WO2015028328A2

WO2015028328A2 - Dual function luminaire

Info

Publication number: WO2015028328A2
Application number: PCT/EP2014/067536
Authority: WO
Inventors: Anthonie Hendrik Bergman
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-08-30
Filing date: 2014-08-18
Publication date: 2015-03-05
Also published as: WO2015028328A3

Abstract

The invention provides a lighting unit comprising a first light source and a second light source, a first plate-like light guide having first light guide edge, and a second plate-like light guide having a second light guide edge, wherein the first light source is configured to couple first light source light into the first plate-like light guide via the first light guide edge, wherein the second light source is configured to couple second light source light into the second plate-like light guide via the second light guide edge, wherein the first plate- like light guide is configured to couple first lighting unit light out a first light guide face and wherein the second plate-like light guide is configured to couple second lighting unit light out via a second light guide outcoupling edge, wherein the first light source and the second light source are independently controllable.

Description

Dual function luminaire

FIELD OF THE INVENTION

The invention relates to a lighting unit comprising one or more light guides and to a light guide per se. The invention further relates to a use of the lighting unit for one or more purposes.

BACKGROUND OF THE INVENTION

Lighting devices that can have dedicated functions are known in the art.

US2013039090, for instance, describes a variety of illumination devices that are configured to manipulate light provided by one or more light-emitting elements (LEEs). In general, embodiments of the illumination devices of US2013039090feature one or more optical couplers that redirect illumination from the LEEs to a reflector which then directs the light into a range of angles. In some embodiments, the illumination device includes a second reflector that reflects at least some of the light from the first reflector. In certain embodiments, the illumination device includes a light guide that guides light from the collector to the first reflector. The components of the illumination device can be configured to provide

illumination devices that can provide a variety of intensity distributions. Such illumination devices can be configured to provide light for particular lighting applications, including office lighting, task lighting, cabinet lighting, garage lighting, wall wash, stack lighting, and down lighting.

SUMMARY OF THE INVENTION

Looking at the activities that take place around a dining table and judging what kind of light is needed it turns out that two main functions may exist. The common one is illuminating the table itself, for instance to read, eat, or work. The second one is when the table top itself is not the place of attention, but the people around it, for instance after dinner enjoying a glass of wine.

For illuminating people's faces around the table one quite often uses candles. This is both a nice a light to watch, but is also done because the luminaire over the table is in general unable to do this in a friendly way. Similar problems may be encountered for instance in office rooms and other spaces, wherein it may be desirable to provide target lighting and a more diffuse general lighting, wherein especially the latter does not provide undesired glare effects.

Hence, it is an aspect of the invention to provide an alternative lighting unit, which preferably further at least partly obviate one or more of above-described drawbacks and/or can meet the above-indicated desired functionalities. It is yet a further aspect of the invention to provide an alternative light guide, that may be used in such lighting unit, which preferably further at least partly obviate one or more of above-described drawbacks and/or can meet the above-indicated desired functionalities.

The main idea is to create a luminaire especially capable to illuminate e.g. a table but also to illuminate the people (around such table) without causing uncomfortable glare. The second idea is to be able to direct the light on the table, wherein especially (also) the direction can be chosen by a user. Further it is desirable that for instance a user can control the relative amounts of light of the different types of light.

In a first aspect, the invention provides (thereto) a lighting unit comprising a first light source and optionally a second light source, a first plate-like light guide (herein also indicated as "first light guide", or sometimes also indicated as "plate") having first light guide edge, and optionally a second plate-like light guide (herein also indicated as "second light guide" or sometimes also indicated as "plate") having a second light guide edge, wherein the first light source is configured to couple first light source light into the first platelike light guide via the first light guide edge, wherein the optional second light source is configured to couple second light source light into the (optional) second plate-like light guide via the second light guide edge, wherein especially the first plate-like light guide is configured to couple first lighting unit light out a first light guide face and wherein the optional second plate-like light guide is especially configured to couple second lighting unit light out via a second light guide outcoupling edge, wherein especially the first light source and the (optional) second light source are independently controllable, and wherein one or more of the first and second light guides are flexible and wherein the lighting unit further comprises an infrastructure for directing one or more of the first lighting unit light and second lighting unit light by bending one or more of the first plate-like light guide (100) and the second plate-like light guide. Such lighting unit is herein also indicated as "dual function luminaire".

Such lighting unit may for instance be used for illuminating a room and providing target lighting to a surface (in such room). Especially, such lighting unit may be used to illuminate the room while providing (target) lighting to a table or a desk (in such room). The light that is coupled out from the first light guide may be diffuse light and may for instance, during use of the lighting unit, have a main direction (optical axis) that is substantially horizontal, whereas the light that is coupled out form the second light guide may have a relative small opening angle and/or have a distribution that prevents or reduces glare, and may for instance, during use of the lighting unit, have a main direction (optical axis) that is substantially vertical.

With such lighting unit, in a user pleasant way general lighting, may be provided, to illuminate a room, and target lighting may be provided to a surface below the lighting unit (when arranged for use). Especially, the lighting unit will be configured as down lighter or pendant lamp, i.e. a lighting unit integrated in a ceiling or suspending from a ceiling. However, also other configuration are possible, including e.g. with a lamp standard.

The term "room" may refer to an office room, a room in a house, a room in a hospitality environment such as a hotel room, or a hospital room. The lighting unit may for be used for illuminating any space. The space may for instance be (part of) a hospitality area, such as a restaurant, a hotel, a clinic, or a hospital, an office, a department store, a warehouse, a cinema, a church, a theatre, a library, etc.

By using two, or at least two, independently controllable light sources, the ratio of the light from the two light guides, i.e. the two different types of light, can be tuned according to the desire of a user. This may include a predefined time scheme. The use of two independently controllable types of light sources also allows providing light with different colors and/or different color temperatures. Control may e.g. be done via a (remote)(wireless) user interface. Preferably, the first light source and the second light source are light sources that during operation emit (light source light) at least in the visible. Especially, the second light source may at least be configured to provide white light, as this light may be used for target lighting, and may facilitate activities of a human. In an embodiment, the first light source and the second light source are light sources that during operation emit (light source light) light having different spectral characteristics. In embodiments, the lighting unit may be configured to provide first lighting unit light and second lighting unit light having a different color temperature, such as a color temperature difference of at least 100 K, especially at least 500 K, such as at least 1000 K. In embodiments, the lighting unit may be configured to provide first lighting unit light and second lighting unit light having different colors, such as colored light and white light, respectively. Optionally, one or more of the color and color temperature of the first light source light and/or the color or the second light source light is also controllable.

In a specific embodiment, the light source comprises a solid state LED light source (such as a LED or laser diode). The term "light source" may also relate to a plurality of light sources, such as 2-20 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs. The term "light source" refers to both the first light source and the second light source, which, as indicated above, can each independently refer to a plurality of (first or second) light sources. Further, the invention does not exclude the presence of further light guides, especially plate-like light guides and (third or further) light sources functionally coupled thereto. However, for the sake of clarity, at least the two relevant platelike light guides are further described.

The term white light herein, is known to the person skilled in the art. It especially relates to light having a correlated color temperature (CCT) between about 2000 and 20000 K, especially 2700-20000 K, for general lighting especially in the range of about 2700 K and 6500 K, and especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL.

In an embodiment, the light source may also provide light source light having a correlated color temperature (CCT) between about 5000 and 20000 K, e.g. direct phosphor converted LEDs (blue light emitting diode with thin layer of phosphor for e.g. obtaining of 10000 K). Hence, in a specific embodiment the light source is configured to provide light source light with a correlated color temperature in the range of 5000-20000 K, even more especially in the range of 6000-20000 K, such as 8000-20000 K.

The terms "violet light" or "violet emission" especially relates to light having a wavelength in the range of about 380-440 nm. The terms "blue light" or "blue emission" especially relates to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues). The terms "green light" or "green emission" especially relate to light having a wavelength in the range of about 490-560 nm. The terms "yellow light" or "yellow emission" especially relate to light having a wavelength in the range of about 540- 570 nm. The terms "orange light" or "orange emission" especially relate to light having a wavelength in the range of about 570-600. The terms "red light" or "red emission" especially relate to light having a wavelength in the range of about 600-750 nm. The term "pink light" or "pink emission" refers to light having a blue and a red component. The terms "visible", "visible light" or "visible emission" refer to light having a wavelength in the range of about 380-750 run.

Herein, the light guides are indicated as plate-like light guides. This may especially indicate that the thickness of the plates is in general smaller than one or more of their length and width, assuming rectangular plate like plates. However, the plates may also have other shapes. Nevertheless, in general the thickness (of the plate-like light guides) may be smaller than their length and/or width. Further, in general the plate-like light guides are planar, though they may also be curved. Further, the plate-like light guides may also independently be wedge shaped. As indicated below, one or more of the light guides are flexible, which may also a bended configuration, either permanently or temporarily (see also below).

Instead of the term light guide also the term wave guide may be applied. The term wave guide or light guide may especially refer to a (solid (or optionally liquid)) material that allows transport of electromagnetic radiation, here especially visible light. Hence, the light guides herein are transmissive, especially transparent (for visible light).

The light guide may comprises, or essentially consist of, one or more materials selected from the group consisting of a transmissive organic material support, such as selected from the group consisting of PE (polyethylene), PP (polypropylene), PEN

(polyethylene napthalate), PC (polycarbonate), polymethylacrylate (PMA),

polymethylmethacrylate (PMMA) (Plexiglas or Perspex), cellulose acetate butyrate (CAB), silicone, polyvinylchloride (PVC), polyethyleneterephthalate (PET), (PETG) (glycol modified polyethyleneterephthalate), PDMS (polydimethylsiloxane), and COC (cyclo olefin copolymer). However, in another embodiment light guide may comprise an inorganic material. Preferred inorganic materials are selected from the group consisting of glasses, (fused) quartz, transmissive ceramic materials, and silicones. Also hybrid materials, comprising both inorganic and organic parts may be applied.

Especially, the material of the light guide has a light transmission in the range of 50-100 %, especially in the range of 70-100%, for light generated by the light source and having a wavelength selected from the visible wavelength range. Herein, the term "visible light" especially relates to light having a wavelength selected from the range of 380-780 nm.

The transmission or light permeability can be determined by providing light at a specific wavelength with a first intensity to the material and relating the intensity of the light at that wavelength measured after transmission through the material, to the first intensity of the light provided at that specific wavelength to the material (see also E-208 and E-406 of the CRC Handbook of Chemistry and Physics, 69th edition, 1088-1989).

The first light source is especially radiationally coupled to the first light guide and the second light source is especially radiationally coupled to the second light guide. The term "radiationally coupled" especially means that the light source and the light guide are associated with each other so that at least part of the radiation emitted by the light source is received by the light guide. As indicated above, the first light source is configured to couple first light source light into the first plate-like light guide via the first light guide edge. Further, as indicated above, the second light source is configured to couple second light source light into the second plate-like light guide via the second light guide edge.

As the first light guide is configured to couple light out via a light guide face, the first light guide may comprise outcoupling structures. These outcoupling structures may comprise one or more of (i) discontinuities at the face(s) and (ii) outcoupling structures within the material of the light guide, especially particles. Such particles are herein also indicated as scattering particles. Hence, especially, the first light guide may be configured to provide diffuse (outcoupled) (lighting unit light) light. This may also imply that the first light guide may be (slightly less) transparent than the second light guide. Optionally, the first light guide has some translucency or is translucent, whereas the second light guide is (essentially) transparent. For further information about outcoupling, see also below.

The light guides may be arranged in series, but may especially also be arranged parallel. Especially, a face of the first light guide is over essentially its entire area in physical contact with a face of the second light guide. Hence, also a face of the second light guide is over essentially its entire area in physical contact with a face of the first light guide. Especially, the light guide may have in such embodiments substantially the same areas (of faces that are in physical contact). Terms like "parallel" or "perpendicular" may also relate to essentially parallel or essentially perpendicular, respectively.

During operation, the light that escapes from the first light guide will in general travel in another direction than the light that escapes from the second light guide. Especially, the light that escapes from the former is essentially perpendicular to the latter. Hence, in a specific embodiment the first plate-like light guide and the second plate-like light guide are arranged parallel, and the lighting unit is especially configured to provide first lighting unit light (escaping from (the first light guide face of) the first plate-like light guide) and second lighting unit light (escaping from (the second light guide outcoupling edge of) the second plate-like light guide) with optical axes having a mutual angle in the range of 60-120°, especially 70-110°, such as 80-100°, and wherein especially the first lighting unit light has diffuse character. In this way, e.g. a beam may travel in a direction with an optical axis that may be substantial horizontal (room lighting) and a beam may travel in a direction with an optical axis that may be substantial vertical (target lighting). Hence, the lighting unit may be configured to provide - during use of the lighting unit - two types of lighting unit light, especially having different characteristics (like diffuse and focused), that have substantially perpendicular optical axes. The term "diffuse character" may especially indicate that the light may have a substantially Lambertian distribution. Especially, the first lighting unit light has more diffuse character than the second lighting unit light. Hence, the light distribution of the first lighting unit light may comply more with a Lambertian distribution than the second lighting unit light. The first lighting unit light may (thus) have less directional character than the second lighting unit light. The first lighting unit light may be more scattered, due to the outcoupling structures, than the second lighting unit light. The latter light may especially be used as target light.

In order to protect the light guides, they may be protected with outer plates.

These outer plates are especially essentially transparent. In an embodiment, the first light guide is sandwiched between two outer plates. In yet another embodiment, the second light guide is sandwiched between two outer plates. In yet a further embodiment, the lighting unit comprises a sandwich structure with two outer plates enclosing in between the first plate-like light guide and the second plate-like light guide (with especially the latter two being in physical contact with each other with contacting faces). Hence, the invention (also) includes a sandwich structure of an outer plate, a first light guide, a second light guide, and another outer plate, with especially adjacent plates in physical contact with each other.

As already indicated above, outcoupling of light from the light guides may be effected via several ways. Especially in case of the first light guide, outcoupling features are provided at one or more of the (two) faces. In this way, diffuse light may escape from the light guide, especially in a direction perpendicular to the light guide face(s). However, alternatively or additionally, the outcoupling features may direct the light in a direction not perpendicular to the light guide face(s). The main direction in which the light that is coupled out from the light guide is indicated with the optical axis. The (light) outcoupling features (at one or more of the faces (and/or optionally edges)) may in embodiments include irregularities, such as irregularities at one or more of the faces. For instance, the outcoupling features may include a textured surface, like a textured face. Outcoupling features may include grooves, indentations, etc. A further example to provide outcoupling features is frosting a surface. Frosting can for instance be produced by grinding or otherwise abrading a surface. Hence, the first light guide face may be frosted. Alternatively or additionally, the light guide face opposite of the first light guide face may be frosted.

The fact that outcoupling features or structures are available, does not exclude that part of the light may escape from one or more edges, especially an edge opposite to the first light guide edge. Note however that optionally one or more mirrors (and/or optical elements (herein also indicated as "optical active components") with a similar function, e.g. a slanted slit) may be provided to have light extraction in one desired direction, or optionally two (opposite) directions (i.e. from both faces). Hence, the lighting unit may further include one or more optical elements configured to further direct and/or diffuse (one or more of) the first lighting unit light (and the second lighting unit light). Therefore, optionally one or more optical active components like mirror and extraction elements may be provided to the first light guide in order to facilitate extraction from the light guide at the first light guide face (and optionally an opposite face). The opposite face of the first light guide face may herein also be indicated as second first light guide face. Especially, the edge(s) may bridge the first light guide face and the opposite or second first light guide face. As indicated above, in embodiments, especially when light outcoupling particles are applied and/or when this latter (also) includes light outcoupling features, light may also escape from this opposite face. In specific embodiments, light escaping from this face may enter the second plate-like light guide, penetrate, and escape therefrom, such as at a face of the second light guide. Hence, in a specific embodiment, especially wherein the first light guide and the second light guide are adjacent, at least part of the first lighting unit light propagates through the second light guide and escapes therefrom. As indicated above, the second light guide may be (essentially) transparent.

In a specific embodiment, the first plate-like light guide comprises scattering particles (as an embodiment of (light) outcoupling features) embedded in the first plate-like light guide. Such scattering particles may especially comprise one or more of alumina (AI₂O₃), barium sulphate (BaS0₄), magnesium oxide (MgO), and titania (Ti0₂). Especially, the first plate-like light guide comprises scattering particles embedded therein, wherein the scattering particles have (number) average(d) dimensions selected from the range of 0.1-50 μιη. Further, especially the amount of scattering particles relative to the total weight of the light guide may be in the range of 0.0001-0.01 wt.%, especially in the range of 0.0005-0.005 wt.%. Additionally or alternatively, the first plate-like light guide comprises scattering features at the first light guide face (and optionally also at an opposite face of the first light guide). As indicated above, optionally the first light guide may be configured to provide light in two (opposite) directions. Hence, in an embodiment the first plate-like light guide is configured to couple first lighting unit light out the first light guide face and a second first light guide face.

Especially in case of the second light guide, light may especially escape from an opposite edge, such a light guide outcoupling edge opposite of the second light guide edge. Note that optionally one or more optical active components like mirror and extraction elements may be provided to the second light guide in order to facilitate extraction from the light guide at the light guide outcoupling edge. Such extraction elements may thus optionally (also) include light outcoupling features. Hence, in an embodiment the second light guide edge may be frosted.

In general, the amount (in terms of power) of light coupled out via one or more faces of the first light guide is larger than the amount of light coupled out via one or more edges, especially at least two times larger, even more especially at least 10 times larger. In general, the amount (in terms of power) of light coupled out via one or more edges of the second light guide is larger than the amount of light coupled out via one or more faces, especially at least two times larger, even more especially at least 10 times larger.

Good optical properties may especially be obtained with poly acrylates, such as PMMA, and/or poly siloxanes. Hence, in an embodiment one or more of the first plate-like light guide and the second plate-like light guide comprise a poly acrylate material. In yet another embodiment, one or more of the first plate-like light guide and the second plate-like light guide comprise a poly siloxane material. Combinations of materials may also be applied. Further, also one light guide may e.g. comprise a poly acrylate, like PMMA, such as the second light guide, whereas the other light guide may comprise a poly siloxane, like the first light guide.

In a specific embodiment the first plate-like light guide comprises a poly siloxane with titania (Ti0₂) particles embedded therein, wherein the titania particles have average dimensions selected from the range of 0.1-50 μιη, and wherein the amount of titania particles relative to the total weight of the poly siloxane is in the range of 0.0001-0.01 wt.%.

Further (optical) features of interest may be obtained when the light guide, especially the first light guide, may comprise domains with lower (or zero) scattering particle content embedded in the light guide material. For instance in a polymer material light guide comprising particulate scattering material, holes can be made that may at least partly be filed with polymer material (especially of the same type) comprising lower or no particulate material. Hence, in an embodiment the first plate-like light guide comprises domains having volumes of at least 0.1 cm³, wherein the amount in titania in the domains and in the surrounding material differ with a factor of at least 5, such as at least 10, like at least 100. As indicated above, it may also be possible that either the domains or the surrounding material has no particulate scattering material at all. With domains additional scattering effects may be provided. Interestingly, those holes may not cast shadows. With the domains, light distribution can further be tuned.

Features of interest are obtained with one or both light guides have flexible properties. This may allow further directioning the light. By applying a (bending) force onto at least one of the light guides having a basic shape, said at least one of the light guides assumes a changed shape, either temporarily or permanently. Said changed shape can be maintained either by maintaining the (bending) force on a light guide made of resilient material, i.e. when the force ceases to be exerted on the light guide it will spring back to its basic shape. Alternatively, the light guide can be made of a deformable material which maintains a changed shape by itself, i.e. wherein the assumed shape is maintained without the need for a (bending) force to be exerted permanently. Hence, in an embodiment both the first plate-like light guide and the second plate-like light guide are flexible. The lighting unit having a flexible first and/or second light guide may also be indicated as "flexible dual function luminaire". The first and second light guide may be coupled to each other, for example via an optical unit, such that a, for example bending, pressing or pulling, force applied on either one of the light guide affects the shape of both light guides or that the rigidity of the first light guide influences the deformation behavior of the second light guide, and vice versa. The infrastructure may comprise one or more of pneumatic, electronic, magnetic, and mechanical means, etc., to bend a plate-like light guide.

In a further aspect, the invention provides a lighting unit comprising a first light source, a first plate-like light guide (herein also indicated as "first light guide") having first light guide edge, wherein the first light source is configured to couple first light source light into the first plate-like light guide via the first light guide edge, wherein especially the first plate-like light guide is configured to couple first lighting unit light out a first light guide face, wherein especially the first light source is controllable. In yet a further first aspect, the invention provides a lighting unit comprising a second light source, a second plate-like light guide (herein also indicated as "second light guide") having a second light guide edge, wherein the second light source is configured to couple second light source light into the second plate-like light guide via the second light guide edge, wherein the second plate-like light guide is especially configured to couple second lighting unit light out via a second light guide outcoupling edge, and wherein especially the second light source is controllable.

Especially, these embodiments may further include one or more of flexible light guides, especially flexible poly siloxane light guides, and/or one or more light guides having the above described domains.

In yet a further aspect, the invention provides a plate-like light guide comprising a poly siloxane material, wherein the plate-like light guide comprises light out coupling structures configured to couple light, that is coupled into the plate-like light guide via the light guide edge, out of one or more a first light guide face and a second light guide face, wherein the plate-like light guide has a thickness of at least 200 μιη, and wherein the plate-like light guide is flexible. This light guide is above also indicated as first light guide or first plate- like light guide.

Especially, the plate-like light guide may comprise a poly siloxane with scattering particles embedded therein, wherein the scattering particles have (number) average(d) dimensions selected from the range of 0.1-50 μιη, and the amount of scattering particles relative to the total weight of the poly siloxane is in the range of 0.0001-0.01 wt.%.

In yet a further embodiment, the first plate-like light guide comprises domains having volumes of at least 0.1 cm³, wherein the amount in scattering particles in the domains and in the surrounding material differ with a factor of at least 10. As indicated above, especially the scattering particles may comprise titania (Ti0₂).

The lighting unit may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive

applications, green house lighting systems, horticulture lighting, or LCD backlighting.

The term "substantially" herein, such as in "substantially all light" or in "substantially consists", will be understood by the person skilled in the art. The term

"substantially" may also include embodiments with "entirely", "completely", "all", etc.

Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term "substantially" may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. Likewise this may apply to the term "essentially". The term "comprise" includes also embodiments wherein the term

"comprises" means "consists of. The term "and/or" especially relates to one or more of the items mentioned before and after "and/or". For instance, a phrase "item 1 and/or item 2" and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. 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.

The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications. US20110309735 Al discloses a lighting unit comprising two independently controllable light sources and two corresponding light guides wherein the first and second light guide emit light in different directions. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig. la- lb schematically depict embodiment so the lighting unit; Figs. 2a -2c schematically depict some aspects of the invention;

Figs. 3a-3c schematically depict some further embodiments of the invention; Fig. 4 schematically depicts an application of the lighting unit.

The drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. la- lb schematically depict two embodiments of the lighting unit as described herein. They show a lighting unit 1000 comprising a first light source 10 and a second light source 20, a first plate-like light guide 100 having first light guide edge 110, and a second plate-like light guide 200 having a second light guide edge 210.

The first light source 10 is configured to couple first light source light 11 into the first plate-like light guide 100 via the first light guide edge 110. Further, the second light source 20 is configured to couple second light source light 21 into the second plate-like light guide 200 via the second light guide edge 210. The first plate-like light guide 100 is configured to couple first lighting unit light 1101 out a first light guide face 150. Further, the second plate-like light guide 200 is configured to couple second lighting unit light 1201 out via a second light guide outcoupling edge 230. Especially, the first light source 10 and the second light source 20 are independently controllable. This may be done with a control unit 50, which is functionally coupled to the lighting unit 100. In an embodiment, a (remote) user interface 51 may be applied (see also fig. 4). For instance, the first light guide 100 may be translucent and the second light guide 200 may be transparent.

References 1111 and 1211 indicate the respective optical axes of the first lighting unit light 1101 and the second lighting unit light 1201. The mutual angle is indicated with Θ. This angle may especially be in the range of 60-120°, especially 70-110°. Fig. lb schematically depicts an embodiment wherein one or more of the first light guides, here especially the second light guide, is not planer. Also in this way the optical properties of the lighting unit light can be controlled.

In operation light of the light sources enters via an edge the respective light guides. These light guides are thus arranged downstream of the respective light sources. Further, incoupled light escapes from the respective light guides via one or more of one or more faces and one or more edges. The terms "upstream" and "downstream" relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is "upstream", and a third position within the beam of light further away from the light generating means is "downstream". In operation, both types of light sources may be switched on. Optionally, one may be switched off. As indicated above, they may be controlled independently. Further, one or both may comprise a plurality of light sources. Also, the first and the second light sources may generate light having different color temperature or color.

Note that in both embodiments schematically depicted in figs, la- lb the first lighting unit light 1101 is not only coupled out from the first light guide face 150, but also from an opposite face 160. First light guide face 150 and light guide face 160 are herein also indicated as opposite faces (with the edge in between). The opposite face 160 of the first light guide face 150 may herein also be indicated as second first light guide face. As indicated above, in embodiments, especially when light outcoupling particles are applied and/or when this latter (also) includes light outcoupling features, light may also escape from this opposite face. This is also indicated in fig. la (and 3b, 3c, and 4). In for instance the specific embodiment schematically depicted in fig. la, light escaping from this face 160 may enter the second plate-like light guide (via face 250), penetrate, and escape therefrom, such as at a face of the second light guide (which face may again be opposite of face 250. Hence, at least part of the first lighting unit light 1101 propagates through the second light guide 200 and escapes therefrom.

Fig. 2a schematically depicts embodiments of the first light guide 100 and the second light guide 200. Here, they are depicted as planar plates with length 1, height h, and width w. Note that the respective dimensions are not necessarily the same. Further, not only rectangular plates may be used (see also fig. lb wherein w varies over the height h), but also round or oval plates, etc. Nevertheless, in general w< 1 and w< h. The width may in embodiments be at least 200 μιη. Especially, the thickness is defined by the distance between the two opposite faces. Optionally the distance (or thickness) varies over the light guide(s).

The plates have edges 110, 120, 130, 140, and 210, 220, 230 and 240, respectively. Edge 110 and edge 210 are herein also indicated as first and second light guide edges, respectively. Further, edge 230 is herein also indicated as second light guide outcoupling edge 230. The light guides 100,200 further comprise faces 150,160 and 250,260, respectively. Herein, face 150 is also indicated as first light guide face 150.

The edges (110, 120, 130, 140, and 210, 220, 230 and 240, respectively) connect the faces of the respective plate-like light guides. Note that optionally one or more of the edges and/or faces may independently be curved. For instance, the second light outcoupling edge may be curved in a direction from edge 220 to edge 240, but may especially be curved in a direction from face 250 to face 260. The latter embodiment may create a larger opening angle of the beam of the second lighting unit light (an analogous effect as the configuration chosen in fig. lb).

Figs. 2a-2b schematically depict several options for outcoupling structures 170, which may be at one or more of the faces 150,160 (in case of the first light guide), indicated with references 172 and which may optionally also be at the second light outcoupling edge 230 (not depicted). Further, additionally or alternatively the outcoupling structures 170 may include particulate material or particles 171 which may be embedded in the material of the light guide.

Fig. 2c schematically depicts a first light guide 100 comprising domains 180. These domains may comprise different amounts of scattering material or particles 171 than the surrounding material. Optionally, the amount of scattering materials in either the domains 180 or the surrounding material is zero.

Fig. 3 a schematically depicts a lighting unit 1000 wherein one or both the light guides are flexible. In the right figure, further an infrastructure 40 for bending the flexible light guide is depicted. By way of example, the second light guide 200 is bent in the right drawing.

Fig. 3b schematically depicts a lighting unit 1000 comprising a sandwich structure 300 with two outer plates 310,320 enclosing in between the first plate-like light guide 100 and the second plate-like light guide 200. Other sandwich structures are however also possible.

Fig. 3c again shows a lighting unit 1000 comprising one or more flexible light guides 100,200. In this embodiment, but that may apply in general to all herein described embodiments, one or both light guides are optically (and physically) coupled to an optical unit 500. This optical unit 500 may be applied to further control optical properties, like beam angle and/or beam direction of especially the second lighting unit light 1201. By exerting in top-down direction a permanent pressing force on the first light guide 100 via an

infrastructure 40 at a side remote from the optical unit 500 and/or by exerting in top-down direction a pulling force on the second light guide 200 via said infrastructure 40, both the first and second light guide assume and maintain a changed shape. Furthermore, as a result the optical unit 500 assumes a tilted position and the light issued from said optical unit is redirected. The infrastructure in this embodiment comprises mechanical means to set the push-pulling force, for example adjustable screws or sliders to adjust the vertical position of the infrastructure (not shown).

Fig. 4 schematically depicts an application wherein the lighting unit 1000 is used for illuminating a room 1, especially with first lighting unit light 1101 and providing target lighting to a surface 2, such as from a table, with especially second lighting unit light 1201. Control may be done via e.g. a remote user interface 51.

Claims

CLAIMS:

1. A lighting unit (1000) comprising a first light source (10) and a second light source (20), a first plate-like light guide (100) having first light guide edge (110), and a second plate-like light guide (200) having a second light guide edge (210), wherein the first light source (10) is configured to couple first light source light (11) into the first plate-like light guide (100) via the first light guide edge (110), wherein the second light source (20) is configured to couple second light source light (21) into the second plate-like light guide (200) via the second light guide edge (210), wherein the first plate-like light guide (100) is configured to couple first lighting unit light (1101) out a first light guide face (150) and wherein the second plate-like light guide (200) is configured to couple second lighting unit light (1201) out via a second light guide outcoupling edge (230), wherein the first light source (10) and the second light source (20) are independently controllable and wherein one or more of the first and second light guides are flexible and wherein the lighting unit (1000) further comprises an infrastructure (40) for directing one or more of the first lighting unit light (1101) and second lighting unit light (1201) by bending one or more of the first plate- like light guide (100) and the second plate-like light guide (200).

2. The lighting unit (1000) according to claim 1, wherein the first plate-like light guide (100) and the second plate-like light guide (200) are arranged parallel, and wherein the lighting unit (1000) is configured to provide first lighting unit light (1101) and second lighting unit light (1201) with optical axes (1111,1211) having a mutual angle in the range of 70-110°, and wherein the first lighting unit light (1101) has diffuse character.

3. The lighting unit (1000) according to any one of the preceding claims, comprising a sandwich structure (300) with two outer plates (310,320) enclosing in between the first plate-like light guide (100) and the second plate-like light guide (200).

4. The lighting unit (1000) according to any one of the preceding claims, wherein the first plate-like light guide (100) comprises scattering particles (171) embedded in the first plate-like light guide (100).

5. The lighting unit (1000) according to any one of the preceding claims, wherein the first plate-like light guide (100) comprises scattering features (172) at the first light guide face (150).

6. The lighting unit (1000) according to any one of the preceding claims, wherein the first plate-like light guide (100) is configured to couple first lighting unit light (1101) out the first light guide face (150) and a second first light guide face (160).

7. The lighting unit (1000) according to any one of the preceding claims, wherein one or more of the first plate-like light guide (100) and the second plate-like light guide (200) comprise an poly acrylate material.

8. The lighting unit (1000) according to any one of the preceding claims, wherein one or more of the first plate-like light guide (100) and the second plate-like light guide (200) comprise a poly siloxane material.

9. The lighting unit (1000) according to claim 8, wherein the first plate-like light guide (100) comprises a poly siloxane with titania (Ti0₂) particles (171) embedded therein, wherein the titania particles have average dimensions selected from the range of 0.1-50 μιη, and wherein the amount of titania particles relative to the total weight of the poly siloxane is in the range of 0.0001-0.01 wt.%.

10. The lighting unit (1000) according to any one of the preceding claims, wherein both the first plate-like light guide (100) and the second plate-like light guide (200) are flexible.

11. A plate-like light guide (100) comprising a poly siloxane material, wherein the plate-like light guide (100) comprises light out coupling structures (170) configured to couple light, that is coupled into the plate-like light guide (100) via the light guide edge (110), out of one or more a first light guide face (150) and a second light guide face (160), wherein the plate-like light guide (100) has a thickness of at least 200 μιη, and wherein the plate- like light guide (100) is flexible.

12. The plate-like light guide (100) according to claim 11, comprising a poly siloxane with scattering particles (171) embedded therein, wherein the scattering particles have average dimensions selected from the range of 0.1-50 μιη, and wherein the amount of scattering particles relative to the total weight of the poly siloxane is in the range of 0.0001- 0.01 wt.%.

13. The plate-like light guide (100) according to claim 11, wherein the first platelike light guide (100) comprises domains (180) having volumes of at least 0.1 cm³, wherein the amount in scattering particles (171) in the domains and in the surrounding material differ with a factor of at least 10.

14. The plate-like light guide (100) according to claim any one of claims 12-13, wherein the scattering particles (171) comprise titania (Ti0₂).

15. Use of a lighting unit (1000) as defined in any one of claims 1-10 for illuminating a room (1) and providing target lighting to a surface (2).