A lens arrangement

Abstract

A lens arrangement comprising first lenslets, second lenslets and saddle-shaped lenslets. The first and second lenslets curve in opposite directions to one another. The highest magnitude for any curvature of each first lenslet is within a predetermined percentage of the highest magnitude for any curvature of all neighboring second lenslets to the first lenslet. Similarly, the highest magnitude for any curvature of each saddle-shaped lenslet is no greater than the highest magnitude for any curvature of all neighboring first and second lenslets to the saddle-shaped lenslet.

Description

[0001] A LENS ARRANGEMENT

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of lens arrangements, and in particular, to the field of lens arrangements for beam spreading.

[0004] BACKGROUND OF THE INVENTION

[0005] There is an ongoing desire to improve artificial lighting arrangements, which are used to provide artificial light in a wide variety of environments, such as in domestic, industrial and / or public settings.

[0006] It is common for spotlighting lamps and luminaires to have an optical system comprising collimating optics configured to form a light beam. To improve characteristics of the light beam (e.g., reduce irregularities or color non-uniformity), a known technique is to provide a lens arrangement for performing beam spreading at the exit of the optical system. This beam spreading lens arrangement comprises an array of small, closely packed lenslets.

[0007] One known parameter that correlates with quality of the beam after beam spreading is the tessellation shape or arrangement of the array of lenslets.

[0008] Another known parameter that also correlates with quality of the beam is the sharpness of the boundaries between the lenslets. Ideally, these boundaries should be infinitely sharp, but this is impractical or impossible to achieve in practice. Instead, lenslets are connected by fillets, where a fillet is a rounded or curved segment that connects one lenslet to another. The presence of fillets between the lenslets affects beam spreading and peak intensity in an uncontrollable or indefinable manner. This can, if the lens arrangement is intended for color mixing, also lead to additional noise artifacts in the color mixing.

[0009] As noted above, it has traditionally been thought that smaller and sharper fillets (i.e., fillets with an extremely small radius of curvature) will improve beam quality after beam spreading. However, decreasing the radius of curvature of fillet significantly increases the complexity of manufacturing, e.g., requiring specialist tooling.

[0010] It would be desirable to provide an alternative or improved lens arrangement, that is easy to manufacture without significantly affecting the quality of the beam after beam spreading. SUMMARY OF THE INVENTION

[0011] The invention is defined by the claims.

[0012] According to examples in accordance with an aspect of the invention, there is provided a lens arrangement for performing beam spreading. The lens arrangement comprises an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets. For each first lenslet, a maximum magnitude of the curvature of said first lenslet is deviating at the most by a predetermined percentage from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet. Areas between the first and second lenslets are connected by saddle-shaped lenslets having a first curvature in a first plane and a second, opposite curvature in a second plane perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle-shaped lenslet, wherein the predetermined percentage is less than 25%.

[0013] The present disclosure proposes a new form of lens arrangement. A lens arrangement comprises two arrays of lenslets, i.e., two separate pluralities of lenslets. A lenslet may, by itself, be considered to be an example or instance of a lens. An array of first lenslets forms a lens arrangement which also acts as a lens by itself. A lenslet may be formed in any shape, but generally takes a curved shape which defines one or more values of curvature for the lenslet. In particular, a maximum magnitude of the curvature of a lenslet is the highest value for the sharpest part of the lenslet.

[0014] The first lenslets are connected to one another by a plurality of second lenslets of opposite curvature. In this way, the second lenslets function as connecting portions between the first lenslets. It will be understood that if the first lenslets are convex with respect to a light outputting surface of the lens arrangement, then the second lenslets will be concave.

[0015] A maximum curvature of each second lenslet is (substantially) the same as a maximum curvature of any of first lenslet neighboring said second lenslet. It has been advantageously identified that such designs provide a similar amount of beam control as existing lenslet arrays (comprising lenslets connected by relatively small fillets), but are easier to manufacture. For instance, this type of lens arrangement may even be produced by 3D printing, which is not easily possible to achieve with a high degree of quality for existing or conventional designs of lenslet arrays. Saddle-shaped lenslets fill spaces between the first and second lenslets. This facilitates increased flexibility in the positioning and arrangement, e.g., tessellation, of the first and second lenslets. In particular, it has been advantageously identified that the use of first, second and saddle-shaped lenslets facilitates non-gridlike arrangements (e.g., for increased and alternative flexibility of design) of the lens arrangement whilst still achieving good beamspreading functionality by the lens arrangement. In the context of the present disclosure, a gridlike arrangement of lenslets comprises lenses arranged in parallel rows and / or columns, e.g., to form a linear or rectangular (e.g., square or oblong) arrangement of lenslets.

[0016] The predetermined percentage is less than 25% (e.g., 20%) and / or a percentage less than 15% (e.g., 10%).

[0017] In some examples, a center of each first lenslet defines a center of a respective Voronoi cell of a Voronoi tessellation; and a center of each second lenslet is located at a vertex of one or more Voronoi cells defined by the centers of the first lenslets.

[0018] In some embodiments, a maximum magnitude of the curvature of said first lenslet is the same as the average of the maximum magnitudes of the curvature of all second lenslets neighboring said first lenslet.

[0019] In some examples, maximum magnitude of curvature of all first lenslets and all second lenslets is the same. In other examples, the maximum magnitude of curvature may change over the lens arrangement, e.g., to achieve a desired beam spreading function performed by the lens arrangement. The variation over the lens arrangement may depend on the variation of the incoming light distribution over the lens arrangement, which will be defined by the properties of the light source and any other optical elements positioned between the light source and the lens arrangement. If these properties (e.g., variations in angular and / or in color distribution) vary strongly over the exit window, it may be advantageous to vary the curvature and / or the size (footprint) of the lenslets over the lens arrangement.

[0020] The footprint of the array of first lenslets upon a lens plane in which the lens arrangement lies may be less than the combined footprint of the array of second lenslets and the saddle-shaped lenslets upon the lens plane. This provides sufficient space and / or area for the second and saddle-shaped lenses to have the desired curvature with respect to the first lenslets.

[0021] In some examples, the footprint of the array of first lenslets upon a lens plane in which the lens arrangement lies is the same as footprint of the array of second lenslets upon the lens plane. This approach effectively aims to make the first and second lenslets have similar beam shaping properties (on average) across the lens arrangement, assuming that the first and second lenslets share similar individual beam-shaping properties. In the context of this embodiment, two footprints are considered to be the same if they are the same size within a predetermined error margin (e.g., ± 5% or ± 1%).

[0022] The array of first lenslets may be arranged in a non-rectangular and non-linear tessellation pattern. The proposed approach is particularly advantageous in that is facilitates the arrangement of the first lenslets in any arbitrary pattern to achieve novel patterns for performing beam spreading. Grid-like patterns have a disadvantage in that the grid pattern is commonly visible in the beam distribution.

[0023] By way of example, the array of first lenslets may be arranged in a hexagonal or phyllotaxis tessellation pattern.

[0024] In some examples, the minimum radius of curvature of each first and second lenslet is no less than 1 mm.

[0025] The array of first lenslets may comprise no less than 100 first lenslets, e.g., no fewer than 1000 first lenslets.

[0026] The number of second lenslets may be substantially the same as the number of first lenslets.

[0027] There is also provided a lighting device comprising a light emitting element configured to emit light; and any herein disclosed lens arrangement configured to receive light emitted by the light emitting element.

[0028] There is also proposed a method of manufacturing a lens arrangement for performing beam spreading, the method comprising milling a substrate to define any herein disclosed lens arrangement. Thus, the method comprises mill the substrate to define a lens arrangement comprising: an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is deviating at the most by a predetermined percentage from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet, wherein the predetermined percentage is less than 25%; wherein areas between the first and second lenslets are connected by saddle-shaped lenslets having a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle-shaped lenslet. There is also proposed a method of manufacturing a lens arrangement for performing beam spreading, the method comprising 3D printing to define a lens arrangement comprising: an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is deviating at the most by a predetermined percentage from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet, wherein the predetermined percentage is less than 25%; wherein areas between the first and second lenslets are connected by saddle-shaped lenslets having a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction, wherein, for each saddle- shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle-shaped lenslet.

[0029] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0032] Figures 1 and 2 illustrates a portion of a lens arrangement;

[0033] Figure 3 illustrates a saddle-shaped lenslet;

[0034] Figure 4 illustrates a portion of an existing lens arrangement;

[0035] Figure 5 illustrates a portion of a proposed lens arrangement;

[0036] Figure 6 illustrates an example lens arrangement; and Figure 7 illustrates an example lighting device.

[0037] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The invention will be described with reference to the Figures.

[0039] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0040] The invention provides a lens arrangement comprising first lenslets, second lenslets and saddle-shaped lenslets. The first and second lenslets curve in opposite directions to one another. The highest magnitude for any curvature of each first lenslet is within a predetermined percentage deviating from the highest magnitude for any curvature of all neighboring second lenslets to the first lenslet. Similarly, the highest magnitude for any curvature of each saddle-shaped lenslet is no greater than the highest magnitude for any curvature of all neighboring first and second lenslets to the saddle-shaped lenslet.

[0041] Embodiments may be employed in any form of lighting device, particularly those designed to provide a collimated beam such as spot luminaires, spot lamps, downlighters, accent lighting device and / or wall (light) washing devices.

[0042] In the context of a present disclosure, a curvature is a measure of the amount of curving of a lenslet. The greater the curvature, the greater the surface of the curve deviates from a plane. Thus, a curvature is a measure that may be considered to be the reciprocal to the radius of curvature of the lenslet. A curvature may be measured or defined in two-dimensions (e.g., the curvature of a curve) or in three dimensions (e.g., the curvature of a surface). Approaches for determining a curvature are well known in the art. A measure of curvature is often represented by the term K.

[0043] A magnitude of a curvature is an absolute value of the curvature (e.g., ignoring any sign of the curvature). A maximum magnitude of a curvature of a lens (or lenslet) refers to the largest magnitude of a curvature measured at any point on the lens / lenslet, representing the sharpest point at the lens / lenslet.

[0044] Figures 1 and 2 provides a top-down view of a portion of a lens arrangement 100 according to an embodiment, for the purposes of improved contextual understanding.

[0045] The lens arrangement 100 comprises an array of first lenslets 111, 112, 113; an array of second lenslets 121, 122, 123 and a plurality of saddle-shaped lenslets 131, 132, 133. It will be appreciated that for illustrative clarity, only a subset of the aforementioned lenslets have been explicitly labelled in Figure 1.

[0046] For the purposes of illustrative clarity, the first lenslets are depicted with stippling, the second lenslets are depicted with cross hatching, and the saddle-shaped lenslets are depicted with no shading. Each first lenslet 111, 112 113 has a curvature of the same first sign. Thus, each first lenslet curves in the same direction, e.g., in the same direction away from a plane in / on which the lens arrangement lies.

[0047] Each second lenslet 121, 122, 123 has a curvature of a same second sign, which is opposite to the first sign. Thus, if each first lenslet is convex with respect to the plane in / on which the lens arrangement lies, then each second lenslet is concave with respect to said plane (and vice versa).

[0048] The first and second lenslets are interspersed with one another. Thus, the second lenslets are positioned or spread throughout the array of first lenslets 111, 112, 113.

[0049] In practice, each first and / or second lenslet may take the shape of an elliptic paraboloid, e.g., a dome. However, it will be appreciated that a lens may take the shape of any ellipsoid, sinusoid or any other free shape domed structure.

[0050] For each first lenslet, the maximum magnitude of the curvature of said first lenslet is limited or otherwise defined by the maximum magnitude of the curvature(s) of any neighboring second lenslets to said first lenslet. Neighboring second lenslets may include any second lenslet that makes contact with the first lenslet and / or any second lenslet for which no other first lenslet lies between said second lenslet and the first lenslet.

[0051] A maximum magnitude of the curvature of a lenslet is the highest absolute value (i.e., magnitude) of the curvatures at all points across the lenslet. Thus, if a magnitude of a curvature is measured at each point on a lenslet, then the largest of these magnitudes is the maximum magnitude of the curvature of the lenslet.

[0052] In particular, for each first lenslet, the maximum magnitude of the curvature of said first lenslet is within a predetermined percentage deviating from the average of the maximum magnitude(s) of curvature(s) of all neighboring second lenslets to said first lenslet.

[0053] The predetermined percentage is a percentage less than 25% (e.g., 20%) and / or a percentage less than 15% (e.g., 10%), e.g., less than 10%, e.g., less than 5%. The lower the percentage, the more uniform the local beam distribution of light transmitted through the lens arrangement in the (local) region surrounding any individual first lenslet. However, higher percentages may be desired in some instances for improved ease of manufacturing, and have been identified as proving a better compromise without significantly affecting the uniformity of light transmitted through the lens arrangement within a local region.

[0054] Put mathematically, this can be expressed as:

[0055] Where 11 is the first lenslet max (|K(.)|) is the maximum magnitude of the curvature of a lenslet 1, Pl is the predetermined percentage, i identifies a neighboring second lenslet to the first lenslet such that 12i represents the ith neighboring second lenslet, N is the number of neighboring second lenslets to the first lenslet 11.

[0056] Areas between the first and second lenslets are connected by saddle-shaped lenslets. Thus, each continuous unfilled space between the first and second lenslets is filled with a respective saddle-shaped lenslet.

[0057] Figure 3 conceptually illustrates an example of a saddle-shaped lenslet 300, for improved contextual understanding.

[0058] Each saddle-shaped lenslet has a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction. In particular, the first direction may connect two first lenslets together, with the second direction connecting two second lenslets together. Put another way, the first direction may extend between two first lenslets and the second direction may extend between two second lenslets. The first and second directions are perpendicular to one another.

[0059] Thus, each saddle-shape lenslet has a shape resembling a (portion of a) hyperbolic paraboloid.

[0060] For each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the maximum magnitude of the curvature of any first or second lenslet neighboring said saddle-shaped lenslet.

[0061] More specifically, a first curvature is measured in any first plane Pl that intersects or is parallel to the first direction. Each first plane is perpendicular to the plane in / on which the lens arrangement lies. The second curvature is measured in any second plane P2 that intersects or is parallel to the second direction. Each second plane is perpendicular to the plane in / on which the lens arrangement lies and is perpendicular to all first planes.

[0062] From Figure 3, it will be clear that the saddle-shaped lens will have two portions that rise in the first plane Pl (e.g., to meet a respective first lenslet) and two portions that fall (e.g., to meet a respective second lenslet) in the second plane P2. The use of saddle-shaped provides a transition or connection between the first and second lenslets.

[0063] For improved beam spreading uniformity, in some examples, the maximum magnitude of the curvature of each saddle-shaped portion is within a second predetermined percentage deviating from the average of the maximum magnitude of curvature(s) of all neighboring first and second lenslets to said saddle-shaped lenslet. In this context, a neighboring first or second lenslet comprises / consists of only the first and second lenslets that contact the saddle shaped lenslet.

[0064] The second predetermined percentage may be the same as the predetermined percentage previously mentioned.

[0065] The second predetermined percentage may, for instance, be a percentage less than 25% (e.g., 20%) and / or a percentage less than 15% (e.g., 10%), e.g., less than 10%, e.g., less than 5%. The lower the percentage, the more uniform the local beam distribution of light transmitted through the lens arrangement in the (local) region surrounding any individual first lenslet. However, higher percentages may be desired in some instances for improved ease of manufacturing, and have been identified as proving a better compromise without significantly affecting the uniformity of light transmitted through the lens arrangement within a local region.

[0066] As best illustrated in Figure 2, in particularly preferred examples, a center of each first lenslet 111, 112, 113 defines a center of a respective Voronoi cell 210 (illustrated with dashed lines) of a Voronoi tessellation. In general, a Voronoi tessellation or diagram comprises a plurality of Voronoi cells 210 (illustrated with dashed lines). The center of each first lenslet may define the center of a respective one of the plurality of Voronoi cells. A center of each second lenslet 121, 122, 123 is preferably located at a vertex of one or more Voronoi cells defined by the centers of the first lenslets.

[0067] In this configuration, a second lenslet may be considered to neighbor a first lenslet if a center of said second lenslet is located at the vertex of the Voronoi cell having a center defining by said first lenslet.

[0068] The proposed approach advantageously facilitates the placement or tessellation of the first and second array of lenslets according to any desired pattern or arrangement, without significant loss in beam quality of light emitted through the lens arrangement. In particular, the proposed approach advantageously allows the first array of lenslets to be positioned in any non-linear and non-rectangular (i.e., non-gridlike) arrangement, pattern, or other configuration. For instance, the array of first lenslets may be positioned in a hexagonal or phyllotaxis tessellation pattern. More particularly, the proposed configuration and restrictions means that the beam spreading properties of all neighboring lenslets are like one another. This facilitates consistency and uniformity in the beam spreading performed by the lens arrangement.

[0069] Of course, it will be appreciated that the curvatures of lenslets may differ across the lens arrangement (more generally), dependent upon the desired beam spreading characteristics of the lens arrangement. Appropriate approaches for controlling the beam spreading will be readily apparent to the suitably skilled person in the art.

[0070] To provide sufficient space for achieving the desired (maximum) curvature(s) of the first, second and saddle-shaped lenslets, the footprint of the array of first lenslets upon a lens plane in which the lens arrangement lies may be less than the combined footprint of the array of second lenslets and the saddle-shaped lenslets upon the lens plane.

[0071] In this way, the footprint of the first lenslets on a plane in which the lens arrangement lies is less than the combined footprint of the second lenslets and the saddle- shaped lenslets. In other words, the lenslets are configured such that the area occupied by the two-dimensional projection of the second lenslets and saddle-shaped lenslets onto the lens plane is greater than the two-dimensional projection of the first lenslets onto the lens plane.

[0072] In particular embodiments, the footprint of the array of first lenslets upon a lens plane in which the lens arrangement lies is the same as footprint of the array of second lenslets upon the lens plane.

[0073] One approach for modifying or controlling the beam spreading properties of the lens arrangement is by controlling the spacing between the first / second lenslets, whilst keeping the curvature of the first lenslets the same.

[0074] Another approach for modifying or controlling the beam spreading properties is to control the curvature of the lenslets and keep the spacing between the first / second lenslets the same. A simple way to decrease the radius is by increasing or stretching the height of the lenslets (stretching the spherical lenslets into ellipsoids).

[0075] In some examples, the minimum radius of curvature of each first and second lenslet is no less than 0.8 mm, preferably no less than 1 mm, e.g., no less than 2 mm. This advantageously increases the ease of producing the lens arrangement, e.g., by milling, 3D printing or the like.

[0076] The array of first lenslets may comprise no less than 100 lenslets, e.g., no fewer than 1000 lenslets.

[0077] Figure 4 illustrates an example of an existing lens arrangement 400. The existing lens arrangement comprises an array of lenslets 411, 412 that are interconnected with one another by fillets 421, 422. It will be apparent that, due to the close positioning of the array of lenslets, the interconnecting fillets 421, 422 necessarily have a significantly smaller radius of curvature than the lenslets 411, 412.

[0078] Figure 5 illustrates an example of a proposed lens arrangement 500. The lens arrangement comprises an array of first lenslets 511, 512 and an array of second lenslets 521, 522 (interspersed amongst the first lenslets). Spaces between the first and second lenslets are filled with respective saddle-shaped lenslets 531, 532.

[0079] As illustrated in Figure 5, the curvature of each first lenslet is similar to (e.g., within a predetermined percentage of) the curvature of neighboring second lenslets. This creates greater uniformity in local regions of the lens arrangement 500.

[0080] Figures 3 and 5 clearly demonstrate the difference between existing or known lens arrangements and the proposed concept. More particularly, they clearly demonstrate how (sudden) local changes in curvature are reduced or avoided through use of the proposed configuration.

[0081] Figure 6 illustrates an example of a proposed lens arrangement 600. The array of first lenslets (and thereby the array of second lenslets) are arranged in a phyllotaxis arrangement, forming a visible pattern in the lens arrangement 600. Of course, other patterns for the first and / or second lenslets are possible.

[0082] For the avoidance of doubt, it is noted that any proposed lens arrangement may be generally planar or curved in shape. Thus, the arrays of first and second lenslets may be formed on a planar or curved surface. This is advantageous as the proposed approach can be used to enhance or supplement the optical performance of an existing lens (e.g., defining the curved surface) or other optical element, such as a collimator.

[0083] There is also provided a lighting device comprising a light emitting element configured to emit light; and any herein disclosed lens arrangement of configured to receive light emitted by the light emitting element.

[0084] Figure 7 illustrates an example of a lighting device 700 comprises a light emitting element 720 (e.g., an LED chip or an array of LEDs) and a lens arrangement 710, which may be embodied as previously described.

[0085] The illustrated light emitting element 720 takes the form of an LED chip, e.g., an array of one or more LEDs. However, alternative forms of light emitting element will be readily apparent to the skilled person, e.g., a halogen bulb or the like. The lighting device 700 may comprise a collimator 730 configured to collimate received light to produce a beam of light. The lens arrangement 710 may be a separate component to the collimator 730 (e.g., formed in a plate position on top of the collimator).

[0086] Alternatively, the lens arrangement may be integrally formed with the collimator. For instance, the collimator may take the form of an optical system (such as a collimating lens, a Fresnel lens, a TIR lens or a TIR collimator), and the lens arrangement may be formed in / on a light exit surface (i.e., an exit face) of the optical system. In some examples, the lens arrangement may be formed directly upon the collimator, e.g., 3D printed on top of the collimator. This allows for late stage (re)configuration of the shape of the beam output by the lighting device.

[0087] Proposed lens arrangements are easier to manufacture than existing lens arrangements. In particular, the precision required to generate proposed lens arrangements with desired beam spreading or shaping characteristics is significantly reduced, thereby increasing an ease of manufacturing the lens arrangement(s).

[0088] For instance, if the lens arrangement (or a mold for making a lens arrangement) is produced by a milling process, then a larger and / or less precise milling tool can be used compared to the manufacturing process for an existing or known lens arrangement. In particular, the larger the diameter of the milling tool, the greater surface speed and stability is achieved. Moreover, large diameter tools wear out less quickly than small diameter tools, thereby reducing the material cost and difficulty of manufacture.

[0089] Accordingly, there is proposed a method of manufacturing a lens arrangement for performing beam spreading, the method comprising milling a substrate to define a herein disclosed lens arrangement.

[0090] Thus, the method comprises milling a substrate to define a lens arrangement comprising: an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is within a predetermined percentage deviating from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet; wherein areas between the first and second lenslets are connected by saddle-shaped lenslets having a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle-shaped lenslet.

[0091] There is proposed a method of manufacturing a mold for a lens arrangement performing beam spreading, the method comprising milling a substrate to define a mold for a herein disclosed lens arrangement.

[0092] One advantage of the proposed approach is that a first lens arrangement produced by directly milling a substrate in a first pattern to create the lens arrangement will share similar or identical properties to a first lens arrangement produced using a mold produced by milling a substrate in the same first pattern (i.e., having a complementary / inverse / flipped shape to the mold). In particular, the roles of the array of first lenslets and array of second lenslets will simply flip. As they may share similar beam-spreading capabilities (due to the restriction on maximum magnitude of curvature), the first and second lens arrangements will function in a same / similar way.

[0093] As another example, if the lens arrangement is produced using a 3D printing effect, then the required accuracy and / or interlayer wait time can be reduced. More particularly, with smaller curvatures, the precision of the 3D printing process can be significantly reduced, and the effect of material flow after printing has a significantly reduced impact on the performance of the lens arrangement (e.g., as a percentage change will be significantly reduced).

[0094] Accordingly, there is herein proposed a method of manufacturing a lens arrangement for performing beam spreading, the method comprising 3D printing to define any herein disclosed lens arrangement.

[0095] Thus, the method comprises 3D printing to define a lens arrangement comprising an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is within a predetermined percentage deviating from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet; wherein areas between the first and second lenslets are connected by saddle-shaped lenslets having a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle-shaped lenslet. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0096] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0097] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A lens arrangement for performing beam spreading comprising: an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is deviating at the most by a predetermined percentage from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet; wherein areas between the first and second lenslets are connected by saddle- shaped lenslets having a first curvature in a first plane and a second, opposite curvature in a second plane perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle- shaped lenslet, wherein the predetermined percentage is less than 25%.

2. The lens arrangement of claim 1, wherein: a center of each first lenslet defines a center of a respective Voronoi cell of a Voronoi tessellation; and a center of each second lenslet is located at a vertex of one or more Voronoi cells defined by the centers of the first lenslets.

3. The lens arrangement of claim 1 or 2, wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is the same as the average of the maximum magnitudes of the curvature of all second lenslets neighboring said first lenslet.

4. The lens arrangement of claim 3, wherein a maximum magnitude of curvature of all first lenslets and all second lenslets is the same.

5. The lens arrangement of any of claims 1 to 4, wherein the footprint of the array of first lenslets upon a lens plane in which the lens arrangement lies is less than the combined footprint of the array of second lenslets and the saddle-shaped lenslets upon the lens plane.

6. The lens arrangement of claim 5, wherein the footprint of the array of first lenslets upon a lens plane in which the lens arrangement lies is the same as footprint of the array of second lenslets upon the lens plane.

7. The lens arrangement of any of claims 1 to 6, wherein the array of first lenslets are arranged in a non-rectangular and non-linear tessellation pattern.

8. The lens arrangement of claim 7, wherein the array of first lenslets are arranged in a hexagonal or phyllotaxis tessellation pattern.

9. The lens arrangement of any of claims 1 to 8, wherein a minimum radius of curvature of each first and second lenslet is no less than 1 mm.

10. The lens arrangement of any of claims 1 to 9, wherein the array of lenslets comprises no less than 100 lenslets.

11. A lighting device comprising: a light emitting element configured to emit light; and the lens arrangement of any of claims 1 to 10 configured to receive light emitted by the light emitting element.

12. A method of manufacturing a lens arrangement for performing beam spreading, the method comprising milling a substrate to define a lens arrangement comprising: an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is deviating at the most by a predetermined percentage from the average maximummagnitude of the curvature of any second lenslet neighboring said first lenslet, wherein the predetermined percentage is less than 25%; wherein areas between the first and second lenslets are connected by saddle- shaped lenslets having a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle- shaped lenslet.

13. A method of manufacturing a lens arrangement for performing beam spreading, the method comprising 3D printing to define a lens arrangement comprising: an array of first lenslets having a curvature of a same, first sign; and an array of second lenslets having a curvature of a same, second sign, wherein the second sign is opposite to the first sign, wherein the array of first lenslets is interspersed with the second lenslets; wherein, for each first lenslet, a maximum magnitude of the curvature of said first lenslet is deviating at the most by a predetermined percentage from the average maximum magnitude of the curvature of any second lenslet neighboring said first lenslet wherein the predetermined percentage is less than 25%; wherein areas between the first and second lenslets are connected by saddle- shaped lenslets having a first curvature in a first direction and a second, opposite curvature in a second direction perpendicular to the first direction, wherein, for each saddle-shaped lenslet, the maximum magnitude of the first curvature and the maximum magnitude of the second curvature is no greater than the curvature of any first or second lenslet neighboring said saddle- shaped lenslet.

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