Sung-Sik Kim

Desktop autostereoscopic display with head tracking capability

A desktop 20 inches autostereoscopic display system based on two 6.5 inches LCD projection panels and a single objective is described. The system employs vertical separation of left and right views in the objectives entrance pupil for the viewing zone forming. The vertically separated views are horizontally divided with use of a positioned at the pupil. This diaphragm is composed of two horizontally parallel LC stripes shutters which are made of independently working 32 black and white LCD columns. A rear projection type screen made of a Fresnel lens with a vertical diffuser is used for the image projection. The screen provides the best viewing distance of 70 - 80 cm. The system equipped with a head-tracking device for 16-view image display. The system is compatible with any dual monitor SVGA video card with resolution 800 X 600 or any source of parallel stereoscopic video signal. The size of the system is comparable to that of 20 inch CRT monitor.

Non-glasses type stereoscopic display system based on polarization

The problems related with a dichroic type polarization filter plate which is used as a spatial image separator for a non-glasses type stereoscopic display device utilizing a liquid crystal display panel are discussed. The filter plate is consisted of many parallel line filters. Each line filter is directing the light with the same polarization only to its corresponding pixel lines in the display panel. The filter plate is cemented to the display panel, back- illuminated by a halogen lamp through two cross-polarized polarizers in side by side. Two Fresnel lenses located before the filter plate for collimating the illuminating beam and after the liquid crystal display panel for forming the images of two polarizers in front of the liquid crystal display panel as viewing zones are used.

Analysis of color distortions in a transmission-type holographic screen.

Full-color transmission-type holographic screens for displaying stereoscopic and multiview images suffer color distortions, especially at their edges. These distortions arise because the reconstructed image of the diffuser appears not at a specified location at different locations for different parts of the screen. Analysis shows that the diffuser strip, which is an object that records the screen, should be extended further in the photoplate direction than in the conventional position to remove the distortions and that use of a short-wavelength laser in the blue spectral region, along with extending the diffuser, is recommended for recording large-sized screens. The analysis also allows the largest sizes of screens that can be recorded for a given set of parameters to be calculated. A comparison of the quality of the images displayed on the screens recorded in the conventional position and in the newly developed position has shown distinctive improvements for the new position.

Quadtree-based disparity estimation for intermediate view synthesis of stereoscopic image sequences

In stereoscopic or multiview 3-D display systems, the synthesis of intermediate sequences is essential to assure lookaround capability and continuous motion parallax so that it can enhance comfortable 3-D perception. The quadtree-based disparity estimation is one of the most popular methods for the synthesis of intermediate sequences, due to the simplicity of its algorithm and hardware implementation. We propose two solutions in order to reduce annoying flicker at object boundaries of synthesized intermediate sequences using quadtree-based disparity estimation. The first requires a new splitting scheme, providing more consistent quadtree splitting strategies during the disparity estimation. The second involves adaptive temporal smoothing, using the dissimilarity between the present frame and the previous one to reduce the error of disparity estimation. These two proposals are tested by using several stereoscopic sequences, and the results show that flicker is remarkably reduced by them.

Full parallax images with a diamond shape pixel cell

Characteristics and two building methods of diamond shaped pixel cell are introduced. It can provide wider horizontal direction size of viewing zone compared with its corresponding square or rectangular pixel cell and reduce the pseudoscopic effect. The two building methods are named as integer and non-integer depending on the number of different view pixels involved with the pixel cell. The full parallax images generated by these two methods shows that the integer method provides better image quality than the non-integer.

Autostereoscopic display with eye tracking

Auto-stereoscopic 21-inch display with eye tracking having wide viewing zone and bright image was fabricated. The image of display is projected to retinal through several optical components. We calculated optical system for wider viewing zone by using Inverse-Ray Trace Method. The viewing zone of first model is 155mm (theoretical value: 161mm). We could widen viewing zone by controlling paraxial radius of curvature of spherical mirror, the distance between lenses and so on. The viewing zone of second model is 208mm. We used two spherical mirrors to obtain twice brightness. We applied eye-tracking system to the display system. Eye recognition is based on neural network card based on ZICS technology. We fabricated Auto-stereoscopic 21-inch display with eye tracking. We measured viewing zone based on illumination area. The viewing zone was 206mm, which was close to theoretical value. We could get twice brightness also. We could see 3D image according to position without headgear.

Projection-type integral 3D imaging using multifacet flat mirrors

We propose a projection-type integral imaging scheme using multi-facet flat mirrors and demonstrate its feasibility. Instead of spherical mirrors on a flat surface, multi-facet flat mirrors which contacts with the tangential line of a curved surface function like elemental mirror component. Lights reflected from different facet of each mirrors give different viewing perspectives. By using electronic capturing and display devices, the proposed method makes it possible to record and reconstruct 3D scene in real-time. In the experiment, only horizontal parallax is provided because one-dimensional surface can be made more easily. But extension for two-dimensional or computer generation of elemental images can also be done.

Recent development of 3D display technology for new market

A multi-view 3D video processor was designed and implemented with several FPGAs for real-time applications and a projection-type 3D display was introduced for low-cost commercialization. One high resolution projection panel and only one projection lens is capable of displaying multiview autostereoscopic images. It can cope with various arrangements of 3D camera systems (or pixel arrays) and resolutions of 3D displays. This system shows high 3-D image quality in terms of resolution, brightness, and contrast so it is well suited for the commercialization in the field of game and advertisement market.

Processing full-parallax images in special cases

There are several ways of processing Images from multiview cameras for full parallax image generation. Among them, the most used one is laying the images as a rectangular shape pixel cell on the image display panel. However, it cannot maximize the stereoscopic effect and viewing zone size in horizontal direction with a given full parallax image set. A diamond shape pixel cells can maximize the stereoscopic effect and the viewing zone size in vertical direction. The sequence of making the diamond shape pixel cell includes two rotations of a multiview image with the rectangular pixel cell in opposite to each other with the same angle.

54.5: Holographic Screens for 3 Dimensional Image Projection

color transmission type holographic screen having a size of 40cm X 60cm are developed recently at Korea Institute of Science and Technology. This screen can be operated in reflection mode by adding a mirror at its back. This operation extends viewing angle of the screen to be more than 30degree. This wide viewing angle permits the screen to be operated in viewer tracking regime. By mosaicking the screens, a 120cm X 80cm screen is made. The mosaicked screen shows a good image performance. Introduction screen has been developed to use as an image projection screen for forming viewing zones for the projected images(1). It is a kind of holographic optical element(HOE)s which has the properties of a spherical mirror or a lens + a diffuser. Since HOE is basically a spectral selective component, full color images can not be projected on the holographic screen(2), unless a specific optical recording set-up is used or a special development process is developed. One good example of the screen is the image combiner in Head Up Display for airplanes(3). It is tuned to have the maximum diffraction efficiency for the spectral range corresponding to that of the image display device used for the Display, i.e., CRT. This means that the screen has an uniform period fringe structure. To make the screen has a wide spectral response comparable to visible spectral range, it is necessary to make the screen have a variable period fringe structure. Based on this concept, Korea Institute of Science and Technology(KIST) developed a full color transmission type holographic screen with use of a long slit type diffuser as an object(4). The screen creates a full color viewing zone for images projected from a projector by making the reconstructed diffuser image for each spectral com ponent of the images overlap partially in space. The viewers can perceive the full color images displayed on the screen through the viewing zone. The advantages of the holographic screen compared with popularly used optical plates to form viewing zones, such as Lenticular, Parallax Barrier and Integral Photography plates and Fresnel lens(5) are such that resolution and depth of the viewing zone of the screen are higher and more, respectively. However, making larger size screen with full color capability is difficult due to problems related with optimizing the recording set-up to minimize aberrations and exposition time, and changing viewing zones following to the viewers movement. It found that the problems could be solved by mosaicking smaller size screens and by operating the screen in a reflection mode. This reflection mode operation allows the angular selectivity of the screen to be two times of that of transmission mode. In this paper, some features of the full color transmission type holographic screens developed at KIST are described.