A New Spin on 3D

Last Updated (Friday, 08 October 2010 12:22) Written by Raymond Nakamura

I went to see one of those new 3D movies. I'd been to others in the past, wearing special glasses with polarized lenses so slightly different images went into each eye. With two pairs of these glasses, if you overlapped the lenses and then rotated them, you could get them to go from clear to gray to black depending on how much light got blocked out. I thought I'd show this to my daughter, but it didn't work with the new glasses. What was going on?

Seeing It Old School

In the old days, they had the funny looking red and blue lenses, but you don't get proper colour images. To see 3D movies in colour, they went to glasses with polarized lenses. Polarization has to do with the orientation of light waves. Linear polarization involves light waves being oriented in a one plane or other. Each lens was polarized for light in a plane perpendicular to the other. We used to have a strange 3D light show at Science World for which volunteers were always polishing the glasses. They don't block as much light as sunglasses.

Colour My World

The latest 3D projection systems in the theatres are digital. One system uses a filtration wheel in front of the projector to separate the image into red, green and blue. It spins around three times a frame so you can't tell. Each lens allows slightly different frequencies to get through.

Do the Twist

The theatre I was in used a system with a circular polarization filter in front of the projector, which gives the light a twist. Light goes in a corkscrew to the right and to the left. This filter switches direction back and forth so quickly you can't tell. You only need one projector instead of two. Apparently this allows you to move your head without losing the effect. This might also explain why I didn't see much change in the light when I rotated overlapping lenses.

High Noon in 3D

The filtration wheel approach allows theatres to use their existing screens. The glasses are fancier and reusable. For the circular polarization system you need a custom screen that will preserve the polarization when it reflects it. The glasses are recyclable. It looks like another one of these technological showdowns, but I don't know if it's worth it.

What do you think?