Expansion of a vertical effective viewing zone for an optical 360° holographic display

Cylindrical holography, as a promising 360° display technology, has already attracted a lot of attention. In a previous study, an optical 360° cylindrical holography has been achieved in the visible spectrum using a planar spatial light modulator (SLM) and a 45° conical mirror. Although the 360° viewing zone is successfully achieved in the horizontal direction, in the previous study, the vertical viewing zone remains as narrow as the planar holography, and its expansion is not only necessary but also potential due to the waste of vertical viewing zone in application scenarios such as tabletop and ceiling. In this paper, we propose a method of expanding the vertical effective viewing zone for optical 360° holographic display by using a conical mirror with a base angle of less than 45°. The proposed method can expand the vertical effective viewing zone by shifting the wasted vertical viewing zone into an effective vertical viewing zone from the base to the top angle direction of the conical mirror, which is up to two times theoretically. The feasibility and effectiveness of the proposed method are demonstrated by optical experiments. We believe that it would be promising in the field of augmented reality.