New screen allows you to watch 3D films without glasses

Movie-goers, rejoice! MIT scientists have developed a novel screen technology that may allow you to watch 3D movies in theatres without wearing those annoying goofy glasses.
Dubbed "Cinema 3D," the prototype uses a special array of lenses and mirrors to enable viewers to watch 3D films from any seat in a theatre.
"Existing approaches to glasses-free 3D require screens whose resolution requirements are so enormous that they are completely impractical," said Wojciech Matusik professor at Massachusetts Institute of Technology (MIT).
"This is the first technical approach that allows for glasses-free 3D on a large scale," said Matusik.
While the researchers caution that the system is not currently market-ready, they are optimistic that future versions could push the technology to a place where theatres would be able to offer glasses-free alternatives for 3D movies.

Glasses-free 3D already exists, but not in a way that scales to movie theatres. 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.

However, because parallax barriers have to be at a consistent distance from the viewer, this approach is not practical for larger spaces like theatres that have viewers at different angles and distances.
Other methods 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 theatres 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 theatre.
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 theatre by a series of mirrors and lenses within Cinema 3D's special optics system.

"With a 3D TV, you have to account for people moving around to watch from different angles, which means that you have to divide up a limited number of pixels to be projected so that the viewer sees the image from wherever they are," said Gordon Wetzstein, assistant professor of electrical engineering at Stanford University, who was not involved in the research.
"The authors (of Cinema 3D) cleverly exploited the fact that theatres have a unique set-up in which every person sits in a more or less fixed position the whole time," said Wetzstein.
The team demonstrated that their approach allows viewers from different parts of an auditorium to see images of consistently high resolution.