The National Institute of Information and Communications Technology (NICT) and Kobe University have jointly developed a thin-panel type device, which forms 3D images in the air. "This device renders transparent, reflected images. Unlike holography, the device needs no special optical system other than itself and features color image production," said a spokesperson. Just by setting a display (or a subject to be shown) under a glass table and laying this device over the table, a "3D display" can be created.
At the demonstration, this device was set above a small ball (Japanese craft ball) measuring about 2 cm in diameter. When looked sideways from above, the ball, which was supposed to be under the device, looked as if it was floating in the air above the device. No evident change was seen in the 3D image of the ball even when we moderately changed the angle and distance of our viewing position. "We can even realize a 3D image of a human if we only substantially enlarge the device size. However, the top and bottom, concavity and convexity of the 3D image will be displayed in reverse," explained an NICT spokesperson. In other words, a human face will be shown in a form like a mask viewed from its rear side.
This device is made by forming a 100 μm-thick Ni layer on a glass plate and punching a lot of 100 μm square holes in it. Light coming from an object beyond the device is reflected twice by inner surfaces of the holes, which are made like mirror and aligned at 90 degrees against each other, and then forms an image in the air on the opposite side (viewed from the object positon) of the device. This situation can be described as a matrix of many tiny dressing tables, whose two mirrors opened at 90 degrees are set to face square to each other. "Mechanism of this image production is the same as that of mirror reflection. It can be explained with geometric optics and requires no expertise in wave engineering like holography," said the NICT spokesperson.