A preview of the papers appearing in the January 2006 issue of the Journal of the SID, available on-line at www.SID.org.

Edited by Aris Silzars

Hybrid spatial–temporal color synthesis and its applications

Louis D. Silverstein
Sander J. Roosendaal
Martin J. J. Jak

VCD Sciences, Inc.

Abstract — A novel approach of synthesizing display color by hybrid color processing in both the spatial and temporal domains is introduced. The rational basis for this approach is found in vision science, and more particularly in the spatial and temporal characteristics of the human visual system. Various examples of the new approach, aiming at different display-performance objectives, are described. Hybrid spatial–temporal color synthesis can be used to generate a three-primary RGB display, the analysis of which reveals a higher spatial resolution and a lower fixed-pattern noise. The concept has also been used to build, based on a conventional LCD panel in combination with an adapted backlight system, a six-primary LCD TV with a 22% wider color gamut. Finally, the approach is demonstrated in a four-primary mobile LCD and results in lower cost combined with a higher display luminance and a wider color gamut.

Relative to displays using temporal color synthesis alone, marked reductions in color field rate, minimization of color break-up, and improved light efficiency can be realized by using STColor. Moreover, the method provides many degrees of freedom for selecting combinations of temporally switched illuminants and color-filter mosaics to achieve different display-performance objectives. The method is illustrated for three different applications. It is used in a three-primary RGB display to show the potential gain in spatial resolution and reduction in fixed-pattern noise. It is demonstrated in a 30-in. spectrum-sequential LCD TV based on two different types of hot-cathode fluorescent lamps that alternately illuminate a conventional panel. And, it is demonstrated in aspectrum-sequential mobile LCDs, based on a mosaic pixel structure of two color filters in combination with two different LED light sources. This design enables a high-resolution display with a high aperture ratio, enhanced luminance throughput, and a wide color gamut, and at relatively low cost.

FIGURE 4 — RGB vertical-stripe pixel mosaic with associated spatial Nyquist limits and fixed-pattern noise-modulation spectrum.


Post-transmission digital video enhancement for the visually impaired

Matthew Fullerton
Eli Peli

Schepens Eye Research Institute

Abstract — Image enhancement has been shown to improve the perceived quality of images and video for people with visual impairments. The MPEG coding scheme makes spatial filtering, likely to help those with such impairments, possible at the decoding stage. A real-time platform was implemented for testing and improving contrast-enhancement algorithms for MPEG video, with controls appropriate for the target population. The necessary additional processing runs efficiently on a general-purpose PC and can be integrated easily into existing MPEG-2 decoders. The system has enabled substantial improvement over the previous filtering algorithm, reducing artifacts exhibited in the previous implementation and facilitating individual user selection of enhancement parameters in evaluation studies.

FIGURE 7 — Illustration of MPEG-based enhancement using the new method (libmpeg2) demonstrating replication of the previous (Restream) method. (a) New method with λ =1.0, α = 1.0. (Unenhanced image) (b) Previous method with λ =4.0, α = 1.5. (c) New method with λ =4.0, α =1.5.


Roll-to-roll manufacturing considerations for flexible, cholesteric liquid-crystal display (Ch-LCD) media

G. Thomas McCollough
Charles M. Rankin
Megan L. Weiner

Eastman Kodak Co.

Abstract — Roll-to-roll methods and equipment to manufacture a bistable, passively driven display media on a flexible substrate have been developed. Using continuous coating techniques and equipment, cholesteric liquid-crystal droplets in a gelatin binder and a dark layer are simultaneously coated onto laser-etched-patterned transparent ITO conductors on a polymeric web. Second conductors are printed with a UV-curable polymer thick-film ink over the active display layers, followed by slitting and chopping to complete the manufacture of display media in a full roll-to-roll mode. Segmented- and matrix-display media can be generated using these techniques. This paper will focus on the manufacturing considerations for producing matrix-display media.

The objective of this project was to create the initial manufacturing capability for flexible, cholesteric liquid-crystal display (Ch-LCD) media in both segmented and matrix formats. The initial flexible bistable display media was produced in the research laboratories of Eastman Kodak Co. by first using a narrow-width roll-to-roll laser etcher to segregate the bottom electrode of ITO on PET (ITOp). A narrow-width continuous-coating machine was used to precisely deposit and dry the cholesteric liquid-crystal (Ch-LC) droplets dispersed in a water-soluble binder layer (PDLC) and a dark layer (DL). This was followed by panel-based operations to remove coated material that was covering selected areas of the first conductor and screen printing thermally cured conductive, polymer thick-film ink to form the top conductors (C2) and interconnect pads (PC).

FIGURE 1 — 3-D view of flexible-display media structure.


Layer-thickness simulation for static thin-film deposition on Gen 6/Gen 7 substrates

Andreas Lopp
Stefan Bangert
Wolfgang Buschbeck
Markus Hanika
Michael König
Jörg Krempel-Hesse
Harald Rost
Jürgen Schroeder
Tobias Stolley

Applied Films GmbH & Co. KG

Abstract — The movement of particles from a target to a substrate during the sputter process was studied using the Monte Carlo simulation technique. The momentum and energy distribution of the ejected particles were taken into account along with the change of momentum and energy in their collisions with gas atoms. The momentum transfer from the ejected target atom to the gas atom was used to estimate the gas rarefaction in front of the target. Layer-thickness distributions of different target materials were calculated and compared with experimental measurements. The results were used to optimize the uniformity of static thin-film depositions on Gen 6/Gen 7 substrates from a large-area cathode array.

Computer simulation of the sputtering process for predicting the layer uniformity is proving to be a very helpful tool used for the design of the sputter environment. In this work, we use the Monte Carlo method to calculate the layer-thickness distribution. We used the TRITON™ sputtering system for our experiments with an array of nine rotatable cathodes for static thin-film deposition on Gen 6 glass substrates. The layer-thickness uniformity of a range of target materials was investigated and the simulation results were compared with experimental measured data.

FIGURE 4 — Simulation of 100 trajectories for molybdenum.


System considerations for RGBW OLED displays

Jeffrey P. Spindler
Tukaram K. Hatwar
Michael E. Miller
Andrew D. Arnold
Michael J. Murdoch
Paul J. Kane
John E. Ludwicki
Paula J. Alessi
Steven A. Van Slyke

Eastman Kodak Co.

Abstract — The fabrication of full-color RGBW OLED displays using a white emitter with RGB color filters has been previously described. This paper discusses the effect of several display-system factors on the important RGBW OLED display performance attributes of power consumption, lifetime, and perceived image quality. These display-system factors include the spectrum of the white OLED, the white OLED structure, the color-filter selection, the subpixel aperture ratios, and the pixel arrangement (including sub-sampling).

The addition of a fourth color subpixel in any direct-view display technology increases the number of subpixels within each display pixel. This additional subpixel will reduce the pixel aperture ratio (PAR) of a display for any given pixel resolution. The reduction in PAR can reduce the effective luminous efficiency of an LCD because a smaller proportion of the display allows light to pass from the backlight to the observer. In an OLED display, the reduction in PAR affects only lifetime since, for a given display luminance, a smaller PAR translates to the need to drive each subpixel with a higher current density, which negatively impacts the lifetime of an OLED. This effect is a significant factor when evaluating RGBW OLEDs.

FIGURE 5 — Rendering of a magnified view of a group of RGBW pixels for two renderings from a small portion of an image. The portion is indicated by the yellow square in the photograph. The top-right rendering represents a WMR of 1.0, while the bottom-right rendering represents a WMR of 0.5.


Alternative approach to large-sized AMOLED HDTV

Ho-Kyoon Chung
Ki-Yong Lee
Seong Taek Lee

Samsung SDI Co., Ltd.

Abstract — In this work, alternative approaches to existing technologies for the fabrication of large-sized AMOLEDs, such as non-laser crystallization methods for poly-Si TFT fabrication and color patterning using laser-induced thermal imaging (LITI), is proposed. In particular, it was found that the Super Grain Silicon (SGS) crystallization method resulted in high-performance TFTs in terms of mobility and off-current. The feasibility of these techniques for large-sized AMOLEDs is demonstrated by 17-in. UXGA AMOLED displays which show good brightness uniformity.

The TFT performance for various crystallization methods was compared. TFTs having a field-effect mobility of 63 cm2/V-sec and a sufficiently low off-current have been fabricated by utilizing SGS (Super Grain Silicon) crystallization technology. It was found that a 1-nm surface roughness of SGS poly-Si film yielded the highest oxide breakdown field of about 9 MV/cm, promising superior interface reliability. For the color patterning of AMOLEDs for large-sized HDTVs, a laser-induced thermal-imaging (LITI) technology is proposed, which, as a full-color patterning method for large-sized HDTVs, has great advantages in terms of high resolution, dry patterning process, and scalability to large-sized motherglass.

FIGURE 11 — Image of 17-in. UXGA AMOLED fabricated by employing SGS poly-Si TFTs.


Development of 1.5-in. full-color double-sided active-matrix OLED with novel array design

Chung-Wen Ko, Shuo-Hsiu Hu,
Shi-Hao Li, Tiao-Hung Hsiao,
Kou-Sheng Lee, Che-Jen Chen,
Jui-Hsing Chen, Jiin-Jou Lih

AU Optronics Corp.

Abstract — A 1.5-in. full-color double-sided AMOLED with a novel array design was fabricated. Different images on both sides of the panel can be controlled by using only one IC driver. High color gamuts of 67% and 81% on the bottom- and top-emitting sides, respectively, were achieved. In addition, good performance on both sides, such as brightness and white balance, were also achieved.

The double-sided AMOLED can significantly reduce the thickness form factor and weight. The technology behind the independent image control of double-sided OLED opens up the application of double-sided AMOLEDs. Each side of the panel can simultaneously display different images without signal interferences. Both sides are controlled by only one set of IC drivers and exhibit high-quality images. In the design, only one AMOLED backplane is required for this innovative display, so the cost is similar to single-sided AMOLEDs. The cost of a double-sided AMOLED is virtually only one half of that for a double display module. The novel TFT pixel design and simple OLED evaporation process makes the double-sided AMOLED highly manufacturable.

FIGURE 4 — Designed architectures for bottom- and top-emitting OLEDs.


FIGURE 7 — Photograph of prototype 1.5-in. double-sided AMOLED display.


Highly efficient deep-blue organic light-emitting devices

Meng-Ting Lee
Chi-Hung Liao
Chih-Hung Tsai
Chin H. Chen

National Chiao Tung University

Abstract — A highly efficient deep-blue organic light-emitting device (OLED) incorporating a novel composite hole-transport layer (c-HTL) and an emitter based on the new non-symmetrical mono(styryl)amine fluorescent dopant in the stable host MADN, which achieved a luminance efficiency of 5.4 cd/A with a Commission Internationale d'Eclairage (CIE x,y) of (0.14, 0.13) and an external quantum efficiency of 5.1% at 20 mA/cm2 and 6.8 V, is reported. The increased device efficiency is attributed to an improved balance between hole and electron currents in the recombination zone.

The PL solution of BD1, BD2, and BD3 in toluene, compared with DSA-Ph, are shown in Fig. 2. Their peak fluorescence λmax are located at 438, 442, and 448 nm and the full width at half maximum (FWHM) are 58, 62, and 64 nm, respectively, which is about 20 nm less than that of the sky-blue dopant, DSA-Ph (λmax = 458 nm, FWHM = 58 nm). The hypsochromic shift is believed to result from shortening the chromophoric conjugation as well as modifying the aromatic substituents of the mono(styryl)amine-based dopants. In order to produce a deep-blue OLED in this study, the bluest compound, BD1, was judiciously chosen to be the dopant.

FIGURE 2 — PL solutions BD1, BD2, and BD3 vs. DSA-Ph in toluene.


Development of a 32-in. slim CRT with 125° deflection

Kuedong Ha
Soon-Cheol Shin
Do-Nyun Kim
Kue-Hong Lee
Jeong-Hoon Kim

Samsung SDI Co., Ltd.

Abstract — Today, CRT markets are being threatened by flat-panel displays (FPDs) even though the screen quality of the CRT is one of the best of existing display devices. The depth of CRTs is one of its most important design factors that must be addressed in order to maintain its dominant position in the display market. Thus, a 32-in. wide-deflection-angle (125°) CRT (tube length of 360 mm) has been developed, and mass production began in January 2005. Wide deflection requires more advanced design of the major parts and reliable facilities in the production line. In this paper, new designs, mainly for deflection yokes and electron guns, will be introduced, which are considered the most difficult to design. These wide-deflection-angle CRTs attracted an extraordinary amount of attention even from end users in a variety of display shows last year, and this will help maintain the solid position of CRTs in the coming era.

To develop a deflection yoke (DY) with a 125° deflection angle, a simulation-based design of experiment (DOE) for the optimization of the DY parameters on the basis of an optimal funnel cone shape was used. A horizontal deflection sensitivity of 51 mJ was achieved. For the improvement of geometric distortion (G/D), the relative position between the e-gun and DY was controlled and a method for TV circuit correction was adapted. A single dynamic focus gun with a new structure was developed to meet the focus requirements and to achieve dynamic voltage below 1 kV. To reduce the dynamic parabolic voltage, the design is directed to strengthen the effects of the main focus lens and quadruple lens intensity. The spot sizes of Vixlim was maintained to be comparable to those of the conventional type.

FIGURE 20 — Panel height (H1) and funnel height (H2) in a Vixlim tube.


Fabrication and characterization of surface-conduction electron emitters for SED application

K. Yamamoto
T. Oguchi
K. Sasaki|
I. Nomura
S. Uzawa
K. Hatanaka

SED, Inc.

Abstract — A surface-conduction electron emitter (SCE) for next-generation flat-panel displays has been developed. PdO thin films (approximately 10 nm thick) produced by an ink-jet process were used to form the surface-conduction electron emitter. The films were electroformed and activated while a voltage was applied, and an electron emitter with good characteristics was obtained. A current density of approximately 30 mA/cm2 was attained when an anode voltage of 10 kV was applied. Furthermore, a 36-in. surface-conduction electron-emitter display (SED), consisting of SCEs and a phosphor screen similar to that of a CRT, was also developed.

FIGURE 1 — Structure of an SED.


FIGURE 6 — Fabrication of carbon nano-gap.


A 25-in. SMPDP with fine pitch and high resolution

Yongming Tang,
X. Zhang, Q. Li,
Y. Tu, Y. S. Zheng,
Z. Wu, J. Xia,
Z. W. Fan, B. P. Wang,
L. S. Tong

Southeast University

Abstract — A 25-in. shadow-mask PDP (SMPDP) with fine pitch and high resolution has recently been developed as a succession of the 34-in. SMPDP, which had been exhibited at ASID '04. SMPDP was regarded as a hopeful low-cost PDP solution. The new pitch size of 0.66 mm realized an SVGA resolution on this 25-in. SMPDP, and it also promises HDTV-resolution compatibility for a 42-in. SMPDP. The discharge cell has been re-designed and the delta-type arrangement of discharge cells has been applied, which provides more display area and facilitates the panel fabrication as well. Other modifications, such as the bus-electrode structure and the alternative of glass material for substrates, have been tested. A peak luminance of 500 cd/m2 and a total power consumption of 100 W have been achieved for the 25-in. SMPDP sample.


FIGURE 4 — Comparison of cell structures and subpixel arrangements between a 34- and 25-in. SMPDP. (Note: the two bus electrodes within each cell of the 34-in. SMPDP are connected and act as one bus electrode).


TABLE 1 — Performance of a 25-in. SMPDP


Effects of diamond and AlN layers inserted beneath the phosphor layer on the discharge characteristics of PDPs

Do-Young Park
Seong-Eui Lee
Young-Mo Kim
Jin-Seok Kim
Yong-Seog Kim

Hongik University

Abstract — In this study, the effects of diamond and AlN layers inserted beneath the phos-phor layer of the rear plate of a PDP were investigated. The layers were formed via an osmotic-pressure coating process. Macrocells and test panels were prepared to examine their effects on luminance and luminous efficacy. The results indicate that the layers primarily affect the glow-discharge behavior and eventually enhance the luminous efficacy of the PDP, suggesting the possibile improvement in the performance of PDPs.

The use of diamond and AlN layers enhances the luminous efficiency by changing the glow-discharge behavior. It is believed that the diamond and AlN layers modify the capacitance of the discharge cells and influence the distribution of the glow-discharge density. If the phosphor and diamond are assumed to have the same dielectric constant, the capacitance of the composite layer will be reduced to half the value of the phosphor layer only. It is, however, difficult to estimate the effects of the capacitance change on the discharge behavior, and further investigation is required to determine the exact mechanism for the improvement in the luminous efficacy.

FIGURE 4 —Emission intensity profiles of glow discharges in macrocells with a phosphor layer and a diamond layer. The intensity profile was scanned from top to bottom of a macroscopic cell shown in Fig. 3(c).


Characterization of inhomogeneous retarders

Michael E. Becker

Display-Metrology & Systems

Abstract — Various approaches for the measurement and evaluation of the optical characteristics of compound retarder sheets will be presented and their features and limitations will be discussed. Two ways of modeling the actual multilayer structure with an inclined uniaxial indicatrix and an inhomogeneous biaxial layer plus negative c-plate is introduced and compared, and the performance of these models is analyzed for the principal plane of light incidence and for arbitrary directions of light propagation.

In state-of-the-art LCDs, two approaches are used for reducing the variation of the luminance, contrast, and chromaticity with viewing direction, i.e., for "widening" the viewing cone:

• LC alignment in multi-domain configurations induced by surface treatment or structures or by the electric field and
• application of birefringent retarder sheets.

Accurate numerical modeling and detailed optimization of the LCD system requires precise knowledge of the physical parameters of the relevant materials and components including polarizers and retarders. These target parameters are the thickness of the layers, their complex refractive indices (in order to account for absorption) vs. wavelength of light, and the spatial distribution of the optical axes.

FIGURE 4 — Details of a typical 1-D layer-structure of an LCD with polarizers, retarders, electrodes, and other layers and components.


Display modulation by Fourier transform: A preferred method

Thomas G. Fiske
Louis D. Silverstein

Rockwell Collins

Abstract — A preferred method for determining the grating modulation of a rear-projection display using a grating image and Fourier analysis is prescribed. This method is insensitive to spatial image noise and is in better correspondence with the response of the human visual system than is the standard technique. This method is not limited to rear-projection displays and can be applied to any display technology.

The Modulation Transfer Function (MTF) or grating modulation versus spatial frequency of a display system is commonly used as a metric of the ability of the system to faithfully reproduce information as a function of spatial frequency. A Fourier analysis method as a preferred alternative to the standard method was proposed. The same grating images are used. In this method, the 2-D modulation spectrum is computed from a 2-D image. The calculation is based on 2-D FFT analysis implemented at Matlab. One could also use a 1-D analysis performed on a high-resolution slit scan-type measurement. The amplitude of the fundamental sinusoidal component of the Fourier transform (suitably normalized) is reported as the modulation.

FIGURE 5 — Magnified view of a one-line grating image on a beaded projection screen.


Performance limitations with mirror/QWP reference targets for reflective LCD measurements

W. Lewis Collier
Robert A. Powell
Kenneth A. Pietrzak
Matthew H. Smith


Abstract — Test equipment for reflective LCD devices must use a calibration target to mimic a known state of the intended display devices under test (DUTs). This target must also mimic the polarization effects of the DUTs. Traditionally, a mirror and quarter-wave plate (MQWP) assembly is used for this function. By accounting for the reflectivity of the mirror and the transmission of the QWP, a reference target can be generated. The effects of the use of a QWP in this role will be examined and additional effects for which compensation must be performed in order to achieve accurate test results will be discussed.

In order to use the MQWP as a reflectance standard, it must be properly calibrated. Due to the necessary polarization components used to view the target, it is quite difficult to calibrate an MQWP directly as a single component. Rather, it is more straightforward to calibrate the transmissions and reflectances of the individual components of the MQWP and combine them for an effective reflectance measurement. While this method should work well for a theoretically perfect QWP, variations in the retardance of a typical QWP can significantly alter the reflectance of the overall MQWP.

FIGURE 3 — Spatial variation of mica QWP retardance centered at 566 nm.