Abstract: An optical system is provided that produces bright, high contrast head-up display images which are not adversely affected by the direct exposure to sunlight of the system's virtual image source. The optical system comprises a light source system which projects a focused light beam to a segmented, electronically-addressed polymer-dispersed liquid crystal ("PDLC")-type film, which serves as a primary image source. Selected segments of the image source are made transmissive while other selected segments scatter light. Accordingly, the portions of the focused light beam incident to transmissive segments are transmitted to form a real image, while the balance of the focused light beam is scattered. A stray light-blocking means, such as a lens/aperture combination, is employed to block the scattered light. The real image is projected onto an unsegmented, electronically-addressed PDLC-type film serving as an image screen.

Abstract: A new class of asymmetrical diphenyl-diacetylene liquid crystal compounds exhibit ideal properties for formulating eutectic mixtures suitable for infrared and microwave applications. The new class of liquid crystal compounds comprise asymmetrical nonpolar end groups. These compounds exhibit low melting points, wide nematic temperature range and low heat fusion enthalpy. Eutectic mixtures containing entirely diphenyl-diacetylene homologs using the new compounds have high birefringence, low viscosity and wide nematic range. These unique properties are especially advantageous when these mixtures are used in infrared spatial light modulators, high speed liquid crystal modulators and polymer dispersed liquid crystals shutters. The new asymmetrical diphenyl-diacetylene liquid crystal compounds comprise the following basic structure:R.sub.1 --C.sub.6 H.sub.4 --C.tbd.C--C.tbd.C--C.sub.6 H.sub.4 --R.sub.2wherein R.sub.1 and R.sub.2 are nonpolar end groups and R.sub.1 does not equal R.sub.2. R.sub.

Abstract: A liquid crystal is used as the phase modulating medium in a microwave phase modulating cell (20). Applied electric and/or magnetic fields transverse to the direction of wave propagation create a birefringence that changes the velocity of wave propagation and the index of refraction of the medium. The phase modulating cell (20) is used singly or in arrays to direct microwave beams.

Abstract: A composite material (20) has electrically conducting, elongated particles (22) dispersed in a liquid crystal (24). The index of refraction to microwaves is controllable by the application of a transverse electric field that aligns the liquid crystal material (24) and the particles (22). A phase modulating cell (31) is formed by placing the composite material (20) inside a microwave wave guide (32), with transverse electrodes (36) built into the sides of the wave guide (32). Another set of transverse electrodes or magnet pole pieces (30) can be provided to align the liquid crystal material (24) and the particles (22) in another direction, thereby switching the index of refraction of the cell (31). The particles (22) may be made of a ferromagnetic material, to permit magentic as well as electrical switching.

Abstract: A shaped voltage pulse is applied to a polymer dispersed liquid crystal (PDLC) cell to control its transmission characteristics. The voltage has an initially high level that substantially exceeds the PDLC's threshold voltage. The initial voltage duration is relatively short, and is followed by a gradual reduction of the voltage to a level less than the threshold voltage within a given time frame; the voltage is preferably reduced at a generally exponential rate. Fast response is obtained by setting the initial voltage substantially above the voltage level that corresponds to the desired transmission level in the steady state; the voltage decays from its initial level so that the PDLC transmission actually peaks at the desired range. The shaped waveform forces the PDLC to operate on a hysteresis curve along which the reduction in transmission is delayed as the voltage decays, thereby increasing the cell's optical throughput. The invention is particularly applicable to liquid crystal light valves.

Abstract: A high contrast display is provided by illuminating a polymer dispersed liquid crystal (PDLC) display panel through opposite edges thereof. Light is scattered out the front of the panel from non-activated areas of the PDLC in which the refractive indices of the liquid crystal and polymer matrix materials are mismatched. For a direct view transmission mode display, the rear of the panel is blackened so that activated areas of the PDLC in which the refractive indices of the materials are matched transmit edge-illuminated and ambient light and appear black. For a reflection mode display usable in combination with projection optics, the rear of the panel is provided with a mirror surface, and ambient light is prevented from reaching the panel.

Abstract: Liquid crystals are induced to assume a uniform tilted alignment in the absence of an applied field by treating the surface of a substrate to provide a desired tilted surface microstructure and free hydroxyl groups. A long chain alcohol having the formula ROH, where R is a carbon chain having at least about 6 carbon atoms therein, is chemically reacted with the tilted surface microstructure and the alkoxy groups derived therefrom are chemically bonded to the microstructure. Subsequently introduced liquid crystals assume a tilted-perpendicular alignment at a tilt angle of about 0.5.degree. to about 6.degree.. The liquid crystals exhibit a significantly greater photostability than has previously been achieved. The microstructure is preferably obtained by depositing sequential layers of SiO.sub.x at medium and shallow grazing angles, where x is from 1 to 2, with the substrate rotated 90.degree. between depositions.

Abstract: A polymer dispersed liquid crystal (PDLC) film, along with various fabrication methods that enable partial prealignment of the film's LC bubbles, are described. The film is formed with a matrix of liquid crystal bubbles. Individual liquid crystals within the bubbles are partially, but substantially less than fully, aligned in a given direction. Partial alignment is attained by the controlled application of an electric or magnetic field, or a mechanical flow, during photopolymerization. The resulting films retain the positive qualities of prior PDLCs, and in addition exhibit generally lower threshold and operating voltages, and can be used as tunable birefringent films in the infrared region.

Abstract: A method and associated means for producing simultaneous electrical representations of the electrical and acoustical (heart sound) activity of the heart, in which a pickup device and associated circuits produce a full wave rectified symmetrical heart sound signal annotated by pulses developed from the QRS wave of the electrocardiogram signal.The pickup device is designed to permit the direct (unbuffered) application of the pickup electrodes to the skin of the body and to provide a control of the associated circuits when not in contact with the body to shorten response times when the pickup device is placed in contact with the body.

Abstract: New nematic liquid crystal (LC) ester mixtures with relatively short average molecular lengths are made by including one or more binary sets of components which have identical, or nearly identical, molecular lengths. Undesirable solids solution phase effects are avoided by either utilizing appreciable asymmetry in the alkyl end groups or by combining LC esters of different classes.

Abstract: A number of alkyl and alkoxy-substituted ortho-cyanophenyl biphenylcarboxylate esters have been prepared for use as components for nematic liquid crystal mixtures which can be used in homeotropically aligned, field effect display devices or in dynamic scattering displays.These materials have large negative dielectric anisotropies and high birefringence.