Dynamic sparkling lighting device

1. A lighting device comprising:

a light mixing chamber at least partially delimited by a first surface of a back panel carrying a plurality of light sources spatially distributed across said first surface and by a second surface of a front panel arranged to be illuminated by said light sources, said second surface comprising light transmissive regions delimiting light exit areas having a higher light transmissivity than the light transmissive regions, said light transmissive regions exhibiting isotropic luminance and light exit areas exhibiting anisotropic luminance when illuminated by said light sources, a light source is visible to an observer only when a light exit area is in alignment with a light source and an observer's eye and

a controller adapted to individually control said light sources and having a mode of operation in which the controller is adapted to vary the luminous output of a selection of said light sources as a function of time such that the isotropic luminance of the light transmissive regions is time-independent and the anisotropic luminance of at least some of the light exit areas is time-dependent during said mode of operation while the overall luminous output intensity of the plurality of light sources is kept substantially constant, in that the controller further is adapted to adjust the luminous output intensity of at least some of the light sources outside said selection as a function of the number of light sources in said selection during said mode of operation to compensate for increases in the luminous output intensity of the light sources in said selection.

2. The lighting device of claim 1 , wherein the controller is adapted to change the selection of said light sources after a period of time (t 1 , t 2 , t 3 ) and adjust a luminous output intensity of the light sources in each selection for said period of time during said mode of operation.

3. The lighting device of claim 2 , wherein said period of time (t 1 , t 2 , t 3 ) is in a range of 0.5 s to 10 s, preferably in a range of 1 s to 7 s and most preferably in a range of 1.5 s to 5 s.

4. The lighting device of claim 2 , wherein the controller is adapted to apply a non-block shaped current curve to alter the luminous output intensity of each selection of said light sources for said period of time (t 1 , t 2 , t 3 ), wherein different instances of said non-block shaped current curve corresponding to temporally neighboring selections are temporally partially overlapping.

5. The lighting device of claim 1 , wherein each selection of said light sources consists of a plurality of non-neighboring light sources.

6. The lighting device of claim 1 , wherein each selection comprises between 3-30% of the light sources of the plurality of light sources.

7. The lighting device of claim 1 , wherein the controller is adapted to adjust the luminous output intensity of light sources outside a selection that neighbour light sources in said selection to a lower luminous output intensity than light sources outside said selection that do not neighbour light sources in said selection during said mode of operation.

8. The lighting device of claim 1 , wherein the first surface is reflective.

9. The lighting device of any of claim 1 , wherein the controller further is adapted to vary the colour temperature of the luminous output of a selection of light sources as a function of time such that the colour temperature of the light transmissive regions is time-independent and the colour temperature of at least some of the light exit areas is time-dependent.

10. The lighting device of claim 9 , wherein the controller is adapted to periodically change said selection of light sources after a period of time (t 1 , t 2 , t 3 ) and adjust the colour temperature of the luminous output of the light sources in each selection for said period of time, wherein the light sources in each selection are divided in a first set of light sources producing light having a first colour temperature and a second set of light sources producing light having a second colour temperature different to the first colour temperature, preferably wherein the first set and the second set contain the same number of light sources.

11. The lighting device of claim 1 , wherein the light transmissive regions are optically diffusive and preferably have a reflectance of 30-80%.

12. The lighting device of claim 1 , wherein the light exit areas have an average diameter of at most 5 mm, preferably of at most 4 mm, more preferably of at most 3 mm.

13. The lighting device of claim 1 , wherein the light exit areas have a reflectance of less than 12%, preferably of less than 10%, more preferably the light exit areas are transparent.

14. The lighting device of claim 1 , wherein the light sources are LEDs, wherein said LEDs preferably are white light-emitting LEDs.