in case their friends come over. The next obstacle is standardization: just like we saw consumers holding off on HD-DVD vs. Blu-ray until there was only one, they will do the same for 3D TV. It’s also worth noting that more 3D content has to be created for people to watch it, so the chicken and egg causality dilemma stands in the way. Content producers won’t be rushing to create 3D content if there’s only a small install base of 3D-capable living rooms. One thing is for sure, television manufacturers are very inclined to get you to buy a new TV and they are focused on enticing you by wowing your pants off with fantastic 3D technology. I’m prepared to allow them, but without glasses!