WO2012052937A1

WO2012052937A1 - Arrangement for a low loss luminaire

Info

Publication number: WO2012052937A1
Application number: PCT/IB2011/054654
Authority: WO
Inventors: Hendrikus Hubertus Petrus Gommans; Eduard Johannes Meijer; Michel Cornelis Josephus Marie Vissenberg; Fetze Pijlman; Wilhelmus Petrus Adrianus Johannus Michiels; Jochen Renaat Van Gheluwe
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-10-22
Filing date: 2011-10-19
Publication date: 2012-04-26

Abstract

The disclosed embodiments relate to an arrangement (1) for a low loss luminaire and in particular to such an arrangement in a system comprising a daylight tube system. Light provided by an aperture (4) is received by a re-directional structure (2). The re- directional structure is arranged at a distance L1 from the aperture (4). The light extraction efficiency from the aperture (4) is thus enhanced in comparison to known techniques.

Description

Arrangement for a low loss luminaire

FIELD OF THE INVENTION

The present invention relates in general to a lighting system and in particular to an arrangement for a low loss luminaire in such a system comprising a daylight light tube. BACKGROUND OF THE INVENTION

There is a lot of daylight available during the day which currently is hardly used in windowless spaces. In professional buildings in areas like washrooms, halls and stairs often artificial light is constantly burning during working hours.

Additionally it is often desired by people to have natural light wherever possible. Also, having more natural light available inter alia in hospitals is known to be welcomed by personnel as well as patients.

Several options are known where daylight is put to more effective use, such as light tubes used for transporting daylight into a building. The light tube typically has an inlet for receiving daylight at the roof of a building. The received daylight is transmitted through a pipe of the light tube to an outlet inside the building so as to illuminate the interior of the building. The resulting indoor light spot may have a shape which is dependent on the geometry of the inner light tube surface and also on the variation in sun position over a day. Thereby the diameter of the indoor light spot changes over the course of the day. To mask this dynamical spot variation and the light tube exit is commonly fitted with a diffuser placed at the outlet of the light tube.

SUMMARY OF THE INVENTION

The inventors of the disclosed embodiments have identified drawbacks associated with the techniques described above. A diffuser placed at the outlet of the light tube results in significant backscatter into the light tube and hence reduced light extraction for the area to be illuminated. Furthermore, if artificial light is integrated in a light tube system to for example compensate for the absence in daylight during for example evenings or other situations where daylight is scarce, the arrangement suffers from further drawbacks such as reduced efficiency due to backscattering of the artificial light at the diffusing plate. Also, typical artificial light integration could block the daylight guiding through the light tube and as a result reduce the light extraction even further.

It is therefore an object of the present invention to overcome these problems, and to provide an improved lighting system that provides light in an efficient way with low losses.

The inventors of the disclosed embodiments have discovered that the positioning of a re-directional structure at the light outlet of the light tube may affect the overall illumination properties (such as the daylight efficiency gain) of the light tube.

Generally, the above objectives are achieved by an arrangement for a low loss luminaire according to the attached independent claim.

According to a first aspect of the invention, the above mentioned and other objects are achieved by an arrangement comprising a re-directional structure arranged to receive light from an aperture in a first surface, the aperture having a diameter Dl and being oriented towards the re-directional structure, wherein the re-directional structure is arranged to be positioned at a distance LI from the aperture, the distance LI being larger than the diameter Dl of the aperture, wherein the re-directional structure is arranged to transmit light towards a second surface, and wherein the re-directional structure is arranged to reflect light, such that light reflected by the re-directional structure is reflected towards the first surface. The second surface is a surface to be illuminated by means of the arrangement.

The aperture could be of various shapes such as polygon or circular. By diameter of the aperture in the case the aperture is being shaped as a polygon is meant the maximum diagonal distance between two corners of the polygon.

Advantageously, the distance LI is at least twice as large as the diameter Dl of the aperture. Furthermore it is advantageously that the ratio between the diameter Dl of the aperture and a diameter D2 of the re-directional structure is equal to or smaller than 1.

The arrangement may further comprise sidewalls attached to the re-directional structure and extending towards the first surface. The arrangement may also comprise spacing means for spacing the re-directional structure at the distance LI from the aperture. The spacing means may be used to suspend the re-directional structure at the distance LI from the aperture. The spacing means may be defined by the sidewalls. Thereby the sidewalls may at least partly suspend the re-directional structure from the aperture.

The re-directional structure and/or the sidwalls may be a semi-transparent diffuser. Advantageously, the diffuser and/or the sidwalls could have the characteristics of being both transmissive and reflective. Thus, the arrangement could provide illumination at both the first surface surrounding the aperture and the second surface which typically is opposite to the first surface. For example, if the first surface is a ceiling of a room, the second surface could be a floor.

The re-directional structure and/or the sidwalls may be defined by a plurality of lamellas. The lamellas may not be made from a semi-transparent material which may reduce the manufacturing costs for the re-directional structure.

The arrangement could advantageously further comprise a diffusing plate which is arranged between the plurality of lamellas and the aperture. This may reduce the dynamical spot variation.

According to further embodiments, the arrangement may comprise at least one light source. The at least one light source could for example be located between the re-directional structure and the aperture. The at least one light source provide artificial light which could be used in combination with the light provided at the aperture. Since the extraction of daylight could vary greatly the artificial light is an advantageous complement to the arrangement, especially during for example evenings or other situations where daylight is scarce.

The arrangement may comprise a micro lens optical plate. The micro lens optical plate may be arranged to receive light transmitted by the re-directional structure. The micro lens optical plate could furthermore shape the provided light beams into a focused beam of light. Thereby a functional light may be provided.

The least one light source mentioned above may be located between the re-directional structure and the micro lens optical plate. The light sources may thereby be concealed behind the micro lens optical plate.

In embodiments where the arrangement comprises at least one light source, the at least one light source could furthermore be electrically coupled to sensing circuitry and/or control circuitry. This enables the at least one light source to be tuneable so that for example a dimmed lighting may be achieved. Furthermore, such an arrangement may create resilience against or enhancement of the daylight dynamics.

According to embodiments the arrangement may further comprise a light tube having an entry aperture arranged to receive light and an exit aperture arranged to emit light. The exit aperture may define the aperture of the first surface according to the first aspect of the invention. Moreover, the arrangement could further comprise a collimator, such as a compound parabolic concentrator, arranged at the exit aperture of the light tube. According to a second aspect of the invention, the above object and other objects are achieved by a luminaire comprising an arrangement as disclosed above.

According to a third aspect of the invention, the above object and other objects are achieved by a lighting control system comprising at least one arrangement as disclosed above.

It is noted that the invention relates to all possible combinations of features recited in the claims. Thus, all features and advantages of the first aspect likewise apply to the second and third aspects, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs, la-b are perspective views of an arrangement according to embodiments of the invention.

Fig. 2 is a perspective view of an arrangement according to an embodiment of the invention where the arrangement is a part of a light tube system.

Figs. 3a-c are side views of arrangements according to embodiments of the invention.

Fig. 4 to Fig. 6 are side views of different arrangements of light tubes.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled addressee. Like reference characters refer to like elements throughout.

The terms "upstream" and "downstream" as used herein relate to an arrangement of items or features relative to the propagation of light from a light source. Relative to a first position within a beam of light from the light source, a second position in the beam of light closer to the light source is "upstream", and a third position within the beam of light further away from the light source is "downstream".

The term "light axis" as used herein relate to an axis in which direction light is propagated downstream of a light source, e.g. from the entry aperture of a light tube to the exit aperture of said light tube. Thus, by for example "the light axis relative the light tube" is meant a light axis directed downstream of the light tube exit.

The invention is based upon the realization that the positioning of a

re-directional structure downstream of the light tube may improve the overall illumination properties (such as the daylight efficiency gain) of the light tube.

Fig. la illustrates an arrangement 1 for a low loss luminaire. The arrangement 1 comprises a re-directional structure 2. The re-directional structure 2 is arranged to receive a light beam 3 from an aperture 4. The aperture 4 is in general surrounded by a first surface 5. The first surface 5 could for example be (part of) a ceiling, a wall or a floor depending on the geometrical orientation, i.e. where in a room the arrangement 1 is mounted. The aperture 4 is oriented towards the re-directional structure 2. The re-directional structure 2 is further arranged to transmit light towards a second surface (not explicitly illustrated). The second surface may be a surface which is preferred to be illuminated. The second surface could for example be (part of) a ceiling, a wall or a f oor. However, if the first surface 5 is (part of) a ceiling, the second surface is not (part of) the same ceiling but may instead be (part of) a floor. The corresponding relation likewise apply to an arrangement 1 where the first surface 5 is (part of) a floor, wherein the second surface may then be (part of) a ceiling. Both the first surface 5 and the second surface may be (part of) a wall.

The re-directional structure 2 is arranged to reflect a light beam 3, such that the light beam 3 reflected by the re-directional structure 2 is reflected towards the first surface 5 surrounding the aperture 4. The arrangement 1 may thereby enable for lighting of both the first surface 5 and the second surface. The design of the arrangement 1 is thus such that very little of the generated light is lost (e.g. by being backscattered towards the aperture 4). Most light is used in either of two projections, as illustrated by the arrows of the light beam 3: transmission through the re-directional structure 2 towards the second surface or reflection by the re-directional structure 2 towards the first surface 5 surrounding the light tube exit 4 (to be further reflected towards the second surface).

The re-directional structure 2 has a diameter D2 and is located at a distance LI from the aperture 4. The aperture 4 has a diameter Dl . To increase the daylight efficiency the distance LI is preferably larger than the diameter Dl of the aperture 4. Thereby the solid angle subtended by the aperture 4 is reduced which lowers the probability for backscatter (i.e. that the reflected light beam 3 is reflected upstream the aperture 4). Accordingly, the optical loss in comparison to known techniques may be reduced whilst maintaining a regular light beam pattern irrespective the time of day. It has for example been shown by the inventors that an increase of 59 % to 88 % light extraction efficiency is obtained in case the distance between the light tube exit 4 and the re-directional structure 2 is about 0.5 m. These considerations will be further described at the end of the detailed description of the invention with reference to Figs. 5 to 7.

Advantageously, the distance LI is at least twice as large as the diameter Dl of the aperture 4.

In one embodiment the re-directional structure could be placed in a room where the first surface is constituted by the ceiling of the room and the second surface is constituted by the floor of the room. A typically diameter Dl could be 40 cm. Thus it may in such a case be advantageous if the distance LI is at least 80 cm. However, in order to avoid that the re-directional structure 2 forms an obstacle in the room, the value of the distance LI should in practical circumstances not be too high. The optimum of the distance LI could therefore be determined also by considering the height HI of the room, i.e. the distance between the ceiling and the floor of the room. In other words, the value of the distance LI could be chosen as to be preferably at least 80 cm but not so high that the re-directional structure 2 is in somebody's way {inter alia such that the distance H2 between the re- directional structure 2 and the floor is, for example, at least 200 cm). Thus, LI may be determined as LI > 2 - Dl, as long as Hl - LI > H2, and

LI = HI - H2, otherwise.

In practical circumstances HI is typically between about 250 cm and 350 cm and H2 is typically between about 200 cm and 250 cm.

Furthermore, it is also advantageously that the ratio between the diameter Dl of the aperture 4 and the diameter D2 of the re-directional structure 2 is equal to or smaller than one. In other words the diameter D2 is advantageously larger than the diameter Dl . This may further enhance the light extraction efficiency. The larger the diameter D2 is compared to the diameter Dl the more efficient the adjustment of the light may be.

The re-directional structure 2 is distanced from the aperture 4 by spacing means 6. The spacing means 6 may be for example a string or a pane. The spacing means 6 could be made of a transparent material as well as a non-transparent material as well as a semi-transparent material. The choice of material is not limited to any specific and could be for example metal, wood, glass, fabric or plastics. The spacing means 6 could consist of a single attachment such as a single pane or string or it may be formed by a plurality of attachments such as multiple panes or strings or a combination of strings and panes. The pane or panes may thus define one or more sidewalls 15 which are attached to the re-directional structure.

Fig. lb illustrates an arrangement 1 comprising a re-directional structure 2 with spacing means 6 defining sidewalls. The one or more sidewalls may extend from the re-directional structure towards the first surface. The re-directional structure 2 and the one or more sidewalls 15 may thereby form sides of a so-called light box 16. The light box 16 may have the shape of a rectangular parallelepiped. Alternatively the light box may have the shape of a cylinder. According to one embodiment the one or more sidewalls extend along the entire distance LI towards the first surface.

As noted above the diameter D2 is advantageously larger than the diameter Dl . Preferably the diameter D2 of the re-directional structure 2 (and hence of the light box 16) is at least 50% larger than the diameter Dl of the aperture 4. In this case the one or more sidewalls 15 of the light box 16 may be inclined from the re-directional structure 2 towards the aperture 4, thus forming a pyramid shaped light box 16.

The inner surfaces of the one or more sidewalls 15 (i.e. the surface facing the interior of the defined light box 16) may be coated with a light reflective layer so as to form a reflector for reflecting incoming beams of light 3. Alternatively the one or more sidewalls 15 may comprise one or more semi-transparent diffusers. The semi-transparent diffuser may have the same properties as the semi-transparent diffuser of the re-directional structure 2. Yet alternatively the one or more sidewalls 15 may comprise a plurality of lamellas. The plurality of lamellas may have the same properties as the plurality of lamellas of the re-directional structure 2. The first surface 5 may thus be defined by an inner surface of the light box itself.

Fig. 2 illustrates an arrangement 1 similar to the one illustrated in Fig. la. The arrangement may be (part of) a light tube system. A typically known light tube system consists of a light tube 7 comprising an light tube entry 8 and light tube exit 4. The light tube entry 8 is arranged to receive a light beam 3 and the light tube exit 4 is arranged to emit the light beam 3. The light tube entry 8 could be for example connected to a light collector arranged on a roof of a building for collecting daylight. According to the present arrangement the aperture 4 described with reference to Fig. la is equal to the light tube exit 4. A pipe is arranged between the light tube entry 8 and the light tube exit 4. The pipe is typically provided with a highly reflective inner surface for light transport. Furthermore, a re-directional structure 2 is arranged at the light tube exit 4. The re-directional structure 2 is typically a diffuser which is available in a variety of shades and rim designs. The diffuser may be applied in order to mask the dynamical directionality of the light collection during the course of the day, commonly known as daylight dynamics. The re-directional structure 2 is distanced from the aperture 4 by spacing means 6, as described in connection to Fig. la. The spacing means could be a part of the light tube 7 or be separated arranged between the light tube exit 4 and the re-directional structure 2.

According to the above the arrangement 1 has been described as fitted below the light tube exit 4 and below the inner ceiling 5 of a room (i.e. suspended from the ceiling). However, the arrangement 1 may also be fitted in a suspended ceiling. Fig. 3a illustrates an arrangement 1 comprising a re-directional structure 2 and a light box 16 fitted in a suspended ceiling. Such a fitting of the arrangement 1 may not be as obtrusive as an arrangement suspended from the ceiling. In an arrangement comprising a light box 16 the light tube exit 4 may in general be defined as the part of the light tube 7 where light is arranged to enter the light box 16 - independently of whether or not the light box 16 is (entirely or partly) suspended from the ceiling or (entirely or partly) fitted in a suspended ceiling.

The arrangement according to Fig. la, Fig. lb, Fig. 2 or Fig. 3a may comprise further components which now will be described in connection to Figs. 3b and 3c. Fig. 3b illustrates an arrangement for a low loss luminaire similar to the arrangements of Figs, la-b and 2. It should be noted that it is not necessary for every component shown in Fig. 3b to be included in a single embodiment of the present invention. It will be apparent for the skilled person which components that are dependent of others to achieve described features and advantages.

The arrangement illustrated in Fig. 3b may be regarded as a synthesis of a daylight tube system and a pendant lighting fixture. Natural daylight and connectivity to the outside is combined with the visual comfort, light functionality and freedom of design of electric light for the user. The arrangement may furthermore provide collimated light downstream of the light tube 7 combined with a diffuse spot at the surface surrounding the light tube exit 4.

The re-directional structure 2 may be a diffusing plate. The diffusing plate may be transmissive and thus capable of providing light in the downstream direction of the light tube exit 4. The diffusing plate may be reflective as well in order to provide light reflection towards the surface surrounding the light tube exit 4. This may enable illumination of two surfaces, for example a ceiling in combination with a floor. The re-directional structure 2 could furthermore be arranged to shield direct sunlight, also when viewed at large angles to the optical axis relative the light tube exit 4. Such an arrangement may enhance the visual comfort of a user and contribute to a soft harmonization between the arrangement and its surrounding interior.

A micro lens optical plate 9 may be arranged to receive a light beam 3 transmitted by the re-directional structure 2. The micro lens optical plate 9 may be arranged to transmit the light beam 3. It may also be arranged to reflect the light beam 3. The light beam 3 may be reflected at the micro lens optical plate 9 towards the diffuser plate where the light beam 3 can be reflected yet again towards the micro lens optical plate 9 or alternitively be transmitted through the re-directional structure 2.

A collimator 13 may be arranged at the light tube exit 4. Thereby the light beam 3 may be collimated downstream of the light tube exit 4 directly after exiting the light tube 7. The light extraciton efficiency of the light tube 7 may thereby be further enhanced. The collimator 13 may also contribute to reducing glare for a user. As an example, the collimator 13 could be be a compound parabolic concentrator.

The arrangement may further comprise a light source 10. The arrangement is not limited to comprise a single light source; the arrangement could equally comprise a plurality of light sources. The light source 10 may be located between the re-directional structure 2 and the micro lens optical plate 9. The light source 10 could for example be a light emitting diode (LED), but other types of light sources known to the skilled person could also be used. Artificial light emitted by the light source 10 may fill in seamlessly with a light beam 3 provided from the light tube exit 4. As an example the artificial light may be activated whenever daylight, i.e. light from the light tube exit 4, is obstructed. Such an obstruction could occur for example on a cloudy day or at night.

The light source 10 may be positioned and/or directed in a variety of configurations to achieve a preferred illumination arrangement, such as directed or dimmed lighting. According to the present arrangement the position of the light source 10 is chosen to provide functional light downstream of the light tube exit 4 and simultaneously to conceal the light source 10 behind the micro lens optical plate 9. In other embodiments of the present invention the position of a light source may be chosen to be, for example, at the rim of the collimator 13, on top of the re-directional structure 2 or at the edge of the micro lens optical plate 9. This is further examplified in Fig. 3c.

The arrangement could comprise a pendant fixture with integrated LED's. The arrangement may thereby allow for optimal and high efficiency mixing of artificial light and daylight. Also, beam shaping of the light can be performed simultaneously. The pendant fixture itself allows for a typical ceiling illumination if such is preferred. As an example, a sieve light may be arranged as a pendant fixture in for example office spaces. Using such a seive light a functional lighting may be achieved whilst still fulfilling the often desired stringent office glare norms.

The at least one light source lOmay furthermore be electrically coupled to a sensing circuitry 11 and/or a control circuitry 12. This enables the at least one light source 10 to be tuneable so that for example a dimmed lighting may be achieved. Furthermore, such an arrangement may create resilience against or enhancement of the daylight dynamics.

Moreover, the arrangement could be (part of) a lighting control system using the sensing circuitry 11 and/or the control circuitry 12.

The re-directional structure 2 may be arranged to mix daylight (as received at the aperture 4) and artificial light (as produced by the at least one light source 10). In particular, this is advantageous in an embodiment where the integrated artificial light is positioned at the rim of the re-directional structure 2. This improves the impression that the artificial light and daylight origin from a single light source.

Fig. 3c illustrates an arrangement for a low loss luminaire according to one embodiment. The arrangement in Fig. 3c is similar to the arrangements as disclosed above. The re-directional structure of the arrangement is defined by a plurality of lamellas 14 which provides collimation of light from the aperture 4. Light beams 3 that are emitted downstream through the aperture 4 towards a top part of the plurality of lamellas 14 will be Lambertian reflected and mostly add to illumination of the surface surrounding the light tube exit 4, e.g. a ceiling or a side wall. Light beams 3 that instead are emitted towards gaps between the plurality of lamellas 14 will be transmitted and add to the illumination of the surface downstream the plurality of lamellas 14.

A diffusing plate 15 may be added between the light tube exit 4 and the plurality of lamellas 14. The diffusing plate 15 reduces the daylight dynamics of a daylight tube system comprising the arrangement. Increasing the distance between the diffusing plate 15 and the light tube exit 4 may enhance the light extraction efficiency of the light tube 7.

The arrangement may further comprise a light source 10. This may be located between the diffusing plate 15 and the light tube exit 4. The present arrangement is not limited to comprise a single light source; the arrangement could equally comprise a plurality of light sources. The features and advantages in connection to the integration of light sources in the embodiment according to Fig. 3b likewise apply to the present embodiment. The above disclosed arrangements may be (part of) a luminaire.

A study has been performed by the inventors to investigate how the light extraction efficiency of a light tube arrangement is affected by the positioning of a re-directional structure downstream the exit aperture of the light tube. The study will now be described in further detail with reference to Fig. 4 to Fig. 6. In summary, the outcome of the study is that an efficiency gain of daylight extraction from a light tube 7 with an integrated re-directional structure 2 is achieved by increasing the distance between the re-directional structure 2 and the light tube exit 4. By increasing the distance the solid angle subtended by the light tube exit 4 is reduced and therefore the probability for light beams 3 to be reflected upstream of the light tube exit 4 into the light tube 7 is lowered. An increase of 59 % to 88 % daylight extraction efficiency has been shown. This result is obtained in case the distance between the light tube exit 4 and the re-directional structure 2 is about 0.5 m.

The model consists of a room located inside a building. The only present light source in the room is a light tube system. Daylight is provided to the room through the light tube system comprising a light tube 7, a light tube entry 8 and a light tube exit 4. The light tube exit 4 is surrounded by the ceiling of the room. The light tube 7 is modeled with a 100% inner surface reflectance. The floor is located opposite the ceiling of the room.

The following three scenarios were setup to investigate the relation between daylight extraction efficiency and the distance between the re-directional structure 2 and the light tube exit 4:

A first arrangement comprising exclusively the light tube 7 according to the above disclosed model (i.e. without any re-directional structure), as shown in Fig. 4.

A second arrangement comprising the light tube 7 according to the above disclosed model and also including a re-directional structure 2, with 30 % reflectance and 70 % transmittance positioned in direct connection to the light tube exit 4, as shown in Fig. 5.

A third arrangement comprising the light tube 7 according to the model and also including a re-directional structure 2, with 30 % reflectance and 70 % transmittance, positioned 0.5 m downstream of the light tube exit 4, as shown in Fig. 6.

In the first scenario an annular shaped beam spot on the floor from the light tube is formed, yielding a total radiant flux of 469 W.

In the second scenario a beam spot is formed on the floor yielding a radiant flux of 275 W. The resulting daylight extraction efficiency compared to the first scenario is thus about 59 %. In the third scenario a beam spot is formed on the floor, yielding a radiant flux of 312 W. At the ceiling the resulting luminance yields a radiant flux of 103 W due to reflected light by the re-directional structure 2. In the second scenarios no such significant flux is yielded at the ceiling. Thus the total flux in the third scenario is 415 W. The resulting daylight extraction efficiency compared to the first scenario is about 88 % and the radius of the beam spot is larger than for the first scenario thus providing more evenly distributed light than the concentrated beam spot of the first arrangement as used in the first scenario.

Thus, one result of the study is that an increase from 59 % to 88 % of daylight extraction efficiency is yielded when changing from the second scenario to the third scenario, i.e. when increasing the distance between the re-directional structure 2 and the light tube exit 4 with 0.5 m whilst providing an even distribution of light in the room.

In summary the disclosed embodiments relate to an arrangement for a low loss luminaire and in particular to such an arrangement in a system comprising a daylight tube system. Light is provided by an aperture and a re-directional structure is arranged at a distance LI from the aperture. The light extraction efficiency from the aperture is thus enhanced in comparison to known techniques.

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, the disclosed arrangement can be a part of other types of daylight guiding systems, such as anidolic ceilings, lightpipes, and the like.

Claims

CLAIMS:

1. An arrangement (1) comprising:

a re-directional structure (2) arranged to receive light (3) from an aperture (4) in a first surface (5),

wherein the aperture has a diameter Dl and is oriented towards the re-directional structure,

wherein the re-directional structure is arranged to be positioned at a distance LI from the aperture, the distance LI being larger than the diameter Dl of the aperture,

wherein the re-directional structure is arranged to transmit light towards a second surface, and

wherein the re-directional structure is arranged to reflect light, such that light reflected by the re-directional structure is reflected towards the first surface.

2. The arrangement according to claim 1, further comprising sidewalls (15) attached to the re-directional structure and extending towards the first surface.

3. The arrangement according to claim 1 or 2, wherein the re-directional structure and/or the sidwalls is a semi-transparent diffuser.

4. The arrangement according to any one of claims 1 to 3, wherein the re-directional structure and/or the sidwalls is defined by a plurality of lamellas (14).

5. The arrangement according to claim 4, further comprising a diffusing plate (15), the diffusing plate being arranged between the plurality of lamellas and the aperture.

6. The arrangement according to any one of claims 1 to 5, further comprising a micro lens optical plate (9), the micro lens optical plate being arranged to receive light transmitted by the re-directional structure.

7. The arrangement according to claim 6, further comprising at least one light source (10) located between the re-directional structure and the micro lens optical plate.

8. The arrangement according to any one of claims 1 to 6, further comprising at least one light source (10) located between the re-directional structure and the aperture.

9. The arrangement according to claim 7 or 8, wherein the at least one light source is electrically coupled to sensing circuitry (11) and/or control circuitry (12).

10. The arrangement according to any one of claims 1 to 9, wherein the distance LI is at least twice as large as the diameter Dl of the aperture.

11. The arrangement according to any one of claims 1 to 10, wherein the re-directional structure has a diameter D2, and wherein a ratio between the diameter Dl of the aperture and the diameter D2 of the re-directional structure is equal to or smaller than 1.

12. The arrangement according to any one of claims 1 to 11, further comprising a light tube (7) having an entry aperture (8) arranged to receive light and an exit aperture (4) arranged to emit light, the exit aperture defining the aperture of the first surface.

13. The arrangement according to claim 12, further comprising a collimator (13) arranged at the exit aperture of the light tube.

14. A luminaire comprising at least one arrangement according to any one of claims 1 to 13.

15. A lighting control system comprising at least one arrangement according to any one of claims 1 to 13.