We discuss on the recent state of the augmented reality (AR) display technology. In order to realize AR, various seethrough three-dimensional (3D) display techniques have been reported. We describe the AR display with 3D functionality such as light-field display and holography. See-through light-field display can be categorized by the optical elements which are used for see-through property: optical elements controlling path of the light-fields and those generating see-through light-field. Holographic display can be also a good candidate for AR display because it can reconstruct wavefront information and provide realistic virtual information. We introduce the see-through holographic display using various optical techniques.
In this paper, we propose the index matched anisotropic crystal lens. The proposed optical element acts as a transparent glass in extraordinary polarized light and a lens in ordinary polarized light. The conceptual diagram and principle of the index matched anisotropic crystal lens are presented and the ray tracing simulation is performed to verify and analyze the functionality and the distortion of the real world scene. The index matched anisotropic crystal lens is implemented with calcite and the index matching liquid. The preliminary system to show the feasibility of the proposed optical element is implemented. The lens mode and the transparent mode are presented and the distortion along the incident direction of the light is also analyzed by the experiment. It is expected that the index matched anisotropic crystal lens can be a good candidate for the head-up display and head-mounted display.
A head-mounted compressive three-dimensional (3D) display system is proposed by combining polarization beam splitter (PBS), fast switching polarization rotator and micro display with high pixel density. According to the polarization state of the image controlled by polarization rotator, optical path of image in the PBS can be divided into transmitted and reflected components. Since optical paths of each image are spatially separated, it is possible to independently focus both images at different depth positions. Transmitted p-polarized and reflected s-polarized images can be focused by convex lens and mirror, respectively. When the focal lengths of the convex lens and mirror are properly determined, two image planes can be located in intended positions. The geometrical relationship is easily modulated by replacement of the components. The fast switching of polarization realizes the real-time operation of multi-focal image planes with a single display panel. Since it is possible to conserve the device characteristic of single panel, the high image quality, reliability and uniformity can be retained. For generating 3D images, layer images for compressive light field display between two image planes are calculated. Since the display panel with high pixel density is adopted, high quality 3D images are reconstructed. In addition, image degradation by diffraction between physically stacked display panels can be mitigated. Simple optical configuration of the proposed system is implemented and the feasibility of the proposed method is verified through experiments.
In this paper, we propose the see-through parallax barrier type multi-view display with transparent liquid crystal display
(LCD). The transparency of LCD is realized by detaching the backlight unit. The number of views in the proposed
system is minimized to enlarge the aperture size of parallax barrier, which determines the transparency. For
compensating the shortness of the number of viewpoints, eye tracking method is applied to provide large number of
views and vertical parallax. Through experiments, a prototype of see-through autostereoscopic 3D display with parallax
barrier is implemented, and the system parameters of transmittance, crosstalk, and barrier structure perception are
We propose a multi-projection based multi-view 3D display system using an optical waveguide. The images from the projection units with the angle satisfying the total internal reflection (TIR) condition are incident on the waveguide and experience multiple reflections at the interface by the TIR. As a result of the multiple reflections in the waveguide, the projection distance in horizontal direction is effectively reduced to the thickness of the waveguide, and it is possible to implement the compact projection display system. By aligning the projection array in the entrance part of the waveguide, the multi-view 3D display system based on the multiple projectors with the minimized structure is realized. Viewing zones are generated by combining the waveguide projection system, a vertical diffuser, and a Fresnel lens. In the experimental setup, the feasibility of the proposed method is verified and a ten-view 3D display system with compact size in projection space is implemented.
We propose a compact multi-projection system based on integral floating method with waveguide projection. Waveguide projection can reduce the projection distance by multiple folding of optical path inside the waveguide. The proposed system is composed of a wedge prism, which is used as a waveguide, multiple projection-units, and an anisotropic screen made of floating lens combined with a vertical diffuser. As the projected image propagates through the wedge prism, it is reflected at the surfaces of prism by total internal reflections, and the final view image is created by the floating lens at the viewpoints. The position of view point is decided by the lens equation, and the interval of view point is calculated by the magnification of collimating lens and interval of projection-units. We believe that the proposed method can be useful for implementing a large-scale autostereoscopic 3D system with high quality of 3D images using projection optics. In addition, the reduced volume of the system will alleviate the restriction of installment condition, and will widen the applications of a multi-projection 3D display.
We proposed the new optical design of the wedge projection display to enhance the quality of image. Since the thickness
of the wedge plate can be thin enough, this technology makes up for the bulky property in projection type display.
However, the image quality is heavily influenced by “dark zone”. The dark zone means the repeated region that the rays
cannot escape from the waveguide. Thus, these regions present nothing and the image quality is very low. To reduce the
problems, we analyzed the principle of the image formation by the geometrical retracing from the wedged surface to the
aperture of waveguide. The bundle of rays converging into an imaging point on the wedged surface have the same image
information, but can have the different initial position and the angle when started from the aperture. Therefore, each ray
is classified by the position of the imaging points on the inclined surface and the number of reflection. Based on the
classified data, we can obtain the equivalent imaging point which is the intersection when the set of the rays with the
same condition does not experience the reflection at the interface. Because this point is equivalent to the imaging point
on the inclined surface, we can display the image by projecting on the equivalent imaging point. In this paper, the
optimized set of equivalent imaging points is analyzed by retracing method and we designed the improved imaging
system of the wedge projection display by modifying the shape of aperture to equip the optical components in the onaxis.