Abstract: An improved method of producing transparent diamond laminates employs a substrate which is removed once a second layer is deposited over the diamond coating, thereby exposing a smooth diamond surface. The second coating should have a refractive index substantially identical to diamond, with zinc selenide and titanium dioxide being particularly preferred. Diamond films having two smooth surfaces may be produced by simultaneous deposition on parallel, opposed substrates until the two diamond films merge together to form a single film or plate, followed by removal of at least a portion of the two substrates.

Abstract: A fast, relatively inexpensive and simple method for producing a finished plastic aspheric multifocal or progressive lens from a preformed lens which has a predetermined lens correction (i.e., curvature or prescription) at its optical center. The method includes providing a mold; providing an optical photoactivated resin composition; providing a preformed plastic lens; contacting the preformed lens with the mold such that the surfaces of the preformed lens and the mold form a cavity enclosing the resin composition; and curing the resin composition upon application of heat and ultraviolet radiation. The cavity formed by the preformed lens and the mold is shaped to correspond to the desired change in curvature of the mold surface. The preformed lens may also be cast with a thin non-prescription layer which acts as a carrier for the multifocal or progressive region of the finished lens. This allows casting of lenses without employing either expensive conventional optical gaskets or back molds.

Abstract: A one-piece bicomposite intraocular lens having a soft foldable central optic portion and a hard, stiff haptic portion made from two dissimilar polymeric materials wherein the soft polymeric material is soft enough to fold into a smaller dimension for insertion through a surgical incision which is smaller than the diameter of the optic portion and the second hard polymeric haptic material provides a stiffness sufficient to properly hold the intraocular lens in place within a patient's eye. The hard polymeric haptic material is joined to the outermost peripheral surface of the soft central optic material by means of an interpenetrating polymer network to form a one-piece bicomposite intraocular lens, In an alternative embodiment the stiff haptic portion has a further soft material at its terminus to protect the eye tissues at the point of contact without sacrificing the lens positioning properties of stiff haptics.

Abstract: Member of polymethylmethacrylate, polysulfone, polymer or a like material with a plurality of holes arranged in a predetermined, geometrical configuration. The holes are derived at through a procedure of repetitive drawing. Prior to the first drawing operation, each of the holes is filled with a material which is soluble to a certain chemical, yet drawable along with the base material. The member of material can be square, drawn to a reduced cross-sectional area as a square, the reduced cross-sectional members positioned with respect to each other and drawn again in a further operation, and repeated accordingly so that the cross-sectional area of each hole is reduced in proportion to each drawing step. Dependent upon the final drawing step, a subsequent member is provided which includes holes of a significantly reduced cross-sectional area. The member can be utilized as either a contact lens, an intracorneal inlay, an intraocular lens, a medical filter, or a like structure with small holes.

Abstract: A thin film of molten polypropylene resin extruded from a T die is pressed and cooled with a chill roll equipped with a hologram relief master plate on its peripheral surface, whereupon a hologram pattern is simultaneously formed as an integral part of the polypropylene resin sheet being molded. Since the polypropylene resin has a Rockwell hardness of at least 70, the hologram pattern formed in the resulting hologram forming sheet is less likely to be damaged or lost during subsequent processing.

Abstract: The present invention is directed to a process for manufacturing a cladded optical fiber. The cladding and core are halide materials. An interface for inhibiting radiation scatter is provided at the boundary between the halide cladding and the halide core. The process steps include extruding a first halide or halide core from a first chamber, and extruding a second halide or halide cladding from a second chamber into contact with the halide core. The halide cladding is joined to the halide core at the boundary.

Abstract: A microstructure-bearing composite plastic article can be superior, both in microstructure and in physical properties, when it is a composite of a tough, flexible substrate, at a surface of which is microstructure formed of a cured oligomeric resin having hard segments and soft segments, which cured resin is substantially confined to the microstructure portion of the composite. Such a composite plastic article can be made by depositing an uncured oligomeric resin composition onto a master negative molding surface, filling the cavities by moving a bead of the composition between a substrate and the master, and curing the deposited composition by ultraviolet radiation while keeping the temperature during curing from rising not more than about 30.degree. C. above a typical use temperature of the finished composite plastic article.

Abstract: A flow cell for optically analyzing a liquid sample is coated with a fluoropolymer having a refractive index less than the refractive index of water.

Abstract: A process for forming an intraocular lens with haptics having high fracture toughness mixing solid particles with an uncured polymer matrix and introducing the uncured mixture into a mold. Ultrasonic energy is then applied to the mold until the uncured mixture begins to solidify. Sufficient heat is then applied to the polymer mixture to completely cure the polymer. The cured polymer which will form the haptics, is then removed from the mold and a hole for forming the optic is formed in the cured polymer. An uncured polymer matrix suitable for use, when cured, as an optic, is then introduced into the hole and cured. An intraocular lens is then machined from the resulting cured composition.

Abstract: A fast, relatively inexpensive method and simple is disclosed for producing a finished plastic multifocal or progressive lens from a preformed lens which has a predetermined lens correction (i.e., curvature or prescription) at its optical center. The disclosed method produces a finished lens which has a multifocal or progressive region without changing the lens correction at the optical center of the lens.

Abstract: A method of making an intraocular lens including providing a fixation member having a proximal end portion with the proximal end portion including an elongated filament, converting a region of said filament at said proximal end portion from a first configuration into an enlargement having a rounded surface and attaching an optic about the proximal end portion of the fixation member to attach the fixation member to the optic.

Abstract: The PMMA (Polymethyl methacrylate) plastic used to produce one-piece intraocular lenses is modified by a novel thermoplastic pressure forming process to produce a much tougher material with improved mechanical properties. The improved material exhibits greater ductility and fatigue resistance than conventional cast PMMA sheet, resulting in a one-piece lens that is less prone to breakage from implantation or use.

Abstract: Method of preparing superior scratch resistant coatings which are particularly well suited for use in combination with unsaturated polyester gel coats in applications where a smooth, high gloss, durable, scratch resistant surface is desirable, such as in marine and cultured marble applications, include compositions comprising at least one polyfunctional monomer having 3 or more acryloloxy groups per molecule, preferably 5 or more acryloloxy groups, and either at least one N-vinyl imido group containing monomer or at least one polyallylglycidyl ether containing compound. These coating compositions are cured either by exposure to ultraviolet radiation or by thermal means, preferably using organic peroxides.

Abstract: Plastic ophthalmic lenses are coated with a scratch-resistant coating using a spin coating process. The lenses are separated from lens mold pieces, and the lenses are routed through a coating system where the lens coating is applied. A conveyor moves the lens mold pieces toward an inspection station while the corresponding lenses are moving through the coating system. The operation of the lens coating system and the conveyor are coordinated so that the coated lens and the lens mold pieces from which that lens was made are delivered as a group to the inspection station.

Abstract: A method for decoration of paper or plastic sheeting and other substrates, involving a novel technique for coating and embossing the substrate. The paper or plastic sheeting is supplied with a coating of thermosensitive material, as by extrusion. The coated sheet is heated to adequately soften the coating, such as by use of a heated cylinder, and remote heat sources such as infrared heaters. The softened sheet surface is then decorated using an embossing member, to provide a diffraction pattern or hologram. Use of an embossment pattern of lesser depth than the surface roughness of the sheet before embossing provides attractive decorative patterns.

Abstract: The present invention provides a method of coupling an electrical signal to an optical fiber (14). The method includes encapsulating an electrical connector (21), an optical semiconductor device (18,36), and a fiber optic cable (14) all in one body (23,38,41,42). The semiconductor device (18,36) is electrically coupled to the electrical connector (21), and is also aligned to the fiber optic cable (14). The components are encapsulated in one single body (23,38,41,42). The single body (23,38,41,42) permanently maintains the alignment. The electrical connector (21) portion of the body (23,38,41,42) provides an easy means to couple the fiber optical cable (14) to electrical signals.

Abstract: Method for forming an optical element having an optical coating thereon by replication having the steps of preparing first and second molds having polished surfaces which are to be replicated, depositing a soluble inorganic salt to form a release layer, depositing an optical coating in reverse order upon the release layer, supplying liquid material between the molds and in contact with the optical coating, causing the liquid material to solidify and form a bond with the optical coating, separating the molds from the solidified material with the optical coating adherent to the solidified material with separation occurring between the mold and the optical coating in the parting layer and removing any remaining portions of the parting layer from the optical coating.

Abstract: A method of manufacturing a contact lens with an iris simulating pattern by moulding comprising applying to the mould at least two differing designs so as to form an overall pattern. This overall pattern is transferred to the surface or surfaces of the contact lens during moulding and curing thereof, where the designs transferred interact with each other to substantially cover the iris and produce a coloured natural simulation of the iris of the eye when in use.

Abstract: Hydrophobic casting moulds are treated with electrical discharge, such as corona discharge, to provide enhanced compatibility with hydrophilic objects introduced into the mould, without interfering with the release properties of the mould. A preferred embodiment involves treatment of contact lens casting moulds with corona discharge to provide improvements in the lens manufacturing procedure, as well as enhancement in the quality of the contact lenses themselves. The invention is particularly applicable to the production of contact lenses having a colored iris pattern imprinted thereon.

Abstract: A decorative substrate consisting of a paper base sheet coated with a thermoplastic material, involving a novel technique for coating and embossing the substrate. The paper sheeting is supplied with a thermoplastic material, as by coating or extrusion. The coated sheet is heated to adequately soften the coating, such as by use of a heated cylinder, and remote heat sources such as infrared heaters. The softened sheet surface is then decorated using an embossing member, to provide a diffraction pattern or hologram. Use of an embossment pattern of lesser depth than the surface roughness of the sheet before embossing provides attractive decorative patterns.

Abstract: The present invention relates to implants (intraocular lenses) for implantation in the human eyeball to replace the natural crystalline lens. In general, the implant includes a body which includes anterior and posterior surfaces, an axis, and a periphery. The body is formed of a transparent material having an index of refraction which varies with a predetermined profile from the axis to the periphery of the body. In a first embodiment, the body is formed of one element having a convex-convex shape and an index of refraction which decreases in the direction away from the axis of the body. For dual-focus capabilities, the body has an inner and an outer zone with separate gradient profiles and surface curvatures, or an inner zone which is offset from the axis and is the center of the gradient profile. The inner and outer zones provide focusing for nearby and distant objects respectively.

Abstract: A fast, relatively inexpensive and simple method is disclosed for producing a finished plastic multifocal or progressive lens from a preformed lens which has a predetermined lens correction (i.e., curvature or prescription) at its optical center. The method comprises providing a mold; providing an optical quality resin composition; providing a preformed plastic lens contacting the mold such that the surfaces of the preformed lens and the mold form a cavity enclosing the resin composition; and curing the resin composition. The cavity formed by the preformed lens and the mold is shaped, among other purposes, (1) to correspond to the desired change in curvature, and (2) to ensure that the lens correction at the optical center of the resulting lens is substantially the same (preferably the same) as the predetermined lens correction at the optical center of the preformed lens.

Abstract: Methods are disclosed for the manufacture of individual small lenses, which may have gradient indices of refraction. A pedestal is provided having a conduit therein and an end surface the perimeter of which may be circular or elliptical. The perimeter is defined by a sharp edge. The pedestal is supported with the end surface horizontal and facing downwards. The intersection of the conduit and the surface, also defined by a sharp edge, forms an orifice through which at least one of the liquid monomers for forming the lens is fed. Gradient index small lenses are formed by suspending a first monomer from the horizontal end surface of the pedestal and then, via the orifice, introducing the second monomer at a rate which equals the rate of inter-diffusion of the second monomer into the first monomer. Alternatively, both monomers are both fed, in mixed condition, through the orifice in continuously varying proportions. The monomer(s) are cured in the pendant condition.

Abstract: A fast, simple and relatively inexpensive method for forming disposable molds for use in casting optical quality lenses. A method of producing a disposable mold having a casting surface is disclosed which comprises providing a base master having a first contacting surface; providing a casting surface master having a second contacting surface having a shape corresponding to the shape of the casting surface; providing a resin composition; contacting the base master and the casting surface master such that the first and second contacting surfaces form a cavity enclosing the resin composition, wherein the cavity is shaped to correspond to the shape of the disposable mold; and curing the resin composition to form the disposable mold.

Abstract: A method for manufacturing an intraocular lens from a cell cast sheet of high molecular weight polymethylmethracrylate (PMMA). A lens blank having a lens generation area with a surface contoured to correspond to the desired contour of the finished lens is machined from the sheet of PMMA to a predetermined precompensated size larger than desired to acccommodate normalizing shrinkage. The lens blank is normalized by heating the blank in a vacuum oven. The vacuum is released from the oven by introducing dry nitrogen. A stamping die is provided. An optical embossing surface of the stamping die is contoured as a physical negative of the lens generation area and bears a physical negative of the desired optical surface structure of the lens, such as a multifocal diffractive zone plate. The embossing surface of the stamping die is forced into engagement with the surface of the lens blank at a predetermined stamping pressure and for a predetermined stamping dwell time.

Abstract: A soft intraocular lens with an insert which can be molded into an optic having an optic attachment member embedded in the optic and a haptic attachment member extending out of the optic to which a haptic may be connected. The insert permits the easy attachment of the haptic to the optic without subjecting the haptic material to the rigors of the processes by which the soft optic is made.

Abstract: A process for producing an optical recording medium, including the steps of: melt-extruding a resin to form a resin sheet; passing the resin sheet under pressure between a first roller having a predetermined unevenness pattern and a second roller disposed opposite thereto before the resin sheet is hardened, thereby to transfer the unevenness pattern to a surface of the resin sheet; and forming a recording layer having an organic coloring matter on the surface of the resin sheet provided with the unevenness pattern; wherein the steps are conducted while the resin sheet is moved.

Abstract: First and second hydrogel lens members are configured to be ultrasonically welded to one another. Both the first and second lens members have an annular bonding surface. The second lens member has an energy director extending from its bonding surface. The energy director has a generally rectangular cross section, a height of 0.127 to 0.178 millimeter, and an extended smooth surface of 0.127 to 0.381 millimeter width adapted to engage the bonding surface of the first lens member. The smooth extended surface of the energy director of the second lens member is mated with the bonding surface of the first lens member, and pressure in the range of 55.1 to 68.9 KN/m.sup.2 applied thereto to force the lens members together. Ultrasonic energy is applied to the lens members for a weld time period of 0.15 to 0.22 second. Following the weld period, the application of ultrasonic energy is discontinued for a hold time period of 0.15 to 0.25 second. The application of pressure is discontinued following the hold time period.

Abstract: A method and apparatus to continuously harden articles made of visible light-curable resins, including continuously moving the articles to be hardened relative to a multiplicity of sources of visible light which are independently controllable to be able to vary the radiation to which the articles is exposed during its passage while independently controlling the temperature at which this takes place; and apparatus to accomplish this such that a large number of the objects to be irradiated passing through the hardening apparatus have the same exposure history to the visible light and to heating or cooling respectively. As the result, there is substantially no variation in the physical properties of these photo-polymerized products.

Abstract: A method of encasing a luminous translucent tubing (12,32) of a non-linear complex geometrical configuration in a transparent outer member (14,34) and forming a passage (25,35) of annular radial cross section therebetween, which method comprises coating the exterior of the tubing (12,32) with a viscous temporary material (17,47) which solidifies to provide a coating with smooth exterior surface, coating the temporary substance (17,47) with a permanent forming material in a viscous liquid state which hardens to form a rigid transparent outer member (14,34) in coextensive surrounding relation to the tubing (12,32) and its coating of temporary material (17,47), applying heat to said coating of temporary material at a temperature above the melting point of the temporary material and below the softening temperature of the outer member, and removing the temporary material from between the translucent tubing (12,32) and the transparent outer member (14,34) while supporting the translucent tubing in fixed relation to

Abstract: A method to continuousky harden light-curable resins, by irradiating at least one shaped article made of a light-curable resin by continuously moving the article past a multiplicity of light sources while changing the flux of the irradiated light in multiple steps corresponding to the moving positions of the object and an apparatus to accomplish this method including means to continuously move the article relative to the multiple irradiation sources and means to adjust the flux density in multiple steps corresponding to the moving positions of the article. Specifically, the flux density of the light irradiated on the moving article is changed stepwide depending upon the position and the location of the article and the polymerization speed of the article and the hardening depth can be controlled in relation to its position and time.

Abstract: An intraocular lens comprising at least one fixation member and an optic. The fixation member has an attachment region with a roughened outer surface. The attachment region is received within the optic to attach the fixation member to the optic. The roughened outer surface improves the adhesion of the fixation member to the optic.

Abstract: A transmissive screen for use in a video projector or the like and a manufacturing method thereof is provided wherein a UV-curable resin is coated on a back film or a mold. One surface of a lens surface of opposite shape is formed by the mold. The UV-curable resin is sandwiched between the back film and the mold, ultraviolet rays are irradiated on the UV-curable resin and the screen is released from the mold, thereby forming a transmissive screen in which the lens surface is formed on one surface by the UV-curable resin and the back film is formed on the other surface. Thus, the screen can be reduced in weight and thickness, and can be mass-produced.

Abstract: A method and apparatus for producing a plastic lens element having a gradient index of refraction is disclosed in which first and second monomer-containing compositions, each having a different index of refraction, are injected into a centrifugal mold. Precise control of the gradient index is achieved by varying the ratio of the two monomers over a predetermined number of steps during the filling process.

Abstract: A method for attaching a polymethylmethacrylate haptic having a colored core to an optic of an intraocular lens, containing the steps of providing the periphery of the optic with a pair of intersecting holes, inserting an end of the haptic into one hole, inserting an end of a polymethylmethacrylate anchor strand having a colored core into the second hole so that the end of the anchor strand and the end of the haptic intersect, aiming a laser capable of a transmitting energy of a visible wavelength at the intersection of the first and second holes, firing the laser through the optic at the point of intersection of the end of the haptic and the end of the anchor strand, wherein the optic transmits, but essentially does not absorb, the laser energy and the core the anchor strand and the core of the haptic absorb a portion of the laser energy sufficient to fuse the end of the anchor strand and the end of the haptic at their point of intersection.

Abstract: A method and system for replicating microstructures surface relief patterns, such as diffraction patterns including holograms, by casting. A liquid casting resin is held between a surface relief master of the microstructure to be replicated and a substrate while the resin is hardened by actinic radiation curing. Application of resin to edges and discontinuities of the master is avoided in order to reduce undesirable build-up of resin on these areas of the master. The hardened resin surface relief replica may optionally be coated with a discontinuous graphical pattern of a clear or colored paint that eliminates the effect of the surface relief pattern in the regions so coated.

Abstract: A process for the manufacture of a molded contact lens containing a transparent central visual region circumscribed by a colored iris portion which comprisesa. coating a colored liquid which is either curable or thermoplastic in a mold for making a contact lens onto a surface thereof where the iris portion of the lens is formed to produce a colored film thereon which film contains a surface exposed to the interior of the mold and a surface in contact with the mold,b. charging the mold with the resin used to form the body of the lens while maintaining the colored film in the iris portion and configuring the resin about the colored film whereby the surface of the film becomes integral with the body of the lens and the surface of the film becomes part of the outer surface of the lens when the molded lens is removed from the mold.

Abstract: An improvement in the epoxy plastic element of a laminated, glass-plastic, ophthalmic lens structure, and a method of effecting the improvement, are disclosed. The improved element is cast from a casting mix in which the ingredients are maintained in certain relationships to each other to provide an optically clear casting essentially free of striations. The cast material is gelled at a low temperature not over about 100.degree. C., and may then be cured at a temperature up to 200.degree. for a period of at least two hours.

Abstract: A method and a device are disclosed wherein a shrinkable polymer material is formed in situ in a mold without defects and with no internal stresses. A monomer or polymer solution is injected into the mold and solidified sequentially through the mold by exposure to an agent such as ultraviolet radiation, with simultaneous addition of monomer or polymer solution into the area of the mold not yet exposed to the solidifying agent. By controlling the rate at which the solidifying agent is moved across the mold and the monomer or polymer solution is injected into the mold, the resulting product completely fills the mold and is stressfree.

Abstract: A diffractive contact lens in relief includes a smoothing layer (50) of optically transparent material having a smooth outside surface (51) and placed over the optical surface (16) in relief so as to immerse the relief.

Abstract: A solid-state image pickup device comprises a semiconductor chip, a package with a recess in which said semiconductor chip is fixed, and a transparent protective member for protecting an image pickup surface of the semiconductor chip and guiding a light image onto the image pickup surface. The transparent protective member includes a transparent resin layer for covering the image pickup surface and the upper surface of the package without forming a space therebetween, and an incident surface formed on the resin layer in parallel to the image pickup surface. A method manufactures a solid-state image pickup device having a construction described above by using a mold.

Abstract: A plastic lens having a hard coat film and/or anti-reflecting film strongly adhered and having no defects such as yellowing, milky turbidities, cracks is provided. The plastic lens can be produced according to the present invention by forming an anti-reflecting film and/or a hard coat film on the working surfaces of a pair of molds, pouring a monomer liquid into the space between said molds and a ring gasket and polymerizing the monomer therein. Formation of the anti-reflecting film and/or the hard coat film can be carried out by coating of a hard coat solution or by a vacuum deposition of inorganic substances. When the anti-reflecting film and/or the hard coat film is formed by coating of a hard coat solution, a hard coat solution containing at least one release agent is applied to the working surfaces of the molds, or, after applying a release agent to the working surfaces of the molds, a hard coat solution containing no release agent is applied to the release agent layer.

Abstract: A balloon for an intraocular lens, which is a unitary elastic hollow body made of an elastomer and having a convex lenticular shape without projections along its circumference, which gives, when inserted in a lens capsule, a configuration corresponding substantially to the shape of the lens capsule, said hollow body having a wall thickness of from 0.001 to 0.1 mm at its optical portion and a diameter of from 6 to 13 mm, and capable of being inflated in the lens capsule to form an intraocular lens when a light transmitting injection material is injected into the hollow body.

Abstract: Composite acrylic polymer rods having clear central regions and colored peripheral regions are prepared by polymerizing a flowable solution comprising acrylic monomer, dye and, dissolved therein, acrylic polymer, around a rod of acrylic polymer. Alternatively, a rod of acrylic polymer surrounded by a flowable mixture comprising partially polymerized acrylic monomer and dye is subjected to polymerization conditions to polymerize the flowable mixture.

Abstract: A mold for forming a magnetic tape cassette and a method for multi-color molding a magnetic tape cassette or the like. Sprue-runners connected to submarine gates used in making at least portions of the cassette are formed with notches near the submarine gates to reduce the cross-sectional area of the sprue-runners. As result, the sprue-runners can be easily cut off from the body of the cassette by breaking the notched portions.

Abstract: A twisted FRP structure having sufficient strength and flexibility is produced by providing a rod member disposed centrally and twist a plurality of side strands twisted around the rod member in the same direction at a predetermined pitch. At least the side strand includes a composite strand having an FRP element from by impregnating fibers with an uncured thermosetting resin and a thermoplastic coating on such FRP element, the thermosetting resin being cured after the side strands are twisted around the rod member. The twisting pitch is not less than 25 times the outside diameter of the FRP element in the side strand.

Abstract: The present invention provides a process for manufacturing a magneto-optic disc comprising at least a transparent substrate, a magneto-optic recording film, and a protecting film made of resin for protecting the magneto-optic recording film, comprising the steps of forming the magneto-optic recording film over the entire one side surface of the transparent substrate; providing in a portion adjacent to the peripheral edge of the magneto-optic recording film an annular groove extending in depth through the magneto-optic recording film to the transparent substrate; and forming the protecting film over the surfaces of the magneto-optic recording film and the annular groove.

Abstract: A process for releasing leachable substances from a polymeric contact lens blank. the contact lens is confined in a cavity within a carrier to permit the hydration of the lens without permitting it to invert or roll over. A fluid flow is introduced into the cavity about the lens to extract leachable material from the lens. The process significantly reduces the amount of leaching fluid that is used and the amount of time that is needed for hydration, washing and extraction.

Abstract: In a process for mass producing optical storage sheets, an elongate film of a liquid crystalline material is fed lengthwise along a path through an aligning gate. The aligning gate applies to successive areas of the film a field which aligns the molecules. The field may be an electric field and/or a shear field. An aligning layer, such as a surfactant layer may also be used for alignment of the film areas. The aligned film may then be cut into pieces for use as microfiches or microfilms. The film material is preferably a liquid crystal polymer material.

Abstract: A method for setting an ophthalmic lens in a pair of goggles having a flat front transparent lamina for permitting vision and also having a shielding rim surrounding the lamina extending towards the face of the wearer for the abutment thereon is characterized by a lens secured inside the shielding rim adjacent the lamina. The ophthalmic lens has a flat plane adjacent the lamina separated therefrom by an air gap. A first silcone-base caulking is deposited between the periphery of the lens and the shielding rim up to a level substantially corresponding to the thickness of the air gap. This first caulking has a viscosity sufficiently sag-proof to maintain the caulking at the periphery of the gap during its hardening. A second caulking having a lower viscosity is deposited on the top of the first caulking up to a level corresponding to the top of the lens. The caulking is selected to be free of toxic and corrosive gas. The lens has a peripheral groove to improve the adherence of the second caulking.