Providing a natural 3D visualization is a major challenge in 3D display technologies. Although 3D displays with light-ray reconstruction have been demonstrated, displayable 3D scenes are selective because their depth-reconstruction range is restricted. Here, we attempt to expand the range virtually by introducing "depth-compressed expressions," in which the depth of 3D scenes are compressed or modified in the axial direction so that the appearances of depth-compressed scenes is kept natural for viewers. With a simulated system of an autostereoscopic 3D display with light-ray reconstruction, we investigated how large the depth range needed to be to show the depth-compressed scenes without inducing unnaturalness in viewers. Using a linear depthcompression method—the simplest way of depth-compression—we found that viewers did not feel unnaturalness for the depthcompressed scenes that were expressed within at most half the depth range of the originals. These results gave us a design goal in developing 3D displays for high quality 3D visualization.
We developed a novel projection-type integral threedimensional (3D) display method using multiple projectors and displayed a 3D image with a wide viewing angle. In the proposed method, the viewing angle and positions of light spots that become pixels of a 3D image are controlled by projecting elemental images onto a lens array at a predetermined angle as collimated light beams. By projecting elemental images at different angles from multiple projectors installed at optimal positions, the viewing angle is enlarged, and the resolution is enhanced. We prototyped a projection-type integral 3D display system consisting of five ultra high definition (UHD) projectors with a viewing angle of 40 degrees in the horizontal and vertical directions while having a resolution of 114 thousand dots in the center view. We experimentally verified the display performance of the prototype display system and confirmed the validity of the proposed method.