METHOD FOR MANUFACTURING A LENS AND LENS MADE IN

ACCORDANCE THEREWITH

DESCRIPTION

Field and Scope of the Invention

The present invention refers to a method for manufacturing a lens for lighting arrangements, adapted for use in connection with lighting apparatus intended for application in residential, office, commercial and similar buildings, road lighting applications, urban design and street furniture applications, and the like. The present invention also refers to a collimating lens made in accordance with such method.

The present invention is preferably, although not solely, suitable for use in view of optimizing the luminous flux emitted by lighting apparatus comprising LED- based light emitting elements.

State of the Art and Background of the Invention

Largely known in the art are lighting devices, which comprise a plurality of LED-based light emitting elements. For a same luminous power or intensity being output, these lighting devices allow for a drastic reduction in the amount of power needed to supply them, as compared with traditional lighting apparatus based on incandescent lamps, neon glow lamps, or the like. Such lighting devices are also largely known to further comprise a plurality of lenses, generally in the number of one lens for each LED-based light emitting element. Each lens, as made of a plastic or polymeric material, has such optical geometry as to be able to concentrate and collimate the luminous flux emitted by the LED in one or more desired directions in a manner that is consistent with the geometrical arrangement of the LED-based light emitting elements on a related support.

A drawback that is encountered with such prior-art lighting devices lies in the

fact that, for such flaws as for instance material shrinkage, which may occur as the lenses are moulded, and/or air pockets, which may form in the lenses during moulding, and which may alter or modify the desired optical geometry, to be limited as far as possible, each lens is produced individually. Each lens is then associated to the corresponding LED element and mounted on a support, such as for instance an electronic power-supply board supplying the same LED elements, thereby unavoidably implying an increase in the ultimate production costs of the lighting devices.

A further drawback of such prior-art lighting devices lies in the fact that the marked, high degree of directionality of light rays emitted by them gives rise to undesired dazzling occurrences that, in certain fields of application, such as for instance in public environment lighting and /or road lighting applications, may turn out as being particularly dangerous.

Therefore, it is a purpose of the present invention to provide a method for manufacturing a collimating lens for lighting apparatus, which allows for production costs to be sensibly reduced.

A further purpose of the present invention is to provide a collimating lens for lighting apparatus, which allows the luminous flux to be optimized, and which is effective in enabling possible dazzling problems to be reduced or even totally done away with.

In view of doing away with the drawbacks and disadvantages as generally encountered in the prior art, and reaching the above-noted aims and advantages, along with further ones that will become apparent in the following disclosure, the Applicant has studied, found and provided the present invention, as well as experimentally corroborated the effectiveness thereof.

Summary of the Invention

According to the present invention, all these aims are reached in a method for manufacturing a lens and a lens produced according to such method, which incorporate the features and characteristics as defined and recited in the

independent claims appended hereto.

Further features or modified embodiments of the present invention are set forth and defined in the sub-claims.

In compliance with the above-noted purposes, a method for manufacturing a lens according to the present invention can be applied to make and provide a collimating lens for lighting apparatus comprising a plurality of light emitting elements arranged in accordance with a pre-defined geometrical pattern on a support and/or power-supply member.

The manufacturing process according to the present invention comprises a modelling step, in which there is defined a shape of the collimating lens having a pre-determined optical geometry. Such optical geometry is adapted to define a plurality of optical paths extending from the lens and associated to the light rays generated by the corresponding light emitting element, so as to obtain a luminous flux travelling out of the lens in one or more directions as desired and predetermined in the design process.

The manufacturing method also comprises a step, in which there is provided a forming mould, which has such shape and form as to be able to form the collimating lens. The mould has a shape that is consistent with the previously defined optical geometry, and is provided in such manner as to ensure that at least part of the moulding surfaces thereof are made to a desired degree of accuracy. This is aimed at ensuring that conjugate surfaces are provided on the lenses, which perform a specular, i.e. mirror-like action on the light rays generated by the light emitting elements, and the desired luminous flux is obtained.

The manufacturing method further includes a moulding step, in which the lens is moulded by means of said forming mould.

According to an aspect of the present invention, the forming mould is provided so as to be capable of moulding a plurality of lentiform elements made in a one- piece unitary construction, these lentiform elements being in the number of at least two, but advantageously three, four or even more, adapted to be coupled to the

support and/or power-supply member so as to allow, in a subsequent assembly step, each such lentiform element to be coupled to a related light emitting element in a manner that is consistent with the geometrical arrangement of the light emitting elements on the support and/or power-supply member, without inducing any mispositioning of adjacent lentiform elements relative to each other, not even on a micrometrical scale.

According to a preferred embodiment of the present invention, the light emitting elements are of the LED type.

According to a modified embodiment of the present invention, the afore mentioned moulding step of the method is carried out in the form of an injection- compression process including injecting and compressing a plastic or polymeric material in the forming mould, i.e. a process that includes overcompressing the injected material prior to its setting in the mould. The possibility is given in this way for the material to be closely packed together, i.e. densely compacted to thereby ensure that such flaws as air pockets and the like are eliminated from the lentiform elements being moulded, while keeping material shrinking occurrences within fully acceptable limits.

According to another modified embodiment of the present invention, the forming mould is configured so as to obtain - on each lentiform element - at least an optical refraction surface comprising a plurality of micro-optic elements. These micro-optic elements are arranged and adapted to refract at least part of the light rays travelling out of the lentiform elements according to a plurality of optical paths extending in a variety of directions as pre-defined at the design stage. The possibility arises in this way for the likelihood for dazzling problems to possibly occur to be drastically reduced and even totally done away with, since the light rays come out of the lens by following non-parallel optical paths, thereby substantially enabling the luminous flux to be kept in the desired direction, while at the same time preventing the same light rays from concentrating into a single direction.

According to a still further modified embodiment, said forming mould is made and provided so that the lentiform elements are integrally incorporated, i.e. as a one-piece unitary construction, in a backing piece having a shape that is consistent with the geometrical arrangement of the light emitting elements on the support and/or power-supply member. Such backing piece comprises at least one surface having corrugations adapted to intercept part of the light rays passing in each lens to radiate them, i.e. send them forth in a direction that is substantially coincident with the direction of the luminous flux generated by the collimating lenses.

As noted hereinbefore, the present invention also refers to the collimating lens for lighting apparatus obtained with the above-described method.

According to an aspect of the present invention, this lens comprises a plurality, i.e. at least two, but advantageously three, four or even more, of lentiform elements made in a one-piece unitary construction to be then coupled to the support and/or power-supply member so as to allow each such lentiform element to be subsequent assembled to a related light emitting element.

Short Description of the Drawings

Features and advantages of the present invention will anyway be more readily understood from the description of a preferred, although not sole embodiment that is given below by way of non-limiting example with reference to the accompanying drawings, in which:

- Figure 1 is a top view of a collimating lens made in accordance with the present invention;

- Figure 2 is a first side view of the lens shown in Figure 1 ;

- Figure 3 is a second side view of the lens shown in Figure 1 ;

- Figure 3A is a schematical view of a detail of Figure 2;

- Figure 4 is a first axonometric view of the lens shown in Figure 1 ;

- Figure 5 is a second axonometric view of the lens shown in Figure 1 ;

- Figure 6 is a cross-sectional view according to the line Vl-Vl in Figure 1 ;

- Figure 7 is a top view of a modified embodiment of the lens shown in Figure 1 ;

- Figure 8 is a schematical side view of the lens shown in Figure 7;

- Figure 8A is a schematical side view of a detail of Figure 8;

- Figure 9 is a first diagrammatical view of the radiating pattern of the lens made according to the present invention;

- Figure 10 is a second diagrammatical view of the radiating pattern of the lens made according to the present invention;

- Figure 11 is a third diagrammatical view of the radiating pattern of the lens made according to the present invention;

- Figure 12 is an axonometric view of a lighting apparatus comprising a collimating lens according to the present invention.

Detailed Description of a Preferred Embodiment

With reference to above-listed Figures, a manufacturing method according to the present invention can advantageously be used to provide a collimating lens 10 adapted to be applied on to LED-based light sources, while it shall be right away appreciated that such collimating lens 10 is anyway to be understood as being adapted to be also applied to light sources of any other kind.

The manufacturing method according to the present invention includes a modelling step, in which there is defined a geometrical shape of the lens 10 that is

adapted to define a pre-determined optical geometry. In the ultimate form thereof, the collimating lens 10 is adapted to intercept the light rays being emitted by one or more LEDs 11 and passing through lentiform elements 16 associated therewith, and to concentrate them into a luminous flux that comprises the fluxes travelling out of each lentiform element 16 and the lens 10 in at least one pre-determined direction, thereby defining a plurality of optical paths within the lens 10.

Defined in this step is furthermore a pre-determined geometrical pattern for arranging each lentiform element 16 within a backing piece 12, in such manner as to enable the lens 10, i.e. the lentiform elements 16 to be associated in a way that is consistent with the arrangement of the LEDs 11 on a board 40 fitted to ensure power supply to the same LEDs.

In this particular case, the lens 10 comprises four lentiform elements 16 arranged in a square-shaped pattern in the backing piece 12, but it shall be appreciated that the lens 10 is to be understood as being capable of comprising any different number of lentiform elements 16 arranged according to any different geometrical pattern in the backing piece 12. The same backing piece 12 might be provided in any different geometrical shape so as to be capable of fitting, i.e. adapting to one or more particular boards 40.

In this step, each lentiform element 16 is further defined according to a substantially circular geometry adapted to intercept the light rays being emitted in an omnidirectional manner from each LED 11. In particular, each lentiform element 16 is defined so as to comprise a first lower surface 24 having an at least partially spherical contour, as schematically illustrated in Figure 3A, wherein said surface is arranged so as to have a convexity thereof facing the LED 11. This first surface 24 is adapted to reflect at least part of the light rays being emitted by the LED 11 associated therewith in directions extending obliquely relative to the plane described by the board 40 inside the lentiform element 16. Diagrammatically represented in Figure 3A are the patterns of the optical paths of three light rays emitted by the associated LED 11 according to, i.e. along three segments R1 , R2, R3, which have a different direction of emission and are reflected by the first surface 24 towards the interior of the lentiform element 16 according to, i.e. along

three corresponding segments R1 \ R2' and R3', respectively.

In addition, the first surface 24 is adapted to also intercept at least part of the light rays being emitted in a direction that extends substantially orthogonally to the board 40, and to propagate them through the same lentiform element 16. Illustrated in Figure 3A there is a light ray coming from the LED 11 according to, i.e. along a segment R4, emitted in the above-noted orthogonal direction and passing through the lentiform element 16 without any reflection.

Each lentiform element 16 furthermore comprises a second surface 25 which lies on the side flank of the lentiform element 16 and is obtained in the form of a rotation about an axis of symmetry x of a parabolic contour. This second surface 25 becomes narrower, i.e. tapers towards a base portion 17 of the lentiform element 16 and is adapted to reflect towards the interior of the same lentiform element 16 and concentrate most of the light rays being reflected by the first surface 24 towards an upper portion thereof comprising a refractive portion 22. Illustrated in Figure 3A there are three segments R1 ", R2" and R3" that are obtained as a reflection from the second surface 25 of the corresponding segments R1 ', R2' and R3', respectively.

In addition, each lentiform element 16 is defined so as to comprise, in the upper portion thereof that is arranged for outputting the light rays, a diffractive portion 18 along with the afore-mentioned refractive portion 22. Such diffractive portion 18 is arranged to allow for diffusion, in different directions, of the light rays that fail to be reflected by the second surface 25 towards the refractive portion 22. This diffractive portion 18 (Figures 1 and 6) comprises a radial optics 19 in the shape of a circular crown, or annulus, having a pre-defined extension, and featuring circular corrugations 18A around the refractive portion 22. These circular or ring-shaped corrugations 18A have a pitch P, i.e. are spaced from each other by a centre-to-centre distance P of approximately 1.65 mm, and have a cross- sectional circular contour with a radius R of approximately 0.9 mm (Figure 3A). Shown in Figure 3A there is an optical path of a light ray R3 as reflected by the second surface 25 and being output from the diffractive portion 18.

The refractive portion 22 (Figures 1 , 3A, 4) is arranged to allow for emission of most light rays being emitted by the LED 11 associated therewith, and comprises an output surface 26 for letting out the light rays from the lentiform element 16, which is in an ovoid or spherical shape comprising a plurality of micro-optical elements 23. These micro-optical elements 23 are adapted to refract the light rays coming from the first surface 24, or the second surface 25, and being output from the lentiform element 16, in such manner as to diffuse the light rays in non-parallel directions. This in view of preventing a luminous flux comprising a plurality of light rays from being emitted in a single direction, and avoiding possible dazzling problems in this way.

The above-mentioned micro-optical elements 23 are such as to protrude from the output surface 26 and may be in an either spherical or aspheric, e.g. ovoid shape being sized and having a height relative to the output surface depending on the required luminous flux, so as defined at the modelling stage. An optimum shape of these micro-optical elements 23, in view of obtaining an efficient flux while avoiding dazzling occurrences and related problems, is a shape of a spherical kind having a diameter of approximately 0.2 mm and a height relative to the output surface 26 of approximately 4 hundredths of a millimetre. In the illustrations in Figure 3A, as well as in all other accompanying Figures, the micro- optical elements are shown in intentionally enlarged proportions for reasons of greater clarity.

Indicated in Figure 3A there are two segments R2" and R3" corresponding to the segments R1 and R2 emitted by the LED 11 , which are incident from the interior of the lentiform element 16 upon a micro-optical element 23 of the output surface 26.

In a preferred manner, the modelling step is carried out by making use of electronic data processing means, such as for instance an electronic data- processing computer, which are appropriately programmed and arranged for modelling the geometrical shape and simulating the luminous flux emitted in accordance with or depending on the desired geometrical shape. The possibility is in this way given for a variety of emission patterns of the luminous flux to be

simulated according to and depending on both the geometrical shape of the lens 10 and the lentiform elements 16 and the optical properties of the material to be used in making the same lens 10, thereby enabling a geometrical shape to be defined, which will provide an optimum in terms of luminous flux, actually.

Illustrated in Figures 9, 10 and 11 there are diagrams plotting the light radiation patterns of a collimating lens 10 according to the present invention, wherein it can be noticed that a large part of the luminous flux emitted by the lens 10 concentrates in a pre-defined direction, which coincides with the one set in the modelling step, since it shows components that slopes down in directions lying close to, i.e. approaching the pre-determined one.

Defined in the modelling step there is furthermore a diffractive surface 28 of the backing piece 12 (Figures 2, 4 and 5), wherein said diffractive surface is provided to extend below the same backing piece 12. This diffractive surface 28 is arranged and adapted to intercept part of the light rays being emitted by the LEDs 11 associated therewith, and diffuse them onto the same backing piece 12. This enables the luminous flux of the collimating lens 10 to be partially emitted also from the backing piece 12 itself, thereby allowing light to be perceived as being emitted all over the surface of the lens 10, i.e. by the entire lens 10 and not solely by parts thereof. Such diffractive surface 28 comprises longitudinal corrugations 29 extending rectilinearly and parallel to each other.

According to a modified embodiment illustrated in Figures 8 and 8A, the diffractive surface 28 is modelled in such manner as to comprise a plurality of recesses 30, or cuneiform micro-optical elements, having a conical, frusto-conical or partially conical shape and receding into the backing piece 12, arranged according to a regular pattern on the diffractive surface 28. These cuneiform, i.e. wedge-shaped micro-optical elements 30 are adapted to act as light guides to intercept the portion of the light rays emitted by the LED 11 that circulates in the backing piece 12, so as to substantially deflect them into the direction x. Figure 8A can be noticed to schematically illustrate a light ray R5 being intercepted by a cuneiform micro-optical element 30 and being output from the lens 10 according to a segment R5'. The diffractive surface 28 further comprises wrinkled, i.e. rough

portions 3OA showing a surface roughness typical of a sandblasting finish. These rough portions 3OA are provided in an interpolated arrangement between adjacent ones of the above-mentioned cuneiform micro-optical elements 30 and are adapted to further assist in intercepting the light rays circulating in the backing piece 12.

According to a further modified embodiment, which is not illustrated in the accompanying drawings, the diffractive surface 28 comprises a plurality of protrusions jutting from the same surface 28 and having a conical, pyramidal or prismatic shape.

Defined in the modelling step being considered there are also support pillars 13, which are provided to allow the lens 10 to rest on the board 40. These support pillars 13 further comprise dowel-like portions 15 adapted to plug into corresponding bores in the board 40 so as to facilitate mechanical coupling of the collimating lens 10 to the board providing power supply to the LEDs 11. The support pillars 13 located at the corners are advantageously provided with a bore 14 for a screw used to fasten the lens to the same board 40 to be received thereinto.

The inventive manufacturing method further comprises a step, in which there is provided a forming mould having such shape and contour as to be adapted to mould the collimating lens 10 according to the definition of the geometrical shape of the same lens 10, and has in fact a form that is consistent with the geometrical form as defined in the modelling step. The forming mould is provided in such manner as to ensure that the forming surfaces thereof that are conjugate to the first surfaces 24 and second surfaces 25 of the lentiform elements of the collimating lens 10 have a surface accuracy lying at least in the nanometre order. Such forming surfaces of the mould are made of metal and are machined and finished with the help of diamond tools, such as those used in ultra-high-precision CNC machining centres or units for surface processing and machining in the field of nanotechnologies, in order to obtain the above-cited surface accuracy. In this way the possibility is given for conjugate surfaces free of mechanical deformations of any kind to be provided on both the lens 10 and the lentiform elements 16, so

that the first surface 24 and the second surface 25 thereof have the capability of reflecting most of the light rays travelling into the lentiform element 16.

The manufacturing method further comprises a moulding step for forming the collimating lens 10 by a process that includes injecting a clear, i.e. transparent plastic or polymeric material at a melting temperature thereof, i.e. in the molten state thereof, into the afore-considered forming mould. This plastic material may for instance be polycarbonate. In a preferred embodiment, the plastic material is the one carrying the trade-name Makrolon. The lens is moulded by means of an injection-compression process, i.e. a process wherein the plastic or polymeric material is injected and over-compressed in the forming mould.

The injection of the material takes place at a point corresponding to a central, substantially symmetric region of the lens 10 in the ultimate form thereof, in such manner as to allow for the material being injected into the forming mould to distribute evenly therein. Material injection takes place by means of a so-called hot-runner nozzle system so as to prevent the injection point from being visible on the lens 10.

Thereupon, the forming mould is caused to undergo a compression action so as to drive the injected material into a more closely, i.e. densely packed and evenly compacted form and increase the homogeneous character of the physical properties of the same plastic material, thereby both avoiding residual or internal stresses in the polymeric or plastic material and preventing such flaws as air pockets, vacuums, sinks or the like from forming in the lentiform elements 16. Such compacting action is effective in further enabling material shrinkage to be controlled as the plastic material injected in the mould goes through the setting process thereof, so as to keep shrinkage within pre-defined, allowable limits. In this way, the thus moulded collimating lens 10 will be able to most accurately fit the board 40, on which it shall then be applied, while at the same time allowing each lentiform element 16 to be automatically associated to a corresponding LED 11.

The possibility arises in this way for the material to be compacted inside the

mould, thereby effectively doing away with any possible flaw, such as vacuums, air pockets or the like, that may occur in the lentiform elements and, at the same time, keeping material shrinkage within generally allowable and acceptable limits.

As a result, the collimating lens 10 provided in accordance with the present invention can be applied on to the related support board 40, which may in turn be arranged so as to provide power supply to the LEDs 11 , in quite quick and convenient a manner, in a process that enables several lentiform elements 16 to be correctly associated to said board 40 at the same time, actually.

The present invention also refers to a lighting apparatus 50, such as for example an apparatus for road or street lighting purposes, comprising one or more collimating lenses 10 provided in accordance with the present invention. The lighting apparatus 50 (Figure 12) comprises one or more support and/or power- supply boards 40, in which the LEDs are arranged according to a pre-defined geometrical pattern. The boards 40 are mechanically coupled to a so-called heat- sink 52, which is made of a metal material and is adapted to absorb and dissipate heat generated by the LEDs when they are turned on. The heat-sink 52 may be provided with a surface for coupling to the boards 40 that shall not necessarily be perfectly planar, but - as illustrated in Figure 12 - may rather be a surface consisting of several portions that are not co-planar, so as to allow the boards 40 to be applied thereon in such arrangement as to provide a luminous flux being output in several directions.

The lighting apparatus further comprises one or more collimating lenses 10, each one of which being mechanically coupled to a corresponding board 40. Each collimating lens 10 is applied so as to rest with its pillars 13 on the same board 40, while the dowel-like portions 15 (not shown in Figure 12) fit into the corresponding bores.

The lighting apparatus also comprises a containment shell, or casing, formed of an upper shell 56 and a lower shell 58 that are adapted to be coupled together so as to provide a casing for containing the heat-sink 52 and the boards 40 along with the collimating lenses 10. Both the upper shell 56 and the lower shell 58 are

preferably made of a material such as clear or colourless polycarbonate.

The lighting apparatus 50 is electrically energized by means of a power-supply device (not shown in the Figures), which may be provided either inside or outside the containment casing.

It shall be readily appreciated that the method for manufacturing a collimating lens according to the present invention, as well as the same collimating lens provided with such method and the lighting apparatus made in accordance with the present invention as they have been described hereinbefore may be the subject of a number of modifications and/or additions of parts and/or steps without departing from the scope of the present invention.

It will further be readily appreciated that, although the present invention has been described with reference to some particular exemplary embodiments in this specification, anyone skilled in the art would be fully capable of identifying and providing many other equivalent embodiments of the method for manufacturing a collimating lens according to the present invention, as well as of the same collimating lens provided with such method and the lighting apparatus using such collimating lens, all of them featuring the characteristics as recited and defined in the appended claims and, as a result, falling within the scope as defined by them.