Floating volumetric display using an imaging element that consists of a 90° prism sheet and a linear Fresnel lens

Abstract

We propose a floating volumetric display system using a novel imaging element whose aperture is large and can be made easily at low cost. Diffuse rays in a horizontal direction for an observer are formed by a 90o prism sheet, which has a shape of an array of 90o V-grooves, as a result of twice total internal reflection. On the other hand, the diffuse rays in a longitudinal direction for the observer are formed by a linear Fresnel lens. A formed image by the proposed imaging element does not distort in the horizontal direction because the rays in the horizontal direction converge by retroreflection. The proposed imaging element can be produced easier than a conventional distortion-free imaging element and display a larger floating image. A floating three-dimensional image was displayed by a volumetric display system based on optical scanning of an inclined image plane. A position of a two-dimensional real image formed by the proposed imaging element was moved by an optical scanner at a faster rate than the duration time of persistence of vision. A stack of moved images created the floating three-dimensional volume image.