Computer-generated Holographic Stereogram Research Articles

Efficient Hogel-Based Hologram Synthesis Method for Holographic Stereogram Printing

With the development of the holographic printer, printing synthetic hologram requires smaller holographic element (hogel) size to improve spatial resolution of the reconstruction. On the contrary, a larger hogel size affords higher angular resolution, but it leads to a lower lateral resolution and there exists a trade-off problem. In this paper, a hologram synthesis method based on three-dimensional (3D) rendering of computer-generated holographic stereogram (HS) is proposed to limit the spatial-angular trade-off problem. The perspectives of the 3D scene are captured by re-centering the camera method and transformed into parallax-related images by a proposed pixel re-arrangement algorithm for holographic printing. Unlike the conventional approaches, the proposed algorithm not only improves the angular resolution of the reconstruction while maintaining the hogel size fixed, but also keeps the spatial resolution without degradation. The effectiveness of the proposed method is verified by numerical simulation and an optical experiment.

Fast calculation of high-definition depth-added computer-generated holographic stereogram by spectrum-domain look-up table [Invited

High-definition depth-added computer-generated holographic stereogram (DA-CGHS) is superior in its high quality, easy realization, and auto-shading effect. However, its computing cost is extremely high because numerous scenes together with depth information must be calculated. Here, we proposed a fast calculation scheme of DA-CGHS by the spectrum-domain look-up table (SDLUT) method. In SDLUT, diffraction fields on the hogel plane of selected reference points in the object space are calculated. Subsequently, the fields are Fourier transformed to the spectrum domain. Because the signal energy always concentrates in a small spectrum region, these regions are cropped as the elemental tables. In the computing of the hogels, the field superposition is conducted in the spectrum domain by using the elemental tables. In our demonstration, the table size of SDLUT is only 0.44% that of the look-up table (LUT). Because the table size is very small, the computing time of SDLUT method can be nearly 80 times faster than that of conventional LUTs in the spatial domain, while the image quality is comparable.

Performance Improvement for Computer-Generated Holographic Stereogram Based on Integral Imaging

Performance Improvement for Computer-Generated Holographic Stereogram Based on Integral Imaging

Performance Improvement for Computer-Generated Holographic Stereogram Based on Integral Imaging

Performance Improvement for Computer-Generated Holographic Stereogram Based on Integral Imaging

Highly efficient calculation method for computer-generated holographic stereogram using a lookup table.

A highly efficient calculation method to synthesize a computer-generated holographic stereogram using a lookup table (LUT) is proposed. The complete phase distribution (CPD) of a spherical wave that is larger than the hologram is precalculated and stored as a LUT. The wavefront converging to each viewpoint can be directly obtained by adding a specific part of the precalculated CPD to the parallax image, instead of computing the wavefronts pixel by pixel in the conventional method. The computation amount and calculation time are effectively reduced to one-third of the conventional method. The working memory size is reduced effectively using the symmetry of the phase distributions of different viewpoints. A simulation and an optical experiment are performed to verify the proposed method.

High-resolution full-parallax computer-generated holographic stereogram created by e-beam technology

A high-resolution computer-generated stereogram for forming full-parallax three-dimensional (3-D) images is proposed. A full-parallax 3-D image is formed from 825 two-dimensional (2-D) projections and can be observed in a wide angular range. The stereogram is a reflective diffractive optical element (DOE) that consists of 50×50 μm2 hogels, where each hogel corresponds to one pixel of the 2-D frames. A phase-type kinoform is computed in every hogel by solving a nonlinear inverse problem. The DOE relief is fabricated using electron-beam technology with pixel size of 0.2×0.2 μm2. The effectiveness of the technology developed is illustrated by photographs and a video of a real DOE under monochromatic light and under white light. The new high-resolution full-parallax stereograms can be used for protecting bank notes, documents, and ID cards against counterfeit.