Liquid Crystal Panel Research Articles

Virtual image display as a backlight for 3D

We describe a device which has the potential to be used both as a virtual image display and as a backlight. The pupil of the emitted light fills the device approximately to its periphery and the collimated emission can be scanned both horizontally and vertically in the manner needed to illuminate an eye in any position. The aim is to reduce the power needed to illuminate a liquid crystal panel but also to enable a smooth transition from 3D to a virtual image as the user nears the screen.

Integral three-dimensional image capture equipment with closely positioned lens array and image sensor

We have developed a compact integral three-dimensional (3D) imaging equipment that positions the lens array and image sensor in close proximity to each other. In the conventional scheme, a camera lens is used to project the elemental images generated by the lens array onto the image sensor. In contrast, the imaging equipment presented here combines the lens array and image sensor into one unit and makes no use of a camera lens. This scheme eliminates the resolution deterioration and distortion caused by the use of a camera lens and improves, in principle, the quality of the reconstructed 3D image. We captured objects with this imaging equipment and displayed the reconstructed 3D images using display equipment consisting of a liquid crystal panel and a lens array. The reconstructed 3D images were found to have appropriate motion parallax.

Magnetic Separation System for Recovery of Glass Polishing Agent

The polishing agent, mainly composed of cerium oxide (CeO2), is used for fine polishing of products such as liquid crystal panels. The impurities of iron oxide, silica, and alumina get mixed in the cerium oxide-based polishing waste water. In order to reuse the polishing agent, it is necessary to remove these impurities. In this study, the impurities were removed utilizing the difference of magnetic susceptibility in order to recover the polishing agent. In our previous study, we proposed a technique to recover cerium oxide in high purity. In the first stage, iron oxide was removed from the polishing waste water by high-gradient magnetic separation. In the second stage, silica and alumina were removed by magneto-Archimedes method utilizing the magnetic force in vertical direction. In this study, we proposed a magnetic separation method utilizing the magnetic force in horizontal direction, and examined the application possibility of the method for continuous processing in practical use.

Can Sharp become the new liquid crystal panel IGZO leader? Observations from patent information analysis

This research focuses on the patent applications in the field of IGZO liquid crystal panel business. The ‘IGZO’ is a new challenging material for liquid crystal polymer (LCP). We compared and analysed patent information of nine Japanese applicants and one foreign applicant, by using bibliographic data, examination processes, registration data, overseas application, technical classification, citation data, etc., clarifying Sharp’s strength and weakness in the field of IGZO LCP business. We evaluated the strength and weakness together with patent strategy of companies, by using various approaches of patent information analysis. We reached the conclusion that Sharp has advantages against other competitors in the field of IGZO patent acquisitions because of its high registration ratio and few refusal notifications from Japan Patent Office.

Investigation of Liquid Crystal Ripple Using Ericksen-Leslie Theory for Displays Subject to Tactile Force

Liquid crystal display panels subjected to tactile force will show ripple propagation on screens. Tactile forces change tilt angles of liquid crystal molecules and alter optical transmission so as to generate ripple on screens. Based on the Ericksen-Leslie theory, this study investigates ripple propagation by dealing with tilt angles of liquid crystal molecules. Tactile force effects are taken into account to derive the molecule equation of motion for liquid crystals. Analytical results show that viscosity, tactile force, the thickness of cell gap, and Leslie viscosity coefficient lead to tilt angle variation. Tilt angle variations of PAA liquid crystal molecules are sensitive to tactile force magnitudes, while those of 5CB and MBBA with larger viscosity are not. Analytical derivation is validated by numerical results.

Polarimetric Measurement of Jones Matrix of a Twisted Nematic Liquid Crystal Spatial Light Modulator

A polarimetric experimental method was developed to determine the Jones matrix elements of transparent optical materials without sign ambiguity. A set of polarization dependent transmittance data of the samples was measured with polarizer - sample - analyzer system and another set of data was measured with polarizer - sample - quarter-wave plate - analyzer. Two data sets were compared and mathematically analyzed to obtain the correct signs of the elements of the matrix. The Jones matrix elements of a quarter-wave plate were determined to check the validity of the method. The experimentally obtained matrix elements of the quarter-wave plate were consistent with the theoretical expectations. The same method was applied to obtain the Jones matrix elements of a twisted nematic liquid crystal panel.

The order fulfillment planning problem considering multi-site order allocation and single-site shop floor scheduling

The order fulfillment planning process in the thin film transistor---liquid crystal display panel industry is analyzed in this study. A two-phase order fulfillment planning structure is proposed, including the multi-site order allocation among module factories and single-site shop floor scheduling in each factory. In the first phase, the order allocation problem is solved using a mathematical programming model considering practical characteristics, including product structures, customer preferences, alternative bill-of-material, and production constraints. In the second phase, a constraint-based simulation scheduling algorithm is developed to address the scheduling problem in each module factory for determining the ideal order release time. Since production planning and scheduling are dealt with different time scales, the major challenge for the integration lies in the large problem size of the optimization model and becomes intractable. Most of the time bucket-based planning methods in the past literature simplify their scheduling models, but in this paper the detailed shop floor operations and processing behaviors are considered, such as changeover time, processing sequence of orders, and machine characteristics. Finally, a practical case in Taiwan will be employed to testify the feasibility of the proposed order fulfillment planning process; meanwhile, through the analysis of experiments, the adaptability and comparison of different planning approaches in an environment of various market demands are discussed.

Power management of direct-view LED backlight for liquid crystal display

In this paper, we present a study of management of power in function of luminous efficacy of white LED as well as the efficiency enhancement of the direct-view backlight with photon recycling. A cavity efficiency as high as 90.7% is demonstrated for a direct-view backlight with photon recycling. In the future, with a 90% backlight cavity, luminous efficacy of 200lm/W for white LEDs, and a transmission efficiency of 10% for the liquid crystal panel, the required power of LEDs could be only 16W. Up to 85% energy saving could be achieved in comparison to the power of the current liquid crystal display.

59.1: A Volumetric Display Using a Rim‐Driven Varifocal Beamsplitter and High‐Speed DLP Backlit LCD

AbstractWe present a high resolution, full color, volumetric display. The display utilizes a novel optical element: the large‐aperture, rim‐driven, adjustable‐resonance, varifocal beamsplitter. The display generates volumetric real images with pixel addressable depth planes. The primary image generator is an RGB liquid crystal panel backlit by a highspeed video projector.

72.2: Compact and High Efficiency Head‐Up Display for Vehicle Application

AbstractA head up display using 7 inches TFT liquid crystal panel and 13 white light LEDs has been proposed, in which a lens array illumination optics direct the illumination light toward the eye box of the driver so that energy utilization is highly effective. Due to the direct illumination configuration, the thickness of the whole HUD module is 80 mm.

Novel exposure system using light-emitting diodes and an optical fiber array for printing code marks

The feasibility of a novel economical and environmentally friendly exposure system using a light-emitting diode (LED) array as a light source was demonstrated. Such an exposure system is especially useful for printing two-dimensional code marks for the production management of semiconductor devices and liquid crystal display panels. The new system also uses an optical fiber matrix array connected to the LED array. The tips of the plastic optical fibers of 1mm diameter are heated and deformed into a square shape, and the square fiber ends are projected by a 1/10 reduction lens. Using LEDs with a central wavelength of 405 nm and an output power of 40mW/cm2, quasi-square code mark patterns are printed with good size repeatability in a practically feasible short time of less than 2 s.

Application of the Taguchi approach to improve performance of the alignment-layer printing process in liquid crystal displays

The uniformity of the alignment-layer thickness on indium tin oxide glass plays an important role in producing liquid crystal display panels of quality images. However, thickness non-uniformity results in producing liquid crystal display panel of poor color image, which increases rework cost and scrap. The Taguchi method is utilized in the define–measure–analyze–improve–control approach to improve the capability of this process. In the define phase, process mapping and quality characteristic definition are discussed. The x̄ and R control charts and process capability analysis are employed in the measure phase. The L18 array and signal-to-noise ratio, followed by analysis of variance, are utilized in the analyze phase. In the improve phase, two-step optimization is conducted to reduce thickness variations and adjust process mean on target. The control charts for the thickness are regularly constructed in the control phase. Initially, the estimates of the capability indices for the alignment-layer printing process are 0.731 and 0.69, respectively, which indicate that this process is incapable. Utilizing the Taguchi method, confirmation experiments showed that the potential and actual capability indices are respectively improved to 3.48 and 3.47. Hence, the process becomes highly capable. This proves the effectiveness of the Taguchi method in improving the performance of the alignment-layer printing process.

Polarization fields

We introduce polarization field displays as an optically-efficient design for dynamic light field display using multi-layered LCDs. Such displays consist of a stacked set of liquid crystal panels with a single pair of crossed linear polarizers. Each layer is modeled as a spatially-controllable polarization rotator, as opposed to a conventional spatial light modulator that directly attenuates light. Color display is achieved using field sequential color illumination with monochromatic LCDs, mitigating severe attenuation and moiré occurring with layered color filter arrays. We demonstrate such displays can be controlled, at interactive refresh rates, by adopting the SART algorithm to tomographically solve for the optimal spatially-varying polarization state rotations applied by each layer. We validate our design by constructing a prototype using modified off-the-shelf panels. We demonstrate interactive display using a GPU-based SART implementation supporting both polarization-based and attenuation-based architectures. Experiments characterize the accuracy of our image formation model, verifying polarization field displays achieve increased brightness, higher resolution, and extended depth of field, as compared to existing automultiscopic display methods for dual-layer and multi-layer LCDs.

Two‐parallax‐barriers‐based autostereoscopic liquid‐crystal display without cross‐talk

Abstract— An autostereoscopic liquid‐crystal display (LCD) consists of two parallax barriers and an LCD including a liquid‐crystal panel, and a backlight panel is proposed. Parallax barrier 1 is located between the backlight panel and the liquid‐crystal panel, and Parallax barrier 2 is located between the liquid‐crystal panel and viewers. The operation principle of the autostereoscopic display and the calculation equations for the parallax barriers are described in detail. The autostereoscopic LCD was developed and produces high‐quality stereoscopic images without cross‐talk at the optimal viewing distance and less cross‐talk than a conventional one based on one parallax barrier at other viewing distances.

English

The thin film transistor liquid crystal display (TFT-LCD) including three fundamental process stages: array process, cell process and module process is generally called liquid crystal panel by consumers. Each process stage existing the variable manufacturing flow-process and characteristic of capacity results in acquiring individual objective in each plant, however, ignoring the demand in entire supply chain. For instance, array process and cell process enthusiastically pursue to reach maximal throughput contributed to have much more work in process (WIP) of the panel to Module process. However, the module process depends on the demand of final customers to assemble finished products. Therefore, the demand of customers and the supply from the upstream process exists asymmetrically to lead the inventory levels ineffectively for controlling. The theory of constraints supply chain replenishment system (TOC-SCRS) is supposed to apply the TFT-LCD plants, and is mainly discussed the inventory of TFT-LCD in each plant to study this model of replenishment. The inventory of TFT-LCD in each plant has three critical parameters: frequency of replenishment (FR), reliable replenishment time (RRT) and maximum inventory buffer. Furthermore, utilizing FR, RRT, and maximum inventory buffer parameters to calculate the replenishment quantity and delivery quantity. However, each inventory is related to each other between upstream and downstream. This study is concerned with TOC-SCRS to each inventory and uses the simulation model to simulate the variation of the each inventory to demonstrate the significance and feasibility of this proposed TOC-SCRS for TFT-LCD plants.   Key words: Thin film transistor liquid crystal display, theory of constraints, supply chain management, TOC supply chain replenishment system.          

Design of a symmetric blazed grating sheet embedded in an autostereoscopic display

This study proposes a diffractive autostereoscopic display technology that utilizes blazed grating embedded in the liquid crystal panel to deliver a stereo image pair to both eyes. Having the diffractive red green blue beams as the color source of the panel, color filters are no longer required in this system. From the simulation analyses, not only could the brightness achieve 77.90%, but no serious chromatic aberration or cross talk appeared.

Single panel liquid crystal device switchable between reflective and transmissive modes

We propose a single panel liquid crystal (LC) device that is switchable between reflective and transmissive modes. Operation in the reflective mode can be achieved by applying a vertical field to a dye-doped LC device, whereas the device can be in-plane switched for operation in the transmissive mode. Image inversion that was inevitable in a single panel device using a reflective polarizer is effectively eliminated through the absorption of ambient light by the dye-doped LCs. We believe that the proposed device can be applied to various display systems for outdoor mobile use.

Novel input and output mapping-sensitive error back propagation learning algorithm for detecting small input feature variations

This paper proposes a new error back propagation learning algorithm that properly enhances the sensitivity of input and output mapping by applying a high-pass filter characteristic to the conventional error back propagation learning algorithm, allowing small input feature variations to be successfully indicated. For the sensitive discrimination of novel class data with slightly different characteristics from the normal class data, the cost function in the proposed neural network algorithm is modified by further increasing the input and output sensitivity, where weight update rules are used to minimize the cost function using a gradient descent method. The proposed algorithm is applied to an auto-associative multilayer perceptron neural network and its performance evaluated with two real-world applications: a laser spot detection-based computer interface system for detecting a laser spot in complex backgrounds and an automatic inspection system for the reliable detection of Mura defects that occur during the manufacture of flat panel liquid crystal displays. When compared with the conventional error back propagation learning algorithm, the proposed algorithm shows a better performance as regards detecting small input feature variations by increasing the input–output mapping sensitivity.

Stereogram implemented with a holographic image splitter

A special holographic optical element (HOE) which is used as an image splitter is developed to generate a stereogram on a 2.2-in. liquid crystal display panel. The special designed holographic optical element can be attached on the conventional panel directly to replace the traditional image splitter in a stereoscopic display panel. Experimental results show that two images corresponding to slightly different viewing angles displayed on a panel can be separated effectively and can be delivered to the right eye and left eye of an observer individually. The diffraction efficiency for individual right and left image in this developed holographic optical element is about 43%, and the contrast ratio of the diffracted images induced by cross talk is larger than 60%. Theoretical analyses show the proposed technique generates good contrast ratio and brightness performance for stereogram application.

Liquid crystals, photonic crystals, metamaterials, and transformation optics

Recent advances of modern optics have been made possible with the development of unique materials, most notably liquid crystals (LCs), photonic crystals (PCs), and metamaterials (MMs). LCs have already completed a revolution in the way we present information nowadays, enabling an entire industry of flat panel liquid crystal displays (LCDs). PCs (1) and MMs (2) are further behind in terms of broad commercialization, but the change they produce in our understanding of how matter can control light is no less revolutionary, fueling dreams that only recently were science fiction, such as subwavelength imaging and focusing, invisibility cloaking, black hole-like light trapping, and more. PCs and MMs are formed by building units of a size s intermediate between the molecular scale m = (1–3) nm and the optical wavelength λ and cannot be simply synthesized as small organic molecules that form LCs. Design, manufacturing, and control of properties of PCs and MMs at the scale m < s ≤ λ is the major challenge. There are a variety of ways by which the LCs can help in the development of PCs and MMs; one of the latest advances is presented in PNAS by Ravnik et al. (3).