Chao-Hsu Tsai

Measurement of contrast ratios for 3D display

3D image display devices have wide applications in medical and entertainment areas. Binocular (stereoscopic) imaging without glasses, especially spatial-multiplexed displays such as lenticular display, barrier strip display, and single-lens stereoscopic display, is one of the most powerful and popular ways for life-like presentation of our 3D environments. The definition and relationship of the image contrast and viewer crosstalk are reviewed and clarified. They are measured and compared on three different types of 3D display systems, including shutter-glasses stereoscopic display, image splitter autostereoscopic display and dual-panel autostereoscopic display.

Designs of broadband and wide-view patterned polarizers for stereoscopic 3D displays

This work presents a new methodology to design patterned circular polarizers consisting of in-cell polarizers, in-cell retarders and biaxial films to achieve very wide viewing freedom for stereoscopic 3D color LCDs. The biaxial films with least materials and simple fabrication concepts are employed for off-axis compensation of the in-cell retarders. In the best result, the crosstalk ratio is less than 0.035 or 0.0082 respectively for over ± 60° or ± 40° viewing cone of the 3D display. As to the normal view of the proposed structure with glasses or LCD rotation, the crosstalk ratio is less than 0.11%, with 93.5% improvement as compared with the ± λ/4 patterned polarizer. The dispersion properties of materials have been considered in all simulations to mimic real situations.

How crosstalk affects stereopsis in stereoscopic displays

The ghost-image issue induced by crosstalk in stereoscopic, especially autostereoscopic, display systems has been believed to be a major factor to jeopardize stereopsis. Nevertheless, it is found that in some cases the stereopsis remains effective even with serious crosstalk. In fact, many other factors, such as contrast ratio, disparity, and monocular cues of the images, play important roles in the fusion of stereo images. In this paper, we study the factors in an image that may affect stereo fusion, and provide a macroscopic point of view to get a reasonable criterion of system crosstalk. Both natural and computer-generated images are used for detailed evaluation. Image processing techniques are adopted to produce desired characteristics. The results of this research shall be of reference value to content makers of stereoscopic displays, in addition to their designers.

Challenge of 3D LCD Displays

A multiview autostereoscopic LCD display with a localized 2D/3D switching function is developed based on the actively switchable parallax barrier technology. This switchable barrier comprises of an electro-optically switchable liquid crystal (LC) and a microretarder. Polymer dispersed liquid crystal (PDLC) with switchable clear and diffusing states and twisted nematic liquid crystal (TNLC) with polarization switching function are used as switching devices. The microretarder is prepared by self-developed multibeam laser scanning process, which is clean, friendly to the environment, and easy for scale up and mass production. The influence factors on the image qualities of 3D displays based on LCD panel technology are analyzed and discussed. Some solutions have proposed to solve the commercial application issues.

Fabricating microretarders by CO2 laser heating process technology

We describe an environment-friendly fabrication process for microretarders with a high contrast ratio and well-defined stripe bound- aries. It is shown that by accurately controlling the power, spot size, and scanning speed of a CO2 laser beam, the retardation property of a poly- meric film can be tailored within a localized area without altering that of the untreated areas. The measurements and analyses of the contrast ratios on the microretarders are presented. A microretarder can be used in many applications, especially in stereoscopic displays.

Fabricating polymeric microretardation arrays for autostereoscopic display system by CO2-laser heat processing technology

A micro-retardation array is a plate consisting of two or more optical retardation states that are micro-patterned within different regions of the plate. A LCD panel with the micro-retardation array can be used to display stereoscopic images watched with or without special glasses by encoding right-eye image and left-eye image with periodically horizontal stripes of different polarization states. For example, the odd rows of stripes are assigned to have zero retardation and the even rows of stripes with a half- wavelength retardation or vice versa. The width of each stripe is of the order of hundreds of microns. This paper describes a fabrication process of micro-retardation array with high contrast ratio, well-defined stripe boundary and green process. The fact that the retardation property of polymer film will be changed by heat process is used in this fabrication process. It is shown that by accurately controlling the power and spot-size of a CO2 laser, the retardation property of a polymeric film, such as PC and ARTON can be tailored within a localized area without altering the retardation of the untreated areas. In addition, the contrast ratios of micro-retardation array are measured and analyzed, the performance of an autostereoscopic display system using the micro-retardation array is also described.

32.4: Invited Paper: The Pursuit of High‐Definition 3D Display Technology

The status and limitation of 3D display technology are presented. Due to the difficulty in realizing high-definition autostereoscopic displays, glasses-type 3D displays are suggested as a better choice for home applications in short term and several technologies of them are introduced. However, autostereoscopic displays with comparable image quality with the glasses-type ones are definitely important for the popular acceptance of the products and the continue development of the 3D industry. In this paper, a method using proximity projector array to implement high-definition autostereoscopic displays is proposed for long-term development.

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

— 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.

Fabrication of a large F-number lenticular plate and its use as a small-angle flat-top diffuser in autostereoscopic display screens

A diffuser with large horizontal and vertical diffusion angle is a key component for the screen of a projection display. On the other hand, an autostereoscopic projection display needs a small horizontally diffused and large vertically diffused diffuser. A commercial LSD composed of cylindrical-based grains can be used to meet this requirement. Nevertheless, as the diffused intensity profile of a LSD is Gaussian-like, a LSD in many cases can cause either ghost imaging or black stripes while applied to the screen of autostereoscopic displays. Lenticular plates can produce a near flat-top diffusing profile when the divergence angle is small. For example, a lenticular plate with a 5 degrees divergence can be shown in theory to have only a 2.1 percent non-uniformity. However, as the curvature of the lenticular is very small, it becomes very difficult to fabricate such a lenticular plate. This paper reports a novel approach to modify a lenticular plate that was originally with a large divergence angle to a plate with a desired smaller divergence angle, without destroying the surface quality and maintaining good uniformity. The lenticular plate fabricated by using this approach was used as a screen diffuser of a projection-based autostereoscopic display, and the luminance of the screen viewed from different angles was measured.

The fabrication of microretarder for in-cell stereoscopic LCD using reactive liquid crystal

A microretarder for stereoscopic display is a film consisting of horizontal or vertical stripes with alternating null and half-wave phase retardation states. An LCD with a microretarder attached on the front side can display good-quality stereoscopic images when viewed with polarization glasses. It is now the easiest and cheapest way to present stereoscopic images on a flat-panel display. However, the space caused by the glass between the retarder layer and the LC layer of the panel seriously limits the vertical view angle, which, in turn, limits the application of this technology. In this paper, a process for thin-film microretarder is developed using reactive liquid crystal. The material and the process are essentially compatible with current LC panel processes. Since the thin-film microretarder is to be fabricated in the cell of an LC panel, the retarder layer and the LC layer can be fabricated as close to each other as possible. A nearly unlimited 3D view angle can be achieved for the display.