You may recall in the first Star Wars movie, R2D2 displays a video message floating in mid-air in which the image of Princess Leia pleads for help from Obi-Wan Kenobi. More recently, in Star Wars: The Force Awakens (Spoilers), the same droid projects a map into the air showing the location of Luke Skywalker. Science fiction? Maybe, but by 2020 Mitsubishi Electric plans to commercialize a system that can display relatively large images (measuring approximately 56 inches diagonally) as if they were floating in mid- air.
Help us Mitsubishi, we really want to see free-floating displays
To make images appear to float in front of the viewer, Mitsubishi relies on two optical devices: a beam splitter, which divides incoming light into reflected light and transmitted light; and a retro-reflective sheet, which reflects incoming light back in the direction from which it was emitted (see illustration below). The aerial image, which can be a still image or video, is first projected on a screen that is perpendicular to the viewer and out of the viewer’s sight. Placed at a diagonal to the screen is the beam splitter, which as the name suggests creates two duplicate images. These are reflected off of the retro-reflective sheet and converge in the air in front of the viewer, causing the viewer to perceive a single image that appears to be floating in front of him or her.
Mitsubishi has created floating displays using an elaborate series of reflections
Among the hidden obstacles in creating a so-called floating image is that people find it hard to focus on such displays when they have no point of reference—that is, when there's no way of telling where the image is. To resolve this issue, Mitsubishi came up with a simple idea of displaying "guide images" projected onto walls or other fixed surfaces on either side of the floating image (see the illustration at the top of the page) to give the viewer a context point to help them focus on the image in front of them. Mitsubishi hopes to create a final product that will link the three images in a single display unit that can be used to project entertainment and/or information content. The entire display area, including the two guide images, measures 90 inches diagonally; the floating display measures approximately 56 inches diagonally.
Another key ingredient in making aerial image displays possible is an optical simulation program developed by Mitsubishi that helps them calculate the exact positions of the screen, the beam splitter and the retro-reflective sheet necessary to generate a floating image approximately one meter from the optical arrangement.
Mitsubishi Electric began joint research on aerial displays in April 2015 with Hirotsugu Yamamoto, an Associate Professor at the Graduate School of Engineering at Utsunomiya University. The company hopes to commercialize its aerial display technology by 2020. Applications that will be explored include: signage—images can be installed over roads without obstructing walking or traffic; aerial advertising --displaying large images in the air above a stadium; or communications-- displaying life-sized images of people (for example, missing or lost children at a shopping mall).