A light emitting device

Abstract

A light emitting device (1) configured to, in operation, emit device light (2) and comprising an optical cavity (3), at least one LED filament (4) configured to, in operation, emit LED filament light (5), the at least one LED filament (4) being arranged in the optical cavity (3), and at least one beam shaping optical element (8), wherein the optical cavity (3) comprises a light exit window (6) and an inner surface (7), the inner surface (7) comprising a bottom surface (71) and a circumferential surface (72) extending between the light exit window (6) and the bottom surface (71), wherein at least a part of the inner surface (7) is specular reflective, and wherein the at least one LED filament (4) comprises a longitudinal axis (LF) and a transversal axis (TF), and the at least one LED filament (4) is arranged with the longitudinal axis (LF) extending at an angle, α, with a longitudinal axis (LO) of the at least one beam shaping optical element (8), wherein 0 degrees < α ≤ 90 degrees.

Description

[0001] 2025P80102EP01

[0002] 1

[0003] A light emitting device

[0004] FIELD OF THE INVENTION

[0005] The invention relates to a light emitting device configured to, in operation, emit device light, the light emitting device comprising an optical cavity, at least one LED filament configured to, in operation, emit LED filament light, the at least one LED filament being arranged in the optical cavity, and at least one beam shaping optical element.

[0006] BACKGROUND OF THE INVENTION

[0007] There is a continuous drive to improve the performance of LED based systems. A relatively new LED type is the LED filament which is frequently and exclusively used in LED lamps or bulbs. A LED filament is a long rod-shaped emitter (typical length 30-50 mm, diameter: 1-3 mm) which emits light over the whole surface area (comparable to a fluorescent tube). A LED filament may be composed of a linear array of blue LED dies on a lead frame (supported by a ceramic bar), covered with a layer of blue light converting material (“phosphor”). In a LED filament the LEDs are preferably arranged on an elongated carrier surface area. This specific “package-less” construction results in LEDs with a high efficacy of typically 250 Im / W. Up to now, LED filaments are exclusively applied in light bulbs. However, LED filaments can be applied in other lighting applications such as office lighting, creating several advantages compared to the more conventional small SMD LEDs based systems.

[0008] US 2012 / 120652 Al discloses an illumination source that is mounted so that its axis is in line with an edge (distal of a vertex) of a parabolic reflector. Some light will fall on the parabolic reflector in a region past the line from the focal point to the vertex. The light in region will be dim and have a small angular size because of the projected cross sectional area. However, this light will allow at least a portion of the second half of the parabola (that is, the half that is not illuminated) to contribute to the lighting distribution of the lamp.

[0009] The intensity profile is essential to optimize the illumination uniformity on the target plane, such as a floor, a table, or a wall. In the conventional approach, such as illustrated by the exemplary prior art light emitting device 1000 shown in Fig. 1, surface mounted device (SMD) LEDs 1003 are placed behind a diffuser and a beam shaping plate2025P80102EP01

[0010] 2

[0011] 1008 arranged at a light exit window 1006 of an optical cavity 1007 in which the LEDs 1003 are arranged. Such a configuration generates light 1002 with a typical droplet shaped intensity profile which allows almost no flexibility. An example of such an intensity profile is shown in Fig. 2.

[0012] CN 213 177755 U discloses a light emitting device comprising of an optical cavity, at least one LED filament and at least one beam shaping optical element.

[0013] US 2004 / 0223338 Al discloses a vehicle lamp for emitting light comprising a plurality of light sources and corresponding reflective surfaces to generate light beams having a certain light distribution pattern.

[0014] EP 1 471 304 A2 discloses a vehicle lamp comprising a plurality of light sources realized using LED arrays and reflecting surfaces forming a prescribed light distribution.

[0015] EP 1 298383 A2 discloses a vehicle light source comprising a replaceable lamp capsule having a support directly supporting one or more LED chips providing direct emission of light.

[0016] Also, if using LED filaments rather than LEDs, the properties of the optical cavity become essential in the final intensity profile of the beam because LED filaments radiate light in all directions. Therefore, there is a desire to provide a light emitting device with one or more of an improved illumination uniformity on the target plane and an improved intensity profile.

[0017] SUMMARY OF THE INVENTION

[0018] It is an object of the present invention to overcome this problem, and to provide a light emitting device with one or more of an improved illumination uniformity on the target plane and an improved intensity profile.

[0019] According to a first aspect of the invention, this and other objects are achieved by means of a light emitting device configured to, in operation, emit device light, the light emitting device comprising an optical cavity, at least one LED filament configured to, in operation, emit LED filament light, the at least one LED filament being arranged in the optical cavity, and at least one beam shaping optical element, wherein the optical cavity comprises a light exit window and an inner surface, the inner surface comprising a bottom surface and a circumferential surface extending between the light exit window and the bottom surface, wherein at least a part of the inner surface is specular reflective, and wherein the at least one LED filament comprises a longitudinal axis, LF, and a transversal axis, TF,2025P80102EP01

[0020] 3

[0021] and the at least one LED filament is arranged with the longitudinal axis, LF, extending at an angle, a, with a longitudinal axis, LO (and / or extending at an angle a with plane P in which the light exit window extends), of the at least one beam shaping optical element, wherein 2 degrees < a < 90 degrees, or 5 degrees < a < 90 degrees. In a LED filament the LEDs are preferably arranged on an elongated carrier surface area.

[0022] The inventors have surprisingly found that the orientation of the filaments is an important parameter to tune the intensity profile of the lighting module. Also, LED filaments can be applied directly behind a clear beam shaping plate (because of their relatively low brightness), and the orientation of the filaments have a strong relationship with the intensity profile of the final luminaire. Alternatively or additionally, the shape of the optical cavity can (also) be applied to tune said intensity profile.

[0023] Thereby, a light emitting device with one or more of an improved illumination uniformity on the target plane and an improved intensity profile is provided for. A LED filament typically is a light-emitting device that has a plurality of light emitting diodes (LEDs) arranged in a linear array. The LEDs may be arranged to emit light of different colors or spectral distributions. A LED filament has a length, a width, and an axis of elongation along the length. The length may be more than five times the width, such as more than ten times the width. A LED filament has a light-emitting surface that extends along the length, and preferably at least partly around the axis of elongation. The light-emitting surface is preferably arranged to homogenously emit light and / or to emit light omnidirectionally, i.e. in all directions / over 360 degrees around the axis of elongation. A LED filament may be arranged in a straight configuration or in a non-straight configuration, such as a curved configuration, a spiral or a helix. The LEDs of the LED filament are preferably arranged on an elongated carrier surface area, such as a surface area of a substrate that may be made from a polymer, glass, quartz, metal, or sapphire. The carrier may be rigid or flexible. When the carrier has a first major surface and an opposite second major surface, the LEDs are arranged on at least one of these surfaces. The carrier may be reflective or transmissive for light, such as translucent, or transparent. A LED filament may comprise an encapsulant that at least partly covers one or more of the LEDs and is configured to modify the light as emitted by the LEDs. The encapsulant may also at least partly cover one or more of the first and second major surfaces of the carrier. The encapsulant may comprise a polymer, which may be flexible, such as a silicone. The encapsulant may comprise a luminescent material, such as a phosphor, for modifying / converting the light, such as blue light, emitted by the LEDs, resulting in the light emitting device to emit white light. A LED filament may be used to2025P80102EP01

[0024] 4

[0025] mimic the filament of an incandescent light bulb. A LED filament may comprise multiple sub-filaments. Alternatively or additionally, the LED filament(s) may comprise a plurality of individually controllable red, green and blue LEDs (RGB LEDs) and alternatively or additionally the encapsulant may be a diffuser or comprise a diffusing or scattering material to modify / mix the light (beams) as emitted by the LEDs thus to render the light emitting device to (uniformly) emit white light and / or colored light.

[0026] The light emitting device may comprise a plurality of LED filaments arranged in the optical cavity, wherein each LED filament of the plurality of LED filaments is arranged with its longitudinal axis, LF, extending at an angle, a, with the longitudinal axis, LO, of the at least one beam shaping optical element (8), (and / or with the plane P) wherein 2 degrees < a < 90 degrees, or 5 degrees < a < 90 degrees, or 2 degrees < a < 90 degrees, or 5 degrees < a < 90 degrees.

[0027] It is noted that the angle alpha need not be the same for all LED filaments, or indeed for any two LED filaments. The multiple LED filaments may in other words have a wide variety of mutually different orientations in the optical cavity with respect to the longitudinal axis (LO) of the (at least one) optical element and / or with respect to the plane P in which the light exit window extends.

[0028] In other words, the light emitting device may comprise at least two LED filaments that are arranged at mutually different angles a with respect to the longitudinal axis (LO) (and / or with the plane P) of the beam shaping optical element arranged at the light exit window. Furthermore, to reduce or minimize the distortion of the omnidirectional light emission of each of the filaments and hence the uniformity of emission from the lighting device, each LED filament comprises two respective opposite end points lying on its respective longitudinal axis, LF, wherein the LED filaments are connected and mounted by their respective opposite end points to relatively thin, yet robust electrical conductors and kept in fixed position thereby. Thus, other mounting and / or support structures in the optical cavity that may negatively affect a uniform emission of the lighting device can be reduced.

[0029] At least 50% of the extent of the LED filament is unsupported. It may apply that at least 70% or at least 90% of the extent of the LED filament is unsupported and preferably the extent of the LED filament is completely unsupported.

[0030] Thereby, a light emitting device with one or more of a further improved illumination uniformity on the target plane and particularly a further improved intensity profile is provided for.2025P80102EP01

[0031] 5

[0032] It may apply that 20 degrees < a < 90 degrees, or 35 degrees < a < 90 degrees, or 45 degrees < a < 90 degrees, or 60 degrees < a < 90 degrees, or 75 degrees < a < 90 degrees, or 80 degrees < a < 90 degrees, or 85 degrees < a < 90 degrees, or a = 90 degrees.

[0033] Thereby, a light emitting device with particularly a further improved illumination uniformity on the target plane, and also a further improved intensity profile is provided for.

[0034] The at least one beam shaping optical element may be arranged at the light exit window.

[0035] Thereby, a light emitting device with which a wider variety of beam shapes may be obtained is provided for.

[0036] The beam shaping optical element may comprise a microlens optics (MLO) and a Gaussian diffuser film.

[0037] The MLO may for instance be a glare reducing plate or foil, a micro-prism plate or array, a microlens plate or array, or any combination thereof.

[0038] Thereby, a light emitting device with a simple structure is provided for.

[0039] The at least one LED filament may be arranged in a distance, d, from the bottom surface of the optical cavity.

[0040] This both influences the light distribution in a desirable manner and gives room for pivoting the at least one LED filament if it is arranged pivotably in the optical cavity.

[0041] The at least one LED filament, or each LED filament of the plurality of LED filaments, is arranged to be pivotable around an axis, A, extending perpendicular to the longitudinal axis, LF, and extending perpendicular to the transversal axis, TF.

[0042] Thereby, a light emitting device with which a wide variety of beam shapes may be obtained is provided for.

[0043] The at least one LED filament, or each LED filament of the plurality of LED filaments, is arranged to be pivotable around one of its end points, or around its center point.

[0044] Thereby, the light distribution of the device light may be influenced or optimized to a given application by pivoting the LED filament or filaments to a desired angle providing a desired light distribution. Thus, a versatile light emitting device is provided for.

[0045] At least 50 % of the inner surface may be specular reflective.

[0046] At least the bottom surface of the inner surface may be specular reflective. Thereby, light losses at the inner surface is reduced, and device light with an improved directionality may be obtained.2025P80102EP01

[0047] 6

[0048] At least a part of the inner surface comprises one or more of a specular reflective element, a semi-specular reflective element, a specular reflective material, a semi-specular reflective material, a specular reflective coating, or a semi-specular reflective coating.

[0049] Thereby, the light distribution of the device light may be influenced or optimized to a given application.

[0050] The circumferential surface may be any one of reflective, diffusive, and specular reflective.

[0051] Thereby, the light distribution of the device light may be influenced or optimized to a given application.

[0052] The at least one LED filament, or each LED filament of the plurality of LED filaments, may be arranged asymmetrically in the optical cavity.

[0053] Thereby, asymmetric beam shapes may be obtained, which as useful in many applications.

[0054] The at least one LED filament, or each LED filament of the plurality of LED filaments, may be arranged symmetrically in the optical cavity.

[0055] Thereby, symmetric beam shapes may be obtained, which as useful in many other applications.

[0056] The light emitting device may comprise two or more beam shaping optical elements arranged at the light exit window, the two or more beam shaping optical elements, optionally being separated by a transflective element, i.e. an optical element being in a range of 40% to 60%, such as for about 50%, transmissive for visible light and in a range of 40% to 60%, such as for about 50%, reflective for visible light. Alternatively or additionally, the two or more beam shaping elements may be optically split by a reflector that extends from the light exit window towards the bottom surface, thus dividing the optical cavity into two or more optical sub cavities. The reflector may extend from the light exit window substantially perpendicularly and / or onto the bottom surface. One or more LED filaments may be present at the border of the two or more optical sub cavities such that the LED filaments are shared by the optical sub cavities, or one or more LED filaments may be present in each optical sub cavity, such that each optical sub cavity has its own respective LED filament.

[0057] Thereby, a light emitting device with which an even wider variety of beam shapes may be obtained is provided for.

[0058] The two or more beam shaping optical elements may comprise a microlens optics (MLO) and a Gaussian diffuser film.2025P80102EP01

[0059] 7

[0060] The MLO may for instance be a glare reducing plate or foil, a micro-prism plate or array, a microlens plate or array, or any combination thereof. For example, at the exit surface a Gaussian diffuser is placed followed by the beam shaping plate (MLO). The Gaussian diffuser spreads the light according to a Gaussian distribution with a FWHM of 10 deg. The resulting beam shape is optimal for uniform illumination of a target area, space or object (e.g., a table). The improved illumination uniformity has the advantage that the spacing between luminaires can be increased (cost savings installation).

[0061] Thus, a light emitting device with a simple structure yet with ample beam shaping possibilities is provided for.

[0062] The circumferential surface may taper in a direction away from the bottom surface, such that the light exit window is larger than the bottom surface.

[0063] Thereby, the light distribution of the device light may be influenced or optimized to a given application.

[0064] The circumferential surface may extend perpendicular to the light exit window and the bottom surface.

[0065] Thereby, the light distribution of the device light may be influenced, particularly to obtain a well-defined batwing distribution.

[0066] The circumferential surface and the bottom surface may extend at an angle, P, with respect to one another, wherein 75 degrees < P < 120 degrees, or 90 degrees < P < 95 degrees, or 91 degrees < P < 95 degrees, or p = 90 degrees.

[0067] Thereby, the light distribution of the device light may be influenced or even optimized to provide a batwing distribution.

[0068] The invention further relates to a lamp comprising a light emitting device according to the invention.

[0069] The lamp may further comprise a light transmissive envelope at least partly enclosing the light emitting device and a base for electrically and mechanically connecting the LED filament lamp to a socket or a socket of a luminaire.

[0070] The invention still further relates to a luminaire, such as an essentially elongated box-shaped luminaire, comprising a lamp according to the invention.

[0071] The invention still further relates to a luminaire comprising a light emitting device according to the invention.

[0072] It is noted that the invention relates to all possible combinations of features recited in the claims.2025P80102EP01

[0073] 8

[0074] BRIEF DESCRIPTION OF THE DRAWINGS

[0075] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

[0076] Fig. 1 shows a cross-sectional side view of a prior art light emitting device. Fig. 2 shows an intensity profile of the device light emitted by the prior art light emitting device according to Fig. 1.

[0077] Fig. 3 shows a cross-sectional side view of a light emitting device according to the invention.

[0078] Fig. 4 shows an intensity profile of the device light emitted by the light emitting device according to Fig. 3.

[0079] Fig. 5 shows a cross-sectional side view of another light emitting device according to the invention.

[0080] Fig. 6 shows an intensity profile of the device light emitted by the light emitting device according to Fig. 5.

[0081] Fig. 7 shows a cross-sectional side view of another light emitting device according to the invention.

[0082] Fig. 8 shows an intensity profile of the device light emitted by the light emitting device according to Fig. 7.

[0083] Fig. 9 shows a perspective view of another light emitting device according to the invention.

[0084] Fig. 10 shows a cross-sectional side view of the light emitting device according to Fig. 9.

[0085] Fig. 11 shows a close-up view of the detail marked XI in Fig. 10.

[0086] Fig. 12 shows an intensity profile of the device light emitted by the light emitting device according to Figs. 9 and 10.

[0087] Fig. 13 shows a schematical side view of a lamp comprising a light emitting device according to the invention.

[0088] Fig. 14 shows a schematical side view of a luminaire comprising a lamp and a light emitting device according to the invention.

[0089] As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.2025P80102EP01

[0090] 9

[0091] DETAILED DESCRIPTION

[0092] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

[0093] Fig. 3 shows a cross-sectional side view of a light emitting device 1 according to the invention. Generally, and irrespective of the embodiment, the light emitting device 1 comprises an optical cavity 3, at least one LED filament 4, and at least one beam shaping optical element 8. To reduce or minimize the distortion of the omnidirectional light emission of (each of) the LED filaments 4 and hence the uniformity of emission from the lighting device 1, (each) LED filament 4 comprises two (respective) opposite end points 41, 42 lying on its (respective) longitudinal axis , LF, and wherein the LED filaments 4 are supported / connected / mounted only by the (respective) opposite end points 41, 42 to relatively thin, yet robust electrical conductors 46 and kept in fixed position thereby. Thus, other mounting and / or support structures in the optical cavity 3 that may negatively affect a uniform emission of the lighting device 1 can be reduced.

[0094] The optical cavity 3 comprises a light exit window 6 and an inner surface 7. The inner surface comprises a bottom surface 71 and a circumferential surface 72. The circumferential surface 72 extends between the light exit window 6 and the bottom surface 71. The circumferential surface 72 extends perpendicular to both the light exit window 6 and the bottom surface 71. More particularly, the circumferential surface 72 and the bottom surface 71 extend at an angle P with respect to one another, where P = 90 degrees. The circumferential surface 72 connects the light exit window 6 and the bottom surface 71.

[0095] At least a part of the inner surface 7 is specular reflective. For instance, at least 50 % of the inner surface 7 may be specular reflective. Alternatively, or additionally, at least the bottom surface 71 of the inner surface 7 may be specular reflective. The circumferential surface 72 may be any one of reflective, diffusive, and specular reflective.

[0096] Alternatively, or additionally, at least a part of the inner surface 7 comprises one or more of a specular reflective element, a semi-specular reflective element, a specular reflective material, a semi-specular reflective material, a specular reflective coating, or a semi-specular reflective coating.2025P80102EP01

[0097] 10

[0098] The at least one beam shaping optical element 8 comprises a longitudinal axis LO. The at least one beam shaping optical element 8 is arranged at the light exit window 6, which extends in a plane P. The at least one beam shaping optical element 8 may alternatively be arranged at a distance from the light exit window 6, particularly between the light exit window 6 and the bottom surface 71.

[0099] The at least one LED filament 4 is configured to, in operation, emit LED filament light 5. The at least one LED filament 4 is arranged in the optical cavity 3. The at least one LED filament 4 comprises mutually opposite end points 41 and 42. The at least one LED filament 4 further comprises a center point 43 being equidistant from the end points 41, 42. The at least one LED filament 4 comprises a longitudinal axis LF and a transversal axis TF. The at least one LED filament 4 is arranged with its longitudinal axis LF extending at an angle a with the longitudinal axis LO of the at least one beam shaping optical element 8 (and / or with plane P in which the light exit window 6 extends). It applies that 0 degrees < a < 90 degrees, or 2 degrees < a < 90 degrees, or 5 degrees < a < 90 degrees. Other angles or intervals for the angle a may also apply. For instance, it may apply that 20 degrees < a < 90 degrees, or 35 degrees < a < 90 degrees, or 45 degrees < a < 90 degrees, or 60 degrees < a < 90 degrees, or 75 degrees < a < 90 degrees, or 80 degrees < a < 90 degrees, or 85 degrees < a < 90 degrees, or a = 90 degrees. As shown in Fig. 3, a = 0 degrees, or close to 0 degrees, such as 2 degrees.

[0100] The at least one LED filament 4 is arranged at a distance d from the bottom surface 71 of the optical cavity 3. The distance d may for instance be between 0 mm and half of the length of the at least one LED filament 4. The at least one LED filament 4 is further arranged symmetrically in the optical cavity 3.

[0101] Fig. 4 shows an intensity profile of the device light emitted by the light emitting device 1 according to Fig. 3. As may be seen, because only one LED filament 4 is added to the optical cavity 3, some asymmetry in the light distribution is observed. The intensity profile is asymmetric.

[0102] Fig. 5 shows a cross-sectional side view of a light emitting device 100 according to the invention. The light emitting device 100 differs from the light emitting device 1 described above and shown in Fig. 3 in virtue of the following.

[0103] The at least one LED filament 4 is arranged to be pivotable around an axis A. The axis A extends perpendicular to both of the longitudinal axis LF and the transversal axis TF. For example, axis A extends through the end point 41, 42 or through the center point 43. In Fig. 5, axis A extends through the center point 43. The at least one LED filament 4 is2025P80102EP01

[0104] 11

[0105] arranged to be pivotable around one of its end points 41, 42, as shown in Fig. 5 exemplified by the end point 41. Alternatively, the at least one LED filament 4 may be arranged to be pivotable around its center point 43.

[0106] The at least one LED filament 4 is further arranged asymmetrically in the optical cavity 3.

[0107] Fig. 6 shows an intensity profile of the device light emitted by the light emitting device 100 according to Fig. 5. As may be seen, some asymmetry in the light distribution is again observed. The intensity profile is asymmetric, but here tending more towards a batwing distribution.

[0108] Fig. 7 shows a cross-sectional side view of a light emitting device 101 according to the invention. The light emitting device 101 differs from the light emitting devices 1 and 100 described above and shown in Figs. 3 and 5 in virtue of the following.

[0109] The at least one LED filament 4 is arranged with its longitudinal axis LF extending at an angle a with a longitudinal axis LO of the at least one beam shaping optical element 8 (or with plane P), where a = 90 degrees. In other words, the at least one LED filament 4 is arranged with its longitudinal axis LF extending perpendicular to the longitudinal axis LO of the at least one beam shaping optical element 8 (or extending perpendicular to plane P in which the light exit window 6 extends).

[0110] Fig. 8 shows an intensity profile of the device light emitted by the light emitting device 101 according to Fig. 7. As may be seen, some asymmetry in the light distribution is again observed. The intensity profile is asymmetric, and here exhibiting a more pronounced batwing distribution.

[0111] Fig. 9 shows a perspective view of a light emitting device 102 according to the invention. Fig. 10 shows a cross-sectional side view of the light emitting device 102. Fig. 11 shows a close-up view of the detail marked XI in Fig. 10. The light emitting device 102 differs from the light emitting devices 1, 100 and 101 described above and shown in Figs. 3, 5 and 7 in virtue of the following.

[0112] As is best seen in Fig. 9, the light emitting device 102 comprises a plurality of LED filaments 4. The plurality of LED filaments 4 is arranged in the optical cavity 3. Each LED filament 4 of the plurality of LED filaments 4 is arranged with its longitudinal axis LF extending at an angle, a, with the longitudinal axis LO of the at least one beam shaping optical element 8 (and / or extending at an angle a with plane P in which the light exit window 6 extends). As shown in Fig. 9, a = 90 degrees with respect to both the longitudinal axis LO of the at least one beam shaping optical element 8 and with plane P in which the light exit2025P80102EP01

[0113] 12

[0114] window 6 extends (see also Fig. 10). It is noted that the angle, a, need not be the same for all LED filaments of the plurality of LED filaments 4. That is, different LED filaments of the plurality of LED filaments 4 may be arranged with their respective longitudinal axis LF extending at mutually different angles, a, with the longitudinal axis LO of the at least one beam shaping optical element 8 (and / or extending at mutually different angles a with plane P in which the light exit window 6 extends), to obtain an improved and / or desired illumination of a target area by the light emitting device. The light emitting device as shown in Fig. 9 can alternatively be considered an essentially box-shaped, elongated luminaire when provided with, for example, a driver, a junction box, a controller, and / or a power-connector.

[0115] As is best seen in Fig. 11, the light emitting device comprises two beam shaping optical elements 81, 82 arranged at the light exit window. The two beam shaping optical elements 81, 82 are separately arranged, i.e. mutually spaced in a direction perpendicular to the light exit window 6. It is also feasible to provide more than two beam shaping optical elements 81, 82. For instance, the optical element 81 may be a Gaussian diffuser, and the optical element 82 may be a beam shaping plate, such as a microlens optic plate (MLO plate). The Gaussian diffuser spreads the device light according to a Gaussian distribution with a FWHM of 10 degrees.

[0116] As is best seen in Fig. 10, the circumferential surface 72 tapers in a direction away from the bottom surface 71. Thereby, the light exit window 6 becomes larger than the bottom surface 71. More particularly, the circumferential surface 72 and the bottom surface 71 extend at an angle P with respect to one another. It applies that 75 degrees < P < 120 degrees, or 90 degrees < P < 95 degrees, or 91 degrees < P < 95 degrees. The optical cavity 3 thus comprises a tapered shape. The optical cavity 3 is further made of a specular reflective material. As further shown in Fig. 10 the two or more beam shaping elements 81, 82 are arranged on either side of a reflective element 83 that extends perpendicularly from the light exit window 6 towards and onto the bottom surface 71, thus dividing the optical cavity into two or more optical sub cavities and optically separating the two or more beam shaping elements 81, 82.

[0117] Fig. 12 shows an intensity profile of the device light emitted by the light emitting device 101 according to Figs. 9-11. As may be seen, very little, if indeed any, asymmetry in the light distribution is observed. The intensity profile is thus symmetric, or at least almost symmetric, and here exhibiting a clearly defined batwing distribution. This resulting intensity profile or beam shape is optimal for uniform illumination of a space or object, such as a table. The improved illumination uniformity has the advantage that the2025P80102EP01

[0118] 13

[0119] spacing between light emitting devices 102, such as luminaires, can be increased, which in turn provides for a cost saving installation.

[0120] Fig. 13 shows an exemplary lamp 300 comprising a light emitting device 1, 100, 101, 102 according to any embodiment of the invention.

[0121] The lamp 300 further comprises a driver or controller 305 configured for controlling the one or more LED filaments 4 of the light emitting device 1, 100, 101, 102. The controller 305 is configured to power the one or more LED filaments 4 via electrical circuitry (not visible on the figures) of the light emitting device 1, 100, 101, 102. The light emitting device 1, 100, 101, 102 may also comprise a controller 10, which may or may not be separate from the controller 305. In other words, the controller 305 and the controller 10 of the light emitting device 1, 100, 101, 102 may be integrated into one and the same driver or controller, or they may be mutually separate units.

[0122] The lamp 300 further comprises an envelope 301 at least partially enveloping the at least one light emitting device 1, 100, 101, 102. The lamp 300 further comprises a cap 303. As shown in Fig. 13, the controller 305 is arranged within the envelope 301. When comprising a cap 303, the controller 305 may also be arranged inside the cap 303 such that it is hidden from view. The lamp 300 further comprises threading 302 for connection to a socket, and a terminal 304 for connection to a source of electrical energy.

[0123] The envelope 301 of the lamp 300 may further and optionally be provided with a coating (not shown), such as a reflective coating, covering at least a part of the envelope 301.

[0124] Turning finally to Fig. 14, an exemplary luminaire in the form of a pendant 400 is shown. The pendant 400 comprises a light emitting device 1, 100, 101, 102 according to any embodiment of the invention. The light emitting device 1, 100, 101, 102 is as shown in Fig. 13 provided within a lamp 300 in the form of a light bulb.

[0125] As is also mentioned above, the light bulb further comprises a transparent envelope (cf. transparent envelope 301 of lamp 300) at least partially enveloping the at least one light emitting device 1, 100, 101, 102. The transparent envelope may be shaped in any feasible shape, for example such as to resemble the shape of any one of a standard light bulb, a globe light bulb, a candlelight bulb, a customized light bulb and even a spiral light bulb. The transparent envelope may comprise a luminescent material. The transparent envelope may be a glass envelope.2025P80102EP01

[0126] 14

[0127] It is noted that the pendant 400, or the luminaire, does not comprise the exit surface of the luminaire does comprise a beam shaping optical element 8 arranged at a light exit surface of the pendant 400, or the luminaire.

[0128] The pendant 400 further comprises a socket 401 for connecting the lamp 300, and thereby the light emitting device 1, 100, 101, 102, to the pendant 400. The socket 401 is adapted to cooperate with the base 303 of the lamp 300. The socket 401 may comprise a threading adapted to cooperate with the threading 302 of the lamp 300. The socket 401 may comprise a terminal adapted to cooperate with the terminal 304 of the lamp 300. The pendant 400 further comprises a reflector or screen 403.

[0129] The pendant 400 may further comprise a driver 402 configured for controlling the light emitting device 1, 100, 101, 102. The driver 402 may or may not be the same unit as the controller 305 described above. In other words, the driver 402 and the controller 305 may be integrated into one and the same driver or controller, or they may be mutually separate units. Alternatively, or additionally, the light emitting device 1, 100, 101, 102 may also comprise a controller 10, which may or may not be separate from one or both of the driver 402 and the controller 305.

[0130] As shown in Fig. 14, the driver 402 is arranged on a reflector or screen 403 of the pendant 400. The driver may also be arranged within or incorporated into the reflector or screen 403. The pendant 400 further comprises an electrical wiring 404 for connection to a source of electricity, such as a mains.

[0131] It is noted that the pendant 400 shown in Fig. 14 is only one example of a luminaire according to the invention. Any suitable type of luminaire may be envisaged, such as but not limited to, a standing luminaire, a wall hung luminaire, a chandelier, a reading luminaire, an outdoor luminaire, and a table luminaire.

[0132] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

[0133] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person 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 measured cannot be used to advantage.2025P80102EP01

[0134] 15 LIST OF REFERENCE NUMBERS:

[0135] 1, 100, 101, 102 light emitting device

[0136] 2 device light

[0137] 3 optical cavity

[0138] 4 LED filament

[0139] 5 LED filament light

[0140] 6 light exit window

[0141] 7 inner surface

[0142] 8, 81, 82 beam shaping optical element

[0143] 41, 42 end points

[0144] 43 center point

[0145] 46 electrical conductors

[0146] 71 bottom surface

[0147] 72 circumferential surface

[0148] 83 reflective element

[0149] 300 lamp

[0150] 301 envelope

[0151] 302 threading

[0152] 303 cap, base

[0153] 304 terminal

[0154] 305 driver, controller

[0155] 400 luminaire, pendant

[0156] 401 socket

[0157] 402 driver

[0158] 403 screen

[0159] 404 wiring

[0160] A axis

[0161] d distance

[0162] LF longitudinal axis of filament

[0163] LO longitudinal axis of optical element

[0164] TF transversal axis

[0165] P plane in which the light exit window extends

Claims

2025P80102EP0116CLAIMS:

1. A light emitting device (1) configured to, in operation, emit device light (2), the light emitting device (1) comprising an optical cavity (3), at least one LED filament (4) configured to, in operation, omnidirectionally emit LED filament light (5), the at least one LED filament being arranged in the optical cavity (3), and at least one beam shaping optical element (8), whereinthe optical cavity (3) comprises a light exit window (6) and an inner surface (7), the inner surface comprising a bottom surface (71) and a circumferential surface (72) extending between the light exit window and the bottom surface, whereinat least a part of the inner surface (7) is specular reflective, and wherein the at least one LED filament (4) comprises a longitudinal axis (LF) and a transversal axis (TF), and two opposite end points (41, 42) lying on the longitudinal axis (LF), wherein the at least one LED filament (4) is connected and mounted by the opposite end points (41, 42) to electrical conductors (46), wherein at least 50% of the extent of the at least one LED filament (4) is unsupported, and the at least one LED filament is arranged with the longitudinal axis (LF) extending at an angle, a, with a longitudinal axis (LO) of the at least one beam shaping optical element (8), wherein 2 degrees < a < 90 degrees.

2. A light emitting device according to claim 1, wherein the light emitting device (1) comprises a plurality of LED filaments (4) arranged in the optical cavity (3), wherein each LED filament of the plurality of LED filaments (4) is arranged with its longitudinal axis (LF) extending at an angle, a, with the longitudinal axis (LO) of the at least one beam shaping optical element (8), wherein 2 degrees < a < 90 degrees.

3. A light emitting device according to claim 1 or 2, wherein 20 degrees < a < 90 degrees, or 35 degrees < a < 90 degrees, or 45 degrees < a < 90 degrees, or 60 degrees < a < 90 degrees, or 75 degrees < a < 90 degrees, or 80 degrees < a < 90 degrees, or 85 degrees < a < 90 degrees, or a = 90 degrees.2025P80102EP01174. A light emitting device according to any one of the above claims, wherein the at least one beam shaping optical element (8) is arranged at the light exit window (6).

5. A light emitting device according to any one of the above claims, wherein the at least one LED filament (4) is arranged at a distance (d) from the bottom surface (71) of the optical cavity (3).

6. A light emitting device according to any one of the above claims, wherein the at least one LED filament (4), or each LED filament of the plurality of LED filaments (4), is arranged to be pivotable around an axis (A) extending perpendicular to the longitudinal axis (LF) and to the transversal axis (TF).

7. A light emitting device according to any one of the above claims, wherein the at least one LED filament (4), or each LED filament of the plurality of LED filaments (4), is arranged to be pivotable around one of its end points (41, 42), or around its center point (43).

8. A light emitting device according to any one of the above claims, wherein one or more of the following applies:at least 50 % of the inner surface (7) is specular reflective, and at least the bottom surface (71) of the inner surface (7) is specular reflective.

9. A light emitting device according to any one of the above claims, wherein at least a part of the inner surface (7) comprises one or more of a specular reflective element, a semi-specular reflective element, a specular reflective material, a semi-specular reflective material, a specular reflective coating, and a semi-specular reflective coating.

10. A light emitting device according to any one of the above claims, wherein the at least one LED filament (4), or each LED filament of the plurality of LED filaments (4), is arranged asymmetrically in the optical cavity (3), or whereinthe at least one LED filament (4), or each LED filament of the plurality of LED filaments (4), is arranged symmetrically in the optical cavity (3).

11. A light emitting device according to any one of the above claims and comprising two or more beam shaping optical elements (81, 82) arranged at the light exit2025P80102EP0118window, the two or more beam shaping optical elements being split by a reflective element (83) that extends from the light exit window (6) towards the bottom surface (71), wherein the at least one LED filament (4) is arranged with the longitudinal axis (LF) extending at the angle, a, with a longitudinal axis (LO) of at least one of the at least two beam shaping optical elements (81, 82).

12. A light emitting device according to any one of the above claims, wherein the circumferential surface (72) tapers in a direction away from the bottom surface (71) such that the light exit window (6) is larger than the bottom surface (71), orwherein the circumferential surface (72) extends perpendicular to the light exit window (6) and the bottom surface (71).

13. A light emitting device according to any one of the above claims, wherein the circumferential surface (72) and the bottom surface (71) extend at an angle (P) with respect to one another, wherein 75 degrees < P < 120 degrees, or 90 degrees < P < 95 degrees, or 91 degrees < P < 95 degrees, or p = 90 degrees.

14. A light emitting device (1) according to any one of the above claims, wherein the at least one LED filament (4) is at least two LED filaments (4), wherein the at least two LED filaments (4) are arranged at mutually different angles a with respect to the longitudinal axis (LO) of the beam shaping optical element (8) arranged at the light exit window (6).

15. A lamp (300) or a luminaire (400) comprising a light emitting device (1) according to any one of the above claims.

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