Abstract: This invention provides a phase modulator comprising an electro-optically rotatable smectic liquid crystal half-wave retarder in combination with a cholesteric liquid crystal circular polarizer. Rotation of the half-wave retarder varies the phase delay of the modulator. A polarizing interferometer is provided utilizing the phase modulator of this invention in combination with a second cholesteric circular polarizer and a linear polarizer. A tunable Fabry-Perot resonator which does not require ordinary mirrors is provided utilizing the phase modulator of this invention in combination with a second cholesteric circular polarizer.

Abstract: A system for determining a distance to a target object or a displacement of a target object monitors electrical characteristics of a semiconductor laser aimed at the object. Light emitted from the laser is reflected from a surface of the object back into the laser. The amount of reflected light reaching the laser affects electrical characteristics of the laser. Because the amount of reflected light reaching the laser depends on the distance to the target object, the electrical characteristics of the semiconductor laser provide an indication of the distance to the target object. Also, a change in the electrical characteristics can be used to determine an amount of displacement of a target object. A system embodying the invention could also include an optical detector array which can be focused on a target object by monitoring electrical characteristics of one or more semiconductor lasers.

Abstract: This invention provides split-element liquid crystal polarization interference filters in wide-field, bandpass, cut-on, cut-off and notch filter embodiments. The split-element filters of this invention comprise a polarization interference stage defined by a pair of polarizers. Disposed within the stage are a center retarder, and first and a second split-element retarder, the split-element retarders having equal retardances and positioned in series with and on either side of the center retarder. The retarders can be liquid crystal variable retarders or can be fixed retarders used in combination with liquid crystal retarders. Double split-element filters in passive and tunable embodiments are provided comprising, within a polarization interference stage, a center retarder, an inside pair of split-element retarders and an outside pair of split-element retarders.

Abstract: This invention provides achromatic compound retarders, achromatic polarization switches, and achromatic shutters using the liquid crystal compound retarders. It further provides achromatic variable retardance smectic liquid crystal retarders. The achromatic compound retarder of this invention comprises a central liquid crystal retarder unit and two outer retarders positioned in series with and on either side of the liquid crystal retarder unit. The liquid crystal retarder unit comprises either (1) a rotatable smectic liquid crystal half-wave retarder or (2) first and second liquid crystal variable retarders having retardance switchable between zero and half-wave. The outer retarders have substantially the same retardance and orientation. Design equations determine the retardance of the outer retarders and their orientation relative to the central retarder to obtain a particular achromatic retardance for the compound structure.

Abstract: The present invention provides a high brightness subtractive color filter formed by an electro-optic modulator positioned between two retarder stacks. The second retarder stack echoes the first retarder stack, having the same sequence of retardances but in reverse order and having an orientation rotated with respect to the first stack. The modulator changes the apparent orientation of the second stack so that, in a first switching state of the modulator the two stacks cooperate in filtering the spectrum of input light, and in a second switching state they vanish, leaving white light. Two or more stages can be used in series, each stage providing independent analog control of a primary color. One preferred embodiment eliminates internal polarizers between stages, thereby providing a full-color display with only two neutral polarizers. Hybrid filters can be made using the filter of this invention in combination with other active or passive filters.

Abstract: This invention provides achromatic liquid crystal compound retarders, achromatic polarization switches, and achromatic shutters using the liquid crystal compound retarders. It further provides achromatic variable retardance smectic liquid crystal retarders. The compound retarder of this invention comprises a central liquid crystal retarder unit and two external passive retarders positioned in series with and on either side of the liquid crystal retarder unit. The liquid crystal retarder unit comprises either (1) a rotatable smectic liquid crystal half-wave retarder or (2) first and second liquid crystal variable retarders having retardance switchable between zero and half-wave. The external passive retarders are equal in retardance and orientation to each other. Design equations determine the retardance of the external elements and their orientation relative to the central retarder to obtain a particular achromatic retardance for the compound structure.

Abstract: A programmable hologram generator comprises a layered structure of a pixelated VLSI chip, a reflective ferroelectric liquid crystal that is physically disposed on the VLSI chip, and a photorefractive crystal that is physically disposed on the liquid crystal. The VLSI chip is controlled by a computer wherein holograms are digitally stored. The reflective state of the individual pixel areas of the liquid crystal are controlled or selected by this computer control of the VLSI chip. A desired hologram is written into the photorefractive crystal by a reference beam that illuminates the photorefractive crystal, and by an illumination beam that is reflected from the selected pixels of the liquid crystal and thereafter interferes with the reference beam. The hologram that is written into the photorefractive crystal is a function of the control of the reflective state of the pixels of the liquid crystal, as this reflective state is in turn controlled by the pixels of the VLSI chip.

Abstract: A retarder stack for transforming at least partially polarized light includes a first retarder and a second retarder. The first retarder has a first retardance and a first orientation and the second retarder has a second retardance and a second orientation both orientations with respect to the partially polarized light. The first retardance, first orientation, second retardance, and second orientation can be arranged to yield the desired polarization transformed light which includes a first spectrum and a second spectrum. The polarization of the first spectrum and the polarization of the second spectrum can be made orthogonal to each other. The polarizations can be linear or elliptical. If the polarization transformed light is linear, the directions of polarizations are different and in one case can be made perpendicular.

Abstract: A retarder stack for preconditioning at least partially polarized light for input to a modulator includes a first retarder and the second retarder. The first retarder has a first retardance and a first orientation with respect to the partially polarized light and the second retarder has a second retardance and a second orientation with respect to the partially polarized light. The first retarder and second retarder are oriented with respect to each other and the first retardance and the second retardance are selected such that the light output from the second retarder includes a first portion of light and a second portion of light which, if input to a modulator, would be modulated differently. Hence, the retarder stack can be used to precondition light for input to a modulator such as an electro-optic, magneto-optic or other type of modulator.

Abstract: A method and apparatus for assembly of liquid crystal cells with a thin (<4 pm), uniform (.+-.100 .mu.m) cell gap. The method can be used for the assembly of either individual or multiple liquid crystal cells on a single substrate. The method uses a photo-definable polymeric resin as both an edge seal and a spacer and has several important steps: spin-coating defines the cell gap, patterning defines the cell structure, and thermocompression bonding provides adhesion. The method for assembling liquid crystal cells having a thin, uniform cell gap, comprises the steps of: diluting a photo-definable polymeric resin with a solvent; applying the diluted photo-definable polymeric resin on a substrate; patterning the diluted photo-definable polymeric resin by selective exposure to a light; and selectively removing portions of the diluted photo-definable polymeric resin based upon exposure to the light resulting in a resin pattern.

Abstract: A method for making an electro-optic device or electro-optic display system having enhanced performance over conventional flat-panel displays, wherein a planarizing polymeric resin layer is spin-cast on a flat-panel backplane containing pixel circuitry. The spin-cast layer is cured to provide a flat backplane. Vias are opened in the cured polymeric resin to each pixel. Metal is deposited to fill the vias and to form a confluent, overlying metal layer on the upper surface. The metal layer is patterned and etched to form individual mirrors over each pixel. The metal acts as both a switchable electrode and as a high aperture, highly reflective mirror over each pixel. Electro-optic devices which may be made using such a process are also disclosed.

Abstract: An apparatus and method for detecting anomalies morphologically detecting regions of interest. The apparatus and method include a region of interest (ROI) detection unit which morphologically detects anomalies in two dimensional input images or morphologically detects regions of interest based on structuring elements which can be set by a user using a modified hit and miss transform which includes a thresholding feature. The thresholding feature makes it possible to vary how much the shape of features within the input images can deviate from the shape of structuring elements and still be detected as a region of interest. One application of this involves detection of abnormal cells in a cervical Pap-smear.

Abstract: This invention provides polarization-independent optical filters that are Fabry-Perot filters. The inventive filters incorporate a phase modulator within the FP cavity and two quarter-wave plates, one on either side of the phase modulator, in the cavity. The quarter-wave plates are perpendicular to each other and oriented at .+-.45.degree. with respect to the optic axis of the phase modulator. A variety of phase modulators including those that incorporate nematic and smectic liquid crystal optical modulators can be employed in these FP filters. The filters of this invention are particularly useful in fiber optic systems and in telecommunications applications at 1550 nm.

Abstract: This invention provides achromatic liquid crystal compound retarders, achromatic polarization switches, and achromatic shutters using the liquid crystal compound retarders. It further provides achromatic variable retardance smectic liquid crystal retarders. The compound retarder of this invention comprises a central liquid crystal retarder unit and two external passive retarders positioned in series with and on either side of the liquid crystal retarder unit. The liquid crystal retarder unit comprises either (1) a rotatable smectic liquid crystal half-wave retarder or (2) first and second liquid crystal variable retarders having retardance switchable between zero and half-wave. The external passive retarders are equal in retardance and orientation to each other. Design equations determine the retardance of the external elements and their orientation relative to the central retarder to obtain a particular achromatic retardance for the compound structure.

Abstract: This invention provides a phase modulator comprising an electro-optically rotatable smectic liquid crystal half-wave retarder in combination with a cholesteric liquid crystal circular polarizer. Rotation of the half-wave retarder varies the phase delay of the modulator. A polarizing interferometer is provided utilizing the phase modulator of this invention in combination with a second cholesteric circular polarizer and a linear polarizer. A tunable Fabry-Perot resonator which does not require ordinary mirrors is provided utilizing the phase modulator of this invention in combination with a second cholesteric circular polarizer.

Abstract: This invention provides a liquid crystal polarization handedness switch, and optical devices employing the handedness switch in conjunction with optical elements which are sensitive to the handedness of incident light. The handedness switch receives unpolarized light and converts it into circularly polarized light with switchable handedness. In combination with cholesteric circular polarizers, switchable color filters are provided. The color filters of this invention include the analogous x-y polarization switch combined with colored partial polarizers. The liquid crystals employed in the color filter of this invention can include SmC*, SmA*, antiferroelectric, DHF, achiral ferroelectric and twisted nematic liquid crystals.

Abstract: The present invention provides optical modulators which comprise aligned chiral smectic liquid crystal cells within an optical resonance cavity. The cavity configurations include symmetric and asymmetric Fabry-Perot etalons. The liquid crystal cells can be planar- or homeotropically-aligned and can be discrete state or analog cells. The device configurations of the present invention provide discrete or continuous optical modulation of the phase, intensity, and wavelength of elliptically polarized light, without requiring polarization analyzers. The modulators are optically or electronically addressable in single pixels or arrays of multiple pixels. Certain homeotropically-aligned cells are provided as an aspect of this invention, as are certain variable retarders comprised of planar-aligned cells in combination with birefringent elements.

Abstract: This invention provides split-element liquid crystal polarization interference filters in wide-field, bandpass, cut-on, cut-off and notch filter embodiments. The split-element filters of this invention comprise a polarization interference stage defined by a pair of polarizers. Disposed within the stage are a center retarder, and first and a second split-element retarder, the split-element retarders having equal retardances and positioned in series with and on either side of the center retarder. The retarders can be liquid crystal variable retarders or can be fixed retarders used in combination with liquid crystal retarders. Double split-element filters in passive and tunable embodiments are provided comprising, within a polarization interference stage, a center retarder, an inside pair of split-element retarders and an outside pair of split-element retarders.

Abstract: This invention provides analog phase modulators comprising smetic liquid crystal cells wherein the layers are specifically not aligned perpendicular to the cell walls. The layers are either tilted with respect to the substrate or are in a chevron structure. Application of an analog electric field perpendicular to the cell walls bends the molecules in an analog fashion in a plane not parallel to the cell walls and thereby provides analog phase modulation of incident light. Analog phase modulation can not be directly provided by the surface-stabilized smectic liquid crystal cells known in the art, nor can analog tilting of SmC* liquid crystals be achieved. This invention further provides Fabry-Perot devices containing these analog phase modulators within the resonance cavity. The filter of this invention is optimally suited for wavelength-division multiplexing in photonic networks. It has high throughput, large tuning range, high resolution, and high modulation speed.

Abstract: This invention provides smectic liquid crystal cells with lateral electrodes. The effective change in refractive index with field-induced tilting of the liquid crystal molecules is increased by providing an angle between the direction of propagation of light and the direction of the molecular directors at zero applied field. For homeotropically aligned liquid crystals this is accomplished by inclining the incident light beam at an oblique angle to the device surface. For tilted layer cells the liquid crystal layers are tilted and the light can impinge at normal incidence. This invention further provides Fabry-Perot filters utilizing lateral electrode liquid crystal cells.