LED Filament Lamps

Abstract

An object of the present invention is to provide an improved LED filament lamp (10), the LED filament lamp (10) comprising a transparent capsule (11) provided with a transparent optical structure (12); at least one LED filament (14) enclosed by the transparent capsule (11); wherein the transparent optical structure (12) comprises a plurality of individually separated prismatic grooves (17) and / or ridges, the plurality of individually separated prismatic grooves (17) and / or ridges being at least partially aligned along a projection of the at least one LED filament (14) on the transparent capsule (11); wherein each of the plurality of individually separated prismatic grooves (17) and / or ridges comprises a refractive facet (171), the refractive facet (171) being oriented at a position of the corresponding prismatic groove (17) and / or ridge at a wedge angle (172) between 5 and 50 degrees with respect to a tangent line of the capsule (11).

Description

Technical Field

[0001] The present invention relates to an LED (light emitting diode) filament lamp, wherein the LED filament lamp comprises a transparent capsule provided with a transparent optical structure comprising a refractive optical element. The present invention also relates to a luminaire comprising a socket and such an LED filament lamp. The present invention also relates to a method for providing a transparent optical structure to a transparent capsule of such an LED filament lamp. Background Art

[0002] Incandescent lamps are increasingly being replaced by LED-based lighting solutions. However, many users still prefer the appearance of incandescent lamps, for example due to their highly decorative appearance, but at the same time still want to have the benefits provided by LED-based lamps and lighting. Therefore, it is possible to utilize the infrastructure for producing glass bulb-based incandescent lamps and use LED filaments to replace the (conventional) filaments; thus, an LED filament lamp is provided. The LED filament can thereby be connected to a module comprising electrical wiring and / or a power supply.

[0003] When one or more LED filaments are operated to emit light of relatively low intensity, such LED filament lamps are generally able to produce the desired effect of an incandescent-like appearance. However, due in part to the lower power consumption of LED-based lighting, the lumen output of each LED filament lamp tends to be higher. Therefore, due to the continued increase in the intensity of the light emitted by the one or more LED filaments, the glare produced by the light emitted by the LED filament lamp to the observer may be uncomfortable. This is a significant drawback.

[0004] To reduce this glare, the (bulb) envelope of the LED filament lamp can be frosted or textured so that the filament is hidden from direct viewing. While this solves the glare problem, it also takes away the decorative look of the clear filament bulb, thus eliminating the transparency and unique characteristics of the LED filament lamp. Summary of the invention

[0005] The object of the present invention is to provide an improved LED filament lamp, which at least alleviates the problems and drawbacks mentioned above. In addition, the present invention provides an LED filament lamp, comprising a transparent capsule, the transparent capsule being provided with a transparent optical structure; at least one LED filament, the at least one LED filament being enclosed by the transparent capsule; wherein the transparent optical structure comprises a plurality of individually separated prismatic grooves and / or ridges, the plurality of individually separated prismatic grooves and / or ridges being at least partially aligned along a projection of the at least one LED filament on the transparent capsule; wherein each of the plurality of individually separated prismatic grooves and / or ridges comprises a refractive facet, the refractive facet being oriented at a wedge angle of between 5 and 50 degrees to a tangent of the capsule at the location of the respective prismatic groove and / or ridge.

[0006] The LED filament lamp comprises a transparent enclosure provided with a transparent optical structure. The at least one LED filament is arranged in the transparent enclosure. Therefore, the at least one LED filament is visible in the enclosure and presents a characteristic appearance of an incandescent lamp while providing the technical advantages of an LED lamp.

[0007] Moreover, the transparent optical structure comprises a plurality of prismatic grooves and / or ridges. The plurality of grooves and / or ridges are individually spaced and at least partially aligned along a projection of at least one LED filament on the transparent capsule. Additionally, each prismatic groove and / or ridge comprises a refractive facet (or plane). The refractive facet is oriented at a wedge angle of between 5 and 50 degrees to a tangent to the capsule at the location of the corresponding prismatic groove and / or ridge. Thus, the prismatic grooves and / or ridges are refractive. Thus, due to the combination of these features, the plurality of individually spaced prismatic grooves and / or ridges provide a refractive optical effect of light emitted from at least one LED, rather than providing an effect based on, for example, total internal reflection (TIR).

[0008] More specifically, a plurality of prismatic grooves and / or ridges provided to the transparent capsule deflect a portion of light emitted from at least one LED filament to produce one or more shifted virtual images of the at least one LED filament. Considering a relative prism area of ​​'P' and a luminance of the LED filament of 'L', the transparent capsule provided with the transparent optical structure according to the present invention will present a luminance of (1-P)*L to the at least one LED filament arranged in the transparent capsule, and a luminance of P*L to the virtual image of the at least one LED filament. Thus, by redistributing the luminance of the at least one LED filament over a larger surface area, the perceived brightness and glare of the LED filament lamp is advantageously reduced without reducing the light output of the LED filament lamp.

[0009] According to the invention, the individually separated prismatic grooves and / or ridges may be symmetrical or asymmetrical. Thus, asymmetrical and individually separated prismatic grooves and / or ridges may present only one virtual image, while symmetrical and individually separated prismatic grooves and / or ridges may present two virtual images. In both cases, the refractive facets may be oriented at the location of the corresponding prismatic grooves and / or ridges in a wedge angle of between 5 and 50 degrees to the tangent of the capsule, thereby ensuring the refraction of the light.

[0010] The spaces between the plurality of prismatic grooves and / or ridges may be flat, thus only slightly shifting the image of the LED filament, so as not to be considered as presenting a shifted virtual image according to the present invention. Moreover, the absence of spaces between the plurality of prismatic grooves and / or ridges would present a completely diffuse optic, thereby eliminating the unique characteristic appearance of an LED filament lamp and becoming merely a diffuse LED lamp in which individual filaments cannot be identified.

[0011] In various aspects, the transparent enclosure may be at least partially transparent. For example, the top and / or neck of the enclosure of the LED filament lamp may be, for example, translucent.

[0012] In one embodiment, the wedge angle may be between 10 and 40 degrees, preferably between 20 and 30 degrees. Such wedge angles between 10 and 40 degrees or between 20 and 30 degrees may be preferred because a plurality of individually spaced prismatic grooves and / or ridges may enhance the induced refractive optical effect.

[0013] In one embodiment, at least two of the plurality of individually spaced prismatic grooves and / or ridges may include different wedge angles.Such an embodiment may be advantageous for providing more variety in virtual images presented by the transparent optical structure.

[0014] Furthermore, in one embodiment, the transparent optical structure may cover less than half of the transparent envelope, (preferably) less than one-third of the transparent envelope, or (more preferably) less than one-tenth of the transparent envelope. Because less than half of the transparent envelope is covered by the transparent optical structure, when viewing the LED filament lamp, looking directly at at least one LED filament will preserve the dominant image. However, to a more advantageous degree, the same applies to examples in which less than one-third or less than one-tenth of the transparent envelope is covered by the transparent optical structure.

[0015] The embodiment can also be expressed as: the transparent optical structure covers less than half of the entire surface area of ​​the transparent capsule, (preferably) less than one-third of the entire surface area of ​​the transparent capsule, or (more preferably) less than one-tenth of the entire surface area of ​​the transparent capsule. The embodiment can also be expressed as: the total surface area of ​​the transparent capsule can be partially covered by the transparent optical device, and the portion is less than half of the total surface area of ​​the transparent capsule, less than one-third of the total surface area of ​​the transparent capsule, or less than one-tenth of the total surface area of ​​the transparent capsule.

[0016] The individual spacing of the prismatic grooves and / or ridges may be consistent. Thus, in one embodiment, a plurality of prismatic grooves and / or ridges may be individually spaced at a fixed pitch; wherein the fixed pitch may be defined as the shortest distance along the capsule between adjacent tops of the plurality of individually spaced prismatic grooves and / or ridges.

[0017] In one embodiment, the base width of each prismatic groove and / or ridge of the plurality of individually spaced prismatic grooves and / or ridges may be between 0.01 mm and 0.9 mm, preferably between 0.05 mm and 0.5 mm. The base width may be expressed as the base width of the prism. Such a width between 0.01 mm and 0.9 mm, and preferably between 0.05 mm and 0.5 mm, may be typical for presenting a refractive optical effect, for example, according to the present invention. In another embodiment, at least two prismatic grooves and / or ridges of the plurality of individually spaced prismatic grooves and / or ridges may include different base widths. Such an embodiment may even reduce the perception of glare, since the plurality of individually spaced prismatic grooves and / or ridges may present a plurality of virtual images corresponding to the respective at least one LED filament.

[0018] In one embodiment, each of the plurality of individually spaced prismatic grooves and / or ridges may include the same base width. Thus, the prismatic grooves and / or ridges may include the same shape. This may, for example, facilitate the manufacture of LED filament lamps.

[0019] Moreover, in another embodiment, the plurality of prismatic grooves and / or ridges may be individually spaced apart by a fixed pitch equal to one of: at least twice the same base width, at least three times the same base width, at least four times the same base width, at least five times the same base width, or at least ten times the same base width; wherein the fixed pitch may be defined as the shortest distance along the capsule between adjacent tops of the plurality of individually spaced prismatic grooves and / or ridges.

[0020] In one embodiment, a plurality of individually spaced apart prismatic grooves and / or ridges are evenly distributed along the perimeter of the transparent envelope. Such an embodiment is advantageous in producing a uniform light output and / or appearance of the LED filament lamp.

[0021] In one embodiment, the transparent capsule may include an inner capsule surface and an outer capsule surface, wherein the transparent optical structure may be disposed on the inner capsule surface, on the outer capsule surface, and / or between the inner capsule surface and the outer capsule surface. The inner capsule surface may be a surface of the transparent capsule facing inwardly toward the at least one LED filament. The outer capsule surface may be a surface of the transparent capsule facing outwardly away from the at least one LED filament.

[0022] The transparent optical structure may be provided on the inner surface of the transparent capsule; thus, the inner surface may be provided with a plurality of individually spaced prismatic grooves and / or ridges, which are aligned along the projection of at least one LED filament onto the corresponding inner surface of the transparent capsule. Such an embodiment may provide advantages when manufacturing the LED filament lamp and / or allow the outer surface of the transparent capsule to remain smooth.

[0023] Additionally or alternatively, the transparent optical structure may be provided on the outer surface of the transparent capsule; thus, the outer surface may be provided with a plurality of individually spaced prismatic grooves and / or ridges, the plurality of individually spaced prismatic grooves and / or ridges being aligned along the projection of at least one LED filament onto the respective outer surface of the transparent capsule. Such an embodiment may provide advantages when manufacturing the LED filament lamp, for example, first, the transparent capsule may be manufactured; subsequently, the transparent optical structure may be associated with the outer surface of the transparent capsule.

[0024] Additionally or alternatively, the transparent optical structure may be provided in the transparent enclosure, i.e. between the inner enclosure surface and the outer enclosure surface; thus, a plurality of individually separated prismatic grooves and / or ridges may be provided as an integral part of the transparent enclosure, the plurality of individually separated prismatic grooves and / or ridges being aligned along a projection of at least one LED filament onto the transparent enclosure. Such an embodiment may provide advantages when manufacturing the LED filament lamp, e.g. the transparent enclosure and the transparent optical structure may be made, e.g. from a single material, e.g. by a single process. Techniques such as 3D printing or photolithography or 2K injection molding may be applied.

[0025] Thus, although the outer surface of the transparent envelope is generally easier to construct, the transparent optical structure can be provided on the inner or outer surface of the transparent envelope, depending on, for example, the materials and / or the production technology. It can be made by the structure in the mold of the plastic or glass bulb; made as a post-processed structure; or made by coating (e.g., embossing or etching or photolithography); or made as a separate sleeve (e.g., a sleeve made of silicone) or a rigid cylinder that can be pulled over the lamp as an attachment.

[0026] As mentioned above, the dimensions may also depend, for example, on the material of the transparent optical structure and the corresponding plurality of individually spaced prismatic grooves and / or ridges. Thus, in one embodiment, the transparent optical structure may include an optical structure material, wherein the optical structure material may be one of the following: glass, plastic, silicone, resin, or ceramic.

[0027] Likewise, the material of the transparent capsule can also be limited. Therefore, in one embodiment, the transparent capsule comprises a capsule material, wherein the capsule material can be one of the following: glass, plastics, silicone, resin, or ceramic. The plastic can, for example, be poly(methyl methacrylate), also referred to as PMMA. Other similar transparent materials can also be envisioned as optical structure materials and / or capsule materials. Some examples can be provided, wherein the optical structure material and the capsule material can be identical, or at least comprise identical crystalline structures. Therefore, in one embodiment, the transparent optical structure can be integrated with the transparent capsule. This embodiment is advantageous when manufacturing the transparent capsule provided with the transparent optical structure according to the present invention.

[0028] In one embodiment, the luminance of each of the at least one LED filament may be at least 100 kcd / m 2 Because the brightness of the at least one LED filament is high, a relatively low prism area 'P' is sufficient to reduce glare, since the at least one LED filament has a brightness of 100 kcd / m 2 A virtual image of 10% or even 1% of such brightness value can still be perceived as a bright source (thereby distributing part of the light emitted from one LED filament to the virtual image, thus reducing the perception of glare). An additional benefit of being able to achieve a relatively low prism area 'P' is that when the LED filament lamp is operationally in an off state, the virtual image of at least one LED filament becomes substantially invisible, which makes the appearance of the LED filament lamp according to the present invention substantially the same as other filament light bulbs (such as conventional light bulbs) in an off state.

[0029] In one embodiment, the LED filament lamp may comprise an axis of symmetry, wherein at least one LED filament extends longitudinally along said axis of symmetry. Such an axis of symmetry may be a centerline of the LED filament lamp, such as an LED light bulb. Moreover, in one embodiment, at least one LED filament may be substantially parallel to said axis of symmetry. Such an embodiment ensures that the transparent optical structure itself is also not visible. Substantially parallel may mean that at least one LED filament may be tilted with respect to the axis of symmetry at a pitch of less than 1 mm, or alternatively may have an angle of less than 5 degrees with respect to said axis of symmetry.

[0030] The transparent envelope may include a bulb shape, a cylindrical shape, an at least partially spherical shape, a tubular shape, a rectangular shape, and / or any other shape that is common, in particular, for lamps or bulbs.

[0031] In various aspects, the transparent optical structure can be provided to a surface area of ​​the transparent capsule that is oriented toward the viewing direction of the LED filament lamp (towards the user). For example, considering a classic light bulb (shape), the transparent optical structure can be provided to a spherical surface area of ​​the bulb capsule, while the transparent optical structure is not applied to the bottom neck of the bulb capsule (which is incorporated into the fitting of the bulb).

[0032] Another object of the present invention is to provide an improved luminaire (or lighting system) according to the present invention, which at least alleviates the problems and drawbacks mentioned above. In addition, the present invention also provides a luminaire comprising a socket and an LED filament lamp according to any one of the preceding claims, wherein the LED filament lamp is mounted in the socket. Therefore, the advantages and / or embodiments applied to the LED filament lamp according to the present invention can be applied to the luminaire according to the present invention mutatis mutandis.

[0033] Another object of the present invention is to provide an improved method for providing a transparent envelope of an LED filament lamp with a transparent optical structure, which at least alleviates the problems and disadvantages mentioned above. In addition, the present invention provides a method for providing a transparent envelope of an LED filament lamp with a transparent optical structure, the LED filament lamp comprising at least one LED filament enclosed by the transparent envelope, wherein the method comprises: coating the outer surface and / or inner surface of the transparent envelope with a plurality of individually separated prismatic grooves and / or ridges by means of embossing, etching or photolithography, the plurality of individually separated prismatic grooves and / or ridges being at least partially aligned along the projection of the at least one LED filament on the transparent envelope; wherein each of the plurality of individually separated prismatic grooves and / or ridges comprises a refractive facet, which is oriented in a manner that forms a wedge angle of between 5 and 50 degrees with a tangent to the envelope at the location of the respective prismatic groove and / or ridge. Therefore, the advantages and / or embodiments applicable to the LED filament lamp according to the present invention can be applied mutatis mutandis to the method according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention will now be further illustrated by means of the accompanying schematic and non-limiting drawings,

[0035] Figure 1A and Figure 1B Schematically depicts an LED filament lamp known in the prior art;

[0036] Figure 2A , Figure 2B and Figure 2C An embodiment of an LED filament lamp according to the present invention is schematically depicted, wherein Figure 2C A cross-sectional view of a transparent capsule provided with a transparent optical structure of the LED filament lamp corresponding to the embodiment is depicted;

[0037] Figure 3A and Figure 3B schematically depicting a number of alternative embodiments of a transparent enclosure provided with a transparent optical cover according to the invention;

[0038] Figure 4 An embodiment of the method according to the invention is schematically depicted. DETAILED DESCRIPTION

[0039] The present invention is now described hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the present invention are illustrated. However, the present invention may be implemented in many different forms and should not be construed as being limited to the embodiments of the present invention set forth herein; rather, these embodiments of the present invention are provided by way of example so that the disclosure will convey the scope of the present invention to those skilled in the art. In the accompanying drawings, unless otherwise specifically stated, the same reference numerals represent the same or similar components having the same or similar functions.

[0040] As mentioned above, incandescent lamps are increasingly being replaced by LED filament lamps because they resemble the appearance of incandescent lamps but provide the benefits associated with LED lighting. However, due to the ongoing trend to increase the light output of the LED filaments installed within such LED filament lamps, LED filament lamps may produce an uncomfortable glare to the observer. Reducing this glare is often achieved by frosting or texturing the enclosure of the LED filament lamp in order to hide the filament from direct viewing, but this solution eliminates the unique feature of LED filament lamps having a transparent enclosure and a clearly visible LED filament.

[0041] Figure 1A and Figure 1B Schematically depicted is an LED filament lamp 800 known in the prior art. The known LED filament lamp 800 comprises a fitting 801, a transparent capsule 802 made of glass, a stem 803 holding a first LED filament 804 and a second LED filament 805. The two LED filaments 804, 805 are visible through the transparent capsule. Although not shown, the first LED filament 804 and the second LED filament 805 are operably connected to a module including electrical wiring and / or a power supply. Mechanical structures for holding and / or mounting the LED filaments are not explicitly depicted, but are known in the art.

[0042] refer to Figure 1A , it is known that the LED filament lamp 800 is in a disconnected state. Figure 1B , it is known that the LED filament lamp 800 is in the on state, wherein the LED filaments 804, 805 emit light. The filament luminance of each LED filament 804, 805 is, for example, 100 kdc / m 2 Due to the high lumen output of the filament, the known LED filament lamp 800 causes glare when looking directly into the transparent envelope 802, which is known to be very uncomfortable and is a technical disadvantage of such LED filament lamps 800 known in the art.

[0043] Figure 2A and Figure 2B An embodiment of an LED filament lamp 10 according to the present invention is schematically depicted. Figure 2A, the LED filament lamp 10 is in the disconnected state. Figure 2B , the LED filament lamp 10 is in the on state (and therefore emits light).

[0044] The LED filament lamp 10 includes a transparent capsule 11. The transparent capsule 11 is made of a glass capsule material. In the transparent capsule 11, the LED filament lamp 10 includes a stem 19 that holds a first LED filament 13 and a second LED filament 14. The first LED filament 13 and the second LED filament 14 extend longitudinally along a symmetry axis 18 of the LED filament lamp 10, wherein the first LED filament 13 and the second LED filament 14 gradually taper inwardly toward the top of the transparent capsule 11. Herein, the luminance of each of the first LED filament 13 and the second LED filament 14 is 100 kcd / m 2 .

[0045] Alternatively, the transparent envelope may be made of another transparent material, such as a plastic, such as PMMA. Alternatively, the stem may be any other mechanical structure known in the art for holding an LED filament. Alternatively, the LED filament lamp may include any other number of LED filaments, such as, for example, one, three or four. Further, alternatively, at least one LED filament may be substantially parallel to the axis of symmetry. Yet alternatively, at least one LED filament may be perpendicular to the axis of symmetry. Alternatively, at least one LED filament may spiral or swirl around the axis of symmetry.

[0046] Figure 2C Depicted Figure 2A and Figure 2B A cross-sectional view 81 of the transparent capsule 11 of the depicted embodiment. Figure 2A , Figure 2B , especially reference Figure 2C The transparent capsule 11 includes an inner capsule surface 15 and an outer capsule surface 16 , wherein the transparent capsule 11 also includes (or is provided with) a transparent optical structure 12 .

[0047] Herein, the transparent optical structure 12 is provided on the outer envelope surface 15. The transparent optical structure 12 includes a plurality of individually separated prismatic grooves 17. For example, the plurality of individually separated prismatic grooves 17 can be manufactured on the outer envelope surface 15 via photolithography. Therefore, the plurality of prismatic grooves 17 are individually separated, and further, along the first LED filament 13 and the second LED filament 14, the projections on the transparent envelope 11 (particularly the outer envelope surface 15) are aligned. Therefore, schematically considering the present disclosure Figure 2A and Figure 2B In the two-dimensional (front) observation plane, the transparent optical structure 12 is aligned along the same contour as the first LED filament 13 and the second LED filament 14. Figure 2CDepicted are six such prismatic grooves 17. Due to their alignment and limited number, the transparent optical structure 12 covers less than one tenth of the transparent envelope 11.

[0048] Alternatively, the prismatic grooves may be individually separated prismatic ridges, or a combination of individually separated prismatic grooves and prismatic ridges. Moreover, in alternative embodiments, the transparent optical structure may cover less than half of the transparent capsule. Alternatively, in some embodiments, the individually separated prismatic grooves may be evenly distributed along the perimeter of the transparent capsule.

[0049] Still reference Figure 2C , the prismatic grooves 17 each constitute an asymmetric prismatic groove (i.e., having one inclined facet (i.e., called a refractive facet) and one vertical facet perpendicular to the outer envelope surface 15). Therefore, each prismatic groove 17 comprises a refractive facet 171. The refractive facet 171 is oriented at a wedge angle 172 of 30 degrees to a tangent 173 to the envelope at the location of the corresponding prismatic groove. The prismatic grooves 17 are thus refractive. Alternatively, at the location of the corresponding prismatic grooves and / or ridges, the wedge angle to the tangent to the envelope may be between 5 and 50 degrees.

[0050] Therefore, each asymmetric and individually separated prismatic groove 17 will present only one shifted virtual image of the corresponding LED filament. Therefore, due to the individually separated refractive prismatic grooves 17, the transparent optical structure 12 refracts (or deflects) the light emitted from the first LED filament 13 and the second LED filament 14 within the transparent envelope 11 and produces the shifted first virtual image 23 and the second virtual image 24 of the corresponding first LED filament 13 and the second LED filament 14, respectively (when viewed). Figure 2C is in the connected state.

[0051] The brightness of the respective virtual images 23, 24 is proportional to the relative surface areas of the respective facets of the prismatic groove 17. For example, when the distance of the LED filament to the prismatic groove is ten times the size of the refractive facets of the prismatic groove 17, the corresponding shifted virtual image of the LED filament is approximately one tenth the brightness of the original (image) LED filament.

[0052] Therefore, still refer to Figure 2A, the LED filament lamp 10 is in an off-state. The first LED filament 13 and the second LED filament 14 are clearly visible through the transparent enclosure 11 provided with the transparent optical structure 12. Moreover, as mentioned, the transparent optical structure 12 generates a shifted first virtual image 23 of the first LED filament 13 and a second virtual image 24 of the second LED filament 14. However, in the off-state of the LED filament lamp 10, the virtual images 23, 24 of the respective two LED filaments 13, 14 are faint and dominated by the standard image (i.e., the brightness of the LED filament in the off-state is, for example, less than the background, so its virtual image is basically invisible in the off-state). Therefore, when observed in the off-state, the LED filament lamp 10 has the (essentially) same appearance as an LED filament lamp without a transparent optical structure (i.e., for example, Figure 1A Thus, the transparent optical structure 12 does not substantially obscure the appearance of the LED filaments 13, 14 in the transparent envelope 11.

[0053] However, when observed in the switched-on state, the two additional LED filaments 23, 24 become visible, slightly displaced relative to the original LED filaments 13, 14, because a first virtual image 23 and a second virtual image 24 of the two corresponding LED filaments 13, 14 of the LED filament lamp appear due to refraction caused by the transparent optical structure 12 including the plurality of asymmetric and individually spaced prismatic recesses 17. Although the brightness of the virtual images 23, 24 is less than the corresponding first LED filament 13 and second LED filament 14 (e.g., only one tenth of the brightness of the original LED filament considering the example given above), since the luminance of each of the first LED filament 13 and second LED filament 14 is initially 100 kcd / m 2 (Thus, considering the above example, the luminance of each virtual image is 10kcd / m 2 ), so the virtual images 23, 24 of the first LED filament 13 and the second LED filament 14 will still become bright and visible in the switched-on state. Therefore, the present invention is particularly advantageous for LED filament lamps with increasing lumen output, for example.

[0054] In summary, the present invention provides an LED filament lamp 10, wherein the transparent optical structure 12 enables virtual images 23, 24 of the LED filaments 13, 14 to appear due to refraction, thereby distributing the brightness of the LED filaments 13, 14 on these virtual images 23, 24 and advantageously reducing glare while still maintaining the characteristic appearance of a clear (transparent) LED filament bulb.

[0055] Figure 3A and Figure 3B Some alternative embodiments of LED filament lamps 30 , 50 according to the present invention are schematically depicted. FIG. 3A to FIG. 3B Also depicted is a corresponding transparent capsule 31 , 51 provided with a corresponding transparent optical structure 32, 52 according to the invention.

[0056] Figure 3A An embodiment of an LED filament lamp 30 is described by way of non-limiting example. FIG. 2A to FIG. 2C The embodiments described are partially similar, so the effects of the present invention and FIG. 2A to FIG. 2C The advantages of the described embodiments apply mutatis mutandis to Figure 3A The depicted embodiment.

[0057] refer to Figure 3A , the LED filament lamp 30 includes a transparent capsule 31. Four LED filaments 38 are arranged in the transparent capsule 31. The transparent capsule 31 is provided with a transparent optical structure 32. The transparent optical structure 32 includes a plurality of individually spaced and symmetrical prismatic grooves 37, which are aligned along the projection portions of the LED filaments 38 on the transparent capsule 31. Alternatively, the grooves may be ridges. More specifically, only the top portion of the transparent capsule 31 is provided with the transparent optical structure 32, thereby covering less than half of the transparent capsule 31 and advantageously presenting a clear view of the LED filament lamp 30.

[0058] Still reference Figure 3A Each prismatic groove 37 includes a refractive facet, and due to the symmetry in this context, each prismatic groove 37 has two refractive facets. The refractive facets are oriented in a manner that forms a wedge angle of 50 degrees with the tangent of the capsule at the location of the corresponding prismatic groove. Therefore, the prismatic groove is refractive.

[0059] Alternatively, the wedge angle may be different for different grooves in a plurality of individually spaced and symmetrical prismatic grooves. The transparent optical structure 32 is provided on the inner shell surface 35 of the transparent shell 31, and may also be provided in the transparent shell, i.e., between the inner shell surface and the outer shell surface. When the transparent shell is manufactured using 3D printing technology or alternatively via 2K injection molding, such a structure may be 3D printed, for example. Herein, a plurality of individually spaced and symmetrical prismatic grooves 37 are evenly distributed along the perimeter of the transparent shell 31.

[0060] Figure 3B An embodiment of an LED filament lamp 60 is described by way of non-limiting example. The LED filament lamp 60 is FIG. 2A to FIG. 2C The embodiments described are partially similar, so the effects of the present invention and FIG. 2A to FIG. 2C The advantages of the described embodiments apply mutatis mutandis to Figure 3B The depicted embodiment.

[0061] refer to Figure 3B , the LED filament lamp 60 includes a cylindrical transparent capsule 61. The LED filament lamp 60 includes a single LED filament 68 in the cylindrical transparent capsule 61. The single LED filament 68 extends in the longitudinal direction of the cylindrical transparent capsule 61 of the LED filament lamp 60, but swirls around the symmetry axis 69 of the LED filament lamp 60 (i.e., the center line 69 of the cylindrical capsule 61). The transparent capsule 61 is provided with a transparent optical structure 62 according to the present invention.

[0062] The transparent optical structure 62 includes a plurality of individually separated prismatic grooves 67, which are aligned along the projection portion of the LED filament 68 on the transparent envelope 61. The individually separated prismatic grooves 67 are provided between the inner envelope surface and the outer envelope surface of the transparent envelope 61. Herein, only a specific portion of the transparent envelope 61 (matching at least a portion of the projection) is provided with the transparent optical structure 62, thereby covering less than one-tenth of the transparent envelope 61 and advantageously presenting a clear view of the LED filament lamp 60.

[0063] In an embodiment not depicted, the present invention provides a lighting device including a socket, wherein FIG. 2, Figure 3A or Figure 3B The depicted LED filament lamp is mounted to the socket. The luminaire thereby powers and controls the LED filament lamp. Such a socket may, for example, include a cable to mount the socket to a ceiling, thereby realizing a suspended LED filament lamp.

[0064] Figure 4 A method 800 of providing a transparent envelope of an LED filament lamp with a transparent optical structure according to the present invention is schematically depicted by way of non-limiting example. The method comprises the following steps 801: coating the inner surface of the transparent envelope with a plurality of individually spaced prismatic grooves by means of photolithography, the plurality of individually spaced prismatic grooves being at least partially aligned along a projection of at least one LED filament on the transparent envelope; wherein each of the plurality of individually spaced prismatic grooves comprises a refractive facet oriented at a wedge angle of between 5 and 50 degrees to a tangent to the envelope at the location of the respective prismatic groove and / or ridge.

[0065] Alternatively or additionally, the individually separated prismatic grooves may also include individually separated prismatic ridges. Alternatively, the inner surface may be the outer surface, or the region between the inner and outer surfaces of the transparent capsule. Alternatively, the photolithography may be replaced by etching and / or embossing (such as 3D printing or injection molding).

Claims

1. An LED filament lamp, comprising: - A transparent enclosure provided with a transparent optical structure; - at least one LED filament, enclosed by the transparent capsule; wherein the transparent optical structure comprises a plurality of individually spaced prismatic grooves and / or ridges, the plurality of individually spaced prismatic grooves and / or ridges being at least partially aligned along a projection of the at least one LED filament onto the transparent envelope; wherein each of the plurality of individually spaced prismatic grooves and / or ridges comprises a refractive facet oriented at a wedge angle of between 5 and 50 degrees to a tangent to the capsule at the location of the respective prismatic groove and / or ridge, The transparent envelope comprises an outer envelope surface, wherein the transparent optical structure is arranged on the outer envelope surface. 2 . The LED filament lamp according to claim 1 , wherein the wedge angle is between 10 degrees and 40 degrees.

3. The LED filament lamp according to any one of the preceding claims, wherein at least two of the plurality of individually spaced prismatic grooves and / or ridges comprise different wedge angles.

4. The LED filament lamp according to any one of the preceding claims, wherein the transparent optical structure covers less than half of the transparent envelope, less than one third of the transparent envelope, or less than one tenth of the transparent envelope.

5. The LED filament lamp according to any one of the preceding claims, wherein the plurality of individually spaced prismatic grooves and / or ridges are individually spaced at a fixed pitch; Wherein the fixed pitch is defined as the shortest distance along the capsule between adjacent tops of the plurality of individually spaced prismatic grooves and / or ridges.

6. The LED filament lamp of any one of the preceding claims, wherein each of the plurality of individually spaced prismatic grooves and / or ridges comprises the same base width.

7. The LED filament lamp of claim 6, wherein the plurality of individually spaced prismatic grooves and / or ridges are individually spaced at a fixed pitch, the fixed pitch being equal to one of: at least two times the same base width, at least three times the same base width, at least four times the same base width, at least five times the same base width, or at least ten times the same base width; Wherein the fixed pitch is defined as the shortest distance along the capsule between adjacent tops of the plurality of individually spaced prismatic grooves and / or ridges.

8. The LED filament lamp according to any one of the preceding claims, wherein the plurality of individually spaced apart prismatic grooves and / or ridges are evenly distributed along the perimeter of the transparent envelope.

9. The LED filament lamp according to any one of the preceding claims, wherein the transparent optical structure comprises an optical structural material, wherein the optical structural material is one of the following: glass, plastic, silicone, resin or ceramic.

10. The LED filament lamp according to any one of the preceding claims, wherein the luminance of each of the at least one LED filament is at least 100 kcd / m 2 .

11. The LED filament lamp according to any one of the preceding claims, wherein the LED filament lamp comprises an axis of symmetry, wherein the at least one LED filament extends longitudinally along the axis of symmetry.

12. The LED filament lamp of claim 11, wherein the at least one LED filament is substantially parallel to the symmetry axis.

13. The LED filament lamp according to claim 2, wherein the wedge angle is between 20 degrees and 30 degrees.

14. A luminaire comprising a socket and an LED filament lamp according to any one of the preceding claims, wherein the LED filament lamp is mounted in the socket.

15. A method for providing a transparent optical structure to a transparent enclosure of an LED filament lamp, the LED filament lamp comprising at least one LED filament enclosed by the transparent enclosure, wherein the method comprises: - coating the outer surface of the transparent envelope with a plurality of individually spaced prismatic grooves and / or ridges by means of embossing, etching or photolithography, the plurality of individually spaced prismatic grooves and / or ridges being at least partially aligned along the projection of the at least one LED filament on the transparent envelope; Each of the plurality of individually spaced prismatic grooves and / or ridges comprises a refractive facet oriented at a wedge angle of between 5 and 50 degrees to a tangent to the capsule at the location of the corresponding prismatic groove and / or ridge.

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