Abstract: An irradiance redistribution guide (IRG) for providing from a radiation source having a nonuniform irradiation distribution, a predetermined irradiance distribution over a predetermined target area spaced away from the IRG, includes a tubular reflective inner surface disposed between an entrance aperture and an exit aperture. The reflective inner surface has a varying cross-sectional radius. The profile of the cross-sectional radius is defined by a spline function that is uniquely determined by a plurality of knots. The IRG, when used in conjunction with a high-power solar concentrator, is advantageous in materials processing that requires high irradiance level that is uniformly distributed over an area spaced away from the exit aperture by a working distance.

Abstract: A fiber optic light source module (FOLSM) of a hybrid fiber optic lighting distribution system for distributing light from the FOLSM to various lighting features. The FOLSM includes a base, a lamp holder connected to a forward portion of the base and an access cover connected to a rearward portion of the base independent of the lamp holder. The base has a lamp cavity, a communicating lower rod support and an electrical lead port. The lamp holder has a front cover for covering the lamp cavity, an upper rod support and an annular lamp support member for interfacing with a lamp having a concave mirror. The upper and lower rod supports collectively form a rod support, wherein a square cross-sectioned light transmission connecting rod is seated therein via a resilient grommet. Accordingly, because the lamp support member is integral with the upper rod support, when the concave mirror is seated at the lamp support member the lamp is automatically aligned with respect to the light transmission connecting rod.

Abstract: A surface light source device of side-light type enables concentrated output of illumination light to a frontal direction. A flux having clear directivity is outputted from window portions 1w on an emitting surface 5 of a light guide plate 1 with emitting directivity. This flux is represented by a beam C01 outputted in a direction at an angle of 70.degree.. A flux C02 incident on reflection portions 1r is returned to the light guide plate 1 and is given an opportunity of output from the window portions 1w again. The flux C01 having escaped from the window portions 1w to an air layer AR is obliquely incident on flat regions 14g of a propagation direction characteristics modifier 14, and a degree of parallelization of the flux in a propagation direction is improved. The flux is blocked by the reflection portions 1r from being incident on a notch portion (uneffective area) between the flat regions 14g.

Abstract: Method and apparatus for forming hollow tubular light-distributing tubes for area illumination along the length of the tubes from a beam of light introduced into one end. Within the tube is a geometrically complex, 3-dimensional light redirecting structure traversing the light beam along the full length of the tube to redirect the light beam proportionately along the length of tube through a window formed therein. Both the tube and the light-redirecting structure can be formed as an integrated flat, substantially void-free structure for shipping and then converted in situ to the operative, 3 dimensional configuration.

Abstract: A photonic television system for propagating an image of light, in the form of its original three dimensional photonic makeup, through an airless, light proof, wave guide structure, utilizing a unique system of plastic concave and convex lenses in tandem, whose physical spacing is preferably one focal length from each other, which results in the photons of the image to be continually expanding and contracting, as they automatically propagate through each lens to the end of the wave guide, where via conventional magnifying lenses, the three dimensional image can be seen by a viewer, in a manner similar when viewing a microscope or telescope.

Abstract: A tip of a probe is sharpened and a level difference portion 6 in a boundary zone between a base portion 5 and an elastic functioning portion 4 is formed into a tapered configuration. The diameter of the elastic functioning portion 4 is made smaller than that of the base portion 5. Also, a part of the elastic functioning portion 4 is shaped into a constricted configuration. Also, the probe material is an optical fiber and this probe is composed of a core portion 2 that propagates light therethrough and clad portions 3 that differ in refractive index from each other. And the portion of the probe that excludes a aperture is clothed by a metal film cladding 7.

Abstract: An endoscope for image acquisition via illumination of an object's image, such as but not limited to a bar code, by a set of spatially resolved patterns, with subsequent reconstruction of the image without detailed spatial resolution. A device to stabilize the prescribed set of illuminating patterns against bending of the fiber is also disclosed, which consists of the auxiliary pre-bent part of the fiber and the work part of the fiber, subject to the inevitable bends with or without additional compensation. The distorting influence of the bending of the work part is compensated by the controllable loosening of the pre-bent part of the fiber. Encoding of the pixels of the image or of the illumination patterns encodes the intensity of each pixel to the excitation intensity of the corresponding mode. Such encoding is stable to the bending of the guide.

Abstract: A light pipe array includes a series of light pipes connected to a runner. The light pipes and runner are preferably molded as a single piece using a clear or transparent plastic. The runner is fabricated to have a relatively small cross-section when compared to the light pipes. The interconnection between the runner and each light pipe is chosen so that each light pipe is oriented to be substantially perpendicular to the runner. Additionally, the interconnection between the runner and each light pipes is chosen so that the runner is in close proximity to the light ray exit end of each light pipe. The small cross-section of the runner, the perpendicular relationship between the runner and the light pipes and the location of the connection between the runner and the light pipes provides a light pipe array exhibiting little or no contamination between the included light pipes.

Abstract: A fiber optic interface for laser spectroscopic Raman probes incorporating a housing with a window enclosure. The fiber optic interface minimizes stray light interference from window back reflections and provides high photonic efficiency through refractive manipulation of emission and reception fields. The illumination fiber is surrounded by collection fibers. The fiber bundle formed by the illumination fiber and the collection fibers is formed into a conical shape, which creates a refractive surface on the illumination fiber and each of the collection fibers. The refraction at the end faces steers the illumination and collection patterns toward the axis of the illumination fiber. This results in the reflected portion of the illumination light being reflected toward the illumination fiber, and in the collection pattern being coincident with the illumination pattern.

Abstract: A light guide light extraction mechanism can be formed in a predetermined maximum length to yield a predetermined light emission characteristic. Any shorter length segment removed from a predetermined end of the extraction mechanism and installed in a light guide of that shorter length causes the shorter length light guide to exhibit substantially uniform surface brightness. This obviates the need for cumbersome trial and error development of a different light extraction mechanism for each such shorter light guide.

Abstract: A line light source comprising a point line source, e.g., a light emitting diode (LED), and a light pipe having a rectangular, e.g., square, cross-section. Light rays from the point light source enter one end of the light pipe and travel along the length of the pipe. The light rays are reflected off notches or step-facets on one of the four sides of the light pipe. The light rays then pass across the light pipe and exit from the side of the light pipe opposite the notched/faceted side. The square cross-section of the light pipe of the present invention preserves the modes emitted from the point light source, i.e., the cone of emission from the light pipe is about the same as that from the light source. The light source converts a point light source to a line light source which emits light rays at a relatively uniform intensity along the length of the light pipe.

Abstract: An assembly for frontlighting or backlighting a display or other such arrangement requiring frontlighting or backlighting is disclosed herein. The assembly uses a light pipe with a set of specially configured microprisms to rotate the divergent angle of light. The divergent angle rotator is used with a flat collimator assembly for efficient display illuminating with light of a controllable degree of collimation in both dimensions.

Abstract: A light guide structure has a base portion which is slidingly received and retained by a supporting member. The longitudinal edges of a light guide are secured within longitudinal slots formed in the base member. The supporting member is mounted upon a surface. The support structure allows for expansion and contraction of the light guide with temperature variations.

Abstract: A light guide supporting structure has a base portion which is slidingly received and retained by a supporting member. The longitudinal edges of a light guide are secured within longitudinal slots formed in the base member. The supporting member is mounted upon a surface. The support structure includes an axial cavity which can form an electrical conduit.

Abstract: An internally-mirrored tube of constant cross-section, for use as a beam-shaper-uniformizer in an optical lithography tool, requires precision assembly, closely approaching total internal reflection, to be able to accept at the entry end a beam of laser light of specified numerical aperture, having an arbitrary cross-section and a non-uniform intensity profile, and deliver at the exit a beam having the same numerical aperture, the desired cross-sectional shape, and a substantially uniform intensity profile across the illuminated area. Imperfections at the edges of the component slabs would interfere with operation. The difficulty of machining internal surfaces to mirror smoothness, and the difficulty of applying mirror finishes to internal surfaces, suggests that the uniformizer be assembled from mirrored slabs cemented together. Achieving precision without breakage or scuffing of mirrors is difficult.

Abstract: An optical transmitter having a higher diffusiveness and a higher transmittivity simultaneously is constructed so that a light from a lamp 2 of light source enters an optical fiber materials A and is transmitted to a reflector tube 1 of which mirror surface of the inner side is formed by vacuum deposition. The diffused light components in the reflector tube 1 are reflected on the mirror surface and directed towards an optical fiber materials B and transferred to an exposure device 3 having a PLZT shutter.

Abstract: Illumination devices and methods of forming illumination devices, utilizing optical light films are disclosed. Joints useful in forming light carriers from optical light films are also disclosed.

Abstract: A compact beam scanning information readout device and method for reading bar code or other information requires little or no orientation of the information to be scanned by virtue of its raster or omni directional scan capabilities. Only a single mirror is needed to generate two dimensional scans. A wide range of scan speeds are also possible for simple or complex one or two dimensional patterns. Scanning in two dimensions may be done with independent and continuous control of the scan in each dimension. The scan patterns may be electronically controlled to instantly achieve various orientations ranging from a straight line rotated about a point to continuously rotating complex patterns. A light collector, light detector, processor, and means of signal transmission are also included. In one embodiment the device is packaged in a housing resembling a wand or a thin flashlight and in another embodiment the device is packaged in a ceiling mountable housing which will not interfere with counter top work space.

Abstract: An optical system is described consisting of reflection birefringent light valves, polarizing beam splitter, color image combining prisms, illumination system, projection lens, filters for color and contrast control, and screen placed in a configuration offering advantages for a high resolution color display. The illumination system includes a light tunnel having a cross-sectional shape corresponding to the geometrical shape of the spacial light modulator to optimize the amount of light projected onto the screen.

Abstract: A hollow, cylindrical light conduit for transporting light generally longitudinally therethrough and distributing light therealong includes a cylindrical wall member of a transparent material. The wall member has an inner cylindrical smooth surface and an outer cylindrical structured surface having an array of isosceles prisms arranged side by side thereon. The faces of adjacent prisms extend longitudinally along the cylindrical wall member and are aligned at the same desired prism angle relative to one another. The light transporting performance of the light conduit, achieved by total internal reflection, and the light distributing performance of the light conduit, specifically relative to radially aligned, high incident angle longitudinal light rays in planes parallel or near parallel to the prisms, is optimized as a function of the desired prism angle between the faces of adjacent prisms.

Abstract: A compound parabolic concentrator which can be used as an optical connector or in a like management system or simply as a concentrator or even as a spotlight, has a hollow body formed with an input aperture and an output aperture and a wall connecting the input aperture with the output aperture and diverting from the smaller of the cross sectional areas to the larger cross sectional areas of the apertures. The wall is composed of contiguous elongated prisms of a transparent dielectric material so that the single reflection from the inlet aperture to the outlet aperture takes place within the prisms and thus the losses of purely reflective reflectors can be avoided.

Abstract: A hollow light guide with opposed first and second parallel sections having confocal, parabolic cross-sectional shape. The light guide may be a prism light guide, or other hollow light guide such as a metallic mirror light guide or a multi-layer dielectric light guide. The cross-sectional shapes have vertices separated by a distance which does not exceed about three times (preferably, about 2.5 times) the focal length of the shapes.

Abstract: A lighting structure for intensely illuminating a narrow linear region. A light source emits light into an end of a hollow, elongate light guide. A longitudinal slit light-emitting aperture extends through an external wall of the light guide. A lens is mounted in the aperture. The lens bears a plurality of prisms which extend substantially perpendicular to the slit, on an inwardly directed face of the lens. The lens may be formed of a film material. A mechanism is provided to maintain the lens flat. A diffuser mounted outwardly of the lens bears a plurality of thin striations extending transversely, relative to the longitudinal slit aperture.

Abstract: A hollow light guide illumination system is provided for coupling light from an illumination source to a hollow light guide, which is used for a variety of purposes, such as tunnels, hallways, and large rooms where direct lighting is dangerous, difficult to maintain, or subject to vandalism. The illumination system employs an illumination reflector which has been customized to maximize the efficiency of light transmission between the illumination source, such as an arc lamp, and the core of the hollow light guide. A method of fabricating the customized illumination reflector includes mapping the radiation patterns of the particular illumination source to be utilized, creating a database of those radiation patterns, and utilizing the database to generate an optimal illumination reflector configuration. The computer-generated reflector will virtually always be a non-conic section, because the illumination source is not ideal.

Abstract: Three-layer light guide transports light from a source of low aspect ratio (e.g. nearly circular or nearly square) to one of high aspect ratio (e.g. narrow slit) to produce an output beam of low output divergence angles at high transfer efficiency. The design principle eliminates tapers or bends in the guide surfaces. Thereby, light from a conventional round lamp may be redirected with high optical efficiency to an aperture constrained to a long, narrow area, as in a slit headlight, a nacelle-rim light, a radome-edge light, or a landing light embedded in a wing having a sharp leading edge. The resulting far field intensity pattern is similar to that of a conventional sealed beam lamp.

Abstract: The invention provides a rigid endoscope utilizing a high refractive index (HRI) tunnel rod, preferably made of glass, for transfer of image light from a distal end to a proximal end of the device, such HRI tunnel rod being modified so that a minimum of light is scattered and reflected within the rod, thus minimizing veiling glare and contrast reduction of the image which is formed near the HRI tunnel rod's proximal end. The HRI tunnel rod shortens the apparent distance from the proximal to the distal end by virtue of its refractive index being greater than that of air, and also provides a light tunnel which can carry the image over a relatively long distance by virtue of its modified inside walls. A preferred method of modification includes hydrogen firing of the HRI tunnel rod in order to create a thoroughly blackened inner surface which is highly non-reflective, even at grazing incidences.

Abstract: HDI fabrication techniques are employed to form a variety of optical waveguide structures in polymer materials. Adaptive optical connections are formed, taking into account the actual position and orientation of devices which may deviate from the ideal. Structures include solid light-conducting structures, hollow light-conducting structures which are also suitable for conducting cooling fluid, and optical switching devices employing liquid crystal material. A "shrink back" method may be used to form a tunnel in polymer material which is then filled with an uncured polymer material that shrinks upon curing.

Abstract: Illumination devices and methods of forming illumination devices, utilizing optical light films are disclosed. Joints useful in forming light carriers from optical light films are also disclosed.

Abstract: A remote sensory unit, including any of a display, earphones and a microphone, connected to a driver by an optical link. The remote sensory unit is active, passive, or some combination of the two. Active sensory units are powered by solar cells, batteries, power transmitted through the optical link, or a combination thereof.

Abstract: The invention provides a rigid endoscope utilizing a high refractive index (HRI) tunnel rod, preferably made of glass, for transfer of image light from a distal end to a proximal end of the device, such HRI tunnel rod being modified so that a minimum of light is scattered and reflected within the rod, thus minimizing veiling glare and contrast reduction of the image which is formed near the HRI tunnel rod's proximal end. The HRI tunnel rod shortens the apparent distance from the proximal to the distal end by virtue of its refractive index being greater than that of air, and also provides a light tunnel which can carry the image over a relatively long distance by virtue of its modified inside walls. A preferred method of modification includes hydrogen firing of the HRI tunnel rod in order to create a thoroughly blackened inner surface which is highly non-reflective, even at grazing incidences.

Abstract: An illuminator apparatus has a light source and a liquid-core light guide comprising a tubular flexible sheath of a fluorocarbon polymer material which is filled with a lightguiding fluid such as glycol, a salt solution containing a chloride, fluoride or phosophate, phenylmethyl silicone oil (n.apprxeq.1.57), PCTFE oil, polychlorotrifluoroethylene oil (n=approx. 1.40) or also pure water. The tubular sheath is internally coated with a thin film of Teflon AF.RTM., the refractive index of which is lower than that of the sheath material.

Abstract: A fiber optic probe for detecting scattered light, with transmitting and receiving fibers having slanted ends and bundled together to form a bevel within the tip of the probe. The probe comprises a housing with a transparent window across its tip for protecting the transmitting and receiving fibers held therein. The endfaces of the fibers are slanted, by cutting, polishing and the like, so that they lie in a plane that is not perpendicular to the longitudinal axis of the respective fiber. The fibers are held in the tip of the probe using an epoxy and oriented so that lines normal to the slanted endfaces are divergent with respect to one another. The epoxy, which is positioned substantially between the transmitting and receiving fibers, is tapered so that the transmitting fiber, the epoxy and the receiving fiber form a bevel of not more than 20 degrees. The angled fiber endfaces cause directing of the light cones toward each other, resulting in improved light coupling efficiency.

Abstract: An optical scanning station is disclosed which utilizes light bending apparatus such as mirrors or optical wedges to gather and redirect some of the illumination radiating from the object. The gathering of the light occurs off-axis from the lens and the redirection of the light to the lens causes an off-axis angle between the light beam and the lens axis, thereby resulting in multiple images which are spaced apart from each other when focused on an image plane. The multiple images may be split apart and directed to separate image planes by use of front surface mirrors making the images then available for individual capture by charge couple devices or other similar image capture apparatus. Alternatively, the outboard images may be redirected, again by mirrors, to be focused coincident to the on-axis image, thereby increasing the illumination level at the image plane well in excess of that obtainable with only a single image of the object being focused at the image plane.

Abstract: The present invention provides an apparatus for transporting and distributing light. The apparatus comprises a longitudinal, hollow light conduit with a linear array of prisms arranged side-by-side to form grooves, the grooves disposed in a non-parallel orientation with respect to the longitudinal axis of the light conduit. The non-parallel orientation of the grooves causes some, or all, light which would otherwise be totally internally reflected within the light conduit to be emitted from the light conduit.

Abstract: Optoelectronic semiconductor devices which have a groove-shaped waveguide in an oxide layer provided on a silicon substrate are compact, easy to manufacture, and--when the waveguide comprises a non-linear optical material--applicable inter alia for frequency doubling of laser radiation. In known devices, scattering losses occur in the waveguide owing to the roughness of the groove which arises during etching of the groove. Here, the groove and a portion of the oxide layer are formed by local, preferably thermal, oxidation of the silicon substrate. The groove formed at the area of the oxidation mask has a smoother surface and as a result the waveguide has lower losses. When the device includes a GaAs/AlGaAs diode laser, it forms an efficient, compact, inexpensive and blue-emitting laser source which is suitable for use in an optical disc system. Preferably, the diode laser is situated in a deeper and wider further groove in the oxide layer.

Abstract: A prism light guide luminaire has opaque and light emitting surface portions which together form a selected cross-sectional configuration. The opaque surface portion has a light reflecting characteristic. The light emitting surface portion is prism light guide material which confines, within the luminaire, light rays which strike the material at angles falling within the material's acceptance angular range. Within the luminaire, a light scattering area having a predefined shape and location redirects light into angles falling outside the material's acceptance angular range.

Abstract: A compact array imager including image generation apparatus providing a real image at an inlet of an optical image waveguide. The real image being reflected a plurality of times within the optical image waveguide by diffractive optical elements that magnify and filter the real image and produce a virtual image at a viewing aperture The imager further includes electronics mounted on the sides of the optical image waveguide and coupled to the image generation apparatus by embedded molded signal waveguides for receiving signals representative of an image and controlling the apparatus to generate the image.

Abstract: A light valve is a planar member in which liquid crystals are hermetically sealed, and allows the transmission of light in an almost parallel direction and selectively scattering undesired light. On a rear surface of the light valve is disposed a light guide tube which contains a plurality of minute apertures. Alternatively, one of the substrates which constitute the light valve may be made of a fiber plate. The fiber plate has a structure in which short optical fibers are stacked. The light guide tube or the fiber plate converges a luminous flux emitted from the light valve to improve the contrast of an image. A projection display apparatus is constituted of a light source, a light valve, either a light guide tube or a fiber plate, a lens, and a projection lens. A luminous flux emitted from either the light guide tube or the fiber plate is incident on the pupil of the projection lens by way of the lens, and the projection lens casts this luminous flux onto a screen, thus forming a projected image.

Abstract: A flexible light conduit which preserves the coherence of a transmitted beam. Several conduit elements having optical elements mounted inside each one are connected together to form a chain. Each conduit element is tiltably coupled to each adjacent conduit element in the chain. The optical elements may be refractive or reflective. The conduit preserves the spatial coherence properties of the beam so the input image is reimaged at a distant place, having passed through the series of relay optical elements through the angles permitted by the coupling members.

Abstract: A new and improved laser light beam homogenizer for transforming a laser beam with spatially inhomogeneous intensity into a beam with a more nearly spatially uniform intensity pattern is presented. The light beam is diverged by a lens and presented to an integrator. The integrator transforms the beam into a beam with a more uniform illumination. The uniform illumination beam is then impinged on control optics to limit the divergence of the uniform beam and control higher order distortion in the system. This beam may then be illuminated at a predetermined distance by a projecting optic lens. The laser light beam homogenizer of this invention is particularly well suited for use in an imaging lidar system.

Abstract: A waveguide coupler for coupling electromagnetic power between a first rectangular waveguide and a second rectangular waveguide includes a one-dimensional intermediate waveguide formed of two plates spaced apart by a distance equal to a common height of the two waveguides. This enables a wave emanating from the first waveguide to spread apart transversely so as to equal the width of the second waveguide, the width of the second waveguide being greater than the width of the first waveguide. A cylindrical lens is located between the intermediate waveguide and the second waveguide to provide for a conversion between a cylindrical wavefront and a planar wavefront. The coupler is operative in reciprocal fashion such that a wave emanating from the first waveguide spreads out in width and is then converted to a planar waveguide prior to entering the second waveguide; and a wave emanating from the second waveguide is converted to a wave of contracting width for entry into the first waveguide.

Abstract: A waveguide virtual image display including image generation apparatus providing a real image at an inlet of an optical waveguide. The real image being reflected a plurality of times within the optical waveguide by diffractive optical elements that magnify and filter the real image and produce a virtual image at a viewing aperture. The display is mounted on an eyeglasses frame for hands-free viewing.

Abstract: Apparatus for producing a continuous line of light for a document scanner. An incoherent light beam is directed into one surface of an optical wedge device. The light beam is repeatedly reflected, back and forth, between input and output reflective surfaces on the wedge. The output surface is only partially reflective, thereby allowing a portion of the light to escape the wedge and provide the line of light which illuminates the document. Non-parallel sides extending between the reflective surfaces are used to provide total internal reflection and concentrate all of the incoherent light beams into a smaller area, Alignment of the incoherent light beam according to a predetermined angle causes the escaping light beams to be adjacent to each other and produce a uniform and continuous line of light free from destructive interference areas.

Abstract: When two hollow tubular light conduits are interconnected at a miter joint, beamed light can be redirected from one of the conduits to the other by a thin transparent prismatic element that is mounted to extend along the plane of the miter joint. When the interconnected conduits are acting as a luminaire, the miter joint can be fully illuminated by the transported light. A luminaire of unlimited length can be obtained by mounting a plurality of lamps and parabolic reflectors along a transparent hollow tubular light conduit and redirecting light from each lamp to be transported along the axis of the conduit in both directions.

Abstract: Disclosed is an apparatus and method for the modifying the intensity profile of radiant energy beam or reducing its spatial coherence, especially that produced by a laser. The apparatus includes a waveguide having a light reflecting surface including a substructure. The light reflecting surface and substructure reflect incident light causing chaotic scattering which acts to homogenize the intensity profile of the laser beam.

Abstract: A fiber optics illuminator includes a source of illumination on an optical axis and an optical element coaxially disposed on the optical axis, forming an image of the illumination source at an image plane. A housing encloses the source of illumination, the optical element and the image plane. A thermal control bushing is disposed on the optical axis at an exit aperture in the housing and includes an elongated, generally cylindrical glass rod coaxially disposed on the optical axis, having a first end at the image plane of the optical element, receiving illumination and heat, and a second end external to the housing. The thermal control bushing includes a means for dissipating heat from the glass rod by radiation outside the housing and by convection aided by a ventilating fan. An elongated fiber optics light guide has a light receiving end coaxially disposed adjacent to the second end of the glass rod, and a remote light-emitting end.

Abstract: A radiation guiding structure for incoherent radiation is disclosed in which a collimated beam is transmitted through a light pipe having high radition throughput. Radiation losses due to absorbance are minimized by: (1) matching the area of the beam and the light pipe passage; (2) minimizing the number of reflectances of a given ray by reducing the angular divergence of radiation in the beam; and (3) using a reflective coating on the wall of the light pipe which has the low point of its reflectance curve at a relatively high grazing angle.

Abstract: An image transmitting element and a process for producing the same are disclosed, which image transmitting element comprises: a transparent substrate; photo-transmissible holes one-dimensionally or two-dimensionally formed as an array in the transparent substrate, each of the holes having one end opened at one surface of the substrate and the other end made blind and provided with a substantially spherical top end within a thickness of the substrate; a photo-absorptive surface formed on at least a part of an inner surface of each of the photo-transmissible holes except the surface of the spherical top end thereof; and a transparent material with which the photo-transmissible holes are filled, the transparent material having a refractive index higher than that of the substrate.