Reducing thickness of long-distance aerial display system in AIRR using Fresnel lens

Aerial displays for providing road information require long-distance image formation and a compact installation space. This paper proposes a compact optical system for forming long-distance floating images by introducing a Fresnel lens in an aerial imaging by retro-reflection (AIRR) optical system. In the conventional AIRR optics, since the aerial image position is the plane-symmetrical position of the light source with respect to the beam splitter, the installation space for forming a long-distance aerial image becomes huge. Our proposed method uses the virtual image formed by a Fresnel lens as the light source in an AIRR optical system. This leads to a much longer distance from the beam splitter to the aerial image than the distance from the beam splitter to the light source. We developed a prototype long-distance floating aerial display system using a large-scale Fresnel lens. As a result, the distance from the LED panel to the beam splitter was halved. Furthermore, we used two beam splitters to form two aerial images by using a single LED panel. Long-distance floating images could be formed 3.4 m and 4.6 m away from the beam splitters and could be seen with the naked eye.