Transmission and reflection dual operational mode MEMS display device

A novel MEMS display device comprising a light separator and MEMS light shutters is introduced. This device is operable both in transmissive mode using internal light source and in reflective mode using external sun light. In transmissive mode, the light separator directs internal backlight illuminated on its incident surface into a plural of small openings (grooves) on the viewing surface. The MEMS light shutters are used to control the color and intensity of light at individual pixels. Internal light utilization efficiency of this display is the greatest compared to any other transmissive displays. The device is capable of having true black background, hence a very high contrast ratio. In reflective mode, MEMS shutters direct part of the sun light for image display. MEMS shutters have fast response time, making the new device suitable for vivid motion picture display, and operable at very low voltages, suitable for mobile device applications.     

Large-display developments in China

In China, various kinds of displays have been developed in recent years. Normal displays, i.e. on-off type displays such as LED and electromagnetic displays, have been used in many places. These have formed the main display modes in China. Another significant development has been the appearance of giant video displays. The first system has been installed in Xiannongtan Stadium in Beijing. It was used during the opening ceremony of the First Farmer Games of the People's Republic of China, and is intended for further use at the 11th Asian Games to be held in 1990.     

Optical performance characterization of flexible mobile displays

The high interest in the display industry to produce curved or flexible displays for mobile, wearable, and television markets has raised concerns on the performance of displays in their bent state. Flexible display technologies have been developed for this purpose, but their optical characteristics have not been previously reported at various degrees of curvature. The measurement of flexible displays is possible only with special measurement arrangements using common display characterization devices. A conoscope with a working distance of 15 mm was used to demonstrate the curvature dependence of luminance, viewing angle, and color coordinates of the white point of a flexible active‐matrix organic light‐emitting display. The results show that the effect of curvature on the optical characteristics of the display is most evident at the smallest measured bending radii of +/?50 mm and that the effects are most visible when viewing the bent ends of the display, from the central normal vantage point, with uniform curvature along the display.     

Super multi-view and holographic displays using MEMS devices

Holographic displays and super multi-view (SMV) displays have been developed to solve the accommodation–vergence conflict that is responsible for visual fatigue caused by the 3D images that are generated by conventional three-dimensional (3D) displays upon which the eye cannot focus. However, holographic and SMV displays provide 3D images upon which the eye can readily focus so that the accommodation–vergence conflict does not occur. Because these two display techniques require the generation of a very large amount of image data, the high data bandwidth of microelectromechanical (MEMS) devices is effectively utilized. The present article describes the holographic display system that employs a MEMS spatial light modulator (SLM), which increases the screen size and viewing zone angle. Two SMV displays are also described, where one employs MEMS SLMs and the other an array of MEMS projectors. The resolution and the number of viewpoints of the SMV displays have increased. Moreover, the technique using a MEMS SLM to eliminate speckles from holographic reconstructed images is also described.     

Improved gray‐scale monochrome and color AMEL displays using analog pixel

Abstract— Active‐matrix electroluminescent (AMEL) microdisplays have been known for their numerous beneficial characteristics such as low weight, compactness, high brightness, and high contrast ratio. Beside these desirable characteristics, some of their drawbacks include difficulty in obtaining a high number of gray‐scale levels or a large number of colors, and interface‐electronics complexity. To address these drawbacks, AMEL displays using an analog addressing architecture have been developed. Utilizing this new driving scheme, 256 monochrome levels or 16 million colors are obtainable. Gray shade is proportional to an analog voltage stored on the hold node of each pixel. For color displays, each pixel is comprised of red, green, and blue subpixels arranged in vertical stripes, and can be sized independently to achieve the appropriate white balance. With the integration of control‐signal circuit blocks on the same substrate as the microdisplay, the number of input control signals is minimized and the display can be driven with very simple interface electronics. This results in low overall system cost, compact electronic packaging, and low power consumption. To accommodate most optical orientations, the display has built‐in modes to flip the image both vertically and horizontally. Additionally, the display supports multiple interlace addressing modes.     

Raster graphics display technology: a review

Performance and technologies of monochrome and polychromatic raster CRT visual display units are reviewed. For computer graphics, image quality is affected most by parameters such as size, resolution, luminance, contrast ratio, geometric distortion, flicker and video bandwidth. For polychromatic displays, chromaticity and convergence are also important parameters. Comparisons of 480 mm VDUs show that monochrome untis are less expensive and have better performance except for the use of colour to discriminate between different entities on the screen. Some typical graphics processor output head architectures are reviewed together with trends in display technology.     

3‐D displays — Technologies and testing methods

Abstract— This paper is a review of stereoscopic 3‐D display technologies and testing methods. The first part addresses the different 3‐D displays with focus on technologies. It gives both a background and the logic to group the technologies into categories. A family‐tree chartsummarizes the technology map. This categorization allows for logical grouping of test methods. The second part is a summary of testing procedures developed as part of the ICDM (International Committee for Display Metrology) standards group, affiliated with SID (Society of Information Display). Definitions to key test parameters pertinent to the evaluation of stereoscopic 3‐D displays including formulae development will be presented. This review paper can serve as an introduction to the 3‐D & Stereoscopic Displays chapter of the IDMS (Information Display Measurement Standard) version 1.0 that will be issued by the ICDM group later this year. The IDMS v1.0 will be the successor of the FPDM‐2 from VESA.     

Towards nanoscale molecular switch-based liquid crystal displays

Cholesteric liquid crystals (Ch-LCs) have been extensively studied due to their unique self-organized helical molecular structures and selective Bragg reflection properties, which exhibit great potentials for color displays and other practical applications. When functional, nanoscale molecular switches are doped in liquid crystals (LCs), the phases of the LCs or the molecular structures of the Ch-LCs can be changed upon the influence of external stimuli, such as light and temperature. In this paper, the photoresponsive molecular switch-based LCs for display applications are reviewed. The progress and effort in developing molecular switches, the principles of light-tuning, photo-addressed color displays, information processing, bistable displays and flexible displays are presented.     

Evaluation of true 3 D display systems for visualizing medical volume data

The last few years have witnessed extraordinary advances in medical imaging. The new digital methods, such as CT or MRI, share the common characteristic of providing three-dimensional volume data. The urgent need for efficient techniques for visualizing volume data has recently been recognized not only in diagnostic medicine, but also in computer-assisted surgery and radiation-therapy planning. In recent years, new display technologies have emerged, in which depth perception has been improved significantly, because it relies in principle on physiological depth cues. This paper presents the state-of-theart is true 3D displays (with a special emphasis placed on equipment that has reached relative maturity) and a discussion of their most important advantages and disadvantages with respect to visualizing medical data.     

MEMS-based tactile displays

This paper discusses state-of-the-art tactile displays fabricated by a micro-electronic-mechanical-system (MEMS). A tactile display conveys tactile sensations to users by using actuators. Traditional tactile displays consist of large size actuators, such as a motor or an ultrasound vibrator, to convey tactile feedback by vibration. In addition, the tactile sensation of traditional displays has poor resolution. Microelectromechanical system (MEMS) technology, which is a miniature fabrication process, enables etching, sputtering and assembling of miniature structures. Recently, the technology was applied to tactile displays. For example, shape memory alloy (SMA) actuators are widely used in tactile displays to convey roughness or vibration. The actuators are fabricated by a sputtering process and then thinned. The displays convey various tactile sensations, including feedback and tactile sensations of objects such as paper or wood. This paper is a review of tactile displays fabricated by MEMS technology. We also describe the fabrication processes and stimulation methods to present the potential and applications of the displays.     

Psychophysical research on switching between light emitting and reflecting modes of light adaptable display considering equal visibility

Viewing high-luminance displays such as liquid crystal displays or organic light emitting diode displays under low-light conditions causes an unbearable glare, while viewing them with low luminance under bright-light conditions reduces visibility. Recently, several research groups have reported light adaptable displays (LADs) to extend display visibility over a wide range of light conditions. Here, we present a psychophysical study on how to effectively utilize the LAD using two different display types for the first time. LAD features two switchable display types: light emitting mode (LEM) and light reflecting mode (LRM). To maintain visibility and prevent visual artifacts, we investigate when to switch modes between LEM and LRM. We conduct psychophysical experiments involving seventy subjects. They are asked to select illuminance levels under which they perceive that the LEM and LRM look the same depending on luminance of the LEM. We propose a mode-switching condition by combining our previous results on the comfortable luminance of LEM display according to the ambient illuminance and the selected illuminance results providing equal visibility of both LEM and LRM displays.     

EL displays for automotive applications

Abstract— This paper presents an overview of the display requirements for automotive applications and introduces alternating‐current thin‐film electroluminesent (ACTFEL) displays for automobiles. An ACTFEL has advantages over other displays under sunlight and low temperature conditions. Several automotive applications for transparent and multicolor EL displays are introduced in this paper.     

Reduced cross‐talk in shutter‐glass‐based stereoscopic LCD

Abstract— It is expected that 3‐D will be the next step in the enhanced viewing experience. At present, there are two competing 3‐D technologies for glasses‐based consumer TVs: active shutter glasses and passive polarized glasses. With the ongoing reduction in response time of liquid‐crystal displays (LCDs), this article will focus on shutter‐glass‐based stereoscopic LCDs. In this paper, the properties of such a display system is described and it is demonstrated that by adding a line‐scanning backlight, the cross‐talk can be reduced to less than 1.4%, allowing for excellent 3‐D portrayal. For images of extreme contrast, this is perceivable, but not judged annoying by a panel of expert viewers. Which characteristics of the display and shutter glasses that should be optimized to create an inexpensive, cross‐talk‐free, 3‐D LCD are discussed.     

Thin film electroluminescent displays produced by atomic layers

Electroluminescence (EL), light emission generated by an electric field in solid state, has been known as a phenomenon since 1936. Quite a lot of research and development has resultedin the establishment of the principle of thin film electroluminescent (TFEL) structures enabling display devices of good performance and simple structure to be built. The reasons for their non-availability in practice are mainly based on deficiencies in the existing material technologies. This paper reports the development of a new method for producing thin films, atomic layer epitaxy (ALE), which is now used in the Finlux EL displays.     

Front glass thickness requirements for high resolution polarized stereoscopic displays: A simulation platform

The tendency of the display market is towards displays with higher resolutions. Therefore, patterned retarder‐based stereoscopic displays require smaller front glass thickness to maintain good vertical viewing angle and limited crosstalk. To properly design these stereoscopic displays and quantify these requirements, we developed a simulation platform to predict radiance, polarization profile, and crosstalk over viewing angles and over wavelengths. Tunable parameters such as the distance between the pixels and the patterned retarder, and the optical properties of the patterned retarder are included. The simulation platform has been validated by comparing outcomes of simulations with measurements. We predict crosstalk accounting for both the human eye field of view and the diameter of the pupil. We found that to obtain a vertical viewing angle of at least ± 30° and crosstalk of at most 0.11 for a display with a pixel pitch beyond 0.27 mm, the display should include black absorbers, and the thickness of the front glass should be at most 0.5 mm. For higher resolution displays (pixel pitch no more than 0.21 mm), a front glass thickness at most 0.15 mm is required to produce a vertical viewing angle beyond ± 14° and a minimum viewing distance of 0.3 m.     

Substrate‐free cholesteric liquid‐crystal displays

Abstract— This paper demonstrates the first substrate‐free cholesteric liquid‐crystal displays. The encapsulated cholesteric displays are ultra‐thin (with a total thickness around 20 μm) and ultra‐lightweight (0.002 g/cm²). The displays exhibit unprecedented conformability, flexibility, and drapability while maintaining electro‐optical performance and mechanical integrity. All functional display layers are sequentially coated on a preparation substrate and then lifted‐off from the preparation substrate to form a free‐standing display. The display fabrication process, electro‐optical performance, and display flexibility are discussed.     

High-performance MEMS shutter display with metal-oxide thin-film transistors and optimized MEMS element

Active matrix prestressed microelectromechanical shutter displays enable outstanding optical properties as well as robust operating performance. The microelectromechanical systems (MEMS) shutter elements have been optimized for higher light outcoupling efficiency with lower operation voltage and higher pixel density. The MEMS elements have been co-fabricated with self-aligned metal-oxide thin-film transistors (TFTs). Several optimizations were required to integrate MEMS process without hampering the performance of both elements. The optimized display process requires only seven photolithographic masks with ensuring proper compatibility between MEMS shutter and metal-oxide TFT process.     

Conformable displays based on polymer‐dispersed liquid‐crystal materials on flexible substrates

Abstract— We have developed a process that enables one to conform polymer‐dispersed liquid‐crystal (PDLC) displays into a particular shape indefinitely. Planar PDLC displays are first fabricated between indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates. This fully functional display can then be conformed to a particular shape by heating above the glass‐transition temperature of PET and then allowing it to cool down to room temperature. The display retains its shape and is fully functional after processing. We have created spiral‐and wave‐like samples and have demonstrated their operation after the conformal process. The stress is relieved in the substrate by conforming. Temperature effects on polymer substrates were investigated for two types of polymer films (PET/ITO substrates and a conducting polymer PEDOT:PSS/PET substrate) to analyze the effects of temperature on the resistance and mechanics of the films under an applied uniaxial strain. We have found a decrease in contrast of the PDLC after conforming, but surprisingly, a reduced threshold voltage and reduced hysterisis occurs.     

Medical displays in the healthcare system

Abstract— As the healthcare system changes and progresses, the need for different types of high‐performing displays is also evolving. There are three categories of displays: (a) embedded (as part of life saving devices), (b) informative (for patient data and history, and managing workflow), and (c) imaging (high performing for diagnosis). The challenges of AMLCDs, which are the display of choice at the moment mainly in digital imaging, will be discussed. These challenges include very high resolution, high brightness, and wide viewing angle. The current performance of AMLCDs and the areas which they need to improve will be reviewed. A brief summary of the standards used to specify medical (diagnostic) displays will follow. A look into the future will predict the role of displays in hospitals.     

Advances towards high‐resolution pack‐and‐go displays: A survey

Abstract— Tiled displays provide high resolution and large scale simultaneously. Projectors can project on any available surface. Thus, it is possible to create a large high‐resolution display by simply tiling multiple projectors on any available regular surface. The tremendous advancement in projection technology has made projectors portable and affordable. One can envision displays made of multiple such projectors that can be packed in one's car trunk, carried from one location to another, deployed at each location easily to create a seamless high‐resolution display, and, finally, dismantled in minutes to be taken to the next location — essentially a pack‐and‐go display. Several challenges must be overcome in order to realize such pack‐and‐go displays. These include allowing for imperfect uncalibrated devices, uneven non‐diffused display surfaces, and a layman user via complete automation in deployment that requires no user invention. We described the advances we have made in addressing these challenges for the most common case of planar display surfaces. First, we present a technique to allow imperfect projectors. Next, we present a technique to allow a photometrically uncalibrated camera. Finally, we present a novel distributed architecture that renders critical display capabilities such as self‐calibration, scalability, and reconfigurability without any user intervention. These advances are important milestones towards the development of easy‐to‐use multi‐projector displays that can be deployed anywhere and by anyone.