Herein, we report that liquid crystal displays (LCDs) such as TN (twisted nematic)-mode, TB (tunable birefringence)-mode, VAN (vertically aligned nematic)-mode, BN (bent nematic)-mode, and so forth, exhibit the reduction in the operating voltage and response times by doping the nanoparticles of inorganic substances such as MgO. These effects may be attributed to the modification of the physical properties of the liquid crystal host media in these LCD cells.

The viewing angle performance in IPS-LCDs has been greatly improved, by using two technologies. One is optical compensation technology using a biaxial film. The other is the newly developed IPS-Pro cell structure with its higher transmission efficiency. These technologies have been successfully introduced into the fabrication of 32-inch IPS-LCDs with a minimum contrast ratio of over three times that of the conventional and with a color saturation (area ratio to NTSC at CIE1931 xy chromaticity coordinates) of over 70 % at almost all viewing angles.

Tri-acetyl cellulose (TAC) films are widely used as a protective film for polarizers because it has high light transmittance, low birefringence, high moisture permeability, high uniformity and good curling property. This paper describes TAC film technologies, especially about the birefringence control of TAC film. Making use of the controlled birefringence, the TAC film comes to take an active role in optical compensation of LCDs as well as protection of polarizers. The out-of-plane birefringence of the TAC film can be controlled by additives, and the in-plane birefringence can be controlled by stretching. Coating a discotic material on the TAC film gives an additional optical compensation layer. With these technologies, we were able to develop an optical compensation film called WV film, which remarkably improves the viewing angle characteristics for TN-LCDs. Recently, we have developed and commercialized a new WV film for the OCB mode. OCB is known to have a very fast optical response time and promising as a next generation LCD-TV. The OCB-WV film has realized excellent viewing angle characteristics for OCB as well as a high on-axis contrast ratio. TAC film technologies open up possibilities of developing various types of optical compensation films suited for all LCD modes.

Electrically switchable diffraction gratings having periods as small as 5 μm and incorporating nematic LC confined within channels formed in poly(vinyl alcohol) (PVA) films were prepared and characterized. Gratings were produced by first using conventional photolithographic procedures to prepare reusable surface-relief grating molds from a common photoresist (SU-8). An aqueous PVA solution was then drop coated onto the mold and dried, The PVA film was subsequently peeled from the mold and pressed (channel side down) onto an indium tin oxide (ITO) coated glass slide. The channels were then filled with LC using capillary action. Finally, a second ITO-coated slide was pressed onto the backside of the PVA film, forming a polymer/LC grating cell. The diffraction efficiency of each grating was measured as a function of applied electric field strength using 488 nm light. Beam diffraction was greatest in the absence of the field and fell to zero for applied fields of less than 10 V/μm. These studies and atomic force microscopy results showed the LC channels to be ≈ 50-100 nm deep. Multiphoton excited fluorescence microscopy (MPEFM) was used to show the LC was oriented predominantly parallel to the long axis of the channels in the zero field state. Significant nonuniformity observed in the LC orientation was attributed to channel (PVA) wall roughness. Time-resolved MPEFM was used to monitor the LC reorientation process on submicron length scales. The local LC reorientation dynamics were also strongly perturbed by channel wall roughness.

We demonstrate a new method for simultaneously measuring the phase retardation and optic axis of a compensation film by using an axially-symmetric sheared polymer network liquid crystal (AS-SPNLC). The AS-SPNLC is a liquid crystal structure with radial director distribution and its phase retardation has a gradient change from center to edges. When overlaying a tested compensation film with a calibrated AS-SPNLC cell between crossed polarizers, the optic axis and phase retardation value of the compensation film can be determined. This method is particularly useful for those optical systems whose optic axis and phase retardation are dynamically changing.

We invented a new bend transition method using the twisted electric field in OCB mode LCD. And by introducing a pseudo-impulse display method which inserted a black period between two successive fields and scanning backlight system, the motion blur in TFT-LCD was drastically improved. In addition, we clarified the stability of the dynamic bend alignment when adopting the black insert driving method.

We would like to report here novel molecular design for electro-optic liquid crystal devices, i.e. catechol derivatives for reduction in threshold voltage and binaphthyl derivatives for blue phases with a wide temperature range. A threshold voltage of a nematic mixture consisting of a host liquid crystal and 10wt% of a catechol derivative, 1-{6-(3,4-difluorophenyloxy)hexyloxy}-2-{6-[4-(4-fluorophenyl)phenyloxy]hexyloxy}benzene, was markedly lower than that of the host LC. The U-shaped compound was found to induce larger dielectric anisotropy in the nematic phase of the mixture than the corresponding monomeric compound. Then, we prepared a homologous series of novel chiral dimeric compounds, (R)-2,2'-bis{6-[4-(2-(2-fluoro-4-butyloxyphenyl)pyrimidine-5-yl)phenyloxy]alkyloxy}-1,1'-binaphthyl. The binaphthyl derivatives with an even number of atoms in the spacers showed a chiral nematic phase, however, those with an odd number of atoms showed a blue phase in a relatively wide temperature range between the isotropic and smectic A phases. We discuss structure-property relationships in the U-shaped system.

Large tunable properties induced by the change of LC molecular orientation states can be expected for wider frequency region except for visible rays. Focusing on the millimeter wave (MMW) region, a novel measurement method for LC materials is investigated using the rectangular waveguide test cell and several commercially available nematic LC materials have been actually evaluated for V-band (50GHz-75GHz) and W-band (65GHz-110GHz) regions. Refractive indices for the direction parallel to the LC molecular orientation in the MMW region are almost the same with those in the visible rays, on the other hand the indices for the direction perpendicular to the LC orientation show a little larger values. Consequently, refractive index anisotropy which is the most important for the tunable LC devices reduces to be 1/2 through 1/3 of that in the visible rays. Although the larger refractive index anisotropy is desired for the better performance, the anisotropy of the usual LC materials is still large and the loss properties are fairly good. Based on the materials data, we have demonstrated the CPW type LC devices combining with an ITO glass substrate on it. Phase and amplitude changes of the transmitted MMW by the LC driving are investigated considering the influences of some device parameters.

We investigate the fabrication of holographic polymer dispersed liquid crystals (H-PDLCs) for use as switchable laser cavities. H-PDLCs are liquid crystal and polymer dispersions used in grating applications for displays, optical communications and optical security. By controlling the pitch of the H-PDLC and the laser dye used, we are able to fabricate a tunable laser. H-PDLCs were made in both reflection and transmission modes to vary the method by which lasing action occurs. The dye-doped H-PDLCs were pumped with nanosecond pulses from a laser with emission at 532 nm and a power of approximately 6 mJ. Lasing action was observed using a spectrometer from the H-PDLC grating; peak wavelengths occurred over a range of wavelengths, depending on the dye used, with the full width of the emission peaks approximately 6-8 nm at half maximum. The lasing action can be turned on and off by the application and removal of an electric field due to the properties of an H-PDLC. Furthermore, we investigate multidimensional architectures and quasicrystal symmetries for lasing applications. Applications for these cells include use in small-scale portable devices requiring a tunable laser source.

Unique liquid crystal (LC) spatial light modulators (SLM) are being developed for foveated imaging systems that provide wide field-of-view (FOV) coverage (±60° in azimuth and elevation) without requiring gimbals or other mechanical scanners. Recently, a transmissive-SLM- based system operating in the visible (532 nm) has been demonstrated. The LC SLM development is addressing implementation issues through the development of high figure-of-merit (FoM) LC materials and transmissive high-resolution SLMs. Transmissive SLM operation allows the foveated imaging configuration to be very compact using a very simple lens system. The reduction in the size, weight and cost of the imaging optics and in data acquisition/processing hardware makes the foveated approach attractive for small platforms such as unmanned airborne vehicles (UAVs) or missile seekers.

Recently, there have been increasing interests in the study of liquid-crystal-based devices for application in the submillimeter wave or THz frequency range. In this paper, we present recent progress in liquid crystal THz optics from our group. Using time-domain THz spectroscopy, we have determined the complex indices of refraction of nematic liquid crystals, 5CB, PCH5 and E7 from 0.2 to beyond 1 THz. Significantly, the birefringence of 5CB and E7 are found to be as large as 0.2 at THz frequencies, while the absorption is negligible. Electrical-field and magnetic-field-controlled birefringence in LC were also investigated. A tunable room-temperature THz phase shifter using magnetic-fieldcontrolled birefringence in nematic 5CB gives a phase shift as large as 108° at 1.0 THz. Phase shift exceeding 360° at 1 THz, an important milestone, was realized by using a sandwiched LC (E7, Merck) cell as thick as 3 mm. The magnetically tuned LC phase shifter served as key components in a two-element tunable LC Lyot filter. The tuning range of the filter is from 0.388 to 0.564 THz or a fractional tuning range of ~ 40%. Our work clearly demonstrates the potential of liquid crystal devices for THz applications. Finally, we will present initial works on control of enhanced THz transmission through a metallic hole array with nematic liquid crystals. Our work clearly demonstrates the potential of liquid crystal devices for THz applications.

We developed a broad band achromatic linear polarization switch for visible and near infrared radiation. The achromatic switch is based on a twisted nematic cell filled with a dual-frequency nematic material. The switch is capable of fast switching linearly polarized light between two orthogonal directions with a switching time in the millisecond range.

Molecular orientation states in the liquid crystal (LC) cell can easily be deformed and change their properties by applying low driving voltage with low power consumption. Those features are also attractive for the various functional devices in the wider frequency regions such as a millimeter wave (MMW), although only the optics applications are well investigated as the display application is put the head of them. Waveguide systems are well known as an excellent way to make a low loss transmission circuit in the ultrahigh frequency region such as microwaves and MMWs, and then the LC devices utilizing the waveguide have been proposed so far. However, the planar waveguide has gathered many attractions for the wider functionality by integration. We adopt here a coplanar waveguide (CPW) substrate to prepare the planar type of LC MMW devices combined with an ITO glass substrate. Since the ITO film acts as a floating electrode to simplify the electrode structure, LC molecules can be driven by applying the voltage only to the CPW substrate. Unfortunately, since the ITO electrode close to the CPW decreases the transmission of the MMW, the molecular orientation effects related with the electrode structure are very important to minimize the electrode area. We prepare the transparent LC cell which has exactly the same electrode structure with the CPW LC cell, and observe the molecular orientation states in detail by using a polarization microscope. It becomes clear that only the narrow area above the signal electrode of the CPW affects strongly to the phase change of the MMW propagation in the CPW type LC cell.

Porous thin films of dielectric materials have been deposited using e-beam evaporation onto substrates held at highly oblique angles (> 80^o), coupled with simultaneous computer controlled substrate motion about two independent axes. This technique, known as glancing angle deposition (GLAD), enables the formation of shaped, isolated nanostructures, including vertical posts, zig-zags, and both helical and polygonal spirals, which exhibit chiral optical properties. GLAD films form the backbone of liquid crystal (LC) hybrid optical materials and devices, and afford key advantages. The porous nature of the GLAD structures allows LCs to uniformly penetrate the film and modify its optical properties. Addition of LCs to GLAD films improves the properties of the films by reducing optical scattering, enhancing transmission, and accentuating existing chiral and linear optical anisotropies. Further, by mixing a dichroic dye with the LCs, polarization selective optical properties can be introduced into the film which can be used to augment the functionality of GLAD films. It has been found that addressing hybrid GLAD films with an electric field reorients the LCs, allowing one to switch the optical properties of the composite film. This behaviour extends to LCs mixed with dichroic dye, allowing one to switch the selective polarization properties with an applied voltage. Using results based on spectroscopic ellipsometry, we will examine the optical properties and switching behaviour of LC/dichroic dye hybrid GLAD films and discuss how the results allow one to infer the alignment of LCs in GLAD films, as well how the addition of dichroism to the film affects the selective transmission of both linearly and circularly polarized light.

We report on the effect of placement of nucleobase units, thymine or N6-(4-methoxybenzoyl)-adenine onto the ends of the mesogenic and fluorescent core: bis-4-alkoxy-substituted bis(phenylethynyl)-benzene (AA and BB type monomers). While the addition of these bulky polar groups significantly reduces the range of liquid crystalline behavior, mixing two complementary nucleobase-containing monomer units together yields stable thermotropic liquid crystalline phases. Here, we focus on the effect of non-stoichiometric mixing of AA + BB monomers. Hydrogen bonding is shown to play an important role in the formation of these LC phases consistent with the formation of oligomeric or polymeric hydrogen bonding aggregates. Differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) have been used in our studies, revealed greater stability of LC phase formation for the 1:1 mixture.

A prerequisite for a wide market acceptance of 3D displays is the ability to switch between 3D and full resolution 2D. In this paper we present a robust and cost effective concept for an auto-stereoscopic switchable 2D/3D display. The display is based on an LCD panel, equipped with switchable LC-filled lenticular lenses. We will discuss 3D image quality, with the focus on display uniformity. We show that slanting the lenticulars in combination with a good lens design can minimize non-uniformities in our 20" 2D/3D monitors. Furthermore, we introduce fractional viewing systems as a very robust concept to further improve uniformity in the case slanting the lenticulars and optimizing the lens design are not sufficient. We will discuss measurements and numerical simulations of the key optical characteristics of this display. Finally, we discuss 2D image quality, the switching characteristics and the residual lens effect.

The recent Bistable Nematic (BiNem^(R)) LCD technology presents long term bistability, high level passive matrix multiplexing and high optical quality. The BiNem device, based on anchoring breaking, needs specific low anchoring strength materials - alignment layers and liquid crystal mixtures. We present here our approach to develop nematic mixtures with wide enough temperature range and low zenithal anchoring energy.

We have successfully developed and commercialized an optical compensation film for OCB-LCD mode (OCB-WV film). OCB-LCD mode is known to have a very fast optical response time and makes next-generation fast-response LCD-TVs possible and free from image blurring. The OCB-WV film, which has a structure composed with TAC (triacetyl cellulose) film and PDM (polymerized discotic material) layer, can realize the wide viewing angle of OCB-cell. In order to provide the best performance of OCB-cell, we optimized an optical parameter of not only WV film but also OCB cell by a numerical simulation. In this paper, we will discuss a concept of its optimization, which provide excellent results of a numerical simulation.

Usually when optically pumped, dye-doped cholesteric liquid crystals (CLC) generate circularly polarized laser light from both directions of the lasing cell along the cholesteric helical axis. In reality, only the laser light from one direction can be utilized. In this paper, we demonstrate a simple method for doubling the laser output of a dye-doped CLC laser. The extracted laser output is nearly doubled. In experiment, we use a 6-ns, frequency-doubled Nd:YAG laser to pump the CLC lasing sample at ~20 degree incident angle. A reflector: a metal mirror or a cholesteric liquid crystal reflector is placed on the backside of the CLC sample. The reflector is in proximity contact with the CLC sample and the laser action occurs only in one direction. For the metal mirror reflector, the two orthogonal circularly polarized beams are mixed by incoherent superposition. While for the cholesteric liquid crystal reflector (same handedness as the lasing cell and highly reflective of the laser light), the enhanced laser output could also be achieved due to further stimulated amplification but the output is dominated by a single polarization state. For both cases the laser output is associated with a loss of coherence. Hence a nearly unpolarized CLC laser or a partially coherent CLC laser with nearly doubled output intensity is obtained.

Modes dispersion relations of multilayered anisotropic waveguides are presented and investigated for the case of nematic liquid crystal waveguide layer. The multilayered waveguide modes are investigated using the analytic 4x4 propagation matrix approach. Dispersion relations are derived for the TE and TM confined waves for variety of orientations of the dielectric ellipsoid. For the case of coupling via a shallow grating layer where guided wave resonance is excited, it is shown that for the purpose of mode determination, this analytic approach agrees very well with rigorous diffraction calculations. Dependence of the modes on the anisotropic layer parameters is investigated particularly for liquid crystal layer parameters where thin layers are important both for single mode operation, higher switching speed, reduced absorption and scattering losses. Liquid crystals response to an applied electric field usually produces nonuniform molecular director profiles that are shown to have strong effect on the guided wave.

High performance video places severe demands on playback system and display device resources. Motion playback errors such as irregular motion playback and image breakup are common, making accurate measurement of motion critically important for device selection and system tuning to ensure the desired viewing experience. Direct observation of the actual displayed image (screen capture) is the only way to perform a complete end-to-end system test that accounts for all possible sources of motion errors, including original video capture, compression/decompression, playback system performance, and display device operation. Unfortunately for the development of measurement techniques, the fundamentally different ways that different display technologies present imagery can easily confound sensitive measurement techniques, producing measured playback performance differences across multiple display technologies such as LCD (liquid crystal display), plasma, CRT (cathode ray tube), and DMD (digital micromirror device) that are disproportionately large compared to the actual differences (if any) seen by a human viewer. Cross technology measurement tools are necessary to ensure the validity of measures across multiple technologies. The methods being used include a combination of test materials (both selected live video clips and synthetic clips), capture technique (including control of capture rate, triggering, and timestamping), and analysis. This paper describes these methods, then gives several illustrative examples of the use of these methods by the project. The NIST Motion Image Quality Measurement project uses a combination of quantitative measures and subjective analysis to evaluate motion imagery and to identify the factors that determine overall performance. The NIST project has conducted tests to measure (1) perceived image quality and (2) motion image interpretability, as a function of factors including compression, video motion and other scene content, playback system performance, and frame rate. Tests have been conducted using a variety of playback systems with different levels of performance, and using a variety of display technologies.

Laser-based projection displays have long attracted interest because of the multiple advantages (expanded color gamut, high resolution, longer lifetime, etc.) expected from lasers as compared to lamps. However, most of these advantages have been largely negated by the significant cost, size, and cooling requirements associated with lasers, and their inability to produce red, green, and blue colors in the same platform. In this paper, we review a new, laser array technology based of frequency-doubled, semiconductor, surface-emitting lasers. The key features of this technology, such as demonstrated multi-Watt output for rear-projection TVs, power levels scalable with the number of emitters, speckle suppression due to multi-emitter array, and a low-cost and compact design are discussed in detail.

Physical properties and alignment performance of biphenyl and terphenyl negative dielectric anisotropic liquid crystal (LC) compounds are investigated. Results show biphenyl compounds align well in homeotropic LC cells and the alignment of terphenyls are relatively poor. We have developed a new method to align these high birefringence LC compounds. Adding a few percent of positive dielectric anisotropic or nonpolar LC material not only enhances the contrast ratio but also improves the overall figure-of-merit. Molecular modeling and experimentation are demonstrated to support this concept.

Dual paraboloidal reflectors (DPR) can couple more light into small etendue projection systems. The imaging property of DPRs at two conjugation focal points and their peripheral areas has been investigated using ASAP simulation and observation. The result confirms that the DPR can produce one to one image at the conjugated focal points, which is the reason why dual parabolic reflectors are beneficial. In the periphery area, the image is distorted. The image distortion was analyzed theoretically and the results agree with observation. This imaging property was used to develop a new method of locating the focal points of DPRs accurately. A new lamp manufacturing procedure and a pilot line were setup and tested. The coupled lumen efficiency has been increased by 13%.

Photoluminescent nanostructured thin films have been fabricated using physical vapour deposition and the glancing angle deposition (GLAD) technique. Precision controlled substrate motion and oblique incidence (>75^o) enable the fabrication of a variety of 3-D morphologies including vertical posts, helical (chiral) columns and chevrons. Scanning electron microscopy and X-ray diffraction were used to characterize the film nanostructure. These experiments focussed on the chiral morphology which exhibits intriguing polarization behaviour such as selective transmission of circularly polarized light and circularly polarized photoluminescence. Helical films of Y₂O₃:Eu and Alq₃ were fabricated with thicknesses in excess of 2 μm and densities nominally 60% of bulk. Transmission spectroscopic ellipsometry measurements were used to determine the degree of selective transmission of polarized light through the samples. The degree of circular polarization for the photoluminescent light emitted from helical films was measured with the use of a quarter waveplate and linear polarizer. Polarized photoluminescence efficiencies were consistent with the observed selective transmission of circularly polarized light through the films. The use of GLAD to control the nanoscale morphology of the films allows for the spectral location and strength of these polarization effects to be easily and accurately selected.

Conventional parallax barrier display systems have demerits such that the barrier cuts resolution of a screen in half. This paper describes the development of a desktop dual views display using polarizer slits for collaborative tasks. The polarizer slits enable observers to view full screen high resolution images, and this proposal can solve the resolution problem of the conventional system. Moreover, the authors propose the thin display using dual LCD panels. This compact display has two LCD panels to present stereo views and to control polarization. It has twice the 3D image resolution, because the LCD image plane can multiplex images with horizontal and vertical polarization to display stereo views.