FIELD OF THE INVENTION

The present invention relates to a lighting device comprising multiple light sources mounted on a carrier, the light sources emitting light of a first wavelength range, a wavelength converting member arranged at a distance from said light sources configured for converting light of the first wavelength range into light of a second wavelength range, and an optical member arranged downstream of the wavelength converting member for optically effecting the light output of the lighting device.

BACKGROUND OF THE INVENTION

A lighting device of the above-mentioned kind generally is referred to as a large area lighting device, since the light output of the several light sources is distributed across a common output area of the lighting device. It is typically used as general lighting often mounted at the ceiling. It is advantageous to provide solid state lighting solutions for such lighting devices, due to the energy savings obtained in comparison with conventional light sources. Among the solid state lighting alternatives, the so called remote phosphor concept where a remote wavelength converter, typically a phosphor element, changes the colored light from a solid state light source such as a light emitting diode to white light is an efficient way for producing white light. Furthermore, different lighting demands at different places of the environment where the lighting device is mounted, and/or at different times in conjunction with energy saving demands call for adjustability of the lighting device, not only as a general dimming capability but as a capability of providing adjustable lighting at different positions of the environment, and more particularly at different positions within the area that the lighting device illuminates. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a lighting device that has the capability of providing adjustable light at different positions of the illuminated area.

The object is achieved by a lighting device according to the present invention as defined in claim 1. Thus, in accordance with an aspect of the present invention, there is provided a lighting device comprising multiple light sources mounted on a carrier, the light sources emitting light of a first wavelength range; a wavelength converting member arranged at a distance from said light sources, said wavelength converting member comprising a first wavelength converting material configured to convert light of said first wavelength range into light of a second wavelength range; and a segmented optical member arranged downstream of the wavelength converting member, and comprising at least one segment of a first segment type providing a first beam shape, and at least one segment of a second segment type providing a second beam shape, which is different from the first beam shape. The different beam shapes are useful for generating differently bright and differently focused light at the illuminated area.

In accordance with an embodiment of the lighting device, each segment is aligned with a respective one of the light sources. Thereby it is easy to adjust the lighting of different areas by dimming or turning off some of the light sources. For instance light sources providing common surrounding lighting or light sources providing spotwise illumination of for instance a working area can be adjusted.

In accordance with an embodiment of the lighting device, each light source comprises a collimator. Thereby the light output of the light sources can be more accurately directed towards the wavelength converting member.

In accordance with an embodiment of the lighting device, each light source comprises a mixing chamber, protruding up to the wavelength converting member, thereby preventing light from adjacent light sources from interfering with each other before reaching the wavelength converting member.

In accordance with an embodiment of the lighting device, the segmented optical member comprises a plate shaped element, which provides the segments as different portions of the plate shaped element. This is a simple and space saving solution.

In accordance with an embodiment of the lighting device, the first and second segment types are constituted by flat portions having different beam shaping properties. This is an advantageous way of providing different beam shapes with a flat element.

In accordance with an embodiment of the lighting device, the segmented optical member comprises several light-reflecting standing plates being arranged to cause different collimation of the passing light at said at least one segment of a first segment type and said at least one segment of a second segment type. In this embodiment the standing plates can be arranged directly on the wavelength converting member or on a supporting portion of the segmented optical member. The word standing is to be understood as being positioned perpendicular or with an oblique angle with respect to the member on which it is arranged.

In accordance with an embodiment of the lighting device, the standing plates are arranged with varying spacing between them.

In accordance with an embodiment of the lighting device, the standing plates have at least two different heights.

In accordance with an embodiment of the lighting device, the standing plates are arranged with at least two different angles between the plate and a geometric plane in which the wavelength converting member is primarily extending. The embodiments of the standing plates are usable in combinations as well. They all provide a collimating effect on the light passing the standing plates and control the beam width in a precise way.

In accordance with an embodiment of the lighting device, the segmented optical member comprises a diffuser arranged downstream of the plates. This is useful in particular when the standing plates are mounted directly on the wavelength converting member.

In accordance with an embodiment of the lighting device, the wavelength converting member comprises multiple phosphor layers.

These and other aspects, and advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the appended drawings in which:

Fig. 1 shows an example of a room with several lighting devices arranged at the ceiling;

Figs 2a-2e show an embodiment of the lighting device according to the present invention;

Figs 3-8 show further embodiments of the lighting device according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present lighting device is suitable for large area lighting. For instance, as shown in Fig. 1 several lighting devices 100 can be arranged at the ceiling of a room, where the light is output with two different beam shapes 102, 104. A first beam shape 102, which is rather narrow, provides work light, causing enough illumination for a work surface, such as a desk. A second beam shape 104 is wider and is used for background, or surrounding, light. If only the second beam shape 104 is used, a lighting profile as indicated by 109 is formed. It is to be noted, for interpretation purposes, that the device denoted by 100 in Fig. 1 and referred to as a lighting device could also be or be regarded as a luminaire comprising one or more lighting devices.

According to a first embodiment of the lighting device 200 it comprises multiple light sources 206, which are mounted on a carrier 208. Preferably, the light sources 206 are solid state light sources, such as LEDs (Light Emitting Diodes). The light sources emit light of a first wavelength range. The carrier 208 is a substrate such as a PCB (Printed Circuit Board). More particularly, the light sources 206 are mounted in a rectangular or square array having plural rows and plural columns of light sources 206.

A wavelength converting member 210 is arranged at a distance, for instance a few centimetres, from the light sources 206, and it comprises a first wavelength converting material configured to convert light of the first wavelength range into light of a second wavelength range. The wavelength converting material comprises a luminescent material such as an organic phosphor, inorganic phosphor or quantum dots, i.e. the wavelength converting member 210 is a phosphor element. Other materials are however feasible as well. The wavelength converting member 210 is plate shaped and flat. As a further alternative, the wavelength converting member 210 comprises multiple phosphor layers.

Downstream of the wavelength converting member 210, i.e. at a greater distance from the light sources 206, there is arranged a segmented optical member 212. In this embodiment, the segmented optical member 212 is plate shaped, and flat, and is arranged adjacent to the wavelength converting member 210. The segmented optical member 212 has several segments 214 of a first segment type, which provide a first beam shape, and several segments 216 of a second segment type, which provide a second beam shape, which his different from the first beam shape. More particularly, the segments are aligned with the light sources 206, such that each segment 214, 216 is aligned with a respective one of the light sources 206. In this embodiment the segments 214 of the first segment type are arranged side by side with the segments 216 of the second segment type in an alternating manner and forming e.g. a square segmented optical member 212, as shown in Fig. 2b. Of course any other shape, such as triangular, hexagonal, circular, etc. of the segmented optical member 212 is applicable. The segments can be of any suitable shape as well, such as triangular, hexagonal, etc. Each segment 214 of the first segment type provides a wide beam shape, and each segment 216 of the second type provides a narrow beam shape. Thereby, it is possible to use a single type of light source and still obtain very varied lighting conditions. When two adjacent light sources are driven at the same power level, the light source 206 aligned with a segment 216 of the second segment type provides a brighter light output suitable as work lighting, than the light source aligned with a segment 214 of the first segment type, which is suitable for surrounding lighting. This is illustrated in Fig. 1. By selectively turning on and off individual light sources 206 it is possible to control the lighting of a room and to save energy. Some examples of combinations of lighting are shown in Figs. 2c-2e. Furthermore, the light sources 206 are preferably dimmable, which further enhances the controllability of the lighting device 200.

The different segment types of the segmented optical member 212 are realized by means of flat portions of materials having different collimating and/or diffusing properties. In this embodiment, the segments 214 of the first segment type are not affecting the beam shape of the passing light at all, and they can be realized by simple holes or by a fully transparent material. The segments 216 of the second segment type are made of light shaping structures, which cause a significant collimation of the beam coming through segment 216. However, many alternative combinations are feasible and can be chosen on basis of the application of the lighting device 200.

In order to obtain the beam shaping properties, the segmented optical member 212 can have surface structures such as micro prisms, lenses etc. Brightness enhancement films (BEF) supplied by 3M are well known structures which can be used to collimate light. Such structures can therefore be used in the segmented optical member 212.

The main parts of the lighting device 200 described above, i.e. the carrier including the light sources, the wavelength converting member and the segmented optical member are mounted in a housing 218, shown most schematically in Fig. 2b. However, alternatively, the segmented optical member 212 can be attached to the wavelength converting member 210.

It should be noted that the segmented optical member 212 could be provided with more than two different types of segments if desired. Furthermore, the lighting device 200 can comprise control equipment for detecting human presence in an illuminated area and automatically adjust the lighting in dependence of the presence.

More particularly, as regards the wavelength converting member 210, examples of suitable organic phosphor materials are organic luminescent materials based on perylene derivatives, for example compounds sold under the name Lumogen® by BASF. Examples of suitable compounds include, but are not limited to, Lumogen® Red F305, Lumogen® Orange F240, umogen® Yellow F083, and Lumogen® F170.

Examples of inorganic phosphor materials include, but are not limited to, cerium (Ce) doped YAG (Y3A15012) or LuAG (Lu3A15012). Ce doped YAG emits yellowish light, whereas Ce doped LuAG emits yellow-greenish light. Examples of other inorganic phosphors materials which emit red light may include, but are not limited to ECAS and BSSN; ECAS being Cal-AlSiN3:Eux wherein 0<x<l, preferably 0<x<0.2; and BSSN being Ba2-x-zMxSi5-yAlyN8-yOy:Euz wherein M represents Sr or Ca, 0<x<l, 0<y<4, and 0.0005<z<0.05, and preferably 0<x<0.2).

Optionally, the luminescent material comprises a material showing quantum confinement and is at least in one dimension nano sized. Luminescent material like Quantum dots, quantum rods, wires tetrapod show quantum confinement, which means that they have size dependent optical properties. The materials are nano sized, which means that in at least one dimension their size is in the range from 0.5 nanometer to 100 nanometer, or, in another embodiment, in the range from 1 nanometer to 30 nanometer.

In accordance with a second embodiment of the lighting device, as shown in Fig. 3, the lighting device 300 comprises the same parts as the first embodiment, i.e. light sources 302 mounted on a carrier 304, a wavelength converting member 306 arranged at a distance from the light sources 302, and a segmented optical member 308, arranged downstream of the wavelength converting member 306, and more particularly arranged at a front surface thereof and adjacent thereto. Additionally this second embodiment of the lighting device 300 comprises collimators 310, and more particularly each light source 302 comprises a collimator 310. By means of the collimators 310 the light output of the light sources is more accurately directed towards the respective segments 312 of the segmented optical member 308. Each collimator 310 has preferably the shape of a trunchated cone and surrounds the light source 302, the narrower end of the collimator 310 being engaged with the carrier 304. Preferably, the collimators 310 are formed as reflectors, by means of a reflective sheet material or by means of an optical element of the TIR (Total Internal Reflector) type.

In accordance with a third embodiment of the lighting device, as shown in Fig. 4, the lighting device 400 comprises the same parts as the first embodiment, i.e. light sources 402 mounted on a carrier 404, a wavelength converting member 406 arranged at a distance from the light sources 402, and a segmented optical member 408, arranged downstream of the wavelength converting member 406. Additionally, each light source 402 comprises a mixing chamber 410, protruding up to the wavelength converting member 406. Thus it extends from the carrier 404 to the wavelength converting member 406, and abuts against the rear surface of the wavelength converting member 406. The mixing chamber 410 surrounds the very light emitting portion 412 of the source 402, and is square in cross- section, or another suitable shape like triangular hexagonal, and tube shaped and has a reflective surface. By aligning the mixing chamber 410 with the associated segment 412 of the segmented optical member 408, the light emitted from the light source cross-talk of light emitted by adjacent light sources 402 before reaching the segmented optical member 408 is largely prevented. Preferably, the mixing chamber is highly reflective and has a reflectivity of at least 80%, more preferably above 90%, and most preferably above 95%>.

In accordance with a fourth embodiment of the lighting device, as shown in Fig. 5, like the first embodiment the lighting device 500 comprises light sources 502 mounted on a carrier 504, a wavelength converting member 506 arranged at a distance from the light sources 502, and a segmented optical member 508, arranged downstream, seen in the propagation direction of the emitted light, of the wavelength converting member 506.

However, the segmented optical member comprises several light-reflecting standing plates 510 being arranged to cause different collimation of the passing light at said at least one segment of a first segment type and said at least one segment of a second segment type. Each segment of the first segment type is provided by a first set of standing plates 512. Each segment of the second segment type is provided by a second set of standing plates 514. The distance between the standing plates 510 differs such that the distance is greater between the standing plates of the first set of standing plates 512 than between the standing plates of the second set of standing plates 514. Consequently, the light beam output of the first set of standing plates 512 is wider than the light beam output of the second set of standing plates 514.

A fifth embodiment of the lighting device 600 is similar to the fourth embodiment, but instead of arranging the standing plates 610 at different distances, they are equidistantly arranged but have different heights, as illustrated in Fig. 6. The height varies continuously across the segmented optical member 608, thus providing a corresponding variation of beam shapes. Alternatively, the standing plates 610 are grouped in groups of the same length, while the length varies among the groups. The standing plates are attached to the front surface of the wavelength converting member 606. A sixth embodiment of the lighting device 700 is similar to the fourth embodiment, but instead of arranging the standing plates 710 at different distances, they are equidistant ly arranged but the standing plates 710 are arranged at the front surface of the wavelength converting member 706 with at least two different tilt angles α, β between the standing plate 710 and a geometric plane in which the wavelength converting member 706 is primarily extending. In this embodiment the size of the first angle a is 90°, and the size of the second angle β is e.g. 70°. Thus a first set of several standing plates 712 having an equal tilt angle a constitutes a segment of a first segment type providing a beam shape having a centre axis extending along a normal of the above-mentioned geometric plane, and a width which is dependent on the distance between the standing plates 710 and their height, just like in the fourth embodiment, and a second set of standing plates 714 having an equal tilt angle β constitute a segment of a second type providing a beam shape having a centre axis extending at the angle β to the geometric plane.

The standing plates used in the above-described embodiments are preferably diffuse reflecting elements. They can be made in various ways from plastic or metal, such as by injection molding a polymer comprising Ti0 ₂ , BaS04 or A1 ₂ 0 ₃ particles, or by coating a metal plate with white paint.

Furthermore, in all embodiments with standing plates they can be oriented in different directions to form other patterns than the parallel plate pattern shown in the figures. In other words, alternatively, the standing plates are arranged with at least one standing plate oriented in a different direction with respect to the other standing plates. More particularly, typical standing plate patterns are triangular, rectangular, or hexagonal boxes arranged side by side, such as hexagonal boxes forming a honeycomb pattern.

A seventh embodiment of the lighting device 800 is similar to the fourth embodiment, but the segmented optical member 808 additionally comprises a diffuser 816 arranged downstream of the standing plates 810, and thus downstream of the wavelength converting member 806.

Above embodiments of the lighting device according to the present invention as defined in the appended claims have been described. These should merely be seen as non- limiting examples. As understood by the person skilled in the art, many modifications and alternative embodiments are possible within the scope of the invention as defined by the appended claims. For instance, in all embodiments the wavelength converting member is shown to be a uniform layer but it goes without saying that this member can also be patterned to have light conversion layers with different emission characteristics.

It is to be noted that for the purposes of his application, and in particular with regard to the appended claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality, which per se will be evident to a person skilled in the art.