自由立体显示系统背光控制

介绍一种基于瞳孔跟踪的多用户自由立体显示器,利用菲涅尔透镜形成左右眼分立照明区域。本系统采用LCD作为基本显示屏幕,通过指向式LED照明背光设计,高精度瞳孔实时定位装置对人眼位置的探测,AVR单片机的系统控制,形成实时定向跟踪人眼的立体视窗。本装置可提供±25°水平视角范围内1至3人的实时无辅助立体显示。     

A polarization modulated directional backlight autostereoscopic display

A polarization modulated directional backlight autostereoscopic display is proposed and demonstrated. The system consists of the orthogonally polarized backlight, the Fresnel lens array, a light shaping diffuser film, and a liquid crystal display (LCD) with a microphase retardation film. The autostereoscopic image pair carried by the directional light with different polarization directions is simultaneously projected to different spatial directions. The simulation and experimental results show that the directional projection of parallax images is realized for a high-quality autostereoscopic display with large viewing angle and continuous viewing volume, hence making it suitable for practical applications.     

Resolution enhancement of integral‐imaging three‐dimensional display using directional elemental image projection

Abstract— A new approach to resolution enhancement of an integral‐imaging (II) three‐dimensional display using multi‐directional elemental images is proposed. The proposed method uses a special lens made up of nine pieces of a single Fresnel lens which are collected from different parts of the same lens. This composite lens is placed in front of the lens array such that it generates nine sets of directional elemental images to the lens array. These elemental images are overlapped on the lens array and produce nine point light sources per each elemental lens at different positions in the focal plane of the lens array. Nine sets of elemental images are projected by a high‐speed digital micromirror device and are tilted by a two‐dimensional scanning mirror system, maintaining the time‐multiplexing sequence for nine pieces of the composite lens. In this method, the concentration of the point light sources in the focal plane of the lens array is nine‐times higher, i.e., the distance between two adjacent point light sources is three times smaller than that for a conventional II display; hence, the resolution of three‐dimensional image is enhanced.     

Lumisight Table: an interactive view-dependent tabletop display

A novel tabletop display provides different images to different users surrounding the system. It can also capture users' gestures and physical objects on the tabletop. The Lumisight Table approach is based on the optical design of a special screen system composed of a building material called Lumisty and a Fresnel lens. The system combines these films and a lens with four projectors to display four different images, one for each user's view. In addition, we need appropriate input methods for this display media. In the current state of the project, we can control computers by placing physical objects on the display or placing our hands over the display. This screen system also makes it possible to use a camera to capture the appearance of the tabletop from inside of the system. Our other main idea is to develop attractive and specialized applications on the Lumisight Table, including games and applications for computer-supported cooperative-work (CSCW) environments. The projected images can be completely different from each other, or partially identical and partially different. Users can share the identical parts as public information, because all users can see it. This article is available with a short video documentary on CD-ROM.     

A high‐resolution autostereoscopic display system with a wide viewing angle using an LCOS projector array

Abstract— This study develops an autostereoscopic display based on a multiple miniature projector array to provide a scalable solution for a high‐resolution 3‐D display with large viewing freedom. To minimize distortion and dispersion, and to maximize the modulation transfer function (MTF) of the projection image to optimize 3‐D image quality, a dedicated projection lens and an accurate six‐axis adjusting platform for the miniature projector were designed and fabricated. Image‐blending technology based on a lookup table was adopted to combine images from 30 miniature projectors into a seamless single image. The result was a 35‐in. autostereoscopic display with 60 views ata 30° viewing angle, 90° FOV, and large range of viewing distance. The proposed system exhibits very smooth motion parallax when viewers move around in front of it.     

High‐quality direct‐view display combining multiple integral 3D images

This paper proposes a method for combining multiple integral three‐dimensional (3D) images using direct‐view displays to obtain high‐quality results. A multi‐image combining optical system (MICOS) is used to enlarge and combine multiple integral 3D images without gaps. An optical design with a simple lens configuration that does not require a diffuser plate prevents the deterioration in resolution resulting from lens arrangement errors and the diffuser plate. An experiment was performed to compare a previously developed method with the proposed method, and the latter showed a significant improvement in image quality. A method for expanding the effective viewing angle of the proposed optical design was also developed, and its effectiveness was confirmed experimentally. A prototype device of the proposed optical design was constructed using a high‐density organic light‐emitting diode (OLED) panel with 8K resolution and 1058 ppi pixel density to achieve 311 (H) × 175 (V) elemental images, a viewing angle of 20.6° in both the horizontal and vertical directions, and a display size of 9.1 in. In addition, the proposed optical design enabled making device considerably thinner, ie, with a thickness of only 47 mm.     

Dual layered display that presents auto‐stereoscopic 3D images to multiple viewers in arbitrary positions

Dual layered display or also called tensor display that consists of two panels in a stack can present full‐parallax 3D images with high resolution and continuous motion parallax by reconstructing corresponding light ray field within a viewing angle. The depth range where the 3D images can be displayed with reasonable resolution, however, is limited around the panel stack. In this paper, we propose a dual layered display that can present stereoscopic images to multiple viewers located at arbitrary positions in observer space with high resolution and large depth range. Combined with the viewer tracking system, the proposed method provides a practical way to realize high‐resolution large‐depth auto‐stereoscopic 3D display for multiple observers without restriction on the observer position and the head orientation.     

Crosstalk‐free dual‐view integral imaging display

We propose a crosstalk‐free dual‐view integral imaging display. It is composed of a display panel, a barrier array, and a micro‐lens array. The central barrier is located at the vertical central axes of the display panel and the micro‐lens array to split the element image array and the viewing zone. Moreover, other barriers are located at the margins of the elemental images and corresponding micro‐lenses to eliminate the crosstalk. The lights emitting from the left and right half of the element image array are modulated by the left and right half of the micro‐lens array to reconstruct the right and left viewing zones, respectively. A prototype of the proposed dual‐view integral imaging display is developed, and good experimental results agree well with the theory.     

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

Abstract— 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.     

Toward the light field display: autostereoscopic rendering via a cluster of projectors

Ultimately, a display device should be capable of reproducing the visual effects observed in reality. In this paper we introduce an autostereoscopic display that uses a scalable array of digital light projectors and a projection screen augmented with microlenses to simulate a light field for a given three-dimensional scene. Physical objects emit or reflect light in all directions to create a light field that can be approximated by the light field display. The display can simultaneously provide many viewers from different viewpoints a stereoscopic effect without head tracking or special viewing glasses. This work focuses on two important technical problems related to the light field display; calibration and rendering. We present a solution to automatically calibrate the light field display using a camera and introduce two efficient algorithms to render the special multi-view images by exploiting their spatial coherence. The effectiveness of our approach is demonstrated with a four-projector prototype that can display dynamic imagery with full parallax.     

Analysis of longitudinal viewing freedom of reduced‐view super multi‐view display and increased longitudinal viewing freedom using eye‐tracking technique

Abstract— The viewing freedom of the reduced‐view super multi‐view (SMV) display was analyzed. It was found that there are separate multiple viewing ranges in the depth direction; thus, a technique that selects an appropriate viewing range to increase the longitudinal viewing freedom has been developed. Pixels of a flat‐panel display viewed by the viewer's eyes through a lenticular lens were determined from three‐dimensional (3‐D) positions of the viewer's eyes, which were obtained using an eye‐tracking system that employed a stereo camera. Parallax images corresponding to the 3‐D positions of the viewer's eyes were generated, which were displayed by the determined pixels. The experimental results show that the proposed technique successfully increased the longitudinal viewing freedom. It is also shown that a video camera was able to focus on the produced SMV images.     

Self‐calibration three‐dimensional light field display based on scalable multi‐LCDs

Approach to achieve self‐calibration three‐dimensional (3D) light field display is investigated in this paper. The proposed 3D light field display is constructed up on spliced multi‐LCDs, lens and diaphragm arrays, and directional diffuser. The light field imaging principle, hardware configuration, diffuser characteristic, and image reconstruction simulation are described and analyzed, respectively. Besides the light field imaging, a self‐calibration method is proposed to improve the imaging performance. An image sensor is deployed to capture calibration patterns projected onto and then reflected by the polymer dispersed liquid crystal film, which is attached to and shaped the diffuser. These calibration components are assembled with the display unit and can be switched between display mode and calibration mode. In the calibration mode, the imperfect imaging relations of optical components are captured and calibrated automatically. We demonstrate our design by implementing the prototype of proposed 3D light field display by using modified off‐the‐shelf products. The proposed approach successfully meets the requirement of real application on scalable configuration, fast calibration, large viewing angular range, and smooth motion parallax.     

Evaluation of jerkiness of moving three‐dimensional images produced by high‐density directional display

Abstract— The jerkiness of moving three‐dimensional (3‐D) images produced by a high‐density directional display was studied. Under static viewing conditions in which subjects' heads did not move, jerkiness was more noticeable when moving 3‐D images were displayed in front of the display screen and was less noticeable when moving 3‐D images were displayed behind the screen. We found that the perception of jerkiness depended on the visual angular velocities of moving 3‐D images. Under dynamic viewing conditions in which subjects' heads were forced to move, when moving 3‐D images were displayed in front of the screen, jerkiness was less noticeable when the subjects' heads and 3‐D images moved in opposite directions and was more noticeable when they moved in the same direction. When moving 3‐D images were displayed behind the screen, jerkiness was less noticeable when subjects' heads and 3‐D images moved in the same direction and was more noticeable when they moved in opposite directions.     

LC GRIN lens mode with wide viewing angle for rotatable 2D/3D tablet

To widen the vertical and horizontal angular ranges where the lens performs well, the off‐axis performance of a liquid crystal gradient index (LC GRIN) lens is analyzed by the combined simulation system of an LC director simulator and a ray‐tracing simulator. We found that the angular difference between an LC alignment direction and an electrode array direction of the LC GRIN lens is one of significant parameters, and detailed conditions of structure are established. The measurement result shows that the developed structure reduces the degradation ratio in a luminance profile from 61% to 3.2%. We have applied a user tracking system for the rotatable 3D display, equipped with a detection of a panel orientation and a face position. As a result, we have developed a rotatable 2D/3D tablet whose 3D viewing azimuth angle is over 30° in both landscape and portrait orientations.     

3‐D mobile display based on dual‐directional light guides with a fast‐switching liquid‐crystal panel

Abstract— An autostereoscopic display based on dual‐directional light guides with a fast‐switching liquid‐crystal panel was designed and fabricated to provide better 3‐D perception with image qualities comparable to that of 2‐D displays. With two identical micro‐grooved light guides, each with a light‐controlled ability in one direction, two restricted viewing cones are formed to project pairs of parallax images to the viewer's respective eyes sequentially. Crosstalk of less than 10% located within ±8°–±30° and an LC response time of 7.1 msec for a 1.8‐in. LCD panel can yield acceptable 3‐D perceptions at viewing distance of 5.6–23 cm. Moreover, 2‐D/3‐D compatibility is provided in this module.     

Display illumination with modulated directional backlight

Illumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution.     

Viewing direction measurements on flat and curved flexible E‐paper displays

The viewing direction characterization of reflective displays is more demanding than for emissive displays because defined illumination–detection geometries must be maintained for each viewing direction. In addition, the geometry should mimic the behavior of viewers who tend to exclude the reflection of light sources from a handheld reflective display. Viewing direction data was extracted from measured Bidirectional Reflectance Distribution Functions, showing that a source inclination of 45° sufficiently excludes the specular and haze components of source reflection from the measurement. Applying this so‐called 45/θ geometry to curved flexible displays is not straightforward since viewing direction, display curvature, and alignment each affect the measured reflectance. The viewing direction geometry proposed for convex cylindrical displays uses a ring light to deliver viewing‐direction independent illuminance, and maps the range of viewing directions onto the pixels of an image sensor. The illumination can also be applied to flat displays, allowing direct comparisons of flat and cylindrical display states. First results on e‐paper show good agreement with Bidirectional Reflectance Distribution Function data.     

A new LCL-lens array with electrodes of interlaced structure to be applied for auto-stereoscopic 3D displays

A new design of the liquid crystal lenticular (LCL) lens array with interlaced electrodes is proposed to realize an auto-stereoscopic 3D display. The structure of interlaced electrodes aims to generate a desired non-uniform electric filed to improve the focusing ability of the LCL-lens array with lower voltage drives. This paper is organized as first to describe the design criteria of a lenticular lens sheet for wide extended graphics array LCD panel. Based on the designed lenticular lens array, an LCL-lens array with proposed interlaced electrodes is next designed. The fabrication and the detailed structure are given. A series of experiments are then conducted and successfully verify the focusing capability and desired 3D display functions, that is, to separate two images to right and left eyes. Also, the developed auto-stereoscopic 3D display is able to adapt to varied viewer locations with favorable imaging quality.     

Full‐parallax autostereoscopic display with scalable lateral resolution using overlaid multiple projection

Abstract— A method to increase the viewing resolution of an autostereoscopic display without increasing the density of microlenses is proposed. Multiple projectors are used for the projection images to be focused and overlaid on a common plane in the air behind the microlens array. The multiple overlaid projection images yield multiple light spots inside the region of each elemental lenslet of the microlens array. This feature provides scalable high‐resolution images by increasing the number of projectors. Based on the proposed method, a prototype display that includes 15 projectors was designed and built. 3‐D images were successfully reproduced on the prototype display with full parallax and a wide viewing angle of 70°.     

Multi‐view 3‐D display employing a flat‐panel display with slanted pixel arrangement

Abstract— A flat‐panel display with a slanted subpixel arrangement has been developed for a multi‐view three‐dimensional (3‐D) display. A set of 3M × N subpixels (M × N subpixels for each R, G, and B color) corresponds to one of the cylindrical lenses, which constitutes a lenticular lens, to construct each 3‐D pixel of a multi‐view display that offers M × N views. Subpixels of the same color in each 3‐D pixel have different horizontal positions, and the R, G, and B subpixels are repeated in the horizontal direction. In addition, the ray‐emitting areas of the subpixels within a 3‐D pixel are continuous in the horizontal direction for each color. One of the vertical edges of each subpixel has the same horizontal position as the opposite vertical edge of another subpixel of the same color. Cross‐talk among viewing zones is theoretically zero. This structure is suitable for providing a large number of views. A liquid‐crystal panel having this slanted subpixel arrangement was fabricated to construct a mobile 3‐D display with 16 views and a 3‐D resolution of 256 × 192. A 3‐D pixel is comprised of 12 × 4 subpixels (M = 4 and N = 4). The screen size was 2.57 in.