Projection‐based head‐tracking 3‐D displays

Abstract— This paper describes the construction and operation of four 3‐D displays in which each display produces two images for each eye and thus fits into the category of projection‐based binocular stereoscopic displays. The four 3‐D displays described are pico‐projector‐based, liquid‐ crystal—on—silicon (LCOS) conventional projector‐based, 120‐Hz digital‐light‐processor (DLP) projector‐ based, and the HELIUM3D system. In the first three displays, images are produced on a direct‐view LCD whose conventional backlight is replaced with a projection illumination source that is controlled by a multi‐user head tracker; novel steering optics direct the projector output to regions referred to as exit pupils located at the viewers' eyes. In the HELIUM3D display, the image information is supplied by a horizontally scanned, fast, light valve whose output is controlled by a spatial light modulator (SLM) to direct images to the appropriate viewers' eyes. The current statu s and the multimodal potential of the HELIUM3D display are described.     

Alignment control of liquid crystals in a 1.0‐μm‐pitch spatial light modulator by lattice‐shaped dielectric wall structure

We achieved uniform liquid crystal (LC) alignment in lattice‐shaped dielectric walls 1 μm in pitch; this is a prerequisite when driving the individual pixels of spatial light modulators, facilitating the development of practical electronic holographic displays with a wide field of view. In lattice‐shaped dielectric walls, LC alignment becomes unstable, particularly on the bottom and the walls; the LC directors tend to align parallel to the walls. To overcome this problem, we created lattice‐shaped walls featuring partition plates that allow uniform LC alignment. When the plates confine LCs to small regions exhibiting spatial anisotropy, the LC elastic effect and wall anchoring forces align the LC directors parallel to the long anisotropic axis. We found that pixels 0.5 μm × 1.0 μm in pitch formed if the partition plates were sufficiently thick to allow shielding of electric field leakage.     

Vertically integrated,double stack oxide TFT layers for high‐resolution AMOLED backplane

We developed a novel vertically integrated, double stack oxide thin‐film transistor (TFT) backplane for high‐resolution organic light‐emitting diode (OLED) displays. The first TFT layer is bulk‐accumulation mode, and the second TFT layer is a single gate with back‐channel etched structure. The extracted mobilities and threshold voltages are higher than 10 cm²/Vs and 0 ~ 1 V, respectively. Both TFTs are found to be extremely stable under the bias and temperature stress. The gate driver with width of 530 μm and a pitch of 18.6 μm was developed, exhibiting well shifted signal up to the last stage of 900 stages without output degradation, which could be used for 1360 ppi TFT backplane.     

Development of G6 exposure tool for 1.2 μm resolution

We have proposed exposure method using Deep UV (DUV) exposure light to realize high resolution and high productivity in FPD lithography. Here, we show development concepts for our new G6 exposure tools with DUV light sources and exposure test results with a test exposure tool.     

An averaging pixel structure using microcrystalline‐silicon films prepared at high temperature for AMOLED displays

Abstract— A new voltage‐addressed pixel using a multiple drive distribution has been developed to improve, in a simple way, the brightness uniformity of active‐matrix organic light‐emitting‐diode (AMOLED) displays. Moreover, circuits were realized using microcrystalline‐silicon (μc‐Si) films prepared at 600°C using a standard low‐pressure CVD system. The developed p‐channel TFTs exhibit a field‐effect mobility close to 6 cm²/V‐sec. The experimental results show that the proposed spatial distribution of driving TFTs improves the uniformity of current levels, in contrast to the conventional two‐TFT pixel structure. Backplane performances have been compared using circuits based on μc‐Si and furnace‐annealed polysilicon materials. Finally, this technology has been used to make an AMOLED demonstration unit using a top‐emission OLED structure. Thus, by combining both an μc‐Si active‐layer and a current‐averaging driver, an unsophisticated solution is provided to solve the inter‐pixel non‐uniformity issue.     

A new current‐mirror pixel circuit employing poly‐Si TFTs for active‐matrix organic light‐emitting‐diode displays

Abstract— A novel active‐matrix organic light‐emitting‐diode (AMOLED) display employing a new current‐mirror pixel circuit, which requires four‐poly‐Si TFTs and one‐capacitor and no additional signal lines, has been proposed and sucessfully fabricated. The experimental results show that a new current mirror can considerably compensate luminance non‐uniformity and scale down a data current more than a conventional current‐mirror circuit in order to reduce the pixel charging time and increase the minimum data current. Compared with a conventional two‐TFT pixel, the luminance non‐uniformity induced by the grain boundaries of poly‐Si TFTs can be decreased considerably from 41% to 9.1%.     

Performance of high‐efficiency AMOLED displays

Abstract— In this paper, the performance of active‐matrix‐driven small‐molecule OLED displays incorporating high‐efficiency electrophosphorescent dopants were analyzed. These enable triplet excitons to contribute to light emission and have led to pixel efficiencies of over 40 lm/W. By considering a conventional two TFT per pixel addressing scheme, we show how this OLED design enables the fabrication of very‐low‐power‐consumption displays (lower than AMLCDs). We simulate display performance and perform a trade‐off analysis comparing the power consumption of displays driven by both amorphous‐silicon and low‐temperature poly‐Si TFTs.     

In‐pixel temperature sensor for high‐luminance active matrix micro‐light‐emitting diode display using low‐temperature polycrystalline silicon and oxide thin‐film‐transistors

We propose an in‐pixel temperature sensor using low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistor (TFTs) for high‐luminance active matrix (AM) micro‐light‐emitting diode (LED) displays. By taking advantage of the different off‐current characteristics of p‐type LTPS TFTs and n‐type a‐IGZO TFTs under temperature change, we designed and fabricated a temperature sensor consists of only LTPO TFTs without additional sensing component or material. The fabricated sensor exhibits excellent temperature sensitivity of up to 71.8 mV/°C. In addition, a 64 × 64 temperature sensor array with 3T sensing pixel and integrated gate driver has also been fabricated, which demonstrates potential approach for maxing out the performance of high‐luminance AM micro‐LED display with real‐time in‐pixel temperature monitoring.     

a‐InGaZnO thin‐film transistors for AMOLEDs: Electrical stability and pixel‐circuit simulation

Abstract— Inverted‐staggered amorphous In‐Ga‐Zn‐O (a‐InGaZnO) thin‐film transistors (TFTs) were fabricated and characterized on glass substrates. The a‐InGaZnO TFTs exhibit adequate field‐effect mobilities, sharp subthreshold slopes, and very low off‐currents. The current temperature stress (CTS) on the a‐InGaZnO TFTs was performed, and the effect of stress temperature (TSTR), stress current (ISTR), and TFT biasing condition on their electrical stability was investigated. Finally, SPICE modelling for a‐InGaZnO TFTs was developed based on experimental data. Several active‐matrix organic light‐emitting‐display (AMOLED) pixel circuits were simulated, and the potential advantages of using a‐InGaZnO TFTs were discussed.     

Letter: A new compensation pixel circuit with metal oxide thin‐film transistors for active‐matrix organic light‐emitting diode displays

This paper presents a novel compensation pixel circuit for active‐matrix organic light‐emitting diode displays, in which the coupling effect mask technology is developed to compensate the threshold voltage of driving thin‐film transistor whether it is positive or negative. Twenty discrete compensation pixel circuits have been fabricated by In‐Zn‐O thin‐film transistors process. It is measured that the non‐uniformity of the proposed pixel circuit is significantly reduced with an average value of 8.6%. Furthermore, the organic light‐emitting diode emission current remains constant during 6 h continuous operation, which also confirms the validity of the proposed pixel circuit.     

A 470 × 235‐ppi poly‐Si TFT‐LCD for high‐resolution 2‐D and 3‐D autostereoscopic displays

Abstract— We have developed a 470 × 235‐ppi poly‐Si TFT‐LCD with a novel pixel arrangement, called HDDP (horizontally double‐density pixels), for high‐resolution 2‐D and 3‐D autostereoscopic displays. 3‐D image quality is especially high in a lenticular‐lens‐equipped 3‐D mode because both the horizontal and vertical resolutions are high, and because these resolutions are equal. 3‐D and 2‐D images can be displayed simultaneously in the same picture. In addition, 3‐D images can be displayed anywhere and 2‐D characters can be made to appear at different depths with perfect legibility. No switching of 2‐D/3‐D modes is necessary, and the design's thin and uncomplicated structure makes it especially suitable for mobile terminals.     

Toward high‐resolution,inkjet‐printed,quantum dot light‐emitting diodes for next‐generation displays

We have investigated the possibility of fabricating quantum dot light‐emitting diodes (QLEDs) using inkjet printing technology, which is the most attractive method for the full‐color patterning of QLED displays. By controlling the quantum dot (QD) ink formulation and inkjet printing condition, we successfully patterned QLED pixels in the 60‐in ultrahigh definition TV format, which has a resolution of 73 pixels per inch. The inkjet‐printed QLEDs exhibited a maximum luminance of 2500 cd/m². Although the performance of inkjet‐printed QLEDs is low compared with that of QLEDs fabricated using the spin‐coating process, our results clearly indicate that the inkjet printing technology is suitable for patterning QD emissive layers to realize high‐resolution, full‐color QLED displays.     

Fast voltage‐driving scheme for AMOLED displays based on internal feedback

Abstract— A new driving scheme for active‐matrix organic light‐emitting diodes (AMOLED) displays based on voltage programming is proposed. While conventional voltage drivers have a trade‐off between speed and accuracy, the new scheme is inherently fast and accurate. Based on the new driving scheme, a fast pixel circuit is designed using amorphous‐silicon (a‐Si) thin‐film transistors (TFTs). As the simulation results indicate, this pixel circuit can compensate the threshold‐voltage shift (VT shift) of the driver transistors. This pixel can be programmed in just 10 μsec, and it can compensate the threshold‐voltage shifts over 5 V with an error rate of less than 5% for a 1 ‐μA pixel current.     

Static‐volumetric display using rotational‐slicing approach for rendering 3‐D images

Abstract— This work is related to static volumetric crystals which scintillate light when two laser beams are intersected within the crystal. The geometry in this crystal is optimized for linear slices. Most volumetric displays are based on rotational surfaces, which generate the images, while the projected images are sliced in a rotational sweep mode. To date, the majority of 3‐D graphic engines based on static‐volume displays have not been fully developed. To use an advanced 3‐D graphic engine designed for a swept‐volume display (SVD) with a static‐volume display, the display must emulate the operation of a SVD based on a rotational‐slicing approach. The CSpace® 3‐D display has the capability to render 3‐D images using the rotational‐slicing approach. This paper presents the development of a rotational‐slicing approach designed to emulate the operation of a SVD within the image volume of a static‐volume display. The display software has been modified to divide the 3‐D image into 46 slices, each passing through the image center and rotated at a fixed angle from the previous slice. Reconstructed 3‐D images were demonstrated using a rotational‐slicing approach. Suggestions are provided for future implementations that could aid in the elimination of elongations and distortions, which occur within specified slices.     

A flexible 2.1‐in. active‐matrix electrophoretic display with high resolution and a thickness of 100 μm

Abstract— A paper‐thin QVGA, flexible 2.1‐in. active‐matrix electrophoretic display (AMEPD) that features 100‐μm thick and a 192‐ppi resolution has been developed. An LTPS‐TFT backplane with integrated peripheral driver circuits was first fabricated on a glass substrate and then transferred to a very thin (30‐μm) plastic film by employing surface‐free technology by laser ablation/annealing (SUFTLA®). A micro‐encapsulated electrophoretic imaging sheet was laminated on the backplane. A supporting substrate was used to support the LTPS‐TFT backplane. Fine images were successfully displayed on the rollable AM‐EPD. The integrated driver circuits dramatically reduce the number of external connection terminals, thus easily boosting the reliability of electrical connections even on such a thin plastic film.     

Design of dual‐outputs‐single‐stage a‐Si:H TFT gate driver for high resolution TFT‐LCD application

A new gate driver has been designed and fabricated by amorphous silicon technology. With utilizing the concept of sharing the noise free block in a single stage for gate driver, dual‐outputs signals could be generated in sequence. By increasing the number of output circuit block in proposed gate driver, number of outputs per stage could also be adding that improves the efficiency for area reduction. Besides, using single driving thin‐film‐transistor (TFT) for charging and discharging, the area of circuit is also decreased by diminishing the size of pulling down TFT. Moreover, the proposed gate driver has been successfully demonstrated in a 5.5‐inch Full HD (1080xRGBx1920) TFT‐liquid‐crystal display panel and passed reliability tests of the supporting foundry.     

Development of active matrix LCD for use in high‐resolution adaptive headlights

Conventional adaptive driving beam headlamps are limited in achieving still higher quantities of switchable pixels by the number of LEDs and movable elements needed. In this paper, it is shown that by integrating an active matrix liquid crystal display module, it is possible to realize fully adaptive high‐resolution headlights without mechanical elements and a finite number of LED with 30 k switchable pixels.     

Characteristics of a‐IZO TFTs with high‐κ HfSiOx gate insulator annealed in various conditions

In this work, we investigate the enhanced performance of amorphous indium zinc oxides‐based thin film transistors with hafnium silicate (HfSiO_x) gate insulators. HfSiO_x gate insulators annealed at various conditions are deposited by cosputtering of hafnium oxide and Si. The structural properties of HfSiO_x are investigated using the atomic force microscopy, X‐ray diffraction, and x‐ray photoelectron spectroscopy (XPS). techniques. Furthermore, the electrical characteristics of HfSiO_x are analyzed to investigate the effect of annealing conditions. We obtain optimal results for thin film transistors with HfSiO_x gate insulators annealed for 1 h at 100 °C, with a saturation mobility of 1.2 cm²/V · s, threshold voltage of 2.2 V, on current/off current ratio of 2.0 × 10⁶, and an insulator surface roughness of 0.187 nm root mean square.     

Decision‐tree‐based methods for differential diagnosis of β‐thalassemia trait from iron deficiency anemia

Several discrimination indices have been proposed to distinct between β‐thalassemia trait (βTT) and iron deficiency anemia (IDA). This study is the first application of tree‐based methods for differential diagnosis of βTT from IDA. One hundred forty‐four patients with hypochromic microcytic anemia aged 18–40 years old from Ayat Hospital of Tehran were recruited. Classification and Regression tree, CHi‐squared Automatic Interaction Detector (CHAID), Exhaustive CHi‐squared Automatic Interaction Detector (E‐CHAID), Quick, Unbiased, Efficient Statistical Tree (QUEST), Classification Rule with Unbiased Interaction Selection and Estimation (CRUISE), and Generalized, Unbiased, Interaction Detection and Estimation (GUIDE) have been used to discriminate the diagnosis. Mean corpuscular volume (MCV) was found as the main predictor in discrimination. All the mentioned tree‐based methods showed acceptable sensitivity, specificity, accuracy, Youden's index, false positive and negative rate, positive and negative predictive values and AUC in differential diagnosis of βTT from IDA. However, Classification Rule with Unbiased Interaction Selection and Estimation revealed more precise classification with an area under the curve value of 0.99. Decision‐tree‐based methods can be used to develop sensitive and accurate diagnostic methods for differentiating βTT from IDA.     

EO characteristics for a photoaligned VA‐1/4 π cell on a photopolymer layer

The generation of a liquid‐crystal (LC) tilt angle on a copolymer with chalconyl and cholesteryl moiety characteristics was performed, and the electro‐optical (EO) performance of the photoaligned vertical‐alignment (VA) 1/4 π cell by polarized UV exposure on a homeotropic photopolymer surfaces was studied. The LC tilt angles decreased as UV exposure time increased on the copolymer surfaces. A tilt angle of 87° in NLC was observed with an UV exposure of 3 min on the photoalignment‐2 surface. The LC tilt angle is attributed to increased chalcone moiety with increasing UV exposure time. Excellent voltage‐transmittance (V‐T) curves of the photoaligned VA 1/4 π cell by polarized UV exposure on the photopolymer surface for 3 min containing a cholesteryl moiety of 8% were obtained. The V‐T and response‐time characteristics can be improved by the presence of a cholesteryl moiety in the photopolymer.