Lighting device

Abstract

The invention relates to a lighting device (10) comprising a plurality of concave reflectors (20-1, 20-2), each reflector forming a reflector cavity (25) in which a light source (21) is arranged for emitting light towards a light emission window (24). The above-mentioned kind of lighting devices are capable of emitting different light emission distributions, thereby improving their implementation in indoor applications.

Description

Technical Field

[0001] The present invention relates to a lighting device comprising a plurality of concave reflectors, each reflector forming a reflector cavity, wherein a light source for emitting light toward a light-emitting window is disposed in the reflector cavity. Background Technology

[0002] The lighting device described above is disclosed, for example, in International Patent Application No. WO2012 / 042429. The lighting device described therein allows the use of multiple concave reflectors in different numbers, shapes, and sizes (i.e., linear and / or zoned configurations). This lighting device provides a high-quality lighting solution for directly replacing so-called T5 fluorescent lamps in office and other indoor applications. The lighting device according to WO2012 / 042429 consists of a plurality of concave reflectors or reflective cups, each cup containing an LED light source and a diffuser as optical elements between the light source and the luminous window formed by the plurality of reflectors. Each optical element housed in the reflector, together with the light source, provides only collimated light emission toward the luminous window. Summary of the Invention

[0003] It is desirable to provide a lighting device of the aforementioned known type that is capable of emitting different light emission distributions, thereby improving its implementation in indoor applications.

[0004] Therefore, an illumination device is proposed, comprising: a plurality of concave reflectors, each reflector including a narrow end, a wide end, and an inclined edge wall connecting the narrow end and the wide end, thereby forming a first reflector cavity, wherein the wide end constitutes a light-emitting window; a first light source disposed within the first reflector cavity, at or near the narrow end; an optical element disposed within the first reflector cavity between the first light source and the light-emitting window, the optical element dividing the first reflector cavity into a first chamber and a second chamber; and at least one additional light source disposed outside the first reflector cavity, located in a second reflector cavity formed by adjacent inclined edge walls of the plurality of concave reflectors.

[0005] Therefore, the lighting device can switch between different lighting modes, namely collimated task lighting and ambient diffuse lighting.

[0006] In an example of the configuration of the concave reflector, the first chamber is delimited by a first edge wall portion of the edge wall, the narrow end and the optical element; and the second chamber is delimited by a second edge wall portion of the edge wall, the light emitting window and the optical element, the first edge wall portion having a first reflectivity R1 in the range of 90% or more and a first transmissivity T1 in the range of 3% or less, while the second edge wall portion has a second reflectivity R2 in the range of 25% to 60% and a second transmissivity T2 in the range of 40% to 75%.

[0007] With this configuration having several edge wall portions presenting significantly different reflectivity and transmissivity factors, the concave reflector acts as a semi-reflective diffuser in order to obtain a uniform light emission for ambient diffuse illumination, while maintaining a high light emission efficiency for collimated task illumination.

[0008] In a functional embodiment, allowing the lighting device to switch between different lighting modes of collimated task illumination and ambient diffuse illumination, the first reflectivity R1 is 91% or more, in particular 92% or more, and more particularly 93% or more, and / or the first transmissivity T1 is 2% or less, in particular 1% or less, more particularly 0.5% or less.

[0009] Further, the second reflectivity R2 is in the range of 28% to 50%, more particularly in the range of 30% to 45%.

[0010] In a further example of the lighting device with an improved light emission distribution for ambient diffuse illumination, each concave reflector is connected at its wide end with an adjacent reflector by an interconnecting wall portion, the interconnecting wall portion having a third reflectivity R3 in the range of 25% to 60% and a third transmissivity T3 in the range of 40% to 75%.

[0011] In particular, the third reflectivity R3 is in the range of 28% to 50%, more particularly in the range of 30% to 45%.

[0012] Further, the optical element has a fourth reflectivity R4 in the range of 25% to 70% and a fourth transmissivity T4 in the range of 30% to 75%, improving the light emission in different lighting modes of collimated task illumination and ambient diffuse illumination.

[0013] In a preferred embodiment, the second reflectivity R2 is equal to the third reflectivity R3 or the second reflectivity R2 is greater than the third reflectivity R3. In the latter example, the effect obtained is a better collimation of the emitted light.

[0014] In an advantageous example, the second edge wall portion, the optical element and the interconnecting wall portion of the at least one concave reflector are formed as a single piece component. This example can be manufactured using a cost effective and fast manufacturing technique such as injection moulding, allowing the single piece component to be manufactured in high volume.

[0015] In another embodiment, the second edge wall portion, the optical element and the interconnecting wall portion of the single piece component have different thicknesses, thereby obtaining different reflection and transmission factors R2-R4 / T2-T4 for these different component portions of the reflector.

[0016] In a specific example, the second edge wall portion, the optical element and the interconnecting wall portion of the single piece component have the same thickness, such that the second reflectivity R2, the third reflectivity R3 and the fourth reflectivity R4 are equal to each other. Such a component can be made for example using thermo / vacuum forming, for example using an extruded diffuser plate.

[0017] In another example of the lighting device, the light scattering optical element comprises light scattering particles comprised in a matrix, wherein the light scattering particles are AI2O3, BaSO4, TiO2 or silicon particles, and the matrix is a polymer, such as polycarbonate, polyethylene terephthalate, polymethyl methacrylate or polyethylene.

[0018] In yet another advantageous example, wherein the lighting device can be switched between different lighting modes of collimated task lighting and ambient diffuse lighting, during operation the first light source emits a first type of light, and the further light source emits a second type of further light. The lighting device further comprises a controller configured to individually control the first light source and the further light source to be in at least a first state and a second state, wherein in the first state the first light source emits the first type of light and the further light source emits the second type of light, and in the second state the first light source emits the first type of light and the further light source does not emit light.

[0019] Further, the lighting device emits uniform illumination from all of the plurality of reflectors.

[0020] Other configurations of the lighting device provide additional diffuse illumination patterns, the edge wall of the first reflector cavity is arranged at an angle Θ with respect to the light emitting window, Θ being in the range of 20° to 70°, preferably in the range of 30° to 60°, and more preferably in the range of 40° to 50°. In particular, the second reflector cavity comprises at least one second edge wall, the at least one second edge wall being arranged at an angle γ with respect to the light emitting window, wherein γ is in the range of 20° to 70°, preferably in the range of 30° to 60°, and more preferably in the range of 40° to 50°. BRIEF DESCRIPTION OF DRAWINGS

[0021] The present invention will now be discussed with reference to the accompanying drawings, in which:

[0022] Figure 1a and Figure 1b An example of an embodiment of a lighting device according to the present disclosure is schematically illustrated;

[0023] Figure 2 (A) and Figure 2 (B) schematically illustrate details of a light embodiment of a lighting device according to the present disclosure;

[0024] Figure 3 Another example of an embodiment of a lighting device according to the present disclosure is schematically illustrated;

[0025] Figure 4 Another detail of a light embodiment of a lighting device according to the present disclosure is schematically illustrated;

[0026] Figure 5 Another example of an embodiment of a lighting device according to the present disclosure is schematically illustrated;

[0027] Figure 6a and Figure 6b Another example of an embodiment of a lighting device according to the present disclosure is schematically illustrated. DETAILED DESCRIPTION

[0028] For proper understanding of the present invention, reference will be made to the accompanying drawings, wherein:

[0029] Figure 1a A non-limiting example of an embodiment of a lighting device according to the present disclosure is schematically illustrated. Reference 10 depicts a lighting device comprising a plurality of concave reflectors 20-1; 20-2. However, in Figure 1a and 1b In the example of two concave reflectors of 10; 20, it should be noted that a large number of concave reflectors can be arranged in the form of an array or a linear configuration, depending on any structural constraints of the indoor environment in which the lighting device 10 is to be installed or depending on the type of lighting application for which the lighting device 10 is intended.

[0030] A plurality (ten, twenty or even more) of concave reflectors 20-1; 20-2; 20-n are mounted to a frame or housing 11 via which the lighting device 10 is mounted to a roof or ceiling (not shown). Each reflector 20-1; 20-2; 20-n is formed as a concave reflector comprising a cavity 25 and comprises a narrow end (side) 20-1a and a wide end (side) 20-1b and an edge wall 23-1 connecting the narrow end 20-1a and the wide end 20-1b. The plurality (ten, twenty or even more) of concave reflectors 20-1; 20-2; 20-n are aligned at their wide ends 20-1b, thereby constituting a light emitting window 24.

[0031] In addition, the plurality (ten, twenty or even more) of concave reflectors 20-1; 20-2; 20-n are interconnected at their wide ends 20-1b with adjacent reflectors by means of an interconnecting wall portion 27. Here, the lighting device exhibits an improved light emission distribution of ambient diffuse lighting.

[0032] Within each reflector cavity formed by the concave reflectors 20-1, 20-2, 20-n, a first light source 21 is arranged at or near its narrow end 20-1a. The first light source 21 can be a plurality of white, red, green and blue (WRGB) light emitting LEDs mounted on a PCB (not shown) having a light reflective surface. The PCB can be mounted to the frame 11. In this embodiment, the RGB LEDs do not render the correct color for general lighting, but are added to the white LEDs to adjust the color. The PCB and LEDs together are arranged in the reflector cavity 25 of each concave reflector 20-1; 20-2; 20-n, i.e. in this particular case, the PCB and LEDs together form part of the narrow boundary end 20-1a of the reflector cavity.

[0033] An optical element or diffuser 26 is arranged within the reflector cavity 25 between the first light source 21 and the light emitting window 24 and separates the reflector cavity 25 into a first chamber 25-1a and a second chamber 25-1b. The optical element or diffuser 26 functions as a light scattering element. The first chamber 25-1a is delimited or formed by a first edge wall portion 23-1a of the edge wall 23-1, the narrow end 20-1a (or the PCB engaging the first light source 21) and the optical element / diffuser 26, while the second chamber 25-1a is delimited by a second edge wall portion 23-1b of the edge wall 23-1, the light emitting window 24 and the optical element / diffuser 26.

[0034] In the event of energizing the first light source 21, collimated light is obtained which is collimated by the first reflector cavity 25.

[0035] Figure 1aA further light source 22 is also depicted, which is arranged outside the first reflector cavity formed by the two cavities 25-1a / 25-1b in a second reflector cavity 30 formed by the adjacent reflectors 20-1, 20-2, 20-n.

[0036] In case the further light source 22 is energized, diffuse light is obtained.

[0037] Although Figure 1a A further light source 22 is depicted in the second reflector cavity 30, but Figure 1b Embodiments of the second reflector cavity 30 depict two further light sources 22. The number of further light sources 22 in the second reflector cavity 30 formed by the adjacent reflectors 20-1, 20-2, 20-n is arbitrary, but is at least one, preferably two, but can also be three or four. Further, the further light sources 22 in the second reflector cavity 30 can be multiple white, red, green and blue (WRGB) light emitting LEDs mounted on a PCB (not shown) having a light reflective surface. Similar to the first light source 21, the PCB carrying the further light sources 22 can also be mounted to the frame 11.

[0038] Preferably, as Figure 1b is shown, the two further light sources 22 in the second reflector cavity 30 are mounted to the frame 11 such that the further light sources are arranged below the inclined edge wall 23-1 of the reflector cavity.

[0039] Implementing two light sources in the main concave reflector and in the second cavity 30 allows the lighting device to switch between different lighting modes of collimated task lighting and ambient diffuse lighting.

[0040] The boundary wall portions of the first and second cavities 25-1a and 25-1b are each made of a material having different reflectivity and transmissivity coefficients, the first edge wall portion 23-1a having a first reflectivity R1 in the range of 90% or more and a first transmissivity T1 in the range of 3% or less, and the second edge wall portion 23-1b having a second reflectivity R2 in the range of 25% to 60% and a second transmissivity T2 in the range of 40% to 75%.

[0041] In a preferred example, the second reflectivity R2 is in the range of 28% to 50%, more particularly in the range of 30% to 45%.

[0042] Preferably, the first reflectivity R1 is 91% or more, in particular 92% or more, and more particularly 93% or more, and / or the first transmissivity T1 is 2% or less, in particular 1% or less, more particularly 0.5% or less.

[0043] In all these functional embodiments, the lighting devices, particularly the first light source 21 and the additional light source 22, can be effectively switched between different lighting modes of collimated task lighting and ambient diffuse lighting.

[0044] Furthermore, at its wide end 20-1b, the interconnecting wall portion 27 of adjacent concave reflectors 20-1 and 20-2 is made of a material having a third reflectivity R3 in the range of 25% to 60% and a third transmittance T3 in the range of 40% to 75%. Preferably, the third reflectivity R3 is in the range of 28% to 50%, and more particularly in the range of 30% to 45%. This also improves light emission under different illumination modes of collimated mission illumination and ambient diffuse illumination.

[0045] The optical element or diffuser 26 is made of a material having a fourth reflectivity R4 in the range of 25% to 70% and a fourth transmittance T4 in the range of 30% to 75%.

[0046] In an alternative embodiment that results in improved collimation of the emitted light, the second reflectivity R2 is equal to the third reflectivity R3, or the second reflectivity R2 is greater than the third reflectivity R3.

[0047] Figure 2 (A) and (B) show details of an example of a lighting device according to the invention. Figure 2 (A) and Figure 2 (B) details the second edge wall portion 23-1b, the optical element or diffuser 26, and the interconnecting wall portions 27 of the adjacent concave reflectors 20-1, 20-2, 20-n, which are formed as a monolithic component. This monolithic component can be made using cost-effective and rapid manufacturing techniques such as injection molding, thereby allowing for the mass production of monolithic components.

[0048] like Figure 2 As shown in (A), the second edge wall portion 23-1b of the monolithic component, the optical element (diffuser) 26, and the interconnecting wall portion 27 have different thicknesses, denoted by d1, and by d2, the thicknesses of both the second edge wall portion 23-1b and the interconnecting wall portion 27. Preferably, d1 > d2, and increasing the thickness (e.g., by 2) will also increase the probability of reflection by 2. Although in Figure 2 In (A), the second edge wall portion 23-1b and the interconnecting wall portion 27 have the same thickness d2. However, in another example (not shown), these thicknesses of the second edge wall portion 23-1b and the interconnecting wall portion 27 may be different from each other. For example, in one combination, d2 is, for example, 2 mm and d1 is, for example, 1 mm, while in another combination, d2 is, for example, 3 mm and d1 is, for example, 2 mm.

[0049] By providing these portions of the reflector 20-1 (20-2, 20-n) with different thicknesses d1 and d2, different reflectivity and transmissivity factors R2-R3-R4 / T2-T3-T4 can be assigned to these portions of the reflector.

[0050] With this configuration of several edge wall portions with significantly different reflectivity and transmissivity factors, the concave reflector acts as a semi-reflective diffuser in order to obtain a uniform light emission for ambient diffuse illumination while maintaining a high light emission efficiency for collimated task illumination.

[0051] In the example of Fig. 1 1, the first edge wall portion 23-1 a of the single piece component, the optical element (diffuser) 26 and the interconnecting wall portion 27 have the same thickness d2, such that the second reflectivity R2, the third reflectivity R3 and the fourth reflectivity R4 are equal to each other. Such a component can for example be made using thermo / vacuum forming, for example using an extruded diffuser plate. Figure 2

[0052] To further improve the lighting properties of the lighting device, the optical element or diffuser 26 comprises light scattering particles, which are contained in a matrix. The particles are distributed substantially uniformly in the matrix forming the optical element or diffuser 26. The light scattering particles can be chosen from the group comprising AI2O3, BaSO4, TiO2or silicon particles, but are not limited thereto. In another example, the matrix containing these particles is a polymer, for example polycarbonate, polyethylene terephthalate, polymethyl methacrylate or polyethylene.

[0053] By varying the layer thickness and / or the concentration of reflective particles in any of the optical element 26, the edge wall portions 23-1 a, 23-1 b and the interconnecting wall portion 27, the reflection and light transmission properties can be varied and controlled.

[0054] In the example of a lighting device capable of switching between different lighting modes of collimated task illumination and ambient diffuse illumination, during operation, the first light source 21 emits a first type of light and the further light source (or sources) 22 emits a second type of further light. For such switching between the light modes, the lighting device 10-10'-100 further comprises a controller configured to individually control the first light source 21 and the further light source 22 to be in at least a first state and a second state, wherein in the first state the first light source 21 emits the first type of light and the further light source 22 emits the second type of light, and in the second state the first light source 21 emits the first type of light and the further light source 22 is switched off and does not emit light.

[0055] ​Note that the first type of light is emitted by the first light source 21 having a controllable light intensity L1 and the second type of light is emitted by the further light source 22 having a controllable light intensity L2. In an example, the controller controls the first light source 21 and the further light source 22 in the first state such that L1 = x (cd) and L2 = y (cd). Whereas in the second state, the controller controls the first and further lighter sources 21 and 22 such that L1 = z (cd) and L2 = 0 (cd). In those illumination states, the light intensities L1 and L2 satisfy: x < y and z > x.

[0056] In addition, the lighting device can emit a uniform illumination from all of the reflectors in said plurality of reflectors.

[0057] In Figure 3 another configuration of the lighting device is depicted in Fig. 6, which embodiment provides an additional diffuse illumination pattern. Here, the edge wall 23-1 of the first reflector cavity 25-1a / 25-1b is arranged at an angle Θ with respect to the light emitting window 24, Θ being in the range of 20° to 70°, preferably in the range of 30° to 60°, and more preferably in the range of 40° to 50°. In addition, in Figure 3 another example also depicted in Fig. 6, the second reflector cavity 30 is provided with a second edge wall 28 arranged at an angle γ with respect to the light emitting window 24 23. As Figure 3 shown, this second edge wall 28 is connected with one end to the frame 11 and with its other end to the edge wall 23-1, in particular the first edge wall portion 23-1a close to the optical element 26. For optimal illumination effects, the angle γ is in the range of 20° to 70°, preferably in the range of 30° to 60°, and more preferably in the range of 40° to 50°.

[0058] The first edge wall 23-1 is divided into a first edge wall portion 23-1a and a second edge wall portion 23-1b and each of the first edge wall portion 23-1a and the second edge wall portion 23-1b is made of a material having different first and second reflectivities R1 / R2 and different first and second transmittances T1 / T2, similarly, the second edge wall 28 of the second cavity 30 can also have at least one first wall portion and at least one second wall portion (the at least one first wall portion and the at least one second wall portion having different light transmittances T). Such a configuration also provides an additional diffuse illumination pattern.

[0059] As outlined, the number of further light sources 22 in the second reflector cavity 30 formed by the adjacent reflectors 20-1, 20-2, 20-n is arbitrary, but is at least one, preferably two, but can also be three or four. As Figure 4As shown, these additional light sources 22 can be clustered in different chambers of the concave reflectors 20-1 ; 20-2; 20-n. Figure 4 A configuration of clustered additional light sources 22 providing a diffuse illumination pattern is shown. For example, the additional light sources 22' housed in the second chamber 30 can have the same width of the interconnecting wall portion 27.

[0060] The first light sources 21 and the additional light sources 22 can be applied on a single carrier 200 (e.g. a PCB), for example a LED strip 200. The single LED carrier strip 200 can be used as a linear array of n concave reflectors 20-1 ; 20-2; 20-n. Multiple LED strips or carriers 200 can be used as a two-dimensional matrix of concave reflectors 20-1 ; 20-2; 20-n, as shown in the example. Figure 5

[0061] Figure 5 A lighting device 100 is shown, shaped as a two-dimensional matrix of concave reflectors 20-1 ; 20-2; 20-n, wherein first light sources 21 and additional light sources 22 are implemented in first and second reflector chambers 25-30, which surround four concave reflectors 20' implementing only first light sources 21 '. The complete matrix 100 is provided with side walls 29-1.

[0062] Figure 6a and 6b ( Figure 6b is Figure 6a a side view) depicts yet another example of a lighting device 1000, schematically depicted as comprising one circular fixture having a circumferential side wall 29-1 surrounding a second reflector chamber 30 and one concave reflector 20-1 forming a first reflector chamber 25 and positioned at the center of the circular fixture. The second reflector chamber 30 is provided with a plurality of additional light sources 22, which are arranged on the frame 11 in an arbitrary or regular distribution pattern (e.g. in the form of concentric circles placed around the central concave reflector 20-1 ).

[0063] ​The second reflector cavity 30 is provided with a semi-reflective diffuser element 260 made of a material having a reflectivity of 35% and a transmissivity of about 60%. To further improve the lighting properties of the lighting device 1000, the diffuser element 260 can also comprise light scattering particles. The particles are typically uniformly distributed within the diffuser element 260, preferably in the form of a matrix. The light scattering particles can be chosen from the group comprising AI2O3, BaSO4, TiO2or silicon particles, but are not limited thereto. In another example, the matrix comprising the particles is a polymer, such as polycarbonate, polyethylene terephthalate, polymethyl methacrylate or polyethylene. By varying the layer thickness and / or the concentration of reflective particles in the diffuser element 260, the reflective and light transmissive properties can be varied and controlled.

[0064] Similar to the embodiment of Figure 1a and 1b , the first light source 21 is arranged within the concave reflector cavity 25 and the diffuser 26. Upon energizing the first light source 21, collimated light is obtained which is collimated by the first reflector cavity 25.

[0065] It is noted that such single circular lighting devices 1000 are part of the present application, but are not claimed as such. It is further noted that the lighting device 1000 can comprise a plurality of circular fixtures as depicted in Figure 6a and 6b , which can be mounted in the form of a linear array or a two-dimensional matrix array, and such arrays fall within the claimed scope of the present application. When arranged in such linear array or two-dimensional matrix array form, the circumferential side wall 29-1 between two adjacent reflectors is removed, such that the second reflector cavity 30 is formed by the inclined edge wall of adjacent reflectors of the plurality of reflectors.

Claims

1. A lighting device, comprising: - Multiple concave reflectors, each reflector comprising: A narrow end, a wide end, and an inclined edge wall connecting the narrow end and the wide end form a first reflector cavity, wherein the wide end constitutes a light-emitting window. A first light source is disposed within the first reflector cavity at or near the narrow end. An optical element is disposed within the first reflector cavity between the first light source and the light-emitting window, the optical element dividing the first reflector cavity into a first chamber and a second chamber. - At least one additional light source, disposed outside the first reflector cavity and within a second reflector cavity formed by the adjacent inclined edge walls of the plurality of concave reflectors. The first light source and the at least one other light source are mounted on the same frame.

2. The lighting device according to claim 1, wherein the first chamber is defined by a first edge wall portion of the edge wall, the narrow end, and the optical element; and the second chamber is defined by a second edge wall portion of the edge wall, the light-emitting window, and the optical element, the first edge wall portion having a first reflectivity R1 in the range of 90% or greater and a first transmittance T1 in the range of 3% or less, and the second edge wall portion having a second reflectivity R2 in the range of 25% to 60% and a second transmittance T2 in the range of 40% to 75%.

3. The lighting device according to claim 2, wherein, The second reflectivity R2 is in the range of 28% to 50%.

4. The lighting device according to any one of claims 2-3, wherein each concave reflector is connected to an adjacent reflector at its wide end via an interconnecting wall portion having a third reflectivity R3 in the range of 25% to 60% and a third transmittance T3 in the range of 40% to 75%.

5. The lighting device according to claim 4, wherein, The third reflectivity R3 is in the range of 28% to 50%.

6. The lighting device according to claim 4, wherein, The optical element has a fourth reflectivity R4 in the range of 25% to 70% and a fourth transmittance T4 in the range of 30% to 75%.

7. The lighting device according to claim 4, wherein the second reflectivity R2 is equal to the third reflectivity R3, or the second reflectivity R2 is greater than the third reflectivity R3.

8. The lighting device according to claim 6, wherein, The interconnecting wall portion of at least one concave reflector, the second edge wall portion, and the optical element are formed as a single piece.

9. The lighting device of claim 8, wherein the second edge wall portion of the monolithic component, the optical element, and the interconnecting wall portion have different thicknesses.

10. The lighting device of claim 8, wherein the second edge wall portion of the monolithic component, the optical element, and the interconnecting wall portion have the same thickness, such that the second reflectivity R2, the third reflectivity R3, and the fourth reflectivity R4 are equal to each other.

11. The lighting device according to any one of claims 1-3, wherein the optical element comprises light-scattering particles contained in a matrix.

12. The lighting device according to any one of claims 1-3, wherein during operation, the first light source emits light of a first type and the other light source emits light of a second type, and wherein the lighting device further comprises a controller configured to individually control the first light source and the other light source to be in at least a first state and a second state, wherein in the first state, the first light source emits light of the first type and the other light source emits light of the second type, and in the second state, the first light source emits light of the first type and the other light source does not emit light.

13. The lighting device according to any one of claims 1-3, wherein the lighting device emits uniform illumination from all of the plurality of reflectors.

14. The lighting device according to any one of claims 1-3, wherein the edge wall of the first reflector cavity is arranged at an angle θ relative to the light-emitting window, wherein θ is in the range of 20° to 70°.

15. The lighting device according to any one of claims 1-3, wherein the second reflector cavity includes at least one second edge wall, the at least one second edge wall being arranged at an angle γ relative to the light-emitting window, wherein γ is in the range of 20° to 70°.

16. The lighting device according to claim 3, wherein, The second reflectivity R2 is in the range of 30% to 45%.

17. The lighting device according to claim 5, wherein, The third reflectivity R3 is in the range of 30% to 45%.

18. The lighting device according to claim 14, wherein θ is in the range of 30° to 60°.

19. The lighting device according to claim 14, wherein θ is in the range of 40° to 50°.

20. The lighting device according to claim 15, wherein γ is in the range of 30° to 60°.

21. The lighting device according to claim 15, wherein γ is in the range of 40° to 50°.

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