5-inch high-resolution aerial display by use of retro-reflector and a Fresnel lens

Aerial displays form real images in mid-air and realize a non-contact user-interface. However, the aerial images are significantly blurred compared to the light source images due to ray shift, diffraction spread, and scattered light by the optical elements. Lens-enhanced aerial imaging by retro-reflection (LeAIRR) optical system reduces the ray shift, diffraction spread, and scattered light and forms high-resolution aerial images. This system consists of a light source display, a beam splitter, a convex lens, and a retro-reflector. The size of the aerial display based on LeAIRR optical system depends on the size of the lens. However, large-size convex lenses made of glass are difficult to manufacture. In this study, we propose a 5-inch size high-resolution LeAIRR optical system that utilizes a Fresnel lens (Fresnel LeAIRR) that magnifies the light source image on the retro-reflector. The Fresnel lens is positioned so that the aerial image and the retroreflector are conjugated to reduce the effects of diffraction and the ray shift effects. The modulation transfer function (MTF) of the proposed optical system is superior to the conventional AIRR optical system.