Display Brightness Research Articles

알루미늄 도핑된 산화아연 양극을 적용한 고효율 유기발광다이오드

Properties of organic light-emitting diodes (OLEDs) with aluminum-doped zinc oxide (ZnO:Al) anodes showed different behaviors from OLEDs with indium tin oxide (ITO) anodes according to driving conditions. OLEDs with ITO anodes gave higher current density and luminance in lower voltage region and better EL and power efficiency under lower current density conditions, However, OLEDs with ZnO:Al anodes gave higher current density and luminance in higher voltage region over about 8V and better EL and power efficiency under higher current density over . These seemed to be due to the differences in conduction properties of semiconducting ZnO:Al and metallic ITO. OLEDs with ZnO:Al anodes showed nearly saturated efficiency under high current driving conditions compared with those of OLEDs with ITO anodes. This meant better charge balance in OLEDs with ZnO:Al anodes. These properties of OLEDs with ZnO:Al anodes are useful in making bright display devices with efficiency.

Gravity Probe B Photometry and Observations of ζ Pegasi: An SPB Variable Star

ABSTRACTThe Gravity Probe B (GP‐B) satellite photometric system and instrumentation are introduced. Observational results are presented for calibration stars demonstrating a single‐orbit relative photometric precision capability of 500 μmag for bright stars. Broadband photometric observations of the bright star ζ Pegasi are then presented that display brightness variability of 488.2 ± 6.6 μmag (parts per million), with a period of 22.952 ± 0.804 hr (f ≈ 1.04566 cycles day−1). Over the short observational period, the variation is monosinusoidal, thus recommending the star for membership in the class of small‐amplitude, slowly pulsating B (SPB) star variables oscillating in a nonradial g‐mode.

Ambient illumination revisited: A new adaptation‐based approach for optimizing medical imaging reading environments

Ambient lighting in soft-copy reading rooms is currently kept at low values to preserve contrast rendition in the dark regions of a medical image. Low illuminance levels, however, create inadequate viewing conditions and may also cause eye strain. This eye strain may be potentially attributed to notable variations in the luminance adaptation state of the reader's eyes when moving the gaze intermittently between the brighter display and darker surrounding surfaces. This paper presents a methodology to minimize this variation and optimize the lighting conditions of reading rooms by exploiting the properties of liquid crystal displays (LCDs) with low diffuse reflection coefficients and high luminance ratio. First, a computational model was developed to determine a global luminance adaptation value, Ladp, when viewing a medical image on display. The model is based on the diameter of the pupil size, which depends on the luminance of the observed object. Second, this value was compared with the luminance reflected off surrounding surfaces, Ls, under various conditions of room illuminance, E, different values of diffuse reflection coefficients of surrounding surfaces, Rs, and calibration settings of a typical LCD. The results suggest that for typical luminance settings of current LCDs, it is possible to raise ambient illumination to minimize differences in eye adaptation, potentially reducing visual fatigue while also complying with the TG18 specifications for controlled contrast rendition. Specifically, room illumination in the 75-150 lux range and surface diffuse reflection coefficients in the practical range of 0.13-0.22 sr(-1) provide an ideal setup for typical LCDs. Future LCDs with lower diffuse reflectivity and with higher inherent luminance ratios can provide further improvement of ergonomic viewing conditions in reading rooms.

Improvement of Hydrogenated Amorphous-Silicon TFT Performances With Low-$k$Siloxane-Based Hydrogen Silsesquioxane (HSQ) Passivation Layer

A low-dielectric-constant (low-k)-material siloxane-based hydrogen silsesquioxane (HSQ) is investigated as a passivation layer in bottom-gate hydrogenated amorphous-silicon thin-film transistors (a-Si : H TFTs). The low-k HSQ film passivated on TFT promotes the brightness and aperture ratio of TFT liquid-crystal display due to its high light transmittance and good planarization. In addition, the performance of a-Si : H TFT with HSQ passivation has been improved, compared to a conventional silicon nitride (SiNx)-passivated TFT because the hydrogen bonds of HSQ assist the hydrogen incorporation to eliminate the density of states between the back channel and passivation layer. Experimental results exhibit an improved field-effect mobility of 0.57 cm2/Vmiddots and a subthreshold swing of 0.68 V

Electro‐optical transfer function preferences for LCD TVs: The effect of display brightness and surround illumination on preferred gamma

Abstract— Recent commercial liquid‐crystal‐display (LCD) televisions are larger and brighter than traditional televisions, thus impacting the viewing conditions in which they are viewed. These changes in viewing conditions may require different electro‐optical transfer functions (EOTFs) for LCD TVs than those for conventional TVs. Here, the way various EOTFs affect the preferred image quality of test images with changes in brightness and surround illumination conditions are examined. The first method used a gain, offset, and gamma (GOG) function with a range of gamma values, and the second method altered the intrinsic EOTFs. Image preference for the simulated EOTFs was determined using a paired‐comparison experiment for ten images. The first experiment took place in a darkened room at two display luminance levels. The results indicated that a gamma of 1.6 was most preferred overall although more so at a lower screen luminance level. In a second experiment, the procedure was repeated with a dim surround of 10% of the display's white point. With this surround, preference for a gamma value of around 1.6 at both screen luminance levels was more enhanced. These results indicated that image preference for different EOTFs is dependent on display luminance and that this dependence is maintained with a dim surround.

Relaxation of Surface Stabilised Antiferroelectric Liquid Crystals at Video Frequency

As part of our line of research into high resolution, video rate antiferroelectric displays we have studied the ferroelectric – antiferroelectric relaxation that follows the data pulse, in surface stabilised antiferroelectric liquid crystal (AFLC) displays, driven by biasless or low bias video frequency waveforms. This generally incomplete relaxation reduces the intensity of the light transmitted by a pixel in any partially ferroelectric (grey-level) state during a video frame, and hence limits the frame-averaged brightness of the AFLC display. The relaxation is a function of the surface stabilisation (i.e., the anchoring strength, pre-tilt and thickness of the device and the pitch of the AFLC), the rotational viscosity of the AFLC, the degree of relaxation of the AFLC between successive frames, the magnitude of the data pulse (grey level) and bias voltage. We have optimised the driving scheme for a number of symmetric and asymmetric (biasless) displays with different antiferroelectric materials and a variety of alignment surfaces, and present mathematical fits to the decaying transparency during single frames as functions of the data pulse. Finally we discuss the mechanisms governing the relaxation.

Key design issues for autostereoscopic 2‐D/3‐D displays

Abstract— Flat‐panel 2‐D/3‐D autostereoscopic displays are now being commercialized in a variety of applications, each with its own particular requirements. The autostereoscopic display designer has two key considerations to address in order to meet customer needs — the optical output of the display (defined by the output window structure) and the choice of optical components. Window structure determines 3‐D image resolution, achievable lateral and longitudinal viewing freedom, crosstalk, and 3‐D fringe contrast. Optical‐component selection determines the quality of the imaging of such windows, viewing distances, device ruggedness, thickness, and brightness. Trade‐offs in window design are described, and a comparison of the leading optical component technologies is given. Selection of Polarisation Activated Microlenses™ architectures for LCD and OLED applications are described. The technology delivers significant advantages particularly for minimising nominal viewing distances in high pixel density panels and optimizing device ruggedness while maintaining display brightness.

Predation by sparrowhawks Accipiter nisus on male and female pied flycatchers Ficedula hypoleuca in relation to their breeding behaviour and foraging

Bright plumage, song display, and aggressive resource defence in males may cause higher predation on males than on females during the breeding season. However, in birds, higher predation on females is sometimes observed. Parental investment may be high in females (egg-laying, incubation and feeding of offspring), which might lead to a high risk of predation. We studied predation by sparrowhawks Accipiter nisus in relation to behaviour in pied flycatchers Ficedula hypoleuca where breeding males are more conspicuous than females in plumage and behaviour. Male pied flycatchers generally occupied more exposed perches than females. Females were more mobile and foraged more than males, especially prior to and during incubation. During the incubation and nestling stages, when predation on the sexes could be directly compared, sparrowhawks took about the same number of male and female pied flycatchers. During incubation, however, females spent about 77% of the day in the nest and were 4.7 times more vulnerable than males per unit of time available (i.e. outside the nest). A comparison with the chaffinch Fringilla coelebs, where hawks took more females than males, indicates that timing of breeding, foraging behaviour and parental roles of males and females affect predation risk.

P-239L: Late-News Poster: E-2D Advanced Hawkeye: Primary Flight Display

This paper is a response to the challenge of providing a large area avionics display for the E-2D AHE aircraft. The resulting display design provides a pilot with high-resolution visual information content covering an image area of almost three square feet (Active Area of Samsung display = 33.792cm × 27.0336 cm = 13.304″ × 10.643″ = 141.596 square inches = 0.983 sq. ft × 3 = 2.95 sq. ft). The avionics display application, design and performance being described is the Primary Flight Display for the E-2D Advanced Hawkeye aircraft. This cockpit display has a screen diagonal size of 17 inches. Three displays, with minimum bezel width, just fit within the available instrument panel area. The significant design constraints of supporting an upgrade installation have been addressed. These constraints include a display image size that is larger than the mounting opening in the instrument panel. This, therefore, requires that the Electromagnetic Interference (EMI) window, LCD panel and backlight all fit within the limited available bezel depth. High brightness and a wide dimming range are supported with a dual mode Cold Cathode Fluorescent Tube (CCFT) and LED backlight. Packaging constraints dictated the use of multiple U shaped fluorescent lamps in a direct view backlight design for a maximum display brightness of 300 foot-Lamberts. The low intensity backlight levels are provided by remote LEDs coupled through a fiber optic mesh. This architecture generates luminous uniformity within a minimum backlight depth. Cross-cockpit viewing is supported with ultra-wide field-of-view performance including contrast and the color stability of an advanced LCD cell design supports. Display system design tradeoffs directed a priority to high optical efficiency for minimum power and weight.

Effects of playing a computer game using a bright display on presleep physiological variables, sleep latency, slow wave sleep and REM sleep

Epidemiological studies have shown that playing a computer game at night delays bedtime and shortens sleeping hours, but the effects on sleep architecture and quality have remained unclear. In the present study, the effects of playing a computer game and using a bright display on nocturnal sleep were examined in a laboratory. Seven male adults (24.7+/-5.6 years old) played exciting computer games with a bright display (game-BD) and a dark display (game-DD) and performed simple tasks with low mental load as a control condition in front of a BD (control-BD) and DD (control-DD) between 23:00 and 1:45 hours in randomized order and then went to bed at 2:00 hours and slept until 8:00 hours. Rectal temperature, electroencephalogram (EEG), heart rate and subjective sleepiness were recorded before sleep and a polysomnogram was recorded during sleep. Heart rate was significantly higher after playing games than after the control conditions, and it was also significantly higher after using the BD than after using the DD. Subjective sleepiness and relative theta power of EEG were significantly lower after playing games than after the control conditions. Sleep latency was significantly longer after playing games than after the control conditions. REM sleep was significantly shorter after the playing games than after the control conditions. No significant effects of either computer games or BD were found on slow-wave sleep. These results suggest that playing an exciting computer game affects sleep latency and REM sleep but that a bright display does not affect sleep variables.

51.4: Invited Paper: Modelling and Design of Polysilicon Drive Circuits for OLED Displays

AbstractVoltage input pixel driver circuits for low‐temperature polysilicon thin‐film transistor active‐matrix organic light emitting diode displays have been designed to give uniform display brightness in the presence of spatial variation of threshold voltages. These pixel circuits are designed for a high‐resolution and fine‐grayscale display.

A Comparative Study of Reading Performance with a Head-mounted Laser Display and Conventional Low Vision Devices

This study compared the reading performance of subjects using a prototype, head-mounted laser display, a closed-circuit television (CCTV), and a prescribed optical reading device. The prototype yielded reading speeds that are comparable to optical devices but slower than a CCTV The brightness and clarity of the laser display have potential for the development of future low vision devices.

40.5L: Late‐News Paper: TFT‐LCD with RGBW Color System

AbstractAlthough LCDs are widely used in power‐consumption critical applications, they are not very energy‐efficient. The largest absorber of light is the color filter. We developed a TFT‐LCD with four‐color subpixels: red, green, blue and white. The addition of the white subpixel greatly enhanced the light efficiency: up by 50%. The RGB‐to‐RGBW mapping algorithm was designed so that the hue and saturation remains unchanged from the original color. The result is a very bright display with color characteristic almost identical to RGB LCDs.

LP‐2: Late‐News Poster: High Performance Plasma Enhancement Filters

AbstractA new plasma enhancement filter architecture has been introduced to the market with benefits such as increased display brightness (high overall filter transmittance), improved environmental durability, improved surface quality, color balancing and index matching. This greatly simplified design is achieved via a patent pending thin film barrier overcoat process that replaces the traditional costly lamination techniques and avoids the quality issues associated with lamination.

MOCVD technology in research, development and mass production

The recent years have seen a continuous transfer of exciting new technologies from basic research institutions to high-yield mass production and into our everyday lives. Devices made from novel semiconductor compounds can be found in products ranging from consumer electronics to high-speed backbone communication networks. This includes high-power infrared laser diodes for glass fiber applications, light-emitting diodes of ultra-high brightness for display and lighting, high-power blue and UV laser diodes for mass storage as well as all types of transistors made from silicon, III–V compounds and silicon-carbide. To facilitate the easy and straightforward transfer from research scale experimental setups to large-area substrates for mass production AIXTRON offers the whole scale of epitaxy solutions from single-wafer systems to large-scale production machines for up to 95 wafers. The easy configurability of the systems in terms of up-scaling of wafer sizes up to 7×6 in for phosphides and arsenides and up to 7×3 inch for nitride materials in concurrence with easy maintenance, high reproducibility and high uniformity across the wafer and from wafer-to-wafer, make the AIXTRON systems the ideal solution for mass production. The growth principle common to all AIXTRON MOCVD systems allows the easy up-scaling of established processes to larger configurations, even from single-wafer AIX 200 systems to production-type Planetary Reactors ®. Add-ons like in situ monitoring of the growth process by reflectometry (Filmetrics ®) or Reflectance Anisotropy Spectroscopy (Epi-RAS ®) help in a considerable reduction of the development time and costs, hence improving innovation cycles and the time-to-market of novel devices since the growth of the material can be monitored in real time.

51.1: Invited Paper: Polymers for Efficient OLEDs

AbstractPolymer light‐emitting diodes (PLEDs) and displays based on polymer technology have made dramatic progress during the last years. In particular, efficiency and device lifetime have improved to such a significant extent that first products will commercialized within this year. We report here on the technical status of materials and devices upon which this success is based. Efficiency and especially operational stability are now at a level which easily meets the requirements for a variety of applications, namely power efficiencies are well above 10 lm/W, operational lifetimes are exceeding 20000 hours at display brightness levels and room temperature). This progress has been achieved by the careful analysis of failure mechanisms and the systematic improvement of materials. The first products, i. e. back‐lights (for LCD‐displays), segmented displays, and finally passive‐matrix‐addressed low‐information‐content (LIC) graphical displays are described. Light emitting polymerss are now manufactured on industrial scale under high purity conditions; filling and packaging is done under a class 10 clean room condition. For details see H. Becker Paper 46.1.

42.4: Novel Manufacturing Process of TFT‐LCD Featuring C/F on Array and Its Applications

AbstractWe evaluated new manufacturing process featuring with integration of C/F and TFT Array, Rigid spacer as an assistant black matrix, and organic insulator for multi‐purpose of color filter protection and C/F via hole formation. By combining with conventional 5 mask TN mode of top pixel electrode architecture, we could develop novel manufacturing process for displaying performance enhancement and improved productivity. 15.0 inch‐XGA prototype panel with up to 80% of final aperture ratio and 25% increase of display brightness was fabricated.

A real-time/non-real-time spectrum analyzer for musical sounds

A color spectrum analyzer specialized for visualization of musical sounds has been developed for the Macintosh Power PC computer. Input samples (monaural or stereo) can be obtained from microphone or CD-ROM input in real time or from a sound file in nonreal time. Spectral analysis can be tuned specifically to the fundamental frequency of the input signal using sample rate conversion (tuned case), or it can be based on a specified window size at the input sample rate (nontuned case). In the tuned case each spectral component corresponds to a harmonic of the input. Several different displays can occur simultaneously: an oscilloscope waveform display; a 1D spectrum, where an amplitude-vs-frequency graph varies as time progresses; a spectral waterfall display; a 2D spectrum showing frequency vs time with amplitude registered as degree of display brightness; a 3D display showing amplitude vs time vs frequency at an arbitrary orientation. In addition to time-varying graphs which are available for both real and nonreal time, static plots are available for preanalyzed file input. For stereo signals it is possible to plot output/input transfer functions. Spectral time averaging is also available for cases where the instantaneous spectrum is unstable

New functional polymers for liquid crystal displays review of some recent developments

Polymeric materials play an important role in the construction and performance of liquid crystal displays. New functional polymers are developed to improve the displays on brightness, power efficiency and viewing angle performance. Polymer films with a controlled molecular structure and architecture provide new polarization optics to convert non-polarized light into polarized light with higher efficiency than the traditional polarizers based on stretched iodine doped poly(vinyl alcohol). Other films provide a polarization compensation function to maintain an angular invariant net optical retardation of the display device and therewith a better contrast to wider viewing angles. Color generation by non-absorbing methods is believed to improve on the display brightness. Special control of the liquid crystal alignment by photo-sensitive orientation layers, polymer protrusions or photo-formed polymer walls provide multiple director patterns within a single pixel to average out angular LC effects.

ディスプレイの階調再現特性と周囲光の関係

The effectiveness of using a PLUGE (picture line-up generating equipment) signal to improve a display's grayscale reproduction under ambient illumination was investigated using two new metrics. Experimental results showed that adjusting a display's brightness with a PLUGE signal enables more precise adjustment than with a general image. A metric for the volume of reproducible color space was used to describe the area that a display can reproduce in the color space. A metric for the color reproduction reduction rate was used to describe how gray-scale reproduction deteriorates under ambient illumination. The values obtained for these metrics showed that adjusting the brightness with a PLUGE signal improves grayscale reproduction.