Abstract: New intraocular lenses and methods for producing such lenses are included. In one embodiment, the intraocular lens includes an optic; and at least one fixation member, e.g., haptic, secured to and extending from the optic, the fixation member being made from a compressed item having a compressed thickness and made of a polymer selected from the group consisting of methyl methacrylate homopolymers, methyl methacrylate-containing copolymers and mixtures thereof, the compressed item being derived by subjecting an item having a thickness to compression, preferably along an axis substantially parallel to the thickness, to reduce the thickness, provided that the compressed item has increased tensile strength relative to the item and is substantially no less intraocular lens manufacturable than is the item.

Abstract: A novel polythiol having four or more functional groups, a process for producing the polythiol comprising reacting thiourea with a specific compound, a sulfur-containing urethane-based resin prepared from the polythiol and a lens made of the resin. The resin has a high refractive index, and low dispersion of refractive index, is lightweight, colorless and transparent, has no optical distortion, and has excellent characteristics in weatherability, dye-affinity, heat resistance, impact resistance and machinability.

Abstract: The two sides of a multiple cavity mold having electroformed mold cavities for molding intraocular lenses with integral haptics are made by a preferred electroforming procedure involving the use of either a single primary master having a single cavity corresponding to the portion of the lens at either side of its median plane transverse to its optic axis if the lens to be molded is symetrical about both this transverse median plane and its longitudinal median plane containing the optic axis, or a pair of primary masters having single cavities, respectively, corresponding to the portions of each lens at opposite sides of its transverse median plane if the lens is unsymmetrical about either plane.

Abstract: Nanoparticles of a mixed oxide precursor are reduced to form particles of a anostructured metastable alloy having a majority metal and a minority metal. Additional heating enriches the surfaces of the particles with respect to the minority metal, thus forming a coating on the particle core. This coating has a higher atomic ratio of minority to majority metal than found in the precursor. The nanostructured metastable alloys may then be oxidized to form nanoparticles having a coating of the oxide of the minority metal and a core of the majority metal or an oxide of the majority metal. The majority metal may be, for example, copper. The minority metal may be, for example, cobalt.

Abstract: A molded article having a predetermined shape transferred from a mold, characterized by being provided with an informative mark corresponding to the number of times of use of the mold, and a process for producing the molded article including a molding step of transferring a predetermined shape of a mold to a molded article, the molding step comprising an engraving step of engraving an informative mark indicative of the number of times of use of the mold on the mold before the mold is used and an informative mark transfer step of transferring the informative mark to the molded article.

Abstract: An optical connector ferrule of this invention includes a holding portion arranged at a position along an inserting direction of optical fibers to constitute a front surface of the ferrule and having a plurality of first through holes for inserting the optical fibers therethrough and two second through holes for inserting guide pins, the holding portion holding portions of the optical fibers near distal ends thereof, the second through holes and the first through holes having central axes that are substantially parallel to each other, and the first through holes being arrayed in two rows in a direction connecting centers of the second through holes; and an optical fiber tape accommodating portion having an insertion opening for inserting therethrough optical fiber tapes having the optical fibers held by the holding portion, an internal space for partially accommodating the optical fiber tapes, and an injection opening for injecting therethrough an adhesive for adhering and fixing the inserted optical fiber ta

Abstract: Disclosed is a lens assembly constructed of lenses and a lens frame for holding the lenses at predetermined intervals to make optical axes of the lenses coincident. Space walls contacting face-to-face lens surfaces of the two lenses to keep a spacing therebetween are integrally provided in at least three positions at equal intervals in the peripheral direction along an inner peripheral portion of the lens frame. Inner peripheral wall portions for holding at least two lenses in the lens frame, are formed by one of molding dies.

Abstract: The manufacturing process for UV-screening photochromism eye glasses is based on the use of polycarbonate, polymethyl methacrylate or Nylon as substrate to be mixed with spironaphthoxazine or its derivative as photochromism agent along with carrier, hindered phenol type antioxidant, silicone coupling agent, organic phosphorous stabilizer, piperidine type light stabilizer, and UV-absorbent. By mixing two of the last three ingredients and all other substances thuroughly, the mixture is frozen ground or mechanically pulverized to fine particles for injection molding to produce a long-term stable UV-screening photochromism eye glasses.

Abstract: The invention relates to a novel process for the manufacture of mouldings, especially contact lenses, in which a soluble prepolymer comprising crosslinkable groups is crosslinked in solution, and also to mouldings, especially contact lenses, obtainable in accordance with that process. The present invention relates also to novel prepolymers that can be used in the process according to the invention, especially derivatives of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprise from approximately 0.5 to approximately 80% of units of formula I ##STR1## wherein R is lower alkylene having up to 8 carbon atoms,R.sup.1 is hydrogen or lower alkyl andR.sup.

Abstract: A method and apparatus for forming an optical device of a desired shape presses a heat-softened optical material using a set of molds. The optical material is aligned with respect to the molds by two or more aligning members which move around the center of the mold relative to each other. The optical material may also be aligned by inserting a pin into an aligning hole which is fixed to the mold body and has been aligned with respect to the molds.

Abstract: This invention provides a method of molding which can feed the high-viscosity material quickly and accurately as well as with good operability. For achieving quick heating and cooling cycles in a mold, the mold is constructed from a mold material having superior heat-conductivity in such a way that the high-viscosity material can be heated and cooled from outside of the mold.Thereby, this invention comprises:a step for preparing a mold fabricated with high orientation graphite material,a step for feeding high-viscosity material into the recess portion for molding inside said mold in the non-molten state,a step for heating and melting the high-viscosity material in the recess portion via said mold from the outside, anda step for cooling the molten high-viscosity material via said mold and molding it into a desired shape.

Abstract: Retroreflective material is disclosed which is formed of an array of microprisms which reflect light more uniformly by forming a concave curvature in the base face of the prisms.

Abstract: A ferrule includes a cylindrical ceramic main body and a metal or plastic back body mated to an end of the ceramic main body. The cylindrical ceramic main body has an axial bore adapted for holding an optical fiber core in fixed relation to the cylindrical ceramic main body. The metal or plastic back body has an axial, central opening adapted for holding a jacketed portion of an optical fiber which terminates through a stepped or sloped end to a smaller axial, central opening adapted for holding an optical fiber core. At the interface between the cylindrical ceramic main body and the metal or plastic back body, the cylindrical ceramic main body has a substantially planar face and a curving central portion that joins the planar face to the axial bore of the cylindrical ceramic body.

Abstract: An automated demolding apparatus for reliably and repeatedly mechanically separating contact lens mold portions of a mold assembly without damaging the contact lens formed there between. Before demolding, the second mold portion is irradiated by a laser beam, which is absorbed thereby to cause a substantial temperature gradient between the second mold portion and the contact lens being demolded.

Abstract: An optical resin, of which the refractive index continuously changes in a specific direction, is produced by filling a polymerization container with a mixed solution containing at least one type of polymerizable monomer or polymerizable monomer sol and at least one type of substance whose solubility parameter differs by 7 (cal/cm.sup.3).sup.1/2 or less and refractive index by 0.001 or more from those of a polymer produced by polymerization of the monomer, and by subjecting the mixture to polymerization reaction by applying heat or energy rays to the container from outside so that the polymerization reaction starts and progresses preferentially from a particular region of the mixture, thus forming a concentration gradient of the substance having different refractive index.The polymerization container may be made of a polymer which swells and dissolves into the mixed solution from an inner wall thereof.

Abstract: A method and apparatus for releasably securing mold pieces used to mold an artificial eye lens, for example a hydrophilic contact lens. The apparatus includes an ultrasonic welding system to provide directed energy, modified so that the output horn is convex to extend within the outer concave portion of one of the mold pieces and has a shoulder to rest upon the flange of said piece thereby centering it. The method applies directed energy, such as ultrasonic vibrations, through the energy emitter horn to soften or melt then fuse the mating peripheral edge portion of the lens mold pieces.

Abstract: A method of press-molding glass optical elements by press-molding glass, having a high melting point, at a temperature of 650.degree. C. and higher using a die for press-molding glass optical elements which includes a base material having a heat resistance and sufficient strength to withstand press-molding of optical glass elements, a cutting layer on the base material, and a surface protective layer on the cutting layer. The cutting layer is formed of an alloy film containing P and one metal selected from the group Ni, Co, and Fe, and one metal from the group Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, or an alloy film containing Cu and 20 to 80 atom % of one metal selected from the group Ni, Co, Fe, Si, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, or an alloy film containing Si and 20 to 80 atom % of one metal selected from the group Ni, Co, Fe, Cu, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Abstract: The invented methods provide a means for reducing or eliminating manual astments that are required during the fabrication (winding) of fiber optic dispensers. This reduction is accomplished through the use of a fiber placement pattern that is permanently generated on the bobbin winding surface. Filaments, such as optical fibers, are precisely guided during the winding of subsequent filament layers by the embedded crossover pattern baselayer. The embedded crossover pattern baselayer is generated by first winding in a given direction a wire of a pre-selected diameter upon the polymer coating on the bobbin surface. The polymer is allowed to cure partially before the wire is unwound and removed. Afterwards a pre-selected optical fiber is wound in the direction opposite that of the wire winding direction thereby creating crossover patterns which are, then, manually adjusted to be in desired locations on the bobbin axis.

Abstract: A process for providing degassed complementary concave and convex lens molds to filling and mold assembly stations in a continuous or semicontinuous automated soft contact lens manufacturing system. The process includes injection molding the lens molds, immediately transferring the lens molds to an inert gas atmosphere, degassing the lens molds, and filling the lens molds with a polymerizable monomer under the inert gas prior to mold assembly.

Abstract: A contact lens production line pallet system transports contact lens mold materials throughout a facility for producing ophthalmic lenses. Specifically, the contact lens production line pallet system includes a pallet for carrying one or more contact lens mold assemblies throughout a contact lens production line, the pallet having one or more first recesses formed in a surface thereof for receiving either a first mold half or a complementary second mold half, the first and second mold halves when placed together constitute an individual contact lens mold assembly. A conveyor device for transporting the pallet from station to station throughout the production line facility is provided, as is a locating device formed in the pallet surface for enabling precise positioning of the pallet at one or more manufacturing stations in the production line facility.

Abstract: The present invention relates to a process for the production of a polyurethane lens, which comprisesthe step (a) of providing a polyisocyanate compound and two or more polythiol compounds which have different reaction rates with the polyisocyanate compound and adding an alkyltin halide compound to the above polyisocyanate compound, and, after the step (a),the step (b) of mixing the polyisocyanate compound and the two or more polythiol compounds together with the alkyltin halide compound of the general formula (I) to allow them to react, and obtaining a polyurethane lens.

Abstract: A selectively, rotatably adjustable riser pin for aligning a predetermined characteristic on an asymmetrical mold surface with the gate of an injection molding machine for enhanced flow dynamics of the mold material across the mold surface. The riser pin is divided into two co-linear portions which are biased towards one another such that application of a predetermined torque will allow the front riser pin portion, which carries the mold tool, to be rotated independently of the back riser pin portion.

Abstract: The process comprises:(a) the introduction into a mould of a composition which is polymerizable into a transparent organic glass(b) the polymerization of the composition under conditions such that the resulting substrate made of transparent organic glass has at least one thin surface layer polymerized to a degree of progression and/or of crosslinking which is appreciably lower than that of the remainder of the substrate,and optionally (c) a stress-relieving thermal anneal of the substrate.Application to the manufacture of finished or semi-finished optical or ophthalmic items, in particular photochromic optical or ophthalmic items.

Abstract: Method of manufacturing large polycrystalline plates from optical and scintillation materials consists in heating a crystalline blank up to the temperature of 0,5T.sub.melt. <T<T.sub.melt., where T.sub.melt. -melting temperature of the starting material, as well as thermomechanical deformation by means of profiled surface up to the double thickness of the plate to be obtained, after which the blank is deformed again at the same temperature using flat-parallel surface till the specified thickness. Such technology provides the obtaining of large polycrystalline plates of the specified geometrical form with the necessary sizes.

Abstract: A collagen-hydrogel for promoting epithelial cell growth and regeneration of the stroma is shown. Also shown is an optical lens for the eye, fabricated from the collagen-hydrogel, which, when affixed to Bowman's membrane, promotes and supports epithelial cell growth, enables corneal epithelium of the cornea of an eye, during the healing process, to attach to and cover the anterior surface of the lens implanting the same and to regenerate the stroma which grows over the edge of and attaches to the optical lens. Laid down in the layers of the regenerated stroma are new keratocytes and collagen fibial produced from keratocytes. The collagen-hydrogel is a hydrogel polymer formed by the free radical polymerization of a hydrophilic monomer solution gelled and crosslinked in the presence of an aqueous stock solution of collagen to form a three dimensional polymeric meshwork for anchoring collagen. The collagen-hydrogel material has a ratio by weight of collagen-to-hydrogel in the range of about 0.

Abstract: A hydrophilic soft gas permeable contact lens having substantially improved clinical performance by the provision of a sufficient higher proportion of hydroxy acrylic units to silicon units in the lens surface layer, as compared to that existing in the lens core, by the surface treatment of the lens, such as by reacting of the lens surface with polyols and base or acid or by radiation treatment of the base lens to graft, deposit or coat thereon hydroxy acrylic units.

Abstract: The invention enables production of polymer fibrids comprising a polyester which is injected as a low-viscosity jet into a shear field formed by liquid jets, torn apart by the liquid jets and formed into fibrids having a fibril length of from 0.1 to 5 mm by cooling, crystallization and orientation.

Abstract: A composition for a urethane-base plastic lens, comprising:(a) at least one ester compound selected from the group consisting of isocyanate compounds, isothiocyanate compounds and isocyanato-containing isothiocyanate compounds,(b) at least one active hydrogen compound selected from the group consisting of hydroxyl compounds, mercapto compounds and mercapto-containing hydroxyl compounds,(c) a tertiary amine, and(d) a Lewis acid;a plastic lens obtained by heating and curing the composition, and a process for the production of the plastic lens. The composition has a long pot life and can produce an optically uniform plastic lens in a short time.

Abstract: Demolding apparatus for reliably and repeatedly mechanically separating contact lens mold assemblies without damaging the contact lens formed therebetween. The mold assembly includes a frontcurve mold having a central mold section with a surrounding flange, and a corresponding backcurve mold also having a central mold section with a surrounding flange, with a contact lens being molded therebetween. A support pallet is provided for supporting the mold assembly. A wedge separating fixture provides at least one separating wedge positioned between the spaced flanges of the mold assembly, and the wedge separating fixture and support pallet are translated relative to each other to progressively separate the frontcurve mold from the backcurve mold.

Abstract: Unsaturated polyester resin-based compositions that are modified for unexpected improvement in uniform, low optical distortion and/or improved tint speed by the addition of one or more additives selected from an allylic ester and/or an acrylic monomer, together with an exotherm depressant, making the modified polyester resin-based composition commercially viable for casting ophthalmic lenses. The additive(s) and exotherm depressant are useful to modify the polyester for sufficient enhancement of optical distortion and/or tint speed such that any unsaturated polyester resin, capable of producing a clear, low color casting, will be improved sufficiently to provide a composition having the required properties for an ophthalmic lens.

Abstract: Disclosed is a process for producing an ultraviolet radiation absorbing contact lens from a lens shaped polymer having hydroxyl groups pendant therefrom and having dispersed therein a UV absorbing agent substituted with at least one anhydride group which is exposed to basic conditions such that the hydroxyl groups react with the anhydride groups on the UV absorbing agent. As a result the UV absorbing agent becomes fixed to the polymer through the formation of a covalent ester bond.

Abstract: Hydrophilic contact lens molds are transiently modified to provide a water dynamic contact angle equal to or less than 100.degree. by treatment with a wetting agent which may be water or a surfactant composition which provides a mold surface having a water wetting force of at least 70 mg to afford a reduction in lens hole defects in hydrophilic contact lens manufacture.

Abstract: An implantable ophthalmic lens manufactured at least partly out of soft, elastic and pliable material substantially in the shape of a saucer is described. It includes an outer optical face forming one side of the lens, and an inner optical face forming the other side of the lens. A center portion of the inner optical face of the lens as well as the lens rim each have the shape of meniscus derived from the corresponding meniscus of a liquid precursor prior to solidification, the center portion meniscus and the rim meniscus being connected by an annular ring, all surfaces of the lens except the center portion of the inner optical face and the lens rim being replicas of a solid mold from which it is formed. The inner optical face center portion and the lens rim have the shape of a liquid precursor solidified in contact with an inert fluid.

Abstract: A rotary polygonal mirror for a deflection scanning device includes a regular prism-shaped main body portion consisting of a resin material, a projecting portion which projects from an upper surface of a central portion of the main body portion, and a reflection film formed on side surfaces of the main body portion. The projecting portion consists of the same resin material as the resin material of the main body portion. The main body portion and the projecting portion are integrally molded by injection molding or injection compression molding. A gate portion in the molding is provided to the projecting portion.

Abstract: A retroreflective article comprising a transparent base sheet having first and second broad faces, the second face being substantially planar and the first face having an array of substantially hemi-spheroidal microlenses thereon, the microlenses being wider and shorter than portions of true spheres, the shape of the microlenses and thickness of the base sheet being such that collimated light substantially orthogonally incident to the array is focused approximately at the second face, wherein the second face has a coating of a nacreous pigment composition thereon. The article can include an optional layer of adhesive over the reflective layer to permit the article to be adhered to a document as a tamper-indicating, authenticating, and protective overlay. Special images can be formed within the article to enhance the security provided thereby. Also, a method for making such base sheets, and a method for making a forming master.

Abstract: A substrate according to the present invention is applicable to an optical disc on which an information signal is recorded. Formed on the substrate are prepits in the form of irregularities which generates a tracking error signal upon detected. The substrate serving as a electro-acoustic transducer comprises a flat surface portion including at least a portion on which a recording layer and/or a reflecting film layer are formed, and plural pairs of prepits formed on the portion. Two prepits constituting each pair of the prepits are disposed at positions offset from a center of a virtual recording track such that the center of the virtual recording track is interposed between the two prepits. The substrate is produced by injection-molding a synthetic resin material having a light-permeability and has a thickness of 1 mm or less at the portion on which the recording layer and/or the reflecting film layer are formed.

Abstract: An apparatus for filling and assembling mold parts for a contact lens includes a first automated station for receiving a plurality of front curve contact lens mold parts and depositing in each front curve mold a predetermined amount of a polymerizable monomer or monomer mixture, and, a second automated station for receiving the plurality of front curve mold parts and assembling each front curve mold part with a back curve mold part under vacuum to prevent entrapment of gas between the mold parts. The front curve mold parts are transported to the first and to the second automated stations by a pallet having registration guides that cooperate with the second station to register the pallet prior to assembly of the mold parts.

Abstract: A method and apparatus releasably secure mold pieces used to mold an artificial eye lens, for example a hydrophilic contact lens. The apparatus includes an ultrasonic welding system to provide directed energy, modified so that the output horn is convex to extend within the outer concave portion of one of the mold pieces and has a shoulder to rest upon the flange of said piece thereby centering it. The method applies directed energy, such as ultrasonic vibrations, through the energy emitter horn to soften or melt then fuse the mating peripheral edge portion of the lens mold pieces.

Abstract: This invention describes a method for fabricating an intraocular lens made rom clear Teflon.TM., Mylar.TM., or other thermoplastic material having a thickness of about 0.025 millimeters. These plastic materials are thermoformable and biocompatable with the human eye. The two shaped lenses are bonded together with a variety of procedures which may include thermosetting and solvent based adhesives, laser and impulse welding, and ultrasonic bonding. The fill tube, which is used to inject a refractive filling material is formed with the lens so as not to damage the lens shape. A hypodermic tube may be included inside the fill tube.

Abstract: The present invention relates to a process for the production of a polyurethane lens, which comprises the step (a) of providing a polyisocyanate compound and two or more polythiol compounds which have different reaction rates with the polyisocyanate compound and adding an alkyltin halide compound to the above polyisocyanate compound, and, after the step (a), the step (b) of mixing the polyisocyanate compound and the two or more polythiol compounds together with the alkyltin halide compound of the general formula (I) to allow them to react, and obtaining a polyurethane lens.

Abstract: A polymeric infrared window (10) is described which comprises a sheet of polymeric material (14). Sheet 14 further may comprise a layer of molecular weave polymer material (34) fixed to a electromagnetic interference shield (32). In addition, a polymeric sheet (42) may be embossed with a binary defractive pattern (40) to create a polymeric defractive lens (38).

Abstract: A smooth contoured structure is formed from a planar surface by etching mesas of equal height into the surface and heat treating the structure to mass transport material above the desired contour to fill in voids below the desired contour. In an alternate embodiment, an optical element is formed using a patterned layer of sacrificial material and thermally treating the sacrificial layer to form a precursor contour line. The line is then transformed onto a substrate and smoothed to form the optical element.

Abstract: A liquid filling method and in particular a lens material liquid filling method suitable for manufacturing a plastic lens. A thermal sensing portion (2a) of a temperature sensor (2) is set and kept to a temperature different from that of a liquid (3). The liquid (3) is poured into a vessel (8), a change of an output from the temperature sensor (2) is detected when the surface of the liquid (3) comes into contact with the thermal sensing portion (2a) by temperature detecting means (5), and control means (6) determines that the liquid surface has reached a desired level and sends a pouring stop command to a pouring mechanism (7) to complete the filling of the liquid.

Abstract: There is disclosed a method for molding an optical element, by preparing an upper mold member and a lower mold member for press molding a glass material, heating the mold members together or individually to a predetermined temperature, deforming the glass material according to molding faces of the mold members by a pressing force applied to the mold members, then transferring the mold members and the molded glass to a cooling step and subsequently taking out the molded glass by opening the mold members, thereby transferring the optically functional faces corresponding to the molding faces of the mold members, to the glass material.

Abstract: A method and apparatus releasably secure mold pieces used to mold an artificial eye lens, for example a hydrophilic contact lens. The apparatus includes an ultrasonic welding system to provide directed energy, modified so that the output horn is convex to extend within the outer concave portion of one of the mold pieces and has a shoulder to rest upon the flange of the one piece thereby centering it. The method applies directed energy, such as ultrasonic vibrations, through the energy emitter horn to soften or melt then fuse the mating peripheral edge portion of the lens mold pieces.

Abstract: A polymer is placed and heated within a cylinder 1. Then the polymer is subjected to a pressure and extruded in the form of fibers from a nozzle 3. When a diffusible material is injected from a nozzle 5 through a capillary cylinder 4 into the central portion of the polymer melt, the diffusible material gradually diffuses from the central portion toward the peripheral portion while flowing toward the injection port of the nozzle 3. The material extruded from the nozzle 3 is cooled by air and wound on a drum 7 through a roller 6. Fiber-like molded product has a distribution of refractive index which continuously varies from the central portion toward the periphery portion to result in a light-converging or light-diverging plastic optical transmission medium. Reversely, even though the polymer melt is extruded from the nozzle 5, there can be obtained an optical transmission medium also having a region where the refractive index continuously varies.

Abstract: A lens, having an optical power surface, which may have multiple radii portions or aspherical portions as well as spherical portions, is molded in a coined mold. A pair of core pins, positioned within the mold cavity during the lens forming process, will produce a pair of haptic-mounting holes within the lens. As the lenses are subsequently tumbled to remove flash, indentations will form adjacent to the haptic-mounting holes. These indentations allow for tangential attachment of the haptic to the lens which, in turn, enables maximum flexibility without exceeding the width of the optic.

Abstract: The invention relates to a process for the solvent-free and dry production of particles from plastics. According to the invention, the plastic is heated to form a viscous material, in this form, is conveyed as material stream through an outlet into a comminution device and there, with spraying of a pressurized liquid atomization medium against it, is comminuted into fibrids and/or fine particles.

Abstract: The present invention relates to a manufacturing method of a polymer GRIN lens which is used for focusing light in connections for example between two or more optical fibers and between an optical fiber and a light source in the optical communication field. The manufacturing method of a GRIN lens according to the present invention utilizes a characteristic of polystyrene that its refractive-index is decreased by sulfonation. The method includes polymerizing a sphere or rod made of a directional monomer that is capable of sulfonating like a styrene, together with a cross-linking agent, and a polymerization initiator; swelling the polymerized cross-linked polymer by using a predetermined solvent; and sulfonating the swollen cross-linked polymer using a sulfuric acid. Accordingly, the present method can be easily controlled to obtain the desired refractive-index distribution since the refractive-index distribution is determined by the diffusion of the sulfuric acid as a sulfonation.

Abstract: Retroreflective prisms are formed with windows thereon by removing a portion of the prism mold on one prism pair leaving the apex of the prism intact. In this manner smaller prisms are formed adjacent larger prisms. Optionally, the optical axis of the prisms may be tilted with respect to one another, preferably in a negative direction. The smaller prisms with windows provide increased brightness and optimize the retroreflection light.