This PDF file contains the front matter associated with SPIE Proceedings Volume 7232, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We focused on several technical approaches to flexible liquid crystal (LC) display in this report. We have been developing flexible displays using plastic film substrates based on polymer-dispersed LC technology with molecular alignment control. In our representative devices, molecular-aligned polymer walls keep plastic-substrate gap constant without LC alignment disorder, and aligned polymer networks create monostable switching of fast-response ferroelectric LC (FLC) for grayscale capability. In the fabrication process, a high-viscosity FLC/monomer solution was printed, sandwiched and pressed between plastic substrates. Then the polymer walls and networks were sequentially formed based on photo-polymerization-induced phase separation in the nematic phase by two exposure processes of patterned and uniform ultraviolet light. The two flexible backlight films of direct illumination and light-guide methods using small three-primary-color light-emitting diodes were fabricated to obtain high-visibility display images. The fabricated flexible FLC panels were driven by external transistor arrays, internal organic thin film transistor (TFT) arrays, and poly-Si TFT arrays. We achieved full-color moving-image displays using the flexible FLC panel and the flexible backlight film based on field-sequential-color driving technique. Otherwise, for backlight-free flexible LC displays, flexible reflective devices of twisted guest-host nematic LC and cholesteric LC were discussed with molecular-aligned polymer walls. Singlesubstrate device structure and fabrication method using self-standing polymer-stabilized nematic LC film and polymer ceiling layer were also proposed for obtaining LC devices with excellent flexibility.

We report on unique flexible Reflex^TM displays based on bistable, reflective, cholesteric liquid crystal display technology. Reflex displays are attractive for numerous applications because of the low power consumption and paper like reflective color. As the possible applications grow for flexible, reflective displays the new methods to manufacture these displays, such as web processing, also become important. We will report on several unique display types such as a pressure induced writing display and a switchable color electronic skin display. In addition, the current status of traditional Reflex displays will be discussed.

We demonstrate fast-switching electro-optical films (EOFs) based on polymer encapsulated liquid crystal and carbon nanotube. EOFs are made by using the polymerization-induced phase separation method with an initially homogeneous mixture of a pre-polymer, liquid crystal and small amount of carbon nanotubes (CNTs). The effects of the concentrations of CNTs and liquid crystals on the electro optical properties of the EOFs are studied. The rise times for the CNTcontaining EOFs is around 200 μs at 6V/μm, while the fall time is around 30ms at 6V/μm twice as fast as that of the EOF without CNTS. The dielectric measurements show that the relaxation frequency of the EOFs increases with the increase of CNT doping, indicating the decrease in droplets size. The morphology of EOFs is confirmed with SEM morphological studies. With the increase of the concentration of CNT or liquid crystal, the threshold voltages of the EOFs are decreased and the response times are faster.

If it is the exception that proves the rule, liquid crystalline blue phases prove the typical properties of liquid crystals: The latter are ordered fluids, which show birefringence because of the orientational order of their molecules. However, blue phases are optically isotropic in spite of local orientational order. Many liquid crystals form - similar to usual liquids - spherical or at least almost spherical droplets. But blue phase (BP) droplets can show facets that resemble crystal shapes. Typical liquid crystals appear in the bulk as translucent liquids. In contrast, blue phases show brilliant colors (due to Bragg scattering) - a remarkable property, which has probably lead to the discovery of liquid crystals some 120 years ago. Since then, blue phases attracted high academic interest but were not expected to be very useful, because the temperature range of their existence was rather small. But fortunately, there are very useful exceptions: During the last few years, systems have been developed which exhibit blue phases stable within temperature intervals as large as 50 °C. Even a promising prototype of a blue phase display was presented, last year.

Recent experimental and theoretical results that link the phenomenon of dielectric relaxation in nematic liquid crystals (NLCs) to their dynamics and fast electro-optical switching are presented. Namely, we illustrate that the dielectric torque acting on the uniaxial nematic liquid crystal depends not only on the present value of the field and the present orientation of the director, but also on the prehistory of these two parameters. The resulting "dielectric memory" effect leads to a spectacular but counter-intuitive effect: director relaxation during the "switch-off" stage can be accelerated if instead of the abrupt vertical back edge, one uses a voltage pulse with a non-instantaneously vanishing back edge. The acceleration effect can be enhanced with a short high voltage pulse at the end of the "switch on" process.

This study describes an electrically tunable two-dimensional (2D) liquid crystal (LC) holographic polarization grating (HPG). It is a twisted nematic (TN) grating array, which is obtained by orthogonally overlaying two crossed 1D polarization holograms. A 1D polarization hologram has a rotating linear polarization pattern, generated by the interference of two orthogonal circularly (OC) polarized beams on a substrate that is coated with an azo-dye doped PVA layer. The images under a polarized optical microscope (POM) and the diffraction patterns from the 2D grating are simulated using the Jones matrix and a Fourier transformation. The experimental results agree with the simulated results. This work represents a substantial advance toward the realization of highly functionalized passive optical devices in which both the beam propagation direction and the polarization state can be controlled in two dimensions.

In this work, three-dimensional manipulation of multiple defects and structures is performed in the framework of holographic optical trapping approach using a spatial light modulator. A holographic optical tweezers system is constructed using a liquid crystal spatial light modulator to generate multiple optical traps. We optimize the tweezers setup to perform polarization-sensitive holographic optical trapping and then explore properties of optical trapping in thermotropic liquid crystals and compare them to the case of isotropic fluids. One of the major challenges complicating the quantitative measurements in these fluids is the anisotropic nature of the liquid crystal medium, which makes the tight focusing of the laser beam difficult and considerably weakens optical trapping forces. Using liquid crystals with low birefringence allows us to mitigate these artefacts. Optical trapping forces and the trap stiffness are first calibrated for different laser powers using viscous drag forces. This is then used to probe inter-particle and defect-particle interaction forces as well as to characterize tension of line defects in the bulk of liquid crystals.

In this study, we irradiated homogeneously aligned films of an azotolane liquid-crystalline polymer with a single femtosecond (fs) laser pulse. Upon irradiation of the single pulse, the change in ▵n was induced by destruction of due to destroy the homogeneous alignment of the azotolane moieties was induced. The estimated value of the change in ▵n was >0.2, and the response time was about 400 ns. When the experiment temperature was below glass transition temperature, the change in alignment induced by the pulsed irradiation was preserved without a thermal relaxation. On the other hand, the changed alignment completely recovered to the initial state with an increase in temperature.

The photorefractive effect of polymer-stabilized ferroelectric liquid crystals (FLC) was investigated. Two-types of monomers, a liquid crystalline monomer and a photoconductive monomer, were mixed with an FLC and the mixtures were photopolymerized in the ferroelectric phase. The polymer-network was formed in the FLC medium and a polymer-stabilized FLC was obtained. The polymer-stabilized FLC exhibited monostable switching properties. The photorefractive effect was evaluated by a two-beam coupling experiment. It was found that the photorefractive effect was strongly dominated by the preparation condition of the polymer-stabilized FLCs. Large gain coefficients were obtained in the photoconductive-polymer-stabilized FLCs.

A series of novel side chain liquid crystalline polyacrylates with pendent chiral groups was synthesized. Copolymerization of the monomers was carried out and the physical properties of the copolymers were investigated. Two miscible chiral compounds were also synthesized and used as chiral dopants to induce cholesteric liquid crystalline phases of polymers. The optical properties of the induced cholesteric liquid crystalline polymers were investigated by using UV-vis spectrometer. The appearance and the color variation of the polymer films before and after UV irradiation were also investigated.

In this study, the structure and dynamics of a liquid crystalline semiconductor dioctylterthiophene system, 8-TTP-8, were examined by molecular dynamics simulations. We especially focus on the melting transition from the crystal to the liquid crystal smectic G phase. Simulations of the rotational autocorrelation functions show that the transition is characterized by the onset of rotation around the long molecular axis, while maintaining a hexagonal packing within the smectic layers. This implies that the stepwise decrease of the carrier mobility at the melting transition point may be caused by this rotational disordering. We also found the molecular diffusions (at a rate of D~0.9x^-10m²/s) in the simulated SmG phase. All these characteristics of the simulated SmG phase, including the molecular diffusions, are similar to those of a rotator (plastic crystal) phase.

Flexible display devices are widely and extensively studied for using the applications such as smart cards, PDA, head mounted displays and all kinds of mobile display because of their lighter weight, thinner packaging, and flexibility. However, it has some obstacles such as mechanical stability and tight adhesion of two plastic substrates. In this presentation, we will suggest a new bonding technologies with rigid spacers and bonding materials, which will serve mechanical stability and good adhesion strength. The micro-contact printing method is used to place bonding material on the rigid spacers that may be easily applicable to roll-to-roll fabrication processes. The performances of prototype samples fabricated will also be demonstrated by this technology.

In order to improve the approach of the conventional LCD colored image display that has been using color filter, this research is to lead a unique innovative design by using three colors bank scrolling backlight. The backlight scrolling uses Light-Emitting-Diodes (LEDs) to replace the conventional cold cathode fluorescent lamp for fleetly light alternating between Red, Green, and Blue. Images with bank segments can be displayed in terms of RGB colors in time series. According to the human persistence of vision effect, a colorful image can be demonstrated. The advantages of this three color bank scrolling can provide a cost saving because there is no color-filter of the display, resolution tripling with RGB on the same pixel, and abundant in color saturation for the selection of dedicating wavelength LEDs color mixture. Practically, this research contents the experiments of three color bank scrolling, a building up of the prototype for backlight system, optics adjustment for a proper color mixture. The results of this research show the system not only could displace the color filter but also triple the resolution. Consequently, the system is practicable and can be proposed as a new innovation to LCD industry.

Holographic photopolymerization, such as used to form holographic polymer dispersed liquid crystals (HPDLCs), has the advantage of combining the desirable processing properties of polymers with a periodic distribution of an electrically tunable medium (LC). Herein we describe laser oscillations resulting from distributed feedback in fieldmodulated, 2-D H-PDLC photonic crystals. Compared to results of lasing from pyrromethene 597 in 1-D H-PDLCs, the linewidth of the laser action decreases by at least a factor of four and the lasing wavelength is electrically tunable over 5 nm. The 2-D H-PDLCs consist of LC columns within a polymer matrix that were created by interference of four writing beams on the sample cell. Two configurations were studied; one comprising a reflection grating orthogonal to a transmission grating (in-plane) and the other from two orthogonal transmission gratings (out-of-plane). Given that the lattice spacing was the same for both samples, the lasing wavelengths were similar; however the polarization dependence on lasing threshold varied by a factor of three for the in-plane configuration and electrical switching resulted in bimodal lasing. The out-of-plane geometry showed no polarization dependence on lasing threshold and the lasing blue-shifted with applied electric field.

Multi-wavelength lasing in a dye-doped cholesteric liquid crystal (CLC) cell is demonstrated. By adding oversaturated chiral dopant, the multi-photonic band CLC structure can be obtained with non-uniform chiral solubility. Under appropriate excitation, multi-wavelength lasing can be achieved with a multi-photonic band edge CLC structure. The number of lasings can be controlled under various temperature processes. Nine wavelength CLC lasings were observed simultaneously. The wavelength range covers around 600-675nm.

Precision patterned optical films are key components of today's display technologies, serving as brightness enhancement films, diffuser films and patterned light guides, to name a few. In recent years, much attention has been given to methodologies for patterning optical films with nanoscale precision at the scale and economics required by the Flat Panel Display industry. With this work, we report a platform technology, Pattern Replication In Non-Wetting Templates (PRINT®), for polymer-tool based manufacturing of patterned optical films for the display industry. By using Fluorocur® mold materials, the PRINT® (Pattern Replication In Nonwetting Template) technology enables low cost manufacturing of precise micro and nanoscale features with single nanometer precision from virtually any material.

Liquid crystal devices are suitable for spatial light modulators, since their half-wave voltage is only a few volts and can be driven directly by CMOS ICs. In this paper, we describe liquid crystal GRIN lens with segmented ITO patterns. So ITO patterns are like zone plates. ITO segments are connected with smaller, highly resistive ITO links that produce voltage drops between the larger ITO segments. The voltage distribution causes a phase distribution across the modulator that can be generated by a simple 3-terminal input. Variable focus range of from plus-minus 150mm to infinity with 1.64mm diameter and good image quality is achieved.

Liquid crystal (LC) devices for Photonics applications is a hot topic of research. Such elements begin to appear in Photonics market. Passive elements for fiber optical communication systems (DWDM components) based on LC cells can successfully compete with the other elements used for the purpose, such as micro electromechanical (MEM), thermo-optical, opto-mechanical or acousto-optical devices. We have already successfully fabricated certain prototypes of the optical switches based on various electrooptic modes in ferroelectric and nematic LC materials. The electrooptical modes used for the purpose included the light polarization rotation, voltage controllable diffraction and fast switching of the LC refractive index. Use of photo-alignment technique pioneered by us makes it possible to develop new LC fiber components. Almost all the criteria of perfect LC alignment are met in case of azo-dye layers. We have already used azo-dye materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. We have already used the photoaligning materials to align LC mixtures in small cavities, such as the holes and tubes of photonic crystals, having size of 1 μm and less and obtained excellent LC orientation inside the tubes by photoalignment. The prototypes of new LC efficient Photonics devices, such as optically rewritable LC waveguides and voltage controllable diffraction gratings are envisaged. The polarization controllers, polarization rotators, variable optical attenuators and other passive LC optical elements for fiber communication networks are under way.

Liquid crystal (LC) cells with plural latent images have been proposed for security devices. The photo crosslinkable polymer surface is irradiated with unpolarized UV light through the photo-mask and subsequently rubbed. The LC aligns parallel and perpendicular to the rubbing direction on the UV irradiated and unirradiated surfaces, respectively. A guest host mode LC cell is prepared using our alignment patterned substrates. Double-faced optical writing is also successfully demonstrated in the guest host mode LC cell by exposing from both sides of the cell with unpolarized UV light. The LC cell is uniformly colored under the natural ambient light. Two latent images can individually be visualized when a polarizer is replaced in front of and behind the cell. The third latent image is obtained as a result of logical operation for two patterned images when the LC cell is set between the polarizer and analyzer. We can see three domains, that is, transparent, colored and black domains. Each part shows the result of the logic operation of two images, that is, "AND", "NOT" and "EOR". The alignment patterned LC cell is also utilized as a key cell to visualize the latent information in the LC cell.

We have developed a general ray-tracing method in the geometrical-optics approach which enables the modeling of in general inhomogeneous liquid crystal configurations. In this manuscript, we discuss two prominent examples in which we calculate the optical properties of two liquid crystal configurations. We first present simulations of a liquid crystal-based electro-optical device that enables a switching effect due to a back reflection phenomenon. In these simulations, we exploit the optical properties of a liquid crystal with a special Freedericksz alignment. Secondly we present preliminary results of the optical properties of a liquid crystal-based optical element that can actively control guiding and extraction of light. A promising application of such a device can be found in for example beam control devices for lighting applications or applications that require local dimming and highlighting.

Advances in front projection technology, particularly imager chips and illumination sources, are heralding a whole "New Era" of sub-500 lumen projectors that are significantly smaller and/or cheaper than the classical (500+ lumen) models available up to now. Liquid crystal and MEMS technology imager chips are being joined by MOEMS scanner chips, and lamps are being joined by LEDs and lasers. These New Era models are finding myriad applications, from wall-powered toy and gaming projectors (for which price, not size, is the key consideration) and personal projectors that can be used for a variety of vertical markets, to a host of viewing needs that can be filled by tiny battery-powered pico projectors.

A wedge shaped flat panel projection display can be made by combining a slab waveguide with a tapered "wedge" waveguide sector. The sudden angle transition between the flat slab-waveguide surface and the tilted wedge-waveguide surface, sometimes called the 'kink' in a conventional wedge flat panel screen design, causes the rays which are incident at the flat slab-waveguide surface just before the kink to overlap with the rays which are incident at the tilted wedge-waveguide surface just after the kink. This paper identifies the 'kink' problem by using the reverse ray tracing technique, where parallel rays are traced from the wedge-waveguide surface back to the receiving end of the slab-waveguide. We propose a parabolic curved transition region to be inserted between the slab and the wedge waveguide as the solution to this problem, as the parabolic curved surface replaces the 'kink' with a smoother angle change between the flat and the tilted waveguide surfaces, to avoid the rays overlapping. The parabolic curve is designed to introduce collimation for the rays projected from a point light source to avoid inducing convergence or divergence to the rays which are incident at the parabolic curved surface. A thick wedge design consisting of the slab, parabola and wedge waveguides is demonstrated in this paper which shows how the ray overlapping problem for a conventional slab-wedge waveguide design can be solved.

The wedge display is a piece of wedge-shaped waveguide. Each time a ray reflects in the wedge, its angle relative to the opposite side increases so that the critical angle is eventually reached and the ray emerges. Therefore, how far the ray travels before emerging is determined by its injection angle. As a kind of projection display, the wedge-shaped waveguide is a natural fit to holographic projection. In this paper, a new type of holographic display based on the wedge panel is reported. The hologram projected into the wedge is generated by computer with a Spatial Light Modulator (SLM 1280*1024), illuminated by a He-Ne laser. A method taking advantage of reverse ray tracing to correct keystone distortion of the wedge display is introduced. By setting special patterns on the screen of the wedge panel and replacing the projector at its thick end with a camera, keystone distortion information is recorded. The predistortion process adds the distortion pattern from the camera to the original input images. Images with less distortion are shown on the screen after the predistortion process.

In order to produce future generation micro-projection systems that can function independently or in conjunction with small personal communication devices lasers are the preferred source of illumination over LEDs. Lasers are much brighter and require less power than LEDs allowing for larger screen sizes and smaller battery requirements. In order to illuminate the spatial light modulator used in the micro-projection system micro-optical elements are used within the illumination path of a projector system to shape the RGB laser sources. Due to the diffractive nature of the optical elements and the high coherence of the lasers a speckle pattern is produced in the final image reducing the overall image quality. Diffractive diffusers are typically used in combination with micro-lens arrays in a time varying fashion in an attempt to reduce the spatial coherence of the laser sources and hence reduce the speckle. Previous reduction techniques have successfully used pseudo-random hadamard matrix diffusers to greatly minimize the contrast of the pattern. This paper examines new reduction methods involving diffractive diffusing elements and presents measurements in the reduction of speckle contrast for each technique.

Laser is an ideal illumination light source for liquid crystal projection displays in terms of source Etendue and polarization. In order to make a conversion from a circular Gaussian laser beam profile to a rectangular uniform distribution on the microdisplay, a double side microlens array has been proposed as a homogenizer, and a cylindrical lens is exploited for shaping the aspect ratio of illumination pattern. The design and simulation based on scalar diffraction theory have shown that two identical lenslet arrays on each side of a thin plastic substrate with a lateral shift of half diagonal pitch can convert laser beam into a uniform square illumination at a specified near field. The pitch and curvature of the lenslet are major parameters for modifying the illumination distance, area and uniformity. The proposed lenslet array will provide an economical solution for the illumination optics of laser based light valve projector due to its regular and circular lenslet profile.

During the last years, a trend to replace commonly used short arc lamps in projection systems with alternative light sources is seen. Next to LEDs for low light output products, lasers try to enter the projection area and have the ambition to infiltrate from low (picoprojection) towards high light output systems (digital cinema). One of the benefits of lasers is their narrow spectral bandwidth. As a consequence, the display can have a very large colour gamut, if the lasers are carefully selected. Another benefit is the very low intrinsic étendue of the source. One can imagine using less complex, more efficient, smaller but more powerful optical systems. This not only for scanning projectors, but also for 2D light valve based projectors (LCOS, LCD, DLP). In addition, the limited lifetime of lamps has serious impact on a system's cost of ownership, and puts light source reliability/lifetime high on the list of priorities for future developments. For this reason, Barco entered the European FP6-project OSIRIS, in a subtask where a 300 lm laser projector demonstrator has to be developed and evaluated. So far, we found out that next to obvious challenges such as laser cost and laser power, the most critical issue regarding image quality is speckle interference which counteracts the beneficial nature of the light source. This phenomenon is a direct consequence of the coherent nature of a laser and cannot be solved as easily as is often claimed. We will describe laser speckle in the context of laser projection and the theoretical limits of several reduction techniques. This leads to guidelines which can make laser projection worth considering.

To investigate the effect of cholesteryl pendant groups on the phase behaviors of related copolymers, a new cholesteryl-containing liquid crystalline monomer was synthesized and copolymerized with an achiral comonomer in various molar ratios. The phase diagram and optical properties of the synthesized copolymers containing the cholesteryl pendant group were studied and compared with those of the monomer mixtures. The layer-like arrangement of the smectic mesophase with different monomeric compositions of copolymers was investigated using an X-ray diffraction analyzer. The dependence of the reciprocal central reflection wavelength on the mole fraction of the chiral monomer for monomer mixtures and copolymers was investigated.

LEDs have been prevailing rapidly in the field of general lighting owing to the enhancement of output power and emission efficiency. We developed luminaires for general lighting using color LEDs. We also fabricated the lighting system for large size holograms by controlling the luminous flux of the arrayed LEDs. Multiple number of high brightness LEDs with honeycomb arrangement were used as a light source with red, green, and blue LEDs. The resolution and color of the reconstructed image from the color hologram were characterized quantitatively by using the luminaire.

A technique displaying arbitrary images based on phase contrast imaging with phase optimization method is proposed. Phase optimization is performed in a way similar to the iterative Fourier transform algorithm which considers the phase shift and the aperture size of the phase contrast filter. We test and compare two phase shift cases, which are π/2 and π, in optimization process. The phase contrast filter at the Fourier plane is implemented using photopolymer whose optically induced refractive index change has a linear dependence on the illuminating light intensity. As a result, the proposed method is capable of displaying arbitrary images with enhanced quality and high light efficiency in phase contrast projection field. Also when the phase contrast filter has π phase shift, the enhancement of the output intensity image is more obvious.