Abstract: An electrically activated infrared filter utilizes a mixture of infrared absorbing dyes in liquid crystal which normally presents a substantial cross section of dye to absorb the infrared component of impinging light. Polarizing light to be parallel to the direction of liquid crystal alignment enhances the absorption of infrared components. In an alternative embodiment, a chiral additive to the liquid crystal solution increases the dye cross section density which, by absorption, attenuates a higher proportion of the infrared wavelengths. A predetermined voltage differential across the cell aligns the liquid crystal and dye molecules to the voltage gradient, presenting a substantially non-absorptive path to the infrared components of impinging light.

Abstract: A liquid crystal display assembly includes an untwisted nematic liquid crystal cell structure. The light transmittance of each pixel element of the assembly is a function of the pixel drive voltage. A phase compensating plate reduces the voltage necessary to permit switching, permitting compatibility with conventional thin film transistor (TFT) arrays but capable of greatly shortened response times. The configuration includes a combination linear polarizer and quarter wave plate which functions as a circular polarizer for blocking reflections from internal specularly reflecting surfaces within the liquid crystal display, thereby enhancing high ambient viewability.

Abstract: A combiner eyepiece with an enhancement imagery source and a collimating mirror is equipped with two oblique partially reflective mirrors. Both mirrors reflect some of the light impinging on their partially reflective sides and transmit substantially all of the rest of such light. The result is a collimated beam of light travelling toward the viewer along the viewing axis and expanded in vertical extent. This expanded vertical extent eases the requirement for the viewer to place his eyes in a precise location at the near end of the eyepiece. It also allows a smaller and lighter construction for an eyepiece where the vertical extent of the viewing area has been specified.

Abstract: An apparatus and method for increasing resolution and expanding the displayed field of view. The imagery is collimated and split into two paths by a partially reflective mirror set at an oblique angle to the image source. Either path may be blocked by a combination of polarizers and at least one controllable polarization shifting cell(s) (.pi.-cells). This mechanism allows one image source to supply, in alternating sequence, separate imagery to two separate but contiguous portions of a wide angle display. The two collimated image paths are merged about the viewing axis by a one way mirror before being recollimated at the device exit pupil.

Abstract: The efficiency of LC displays is improved by the use of a polymeric chiral nematic liquid crystal rear polarizer and reflective backlight housing which increases the net transmission of light and, at the same time, reduces the weight of the assemblage and increases battery life by utilizing lower levels of illumination. The polymeric chiral nematic liquid crystal can be a freestanding film or films, or can be supported by a single glass substrate. The liquid crystal polarizer can have a bandwidth sufficient to transmit electromagnetic radiation across the entire visible spectrum.

Abstract: A high-efficiency analog power amplifier is disclosed. The amplifier utilizes pulse-width-modulation ("PWM") signals to operate electrical switching devices coupled in series across a d.c. power source. A resonant circuit coupled to the transistors periodically places zero and non-zero voltage levels across each transistor. The frequency and width of the PWM signals are relative to the components of the resonant circuit--enabling each transistor to switch off and on only when zero volts appears across the transistor.

Abstract: A backlight system for liquid crystal device display is equipped with a dual lighting system for day viewing and night viewing. The day lighting system uses conventional fluorescent or incandescent lamps for full color display during daytime use. The night lighting system uses a lower intensity light source. The day lighting system is disabled while the night system is in use. The dual lighting system provides an extended dimming range compared to what would otherwise be available.

Abstract: Prepregs for producing ceramic-ceramic composite articles are prepared by impregnating a ceramic substrate with a liquid ceramic precursor material. By properly controlling the viscosity of the precursor material and the conditions of application of the precursor to the substrate, a prepreg which can retain the precursor may be obtained. The prepreg is suitable for shaping into a wide variety of geometries, and the ceramic precursor may be transformed into the corresponding ceramic matrix material by curing and conversion steps.

Abstract: A novel joint for connecting a closed composite adherend utilizes complementary scarf surfaces on the adherends and then bonds the adherends together. The angle of the scarf is determined by the materials used and the expected loads. Preferably, constant stiffness is achieved through the joint. In alternative embodiments, lap joint areas are included to create localized stress free zones. A method of creating the scarf surfaces utilizes a wrapping technique in which the edges of a lamina of composite material are prepared so as to provide a desired edge termination which permits each layer to be bonded to the adjacent adherend.

Abstract: An improved head up display utilizes a prism to direct the image of a display CRT upward to a semi-transparent combiner element, permitting a substantially smaller vertical profile of the overall structure. An image is presented to a viewer that appears to be at infinity and is indistinguishable from the exterior scene as viewed from that vantage point. In alternative embodiments, the display unit can utilize more than one prism with one or more combiner elements to increase the vertical height of the viewed image of the CRT while dramatically reducing the vertical space required for the display unit in an instrument panel.

Abstract: A method and apparatus for reducing the effects of binocular rivalry in a partially overlapped binocular image are disclosed. A false contour line is generated either electronically or mechanically along the border between the binocular and monocular images. This contour line reduces binocular rivalry in both convergent and divergent partially overlapped binocular displays.

Abstract: A clamp assembly includes a pair of segmented leg members that are tandem-operated to capture and hold a circuit board or module in and to chassis slots. The leg members each comprise a plurality of distinct wedge segment having complementary, confronting wedge surfaces.

Abstract: A backlight system for liquid crystal device display is equipped with a dual lighting system for day viewing and compatible with night vision systems. The day lighting system uses conventional fluorescent or incandescent lamps for full color display during daytime use. The night lighting system uses a light source which is either filtered to remove infrared and near infrared wavelengths or which is chosen from a class of sources which does not emit such wavelengths. The day lighting system is disabled while the night system is in use.

Abstract: A field sequential color head-up display system includes image generating means including a source of light of at least two different wavelengths. A color selective polarizing filter having first and second absorption axes, enables the passage of linearly polarized light of first and second colors. Optical retardation imposed by variable optical retarding means determines the color of the light transmitted by circular polarizing means. Image collimating means apply a generated image of selected colors to an image combiner placed in the line of sight between an observer and a scene, thereby superimposing a generated image over the scene visible to the observer. Holographic elements tuned to the selected wavelengths improve reflection of those wavelengths to the observer.

Abstract: Reinforced composite tubes having integral tapered ends are formed on mandrels which are tapered at each end. Reinforcement fabric is first conformed to the mandrel with at least one end of the fabric structure retaining an opening therein. The mandrel is disassembled and removed through the opening, and a matrix cured within the fabric to produce the desired composite. Usually, the fabric structure will be cured in an external mold with an inflatable mandrel inserted through the opening applying internal pressure.

Abstract: A connector system for joining a male tube to a female tube comprises an axially-split nut which extends across the region being joined. The female tube is externally threaded and mates with internal threads on one end of the axially-split nut. A shoulder formed in the other end of the axially-split nut engages a retaining ring formed on the male tube. A compressible seal ring is disposed between the end of the female tube and a second shoulder of the retaining ring. An external nut is placed over the axially-split nut to hold the entire assembly together and provide a radially compressive force on the seal ring. An axially compressive force can be provided by turning the female tube to draw the female and male tubes closer together.

Abstract: A seal and seat for ball valves is a circular, elastomeric open torus which is fitted between the ball element and the housing. The open torus has within it, a substantially "v" shaped spring that is fitted within the "u" shaped opening of the torus. In normal operation, the spring member is slightly compressed between the ball and the housing and the ball can "float" between a pair of substantially similar seals on the input and output sides of the ball valve, respectively.

Abstract: Aluminum oxide ceramic composite articles having high flexural and tensile strength are produced by introducing a liquid aluminum oxide precursor material into a ceramic reinforcement fabric, curing the precursor material at an elevated temperature, and converting the cured precursor material to an aluminum oxide ceramic by pyrolysis at temperatures which do not result in the degradation of the reinforcement material. Such ceramic composite articles are particularly useful for applications requiring a low dielectric constant and a high mechanical strength.

Abstract: An apparatus and method for providing optical switching or color selection capability uses cholesteric liquid crystals which reflect and transmit circularly polarized light and a variable wave retarder element together with phase reversing mirrors which recapture and recombine the reflected circularly polarized light. With the retarder element in a first state, first orientation circularly polarized light is completely transmitted and second orientation circularly polarized light is redirected. Alternatively, a color selection assembly is provided through the use of a combination of cholesteric light crystals in which light of a first color is given a first polarization orientation and light of a second color is given a second polarization orientation. Depending upon the state of the retarder either the first or second color is transmitted to a desired target.

Abstract: A helmet system includes a helmet shell and an energy-absorbing helmet liner that is constructed from an open-cell urethane foam impregnated with a room-temperature curable thermoset epoxy. The impregnated foam liner is inserted in the helmet shell, heated until the liner becomes deformably plastic, and placed on the head of a user, permitting custom-fitting of the helmet system that conforms to the contours of the user's head. When cured by cooling, the liner assumes a rigid construction that, by custom-fitting, repeatably aligns the helmet shell to the head of the user, and is crushable to absorb energy.