Volumetric display based on optical scanning of an inclined image plane by an image rotator and imaging by a dihedral corner reflector array

We propose to use a rotational optical scanning method for a volumetric three-dimensional (3D) display based on optical scanning of an inclined image plane. The image plane was moved by an image rotator and formed by a dihedral corner reflector array, which is a distortion free imaging element forming a real image at a plane-symmetrical position. A stack of the moved and formed image planes of a two-dimensional (2D) display created displayable space of a 3D image, which satisfies all the criteria of stereoscopic vision and can be seen by the naked eyes. The image rotator used in this study was constructed of prism sheets and planar mirrors. The image plane was moved rotationally by rotating the proposed image rotator on an axis parallel to the mirror plane. Enlargement of the displayable space is achieved by just extending the distance between the 2D display and the mirror, so that the proposed scanning method is effective to display a large 3D image for our volumetric display system. We made a prototype display and observed a moved image plane to measure the displayable space of the 3D image. The size of the displayable space was 1200 [cm3] that is approximately six times as large as our previous display using a translational optical scanning method.