Gilbae Park

Wide viewing angle dynamic holographic stereogram with a curved array of spatial light modulators

A novel design of dynamic holographic stereogram with a curved array of spatial light modulators (SLMs) is proposed. In general, it is difficult to simultaneously achieve a wide viewing angle and an available width for the digital holographic display. Moreover, the wide viewing angle of a display system needs a large optical numerical aperture where the paraxial approximation fails, and thus an extremely large planar SLM is necessary in using previous methods. To solve this problem, our proposed display system is composed of a curved array of SLMs to obtain a large number of data points and reduce the spatial bandwidth in SLMs. In the curved array of SLMs, each SLM is individually transformed to display local angular spectra of object wave, which is based on a fundamental idea of holographic stereogram. To embody the dynamic holographic stereogram with SLMs, each SLM is effectively reformed for simplifying the optical structure and reducing the light power loss. In detail, spatially modulated wave is optically divided and transformed, as if each SLM were composed of three sub-SLMs. This design improves the scalability in viewing angle of holographic display and the loss of light power is significantly reduced. With this method, we can achieve the digital holographic display with 22.8 degrees viewing angle.

Depth-enhanced integral imaging display system with electrically variable image planes using polymer-dispersed liquid-crystal layers

A depth-enhanced three-dimensional integral imaging system with electrically variable image planes is proposed. For implementing the variable image planes, polymer-dispersed liquid-crystal (PDLC) films and a projector are adopted as a new display system in the integral imaging. Since the transparencies of PDLC films are electrically controllable, we can make each film diffuse the projected light successively with a different depth from the lens array. As a result, the proposed method enables control of the location of image planes electrically and enhances the depth. The principle of the proposed method is described, and experimental results are also presented.

Color moiré pattern simulation and analysis in three-dimensional integral imaging for finding the moiré-reduced tilted angle of a lens array.

We propose a color moiré pattern simulation and analysis method in integral imaging for finding the moiré-reducing tilted angle of a lens array. According to the tilted angle, the color moiré patterns are simulated on the assumption of ray optics. The spatial frequencies of the color moiré patterns are numerically analyzed using a spatial Fourier transform for finding the optimal angle where the moiré is reduced. With the proposed technique the visualization of the color moiré pattern and its analysis are enabled. The moiré-reduced three-dimensional images can be displayed. The principle of the proposed method, simulation results, and their analysis are provided. Experimental results verify the validity of the proposed method.

View image generation in perspective and orthographic projection geometry based on integral imaging.

A novel technique generating arbitrary view images in perspective and orthographic geometry based on integral imaging is proposed. After capturing three-dimensional object using a lens array, disparity estimation is performed for the pixels at the selected position of each elemental image. According to the estimated disparity, appropriate parts of elemental images are mapped to synthesize new view images in perspective or orthographic geometry. As a result, the proposed method is capable of generating new view images at arbitrary positions with high resolution and wide field of view.

Reconstruction of three-dimensional occluded object using optical flow and triangular mesh reconstruction in integral imaging

We proposed a reconstruction method for the occluded region of three-dimensional (3D) object using the depth extraction based on the optical flow and triangular mesh reconstruction in integral imaging. The depth information of sub-images from the acquired elemental image set is extracted using the optical flow with sub-pixel accuracy, which alleviates the depth quantization problem. The extracted depth maps of sub-image array are segmented by the depth threshold from the histogram based segmentation, which is represented as the point clouds. The point clouds are projected to the viewpoint of center sub-image and reconstructed by the triangular mesh reconstruction. The experimental results support the validity of the proposed method with high accuracy of peak signal-to-noise ratio and normalized cross-correlation in 3D image recognition.

Implementation of polarization-multiplexed tiled projection integral imaging system

— A 40-in. tiled projection integral imaging system has been implemented, adopting a polarization-multiplexing technique. The system is composed of two full-high-definition (HD) projectors, a time-varying polarizer, a polarization preserving screen, polarization films, a lens array, and a control unit. An elemental image set is projected using two full-HD projectors to enhance the resolution of the system. The viewing region of the system is increased by using a polarization switching method. The polarization state of the elemental image set is changed by the time-varying polarizer, and the elemental image set is diffused by the polarization preserving screen. The elemental image set with a preserved polarization state forms a three-dimensional image with increased viewing angle by the integration of a lens array with polarization films. A 60-in. tiled projection integral imaging system was also demonstrated using four full-HD projectors.

Three-dimensional integral display using plastic optical fibers

A novel approach to an integral imaging system using a pliable plastic optical fiber array is proposed. The proposed system has the advantage that it can utilize a light source for three-dimensional (3D) images at an arbitrary location because the point light sources are formed by the plastic fiber array with flexible optical paths. Two-dimensional images can also be expressed in the proposed system. The light efficiency of this system is high compared with previous point light source array integral imaging systems. The feasibility of the proposed method is explained and demonstrated with experiments.

Enhancement of Viewing Angle and Viewing Distance in Integral Imaging by Head Tracking

We present a head-tracking based method for improving viewing angle and viewing distance in integral imaging system. Elemental images can be made in different regions as the position of a viewer dynamically changes.

Integral imaging with reduced color moire pattern by using a slanted lens array

In this paper, we propose a color moire pattern reduction method in integral three-dimensional imaging by slanting the lens array. The color moire patterns are examined as varying the slanted angles between the lens array and the display panel for choosing the angles for which the pattern is reduced. However, it is difficult to expect the tendency of the pattern. We simulate the color moire pattern on the assumption of ray optics and find out the angle where the moiré is reduced. With the proposed technique clear three dimensional images can be displayed. The explanation of the proposed method will be provided, and the simulation results will be shown. Finally, experimental results will verify the proposed method.

360°-viewable cylindrical integral imaging system using a 3-D/2-D switchable and flexible backlight

— A 360°-viewable cylindrical three-dimensional (3-D) display system based on integral imaging has been implemented. The proposed system is composed of a cylindrically arranged electroluminescent (EL) pinhole film, an EL film backlight, a barrier structure, and a transmission-type flexible display panel. The cylindrically arranged point-light-source array, which is generated by the EL pinhole film reconstructs 360°-viewable virtual 3-D images at the center of the cylinder. In addition, the proposed system provides 3-D/2-D convertibility using the switching of EL pinhole film from a point light source to a surface light source. In this paper, the principle of operation, analysis of the viewing parameters, and the experimental results are presented.