English: Just took a cool tour and theater demo of Dolby 7.1 and 3D Digital Cinema at Dolby research. This rack in the projector room is full of various generations of video codecs.

I had wondered how these passive 3D glasses work when I first tried them at PIXAR. From rotating them in front of my polarizing sunglasses, I could tell they are not polarized, and the color space of each lens seemed similar (no red-blue or other obvious color filtering).

Got the answer today: these are complex multilayer lenses made by JDSU with interleaved filters. The left and right eyes receive the RGB color space shifted 20 nanometers. So, for example, each eye can see red, but 20nm offset in color.

The projector has a spinning color filter wheel as they call it. It takes the full-color frames intended for each eye and applies the relative 20nm spectrum shift (probably a non-linear filter). The wheel rotates in sync with the projector’s frame rate.