Artificial Skylight

Abstract

An artificial skylight comprising a light source surrounded by a protruding rim, the outermost exposed portion of the protruding rim being less than the innermost exposed portion of the protruding rim, and the outermost exposed portion of the protruding rim being non-zero.

Description

[Technical Field]

[0001] The present invention relates to the field of artificial skylights. [Background technology]

[0002] The beneficial properties of daylight for human and animal health are well documented. However, an increasing proportion of the population spends most of their time indoors. While skylights and windows offer opportunities to provide daylight to indoor environments, they can only be located at or near the perimeter of a building and typically cannot illuminate the center of a building.

[0003] One technique for addressing this problem is to utilize artificial skylights that simulate or resemble true skylight (sometimes called natural skylight) in simulating daylight in indoor environments. However, it has been recognized that if the artificial skylight has an unnatural appearance, the beneficial effects of the artificial skylight are adversely affected, such that viewers of the artificial skylight do not perceive it as being like, or similar to, true skylight. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore desirable to provide an improved artificial skylight that is perceived by viewers as more similar to a true skylight. [Means for solving the problem]

[0005] The invention is defined by the claims.

[0006] According to an example according to one aspect of the present invention, there is provided an artificial skylight comprising: a light source configured to output light as source light through a light exit window, the light source having a first thickness; and a protruding rim surrounding the light source, the protruding rim having an inner side close to the light source and having an exposed portion of a first length, an outer side farther from the light source than the inner side and having an exposed portion of a second length, and a front surface connecting the inner side and the outer side, wherein the first length is greater than the second length, and the second length is greater than 0 mm.

[0007] The proposed embodiment provides an artificial skylight in which the light source is perceived to be recessed to a greater extent on the inner side than on the outer side, which causes a viewer of the artificial skylight (if the artificial skylight is mounted on a ceiling) to perceive the light source as located beyond the ceiling, thereby more closely resembling a true skylight.

[0008] In particular, when an artificial skylight is mounted on a ceiling, a viewer perceives the overall extent of the artificial skylight as projecting outward from the ceiling a second length. If the first length is greater than the second length, the light source is perceived as recessed into the ceiling, like a real skylight, or positioned beyond the ceiling.

[0009] When mounted on a flat surface, the artificial skylight may be configured so that the inner and outer sides are substantially perpendicular to the flat surface, an approach that enhances the perception to a viewer of the artificial skylight that the light source is located above the ceiling.

[0010] In some examples, the rim is ring-shaped (circular), however, the rim may be arranged in other ring shapes and / or configurations, for example polygonal configurations such as rectangular configurations.

[0011] In some examples, the second length is less than the first thickness, which creates or facilitates a relatively high ratio between the first length and the second length, enhancing the perceived effect of the light source being located above the ceiling to a viewer of the artificial skylight.

[0012] In another example, the second length is greater than the first thickness, which results in the light source being perceived as being further back relative to the exterior surface, enhancing the perception of the light source being above the ceiling to a viewer of the artificial skylight.

[0013] The first length may be 1.2 times or more than the second length, such as 1.5 times or more than the second length, such as 2 times or more than the second length, which creates a sufficiently large perceived depth for viewers positioned further away from the artificial skylight.

[0014] The first thickness may be less than 5 mm, preferably less than 3 mm, more preferably less than 2 mm, and most preferably less than 1 mm. This embodiment provides a slim, plate-like, flat light source whose light exit window extends in an imaginary plane, reducing the noticeability of the light source as unnatural to viewers of the artificial skylight. Typically, the inner and outer sides are substantially perpendicular to the main light exit window (and therefore to the imaginary plane). Such a slim light source also allows for a larger first length to be created, enhancing the perception of the light source as being located above the ceiling, in other words, as natural light coming from above the ceiling, to viewers of the artificial skylight.

[0015] In some examples, the angle between the front surface and a plane perpendicular to the outer side surface is between 2° and 15°, preferably between 2° and 12°, and more preferably between 4° and 10°. Tilting the front surface at these angles reduces the visibility of the tilt to viewers of the artificial skylight. This, in turn, increases the perception that the light source is located above the ceiling, as the tilt reduces the likelihood that viewers will understand or perceive that the first length is greater than the second length.

[0016] Optionally, the first length is 4 mm or greater, preferably 6 mm or greater, more preferably 7 mm or greater, and most preferably 9 mm or greater, which further enhances the perception that the light source is located above the ceiling.

[0017] In some instances, the distance between the medial and lateral sides is 40 mm or greater, preferably 60 mm or greater.

[0018] In some examples, the opening of the light exit window of the light source has a width that is more than twice the distance between the inner side and the outer side, such as more than three times this distance, for example more than five times this distance.

[0019] Optionally, the exposed portion of the inner side is yellow. This coloring causes the inner side to absorb blue light and provide yellow light, more closely resembling the output of a true skylight.

[0020] In some examples, the exposed portion of the inner side surface is configured to emit or reflect additional light having a correlated color temperature that is at least 500 K lower than the correlated color temperature of the light source, which enhances the effect that the light source is natural light.

[0021] In some examples, the outer side surface is also configured to emit light having a correlated color temperature different from the correlated color temperature of the source light, which enhances the effect that the source light is natural light.

[0022] In some instances, the reflectance of the exposed portion of the outer side is lower than the reflectance of the exposed portion of the inner side, which effectively simulates a lighter color on the inner side and more closely resembles the lighting effect provided by a non-artificial skylight.

[0023] The difference in reflectance may be at least 30%, such as at least 50%.

[0024] The exposed portions of the outer side may be darker than the exposed portions of the inner side, which creates the optical effect of the inner side being lit by natural light, increasing the resemblance of the artificial skylight to natural / true skylight.

[0025] Optionally, the surface roughness of the front surface is greater than the surface roughness of the inner and / or outer side surfaces, which provides greater contrast with the side surface(s) and enhances the apparent recession of the light source relative to the surface to which the artificial skylight is attached.

[0026] In some instances, when the artificial skylight is mounted on / on a flat surface, the outer side is configured so that it is spaced from the flat surface by a gap of 2 mm or more. This provides another technique for shortening the length of the exposed portion of the outer side relative to the exposed portion of the inner side, further enhancing the optical effect of the light source being perceived as being located within / beyond the flat surface.

[0027] In some instances, the gap is 10 mm or less, for example 5 mm or less, which reduces the likelihood that a person viewing the artificial skylight will identify / perceive the gap.

[0028] In some instances, the source light has a correlated color temperature of 6000 K or higher, which makes the emitted light more closely resemble that of natural light, thereby increasing the similarity between artificial skylight and true / natural skylight.

[0029] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. [Brief explanation of the drawings]

[0030] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] Shows artificial skylight. [Figure 2] Another artificial skylight is shown. [Figure 3] 1 shows yet another artificial skylight. [Figure 4] 1 shows a bottom-up view of an artificial skylight. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will now be described with reference to the drawings.

[0032] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used to denote the same or similar parts throughout the drawings.

[0033] The present invention provides an artificial skylight, the artificial skylight including a light source surrounded by a protruding rim, the outermost exposed portion of the protruding rim being smaller than the innermost exposed portion of the protruding rim, the outermost exposed portion of the protruding rim being non-zero.

[0034] The present disclosure recognizes that by configuring the exposed portion of the outer side of the rim (which surrounds the light source) to be smaller than the inner side of the rim, an optical effect is achieved in which the light source is located within or beyond the flat surface to which the artificial skylight is attached. This effect can be exploited to configure the artificial skylight to more closely resemble a true / natural skylight.

[0035] Embodiments may be employed in any suitable environment where it is beneficial to have an artificial skylight, for example, an office, home, clinical and / or industrial environment.

[0036] 1 is a cross-sectional view of an artificial skylight 100 according to one embodiment. For clarity of illustration, the artificial skylight is shown as being attached to a flat surface 190, such as a ceiling or wall.

[0037] The artificial skylight 100 includes a light source 110 having a first thickness T. Here, the term "first thickness" is used to avoid ambiguity when referring to the thickness of the light source later (which may alternatively be referred to as "first thickness").

[0038] In the context of the present invention, the light source 110 is a module or component that emits or outputs light through a light output window 111. The light output through the light output window can be labeled as source light.

[0039] The light source may be, for example, a light guide panel (e.g., including a light guide disposed between a reflector and a diffuser) or a shallow light mixing chamber. Thus, although possible, the light source need not itself generate light, but may simply guide the generated light and exit through the light exit window 111. Preferably, the light for / of the light source is generated by one or more light-emitting elements, such as light-emitting diodes (LEDs). The light-emitting element(s) may be located within the light source itself or on one or more sides of the light source (e.g., guiding and / or mixing light for output at the light exit window).

[0040] The artificial skylight 100 also includes a protruding rim 120 that surrounds the light source. The protruding rim protrudes or extends beyond a flat surface 190 (if the skylight 100 is mounted on a flat surface) beyond the light source.

[0041] The protruding rim 120 is defined by or includes an inner side surface 121, an outer side surface 122, and a front surface 123. The inner side surface 121 is closer to the light source 110 than the outer side surface 121 (e.g., it is the surface of the protruding rim closest to the light source). The outer side surface 122 is farther from the light source 110 than the inner side surface 121. The front surface 123 connects the inner and outer side surfaces. As shown in FIG. 1 , when the artificial skylight 100 is attached to a flat surface 190, the front surface is the surface of the protruding rim farthest from the flat surface 190.

[0042] Of course, the protruding rim 120 may include a rear surface 124 joining the inner and outer sides. The rear surface 124 is closer to the flat surface 190 than the front surface when the skylight is mounted on the flat surface. In normal use, the rear surface 124 is at least partially hidden from the view of an observer of the artificial skylight.

[0043] The inner side surface 121 has an exposed portion 121A with a first length L1. The exposed portion 121A is an uncovered region or area of ​​the inner side surface, for example, a portion of the inner side surface that is not covered or obscured by the light source 110.

[0044] Additionally, the outer side surface 122 has an exposed portion with a second length L2, which is not 0 mm, i.e., is greater than 0 mm.

[0045] Generally, the exposed portion is the portion that is visible or viewable to an observer of the artificial skylight 100 when the skylight is installed on a flat surface 190 during normal operation (e.g., without the need to disassemble the skylight).

[0046] When the artificial skylight 100 is mounted on a flat surface 190, both the inner side surface 121 and the outer side surface 122 extend outward from the flat surface 190. In some preferred examples, when the artificial skylight 100 is mounted on a flat surface 190, the inner side surface 121 and the outer side surface 122 are substantially perpendicular to the flat surface 190.

[0047] The first length L1 is configured to be greater than the second length L2, and thus the first length L1 is also not zero.

[0048] This creates an optical illusion for a viewer of artificial skylight 100 that light source 110 is embedded within or located beyond flat surface 190. This causes the viewer to perceive light source 110 as light coming from a more distant source (i.e., like a true skylight) rather than originating from an artificial light source attached to a flat surface.

[0049] In particular, the proposed configuration gives a viewer of the artificial skylight a perception of depth in the interior of the artificial skylight, resembling or simulating the appearance of a natural or real skylight.

[0050] This allows the artificial skylight 100 to have a more natural appearance than existing or previous artificial skylights.

[0051] This effect increases as the difference between the first length and the second length increases.

[0052] For example, the first length L1 may be 1.2 times or more the second length L2 to create greater perceived depth for a viewer positioned further away from the artificial skylight.

[0053] As another example, the first length L1 may be 1.5 times or more the second length L2, for example, 2 times or more the second length L2. These approaches further enhance the effect provided by the difference between the first length L1 and the second length L2.

[0054] In some examples, the first length L1 is greater than the second length L2, and the first thickness T is less than the second length L2, such that (when the artificial skylight is mounted on a flat surface) the light source 110 extends outward from the flat surface to a lesser extent than the outer side 122, i.e., the light source extends as if it were recessed relative to the outer side 122.

[0055] In another example, the first length L1 is greater than the second length L2, and the first thickness T is greater than the second length, which facilitates an increased ratio of the first length to the second length, thereby facilitating a greater perceived recession of the light source.

[0056] When the skylight 100 is mounted on a flat surface 190, if there is no gap between the inner side 121 and the flat surface 190 and no gap between the outer side 122 and the flat surface 190, the difference in size between the first length and the second length will result in the front surface being inclined relative to the flat surface.

[0057] If the slope of the front surface 123 is small enough, a person viewing the artificial skylight 100 will not perceive the slope (from a distance), or will have a reduced perception of the slope. This enhances the optical effect in which the light source 110 appears to be located beyond the flat surface 190. In particular, one skilled in the art will perceive the inner side surface 121 and the outer side surface 122 as terminating at the same distance from the flat surface 190, such that an additional length of the exposed portion 121A of the inner side surface 121 compared to the exposed portion of the outer side surface 122 will be perceived to extend into the flat surface 190.

[0058] Therefore, to achieve this goal, the angle θ between the front surface 123 and the plane 130 perpendicular to the outer side surface 122 may be less than 15°, for example, less than 12°. More preferably, the angle θ is less than 10°.

[0059] To achieve a sufficient difference in length between L1 and L2 to achieve the optical effect, the angle θ is preferably 2° or greater.

[0060] Preferably, the first length L1 is equal to or less than 4 mm, for example, equal to or less than 10 mm.

[0061] In a preferred example, the distance D between the inner and outer side surfaces is 40 mm or more, preferably 60 mm or more. It will be apparent that the length of the front surface 123 depends on the distance D.

[0062] The opening of the light exit window 111 of the light source 110 may have a width W. The width W of this opening is preferably at least twice the distance D between the inner and outer side surfaces.

[0063] Table 1 shows the relationship between the value of angle θ and the perceptibility of tilt / depth.

[0064] Perceptibility of Inclination indicates how well a viewer of an artificial skylight can perceive the angle θ under normal viewing conditions. It is rated on the following categorical scale: "--" indicates Very Low Perceptibility; "-" indicates Low Perceptibility; "+" indicates Medium to High Perceptibility; and "++" indicates High to Very High Perceptibility.

[0065] Perceptibility of Depth is a measure of the effectiveness of optical effects where a light source is positioned within or beyond a flat structure relative to its mounting position on the flat structure. It is also rated on the following categorical scale: "--" indicates Very Low Perceptibility; "-" indicates Low Perceptibility; "+" indicates Medium to High Perceptibility; and "++" indicates High to Very High Perceptibility.

[0066] For the purposes of Table 1, the distance D is fixed (e.g., 50 mm), the value of L2 is fixed (e.g., 5 mm), and the value of L1 varies with changes in the angle θ. The results in Table 1 were generated under experimental conditions in which the average perceptibility of slant and depth was evaluated for a sample of observers.

[0067] TIFF2025542559000002.tif132154Table 1

[0068] Table 1 clearly shows that angles in the range of 2° to 15° provide a good balance of tilt and depth perceptibility, and angles between 4° and 10° provide a particularly advantageous balance of tilt and depth perceptibility.

[0069] Table 1 also shows that angles less than 2° do not provide the desired effect of depth perceptibility and are therefore less preferred.

[0070] Preferably, when the artificial skylight 100 is mounted on a flat surface 190, the light source 110 abuts the flat surface 190. This further reduces the perceived profile of the light source and emulates a natural or true skylight.

[0071] FIG. 2 shows an alternative artificial skylight 200 .

[0072] Similar to the artificial skylight 100 described above, the artificial skylight 200 includes a light source 210 and a protruding rim 220. The protruding rim 220 also includes an inner side surface 221, an outer side surface 222, and a front surface 223.

[0073] The artificial skylight 200 differs from the artificial skylight 100 described above in that the protruding rim 220 is configured such that, when the artificial skylight 200 is attached to the flat surface 190, the outer side surface 222 is spaced from the flat surface 190 by a gap G. Thus, a gap G is formed between the outer side surface 222 and the flat surface 190.

[0074] The presence of the gap reduces the size of the second length L2 (of the exposed portion of the outer side), which further enhances the optical effect that causes a viewer of the artificial skylight to perceive the light source 210 as being located within or beyond the flat surface to which the skylight 200 is mounted.

[0075] To a person viewing the artificial skylight 200, the appropriate size gap G is either not perceptible or the exact size of the gap is difficult to see or perceive.

[0076] In some examples, the gap G is 10 mm or less, for example, 5 mm or less, which reduces the likelihood that a person viewing the artificial skylight will identify / perceive the gap.

[0077] The gap may be larger than 2 mm, for example larger than 3 mm. This approach enhances the optical effect of the light source being within / over the flat surface 190.

[0078] Any of the features or characteristics of the artificial skylights described above may be implemented in the artificial skylight 200 .

[0079] FIG. 3 shows another artificial skylight 300 .

[0080] Similar to the artificial skylight 200 described above, the artificial skylight 300 includes a light source 310 and a protruding rim 320. The protruding rim 320 also includes an inner side surface 321, an outer side surface 322, and a front surface 323.

[0081] Artificial skylight 300 differs from the alternative artificial skylight 200 described above in that front surface 323 is not angled relative to a plane perpendicular to flat surface 190 and / or outer side surface 322. This approach utilizes only gap G to make length L1 of the exposed portion of inner side surface 321 greater than length L2 of the exposed portion of outer side surface 322.

[0082] Any feature or characteristic of any of the above-described artificial skylights may be implemented in artificial skylight 300 .

[0083] Figure 4 illustrates an artificial skylight 400 attached to a flat surface 190, according to one embodiment. In particular, Figure 4 illustrates a bottom-up view of the artificial skylight 400.

[0084] The artificial skylight 400 includes a light source 410 and a protruding rim 420. The light source 410 is generally surrounded or bounded by the protruding rim 420.

[0085] In the illustrated example, the protruding rim 420 is a ring or annulus, and the light source has a corresponding circular or cylindrical shape.

[0086] The cross-sectional shape of artificial skylight 400 may be embodied as any of the artificial skylights described above, for example, any of the artificial skylights described with reference to any of FIGS.

[0087] Further optional features of the artificial skylight, more particularly the protruding rim of the artificial skylight, are described below. These optional features can be advantageously implemented in any of the herein described embodiments of the artificial skylight.

[0088] In at least one example, the exposed portion of the inner side is yellow. This coloring causes the inner side to absorb blue light and provide yellow light, more closely resembling the output of true or natural skylight.

[0089] In some examples, the exposed portion of the inner side surface is configured to emit or reflect additional light having a correlated color temperature that is at least 500 K lower than the correlated color temperature of the light source, which enhances the effect that the light source is natural light.

[0090] In some examples, the outer side surface is also configured to emit light having a correlated color temperature different from the correlated color temperature of the source light, which enhances the effect that the source light is natural light.

[0091] Thus, the inner side and / or outer side may each include one or more light emitting devices, for example light emitting diodes, for generating and emitting light.

[0092] In some instances, the exposed portion of the outer side is darker in color or shade than the exposed portion of the inner side, and in some instances, the exposed portion of the outer side has a lower reflectivity than the exposed portion of the inner side.

[0093] Both of these approaches make the inner side appear to have enhanced lamination compared to the outer side, creating the perception that the inner side is naturally lit, increasing the similarity of the artificial skylight to natural / true skylight. This effect is enhanced if the outer and inner sides are the same color (e.g., yellow) but in different shades.

[0094] In some examples, the front surface has a color or reflectance that gradually changes from a first color / reflectance (closest to the inner side) to a second color / reflectance (closest to the outer side). If used, the first color is lighter than the second color. If used, the first reflectance is greater than the second reflectance. This also creates the perception that the side closest to the inner side is lit, for example, by natural light. This enhances the perception that the artificial skylight is a natural / real skylight, i.e., the artificial skylight resembles a natural / real skylight more closely.

[0095] In some examples, the front surface has a greater surface roughness Ra than at least the inner side surface (and optionally the outer side surface). This causes the inner side surface to reflect more light than the front surface, resulting in the inner side surface appearing to be more fully lit by natural light. This enhances the perception of the artificial skylight as a natural / real skylight, i.e., the artificial skylight's resemblance to a natural / real skylight increases.

[0096] The above-described embodiments of artificial skylights utilize light sources. Below, a number of optional but advantageous features of such light sources are described that can be implemented in any of the herein-described embodiments of artificial skylights.

[0097] In some instances, the thickness T of the light source is less than 10 mm, and more preferably less than 5 mm. This provides a slim light source that further reduces the conspicuousness or perceptibility of the light source to viewers or observers of the artificial skylight. Thus, it is preferred that the thickness T of the light source be as thin as possible.

[0098] In some examples, the light source is configured to produce light having a correlated color temperature of 6000 K or greater. More specifically, the light source is preferably configured to be capable of producing light having a CCT of 6000 K or greater. This more closely simulates natural light and brings the perceived appearance of artificial skylight closer to that of natural / true skylight.

[0099] Of course, the light source may be configured such that the correlated color temperature (CCT) of the source light can be controlled and / or changed. For example, the correlated color temperature may be variable within a predetermined range, e.g., in response to user input. A suitable example of a predetermined range is the range of 1800K to 20000K. Examples of light sources capable of emitting light within such a range are well established in the art.

[0100] The light source may have a diameter or width of 0.1 m or more, for example, 0.2 m or more. In some examples, the light source has a diameter or width of 2 m or less, for example, 1 m or less. For example, the light source may have a diameter of 0.1 m to 1 m. It has been confirmed that the optical effects of the present invention are observed for light sources having at least these sizes.

[0101] It will be understood that any of the artificial skylights described herein may include additional electronic / circuit components, for example, to power, drive, and / or control the artificial skylight's light source. Preferably, any such electronic components are at least partially housed or incorporated within the protruding rim. This technique serves to cover or hide the components so that the artificial skylight more closely resembles a natural / real skylight.

[0102] Similarly, the light source may be associated with one or more light emitting elements (e.g., one or more LEDs) that may be positioned as part of the light source itself or may be positioned external to the light source so as to receive the emitted light and redirect the received light out through a light exit window.

[0103] One or more light-emitting elements may be at least partially housed within the protruding rim, but positioned such that light is supplied to the light source for outward emission through the light-exit window. Alternatively, one or more light-emitting elements may be entirely housed within the light source itself, i.e., the light source may generate light that is emitted through the light-exit window.

[0104] The artificial skylight may include one or more mounting components for mounting the artificial skylight to a flat surface. Suitable mounting components are well known in the art and include screws, nails, clip elements, adhesives (e.g., glue), or other similar products that can mount or support the artificial skylight to a flat surface, such as a ceiling or wall.

[0105] Variations to the disclosed embodiments can be understood by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims, and can be implemented in practicing the claimed invention. 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.

[0106] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0107] It should be noted that when the term "adapted to" is used in the claims or the specification, it is intended to be equivalent to the term "configured to." It should be noted that when the term "arrangement" is used in the claims or the specification, it is intended to be equivalent to the term "system," and vice versa.

[0108] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. a light source configured to output light through a light exit window as a source light, the light source having a first thickness; a protruding rim surrounding the light source, an inner side adjacent the light source and having an exposed portion having a first length; an outer side farther from the light source than the inner side and having an exposed portion of a second length; and a front surface connecting the inner side surface and the outer side surface; a protruding rim having Including, the first length is greater than the second length, and the second length is greater than 0 mm; The angle between the front surface and a plane perpendicular to the outer side surface is between 2° and 15°, preferably between 2° and 12°.

2. 10. The artificial skylight of claim 1, wherein when attached to a flat surface, said inner side and said outer side are substantially perpendicular to said flat surface.

3. 3. The artificial skylight according to claim 1 or 2, wherein the rim is ring-shaped.

4. The artificial skylight of claim 1 , wherein the second length is less than the first thickness.

5. The artificial skylight of claim 1 , wherein the second length is greater than the first thickness.

6. 6. The artificial skylight according to claim 1, wherein the first length is at least 1.5 times the second length.

7. 7. The artificial skylight of claim 1, wherein the first thickness is less than 5 mm.

8. 8. The artificial skylight according to claim 1, wherein the first length is 4 mm or more.

9. 9. The artificial skylight according to claim 1, wherein the distance between the inner side surface and the outer side surface is 40 mm or more, and the opening of the light source light exit window has a width that is at least twice the distance between the inner side surface and the outer side surface.

10. 10. The artificial skylight of claim 1, wherein the exposed portion of the inner side surface is configured to emit or reflect additional light that is (i) yellow and / or (ii) has a correlated color temperature that is at least 500 K lower than the correlated color temperature of the source light.

11. The artificial skylight according to claim 1 , wherein the reflectance of the exposed portion of the outer side surface is lower than the reflectance of the exposed portion of the inner side surface.

12. 12. The artificial skylight of claim 1, wherein the exposed portion of the outer side surface has a darker color than the exposed portion of the inner side surface.

13. 13. The artificial skylight according to any one of claims 1 to 12, wherein the surface roughness of the front surface is greater than the surface roughness of the inner side surface and / or the outer side surface.

14. 14. The artificial skylight of any one of claims 1 to 13, wherein when mounted on a flat surface, the outer side is spaced from the flat surface by a gap of 2 mm or more, optionally the gap is 10 mm or less.

15. 15. The artificial skylight according to claim 1, wherein the light source light has a correlated color temperature of 6000K or higher.

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