MIT Media Lab tackles glasses-free 3-D

The Media Lab at Massachusetts Institute of Technology has developed a new glasses-free “autostereoscopic” technology called HR3D (High-Rank 3D) that could double the battery life of portable viewing devices without compromising screen brightness or resolution.

The MIT system uses two layers of liquid-crystal displays. Instead of displaying vertical bands or pinholes, as a multiperspective, parallax-barrier system would, the top LCD displays a pattern customized to the image beneath it.

Doug Lanman, a post-doctoral student in Associate Professor Ramesh Raskar’s Camera Culture Group at the Media Lab, said that devices like Nintendo’s 3DS rely on a century-old technology known as a parallax barrier. Like most 3-D technologies, this one requires two versions of the same image — one tailored to the left eye and one to the right. The two images are sliced into vertical segments and interleaved on a single surface.

By itself, the composite image looks like an incoherent mess. But if one places a screen with vertical slits in it — known as the parallax barrier — just in front of the image and stands the right distance away, a 3-D image pops out. The opaque sections of the screen shield the parts of the image intended for the right eye from the left eye, and vice versa, but the slits allow each eye to see the segments intended for it.

When they began the project, the research team had no idea what the customized pattern would look like. But they found that the ideal pattern ends up looking a lot like the source image. Instead of consisting of a few large, vertical slits, the parallax barrier consists of thousands of tiny slits, whose orientations follow the contours of the objects in the image.

They decided to use a barrier that changes with the image — a more versatile method. At its current stage, this technique requires a lot of computational power to spit out the perfect barrier for the image. With simplification, the research could lead to improved glasses-free devices.

Nintendo’s 3DS portable gaming system, the first commercial device with a glasses-free 3-D screen, has been available in the United States for barely a month, and it’s already sold more than a million units. Its three-hour battery life, however, is less than half that of its predecessor, the 2-D DS device.

The MIT researchers said they could double the battery life of devices like the 3DS without compromising screen brightness or resolution. Among other advantages, the technique could also expand the viewing angle of a 3-D screen, making it practical for larger devices with multiple users, and it would maintain the 3D effect even when the screen is rotated — something that happens routinely with handheld devices.

“The great thing about Ramesh’s group is that they think of things that no one else has thought of and then demonstrate that they can actually be done,” said Neil Dodgson, professor of graphics and imaging at the University of Cambridge in England, who was one of the reviewers of the paper when it was accepted last year to the SIGGRAPH Asia graphics conference. “It’s quite a clever idea they’ve got here.”

Dodgson points out, however, that HR3D requires a lot of computing power. “If you’re saving battery power because you’ve got this extra brightness, but you’re actually using all that battery power to do the computation, then you’re not saving anything,” he noted.

While Lanman acknowledges that the algorithm for calculating the barrier pattern that he and his colleagues described in the SIGGRAPH Asia paper is complex, he believes that it can be refined so that “it requires far less computation.” He also points out that special-purpose chips designed specifically to run a refined version of the algorithm would consume much less power than a general-purpose processor performing the same computations.