True Holographic Movie Within Reach

It’s been 43 years since audiences heard those famous words “Help me, Obi-Wan Kenobi. You’re my only hope” from a hologram projection in the first Star Wars film, yet true holographic movies, like the one R2-D2 projected of Princess Leia, are still the stuff of science fiction. “Holographic” performances from Tupac and Michael Jackson weren’t exactly holograms, but rather a more advanced version of an old trick called a Pepper’s ghost.

The most exposure most people get to holographics is with “surface relief holograms,” which can be found in twinkly wrapping paper or security stamps on credit cards and passports.

However, a team from the Tokyo University of Agriculture and Technology has recently demonstrated a true holographic movie inspired by the sequential playback of the first cinematic projectors of the 19th century.

Rather than a reel of film, the proof of concept uses metasurfaces, which are thin-film materials just nanometers thick whose microstructures are crafted to manipulate light. Metasurfaces involve tiny repeating patterns at a scale smaller than the wavelength. Rather than its chemical composition, the shape of a metasurface is what allows it to alter the path of light.

To create the film, the researchers printed an array of 48 rectangular frames of a metasurface made primarily of gold, which diffracts laser light in such a way as to produce a true holographic 3D image in the air, viewable from most angles in the room.

Each of the metasurface frames is slightly different, as with frames on a reel of celluloid film. The sequential images, played at a rate of 30 frames per second, show Earth rotating.

“We’re using a helium-neon laser as the light source, which produces a reddish hologram image,” said Kentaro Iwami, one of the engineers who developed the system. “So the aim is to develop this to produce full color eventually. And we want it to be viewable from any angle: a ‘whole hemisphere’ 3D projection.”

In its current form, the process is quite time consuming. It took an electron-beam lithography printer six and a half hours to draw the 48 frames, an extremely short film that was run on a loop. According to the researchers, a six-minute holographic movie would take more than 800 hours to print.

The research was published in Optics Express (www.doi.org/10.1364/OE.399369).