All About Eyes

Although the 1950s are most often considered the 3-D movie decade, the first feature length 3-D film, “The Power of Love,” was made in 1922. Since that time the use of 3-D technology in theaters has drifted in and out of mainstream popularity, until recently.  But, how do these 3D movies and glasses actually work?

In a movie theater, the reason why you wear 3D glasses is to feed different images into your eyes just like a View-Master does.

The screen actually displays two images, and the glasses cause one of the images to enter one eye and the other to enter the other eye. There are two common systems for doing this:

Red/Blue
Although the red/green or red/blue system is now mainly used for television 3D effects, and was used in many older 3-D movies. In this system, two images are displayed on the screen, one in red and the other in blue (or green). The filters on the glasses allow only one image to enter each eye, and your brain does the rest. You cannot really have a color movie when you are using color to provide the separation, so the image quality is not nearly as good as with the polarized system.

The red and blue lenses filter the two projected images allowing only one image to enter each eye.

Polarization
At Disney World, Universal Studios and other 3-D venues, the preferred method uses polarized lenses because they allow color viewing. Two synchronized projectors project two respective views onto the screen, each with a different polarization. The glasses allow only one of the images into each eye because they contain lenses with different polarization.

The polarized glasses allow only one of the images into each eye because each lens has a different polarization.

3D TVs

Simply, for example, in one system, a 3D TV screen displays the two images alternating one right after the other. Special LCD glasses block the view of one eye and then the other in rapid succession. The secret to 3-D television and movies is that by showing each eye the same image in two different locations, you can trick you brain into thinking the flat image you’re viewing has depth.

While your eyes may converge upon two images that seem to be one object right in front of you, they’re actually focusing on a screen that’s further away. This is why you get eye strain if you try to watch too many 3-D movies in one sitting.

Soo how do you show two different images that appear to only be one? It’s all in the lenses.

But, 3D Glasses Are Dirtier Than You Think

“Good Housekeeping” magazine recently tested 3-D glasses at movie theatres in New York, New Jersey and Connecticut. The glasses they tested were both wrapped in plastic and unwrapped, and the research team found that NONE of them were sterile. A host of bacteria were found on the 3-D glasses, including bacteria that cause Pink Eye.

Dr. William Schaffner is a professor of Preventive Medicine at Vanderbilt University School of Medicine. He says, don’t make yourself crazy over it – there are no more bacteria on the glasses than on the armrest, handrails and bathroom door handles at the movie theater. The difference is, you’re putting the glasses on your face. So make sure kids don’t put them in their mouth.

But how do 3D Tvs without glasses work?

A parallax barrier is one of the more popular ways for swinging 3D without glasses—you see it in Sharp TVs for instance. It actually works a lot like polarized glasses, it just moves where the obstruction magic happens to the front of the TV. Instead of having glasses filter the image for each eye, the screen’s parallax barrier—think of it is a very finely grated fence with precisely angled holes—directs different light into each eye, and your brain turns the mixed signals into a 3D image.

The bad part? With a normal parallax barrier, the screen is permanently in 3D mode and you don’t have exactly have a wide viewing angle. Sharp’s trick for 3D in LCD displays is fancier—there’s a second LCD that creates the parallax barrier with a polarized grid of lines, which is nice because you can turn it off and go back to regular 3D viewing.

Japanese researchers’ new plasma-laser hologrammy device actually creates a surface in mid-air to project an image onto, the floating holograms look 3Dish, though they’re actually planar (2D) images. Yep, it’s expensive.

According to a figure from Britain’s Eyecare Trust, they found that as much as 12% of the population suffer from a visual impairment that prevents them seeing 3D images.  If you’re one, see your eye doctor because they may be able to find the problem and fix it.

Special thanks to Nathaniel and Gordy Graham for the references