Display allows for glasses-free 3D

Dubbed "Cinema 3D," the prototype uses a special array of lenses and mirrors to enable viewers to watch a 3D movie from any seat in a theater.

"Existing approaches to glasses-free 3D require screens whose resolution requirements are so enormous that they are completely impractical," says MIT professor Wojciech Matusik, one of the co-authors on a related paper. "This is the first technical approach that allows for glasses-free 3D on a large scale."

While the researchers caution that the system isn't currently market-ready, they are optimistic that future versions could push the technology to a place where theaters would be able to offer glasses-free alternatives for 3D movies.

Among the paper's co-authors are MIT research technician Mike Foshey; former CSAIL postdoc Piotr Didyk; and two Weizmann researchers that include professor Anat Levin and PhD student Netalee Efrat, who was first author on the paper. Efrat will present the paper at this week's SIGGRAPH computer-graphics conference in Anaheim, California.

Glasses-free 3D 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 allow 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 reduced 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 a narrow range of angles and replicate it 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.

The team demonstrated that their approach allows viewers from different parts of an auditorium to see images of consistently high resolution.

Cinema 3D isn't particularly practical at the moment: the team's prototype requires 50 sets of mirrors and lenses, and yet is just barely larger than a pad of paper. Matusik says that the team hopes to build a larger version of the display and to further refine the optics to continue to improve the image resolution.