High-density recording of full-color full-parallax holographic stereogram

We demonstrate a high quality 3D image reproduced by a full-color, full-parallax holographic stereogram (HS) with high-density light-ray recording. The full-parallax HS is produced by a holographic 3D printer, which is an electronic controlled optical system for automatic recording. The HS consists of a 2D array structure of volume type elementary holograms, and full-parallax 3D image can be observed under white-light illumination. But the quality of the reconstructed image from the HS affected by the array structure which obstructs the reconstructed image. Then, in order to suppress the array structure, the size of elementary holograms is reduced to 50 × 50 micrometers as an invisible size. If the size of elementary holograms is reduced, however, the number of reproducible light-rays is decreased due to the diffraction limit. Thus we evaluate the light-ray density reconstructed by the full-parallax HS with the measurement of the angular resolution of diffracted light, and demonstrate the visual image quality of reconstructed 3D image when high-density light-rays are recorded. In the experiments, we prepared samples of HSs in which sizes of elementary holograms are from 50 to 400 micrometers, and measured the angular resolution of diffracted light. Moreover we synthesized HSs of 3-D artificial images, and visually evaluated their image quality. As a result, decrease in angular resolution was observed as the element size was reduced, though the angular resolution of reproduced light-rays is 1.08 degrees when the element size is 50 × 50 micrometers. But the image quality of 50 micrometers pitch HS was confirmed to be high enough to suppress the array structure when the depth of the reconstructed image is not very deep.