High-resolution Liquid Crystal Research Articles

Photoinduced Birefringence and Liquid Crystal Orientation on Polymers with Different Azobenzene Content in the Main Chain.

In this paper, we give an overview of novel main-chain azobenzene-based fluorinated poly(arylene ether)s with different content of azo groups, aiming at providing a better understanding of the link between a number of N═N bonds and the macroscopic response of the material. We discuss chemical synthesis and molecular structure and report on a comprehensive analysis of the polymer properties, thermal behavior, and mechanical strength. We show that a higher content of azobenzene moieties reduces the mechanical strength of the polymer materials. On the other hand, polymers with a higher content of azobenzene demonstrate higher values of induced birefringence due to a larger number of azobenzene in the trans form. The photoisomerization constants of all polymers fall within a very close range. The minor variations are attributed to the number of azobenzene groups in the polymer composition and the conformational arrangements of the polymer chain packing. The developed light-sensitive polymers were employed for dynamic control and manipulation of the liquid crystal orientation by polarization of the incident light. After the double irradiation of the substrates using appropriate photomasks, we made patterned cells that consist of domains with different high-resolution liquid crystal director orientations.

All-Inorganic Green Synthesis of Small-Sized and Efficient K2SiF6:Mn4+ Phosphor for Mini-LED Displays.

High-resolution liquid crystal display (LCD) backlight requires a color conversion layer featuring micrometer light-emitting particles and a uniform morphology. The widely used commercial red-emitting K2SiF6:Mn4+ phosphor, showing promise as a light-conversion candidate, faces limitations due to its toxic synthesis process, large particle size, and poor moisture resistance. We successfully demonstrated an efficient substitution of the highly toxic HF/TEOS/KHF2 solvent system with a commonly used HCl/SiO2/KF solvent system to synthesize the small-sized K2SiF6:Mn4+ phosphor. Additionally, surface passivation was performed to enhance the luminescence intensity and resistance to moisture, denoted as K2SiF6:Mn4+@CaF2. Accordingly, the K2SiF6:Mn4+@CaF2 phosphor presents a high luminescence efficiency (99.87%/32.84% IQE/EQE) with an average particle size of ∼2.67 μm. Notably, after exposure to 85% humidity and 85 °C temperature for 3 h, the luminescence intensity remains at 47.4% for K2SiF6:Mn4+@CaF2, while 21.2% for pristine K2SiF6:Mn4+, and only 3.5% for K2SiF6:Mn4+ synthesized by TEOS. These advancements hold great potential for improving high-resolution LCD backlighting, particularly for displays with micron-level pixels, opening up new possibilities for enhanced display technology.

Enhancing virtual reality with high-resolution light field liquid crystal display technology

Enhancing virtual reality with high-resolution light field liquid crystal display technology

FPC Design Guidelines for Enabling High-Speed Intrapanel Interface in Large-Size LCD TVs

In this work, we propose flexible printed circuit (FPC) design guidelines for high-speed signal implementation in large-size and high-resolution liquid crystal display (LCD) TV modules by analyzing signal integrity (SI) characteristics through simulation and measurement. We observed that designing an FPC for LCD TV modules that can minimize insertion loss and crosstalk in the channel is critical to successfully implementing multi-Gbps signal characteristics in large-size and high-resolution LCD TV modules. To prove this experimentally, we investigated the trends of insertion loss, impedance, and crosstalk, which are design parameters of simulation-based FPCs, and designed four FPC samples assuming their application to the intra-panel interface module of a real 75-inch LCD TV. Then, based on the measured S-parameter model, the SI performance was verified and compared by measurement and simulation to demonstrate the validity of the proposed design guidelines. In conclusion, to achieve the SI characteristics of FPCs in LCD TV modules, it is necessary to consider minimizing insertion loss and mitigating crosstalk more than any other electrical performance by enabling the differential P/N pairs to have a strong coupling relationship.

Novel pancake‐based HMD optics to improve light efficiency

AbstractRecently, compactness of head‐mounted display (HMD) products have been strongly required to improve comfortableness of user. The folded optics, so‐called “Pancake optics”, is suitable for realizing compact HMD, but there is a big drawback of lowering light efficiency. To overcome this problem, we propose a novel pancake‐based HMD optics named “Double path pancake optics” using two light paths. The optical simulation is performed to find highly optimized optical properties such as thickness, and field of view (FOV). As a result of the simulation, we fixed the appropriate design. From our simple evaluation of both brightness and transmittance, we conclude that light efficiency of “Double path pancake optics” becomes 1.8 times higher than conventional pancake optics. We made the prototype using 1200 ppi high resolution liquid crystal display (LCD) and confirmed that the high image quality can be displayed.

Orbital Angular Momentum Encoded Beam Tracking and Wavefront Sensing

The working principle of conventional Shack-Hartmann-type wavefront sensors is based on a wavefront division by two-dimensional microlens arrays and a Poynting vector mapping by comparing the focal displacements to reference measurements. At complex phase distortions or steep phase gradients, however, wavefront reconstruction can suffer from ambiguities by crossing or overlapping neighboring sub-beams, or even by a complete loss of beam trajectories. Moreover, the recognition of sub-beams can additionally be affected by parasitic reflections at optical surfaces, or scattering in a medium. A possible solution of the problem is to work with arrays of well distinguishable sub-beams. Recently, high-resolution pixelated liquid crystal spatial light modulators became available which enable to flexibly generate spatially structured light and thus to realize advanced wavefront sensors with individually encoded beams. In our experimental study we investigated the specific advantages of orbital angular momentum beams for a robust beam tracking and wavefront reconstruction. As a key point for a wavefront reconstruction from vortex arrays, the reliable detection of spiral-like image features is addressed and related strategies are proposed.

Seamless holographic image generation for a multi-vision system

This paper investigates the optical seamlessness of a holographic multi-vision display. The purpose of the multi-vision approach is to scale up the resolution of a holographic display without requiring a single extremely high-resolution spatial light modulator. Optical experiments reveal that a holographic multi-vision system with 16M pixel resolution successfully generates a seamless virtual reference plane with the essential optical characteristics of a holographic display, such as the accommodation effect and binocular parallax. It is realized from a matrix of eight (42) high-resolution transmission-type liquid crystal displays. Theoretical analysis and numerical simulations are presented for the proposed seamless holographic multi-vision system.

Antenna-on-Display Concept on an Extremely Thin Substrate for Sub-6 GHz Wireless Applications

This communication presents a concept of a sub-6 GHz antenna-on-display (AoD) that can eventually be integrated into the transparent area of a display panel of various wireless devices for the first time in the literature. The transparency of the proposed microwave AoD is realized using metal mesh conductive film and features optical transparency, which is compatible with high-resolution liquid crystal display (LCD)/organic light-emitting diode (OLED) display panel requirements. To maximize the radiation efficiency despite the extremely thin substrate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0048\lambda _{0}$ </tex-math></inline-formula> ), a traveling-wave antenna topology is inspired and further modified to incorporate the inherent structural limitations of modern-day high-resolution display panels. Eventually designed to operate in a leaky-wave mode, a novella dedicated feeding mechanism is introduced to minimize undesired coupling between the antenna structure and the display panel. The composite right-/left-handed (CRLH) unit cell employs a single shunt inductor topology to maximize the radiation efficiency. The measured 6 dB impedance bandwidth of the proposed microwave AoD is from 2.36 to 6.17 GHz, which is consistent with the fast wave region of the proposed unit cell. The measured realized gain of the microwave AoD consisting of 13 unit cells is 2.68 dBi at 5.5 GHz with a radiation efficiency of 62.5%. This is the first demonstration to ascertain that an AoD topology can be applicable at microwave applications while reducing the antenna-to-ground distance by approximately a factor of 20 compared to previous studies.

Measurement of phase modulation of LCOS SLM Santec SLM-200 and analysis of its applicability for optical reconstruction of images from diffractive elements

Phase liquid crystal (LC) spatial light modulators (SLM) are widely used for optical reconstruction of diffraction optical elements, including holograms. For this purpose high stability and linearity of phase response of SLM is required. In modern high resolution SLM digital signal addressing scheme which leads to emergence of effect of phase shift fluctuations during frame time is applied. In this paper measurements of character and peculiarities of modulation of phase shift of modern high-resolution LC SLM Santec SLM-200 were performed. Optical reconstruction of images from diffraction elements of different types was carried out, the quality of reconstruction and diffraction efficiency were assessed.

Bulk-mediated in-situ homogeneous photoalignment induced by reactive mesogen containing diphenylacetylene moiety

ABSTRACTWe designed and synthesised a reactive mesogen containing diphenylacetylene moiety in the mesogenic core and two polymerisable acrylate groups at both ends. By irradiating linearly polarised UV light on the conventional host LC mixture containing a small amount of the synthesised reactive mesogen in a sandwiched cell without an alignment layer, we demonstrated an in-situ photo-induced homogeneous alignment of liquid crystals without a pre-treated alignment layer, which was achieved by an irreversible polarisation-selective [2 + 2] photodimerization of diphenylacetylene moiety with linearly polarised UV irradiation at above the isotropic temperature of LC mixture. The resulting homogeneous alignment showed a superior initial dark state, negligible pretilt angle and excellent stabilities. Furthermore, the in-plane switching (IPS) LC cell prepared by this method exhibited a better dark state and electro-optic performance compared to that with conventional-rubbed polyimide alignment layer. The single photoirradiation process automatically resulted in a perfect alignment matching of optical axes between the top and bottom substrates in the LC cell, giving rise to an excellent dark state overcoming an intrinsic misalignment issue and complex fabrication process. The proposed in-situ alignment method is a promising candidate for cost-effective, green-manufacturing, and high-quality alignment technique in the manufacturing of high-resolution liquid crystal displays.

Tilted LCD Pixel With Liquid Crystal GRIN Lens for Two-Dimensional/Three-Dimensional Switchable Display

In this paper, high images quality switchable two-dimensional (2-D)/3-D display is achieved by carefully matching the high-resolution liquid crystal display (LCD) pixel structure and liquid crystal graded index (GRIN) lens. A parallelogram LCD pixel structure is proposed, in which the edges of each sub-pixels are slanted. At the top of the LCD pixels, the liquid crystal GRIN lens is also tilted to reduce the moire effect and the tilt angle is carefully aligned with the edges of subpixels of LCD. This accurate alignment is useful to eliminate the crosstalk and improves the imaging quality of 3-D display. The 2-D/3-D switchable display is realized by tuning the liquid crystal in the GRIN lens. Based on this, a 3-D display based on 32-inch 8K4K resolution LCD display and Liquid crystal GRIN lens was designed.

Rapid and Inexpensive Fabrication of Multi-Depth Microfluidic Device using High-Resolution LCD Stereolithographic 3D Printing

With the dramatic increment of complexity, more microfluidic devices require 3D structures, such as multi-depth and -layer channels. The traditional multi-step photolithography is time-consuming and labor-intensive and also requires precise alignment during the fabrication of microfluidic devices. Here, we present an inexpensive, single-step, and rapid fabrication method for multi-depth microfluidic devices using a high-resolution liquid crystal display (LCD) stereolithographic (SLA) three-dimensional (3D) printing system. With the pixel size down to 47.25 μm, the feature resolutions in the horizontal and vertical directions are 150 μm and 50 μm, respectively. The multi-depth molds were successfully printed at the same time and the multi-depth features were transferred properly to the polydimethylsiloxane (PDMS) having multi-depth channels via soft lithography. A flow-focusing droplet generator with a multi-depth channel was fabricated using the presented 3D printing method. Experimental results show that the multi-depth channel could manipulate the morphology and size of droplets, which is desired for many engineering applications. Taken together, LCD SLA 3D printing is an excellent alternative method to the multi-step photolithography for the fabrication of multi-depth microfluidic devices. Taking the advantages of its controllability, cost-effectiveness, and acceptable resolution, LCD SLA 3D printing can have a great potential to fabricate 3D microfluidic devices.

Flat Panel Computed Tomography in the Diagnosis of Superior Semicircular Canal Dehiscence Syndrome.

Flat panel computed tomography (FPCT) provides more accurate measurements of dimensions for superior semicircular canal dehiscence (SCD) than multislice CT (MSCT). SCD syndrome occurs when a bony defect of the superior semicircular canal causes vestibular and auditory symptoms. MSCT can overestimate the size of the canal defect, with possible over-diagnosis of SCD and suboptimal selection of surgical approach. The higher resolution of FPCT should afford more accurate measurements of these defects. Radiographic and surgical measurements were compared in 22 patients (mean age 49.4) with clinical SCD syndrome and canal defects confirmed at surgery. Twenty second FPCT scans were acquired before surgery with parameters: 109Kv, small focus, 200 degrees rotation angle, and 0.4 degree per frame angulation step. Dehiscence dimensions were measured from orthogonal multiplanar reconstructions on a high-resolution liquid crystal display monitor and compared with actual measurements recorded during microsurgery. SCD dimensions by FPCT (x) were 2.8 ± 1.6 mm for length and 0.72 ± 0.28 mm for width. The surgical measurements (y) were 2.8 ± 1.7 mm for length and 0.72 ± 0.34 mm for width. Linear fits between x and y yielded R values of 0.93 (length) and 0.66 (width). Our previous study using MSCT had R values of 0.28 (length) and 0.48 (width). The average difference between each FPCT and corresponding surgical measurement was not significantly different from zero, whereas the results for MSCT were significantly different. FPCT can provide more accurate measurements of SCD than MSCT. Clinicians should consider using FPCT for imaging suspected SCD.

Robust Gate Driver on Array Based on Amorphous IGZO Thin-Film Transistor for Large Size High-Resolution Liquid Crystal Displays

Amorphous IGZO thin-film transistors (TFTs) in an etch stop layer (ESL) structure was processed on 2500 mm $\times $ 2200 mm size substrate. The fabricated devices exhibit enhancement mode characteristics, and excellent uniformity over large area. The presented good operational stabilities under both positive gate bias temperature stress (PBTS) and negative gate bias temperature stress (NBTS) tests can well meet the requirements for pixel switching. However, considering even threshold voltage shift under long term positive bias stress might affect proper operation of the gate driver on array (GOA), a design with a pulse gating scheme is proposed, consisting of 13 TFTs and 1 capacitor, to avoid long term continuous bias stressing of the TFT. With the proposed GOA design, a 32-inch QUHD ( $7680\times 4320$ ) high-resolution liquid crystal display (LCD) panel with a 7 mm wide bezel is achieved. The reliability of the GOA circuit is well proved through standard aging tests.

Fast switching, high contrast and high resolution liquid crystal device for virtual reality display.

Virtual reality-head mounted displays require a display with high resolution over 2000 ppi, super-fast response time and high contrast ratio for realizing super image quality at near-eyes. Several liquid crystal devices utilizing fringe-field switching (FFS) mode, having response times less than of half of conventional FFS mode, were proposed for this purpose. However, its contrast ratio is still less than 2000:1 because of intrinsic electro-optic characteristics of homogenous alignment mode and also realizing high resolution like 2000 ppi has some difficulty because twist deformation of liquid crystals can easily affect liquid crystal orientation near pixels. In this paper, we propose a vertically aligned liquid crystal device in which bend deformation occurs in a confined area by an oblique electric field, exhibiting 4 times faster decay response time than that of conventional FFS mode, higher contrast ratio over 5000:1, and pixel pitch less than 4 μm. The proposed liquid crystal device has a strong potential to be the main display for high-resolution virtual reality over 2000 ppi.

Pursuing High Quality Phase-Only Liquid Crystal on Silicon (LCoS) Devices

Fine pixel size and high-resolution liquid crystal on silicon (LCoS) backplanes have been developed by various companies and research groups since 1973. The development of LCoS is not only beneficial for full high definition displays but also to spatial light modulation. The high-quality and well-calibrated panels can project computer generated hologram (CGH) designs faithfully for phase-only holography, which can be widely utilized in 2D/3D holographic video projectors and components for optical telecommunications. As a result, we start by summarizing the current status of high-resolution panels, followed by addressing issues related to the driving frequency (i.e., liquid crystal response time and hardware interface). LCoS panel qualities were evaluated based on the following four characteristics: phase linearity control, phase precision, phase stability, and phase accuracy.

Length to diameter ratio effect on heat transfer performance of simple and compound angle holes in thin-wall airfoil cooling

Heat transfer coefficients on a flat plate surface downstream a row of simple and compound angle cylindrical holes are investigated using high-resolution thermographic liquid crystal technique. A variation of flow parameters including blowing ratio, and geometry parameters including compound angle and length-to-diameter ratio are examined. Blowing ratios (M) ranging from 0.3 to 2, length to diameter ratios (L/D) from 0.5 to 5, and two compound angle (β: 0°, 45°) are employed composing a test matrix of 70 test cases. Detailed local, spanwise averaged, and area averaged heat transfer coefficients hf/h0 are presented to illustrate the effect of length-to-diameter ratio and compound angle. The film cooling performance is also evaluated using NHFR method and Δφ method by combining adiabatic film effectiveness and heat transfer coefficient data. Results indicate that Δφ method has superiority in evaluating film cooling performance due to its direct reflection of temperature reduction by film protection.

High Performance Ultrathin SnO2 Thin-Film Transistors by Sol–Gel Method

Sol–gel processed ultrathin nanostructured SnO2 thin-film transistors were successfully fabricated on a SiO2/Si substrate without using a self-aligned monolayer or high- ${k}$ insulator, which may be unsuitable techniques for the commercial fabrication of complementary metal–oxide–semiconductors. The highest extracted field mobility was approximately 100 cm2/V $\cdot$ s. In addition, by controlling the SnO2 film thickness, we successfully increased the on/off current ratio to ~107. The electrical performance of the proposed transistors is sufficient for high-resolution liquid crystal or organic light-emitting diode displays, which require a high field-effect mobility (>10 cm2/V $\cdot$ s) and high on/off current ratio (>106). Ultrathin SnO2 is also a promising rare-metal-free starting matrix for ternary and quaternary alloys, showing promising electric properties.

Polyimide-free homogeneous photoalignment induced by polymerisable liquid crystal containing cinnamate moiety

ABSTRACTWe designed and synthesised a reactive mesogen (CRM) containing cinnamate moiety in the core and two acrylate groups at both ends. The structure was characterised by 1H NMR and FT-IR, and its liquid crystalline property was investigated by DSC and POM. The compound showed a nematic phase between 175.2 – 97.5 oC, followed by a smectic C phase between 97.5 and 57.9 oC during the cooling cycle. We proposed a fabrication method to achieve uniaxial homogeneous alignment of liquid crystals by irradiating the CRM-doped LC mixture in a sandwich cell of in-plane switching mode (CRM-IPS) with linearly polarised ultraviolet light. The results indicated that the CRM-IPS cell showed excellent initial dark state with a good alignment state, electro-optical performance and durability. This confirmed that the photo-induced alignment of LCs by CRM possesses outstanding alignment capability compared to the conventional rubbed polyimide alignment layer. We expect that this fabrication method is a promising candidate for cost-effective, green-manufacturing, and high-quality alignment method for the manufacturing of high-resolution liquid crystal displays (LCDs).

Real-Time Lens Based Rendering Algorithm for Super-Multiview Integral Photography without Image Resampling

We propose a computer generated integral photography (CGIP) method that employs a lens based rendering (LBR) algorithm for super-multiview displays to achieve higher frame rates and better image quality without pixel resampling or view interpolation. The algorithm can utilize both fixed and programmable graphics pipelines to accelerate CGIP rendering and inter-perspective antialiasing. Two hardware prototypes were fabricated with two high-resolution liquid crystal displays and micro-lens arrays (MLA). Qualitative and quantitative experiments were performed to evaluate the feasibility of the proposed algorithm. To the best of our knowledge, the proposed LBR method outperforms state-of-the-art CGIP algorithms relative to rendering speed and image quality with our super-multiview hardware configurations. A demonstration experiment was also conducted to reveal the interactivity of a super-multiview display utilizing the proposed algorithm.