Simplified digital content generation based on an inverse-directed propagation algorithm for holographic stereogram printing

Holographic stereogram (HS) printing requires extensive memory capacity and long computation time during perspective acquisition and implementation of the pixel re-arrangement algorithm. Hogels contain very weak depth information of the object. We propose a HS printing system that uses simplified digital content generation based on the inverse-directed propagation (IDP) algorithm for hogel generation. Specifically, the IDP algorithm generates an array of hogels using a simple process that acquires the full three-dimensional (3D) information of the object, including parallax, depth, color, and shading, via a computer-generated integral imaging technique. This technique requires a short computation time and is capable of accounting for occlusion and accommodation effects of the object points via the IDP algorithm. Parallel computing is utilized to produce a high-resolution hologram based on the properties of independent hogels. To demonstrate the proposed approach, optical experiments are conducted in which the natural 3D visualizations of real and virtual objects are printed on holographic material. Experimental results demonstrate the simplified computation involved in content generation using the proposed IDP-based HS printing system and the improved image quality of the holograms.

Annular sector elemental image array generation method for tabletop integral imaging 3D display with smooth motion parallax

One of the important features of tabletop 3D displays is the annular viewing area above the display system. In this paper, we propose an annular sector elemental image array (ASEIA) generation method for the tabletop integral imaging 3D display to form the annular viewing zone with smooth motion parallax. The effective pixels of the elemental images are distributed as annular sector, and they are mapped from the perspective images captured by the ring-shaped camera array. Correspondingly, the viewing sub-zones can be formed with an annular sector configuration and can be seamlessly stitched by using the time division scheme. Compared with the previous approach with rectangular elemental image array (EIA) distribution, the number of viewing sub-zones is decreased from 360 to 10 for the same effect of smooth motion parallax. Meanwhile, rendering efficiency is improved. The experimental results show that the proposed method is feasible to produce 360-degree continuous viewpoints in an annular viewing zone.

Integral imaging microscopy with enhanced depth-of-field using a spatial multiplexing

A depth-of-field enhancement method for integral imaging microscopy system using a spatial multiplexing structure consisting of a beamsplitter with dual video channels and micro lens arrays is proposed. A computational integral imaging reconstruction algorithm generates two sets of depth-sliced images for the acquired depth information of the captured elemental image arrays and the well-focused depth-slices of both image sets are combined where each is focused on a different depth plane of the specimen. A prototype is implemented, and the experimental results demonstrate that the depth-of-field of the reconstructed images in the proposed integral imaging microscopy is significantly increased compared with conventional integral imaging microscopy systems.

Analysis on image expressible region of integral floating

We define the image expressible region where three-dimensional (3D) images can be reconstructed in an integral floating display using ray distribution information. Here, the image expressible and viewing regions of the integral floating system, defined using ray distribution based on ray optics, are analyzed to resolve an image-cropping problem known as the viewing window that is due to the virtual aperture. Two experiments for verifying the image expressible and viewing regions are performed, and the results are presented. The obtained analysis is useful to maximize the viewing properties of integral floating.

Fast calculation method of computer-generated cylindrical hologram using wave-front recording surface

Fast calculation method for a computer-generated cylindrical hologram (CGCH) is proposed. The method consists of two steps: the first step is a calculation of a virtual wave-front recording surface (WRS), which is located between the 3D object and CGCH. In the second step, in order to obtain a CGCH, we execute the diffraction calculation based on the fast Fourier transform (FFT) from the WRS to the CGCH, which are in the same concentric arrangement. The computational complexity is dramatically reduced in comparison with direct integration method. The simulation results confirm that our proposed method is able to improve the computational speed of CGCH.