The phase behavior of liquid crystalline side group polymethacrylates with azo-chromophores in the mesogens was investigated. Layer periodicities (monolayers or bilayers) of the smectic phases depend on the spacer to tail length ratio. For the polymer where the layer periodicity changes from a monolayer to a bilayer two orthogonal smectic monolayer phases S_B and S_A1 are metastable. After annealing in the S_B phase a crystallization occurs. On annealing in the S_A1 phase a transformation into a bilayer S_C2 phase takes place. An arrangement of the mesogens in the S_A1 and S_C2 phases is proposed assuming steric hindrance of the side groups caused by the attachment to the polymethacrylate backbone and ataractic permanent dipolar-induced dipolar forces of neighboring side groups. To prove the results also samples with different dipole moments in the mesogens (ester- and amide- instead of azo-units) and in the tail groups (fluorinated) were studied.

Full color images have been demonstrated on a high frame rate, binary, ferroelectric liquid crystal (FLC) display or spatial light modulator (SLM). This display consists of binary surface stabilized ferroelectric liquid (SSFLC) crystal over a custom foundry CMOS silicon VLSI (FLC/VLSI) backplane and provides a new alternative to current well established display technologies. Many issues have been considered to enhance the optical quality of these displays such as the post-processing of the foundry silicon to achieve a high optical flatness and pixel fill factor; with improved liquid crystal alignment. Optimization of electrical addressing schemes and color illumination for video display purposes have been investigated resulting in recommendations for future developments.

The wide range of electro-optical properties such as electrically adjustable optical activity, birefringence and scattering make liquid crystals (LC) suitable for defined alteration of amplitude, phase polarization and spectral composition. The method of incoherent optical space frequency analysis (OSFA) on the basis of liquid crystal light modulators is shown. In an optically addressed image processing camera the objects, which have to become classified, are projected onto an LC-SLM. The reflective SLM gets read-out incoherently. As a 2D- radiator an electronically addressed 'transient-nematic' LC modulator is used. A photo- multiplier serves as detector. It is mathematically exactly proven that the measured intensities are corresponding to the surface integrals of the Fourier transform. In a microscope variant the principle gets translated into action by the way that a telescopic projection of a FLC matrix-display takes place over a condenser and micro-objective into the exit pupil plane. The change-over to incoherent OSFA allows a simple realization of a Fourier processor for detection of particle-size distribution. For this purpose a high speed nematic LC modulator with log-ring structure is incorporated into the aperture stop of the condenser. The coherent OSFA is used in evaluation of particle image velocimetry and laser speckle photographs. The autocorrelator with an optically addressable LC-SLM allows, due to the two 2D-Fourier transforms, a high speed and accuracy.

A frame change data driving scheme (FCDDS) for ferroelectric LCD(FLCD) of matrix- addressing is developed which uses only positive voltages for the row and column waveforms to achieve bipolar driving waveforms on the FLCD pixels. Thus the required supply voltage for the driver chips is half that of the conventional driving scheme. Each scan line is addressed in only twice the switching time (tau) (minimum response time of FLC) so that this scheme is suitable for high duty ratio panels. In order to meet this bistable electro-optic effect of FLCD and zero net dc voltage across each pixel of the liquid crystal, turning on and turning off pixels are done at different time slots and frame slots. This driving scheme can be easily implemented using commercially available STN LCD drivers plus a small external circuit or by making an ASIC which is a slight modification of the STN driver. Both methods are discussed.

Experimental variables affecting the morphology of holographically written Bragg gratings in polymer dispersed liquid crystalline composite systems are discussed. The spatial anisotropic photo-crosslinking of a multifunctional acrylate monomer results in periodic regions of phase separated LC droplets. These films have many electro-optic applications owing to the fact their refractive index profiles can be modulated. Low-voltage high resolution scanning electron microscopy (LVHRSEM) was used to investigate the morphology of these films due to the very small LC domain sizes formed. Specifically, the morphology is discussed in terms of the rates of LC diffusion parallel to the grating vector, and the relative rates of nucleation and subsequent gelation. Using micrographs, the effect of writing intensity, LC content, and chain extender concentration is examined first in uniformly illuminated (flood lit) samples and then in transmission gratings. Elimination of the chain extender increases the gelation time relative to the nucleation time resulting in larger LC domains. The effect of increasing the Bragg spacing on the phase separation behavior is also examined.

We describe the properties of diffractive gratings induced in nematicliquid crystal thin films by fringing electrostatic fields induced by interdigitated ITO electrodes. The index of refraction variation produced by fringing fields gives rise to strong diffraction with resolution constrained only by the available lithography.

We present a detailed discussion of the fundamental mechanisms for recently observed persistent photorefractive effects in nematic liquid crystal films. A theoretical analysis of the various space charge fields, dielectric torques, and estimates of their magnitudes and critical assessment of their roles in the observed holographic grating formation process are presented. In dye- or Fullerene C₆₀-doped films, it is observed that the induced director axis and refractive index grating could persist indefinitely. Furthermore, these stored gratings can be electrically switched on and off at ms-subms speed.

We induced grating structures in polymer films containing small liquid crystal droplets. The grating formation is due to the thermal effect of an intensity grating caused by the interference of two Ar-laser beams. A light-induced grating-like modulation of material properties is stored after the exposure. It can be erased by heating the hole sample. The diffraction efficiency of the grating can be modulated by external electric fields.

A phase separation under an applied electric field (PSUF treatment) in LCPC relaxes the energetic stress for dynamic operation of its device. Both higher dynamic response time and less hysteresis in dark gray scales which are significant issues in LCPC are achieved, since its treatment can control the interface between liquid crystal and matrix polymer without the damage to scattering in off state and contrast ratio. It is based on the morphological characteristic which is caused by the first step: a segregation of liquid crystal and ordering process of the liquid crystal under an applied field, and the second step: polymer/pre-polymer precipitation to maintain the early ordering of segregated liquid crystal. The essential structure of LCPC caused by the characteristic phase separation process, is characterized with confocal fluorescence microcopy, which also supports its process mechanism.

The presence of hysteresis in transmittance-voltage characteristics of liquid crystal mixed with polymer (LCMP) has been the main cause for the residual image of LCMP display devices. This hysteresis is regarded to originate in the interaction between liquid crystal material and matrix polymer. The molecular motion of the matrix polymer of LCMP is varied systematically by changing the monomer and photo-initiator content. The hysteresis of LCMP decreases as the elastic modulus of matrix polymer decreases. It has been found quite effective to lower the elastic modulus of matrix polymer in reducing the hysteresis of LCMP.

The paper presents an objective lower bound for the discrimination of patterns and fine detail in images on a monochrome LCD. In applications such as medical imaging and military avionics the information of interest is often at the highest frequencies in the image. Since LCDs are sampled data systems, their output modulation is dependent on the phase between the input signal and the sampling points. This phase dependence becomes particularly significant at high spatial frequencies. In order to use an LCD for applications such as those mentioned above it is essential to have a lower (worst case) bound on the performance of the display. We address this problem by providing a mathematical model for the worst case output modulation of an LCD in response to a sine wave input. This function can be interpreted as a worst case modulation transfer function (MTF). The intersection of the worst case MTF with the contrast threshold function (CTF) of the human visual system defines the highest spatial frequency that will always be detectable. In addition to providing the worst case limiting resolution, this MTF is combined with the CTF to produce objective worst case image quality values using the modulation transfer function area (MTFA) metric.

This work describes a new optical inspection method, based on the investigation of the combined space-frequency representation of the scattered field. Samples of the sliding window spectrum are measured optically, and then are processed using modern signal processing techniques, like signal reconstruction from Gabor expansion coefficients using the Zak transform, and phase recovery from amplitude only data, using projection onto constraints set algorithm. Computer simulations and experimental results show that the new method is capable to describe accurately very shallow phase objects, even when their dimensions are smaller than the diffraction limit of the optical setup.

Applications of the Voltage Imaging^TM technique in testing active arrays used in AMLCDs have been widely discussed. Voltage Imaging^TM is well known for its simplicity in interfacing with active array panels, and its superior voltage measurement accuracy and repeatability. It is also known for having broad test applicability for many AMLCD panel design technologies, such as TFT, MIM, diode and panels with integrated drivers. This paper briefly discusses a recent improvement related to the application of Voltage Imaging^TM for L-contact panel testing. As the panel manufacturers are trying to reduce the manufacturing cost, the number of panels on one substrate also increases which, in several cases, leaves only enough room to add ESD protection shorting rings on two of the four sides of a panel. Since this is the trend of the industry, a methodology that can be employed to test L-contact panels with Voltage Imaging^TM is presented in this paper.

The method of Black Beam^R Interferometry, which was developed for inspection of glass substrates in LCD manufacturing, is extended in order to achieve a detailed description and classification of defects and other features on the surface under inspection. With a properly arranged detection system, not only a high defect detectability is provided, but also the ability to discriminate between the up or down defects (bumps or pits) in addition to the possibility of measuring the defect geometry (for large defects or structures) and the equivalent defect volume. The method is described and the results of simulations and experiments are presented.

Low voltage operated display devices require thin fluorescent screens of 3 to 4 micrometer, consist of 0.1 to 2.0 micrometer size phosphor particles. Fine grain phosphors are synthesized by hydrothermal, combustion and sol-gel processes. In sol-gel process, the pores in dried gels are often extremely small and the components of homogeneous gels are intimately mixed. The surface area of powders produced from sol-gel is very high, leading to a lower processing temperature. Stable sols of Y(OH)₃, Al(OH)₃ and RE(OH)₃ were prepared by passing respective nitrates through an ion exchange column. Stiochematric amounts of these sols were mixed to obtain YAG:RE (0.001 to 5.0 m/o) phosphors. DTA/TGA analysis showed weight loss corresponding to the loss of water molecules and oxidation. XRD of the samples fired at 1200 degrees Celsius showed only YAG phase. SEM studies revealed that the phosphor particles are nearly spherical in shape and uniform in size. Emission spectra from these samples excited by 200 to 5000 eV, exhibited a number of lines in blue, green and red regions corresponding to Tm³⁺, Tb³⁺ and Eu³⁺ transitions. Introduction of inhibitors (Li⁺) and sensitizes (Pr³⁺) appears promising in improving the morphology as well as the efficiency of the phosphors.

Patterned orientation of liquid crystals is a new emerging area and offers new promises for data storage with high spatial resolution and long memory. We describe below recent advances in producing patterned orientation of liquid crystal molecules. In one of the techniques developed by us, the patterned orientation of liquid crystal molecules is caused by bulk- induced alignment of liquid crystals by photo-polymerization using linearly polarized UV- light. In this process, the local macroscopic orientation direction of the liquid crystal molecules is controlled by the polarization direction of the linearly polarized UV-light and patterns when a high degree of spatial resolution could be recorded optically. In yet another newly discovered technique, the pattern orientation of liquid crystal molecules is controlled by the polymer layer substrate cured thermally. In this process, the aligning polymer layer substrate is placed in contact with the patterned metal mask surface and cured thermally by a unidirectional heat source. The stored information is useful for aligning liquid crystal molecules. This process of aligning liquid crystals has given rise to new possibilities of using them for storing information permanently with a high degree of spatial resolution of approximately 30 - 40 micrometers.

Molecular electron transfer memory (METM) module with shift register based on a polymer storage medium with a photoinduced electron vector transfer reaction is considered. The method for computing such a memory and structural circuit, operation algorithm, the delay parameters of the memory based on two VLSI chips and a homogeneous molecular storage medium are presented. Temperature regime operation of the molecular electron memory module is investigated. The calculation method and the mode of the heat dissipation are suggested. METM module based on the single dynamic memory chip with V-riffle storage capacitor, charged by electron-molecular medium is regarded.

The equations for the light-induced Freedericksz transition threshold of the initial homeotropic director configuration are obtained and the solutions to them are found in analytical or numerical forms. Due to the surface charges the threshold value increases if the nematic static dielectric anisotropy is positive or decreases in the opposite case. The threshold value depends also on the director anchoring energy, Debye screening length and cell thickness. For each given value of the light wave electric vector which stabilizes the initial director configuration the critical value of the surface charge density is found at which this configuration is growing unstable.

A few scattering effects in liquid crystals are considered for display devices, based on liquid crystal image converters. These effects allow us to eliminate the requirements to the polarization of readout light in such systems.

This work is dedicated. to studies or pbyslcal, electrooptical and. modulation properties ot llqull crystal materials on the base or mixtures ot strong- and weak-polar nematic materials with small-percents dopant at ctholesterlne esters In order to they application as optical active medium In display devices on the base or nematic—cholesteric phase transition.

The temperature-concentration dependence of the field hysteresis loop ((delta) U) in nematic- cholesteric mixtures was researched. The matrices were the mixtures of cianobipheniles in which helical structure was created by the addition of optically active dopants (0.4 ... 2.5 weight%) or addition of non-liquid crystal material BIXH-3. It was shown that the magnitude of (delta) U decreases with the increasing of a temperature. The maximum of the (delta) U can be attained by the change of the concentration of the dopant in mixtures.

Analog liquid crystal display as liquid crystal cell in which one of transparent electrodes has variable thickness and/or width is considered at this paper. Suggested display can be wide used for measuring oftemperature, magnetic field, etc.

Recent interest in chiral smectic A liquid crystals is driven in part by their potential for development as fast, analog electro-optic devices. Chiral smectic A liquid crystals exhibit electroclinic behavior, characterized by continuously variable, electrically controllable molecular tilt. Consequently, these materials are suitable for applications where gray-scale capabilities are required. Moreover, new electroclinic liquid crystals have been synthesized which exhibit large tilt angles which may permit fabrication of devices with very good contrast ratios. However, when viewed between crossed polarizers, electroclinic liquid crystals have often been found to exhibit a stripe texture due to a field-dependent deformation of the bookshelf geometry. The degree of deformation appears to increase with the tilt angle and the stripes become more pronounced. X-ray measurements support the picture of a triangular wave deformation of the layers. These observations indicate that the observed stripe deformations may significantly limit the performance, particularly the achievable contrast ratio, that devices made from these materials might attain. In this paper, the optical and electro-optical properties of electroclinic liquid crystals are investigated to gain insight into the structure of stripe domains and to relate these findings to the potential performance of electroclinic liquid crystal devices.

The synthesis and properties of a novel ferroelectric cyclic siloxane oligomer are reported. The properties of the oligomer are compared with those of a linear siloxane polymer and its unattached side group consisting of the same mesogenic moiety as in the cyclic siloxane oligomer. The ferroelectric and electroclinic response times as well as the tilt angles of the cyclic material are found to be similar to those of the monomer while the spontaneous polarization is comparable to that of the linear siloxane polymer. These studies constitute the first detailed comparison of the ferroelectric properties of a cyclic siloxane oligomer and a linear siloxane polymer.