Researchers described a novel tabletop display system that allows multiple viewers to simultaneously view a hologram showing a full 3D image as they walk around the tabletop, giving complete 360-degree access. To be commercially feasible in a range of applications -- from medicine to gaming to media -- the hologram challenge is daunting. It involves scaling an electronic device to a size small enough to fit on a table top, while making it robust enough to render immense amounts of data needed to create a full-surround 3D viewing experience from every angle -- without the need for special glasses or other viewing aids. In the past, researchers interested in holographic display systems proposed or focused on methods for overcoming limitations in the combined spatial resolution and speed of commercially available, spatial light modulators. Representative techniques included space-division multiplexing (SDM), time-division multiplexing (TDM) and combination of those two techniques. Researchers from the 5G Giga Communication Research Laboratory, Electronics and Telecommunications Research Institute, South Korea took a different approach. They devised and added a novel viewing window design.
To implement such a viewing window design, close attention had to be paid to the optical image system. With a tabletop display, a viewing window can be created by using a magnified virtual hologram, but the plane of the image is tilted with respect to the rotational axis and is projected using with two parabolic mirrors. "But because the parabolic mirrors do not have an optically-flat surface, visual distortion can result. We needed to solve the visual distortion by designing an aspheric lens. As a result, multiple viewers are able to observe 3.2-inch size holograms from any position around the table without visual distortion. Building on these advances, the team hopes to implement a key design feature of strategically sizing the viewing window so it is closely related to the effective pixel size of the rotating image of the virtual hologram. Watching through this window, observers' eyes are positioned to accept the holographic image light field because the system tilts the virtual hologram plane relative to the rotational axis. To enhance the viewing experience the team hopes to design a system in which observers can see 3.2-inch holographic 3D images floating on the surface of the parabolic mirror system at a rate of 20 frames per second. Test results of the system using a 3D model and computer-generated holograms were promising.