FIELD OF THE INVENTION

The present invention relates to a lighting device comprising an LED light source and a rod light guide arrangement. The present invention also relates to a lamp comprising such a lighting device, and to a lighting system comprising such a lamp.

BACKGROUND OF THE INVENTION

In US2013114266A1, reflective unit for using with a light guiding element is disclosed. The light guiding element includes a light entrance portion and a light exit portion. The light exit portion has a first concave portion dented toward the light entrance portion. The reflective unit includes a fixing member and a reflective member. The fixing member is arranged around the perimeter of the upper end of the light exit portion. The reflective member is arranged on the fixing member for covering the first concave portion and forming a conical-shaped light propagating space.

In WO 2019/157501 a luminaire is disclosed that includes (i) a first optical system to output light having a first output light distribution and a second optical system arranged adjacent the first optical system and to output light having a second different output light distribution; and (ii) a first light engine optically coupled to an input aperture of the first optical system and a second light engine optically coupled to an input aperture or the second optical system, the first and second light engine to allow independent control of amounts of light provided to the first and second optical systems.

US 2011/309735 discloses a light bulb having a light guide configured as a hollow body surrounding an internal volume. The light guide is open at its proximal and distal ends and has inner and outer surfaces and an end surface at the proximal end that provides a light input edge. A solid-state light source is optically coupled to the light input edge of the light guide, such that light from the solid-state light source travels in the light guide by total internal reflection. The solid-state light source is thermally coupled to a housing at the proximal end of the light guide. The housing contains vents for air flow and convection cooling through the internal volume. Light-extracting optical elements at least one of the inner surface and the outer surface of the light guide are for extracting light from the light guide.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an LED lighting device with a rod light guide arrangement having increase performance and/or functionality.

According to a first aspect of the invention, this and other objects are achieved by a lighting device, comprising: an LED light source comprising a first set of LEDs adapted to emit first LED light and a second set of LEDs adapted to emit second LED light; and a rod light guide arrangement comprising a longitudinal optical axis, a first inner light guide, and a second outer light guide co-axial with the longitudinal optical axis and the first inner light guide, wherein the first inner light guide has a first end for in-coupling at least part of the first LED light and is adapted to light-guide at least part of the in-coupled first LED light as light- guided light based on total internal reflection in a direction to a second end of the first inner light guide opposite said first end of the first inner light guide, wherein the second outer light guide has a first end for in-coupling at least part of the second LED light and is adapted to light-guide at least part of the in-coupled second LED light as light-guided light based on total internal reflection in a direction to a second end of the second outer light guide opposite said first end of the second outer light guide, wherein one of the first inner light guide and the second outer light guide is provided with a first tapered reflector arranged at its second end for reflecting at least part of the light-guided light (of/in that light guide) away from the longitudinal optical axis to provide first reflected light, and wherein the other of the first inner light guide and the second outer light guide a. is provided with a second tapered reflector arranged at its second end for reflecting at least part of the light-guided light (of/in that light guide) away from the longitudinal optical axis to provide second reflected light, which second tapered reflector has a reflective surface arranged at a different angle relative to the longitudinal optical axis than a reflective surface of the first tapered reflector, or b. is provided with no reflector (such as a tapered reflector) at its second end.

In embodiments, the reflectivity of the reflective surface may be at least 80%, preferably at least 85%, more preferably at least 88%, most preferably at least 90%. The higher the reflection the higher the efficiency.

In embodiments, the reflective surface may be diffuser reflective or specular reflective. A diffuse reflective surface has generally/relatively a higher reflectivity, while a specular reflective surface has better beam-shaping properties. The present invention is based on the understanding that by having (at least) two individual sets of LEDs and (at least) two corresponding light guides, wherein at least one of the light guides has a tapered reflector opposite to the light in-coupling end, improved spatial light distribution in a rod lightguide based lighting device/lamp can be achieved. Furthermore, (static or dynamic) beam-shaping in a rod lightguide based lighting device/lamp can be achieved.

The lighting device may further comprise a controller configured to individually control the first set of LEDs and the second set of LEDs relative to each other. In this way, dynamic beam shaping may be provided. For static beam shaping, no controller is needed.

The controller may be configured to individually control the first set of LEDs and the second set of LEDs relative to each other such that the first LED light has a first luminous flux LF1 and the second LED light has a second luminous flux LF2, wherein in a first control mode LF1/FL2>2 and in a second control mode LFl/LF2<0.5.

In one embodiment, the first inner light guide is provided with the first tapered reflector, and the second outer light guide is provided with no reflector (such as a tapered reflector) at its second end. Simulation results show that one here can switch between a bottom/side light distribution (when the first LEDs are on and the second LEDs are off), a top light distribution (when the first LEDs are off and the second LEDs are on), and various possible combined light distributions including an omnidirectional light distribution (when both the first LEDs and the second LEDs are on).

In another embodiment, the second outer light guide is provided with the first tapered reflector, and the first inner light guide is provided with no reflector (such as a tapered reflector) at its second end. Simulation results show that this embodiment shows a better side light distribution than the previous embodiment.

In yet another embodiment, the first inner light guide is provided with the first tapered reflector, and the second outer light guide is provided with the second tapered reflector. Simulation results show that with this embodiment, different side light distributions can be obtained.

The reflective surface of the second tapered reflector may have a greater angle relative to the longitudinal optical axis than the reflective surface of the first tapered reflector (so as to reflect light-guided light more sideways than the reflective surface of the first tapered reflector). Alternatively, the reflective surface of the second tapered reflector may have a smaller angle relative to the longitudinal optical axis than the reflective surface of the first tapered reflector (so as to reflect light-guided light less sideways than the reflective surface of the first tapered reflector). The difference in angle may be at least 5 degrees, preferably at least 10 degrees, more preferably at least 15 degrees, and most preferably at least 20 degrees.

The reflective surface of the first tapered reflector may have an angle a relative to the longitudinal optical axis in a range from 32° to 43°, wherein the angle (P) of the reflective surface of any second tapered reflector is in a range from 32° to 43°. This corresponds to an apex angle of the first and/or second tapered reflector in a range from 64° to 86°.

The tapered reflector of the first inner light guide may be cone-shaped with its point facing the first end of the first inner light guide, whereas the tapered reflector of the second outer light guide may be truncated cone-shaped with its narrower end facing the first end of the second outer light guide. Correspondingly, the first inner light guide may be an elongated right circular solid cylinder, and the second outer light guide may be an elongated right circular hollow cylinder.

The color point and/or color temperature of the first and second LED light is the same. A similar color point may be defined as Ax<0.02 (especially Ax<0.01) and/or Ay<0.02 (especially Ay<0.01). (A CIE 1931 color space may be used. The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision.). A similar correlated color temperature may be defined as ACCT<300K. Alternatively, the color point of the first LED light and the color point of the second LED light are different e.g. Ax>0.05 (especially Ax>0.1) and/or Ay>0.05 (especially Ay>0.1) and e.g. ACCT>500K (especially ACCT>1000K).

In a further embodiment, the LED light source further comprises a third set of LEDs adapted to emit third LED light, wherein the rod light guide arrangement further comprises a third light guide co-axial with the first inner light guide and the second outer light guide, wherein the third light guide has a first end for in-coupling at least part of the third LED light and is adapted to light-guide at least part of the in-coupled third LED light as light-guided light based on total internal reflection in a direction to a second end of the third light guide opposite said first end of the third light guide, and wherein the third light guide is provided with no reflector (such as a tapered reflector) at its second end. In this way, further beam-shaping options and/or refined distributions can be achieved. The third light guide could for example be an innermost light guide of the rod light guide arrangement. Furthermore, the controller (if any) may here be configured to individually control the first set of LEDs and the second set of LEDs and the third set of LEDs relative to each other.

According to a second aspect of the invention, there is provided a lamp, comprising: a lighting device according to the first aspect; a base for mechanically and electrically connecting said lamp to a socket of a luminaire; an envelope at least partly enclosing said lighting device; and optionally an antenna configured for sending and/or receiving data to/from an electronic device remote from said lamp. The electronic device could for example be a remote user interface and/or a remote sensor.

According to a third aspect of the invention, there is provided lighting system, comprising: a lamp according to the second aspect; and a remote user interface and/or a remote sensor, wherein the ratio between the first LED light and the second LED light is adapted based on input from said remote user interface and/or remote sensor.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiments of the invention.

Fig. la is a side view of a lighting device according to an embodiment of the present invention.

Fig. lb is a perspective view of the lighting device of fig. la.

Figs. Ic-e show light distributions of the lighting device of figs. la-b.

Fig. 2a is a side view of a lighting device according to another embodiment of the present invention.

Fig. 2b is a perspective view of the lighting device of fig. 2a.

Figs. 2c-e show light distributions of the lighting device of figs. 2a-b.

Fig. 3a is a side view of a lighting device according to yet another embodiment of the present invention.

Fig. 3b is a perspective view of the lighting device of fig. 3a.

Figs. 3c-e show light distributions of the lighting device of figs. 3a-b.

Fig. 4 is a top view of an LED light source of the of the lighting device of figs. la-b/2a-b/3a-c. Fig. 5a is a side view of a lighting device according to a further embodiment of the present invention.

Fig. 5b is a top view of an LED light source of the of the lighting device of fig. 5a.

Fig. 6 is a schematic side view of a lamp according to another aspect of the present invention.

As illustrated in the figures, like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

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.

Figs, la-b illustrate a lighting device 10 according to an embodiment of the present invention.

The lighting device 10 comprises an LED light source 12. The LED light source 12 comprises a first set of LEDs 14a adapted to emit first LED light 16a. The LED light source 12 further comprises a second set of LEDs 14b adapted to emit second LED light 16b. The first set of LEDs 14a and the second set of LEDs 14b may be mounted on a carrier 18, for example a printed circuit board (PCB), as also shown in fig. 4. The first set of LEDs 14a may comprise one or more LEDs e.g. one or more white LEDs emitting white light, particular one or more phosphor converted LEDs such as a blue LEDs covered by a phosphor which partly converts the blue light into yellow and red light. Alternatively or in addition, one or more blue LEDs emitting blue light, one or more green LEDs emitting green light, and one or more red LEDs emitting red light may be used e.g. to provide white light (and colored light). Likewise, the second set of LEDs 14a may comprises one or more LEDs e.g. one or more white LEDs emitting white light, particular one or more phosphor converted LEDs such as a blue LEDs covered by a phosphor which partly converts the blue light into yellow and red light. Alternatively or in addition, one or more blue LEDs emitting blue light, one or more green LEDs emitting green light, and one or more red LEDs emitting red light may be used e.g. to provide white light (and colored light). In case of colored LED light 16a-b, the color point (on the CIE 1931 color space chromaticity diagram) of the first and second LED light 16a-b could be the same or different. That is, the color of the first and second and LED light 16a-b may be the same. Furthermore, the color temperature of the first and second and LED light 16a-b is preferably the same. Further possible details of the LED light source 12 will be described later on.

The lighting device 10 further comprises a rod light guide arrangement 20.

The rod light guide arrangement 20 comprises a (central) longitudinal/optical axis 22, a first inner light guide 24a, and a second outer light guide 24b. The second outer light guide 24b is co-axial with and the first inner light guide 24a (and the axis 22).

The first inner light guide 24a may be an elongated right circular solid cylinder. It may have a length L in the range of 3-15 cm, and a diameter D in the range of 0.3-3cm. The first inner light guide 24a may for example be made of (transparent) polymer such as for example (transparent) polycarbonate (PC) or poly(methyl methacrylate) (PMMA).

The first inner light guide 24a has a first end 26a facing the first set of LEDs 14a for in-coupling at least part of the first LED light 16a into the first inner light guide 24a. The LEDs 14a may for example be arranged in a circle 27a on the carrier 18, which circle 27a may (substantially) match the cross-section of the first inner light guide 24a, please see fig. 4. The first set may for example consist of three LEDs 14a, but it could alternatively consist of fewer or more LEDs 14a. Furthermore, the first inner light guide 24a is adapted to light-guide at least part of the in-coupled first LED light as light-guided light 28a based on total internal reflection (TIR) in a direction to a second end 26a’ of the first inner light guide 24a, which second end 26a’ is opposite said first end 26a.

In the present embodiment, the first inner light guide 24a is provided with a (first) tapered reflector 30a at the second end 26a’ of the first inner light guide 24a. The first tapered reflector 30a is adapted to reflect at least part of the light-guided light 28a to the side, away from the longitudinal optical axis 22, to provide (first) reflected light 32a. The first tapered reflector 30a may here be cone-shaped, with its point 34 facing the first end 26a of the first inner light guide 24a. Furthermore, the first tapered reflector 30a may have a (first) reflective surface 36a arranged at an angle a relative to the longitudinal optical axis 22. The reflective surface 36a may for example be made of a polymer such as e.g. polycarbonate (PC) or poly(methyl methacrylate) (PMMA) filled with reflective particles (e.g. BaSO4, A12O3 and/or TiO2 particles) or a reflective layer/coating may be used (e.g. a thin layer of silver or aluminium which can be applied with CVD or PVD. The angle a may for example be in the range of 32°-43°.

The second outer light guide 24b may be an elongated right circular hollow cylinder. It may have (substantially) the same length L as the first inner light guide 24a, i.e. in the range in the range of 3-15cm. Furthermore, the inner diameter DI of the elongated right circular hollow cylinder/second outer light guide 24b may be (substantially) the same as the aforementioned diameter D, i.e. in the range of 0.3-3cm. The outer diameter D2 of the elongated right circular hollow cylinder/second outer light guide 24b may be in the range of 0.6-5cm. The second outer light guide 24b may for example be made of (transparent) polymer such as for example (transparent) polycarbonate (PC) or poly(methyl methacrylate) (PMMA).

The second outer light guide 24b has a first end 26b facing the second set of LEDs 14b for in-coupling at least part of the second LED light 16b into the second outer light guide 24b. The LEDs 14b may for example be arranged in a ring 27b on the carrier 18, which ring 27b may (substantially) match the cross-section of the second outer light guide 24b, please see fig. 4. The second set may for example consist of nine LEDs 14b, but it could alternatively consist of fewer or more LEDs 14b. Furthermore, the second outer light guide 24b is adapted to light-guide at least part of the in-coupled second LED light as light-guided light 28b based on total internal reflection (TIR) in a direction to a second end 26b’ of the second outer light guide 24b, which second end 26b’ is opposite said first end 26b.

In the present embodiment, the second outer light guide 24b does not have any reflector at its second end 26b’. Instead, at least part of the light-guided light 28b may be out- coupled through the second end 26b’ to provide out-coupled light 38b. In other words, at least part of the light-guided light 28b exits at the second end 26b’ if not covered by a reflector. Hence, the second end 26b’ of the second outer light guide 24b could here be referred to a light out-coupling surface or light exit surface. The second end 26b’ could be a “plain” surface, or be provided with means for enhancing out-coupling of light. Various such means are known per se for the skilled person.

The lighting device 10 may further comprise a controller 40. The controller 40 is configured to individually control the first set of LEDs 14a and the second set of LEDs 14b relative to each other. As such, the controller 40 may be connected to the LED light source 12. Furthermore, the controller 40 may be adapted to receive control data (e.g. via a cable or via an antenna 106, see fig. 6) from a remote user interface 108, for example a remote control or smartphone or tablet operated by a user. In this way, the user can control/set the beam- shaping of the lighting device 10. The controller 40 could also receive control data from a remote sensor 110.

In this embodiment, the controller 40/user can switch between a bottom/side light distribution as illustrated in fig. 1c when the first LEDs 14a are on and the second LEDs 14b are off, a top light distribution as illustrated in fig. Id when the first LEDs 14a are off and the second LEDs 14b are on, and various combined/weighted light distributions (one of which is illustrated in fig. le) including an omnidirectional light distribution when both the first LEDs 14a and the second LEDs 14b are on.

Figs. 2a-b illustrate a lighting device 10 according to another embodiment of the present invention. This lighting device 10 is similar to the lighting device 10 of figs, la-b, except that here the second outer light guide 24b is provided with a tapered reflector 30b at the second end 26b’ of the second outer light guide 24b, whereas the first inner light guide 24a does not have any reflector at its second end 26a’. In this embodiment, the tapered reflector 30b may be referred to as a “first” tapered reflector 30b in the context of claims 1 (option b.) and 4.

The tapered reflector 30b is adapted to reflect at least part of the light-guided light 28b to the side, away from the longitudinal optical axis 22, to provide reflected light 32b. The tapered reflector 30b may be here truncated cone-shaped with its narrower end 42 facing the first end 26b of the second outer light guide 24b. Specifically, the tapered reflector 30b may comprise or consist of a reflective surface 36b being the lateral surface of a right circular conical frustum. The reflective surface 36b may be arranged at an angle P relative to the longitudinal optical axis 22. The reflective surface 36b may for example be made of a polymer such as e.g. polycarbonate (PC) or poly(methyl methacrylate) (PMMA) filled with reflective particles (e.g. BaSO4, A12O3 and/or TiO2 particles) or a reflective layer/coating may be used (e.g. a thin layer of silver or aluminium which can be applied with CVD or PVD. The angle P may for example be in the range of 32°-43°.

As mentioned above, in the present embodiment, the first inner light guide 24a does not have any reflector at its second end 26a’ . Instead, at least part of the light-guided light 28a may be out-coupled through the second end 26a’ to provide out-coupled light 38a. Hence, the second end 26a’ of the first inner light guide 24a could here be referred to a light out-coupling surface. The second end 26a’ could be a “plain” surface, or be provided with means for enhancing out-coupling of light.

In the embodiment of figs. 2a-b, the controller 40/user can switch between various light distribution as illustrated in figs. 2c-e. Fig. 2c shows a top emission when the first LEDs 14a are on and the second LEDs 14b are off. Fig. 2d shows a side emission when the first LEDs 14a are off and the second LEDs 14b are on. Fig. 2e shows an exemplary weighted combination when both the first LEDs 14a and the second LEDs 14b are on. Overall, simulation results show that this embodiment shows a better side light distribution than the previous embodiment.

Figs. 3a-b illustrate a lighting device 10 according to yet another embodiment of the present invention. This lighting device 10 is similar to the lighting devices 10 of figs, la-b and 2a-b, except that here the both the first inner light guide 26a and the second outer light guide 26b are provided with a tapered reflector 30a and 30b, respectively. Please note that in this embodiment, the tapered reflector 30b may be referred to as a “second” tapered reflector 30b in the context of claims 1 (option a.) and 5. Hence, in this embodiment the first inner light guide 24a is provided with the first tapered reflector 30a at its second end 26a’ and the second outer light guide 24b is provided with the second tapered reflector 30b its second end 26b’. And both reflected light 32a and reflected light 32b may be provided.

The reflective surface 36b of the second tapered reflector may be arranged at a different angle P relative to the longitudinal optical axis 22 than the reflective surface 36a of the first tapered reflector 30a. That is, P a. The reflective surface 36b of the second tapered reflector 30b may have a greater angle P relative to the longitudinal optical axis 22 than the reflective surface 36a of the first tapered reflector (P > a), so as to generally reflect light- guided light more sideways than the reflective surface 36a of the first tapered reflector 30a, as illustrated in fig. 3 a. Alternatively, the reflective surface 36b of the second tapered reflector 30b may have a smaller angle P relative to the longitudinal optical axis 22 than the reflective surface 36a of the first tapered reflector (P < a), so as to generally reflect light- guided light less sideways than the reflective surface 36a of the first tapered reflector 30a (not shown). The difference in angle may be at least 5 degrees.

In the embodiment of figs. 3a-b, the controller 40/user can switch between various side light distribution as illustrated in figs. 3c-e. Fig. 3c shows a semi-top-side emission when the first LEDs 14a are on and the second LEDs 14b are off. Fig. 3d shows a side emission when the first LEDs 14a are off and the second LEDs 14b are on. Fig. 3e shows an exemplary weighted combination when both the first LEDs 14a and the second LEDs 14b are on.

Fig. 5a illustrates a lighting device 10 according to a further embodiment of the present invention. This lighting device 10 is similar to the lighting device 10 of figs. 3a-b, but further comprises a third set of LEDs 14c and a third light guide 24c. The third set of LEDs 14c is adapted to emit third LED light 16c. The third set of LEDs 14c may be mounted on the carrier 18, as also shown in fig. 5b. The third set of LEDs 14c may be adapted to emit white and/or colored LED light 16c.

The third light guide 24c is here an innermost light guide 24c of the rod light guide arrangement 20 and co-axial with the first inner light guide 24a and the second outer light guide 24b. The third innermost light guide 24c may be an elongated right circular solid cylinder, whereas the first inner light guide 24a here may be an elongated right circular hollow cylinder. Accordingly, the first tapered reflector 30a may here comprise or consist of a reflective surface 36a being the lateral surface of a right circular conical frustum.

The third light guide 24c has a first end 26c facing the third set of LEDs 14c for in-coupling at least part of the third LED light 16c into the third innermost light guide 24c. Furthermore, the third light guide 24c is adapted to light-guide at least part of the incoupled third LED light as light-guided light 28c based on total internal reflection (TIR) in a direction to a second end 26c’ of the third light guide 24c, which second end 26c’ is opposite said first end 26c. The third light guide 24c does not have any reflector at its second end 26c’ . Instead, at least part of the light-guided light 28c may be out-coupled through the second end 26c’ to provide out-coupled light 38c.

The controller 40 is here configured to individually control the first set of LEDs 14a and the second set of LEDs 14b and the third set of LEDs 14c relative to each other. In this way, further beam-shaping options and/or refined distributions can be achieved over the previous embodiments.

Fig. 6 illustrates a lamp 100 comprising the lighting device 10. The lamp 100 may be a retrofit lamp. The lamp 100 further comprises a base 102 for mechanically and electrically connecting the lamp 100 to a socket of a luminaire (not shown). The lamp 100 further comprises an envelope 104 at least partly enclosing the lighting device 10, specifically the rod light guide arrangement 20 thereof. The lamp 100 may further comprise an antenna 106 configured for sending and/or receiving data to/from a user interface 108 and/or sensor 110 remote from the lamp 100. The lamp 100 and the remote user interface 108 and/or remote sensor 110 may be referred to as a lighting system 200.

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. For example, for static beam shaping, the controller 40 can be omitted. Furthermore, the third light guide could alternatively be an intermediate or outermost light guide of the rod light guide arrangement 20.

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.