Dongkyung Nam

Optimal projector configuration design for 300-Mpixel multi-projection 3D display

To achieve an immersive natural 3D experience on a large screen, a 300-Mpixel multi-projection 3D display that has a 100-inch screen and a 40° viewing angle has been developed. To increase the number of rays emanating from each pixel to 300 in the horizontal direction, three hundred projectors were used. The projector configuration is an important issue in generating a high-quality 3D image, the luminance characteristics were analyzed and the design was optimized to minimize the variation in the brightness of projected images. The rows of the projector arrays were repeatedly changed according to a predetermined row interval and the projectors were arranged in an equi-angular pitch toward the constant central point. As a result, we acquired very smooth motion parallax images without discontinuity. There is no limit of viewing distance, so natural 3D images can be viewed from 2 m to over 20 m.

A Unified Method for Crosstalk Reduction in Multiview Displays

The slanted lenticular sheet-based multiview display usually suffers both extrinsic crosstalk resulting from fabrication errors or assembling errors and intrinsic crosstalk originating from the leaked light from the two closest neighboring views. In this paper, a unified method is proposed to eliminate the extrinsic crosstalk and alleviate the intrinsic crosstalk simultaneously by adjusting the predefined view index (i.e., the corresponding viewpoint number) and grayscale intensity of each LCD subpixel. Two sets of patterns are utilized: structured light patterns are applied for building the correspondence between LCD subpixels and the captured photos pixels, and intensity test images are used for determining the brightness of LCD subpixels observed at given viewing points. Then the optimal view index for each LCD subpixel can be obtained for extrinsic crosstalk elimination according to the calculated correspondence and the estimated subpixel brightness. Moreover, the crosstalk coefficients for each subpixel can also be computed according to the correspondence and brightness, which are used for intrinsic crosstalk reduction. Experimental results prove the effectiveness of our method.

Precise eye localization with improved SDM

In this paper, we propose a precise and fast eye center localization method. The method is based on SDM [1] algorithm, which has achieved impressive performance in face alignment area. In this work, we further improve the basic SDM algorithm in two aspects: 1) employ the coarse to fine strategy to enhance the robustness to initialization; 2) utilize multiple nonlinear features to ensure the robustness while improve the accuracy. Experimental results on BioID database shows that our improved SDM achieves preferable localization accuracy against the state-of-the-art methods at a speed as fast as 2ms to locate two eyes.

61.4: Active Crosstalk Reduction on Multi‐View Displays Using Eye Detection

Multi-view displays have some problems in the quality of images, while they provide glasses-free systems. Especially inter-view crosstalk is the most critical factor to deteriorate the image quality and cause visual fatigue under large depths. We propose a method to provide clear images appropriate to the positions of the observers eyes. In a subpixel group, using the visibility profiles of the subpixels expressing each view, we can determine the subpixel values to express a certain color at a certain direction. This can compensate color distortion caused by slanted lenticular lens and expand the observable area using the repeated regions neighboring the main region.

Efficient Light-Field Rendering Using Depth Maps for 100-Mpixel Multi-Projection 3D Display

In order to achieve an immersive, natural 3D experience on a large screen, a 100-Mpixel multi-projection 3D display was developed. Ninety-six projectors were used to increase the number of rays emanating from each pixel in the horizontal direction to 96. Conventional algorithms use a large number of cameras or input images to process a large number of light rays. This creates difficulties in the design of both the large acquiring system and substantial memory storage. In this paper, we propose an efficient light-field rendering algorithm that utilizes only a few input colors and depth images. Using a depth map and estimated camera parameters, synthesized light-field images are directly generated. This algorithm requires a much lighter memory load than conventional light-field rendering algorithms. It is also much simpler than the image-based rendering algorithm because it does not require the generation of so many multiview images.

3D Display Calibration by Visual Pattern Analysis

Nearly all 3D displays need calibration for correct rendering. More often than not, the optical elements in a 3D display are misaligned from the designed parameter setting. As a result, 3D magic does not perform well as intended. The observed images tend to get distorted. In this paper, we propose a novel display calibration method to fix the situation. In our method, a pattern image is displayed on the panel and a camera takes its pictures twice at different positions. Then, based on a quantitative model, we extract all display parameters (i.e., pitch, slanted angle, gap or thickness, and offset) from the observed patterns in the captured images. For high accuracy and robustness, our method analyzes the patterns mostly in the frequency domain. We conduct two types of experiments for validation; one with optical simulation for quantitative results and the other with real-life displays for qualitative assessment. Experimental results demonstrate that our method is quite accurate, about a half order of magnitude higher than prior work; is efficient, spending less than 2s for computation; and is robust to noise, working well in the SNR regime as low as 6dB.

Sampling and error analysis of radial symmetric interpolation for fast hologram generation.

In this paper, we present a fast hologram pattern generation method by radial symmetric interpolation, which exploits concentric redundancy of a point hologram pattern to reduce computational complexity in hologram pattern calculation, and analyze the quality degradation sources in the proposed method. Compared to the analytic method in which phase and amplitude information is directly calculated from a wave equation, in our method a Fresnel zone plate is periodically sampled along a diagonal line and the wave information of a point hologram is calculated by linear interpolation. During these sampling and interpolation processes, the wave information can be modified from the original signal and the reconstruction quality can be degraded compared to the analytic pattern calculation method. The effects of sampling and linear interpolation are investigated in spatial and frequency domains.

Autostereoscopic 3D — How can we move to the next step?

The 3DTV market has already started and more people have been enjoying new visual experience. But annoyance of wearing 3D glasses is a problem and the autostereoscopic display still has several limitations unsolved. This presentation discusses these limitations and our approaches to overcome them.

Analysis of blur characteristics on 3D displays

This paper analyzes the image blur characteristics on autostereoscopic 3D (A3D) displays. The A3D displays have an advantage in providing the stereoscopic vision to users without glasses, but the users suffer from the blurred image especially when the depth of image increases. We have analyzed the relationship between the light distribution of the generated rays and the blur characteristics of the images. The analysis result will be useful in designing and evaluating multiview displays, integral displays and other light field based 3D displays.

Light field reconstruction

To overcome the limitations of multiview displays and get more freedom in designing 3D display architectures, we have developed and tested three different 3D displays based on the light field reconstruction concept. In this paper, I will explain the implementation results of each prototype and talk about the potential possibilities for more natural 3D displays.