Aerial 3D LED display by use of retroreflective sheeting

We propose a new optical configuration to form aerial 3D LEDs by use of retroreflective sheeting. The proposed configuration is composed of LEDs, a half mirror, and retroreflective sheeting. A half of the LED lights are reflected by the half mirror and impinge on the retroreflective sheeting. The retroreflective sheeting reflects the lights back to their sources. On the way to the sources, a half of the lights transmit through the half mirror and form the real images of LEDs. Although less than 25 % of the output lights are contributed to the aerial image, recent LED panels have enough luminance to enjoy the aerial image with a quarter of the luminance. We have made a prototype of the proposed aerial LED display. An aerial image of the LED panel has been successfully formed in free space. Its viewing angle was significantly improved compared to the aerial display by use of crossed mirrors, which limit the viewing angle by aperture size and height of mirror walls. The viewing angle in the proposed configuration is mainly limited by the size of the retroreflective sheeting. Furthermore, by using LEDs in different depths, we realized an aerial 3D display in free space.