Interesting news from MIT News:
Glasses-free 3-D already exists, but not in a way that scales to movie theaters. Traditional methods for TV sets use a series of slits in front of the screen (a “parallax barrier”) that allows each eye to see a different set of pixels, creating a simulated sense of depth.
But because parallax barriers have to be at a consistent distance from the viewer, this approach isn’t practical for larger spaces like theaters that have viewers at different angles and distances.
Other methods, including one from the MIT Media Lab, involve developing completely new physical projectors that cover the entire angular range of the audience. However, this often comes at a cost of lower image-resolution.
The key insight with Cinema 3D is that people in movie theaters move their heads only over a very small range of angles, limited by the width of their seat. Thus, it is enough to display images to a narrow range of angles and replicate that to all seats in the theater.
What Cinema 3D does, then, is encode multiple parallax barriers in one display, such that each viewer sees a parallax barrier tailored to their position. That range of views is then replicated across the theater by a series of mirrors and lenses within Cinema 3D’s special optics system.