Researchers at the 5G Giga Communication Research Laboratory of South Korea’s Electronics and Telecommunications Research Institute have developed a novel tabletop display system for holographic images. The system allows multiple viewers to simultaneously view a hologram showing a full 3D image as they walk around the tabletop, giving complete 360° access. "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,” said Yongjun Lim, researcher at the 5G Giga Communication Research Laboratory. “Representative techniques included space-division multiplexing, time-division multiplexing and [a] combination of those two techniques.” Lim and his team took a different approach by devising and adding a novel viewing window design and paying close attention 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 two parabolic mirrors," Lim said. "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-in. size holograms from any position around the table without visual distortion.” Currently, the system produces a monochrome green color. Next, the team aims to produce a full-color experience and resolve issues related to undesirable aberration and brightness mismatch among the four digital micromirror devices used in the display. Collaborators on the project include colleagues from the Department of Electronics and Information Engineering of Korea University, and the School of Electronics Engineering at Kyungpook National University, South Korea.