Abstract: A liquid crystal optical processor is configured in various applications, including a liquid crystal optical switch, polarization independent variable optical attenuator, wavelength selector switch, optical multiplexer and demultiplexer, tunable filter and flexible optical add drop multiplexer. The optical processor is generally configured to include a deposited metal gasket moisture barrier bonding two opposing substrates each having a spacer layer to accurately control cell gap thickness. The optical processor may be temperature insensative and be configured in one or more pixel configurations. The optical processor may include integrated subwavelength optical gratings. It may also include an integrated thermal sensor and heater deposition layer sandwiched between or deposited on at least one or both opposing substrates.

Abstract: This invention relates to a number of components, devices and networks involving integrated optics and/or half coupler technology, all of which involve the use of electronically switchable Bragg grating devices and device geometries realized using holographic polymer/dispersed liquid crystal materials. Most of the components and devices are particularly adapted for use in wavelength division multiplexing (WDM) systems and in particular for use in switchable add/drop filtering (SADF) and wavelength selective crossconnect. Attenuators, outcouplers and a variety of other devices are also provided.

Abstract: An optical switch is provided in which a cell comprised of photopolymer dispersed in a liquid crystal sandwiched between two transparent plates is first recorded with a grating utilizing two plane wave laser beams interacting at an angle. This grating is permanently established in the cell such that when the cell is illuminated the incoming beam is diffracted in accordance with the spatial frequency of the grating. When an electric signal is applied across the cell, the refractive index of the liquid crystal matches that of the photopolymer due to the molecular orientation of the liquid crystal and no diffraction occurs because the grating formed in the liquid crystal is temporarily erased or over written. The liquid crystal cell therefore becomes transparent with the application of the electrical signal. Switching occurs by whether or not the grating is present or not, which is in turn dependent upon whether or not there is an electrical signal applied across the cell.

Abstract: A complex diffraction device, which is excellent in designability, easy in setting the diffraction angle, adaptable to size increase, and easy to handle by adding a diffraction function resulting from an uneven pattern to the diffraction device comprising a liquid crystalline layer where the helical orientation of the smectic liquid crystal phase having a helical structure is maintained.

Abstract: Semiconductor imaging devices with integrated holographic optical element for beam focusing and color separation.

Abstract: A display system using a hologram pattern liquid crystal can adjust color and quantity of light selectively for each and every pixel. The display system includes a plurality of first electrodes formed in line in the same direction, a plurality of second electrodes formed in line in a direction perpendicular to the first electrodes, liquid crystals having hologram patterns formed in a pixel area between the first and second electrodes, an optical waveguide for transferring light to the pixel area, and a light source, located in a side area of the optical waveguide, for generating the light.

Abstract: A display panel and system using a hologram pattern liquid crystal can adjust color and quantity of light selectively for each and every pixel. The display panel includes first and second data lines formed in line in the same direction, the second data lines overlapping with upper parts of the first data lines, first and second scanning lines formed in line in a direction perpendicular to the first and second data lines, the second scanning lines overlapping with upper parts of the first scanning lines, and liquid crystals having hologram patterns formed between the first scanning lines and the first data lines, between the first data lines and the second scanning lines, and between the second scanning lines and the second data lines, respectively.

Abstract: A device that provides a display indicating an absence of power to an LCD is disclosed. The device includes a continuous polarizing filter layer disposed within a display area that makes up a portion of the total display area of the LCD. A layer of liquid crystals is disposed between alignment gratings and optically coupled to the continuous polarizing filter layer. A discontinuous polarizing filter layer is optically coupled to the layer of liquid crystals. The discontinuous polarizing filter layer has a plane of polarization aligned with the plane of polarization of the continuous polarizing filter, and the discontinuous polarizing filter layer comprises a contour within the display area conforming to an image, so that the image is displayed in the absence of an electric field and indicates an absence of power.

Abstract: Disclosed is a device for producing colored light and an image generating apparatus including such a device. The device includes a switchable light-directing apparatus configured to receive light and a first control circuit coupled to the switchable light-directing apparatus. The first control circuit provides control signals to the switchable light-directing apparatus. In response to the switchable light-directing apparatus receiving a control signal, the switchable light-directing apparatus directs a first portion of the received light to a first region of a plane. Additionally, the switchable light-directing apparatus directs a second portion of the received light to a second region of the plane, and directs a third portion of the received light to a third region of the plane. The second region is positioned between the first and third regions of the plane.

Abstract: A polarization-independent optical switch is disclosed for switching at least one incoming beam from at least one input source to at least one output drain.

Abstract: According to the present invention, a method is provided for manufacturing a polarization diffraction film, which comprises the steps of forming a film with a liquid crystal material containing a liquid crystalline polymer and a crosslinkable substance, fixing a cholesteric alignment formed with the liquid crystal material, crosslinking the liquid crystal material to form a liquid crystal film and providing a region exhibiting a diffraction-capability on at least a part of the liquid crystal film or polarization diffraction film or comprises the steps of forming a film with a liquid crystal material containing a polymeric liquid crystal and a crosslinkable substance, crosslinking the liquid crystal material in a cholesterically aligned state so as to form a liquid crystal film with a cholesteric alignment fixed and providing a region exhibiting a diffraction capability on at least a part of the liquid crystal film.

Abstract: Disclosed is an apparatus and method of illuminating an image display via an electrically switchable holographic optical element. The method includes a first electrically switchable holographic optical element (ESHOE) receiving illumination light. The first ESHOE comprises oppositely facing front and back surfaces. The first ESHOE focuses a first component (e.g., p-polarized blue light) of the illumination light while transmitting the remaining components of the illumination light without substantial alteration. An image display is provided and receives the focused first component. In response to receiving the focused first component, the image display emits image light. The first ESHOE receives and transmits this image light without substantial alteration. In one embodiment, the focused first component emerges from the first ESHOE at the back surface thereof, and the first ESHOE receives the image light at the back surface.

Abstract: An optical illumination apparatus has a polarization conversion device for converting light from a light source into light polarized uniformly in a predetermined manner and an optical integrator system for illuminating a display panel with the light polarized in the predetermined manner. The polarization conversion device splits the light from the light source into a first light beam and a second light beam in such a way that the first and second light beams are polarized in different manners, and then converts one of the first and second light beams into light polarized in the identical manner as the other light beam. Moreover, the first and second light beams pass through an identical lens cell of a first lens array of the optical integrator system and are imaged on an identical lens cell of a second lens array of the optical integrator system.

Abstract: A display device including a diffraction grating from which a diffracted light of the zeroth order and a diffracted light of the first order having different color light components emerge to establish color separation. An array of micro-lenses is arranged on a liquid crystal panel. The liquid crystal panel has a plurality of picture elements and each picture element includes a plurality of color display dots. The color display dots in each picture element are arranged in the vertical relationship and in the order of wavelength of the light. A green light component of diffracted light of the first order is made incident normal to the liquid crystal panel, and the diffracted light of the zeroth order passes through the liquid crystal panel at a greater angle relative to the normal to the liquid crystal panel.

Abstract: A liquid crystalline film which functions suitably as a polarization rotating lattice is provided. The liquid crystalline film is characterized in that a cholesteric orientation or a chiral smectic C orientation, in which helical axis is not uniformly parallel in the thickness direction of the film nor is helix pitch of helices uniformly equal in the film thickness direction, is formed in a certain region of the film.

Abstract: A process and photoactive media for holographic recording and micro/nanofabrication of optical and bio-optical structures via the simultaneous absorption of two-photons by the photoactive media to induce a simultaneous photochemical change in regions of constructive interference within a holographic pattern is disclosed. The photochemical process of polymerization resulting from the simultaneous absorption of two-photons may be used for the microfabrication of micro and nanoscaled features, holographic data storage, and the formation of switchable diffraction gratings.

Abstract: An apparatus and method for manipulating small dielectric particles. The apparatus and method involves use of a diffractive optical element which receives a laser beam and forms a plurality of light beams. These light beams are operated on by a telescope lens system and then an objective lens element to create an array of optical traps for manipulating small dielectric particles.

Abstract: In order to read out information even from an optical recording medium having birefringence, of a diffracting element comprising an optical material forming a diffraction grating 21 having a cross-sectional shape of projections and recesses, and another optical material 22 filled at least in the recesses of the diffraction grating 21, at least one of the above two types of optical materials 21 and 22 shows birefringence, and the other optical material 22 has a refractive index which is different from both the ordinary refractive index and the extraordinary refractive index of said one optical material 21 showing birefringence.

Abstract: An optical device and a display apparatus of the present invention are constructed so as to improve display characteristics of output light intensity, display contrast, and reduction of scattered light due to external light, and also to provide a large-screen. The optical device has a first stacked body and a plurality of second stacked bodies. The first stacked body includes a light guide, a fist electrode, and an optical control layer. The second stacked body includes a plurality of second electrodes, the reflection film and a substrate. A plurality of third electrodes are provided through the substrate. Each of the third electrode has a first end part connecting to the second electrode and a second end part exposed to the other side of the substrate. A further light absorption film may be disposed between the reflection film and the second electrode.

Abstract: A diffractive focusing device includes a light transmissive substrate and a plurality of selectively light opaque elements formed in the light transmissive substrate. The selectively light opaque elements are capable of being electronically activated. Particular elements of the plurality of selectively light opaque elements are selectively rendered substantially light opaque or substantially light-transmissive in order to create light transmissive channels in the light transmissive substrate with desired diffractive characteristics.

Abstract: There is provided a light diffusion sheet comprising a light diffusion layer formed on a transparent substrate and containing a binder resin and resin particles that impart an uneven surface, wherein the uneven surface of the light diffusion layer exhibits an arithmetical mean deviation of 2.0 &mgr;m or more in three-dimensional surface roughness measurement and/or ten point height of irregularities of 10.0 &mgr;m or more in three-dimensional surface roughness measurement. This light diffusion sheet is high luminance in the front direction, is excellent in light-diffusing property, and is resistant to damage.

Abstract: The present invention relates to an optical device with a variable numerical aperture (NA), which utilizes special optical properties of a liquid crystal medium. Through the design of external electrodes and a circuit control unit, the refraction index of the liquid crystal medium can be modulated by the external voltage so that the beam passing through the LCD produces diffraction. An optical device with a variable focal point is thus formed by combining this LC diffractive device and an objective lens. So the present invention provides an optical device with focal points of different numerical apertures by varying the external voltage, whereby the device can read optical disks of all specifications.

Abstract: A multicolored reflection liquid crystal display device includes a pair of substrates having a reflective holographic polymer dispersed liquid crystal (H-PDLC) film disposed therebetween. The H-PDLC film contains at least two different reflection gratings capable of reflecting two different wavelengths of light. A multicolored reflection H-PDLC is obtained by simultaneously illuminating a plurality of regions of a film comprised of a mixture of a liquid crystal and a photo-polymerizable monomer with a plurality of holographic light patterns capable of providing liquid crystal layers of different spacings so as to obtain different reflection gratings in each of the regions. A mask is placed between each of the laser light beams and the film to form a pattern of light and dark regions on the film. Each mask is positioned such that at least one light region of a first beam pair coincides with at least one dark region of a second beam pair within the film.

Abstract: A liquid crystal cell includes a liquid crystal layer between upper and lower substrates. A series of insulating ridges forming a monograting structure overlay a first electrode overlaying the lower substrate. The ridges carry second electrodes connected together and displaced from the first electrode along the thickness dimension of the cell. The second electrodes lie within a “bulk region” of the liquid crystal bounded by the farthest extent reached by the liquid crystal in the thickness dimension. As the gap between electrodes is small, low drive voltages produce between the electrodes a significant electric field adjacent the surface.

Abstract: To provide a diffractive optical element that allows simplification of a manufacturing process and reduction in manufacturing costs. A diffractive optical element includes a first transparent substrate having a pair of transparent interdigitated electrodes facing each other formed on its surface, a second transparent substrate, and a liquid crystal sandwiched therebetween. Alignment layers are formed on surfaces of the first and second transparent substrates facing the liquid crystal. Pads are provided on the transparent electrodes and electrically connected to an outside. A seal material and a liquid crystal sealing port are provided on the first transparent substrate. The seal material is formed into a partly cut rectangle, and the liquid crystal sealing port is formed at the cut portion of the rectangular seal material.

Abstract: Disclosed is a device for producing colored light and an image generating apparatus including such a device. The device includes a switchable light-directing apparatus configured to receive light and a first control circuit coupled to the switchable light-directing apparatus. The first control circuit provides control signals to the switchable light-directing apparatus. In response to the switchable light-directing apparatus receiving a control signal, the switchable light-directing apparatus directs a first portion of the received light to a first region of a plane. Additionally, the switchable light-directing apparatus directs a second portion of the received light to a second region of the plane, and directs a third portion of the received light to a third region of the plane. The second region is positioned between the first and third regions of the plane.

Abstract: A renewable liquid reflection grating. Electrodes are operatively connected to a conducting liquid in an arrangement that produces a reflection grating and driven by a current with a resonance frequency. In another embodiment, the electrodes create the grating by a resonant electrostatic force acting on a dielectric liquid.

Abstract: An apparatus is disclosed for an electrically variable optical attenuator. The apparatus is comprised of an Electrically Switchable Bragg Grating device and a polarization-converting reflector. The polarization-converting reflector may be a one-quarter-wave retardation plate or a 45-degree Faraday rotation plate in combination with a mirror. The electrically variable optical attenuator is suited for use in fiber optic communications systems.

Abstract: An optical apparatus is disclosed for processing light that based on a pair of diffraction gratings operating in tandem, with one of the gratings being a fixed diffraction grating and with the other grating being electrically programmable. The combination of the fixed and electrically-programmable diffraction gratings provides a spectral resolution and dispersion higher than that of either diffraction grating when used alone. These two diffraction gratings can be formed on different substrates, or alternately be combined to form a composite diffraction grating. The electrically-programmable diffraction grating can be operated in either a singly-periodic mode or a multi-periodic mode to select particular wavelengths of the incident light for analysis and detection, or for transferring between optical fibers (e.g. wavelength division multiplexing or demultiplexing). In some cases, a prism can be substituted for the fixed diffraction grating or used in addition to the fixed grating.

Abstract: A complex diffraction device, which is excellent in designability, easy in setting the diffraction angle, adaptable to size increase, and easy to handle by adding a diffraction function resulting from an uneven pattern to the diffraction device comprising a liquid crystalline layer where the helical orientation of the smectic liquid crystal phase having a helical structure is maintained.

Abstract: A method for effecting the desired optical characteristics of an optical system (10) using phase diffractive optics. Incident light (Bi) is directed onto a surface (12i) of a material (12) whose index of refraction (n) is variable over the material. Passage of the incident light through the material effects the phase and amplitude of the light waveform. An optical map (Om) is determined for the surface of the material. This map comprises variations in the index of refraction over the material surface, and the map, in effect, represents any of a range of refractive and diffractive optical elements such as a mirror (1), a lens (2,3,6,7), or a diffraction grating (100). The map is dynamically written onto the material to map the material such that the incident light's passage through the material corresponds to the passage of the light through the optical element currently emulated by the material.

Abstract: A system and method for generating a system are disclosed. The system includes a display device comprising a plurality of display regions, each region configured for displaying a color component of the image. A display controller is coupled to the display device and is operable to activate the regions of the display device to display portions of the image. A plurality of light directing devices are positioned to receive light from regions of the display device and direct light towards an image plane. The system further includes a light directing controller coupled to the light directing devices to direct light received thereby to different areas of the image plane. The areas of the image plane generally correspond to the different portions of the image displayed by the regions of the display device.

Abstract: A diffractive spatial light modulator comprises first and second substrates (1, 2) between which an optical path is defined comprising, in order, first (8a,8b), second (5,6), and third (8a,8b) half wave retarders. The second retarder (6,5) has a fixed optic axis (9c) whereas the first and third retarders have switchable optic axes (9a,9b). The fixed optic axis (9c) is oriented outside the switching ranges of the switchable optic axes (9a,9b). The modulator is pixellated and each pixel comprises a switchable phase-only diffraction grating. Each pixel is switchable between a first mode in which incident light is output in the zeroth order diffraction lobe and a second mode in which incident light is deflected into higher order diffraction lobes. The spatial light modulator may be used in high brightness projection displays.

Abstract: A linear light valve array including individually addressable diffractive optical elements, the diffractive optical elements having planes of diffraction substantially perpendicular to the longitudinal axis of the array.

Abstract: A method of producing a switchable hologram generally comprises providing a substrate comprised of a liquid crystal material and having two generally opposed surfaces and recording a plurality of holographic fringes composed of liquid crystal droplets in the substrate with one or more of the plurality of holographic fringes positioned such that a surface of the fringes is angled relative to one of the substrate surfaces. The substrate is subjected to an electrical field during recording of the holographic fringes. The electrical field varies across the surface of the substrate so that the liquid crystal droplets are all oriented generally in a common direction.

Abstract: Disclosed is an apparatus and method of illuminating an image display via an electrically switchable holographic optical element. The method includes a first electrically switchable holographic optical element (ESHOE) receiving illumination light. The first ESHOE comprises oppositely facing front and back surfaces. The first ESHOE diffracts a first component (e.g., p-polarized blue light) of the illumination light while transmitting the remaining components of the illumination light without substantial alteration. An image display is provided and receives the diffracted first component. In response to receiving the diffracted first component, the image display emits image light. The first ESHOE receives and transmits this image light without substantial alteration.

Abstract: Transmission and reflection type holograms may be formed utilizing a novel polymer-dispersed liquid crystal (PDLC) material and its unique switching characteristics to form optical elements. Applications for these switchable holograms include communications switches and switchable transmission, and reflection red, green, and blue lenses. The PDLC material of the present invention offers all of the features of holographic photopolymers with the added advantage that the hologram can be switched on and off with the application of an electric field. The material is a mixture of a polymerizable monomer and liquid crystal, along with other ingredients, including a photoinitiator dye. Upon irradiation, the liquid crystal separates as a distinct phase of nanometer-size droplets aligned in periodic channels forming the hologram. The material is called a holographic polymer-dispersed liquid crystal (H-PDLC).

Abstract: An optically anisotropic diffraction grating for an optical read/write head, comprising optically isotropic polymer liquid crystal held between two transparent base plates. Gratings of different refractive indexes are formed by periodically changing the orientation of the polymer liquid crystal of the diffraction grating. This enables a high light-utilization efficiency and a high reliability to be obtained.

Abstract: As an optically anisotropic diffraction grating in an optical head for reading and/or writing of an optically recording medium, optically anisotropic diffraction grating which comprises an optically anisotropic polymer liquid crystal sandwiched between two transparent substrates are used. The optically anisotropic polymer liquid crystal can have an alignment direction periodically changed to form a grating of different refractive indices, obtaining a high-utilization efficiency by light ray and a high degree of reliability.

Abstract: A projection monitor and a method of displaying an output image on a viewing screen of the monitor utilize a number of reconfigurable holographic optical elements (HOEs), allowing the components of the monitor to be physically arranged in a compact configuration. The reconfigurable HOEs may be designed to perform simple optical functions that are commonly associated with traditional optical devices, such as those performed by lenses, prisms and mirrors. However, the reconfigurable HOEs are also designed to perform sophisticated optical manipulations, such as varying the light intensity with respect to a specific direction. Each reconfigurable HOE includes a hologram that is sandwiched between two electrode layers. The hologram is a holographic photopolymeric film that has been combined with liquid crystal. The hologram has an optical property that changes in response to an applied electrical field.

Abstract: In accordance with the invention, an optical fiber grating device is made by providing a fiber with an electrically actuable component optically responsive to voltage or current and a plurality of conductive elements to locally activate the component and thereby to produce local optical perturbations in the fiber. In a preferred embodiment, a fiber is provided with a core of liquid crystal material and a plurality of periodically spaced microelectrode pairs. Application of a voltage to the microelectrodes results in a periodic sequence of perturbations in the core index which produces a grating. When the voltage is switched off, the grating switches off. Other embodiments utilize helical conductive elements.

Abstract: An object is to provide an optical head device whereby the light utilization efficiency can be increased and which can be produced at a low cost. A glass substrate 1 having projections and recesses 2 formed by patterning a SiON type transparent thin film on its inner surface by dry etching, and a second glass substrate 3 having a polyimide film 4 formed as an alignment film on its inner surface, are laminated with a space, the periphery is sealed by a sealing material made of an epoxy resin 5, and liquid crystal 6 is injected under vacuum into the interior to form an optically anisotropic diffraction grating. On the outer surface of this second glass substrate 3, a quarter-wave film 7 is laminated, and a third glass substrate 9 is bonded by a photopolymer 8 to obtain a diffracting element 10. This diffracting element 10 is disposed between a light source and an optical recording medium to obtain an optical head device.

Abstract: A bar code reader for an automated storage library has a lens assembly with a pair of polarized liquid crystal lenses. Each lens has pair of parallel glass plates that are separated by upper and lower glass substrates. A series of polymer films are symmetrically spaced apart between the substrates. Both the substrates and the films are perpendicular to the glass plates. Electrodes are formed on the films and combine to form a semi-cylindrical stack of film. Liquid crystal fills the spaces between adjacent pairs of the films. The films are coated and/or treated by an alignment process to predispose the liquid crystals to a specific rotational direction. When a selected voltage is applied between adjacent ones of the electrodes, the liquid crystals are synchronously rotated to alter their refractive index to a desired value. Thus, when the layers of each lens are manipulated in unison, the bar code reader is able to quickly adjust its focal length to read bar codes at various distances.

Abstract: Binary optics are used in an illumination system to provide a method of imaging for a color projection display. In one embodiment a broad spectrum light source illuminates a multilevel optical phase element which disperses the broad spectrum light from the light source by diffraction. A display having a number of pixel elements, each capable of transmitting a predetermined spectral region, is positioned within the near field region of the multilevel optical phase element so as to receive the light dispersed by the multilevel phase element.

Abstract: Holographic optical elements (HOEs) can be used in systems and methods for providing illumination and for projecting images. The HOEs may be switchable HOEs, whose diffractive properties can be controlled. Described herein is a method of combining light from two or more illumination sources. In one embodiment, a reflection-type HOE is illuminated by the first illumination source. The HOE diffracts light from the first illumination source into an output direction. Light from the second illumination source is transmitted through the HOE and onto a reflective optical element, which reflects the light back through the HOE and into the same output direction. Also described is a projection system that uses two or more HOEs to combine two or more colors of light for use by a single image display. The system includes one or more light sources, an image display (such as a reflective or transmissive LCD display or a MEMS display, for example), and a first and a second HOE.

Abstract: A spatial light modulator, for instance of the diffractive liquid crystal type, comprises an addressing circuit and a plurality of pixels. Each of the pixels has a plurality of first elongate electrodes and a plurality of second elongate electrodes interdigitated with the first electrodes. The first electrodes are connected to the addressing circuit whereas the second electrodes are electrically floating.

Abstract: A system and a method of displaying projected images on a projection screen of the system include one or more reconfigurable holographic optical elements (HOEs) in the screen to optically manipulate the projected images impinging on the screen. The reconfigurable HOEs may be configured to perform simple optical functions that are commonly associated with traditional optical devices, such as lenses, prisms and mirrors. However, the reconfigurable HOEs may also be configured to perform sophisticated optical manipulations, such as varying angular intensity of diffused light toward predefined viewing regions. Each reconfigurable HOE includes a hologram that is sandwiched between two electrode layers. The hologram is a holographic photopolymeric film that has been combined with liquid crystal. The hologram has an optical property that changes in response to an applied electrical field. The reconfigurable HOEs are utilized to control the diffusing characteristic of the projection screen.

Abstract: The present invention is directed to liquid crystal diffraction gratings with electrically controlled periodicity. An electrical field is applied to liquid crystal device wherein the liquid crystals align to form a diffraction grating. The period of the diffraction grating is varied by changing the applied electrical field. The diffraction grating therefore has a period that can be varied by an electrical field.

Abstract: A system for generating an image comprising an illumination system having a light source and a plurality of holographic devices switchable between an active state wherein light from the light source is diffracted by the device and a passive state wherein the light is not diffracted by the device. A display device is positioned for illumination by the illumination system and operable to project a display image. The system further includes an optical projection device operable to receive the displayed image and form an intermediate image having a generally uniform illumination distribution on an optical diffuser. The diffuser is operable to project a resultant image with an emission angle larger than an emission angle of the display panel.

Abstract: A projection system and a method of displaying a projected input image on a projection screen of the system utilize one or more reconfigurable holographic optical elements (HOEs) to optically manipulate propagating light in the system. The reconfigurable HOEs may be configured to perform simple optical functions that are commonly associated with traditional optical devices, such as lenses, prisms and mirrors. However, the reconfigurable HOEs may also be configured to perform sophisticated optical manipulations, such as varying the light intensity toward a specific direction and generating virtual (holographic) images. Each reconfigurable HOE includes a hologram that is sandwiched between two electrode layers. The hologram is a holographic photopolymeric film that has been combined with liquid crystal. The hologram has an optical property that changes in response to an applied electrical field.