LC Panel Research Articles

Two-Field Scheme: Spatiotemporal Modulation for Field Sequential Color LCDs

A novel displaying method, two-field driving scheme, was proposed for field sequential color LCDs without color filter. A spatially modulated color backlight provided multi-primary low-resolution optical stimuli, which were then compensated by an LC panel to display detailed colorful images. That is, the manipulation on three (or more) spatial and two temporal degrees of freedom was sufficient to convey full color information. The simulation results showed that the proposed method achieved acceptable color reproduction accuracy, average CIEDE2000 color difference (DeltaE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> ) < 3. The least number of fields particularly alleviated the demand for fast-response LC modes in sequential-type LCDs. Furthermore, color break-up suppression was observed due to less chrominance difference between the two fields.

P‐47: Hold‐Type Display Motion Blur Reduction with Spatial Compensation

AbstractMotion blur reduction technology becomes more and more important in LCD TV applications. Recently, black data insertion, scanning backlight, LED local dimming, and high frame rate driving with ME/MC are main technologies for motion blur reduction. Those technologies improve motion blur by reducing temporal integration time of human visual system. We proposed a novel method to reduce motion blur by mapping the designed optical waveform back to the spatial position on the display. By this proposed method, we can improve the motion picture response time without increasing frame rate and decreasing the luminance of display. By simple motion estimation (simply estimating the motion speed and direction) and mapping the designed optical waveform back to the spatial position, the complex computing hardware can be saved and the requirement for LC panel can be reduced.

A Field Sequential Color LCD Based on Color Fields Arrangement for Color Breakup and Flicker Reduction

The field sequential color (FSC) mechanism can effectively generate multi-primary color fields in temporal sequence to form a full-color image. Color breakup (CBU), however, has appeared intrinsically in conventional FSC displays to degrade visual qualities. A novel CBU suppression method, color fields arrangement (CFA), was proposed to eliminate the artifacts for FSC liquid crystal displays (LCDs). The modified order of consecutive color fields results in superimposed color images on a retina without CBU. Additionally, the 4-CFA method with a field rate of 240 Hz was found to avoid the flicker phenomenon on static images. The proposed method was successfully implemented on a 5.6-in optically compensated bend (OCB) LC panel. Our results confirm that the visibility of CBU artifacts can be reduced as the evaluation of dynamic and static models.

Adaptive LC/BL Feedback Control in Field Sequential Color LCD Technique for Color Breakup Minimization

A full-color image on field sequential color (FSC) displays is composed of color fields in temporal sequence. With the FSC mechanism, color filters of liquid crystal displays (LCDs) can be removed to heighten the light efficiency and lower the material cost. Color breakup (CBU), however, has appeared intrinsically to degrade visual qualities. A novel gray level determination of liquid crystal and backlight (LC/BL) was proposed to suppress the CBU artifact on FSC-LCDs. Based on the image content in each frame, a dominated color-mixed field was found to minimize the color difference between the CBU and original image. Additionally, the feedback algorithm for the adaptive LC/BL signals was developed and implemented on a 32-inch optically compensated bend (OCB) mode LC panel. According to the evaluation of experiments and observations, the proposed method has been demonstrated to greatly suppress CBU in LCD applications.

Transient‐current asymmetry in CSTN‐LCD panels

Abstract— Optical flicker is one of the artifacts of color STN‐LCDs and is related to the electrical asymmetry in LCD panels. The transient‐current asymmetry was observed to have a linear correlation with the internal DC offset of LC panels. The asymmetric cell structure of LC panels with a single topcoat layer leads to the asymmetry. The interface effect between different layers in an LC panel plays an important role in this phenomenon. Based on experiments, an improved RC network model was introduced to describe the mechanism.

32.2: The Improvement of In‐Cell Microretarder for Stereoscopic LCD Fabrication

AbstractA microretarder for stereoscopic display is a thin film consisting of horizontal or vertical stripes with alternating null and half‐wave phase retardation states. As to in‐cell microretarder, we improved the phase retardation performance and proceeded to integrate the stereoscopic LCD structure together. In our final goal, the in‐cell microretarder LC panel with ten pixels will be proposed and produced to verify display performance.

LED를 PLS 배열로 사용한 시역 형성 광학계가 없는 3차원 영상의 시역에 대한 연구

A two dimensional point light source array can replace both the viewing zone forming optics and the back light panel in the contact-type 3 dimensional imaging systems based on LC panels. This replacement can make the system structure of the 3 dimensional imaging systems no different from that of the conventional LCD and can reduce undesirable visual effects caused by the viewing zone forming optics. The problem with the point light source array is the visual quality deterioration of the system due to the non-ideal nature of the array.

ディスプレイ―ＩＤＷ’０７を中心に―視域拡大法を適用させたインテグラルフォトグラフィーホログラム変換を用いた実写入力電子ホログラフィ

This paper describes electronic holography that can record and reconstruct real objects. Images of objects were captured by integral photography (IP) . Object beams were obtained from the captured images by simulating an IP reconstructed optical system. The beam reproduced by IP with a wide viewing zone was divided horizontally into three ranges in the direction of propagation, and each beam was recorded in a separate hologram. In holographic reconstruction, three holograms were displayed in another liquid crystal panel with a pixel pitch of 6.8 μm and 4096 (horizontal) ×2400 (vertical) pixels and illuminated by a He-Ne laser. The horizontal viewing zone was enlarged by combining each reconstructed beam from LC panels, and three-dimensional holographic images of real, moving objects could be seen with both eyes at a distance of 40 cm.

P‐66: Analysis and Reduction of Moiré in Two‐Layered 3D Display

AbstractSimulator for moiré in two‐layered 3D displays has been developed and moiré reduction has been investigated. Attachment of lens‐array to a front surface of a rear LC panel is one of good solutions for moiré reduction, while suppressing the deterioration of contrast and brightness of rear panel picture.

Dynamic gamma: Application to LCD motion-blur reduction

— A metric, “dynamic gamma,” to quantitatively evaluate the dynamic temporal response of an LCD device is proposed. Dynamic gamma, associated with 2-D plots, is more suitable for quantitatively characterizing the dynamic characteristics of an LC panel. The dynamic gamma metric was applied to improve the temporal response of LCDs. From dynamic gamma data, overdrive tables can be derived. Dynamic gamma can also be used to evaluate the effectiveness of overdrive. With a second-order dynamic gamma, the performance of different overdrive algorithms can be quantitatively assessed. The dynamic gamma metric was also applied to backlight flashing and developed a time adaptive overdrive algorithm. The new algorithm reduces the ghosting artifact due to the timing mismatch between LCD driving and backlight flashing. Experimental results from a simulated tracking camera confirms the advantages of the new algorithm designed using dynamic gamma.

32.3: New Peeping Prevention Technology to Control Viewing Angle Properties of TFT-LCDs

New peeping prevention technology to control the viewing angle properties of TFT-LCDs has been developed. This technology can be applied to all kinds of LCDs, especially to the ones for PCs, cellular phones, ATMs and so on. In this technology, an additional LC panel in which the whole area is divided into two kinds of small visible domains of different LC alignment directions is used. The products, named VAC Filter™ or VACF™, have been put on sale in 2003 and have been applied to TOSHIBA TECRA M3 and so on.

P-237: Micro-Structure Optical Film with Hybrid Functions for LCD Backlight

To satisfy the high quality requirements of LCD optical films such as diffusers, prism sheets, and DBEF are assembled in backlight module to provide uniform and bright lighting conditions for LC panel. Integrating functions of these laminated optical films to reduce amount of films in current module has been a technical trend in LCD industry. We proposed a novel hybrid optical film (HOF) with micro-structure on its surface simultaneously reveals high uniformity, high brightness, and high light efficiency while it's assembled in backlight module.

Luminance addition of a stack of multidomain liquid-crystal displays and capability for depth-fused three-dimensional display application

A stack of liquid-crystal displays is expected to reduce visual fatigue caused by a flat-panel three-dimensional (3D) display. We previously developed a compact depth-fused 3D (DFD) display by using a stack of two twisted-nematic (liquid-crystal) LC panels, but its viewing-angle characteristics and color reproducibility were not so good. Therefore recent wide-view LC panels should be used. We report calculated and measured luminance addition characteristics, which are essential for evaluating 3D display characteristics, of a stack of two multidomain LC panels. We found that LC panels with super in-plane switching, patterned vertical alignment, multiple vertical alignment, and continuous pinwheel alignment modes are suitable for DFD display application.

Double-faced TFT-LCD having one LC panel and one lighting system

— We have developed a novel liquid-crystal-display (LCD) system referred to as a “Double-Faced LCD.” It has only one LC panel and one lighting system, but it works not only as a transmissive-type LCD from one side but also as a reflective-type LCD from the other side. Therefore, the thickness and the weight of the Double-Faced LCD can be reduced compared to those of conventional LC modules that have two LC panels and two lighting systems.

P-50: Dynamic Gamma: Applications to Improve LCD Temporal Response using Overdrive

In our previous papers, we proposed a metric “dynamic gamma” to quantitatively evaluate the dynamic temporal response of an LC display device. Dynamic gamma, associated with 2-D plots, is arguably more suitable for quantitatively characterizing the dynamic characteristics of an LC panel. In this paper, we apply the dynamic gamma metric to improve the temporal response of LCD. From dynamic gamma data, overdrive table can be derived. It can also evaluate the quality of overdrive. With the second order dynamic, we can even assess the performance of different overdrive algorithms. Test result confirms that dynamic gamma is not only a good metric for LCD panel, but also for overdrive algorithm evaluation.

17.4: Novel Liquid‐Crystal Materials with High Birefringence and Low Rotational‐Viscosity for the Field‐Sequential Color TN‐LCDs

AbstractLiquid crystal (LC) materials with features of coexistence of high birefringence and low rotational‐viscosity were developed, by introducing novel class of tolane substances. Those LC mixtures exhibit voltage‐holding‐ratio high enough for active matrix addressing, and their excellent physical properties improve the TN‐mode display performances significantly. The extremely fast switching characteristics enable TN LC panels to be applicable to field sequential color displays.

イメージスプリッタ方式メガネなし２Ｄ／３Ｄディスプレイの開発

We have developed a 2-D/3-D compatible display without special glasses. We set the image-splitter between the LC panel and the backlight in order to achieve the 3-D images without special glasses. We set a controllable scattering shutter between the LC panel and the backlight in order to display not only 3-D images without special glasses but also normal 2-D images without losing the resolution of the LC panel. By controlling both the image and the special shutter, a 3-D image and a 2-D image can be created in any rectangle groups of 16 rectangles on the screen. A 2-D image can also be viewed without losing resolution. Furthermore, this display has a 3-D indicator to make it easier to find the proper viewing area without the special glasses. We applied these technologies to a 3-D system on the Internet.

Particle Generation by Solid-Lubricated Bearings and Ball Screws in Vacuum Environments©

Rolling bearings used for transporting wafers and liquid crystals in the film-forming process of semiconductor and LC panel manufacturing are required to minimize the particles (originating from both lubricant and bearing material) they generate while in operation. The research reported in this paper focuses on the particle generation under different rotational conditions of ball bearings and ball screws coated with various solid lubricants and operating in a vacuum environment. The results of the tests indicated that a specially composed and applied polytetrafluoroethylene (PTFE) coating was superior in minimizing particle generation by ball bearings and ball screws. Observation of the bearing interior surfaces indicated that particle generation is primarily caused by wear of cage-pocket surfaces, while sudden and large increases in wear are the result of the balls making direct surface-to-surface contact with the raceways and cages due to erosion of the solid lubricant coatings. Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

Improvement of image quality of liquid crystal projection system by a diffractive gratings

AbstractA new depixelization technique using diffractive gratings to suppress the “discrete” nature of liquid crystal projection image is described. The diffractive gratings transform light emitting from each pixel of an LC panel into mainly 0‐th and 1‐st diffraction order light beams of the equal energy. By deflecting the 1‐st order beams horizontally to 3/2 amount of sub‐color pixels to fill the dead space between each pixel, thus doubling the number of pixels within the image, the image quality of the LCD projection is improved.

ディスプレイ イメージスプリッタ方式メガネなし３Ｄディスプレイ

We have improved our original image-splitter technology and developed new higher-performance autostereoscopic displays. The image-splitter is set between the LC panel and the backlight. In this new type, the backlight side of the image-splitter is made of reflective material and makes the lighting efficiency about 1.4 times that of the parallax barrier. Next we have developed a double image-splitter technology in which an image-splitter is set on each side of the LC panel. And by optimizing the arerture ratio of the image-splitters, we were able to create a moire-less autostereoscopic display and a autospereoscopic display with minimal crosstalk. These new autostereoscopic displays satisfy the demanding requirements of entertainment and medical use and will be suitable for many new applications.