Abstract: A variable-angle, wide-angle illuminator is disclosed, one embodiment being a small-gauge, variable-angle illumination surgical system comprising: a light source for providing a light beam; an optical cable, optically coupled to the light source for receiving and transmitting the light beam; a handpiece, operably coupled to the optical cable; an optical fiber, operably coupled to the handpiece, wherein the optical fiber is optically coupled to the optical cable to receive and transmit the light beam; an optical assembly, optically coupled to a distal end of the optical fiber, for receiving the light beam and providing the light beam to illuminate a surgical field; and a cannula, operably coupled to the handpiece and optical assembly, for housing and directing the optical assembly to illuminate a selected area, such as a surgical site.

Abstract: A method and device for converting an input light signal into an output light signal, in an optical component is described. An input light signal, at a first wavelength, and a first light beam which may be at a second wavelength, are received at the component. The input light signal and the first light beam interfere in the component to form an interference pattern, which modifies a reflectivity spectrum of the component to increase the reflectivity of the component in a portion of the reflectivity spectrum. A second light beam, having a second wavelength corresponding with a wavelength within the portion of the reflectivity spectrum, is also received at the component and is then reflected from the component, in dependence upon the portion of the reflectivity spectrum, to generate the output light signal at the second wavelength. This enables conversion of light signals to signals at a different wavelength.

Abstract: A method and apparatus for reducing blur in an image generated by an imaging system is provided. A blur model for the image is identified with respect to an exposure time for the image using a sequence of reference images of an artificial reference point object generated during the exposure time for the image. A source of the artificial reference point object is inertially stabilized over the exposure time. The image is deconvolved with the blur model identified for the image to form a modified image having a desired reduction in blur relative to the image generated by the imaging system.

Abstract: A velocimetry system for measuring the velocity of a moving body propagating through a measurement volume includes a light source for emitting a light beam, a controller for generating a modulation pattern corresponding to a desired set of fringes to be generated in the measurement volume, and a spatial light modulator operatively connected to the controller to receive therefrom the modulation pattern. The spatial light modulator is configured to spatially modulate the light beam according to the modulation pattern in order to generate the desired set of fringes in the measurement volume. Also provided are a light detector for measuring the energy of the light scattered by the moving body as it intersects the fringes, and a data analysis unit operatively connected to the light detector and adapted to determine the velocity of the moving body from at least one fringe characteristic and the energy of the scattered light measured.

Abstract: A system and method may utilize holography to facilitate fabrication techniques such as 3D printing and lithography. The system may include a light source, a hologram of an original object or lithographic pattern recorded in a holographic medium, and a target such as a reservoir of photosensitive material or a photosensitive material attached to a substrate. Illuminating the hologram with the appropriate light source may cause a holographic image of the original object or lithographic pattern to form on the photosensitive material within the reservoir or on the substrate. Formation of the holographic image may result in the formation of a new object from the photosensitive material, or may facilitate removal or retention of photosensitive material as part of a lithographic process.

Abstract: A system and method may utilize holography to facilitate fabrication techniques such as 3D printing and lithography. The system may include a light source, a hologram of an original object or lithographic pattern recorded in a holographic medium, and a target such as a reservoir of photosensitive material or a photosensitive material attached to a substrate. Illuminating the hologram with the appropriate light source may cause a holographic image of the original object or lithographic pattern to form on the photosensitive material within the reservoir or on the substrate. Formation of the holographic image may result in the formation of a new object from the photosensitive material, or may facilitate removal or retention of photosensitive material as part of a lithographic process.

Abstract: This disclosure provides systems, methods and apparatus for enhancing the brightness and/or contrast ratio of display devices. In one aspect, the display devices can include a light redirector that is optically coupled with a diffuser. The light redirector includes a plurality of holographic features that can receive near-collimated light at non-normal angles with respect to a normal to a surface of the light redirector and redirects the received light along a direction that is substantially normal to the surface.

Abstract: Multiple pairs of substrate-guided wave-based holograms (SGWHs) are laminated to a common thin substrate to form a transparent substrate-guided wave-based holographic CHMSL (SGWHC) that diffracts playback LED illumination over a wide angular range. This device is made pursuant to a technique that includes the steps of recording a first set of SGWHs with one setup, that upon playback, will couple and guide the diffracted light inside the substrate, and a second set of SGWHs recorded with another setup, that will diffract and couple the guided light out.

Abstract: A solar light concentration plate comprises a plurality of holograms diffracting incident light wherein each of the plurality of the holograms has a thickness, at least one intermediate light guide plate disposed between the plurality of the holograms, and a pair of external light guide plates disposed on outer surfaces of outermost holograms of the plurality of the holograms, wherein at least one of the pair of the external light guide plates has an inner surface and an outer surface inclined relative to the inner surface.

Abstract: A single longitudinal mode diode laser module including a laser diode (1) and an external resonator using a volume holographic grating (3) having a prescribed reflective bandwidth is made amenable to automatic power control by controlling the temperature of the laser diode such that the laser power may be allowed to increase monotonically with an increase in the input current. Therefore, the output laser power can be controlled at a constant level by automatic power control or by adjusting the input current while monitoring the laser power at any desired level of the laser power.

Abstract: A hologram layer (13) is irradiated by light from an optical element (10). The hologram layer (13) is provided with a first hologram (14) that diffracts in a predetermined direction, from among incident light from the optical element (10), X-polarized light in which the polarization component is in a specific direction and emits the light as X-polarized light of a first phase state (P1), and a second hologram (15) that both diffracts in the same direction as the X-polarized light of the first phase state (P1) and moreover at an equal radiation angle, from among incident light from the optical element (10), Y-polarized light in which the polarization component is in a direction orthogonal to that of the X-polarized light and converts it to X-polarized light, and emits the light as X-polarized light of a second phase state (P2) that differs from the first phase state (P1).

Abstract: A solar light concentration plate comprises a first hologram which receives solar light and diffracts incident light in a range of an incident angle, and first and second light guides respectively disposed on both sides of the first hologram, wherein at least one of the first and second light guides has an outer surface substantially inclined to an inner surface of the at least one of the first and second light guides.

Abstract: An identification medium, in which a pattern is clearly altered in observation through a right-handed circularly polarizing filter and observation through a left-handed circularly polarizing filter, is provided. The identification medium is formed by laminating a cholesteric liquid crystal layer, a ?/4 plate, and a linearly polarizing filter layer, in that order, from an observing side. The cholesteric liquid crystal layer is formed with a hologram and selectively reflects light. In an observation through a circularly polarizing filter that transmits the light reflected at the cholesteric liquid crystal layer, light reflected at a pattern printed layer is not perceived due to the function of a circularly polarizing layer. Images are clearly altered by switching a right-handed and a left-handed circularly polarizing filter.

Abstract: An identification medium is provided in which latent image having plural colors can be observed even when the identification medium is spaced away from a polarization filter. A cholesteric liquid crystal layer is provided as a specific polarization light reflection layer which reflects light having a specific polarized condition. An optical anisotropic layer having an optical anisotropy is provided at an upper position overlapping with the specific polarization light reflection layer. An image A fanned by an area having an optical anisotropy different from that of surroundings is formed at the optical anisotropic layer. When the identification medium is directly viewed, the influence of the optical anisotropy cannot be seen. When the identification medium is observed via a circular polarization filter, the image can be seen to have a specific color by the influence of the optical anisotropy.

Abstract: An arrangement utilizes diffractive, reflective and/or refractive optical elements combined to intensify and homogenize electromagnetic energy, such as natural sunlight in the terrestrial environment, for purposes such as irradiating a target area with concentrated homogenized energy. A heat activated safety mechanism is also described.

Abstract: The optical diffuser mastering of the subject invention includes legacy microstructure surface relief patterns, along with smaller ones, overlaid on the larger ones. The characteristic features produced by the present invention will be found useful to eliminate visible structures in/on optical diffusers, such as those used in movie projection screens (utilizing either coherent (i.e., laser-generated) and non-coherent (e.g., lamp-generated) light), head-up displays (HUDs), laser projection viewing, etc., as the present invention produces much sharper images than those afforded by traditional holographic optical diffusers.

Abstract: A projection display 210 arranged to display an image to an observer 212 use waveguide techniques to generate a display defining a large exit pupil at the point of the observer 212 and a large field of view, while using a small image-providing light source device. The projection display 210 uses two parallel waveguides 214, 216 made from a light transmissive material. One waveguide 214 stretches the horizontal pupil of the final display and the other waveguide 216 stretches the vertical pupil of the final display and acts as a combiner through which the observer 212 views an outside world scene 220 and the image overlaid on the scene 220. In a color display, each primary color is transmitted within a separate channel R, G, B.

Abstract: A free-space dynamic diffractive projection apparatus comprises a laser light source element, a dynamic diffractive element, a control element, and a signal output element. Based on a pattern signal outputted from the signal output element, the control element controls the laser light source element to emit a color beam, and controls the dynamic diffractive element to perform real-time signal modulation so as to generate different dynamic diffractive grating distributions in a specific period. Accordingly, the color beam passes through the dynamic diffractive element to produce the pixels defined by the pattern signal in a specific space. The control element controls the dynamic diffracting element to be quickly switched to display each pixel, so that each pixel is projected on a corresponding position in a specific space to form a two-dimensional geometric image.

Abstract: A main object of the present invention is to provide a hologram observation sheet with a transmission type hologram formed integrally with other members, to be attached with various members for the use as for example an advertising medium or a decoration member. To achieve the object, the invention provides a hologram sheet comprising: a transparent substrate, a hologram layer formed on the transparent substrate and having a transmission type Fourier transform hologram region having the function of transforming a light beam incident from a point light source to a desired optical image, and a pressure-sensitive adhesive layer.

Abstract: The present invention is directed toward a system and method for projecting holographic optical traps whose intensity maxima are extended along specified paths in three dimensions with specified amplitude and phase profiles along those paths. Specifying paths that constitute knotted loops and phase profiles that direct radiation pressure along the knotted paths yields optical traps that exert knotted force fields. Knotted optical force fields have uses for inducing motion along knotted paths, with applications including the generation of knotted electric current loops in plasmas.

Abstract: Optical solenoid beams, diffractionless solutions of the Helmholtz equation whose diffraction -limited in-plane intensity peak spirals around the optical axis, and whose wavefronts carry an independent helical pitch. The solenoid beams have the noteworthy property of being able to exert forces on illuminated objects that are directed opposite to the direction of the light's propagation. Optical solenoid beams therefore act as true tractor beams that are capable of transporting material back toward their source.

Abstract: The invention relates to optical device for illuminating a pixel matrix and/or a controllable spatial light modulator for a display, in particular a stereoscopic or holographic 3D display, wherein the optical device comprises a layer formed as a light waveguide, in which illumination light is guided in a light guiding layer, in particular according to the principle of total internal reflection, between two reflection layers lying opposite one another, wherein an extraction means for extracting illumination light from the light guiding layer is provided. The optical device is characterized in that the extraction means has different properties, in particular different optical properties, at a first extraction position than at another extraction position different to the first extraction position.

Abstract: A Head Up Display can be utilized to find light from an energy source. The Head Up Display includes a first waveguide having a first input coupler and a first output coupler. The Head Up Display can also include a second waveguide having a second input coupler and a second output coupler. The first waveguide has a first major surface and the second waveguide has a second major surface, which are disposed approximately parallel to each other. The first waveguide and the second waveguide are positioned as a combiner and allowing viewing an outside feed and information from an image source. The first input coupler diffracts light in the first field of view into the first waveguide and light in a second field of view reaches the second input coupler and is diffracted into the second waveguide.

Abstract: This disclosure provides systems, methods and apparatus, including a display device that includes an overlying holographic film. In one aspect, the holographic film includes a hologram that is configured to turn light incident on the film. The light is turned towards the display device at desired angles. The display can be formed of interferometric modulators and the turned light can be reflected off the display, and towards a viewer, to form an image. For light that is incident on the film at angles outside of a view cone, the holographic film is provided with holographic light turning features that turn this light so that it is reflected off the display at angles within a view cone of the display.

Abstract: A laser beam (L50) generated by a laser light source (50) is reflected by a light beam scanning device (60), and irradiated onto a hologram recording medium (45). On the hologram recording medium (45), an image (35) of a scatter plate is recorded as a hologram by using reference light that converges on a scanning origin (B). The light beam scanning device (60) bends the laser beam (L50) at the scanning origin (B) and irradiates it onto the hologram recording medium (45). At this time, scanning is carried out by changing the bending mode of the laser beam with time so that the irradiation position of the bent laser beam (L60) on the hologram recording medium (45) changes with time. Regardless of the beam irradiation position, diffracted light (L45) from the hologram recording medium (45) reproduces the same reproduction image (35) of the scatter plate at the same position.

Abstract: An optical element is provided with: first polarization-separation layer (13) that is laminated on first surface (12b) of light guide body (12) and that, of the light incident from light guide body (12), transmits X-polarized light and reflects Y-polarized light that is orthogonal to the X-polarized light; polarization hologram layer (14) that is laminated on first polarization-separation layer (13) and that diffracts to a prescribed diffraction angle the X-polarized light that is incident within a prescribed range of angles of incidence and converts the X-polarized light to Y-polarized light; second polarization-separation layer (15) that is laminated on polarization hologram layer (14) and that, of the light incident from polarization hologram layer (14) transmits Y-polarized light and reflects X-polarized light; reflection layer (18) provided on second surface (12c) side of light guide body (12); and phase difference layer (17) that is provided between first surface (12b) of light guide body (12) and refle

Abstract: A projection apparatus has a hologram recording medium configured to be capable of diffusing coherent light beams, an irradiation unit configured to irradiate coherent light beams to the hologram recording medium so that the coherent light beams scan the hologram recording medium, a light modulator that is illuminated by coherent light beams incident on and diffused at respective points of the hologram recording medium from the irradiation unit, a projection optical system configured to project a modulated image generated by the light modulator onto a scattering plane, and an imaging optical system provided between the hologram recording medium and the light modulator, configured to converge the coherent light beams diffused at respective points of the hologram recording medium to illuminate the light modulator.

Abstract: A method of displaying a video image comprises receiving sequential image frames at a processor. Each image frame is processed to obtain a kinoform. A programmable diffractive element such as an SLM represents the sequence of kinoforms allowing reproduction of the image using a suitable illumination beam.

Abstract: A system and a method perform buoyance of a 3D hologram image on a hologram display screen in a projection mode. A system of displaying a digital hologram includes: a composite hologram unit configured to generate a hologram array by receiving hologram data of a fringe pattern and by compositing background image and a foreground image using the received fringe pattern; a hologram projection unit configured to project a hologram image through a wide-angle lens by applying a light to the hologram array; and a hologram display unit configured to perform space buoyance of the hologram image projected by the hologram projection unit on a 3D hologram display screen. The digital hologram content is managed in real time, and transmission of the digital hologram content to a remote place and site adaptive display of hologram image media may be achieved.

Abstract: A laser processing device includes a laser light source, a spatial light modulator, a control section, and a condensing optical system. The spatial light modulator, presents a hologram for modulating the phase of the laser light in each of a plurality of two-dimensionally arrayed pixels, and outputs the phase-modulated laser light. The control section causes a part of the phase-modulated laser light (incident light) to be condensed at a condensing position in a processing region as a laser light (contribution light) having a constant energy not less than a predetermined threshold X. The control section causes a laser light (unnecessary light) other than the contribution light condensed to the condensing position existing in the processing region to be dispersed and condensed at a condensing position existing in a non-processing region as a plurality of laser lights (non-contribution lights) having an energy less than the predetermined threshold.

Abstract: A security device having a lenticular device that includes an array of lenticular focusing elements located over a corresponding array of sets of image strips such that at different viewing directions, a corresponding image strip from each set is viewed via respective ones of the lenticular focusing elements wherein the image strips are defined at least in part by a relief structure.

Abstract: An adjustable holder (1) for a concave holographic grating (2) for enabling the correct positioning of the grating vis-à-vis a light entrance port (15) and a light exit port (20), characterized in, that it comprises a grating hinge (10) fixed to said grating, said grating hinge (10) enabling rotational adjustment of the grating position with respect to said holder (1), the center point of the rotational adjustment being located at the vertex of said grating (2).

Abstract: Proposed is a speckle-reduced laser illumination device that may be used in optical microscopy, machine vision systems with laser illumination, fine optical metrology, etc. The device comprises a net of planar ridge waveguides formed into an arbitrary configuration and having a plurality of holograms with holographic elements formed into a predetermined organization defined by the shape of a given light spot or light field which is to be formed by light beams emitted from holograms on the surface of an object or in a space and at a distance from the planar ridge waveguide. Speckling is reduced due to the fact that at least a part or all of the holograms are spaced from each other at distances equal to or greater than the coherence length. The geometry and organization of the holographic elements allow position control of the light spot and beam converging and diverging.

Abstract: An exposure device includes at least one light emitting element that emits light in a normal direction of the substrate; at least one hologram element that is recorded on a recording layer arranged on the substrate to diffract light emitted from the light emitting element and condense the diffracted light on a condensing point on a normal line of the light emitting element; and at least one light inhibiting part that is arranged on a straight line that connects the light emitting element and the condensing point such that the light diffracted by the hologram element passes through the outside of the light inhibiting part and condenses at the condensing point, to inhibit transmission of zeroth-order light that goes straight toward the condensing point from the light emitting element without being diffracted by the hologram element.

Abstract: Proposed is a method of laser illumination with reduced speckling for in optical microscopy, machine vision systems with laser illumination, fine optical metrology, etc. The method comprises forming a net of planar ridge waveguides into an arbitrary configuration and providing them with a plurality of holograms having holographic elements formed into a predetermined organization defined by the shape of a given light spot or light field which is to be formed by light beams emitted from the holograms on the surface of the object or in a space at a distance from the planar ridge waveguide. Speckling is reduced by locating at least a part or all of the holograms at distances from each other that are equal to or greater than the coherence length. The geometry and organization of the holographic elements allows controlling position, focusing and defocusing of the beam.

Abstract: An optical device includes: a light guide plate receiving, for each of N types of wavelength bands, a plurality of parallel light beams with different incident angles each corresponding to view angles, and guiding the received parallel light beams; a first and a second volume hologram gratings of reflection type having a diffraction configuration which includes N types of interference fringes each corresponding to the N types of wavelength bands, and diffracting/reflecting the parallel light beams. The optical device satisfies for each wavelength band, a relationship of ‘P>L’, where ‘L’ represents a central diffraction wavelength in the first and second volume hologram gratings, defined for a parallel light beam corresponding to a central view angle, and ‘P’ represents a peak wavelength of the parallel light beams.

Abstract: A laser beam (L50) is reflected by a light beam scanning device (60), and irradiated onto a hologram recording medium (45) where an image (35) of a scatter plate is recorded as a hologram by using reference light that converges on a scanning origin (B). The light beam scanning device (60) bends the laser beam (L50) at the scanning origin (B). Scanning is effected by changing the bending mode of the laser beam so that the irradiation position of the bent laser beam (L60) on the hologram recording medium (45) changes with time. Regardless of the beam irradiation position, diffracted light (L45) from the hologram recording medium (45) reproduces the same reproduction image (35) of the scatter plate at the same position. An illumination spot with reduced speckles is formed on the surface (R) of an illuminating object (70) by the reproduction image (35) of the hologram.

Abstract: A illumination device includes a light source, a diffractive optical element on which light emitted from the light source is made incident, and a superimposing optical system on which diffracted light emitted from the diffractive optical element is made incident. A direction of a principal ray in the center of the diffracted light coincides with an optical axis of the superimposing optical system. Consequently, it is possible to reduce an aberration due to the superimposing optical system and to emit illumination light having a more uniform illuminance distribution.

Abstract: A projection apparatus has an optical device capable of diffusing coherent light beams, an irradiation unit to irradiate coherent light beams to the optical device so that the coherent light beams scan the optical device, a light modulator to generate a modulated image using coherent light beams incident on and diffused at respective points of the optical device from the irradiation unit, and a projection optical system to project a modulated image generated by the light modulator onto a scattering plane. The light modulator has a plurality of micromirrors provided for each pixel, to switch a reflection angle of each coherent light beam from the optical device, and a reflection angle controller to control a timing of switching a reflection angle of each of the plurality of micromirrors so that the timing becomes irregular for each frame period that is a time unit for generating the modulated image.

Abstract: An apparatus for providing an optical display includes an optical substrate for propagating light received from a light source, a first set of one or more switchable diffractive elements in the substrate, and a second set of one or more switchable diffractive elements in the substrate. Each diffractive element in the second set corresponds to a diffractive element in the first set. Each of the diffractive elements in the first and second sets is configured to switch between on and off states. One of the states is for diffracting light and the other state for allowing light to pass through. Each of the first set of diffractive elements is configured to diffract the light at an angle for propagation in the substrate. Each of the second set of diffractive elements is configured to diffract the light for display.

Abstract: An optical device includes: a light guide plate receiving, for each of N types of wavelength bands, a plurality of parallel light beams with different incident angles each corresponding to view angles, and guiding the received parallel light beams; a first and a second volume hologram gratings of reflection type having a diffraction configuration which includes N types of interference fringes each corresponding to the N types of wavelength bands, and diffracting/reflecting the parallel light beams. The optical device satisfies for each wavelength band, a relationship of ‘P>L’, where ‘L’ represents a central diffraction wavelength in the first and second volume hologram gratings, defined for a parallel light beam corresponding to a central view angle, and ‘P’ represents a peak wavelength of the parallel light beams.

Abstract: An image display device includes an image forming device, collimating optical system, and optical device, with the optical device including a light guide plate, first diffraction grating member and second diffraction grating member which are made up of a volume hologram diffraction grating, and with central light emitted from the pixel of the center of the image forming device and passed through the center of the collimating optical system being input to the light guide plate from the near side of the second diffraction grating member with a certain angle. Thus, the image display device capable of preventing occurrence of color irregularities, despite the simple configuration, can be provided.

Abstract: In various embodiments described herein, a display device includes a front illumination device that comprises a light guide disposed forward of an array of display elements, such as an array of interferometric modulators, to distribute light across the array of display elements. The light guide may include a turning film to deliver uniform illumination from a light source to the array of display elements. For many portable display applications, the light guide comprises the substrate used in fabricating the display elements. The display device may include additional films as well. The light guide, for example, may include a diffuser and/or an optical isolation layer to further enhance the optical characteristics of the display.

Abstract: A system includes a light source and a grating cube. The grating cube includes a transmission volume holographic grating positioned between two prisms. The transmission volume holographic grating diffracts part of a light source emission toward a reflective surface, producing diffracted light. At least some of the diffracted light is reflected off of the reflective surface, producing feedback light. The feedback light is fed back to the light source, thereby causing the light source emission to have the same wavelength as the feedback light.

Abstract: A projection system includes at least one projector and a holographic projection film. The projector projects a first image to a projection surface. The holographic projection film mirrors the first image on the projection surface to form a second image on an imaging surface. The projection surface and a standard surface define a first angle therebetween. The first angle is Y degrees. The holographic projection film and the standard surface define a second angle therebetween. The second angle is 45+X degrees. Y and X substantially satisfy: Y=2X.

Abstract: An exposing device including a light emitting element array of light emitting elements arrayed in a row along a predetermined first direction; a hologram recording layer in which hologram elements are multiplex recorded such that each of the hologram elements corresponds to one of the light emitting elements and diffracts an emission beam from the light emitting element and converges the light onto a light exposure plane, such that focused beam spots are formed on the light exposure plane in a row along the first direction; and a first transmission control section, disposed at the light incident side of the hologram recording layer, provided with a structure in which light blocking sections and light transmitting sections are alternately arrayed along a second direction intersecting with the first direction, and selectively transmitting in the second direction light passing along the optical path of the reference beam.

Abstract: Encoding of quantum algorithm and devices therefrom are provided. The encoding includes receiving a unitary matrix operator representing the quantum algorithm, each row of the unitary matrix operator defining a superposition of basis state vectors for transforming input states to output states. The encoding also includes recording rows of the unitary matrix operator by applying, to a volume holographic element, a combination of an ith one of n reference waves and a superposition of n signal waves defined by the superposition defined in an ith row of the unitary matrix operator. The n signal waves are a first set of n plane waves lying on a first conical surface having a first half angle and the n reference waves are a second set of n plane waves lying on a second conical surface, concentric with the first conical surface, with a second half angle different that the first half angle.

Abstract: A security device comprising at least first and second superposed optically variable effect generating structures (3-5, 31-51), each having a surface relief microstructure, the second optically variable effect generating structure being viewable through the first.

Abstract: An integrated hologram optical device, a method of manufacturing the same, and an integrated hologram recording apparatus are provided. The integrated hologram optical device includes a two-dimensional (2D) array of a plurality of hogels. A holographic element is configured to be recorded such that a combination of the plurality of hogels is configured to adjust at least one of an angle and a focal length of a signal beam.

Abstract: There is provided a colour sequential illumination device comprising in series: first and second light sources; a condenser lens; and a grating device. The grating device comprises at least one Bragg grating. The condenser lens directs light from the first and second sources into the grating device at first and second incidence angles respectively. The grating device diffracts light from the first and second sources into a common direction. Desirably, the Bragg gratings are Electrically Switchable Bragg Gratings. In one embodiment of the invention the light sources are Light Emitting Diodes. Alternatively lasers may be used.