Artificial skylight

Abstract

A skylight comprising a horizontal sky section (21) configured to emit light resembling a sky visible through a window, and at least one vertical sun section (22) forming part of a vertical frame extending around the periphery of the sky section (21), each sun section (22) being configured to emit light resembling sunlight reflected from a surface. The sky section (21) includes a mixing chamber (23) having a horizontal diffusing exit window (24) and a plurality of first solid state light sources (27) arranged to illuminate the mixing chamber (23). Each sun section (22) includes a vertical lightguide (31) with a reflective backing (32) arranged on an outwards facing side and a diffusor (33) arranged on an inwards facing side, and a plurality of second solid state light sources (35) arranged to couple light into the light guide (31).

Description

[0001] Artificial skylight

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an artificial skylight providing an appearance of a sun-illuminated sky-light. The skylight function includes a light emitting panel for emitting light resembling the sky, and a light emitting frame extending perpendicular to the light emitting panel and for emitting light resembling sunlight reflected by a surface. The skylight may be integrated in a luminaire.

[0004] BACKGROUND OF THE INVENTION

[0005] In recent years, artificial skylights have been developed that simulate the effect of a blue sky and sun shining in through a ceiling window. Such artificial skylights typically include a horizontal sky section for emitting light resembling the sky visible through a window, and a vertical frame around the periphery of the sky section, where one or several of the sides of the frame are configured to emit light resembling sunlight reflected from a surface.

[0006] In existing designs, the sky section has a horizontal light exit window configured to emit blue and white light resembling the sky to create the impression of a window facing the sky. The frame includes one or several sun sections for emitting white light resembling reflected sunlight to create the impression of sun-lit window edges. The sun section further includes one or several shade sections, which together with the sun sections form the frame around the sky section. In one example, the sky section is rectangular, and the sun section is formed by two sun sections and two shade sections forming a rectangular frame or rim.

[0007] The sky section is covered (on the side facing the room) by a transparent and at least partially reflective panel, e.g. of polycarbonate or glass. The partially reflective cover serves to provide a reflection of the light emitting sun panels, further improving the illusion of a window facing the sky.

[0008] There is a constant effort to reduce the cost of artificial skylights, without compromising the desired visual effect. Prior right WO2023 / 222498A1 discloses an artificial skylight comprising a first light emitting surface configured to resemble the sky and a rim circumscribing the first light emitting surface and configured to resemble sun light. The first light emitting surface is arranged at an angle relative to the rim.

[0009] EP3978796A1 discloses an illumination device including an illumination panel and a side wall around the illumination panel. The side wall includes triangular lightemitting regions that simulates a sunny part and a shady part.

[0010] SUMMARY OF THE INVENTION

[0011] Based on the above, it is an object of the present invention to reduce the cost of an artificial skylight.

[0012] According to a first aspect of the invention, this and other objects are achieved by an artificial skylight having a first light emitting surface and a light transmissive panel arranged downstream from the first light emitting surface, wherein the first light emitting surface is arranged to emit first light for resembling the sky, and wherein part of the first light is transmitted through the light transmissive panel before exiting through a light exit window, and another part of the first light propagates next to the light transmissive panel before exiting through a light exit window. The artificial skylight further includes a rim extending in a perpendicular direction from the light exit window and connecting the first light emitting surface and the light transmissive panel, wherein at least a portion of the rim comprises a second light emitting surface which is configured to emit second light for resembling sunlight through the light exit window.

[0013] As the light transmissive panel covers only a portion of the first light emitting surface, part of the first light will not pass through the transmissive panel, and will exit the light exit window directly.

[0014] By “covers only a portion of the light emitting surface” is intended that the transmissive panel is arranged such that first light emitted from one portion of the light emitting surface will pass through the transmissive panel, while first light emitted from another portion will not pass through the light transmissive panel.

[0015] With this design, the transmissive panel may be made smaller, i.e. smaller than the light emitting surface, for example in a range of 20% to 80% smaller than the light emitting surface, thereby reducing cost.

[0016] Up to date, the illusion of a skylight was considered to require a partially reflective surface, where the second light could be reflected. The invention is based on the surprising realization that the illusion will stay intact even if only a portion of the light emitting surface is covered by the (partially) reflective panel. Another advantageous effect of the partial panel is that the skylight is perceived as being partially open.

[0017] The rim is preferably circumferential, i.e. it may extend around the first light emitting surface.

[0018] The light transmissive panel may be provided with a (partially) reflective coating. Alternatively, it may be transparent, with a smooth major surface. The light transmissive panel and its smooth major surface preferably are straight / flat (i.e. not curved or bend). A transparent panel with smooth surfaces may provide (Fresnel) reflection of the rim which is sufficient for further enhancing the realistic skylight effect, in particular when it is flat. The smooth major surface preferably faces the light exit window.

[0019] In embodiments, the light transmissive panel covers 20% - 80%, 30% - 70% or 40% - 60% of the light emitting surface, for example around one quarter, one third, half, two thirds, or three quarters of the light emitting surface.

[0020] First light from the “non-covered” portion of the light emitting surface may be emitted without being transmitted though the light transmissive panel. This non-covered portion may be in a range from 20% to 80% of the light emitting surface.

[0021] The light transmissive panel preferably extends from a first side of the rim to a second side of the rim, the second side being opposite to the first side. For example, it may extend in a straight line from one side to the opposite side.

[0022] In embodiments, the first light is blue light or white light having a first correlated color temperature, the second light is white light having a second correlated color temperature. In case the first light is white light having the first correlated color temperature, then the second correlated color temperature is lower than the first correlated color temperature. For example the difference may be at least lOOOK or at least 2000K. The first correlated color temperature may be at least 5000K. The first correlated color temperature may be at most 5000K. Combined light i.e. the first light and the second light may have a combined correlated color temperature in a range from 2700K to 5000K. The combined light may have a color rendering index of at least 80 or at least 85.

[0023] In some embodiments, the rim (and thus the light exit window) is substantially rectangular and comprises a first side, a second side, a third side and a fourth side. The light transmissive panel may then extend from the first side to the second, opposite, side, and abut the third side and be arranged at a distance from the fourth side. In case of a rectangular rim, the light transmissive panel may also be rectangular. In some embodiments, the second light emitting surface constitutes 25%-75% of the rim. The remaining part of the rim may be constituted by non-light-emitting shade section(s). The combination of light surfaces and non-light-emitting shade section(s) improves the perception of a skylight facing the sun.

[0024] In order to further improve the desired optical effect, the light transmissive panel may border (i.e. be arranged in connection to) the second light emitting surface.

[0025] In some embodiments, the light transmissive panel is arranged parallel to the first light emitting surface and separated from the first light emitting surface by a distance D, wherein D is in the range 1 - 30 mm. If, in such an arrangement, the transparent panel has a smooth and flat surface, then apparent (Fresnel) reflection of the rim may occur, which in case of the light transmissive panel being arranged parallel to the first light emitting surface, provides a further enhanced, realistic skylight effect. In other embodiments, the light transmissive panel is arranged non-parallel to the first light emitting surface.

[0026] The artificial skylight may further comprise a further light transmissive panel arranged downstream the first light emitting surface, wherein the further light transmissive panel is arranged adjacent to or to partly overlap the light transmissive panel. The further light transmissive panel comprises a major surface, and preferably said major surface of the further light transmissive panel is arranged parallel to the (smooth / flat) surface of the light transmissive panel. The combination of the light transmissive panel and the further light transmissive panel may only partly cover the first light emitting surface. Alternatively, the combination of the light transmissive panel and the further light transmissive panel covers the entire first light emitting surface.

[0027] The light transmissive panel and / or the further light transmissive panel may be movable with respect to the rim. Such an arrangement will allow adjusting how large portion of the first light emitting surface that is covered by the combination of the light transmissive panel and the further light transmissive panel.

[0028] The light transmissive panel and / or the further light transmissive panel may be a side-lit light guide, wherein a major surface of the light transmissive panel and / or a major surface of the further light transmissive panel is provided with an outcoupling structure for outcoupling third light emitted by a third light source.

[0029] The first light emitting surface may be formed by a diffusive light exit window of a mixing chamber, and comprise a plurality of first solid state light sources arranged to illuminate the mixing chamber. Further, the rim may include at least one lightguide with a reflective backing arranged on an outward facing side and a diffusor arranged on an inwards facing side, and a plurality of second solid state light sources arranged to couple light into the light guide.

[0030] The artificial skylight may comprise a controller configured to individually control the first light, the second light, and optionally the third light.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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 present invention.

[0033] Fig. l is a schematic perspective view of an artificial skylight according to an embodiment of the present invention.

[0034] Fig. 2 shows a portion of the artificial skylight in Fig. 1, in operation.

[0035] Fig. 3 is a cross section of a part of an example artificial skylight.

[0036] Fig. 4 is a schematic perspective view of an artificial skylight according to a further embodiment of the present invention.

[0037] Fig. 5 is a perspective view of a skylight luminaire including an artificial skylight.

[0038] DETAILED DESCRIPTION

[0039] The terms “horizontal”, “vertical”, “upper”, “lower", et. are here used to indicate orientation when the skylight is mounted in a horizontal ceiling. It is noted that the artificial skylight may be mounted with a different orientation, and this choice of references is not intended to have any limiting effect on the disclosure.

[0040] The words “upstream” and “downstream” are used with reference to a propagation direction of light emission. So, for example, upstream the light exit window of the sky section means above the exit window when the artificial skylight is mounted horizontally.

[0041] The artificial skylight 1 in figure 1 comprises a horizontal sky section 2 having a generally flat light emitting surface 3 configured to emit first light LI resembling a sky visible through a window. The skylight 1 further comprises a frame or rim 4 which is here substantially perpendicular to and extends around the periphery of the light emitting surface 3. At least one of the sides of the rim 4 includes is formed by a second light emitting surface 5, here referred to as a “sun section”, configured to emit second light L2 resembling sunlight reflected from a surface. The rim 4 may also include at least one non-illuminated shade section 6, representing shaded sides of the frame 4. As shown in figure 2, a triangular portion 6a of the non-illuminated shade section 6 may extend into the side of the sun section 5. Such a triangular shade portion 6a will serve to provide an impression of shade.

[0042] The space inside the frame 4 may be referred to as a light exit window 8 of the artificial skylight. A transmissive and partially reflective panel 7 is arranged downstream the light emitting surface 3 and covers only a portion 3a of the light emitting surface 3. The panel 7 may be transparent. It may also have smooth major surfaces.

[0043] In some embodiments, the panel 7 is separated from the light emitting surface 3 by a distance D, e.g. in the order of millimeters or a few centimeters. In this case the rim 4 may extend from panel 7, i.e. also the rim 4 may be separated from the light emitting surface 3. The panel 7 may be parallel with the surface 3, such that the distance D is constant. Alternatively, the panel 7 is slightly tilted with respect to the surface 3, in which case the distance D varies.

[0044] Figure 2 shows the artificial skylight 1 in figure 1 in operation. The light emitting panel 3 emits LI light resembling the sky, while sun section 5 emits light L2 resembling sunlight reflected from a window side. Light emitted from the portion 3a will be transmitted through the transmissive panel 7, while light emitted from the uncovered part of the light emitting surface 3 will not be transmitted through the panel 7. At the same time, the light transmissive panel 7 will provide a reflection of the sun section 5, even further improving the illusion of a skylight window. The reflection may be Fresnel reflection.

[0045] The first light LI and the second light L2 may have different correlated color temperature (CCT). For example, the difference in CCT may be more than 2000K.

[0046] Figure 3 shows one embodiment of a sky section 2 and sun section 5, serving only as an example. Many other designs are possible to emit the first light LI and second light L2. The sky section 2 here comprises a mixing chamber 23 having a diffusing light exit window 24, in turn partly covered by a transparent panel 7. The diffusing exit window 24 may be a polymer plastic sheet, e.g. 1 mm thick. The transparent panel 7 may be a polycarbonate pane, e.g. 1-2 mm thick. The mixing chamber 23 is configured to mix light emitted by a set of LEDs 27, mounted in the upper part of the mixing chamber 23, typically LEDs configured to emit white and blue light. The sun section 5 comprises a lightguide panel 31, provided with an outwardly facing reflective backing 32 and an inwardly facing diffusor 33. Light is coupled into the lightguide by a set of LEDs 35 such as warm white LEDs and cold white LEDs (only one LED 35 is shown in figure 5 due to the cross-section view). The surface of the lightguide 32 facing the diffusing panel 33 can be provided with suitable outcoupling structures, such as dents, to promote outcoupling of light. The diffusor 33 can be made of suitable polymer plastic sheet, e.g. around 1 mm thick.

[0047] The embodiment in figure 3 also includes a set of further LEDs 36, configured to in-couple light into the transparent panel 7, serving as a light guide. The panel 7 is further provided with suitable outcoupling structures, such that in-coupled light may be emitted as third light L3. This allows a further variation of the appearance of the skylight 1.

[0048] Turning to figure 4, a further embodiment of an artificial skylight 101 is shown. The skylight 101 in figure 4 is similar to the skylight 1 in figure 1, but additionally includes a further partially reflective and transmissive panel 107, here partly overlapping the panel 7. As shown, the further light transmissive panel 107 is arranged parallel to the light transmissive panel 7. The further panel 107 may have different properties compared to the panel 7 thereby improving the versatility of the skylight 101. The further panel 107 may also be a side-lit light guide, as discussed above with reference to figure 3.

[0049] In some embodiments, at least one of the panel 7 and further panel 107 may be displaceable with respect to the rim 4, and to each other. For example, the panel 107 may be slidable in its plane, as indicated by arrow A.

[0050] In the illustrated case, the combination of the light transmissive panel 7 and the further light transmissive panel 107 only partly covers the first light emitting surface 3. In other words, one part of the light emitting surface 3 is uncovered by the transmissive panels 7, 107.

[0051] Figure 5 shows a skylight luminaire 10, including an artificial skylight 1 and a luminaire 11 surrounding the skylight 1. The luminaire 11 is provided with one or more lighting elements (not shown), typically for providing white office-type illumination. For example, the luminaire 11 can be provided with solid state lighting elements covered by a diffuser which spreads the light more evenly over the lower surface of the luminaire 11. In this way, the luminaire 11 cooperates with the recessed skylight 1 to provide indoor light that appears natural, as if it originates from a sunny outside environment shining through a skylight window.

[0052] A controller (not shown) may be connected to the artificial skylight and be configured to individually control the first light, LI, the second light, L2, and optionally the third light, L3. Such control may enable user interaction with the skylight, e.g. for achieving an illusion of a specific “time-of-day”.

[0053] 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, different dimensions and shapes may be implemented in the light emitting surface 3 and the transmissive panel 7.

Claims

CLAIMS:

1. An artificial skylight (1) configured to provide artificial skylight light, said artificial skylight comprising: a first light emitting surface (3) and a light transmissive panel (7) arranged downstream from said first light emitting surface (3), wherein the first light emitting surface (3) is arranged to emit first light, LI, for resembling the sky, so that part of the first light, LI, is transmitted through the light transmissive panel before exiting through a light exit window (8) and another part of the first light, LI, propagates next to the light transmissive panel before exiting through a light exit window (8); a rim (4) extending in a perpendicular direction from the light exit window (8) and connecting said first light emitting surface (3) and the light transmissive panel (7), wherein at least a portion of said rim (4) comprises a second light emitting surface (5) which is configured to emit through said light exit window (8) second light, L2, for resembling sunlight; wherein said light transmissive panel (7) covers only a portion (3a) of the first light emitting surface (3), and wherein the light transmissive panel (7) is arranged parallel to the first light emitting surface (3) and separated from the first light emitting surface (3) by a distance D, wherein D is in the range 1 - 30 mm.

2. The artificial skylight according to claim 1, wherein the light transmissive panel (7) covers 20% - 80% of the first light emitting surface (3).

3. The artificial skylight according to any one of the preceding claims, wherein the light transmissive panel extends from a first side of the rim to a second side of the rim, the second side being opposite to the first side.

4. The artificial skylight according to claim 3, wherein said rim (4) is substantially rectangular and comprises the first side, the second side, a third side and afourth side, and wherein the light transmissive panel abuts the third side and is arranged at a distance from the fourth side.

5. The artificial skylight according to claim 4, wherein said second light emitting surface (5) is formed by at least two adjacent sides of said first, second, third and fourth sides.

6. The artificial skylight according to any one of the preceding claims, wherein the light transmissive panel (7) is transparent and has smooth major surfaces.

7. The artificial skylight according to any one of the preceding claims, wherein the portion (3a) is rectangular.

8. The artificial skylight according to any one of the preceding claims, wherein the second light emitting surface (5) borders the light transmissive panel (7).

9. The artificial skylight according to any one of the preceding claims, wherein the rim (4) extends in a perpendicular direction from the first light emitting surface (3).

10. The artificial skylight according to any one of the preceding claims, further comprising a further light transmissive panel (107) arranged downstream the first light emitting surface (3), wherein the further light transmissive panel (107) is arranged adjacent to or partly overlapping the light transmissive panel (7), and preferably such that a combination of the light transmissive panel (7) and the further light transmissive panel (107) only partly covers the first light emitting surface (3).

11. The artificial skylight according to claim 10, wherein the further light transmissive panel (107) is arranged parallel to the light transmissive panel (7).

12. The artificial skylight according to any one of the preceding claims, wherein said light transmissive panel (7) and / or said further light transmissive panel (107) is movable with respect to said rim (4).

13. The artificial skylight according to any one of the preceding claims, wherein said light transmissive panel (7) and / or said further light transmissive panel (107) is a side-lit light guide, wherein a major surface of the light transmissive panel (7) and / or a major surface of said further light transmissive panel (107) is provided with an outcoupling structure for outcoupling third light, L3.

14. The artificial skylight in any one of the preceding claims, wherein said first light emitting surface (3) is formed by a diffusive light exit window (24) of a mixing chamber (23), and comprises a plurality of first solid state light sources (27) arranged to illuminate the mixing chamber (23), and / or wherein said rim (4) includes at least one lightguide (31) with a reflective backing (32) arranged on an outwards facing side and a diffusor (33) arranged on an inwards facing side, and a plurality of second solid state light sources (35) arranged to couple light into the light guide (31).

15. The artificial skylight according to any one of the preceding claims, further comprising a controller configured to individually control the first light, LI, the second light, L2, and optionally the third light, L3.

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