Patent Description:
Incandescent lamps are rapidly being replaced by LED based lighting solutions. It is nevertheless appreciated and desired by users to have retrofit lamps which have the look of an incandescent bulb. For this purpose, one can simply make use of the infrastructure for producing incandescent lamps based on glass and replace the filament with LEDs emitting white light. One of the known concepts is based on LED filaments placed in such a bulb. The appearances of these lamps are highly appreciated as they look highly decorative. This type of LED filament lamp is selling in high volumes on the market.

For instance, <CIT> discloses an incandescent lamp comprising a twisted light guide consisting of several pillars. The pillars of the light guide are twisted such as to have the shape of a helical spring. Furthermore, the pillars of the light guide are each rod-shaped with a circular transversal cross-section.

However, current LED filament lamps are rather expensive, for instance in terms of the costs of LED filaments and/or assembly costs. Also, current LED filament lamps have an undesired, typically yellow or yellowish, appearance, and they do not allow for color or color temperature tunability.

There is thus still a desire for providing a light emitting device allowing for producing an incandescent lamp, and in particular a LED filament luminaire, which light emitting device is cheaper to manufacture, which emits light with a clearer white appearance, and which allows for color or color temperature tunability of the emitted light.

In <CIT> a lightguide is disclosed that functions as a luminaire. The luminaire includes at least one solid state light source, such as an LED, and a lightguide configured to receive light from the solid state light source. Light from the light source is coupled into the lightguide and transported within it by total internal reflection until the light exits the lightguide. A shape of the lightguide causes and directs extraction of the light, and can also be used to create a particular pattern of the extracted light. Such shapes include linear wedges and twisted wedges. Optical films can be included on the light input and output surfaces of the lightguide.

It is an object of the present invention to overcome or reduce at least some of these problems, and to provide a light emitting device which is cheaper to manufacture, which emits light with a clearer white appearance, and which allows for color or color temperature tunability of the emitted light.

According to a first aspect of the invention, this and other objects are achieved by means of a light emitting device comprising at least one LED light source adapted for, in operation, emitting light source light, and an elongated light guide comprising a height direction, a width direction, a depth direction and a central longitudinal axis extending in the height direction, where the elongated light guide further comprises.

Thereby, and especially by providing a light guide with the above described structure, a light emitting device is provided which has a particularly simple structure, and which is simpler to assemble. Thus, a light emitting device is provided which is cheaper to manufacture.

Furthermore, by providing that the elongated light guide is twisted around the central longitudinal axis of the light guide, and that the light out-coupling element is elongated, a light emitting device is provided which emits light with a clearer white appearance, and which allows for color or color temperature tunability of the emitted light.

In an embodiment, the elongated light guide is configured to guide more than <NUM> %, more than <NUM> %, or more than <NUM> % of the light source light which is coupled into the light guide at the light in-coupling element via total internal reflection to the light out-coupling element.

In an embodiment, the elongated light guide further comprises a third major surface and a fourth major surface arranged extending opposite to the third major surface, the third major surface and the fourth major surface extending in an angle, β, with respect to the first major surface and the second major surface, a third minor surface and a fourth minor surface arranged extending opposite to the third minor surface, the third minor surface and the fourth minor surface extending in an angle, β, with respect to the first minor surface and the second minor surface, and a third end and a fourth end arranged extending opposite to the third end, the third end and the fourth end extending in an angle, β, with respect to the first end and the second end.

Thereby, and especially by providing a light guide with the above described structure, a light emitting device is provided which has a particularly simple structure, and which is simpler to assemble, while allowing for a clearer and brighter light output. Thus, a light emitting device is provided which is cheaper to manufacture and which provides a brighter white light output.

In an embodiment, the angle, β, is <NUM> degrees.

When twisting the elongated light guide around the central longitudinal axis of the light guide, this choice of angle, β, provides for a particularly well-functioning and desirable twisted shape.

In an embodiment, the elongated light guide is twisted around the central longitudinal axis of the light guide such as to have the shape of a screw, an Archimedes screw, a double screw or a double Archimedes screw.

Thereby, a light emitting device is provided which emits light with a particularly clear white appearance in a regular spiraling pattern, and which allows for color or color temperature tunability of the emitted light. Furthermore, the shape of a double screw or a double Archimedes screw provides for a light emitting device which emits light in a regular double spiraling pattern giving an especially pleasing appearance.

In an embodiment, the at least one light out-coupling element is arranged on or adjacent to at least a part of any one or more of the first minor surface, the second minor surface, the third minor surface and the fourth minor surface.

Thereby, a light emitting device is provided which emits light in a particularly regular spiraling pattern, or in a particularly regular double spiraling pattern.

In an embodiment, the at least one light out-coupling element comprises any one or more of light scattering features, light refracting features, light diffracting features and light converting features.

Such features provide for a particularly efficient out-coupling of light with very low losses.

In an embodiment, the at least one light in-coupling element is arranged at the first end, at the first minor surface (not claimed) or in the elongated light guide (claimed).

Thereby, a particularly efficient in-coupling of light into the light guide with very low losses is provided for.

According to the invention, the at least one light in-coupling element forms part of or is provided as a structure arranged adjacent to the LED light source which is provided in the shape of a LED filament. According to the invention, the LED filament extends in the height direction, H, of the light guide throughout a part or all of the light guide.

Thereby, a light emitting device with a larger degree of versatility in terms of positioning of the light in-coupling element(s) is provided for.

In an embodiment, one or more of the first minor surface, the second minor surface, the third minor surface and the fourth minor surface is adapted for collimating incident light.

Thereby, a light emitting device is provided which emits light in a spiraling pattern, or in double spiraling pattern, which is further improved in terms of regularity and appealing appearance.

In an embodiment, the at least one light incoupling means comprises anisotropic light distributing features.

In an embodiment, the at least one light out-coupling element comprises multiple surfaces.

In an embodiment, at least one of the first major surface, second major surface, third major surface and fourth major surface comprises at least one light shaping feature.

Thereby, a light emitting device is provided which emits light in a spiraling pattern, or in double spiraling pattern, which is further improved.

In an embodiment, the at least one light source comprises any one or more of a warm white LED, a cool white LED and RGB LED(s).

Thereby, a light emitting device is provided which allows for particularly efficient color or color temperature tunability of the emitted light, and where the emitted light comprises a clear white and agreeable appearance.

In an embodiment, the average intensity at the minor surfaces is I1, the average intensity at the major surfaces is I2, and I1 > <NUM>*<NUM>. Particularly, the average intensity at the minor surfaces at which a light out-coupling element is arranged is I1.

Thereby, a light emitting device is provided which emits light in a spiraling pattern, or in double spiraling pattern, which is further improved in terms of intensity and appealing appearance.

In an embodiment, at least one of the first major surface and the second major surface, the first minor surface and the second minor surface, the first end and the second end, the third major surface and the fourth major surface, the third minor surface and the fourth minor surface, and the third end and the fourth end are mutually parallel. Thereby, a light emitting device is provided which emits light with a particularly clear white appearance in a particularly regular spiraling pattern, and which allows for color or color temperature tunability of the emitted light in a particularly efficient manner.

In an embodiment, the LED light sources comprise a first light source emitting first light source light and a second light source emitting second light source light being different from the first light source light.

In an embodiment, the LED light sources comprise RGB LEDs, CW and WW LEDs, or RGBW LEDs.

In an embodiment, the light emitting device further comprises a controller for individually controlling the first light source and the second light source to tune the color and/or color temperature.

Such embodiments provide for a light emitting device which allows for a particularly efficient and well-functioning color or color temperature tunability of the emitted light.

The light emitting device may further comprise a base for connecting the light emitting device to a luminaire base and/or a luminaire socket.

The invention also relates to a luminaire or a lamp comprising a light emitting device according to the invention. Such a luminaire or such a lamp may for instance be a light bulb, an incandescent lamp or a filament lamp.

Reference is first made to <FIG>. <FIG> and <FIG> show perspective views of a light emitting device <NUM> according to a first embodiment of the invention. <FIG> shows the light emitting device <NUM> in a cross-sectional top view and <FIG> shows the light emitting device <NUM> in a cross-sectional side view.

Generally, and irrespective of the embodiment, the light emitting device <NUM> comprises at least one LED light source <NUM>, <NUM>, <NUM> adapted for, in operation, emitting light source light, an elongated light guide <NUM>, at least one light in-coupling element <NUM>, <NUM>, <NUM> and at least one light out-coupling element <NUM>, <NUM>.

The elongated light guide <NUM> generally comprises a height direction, H, a width direction, W, a depth direction, D, a central longitudinal axis, L, extending in the height direction, H, a transversal axis, T, extending in the width direction, W, and a depth axis, X, extending in the depth direction, D. Generally, the relative dimensions of the elongated light guide <NUM> are chosen such that it is larger in the height direction, H, than in the width direction, W, and in the depth direction, D, and furthermore such that it is larger in the width direction, W, than in the depth direction, D.

The elongated light guide <NUM> is generally twisted around its central longitudinal axis, L. Thereby the elongated light guide <NUM> is provided with a twisted shape, particularly twisted in a manner like a screw. The light guide <NUM> shown in <FIG> is shaped as an Archimedes screw. In principle, the light guide <NUM> may be twisted such as to have any suitable number of twists, loops or windings. To obtain a suitable spiral light effect, it is desired to twist the light guide <NUM> such that it shows at least <NUM> twists, loops or windings.

The elongated light guide <NUM> further generally comprises a first major surface <NUM> and a second major surface <NUM>. The second major surface <NUM> is arranged extending in parallel with and opposite to the first major surface <NUM> seen in the depth direction, D, of the elongated light guide <NUM>. The elongated light guide <NUM> further generally comprises a first minor surface <NUM> and a second minor surface <NUM>. The second minor surface <NUM> is arranged extending parallel with and opposite to the first minor surface <NUM> seen in the width direction, W, of the elongated light guide <NUM>. The elongated light guide <NUM> further generally comprises a first end <NUM> and a second end <NUM>. The second end <NUM> is arranged extending parallel with and opposite to the first end <NUM> in the height direction, H, of the elongated light guide <NUM>. The elongated light guide <NUM> is thus generally plate-shaped. The elongated light guide <NUM> may be made of a polymer such as PMMA, PC, PET, silicone, or the like. Generally, the relative dimensions of the elongated light guide <NUM> are chosen such that the area of the major surfaces <NUM>, <NUM> is larger than the area of the minor surfaces <NUM>, <NUM> and the area of the ends <NUM>, <NUM>, respectively, and furthermore such that the area of the minor surfaces <NUM>, <NUM> is larger than the area of the ends <NUM>, <NUM>.

The first major surface <NUM> has a first major surface area MA1 and the second major surface <NUM> has a second major surface area MA2. The first minor surface <NUM> has a first minor surface area mA1 and the second minor surface <NUM> has a second minor surface area mA2. The said surface areas may fulfill one or more of the following relations: MA1 > <NUM>*mA1, MA2 > <NUM>*mA2, MA1 = MA2 and mA1 = mA2.

In other embodiments not all mutually opposite pairs of surfaces <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM> need be parallel. Rather, in some embodiments, one or more of the first major surface <NUM> and the second major surface <NUM>, the first minor surface <NUM> and the second minor surface <NUM>, and the first end <NUM> and the second end <NUM>, respectively, may be mutually non-parallel.

The at least one LED light source <NUM>, <NUM>, <NUM> may be an LED filament <NUM> (cf. <FIG>) or one or more LEDs <NUM>, <NUM> (cf. The at least one LED light source <NUM>, <NUM>, <NUM> may be or comprise any one or more of warm white LEDs, cool white LEDs and red, green and blue (RGB) LED(s). As shown in <FIG>, the two LEDs <NUM>, <NUM> are arranged at the second end <NUM> of the light guide <NUM>. Alternatively, or additionally, LEDs may be provided at the first end <NUM> of the light guide <NUM>. Still alternatively, or additionally, LEDs may be provided at one of the first minor surface <NUM> and the second minor surface <NUM> of the light guide <NUM>. Combinations of LED light sources in the form of LED filament(s) <NUM> and LED(s) <NUM>, <NUM> are also feasible.

As shown in <FIG>, when the LED light sources are provided in the form of LED filament(s) <NUM>, the LED filament <NUM> is arranged centrally in the light guide <NUM>. More generally, the LED filament <NUM> extends in the height direction H of the light guide <NUM> throughout a part or all of the light guide <NUM>. A LED filament <NUM> generally comprises a plurality of LEDs arranged on an elongated carrier. Typically, LED filaments comprise more than <NUM> LEDs, more than <NUM> LEDs, or more than <NUM> LEDs. An encapsulant may encapsulate at least part of the plurality of LEDs. The encapsulant may comprise a phosphor and/or a luminescent material. In embodiments where a luminescent material is present in the encapsulant, the LEDs may emit UV and or blue light. In case of no luminescent material being present in the encapsulant, RGB LEDs may be used. The LED filament <NUM> has a width WF, a height HF and length LF. In an embodiment LF > <NUM>*WF and LF > <NUM>*HF. The LED filament <NUM> may be inserted in a hole in the light guide <NUM>, where the hole is provided at the central longitudinal axis L of the light guide <NUM>.

Also, more than one LED light source <NUM>, <NUM>, <NUM> may be provided. In such an embodiment, the LED light sources may comprise a first light source emitting first light source light and a second light source emitting second light source light being different from the first light source light. Furthermore, the light emitting device <NUM> may comprise a controller for individually controlling the first light source and the second light source to tune the color and/or color temperature. Examples of LED light sources for embodiments with more than one light source include RGB LEDs, CW and WW LEDs, and RGBW LEDs.

The one or more light in-coupling elements <NUM>, <NUM>, <NUM> are configured to couple the light source light into the elongated light guide <NUM>. Generally, the one or more light in-coupling elements <NUM>, <NUM>, <NUM> are arranged adjacent to the LED light source(s) <NUM>, <NUM>, <NUM>. the one or more light in-coupling elements <NUM>, <NUM>, <NUM> may thus be arranged at one or more of the first end <NUM>, at the second end <NUM>, at the first minor surface <NUM>, at the second minor surface <NUM> or, according to the invention in the elongated light guide <NUM>.

In the embodiment shown in <FIG>, one light in-coupling element <NUM> is provided. The light in-coupling element <NUM> is arranged centrally in the light guide <NUM>. The light in-coupling element <NUM> extends in the height direction H of the light guide <NUM> throughout a part or all of the light guide <NUM>. The light in-coupling element <NUM> forms part of or is provided as a structure arranged adjacent to the LED light source <NUM> which is provided in the shape of a LED filament.

<FIG> shows an alternative and non claimed embodiment of a light emitting device <NUM> differing only from the light emitting device <NUM> of <FIG> in that two LED light sources <NUM> and <NUM> and two light in-coupling elements <NUM> and <NUM> are provided. The light in-coupling elements <NUM>, <NUM> are arranged at the second end <NUM> of the light guide <NUM> between the two LED light sources <NUM> and <NUM> and the second end <NUM>.

The one or more light out-coupling elements <NUM>, <NUM> are configured to couple the light source light out of the elongated light guide. The one or more light out-coupling elements <NUM>, <NUM> are furthermore elongated. The one or more light out-coupling elements <NUM>, <NUM> may further in some embodiments comprise additional features, such as but not limited to light scattering features, light refracting features, light diffracting features and light converting features. The light out-coupling elements <NUM>, <NUM> may be scattering particles, such as BaS04, TiO2, Al2O3, or the like.

In the embodiment shown - cf. <FIG> - two light out-coupling elements are provided. The two light out-coupling elements <NUM>, <NUM> are arranged on or adjacent to at least a part of both the first minor surface <NUM> and the second minor surface <NUM>. The two light out-coupling elements <NUM>, <NUM> may also be arranged on or adjacent to all of both of the first minor surface <NUM> and the second minor surface <NUM>. Alternatively, one of the light out-coupling elements <NUM>, <NUM> may be omitted.

Turning now to <FIG> and <FIG> a perspective view and a cross-sectional top view, respectively, of a light emitting device <NUM> according to a second embodiment of the invention is shown. The light emitting device <NUM> differs from those described above in relation to <FIG> in virtue of the following features.

The light emitting device <NUM> comprises an elongated light guide <NUM>, which comprises the same general features as the light guide <NUM> shown in <FIG>. Additionally, the elongated light guide <NUM> comprises a third major surface <NUM> and a fourth major surface <NUM>. The fourth major surface <NUM> arranged extending parallel with and opposite to the third major surface <NUM>. The third major surface <NUM> and the fourth major surface <NUM> further extend in an angle, β, with respect to the first major surface <NUM> and the second major surface <NUM>. The angle, β, is shown in <FIG>. The elongated light guide <NUM> also comprises a third minor surface <NUM> and a fourth minor surface <NUM>. The fourth minor surface <NUM> is arranged extending parallel with and opposite to the third minor surface <NUM>. The third minor surface <NUM> and the fourth minor surface <NUM> further extend in an angle, β, with respect to the first minor surface <NUM> and the second minor surface <NUM>. The elongated light guide <NUM> also comprises a third end <NUM> and a fourth end <NUM>. The fourth end <NUM> is arranged extending parallel with and opposite to the third end <NUM>. The third end <NUM> and the fourth end <NUM> extend in an angle, β, with respect to the first end <NUM> and the second end <NUM>. In the embodiment shown in <FIG> and <FIG>, the angle, β, is approximately <NUM> degrees. In other embodiments, the angle, β, may be different from <NUM> degrees, such as for instance between <NUM> degrees and <NUM> degrees, or even below <NUM> degrees. Generally, the angle, β, is different from <NUM> degrees.

The third major surface <NUM> has a third major surface area MA3 and the fourth major surface <NUM> has a fourth major surface area MA4. The third minor surface <NUM> has a third minor surface area mA3 and the fourth minor surface <NUM> has a fourth minor surface area mA4. The said surface areas may fulfill one or more of the following relations: MA3 > <NUM>*mA3, MA4 > <NUM>*mA4, MA3 = MA4 and mA3 = mA3.

In other embodiments not all mutually opposite pairs of surfaces <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM> need be parallel. Rather, one or more of the first major surface <NUM> and the second major surface <NUM>, the first minor surface <NUM> and the second minor surface <NUM>, the first end <NUM> and the second end <NUM>, the third major surface <NUM> and the fourth major surface <NUM>, the third minor surface <NUM> and the fourth minor surface <NUM>, and the third end <NUM> and the fourth end <NUM> may be mutually non-parallel.

The light emitting device <NUM> further comprises four light out-coupling elements <NUM>, <NUM>, <NUM>, <NUM>. In the embodiment shown - cf. <FIG> the four light out-coupling elements <NUM>, <NUM>, <NUM>, <NUM> are arranged on or adjacent to at least a part of each of the first minor surface <NUM>, the second minor surface <NUM>, the third minor surface <NUM> and the fourth minor surface <NUM>. In other embodiments one, two or three of the light out-coupling elements may be omitted.

The elongated light guide <NUM> is also generally twisted around its central longitudinal axis, L. Thereby the elongated light guide <NUM> is provided with a double twisted shape, particularly twisted in a manner like a double screw. The light guide <NUM> shown in <FIG> is shaped as a double Archimedes screw.

In the embodiment shown in <FIG> and <FIG>, the LED light source is a LED filament <NUM>. Alternatively, or additionally, LEDs may be provided at one or more of the first end <NUM>, the second end <NUM>, the third end <NUM> and the fourth end <NUM>.

<FIG> shows a cross-sectional top view of a light emitting device <NUM> according to a third embodiment of the invention is shown. The light emitting device <NUM> differs from those described above in relation to <FIG> in virtue of that the first minor surface <NUM> and the second minor surface <NUM> comprises a collimator <NUM> and <NUM>, respectively. Thus, put in more general terms, one or more of the first minor surface <NUM>, the second minor surface <NUM>, the third minor surface <NUM> and the fourth minor surface <NUM> may be adapted for collimating incident light such that the light emitting device <NUM> emits collimated light.

<FIG> shows a cross-sectional side view of a light emitting device <NUM> according to a fourth non claimed embodiment. The light emitting device <NUM> differs from those described above in relation to <FIG> in virtue of that the at least one light incoupling means <NUM> is arranged at the first end <NUM> of the light guide <NUM>. Furthermore, the light incoupling means <NUM> comprises anisotropic light distributing features <NUM>.

<FIG> shows a cross-sectional top view of a light emitting device <NUM> according to a fifth embodiment of the invention is shown. The light emitting device <NUM> differs from those described above in relation to <FIG> in virtue of that the two light out-coupling element <NUM> and <NUM> each comprises multiple surfaces. In the embodiment shown, the two light out-coupling element <NUM> and <NUM> each comprise three surfaces <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>. Thus, in this embodiment the light out-coupling element <NUM> as arranged such that a first surface <NUM> abuts the first minor surface <NUM>, a second surface <NUM> abuts the first major surface <NUM> and a third surface <NUM> abuts the second major surface <NUM>. Similarly, the light out-coupling element <NUM> as arranged such that a first surface <NUM> abuts the second minor surface <NUM>, a second surface <NUM> abuts the first major surface <NUM> and a third surface <NUM> abuts the second major surface <NUM>. Alternatively, the light out-coupling elements <NUM>, <NUM> may also comprise two, four or five surfaces. In another alternative, the light out-coupling elements <NUM>, <NUM> may also comprise a mutually different number of surfaces.

<FIG> shows a cross-sectional side view of a light emitting device <NUM> according to a sixth embodiment of the invention is shown. The light emitting device <NUM> differs from those described above in relation to <FIG> in virtue of that the first major surface <NUM> comprises at least one, and in the embodiment shown two, light shaping features <NUM> and <NUM>. Other numbers of light shaping features may also be feasible. Put in more general terms, at least one of the first major surface <NUM>, the second major surface <NUM>, the third major surface <NUM> and the fourth major surface <NUM> may thus comprise at least one light shaping feature <NUM>, <NUM>.

Referring now again to <FIG>, a light emitting device according to any of the embodiments described herein - or indeed a combination of such embodiments - may be used in a luminaire <NUM> such as a light bulb. The luminaire <NUM> shown in <FIG> comprises by way of a non-limiting example one light emitting device <NUM> according to the invention. A luminaire may in principle also comprise more than one, such as two, three or more light emitting devices according to the invention. The light emitting device according to the invention may in thus connection be arranged in the luminaire <NUM> such that the central longitudinal axis, L, of the elongated light guide <NUM> extends in parallel with a longitudinal axis M of the luminaire <NUM> as is shown in <FIG>. Alternatively, the light emitting device according to the invention may be arranged in the luminaire <NUM> such that the central longitudinal axis, L, of the elongated light guide <NUM> extends perpendicular to the longitudinal axis M of the light emitting device <NUM>.

The luminaire <NUM> comprises a luminaire socket <NUM> and a luminaire base <NUM> for mechanically and/or electrically connecting the light emitting device <NUM> to the luminaire socket <NUM>. The luminaire socket <NUM> may furthermore comprise a terminal <NUM> for electric connection to a terminal of an external power source.

Therefore, the light emitting device may further comprise a base <NUM> for connecting the light emitting device to the luminaire base <NUM> and thereby the luminaire socket <NUM>. The luminaire socket <NUM> provides electrical power to the light source <NUM>, <NUM>, <NUM> of the light emitting device <NUM>, respectively, through the luminaire base <NUM>.

The luminaire base <NUM>, may, as shown on <FIG>, also act as a holder or support for supporting the light emitting device <NUM>.

In another embodiment it may also be feasible to omit the luminaire base <NUM>, in which case the base <NUM> of the light emitting device <NUM> is adapted for connection directly to the luminaire socket <NUM>. In yet another embodiment it may also be feasible to omit the base <NUM> of the light emitting device <NUM>, in which case the luminaire base <NUM> is adapted for connection directly to the light emitting device <NUM>.

The luminaire <NUM> may further comprise an enveloping structure or bulb <NUM> partly or fully enveloping the light emitting device <NUM>. In the embodiment shown, the envelope or bulb <NUM> is arranged in a distance from light emitting device <NUM>.

Claim 1:
A light emitting device (<NUM>) comprising:
at least one LED light source (<NUM>, <NUM>, <NUM>) adapted for, in operation, emitting light source light, and
an elongated light guide (<NUM>) comprising a height direction (H), a width direction (W), a depth direction (D) and a central longitudinal axis (L) extending in the height direction, wherein the elongated light guide further comprises:
a first major surface (<NUM>) and a second major surface (<NUM>) arranged extending opposite to the first major surface in the depth direction of the elongated light guide,
a first minor surface (<NUM>) and a second minor surface (<NUM>) arranged extending opposite to the first minor surface in the width direction of the elongated light guide, and
a first end (<NUM>) and a second end (<NUM>) arranged extending opposite to the first end in the height direction of the elongated light guide,
wherein the elongated light guide (<NUM>) further comprises at least one light in-coupling element (<NUM>, <NUM>, <NUM>) configured to couple the light source light into the elongated light guide and at least one light out-coupling element (<NUM>, <NUM>) configured to couple the light source light out of the elongated light guide, the elongated light guide being configured to guide at least a portion of the light source light which is coupled into the light guide at the light in-coupling element via total internal reflection to the light out-coupling element,
wherein the elongated light guide (<NUM>) is twisted around the central longitudinal axis of the light guide,
wherein the at least one light out-coupling element (<NUM>, <NUM>) is elongated, characterized in that
the at least one light in-coupling element (<NUM>) forms part of or is provided as a structure arranged adjacent to the LED light source (<NUM>) which is provided in the shape of a LED filament (<NUM>) extending in the height direction (H) of the light guide throughout a part or all of the light guide.