Keio University

Even if you have a dashboard display showing what's behind your car when you back up, it's hard to be 100 percent sure you won't hit something. Or someone. That's why researchers at Japan's Keio University are working on a system that makes the back seat invisible, so to speak.

From the driver's perspective, the back of a car, in this case a Prius, is transparent, thus eliminating blind spots that could conceal hazards. The system is called the "see-through Prius" and it's being showcased this month at the 2012 Digital Content Expo in Tokyo.

The system is a variant on optical-camouflage technology developed by Susumu Tachi, Masahiko Inami and colleagues about a decade ago.

Tachi's invisibility cloak captures footage from behind an object, and then projects the background onto the garment. The illusion of invisibility, as seen in the video below from 2006, is quite astounding.

The technology uses retroreflective materials, which reflect light with little of that light scattering back the way it came. The cloak is embedded with thousands of highly reflective beads to shine light in specific directions, creating the illusion of partial invisibility.

Tachi had suggested using the know-how for car safety, and Inami recently put the idea into practice. It's like augmented reality in that it's layering information on a scene.

There's little info so far about what kind of gear the Prius was loaded with, and whether the seats were also covered with reflective beads, but it seems to involve a display attached to the driver's headrest.

"The driver will feel like he's driving a glass car," Inami told a Japanese government publication. "Sir Arthur C. Clarke said, 'Any sufficiently advanced technology is indistinguishable from magic.' I want to develop technology like magic that general people can use easily in the future."