Volume-reduced floating display based on a holographic optical element

In this paper, we propose a volume-reduced floating display based on a holographic optical element (HOE). The critical problem of a conventional floating display is a huge size, and this drawback limits its practical application. To overcome this drawback, the proposed floating display used the HOE for a reduction of the volume instead of a half mirror. Generally, the HOE can control the diffraction angle of the propagating wavefield. Also, the suitable HOE can be designed depending on the structure or a requirement of the floating display. So, the volume of the proposed floating display can be reduced through the HOE when the HOE is designed to reduce the diffraction angle. In the proposed floating display, the HOE is inclined at a certain angle in front of the retroreflective film. And, the projector and diffuser are set up the bottom of the inclined HOE. Wavefields propagated from the projector are formed as an image on the diffuser and, diffracted by the HOE into the retroreflective film. These diffracted wavefields are reflected by the retroreflective film back toward the direction of the propagating wavefields. As a result, the floated image is formed in the real space. For the optical experiment, we designed a HOE and set up the proposed floating display. Experimental result shows that the image is formed in real space like the conventional floating display. Also, we confirm that the volume of the floating display is reduced by as much as 35.6 % compared with the conventional floating display.