FIELD OF THE INVENTION

The invention relates to a light generating device and a luminaire comprising such light generating device.

BACKGROUND OF THE INVENTION

LED panels are known in the art. US8220962, for instance, describes a LED streetlamp, in particular a structure of a reflector panel of the LED lamp. A reflector panel comprises a base, the base has multiple reflector cups, which are divided into two groups according to the direction of their openings, all reflector cups in each group have the same direction of their openings, the directions of the openings of the reflector cups in two different groups are opposite. The reflector cup comprises the top, bottom, and the reflector part that connects the top and bottom, the said reflector part consists of an inner transverse face, an outer transverse face, an inner vertical face and an outer vertical face; the said inner transverse face and outer vertical face are planes, the said inner vertical face and inner transverse face are curved planes.

SUMMARY OF THE INVENTION

In office lighting, the LED light is usually homogenized by the optics (for instance a light guide panel or indirect lighting) to create lines or areas of light. However, luminaires with point light sources may also be conceivable. However, it appears that glare and/or strongly non-uniform luminance distributions are not desired by users. Amongst others, it appears that direct view of bright point sources for people that glance up into the luminaire may be uncomfortable.

Hence, it is an aspect of the invention to provide an alternative light generating device, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

In an aspect, the invention provides a light generating device comprising (i) a plurality of N light sources and (ii) shielding elements. Especially, the light sources have light emitting surfaces having dimensions (d) of at maximum 3 mm. Further, in embodiments the light sources comprise solid state light sources. Further, the light sources are configured to generate light source light. Especially, in embodiments the light sources are configured to generate the light source light in a first operational mode of the light generating device with an average a luminous flux selected from the range of up to 10 lm, such as up to 8 lm, even more especially up to 6 lm, such as selected from the range of 0.01-6 lm. Further, in specific embodiments the light emitting surfaces may have a pitch (p) selected from the range of 0.5- 24 mm, especially 3-12 mm. Especially, in embodiments p>d. Further, in specific embodiments the shielding elements define cavities for the light sources. Especially, the shielding elements are configured to prevent a direct view of the light emitting surfaces under first angles (a) with normals to the light emitting surfaces, wherein in specific embodiments the first angles (a) are selected from the range of 65-90°, especially selected from the range of 60-90°. Hence, the invention especially provides in embodiments a light generating device comprising (i) a plurality of N light sources and (ii) shielding elements, wherein: (a) the light sources have light emitting surfaces having dimensions (d) of at maximum 100 pm, wherein the light sources comprise solid state light sources, wherein the light sources are configured to generate light source light, especially wherein the light sources are configured to generate the light source light in a first operational mode of the light generating device with an average a luminous flux selected from the range of 0.01-6 lm, and wherein the light emitting surfaces have a pitch (p) selected from the range of 0.5-24 mm, wherein p>d; and (b) the shielding elements define cavities for the light sources, wherein the cavity walls are diffuse reflective or specular reflective and wherein the shielding elements are configured to prevent a direct view of the light emitting surfaces under first angles (a) with normals to the light emitting surfaces, wherein first angles (a) are selected from the range of 65-90°.

With such light generating device, a desirable sparkle effect may be created while glare discomfort can essentially be prevented. Further, with such lighting device large areas may be illuminated with functional light, whereas when directly observing the light generating device, a desirable and user friendly sparkle effect may be observed. The light generating device may provide light according to glare requirements for indoor workplaces. Hence, especially the combination of LED pitch, LED flux and shielding angle ensures compliance with glare norms, as well as a sparkly, non-glary appearance of the LED points when viewed directly.

As indicted above, the light generating device comprises a plurality of N light sources, with N>16, even more especially N>64, yet even more especially N>100. In yet further embodiments, N>4096, such as N>10,000, though N>100,000 may also be possible. The term “lighting device” may also refer to a plurality of functionally coupled lighting devices. Hence, the term “lighting system” (see further also below) may refer to a plurality of functionally coupled lighting devices, each e.g. having 4096 solid state light sources. Even more especially, N may be selected from the range of 16-4,000,000, such as selected from the range of 16-100,000, especially selected from the range of 32-16,000.

The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc.. The term “light source” may also refer to an organic light-emitting diode, such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid state light source (such as a LED or laser diode). In an embodiment, the light source comprises a LED (light emitting diode). The term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chips-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of semiconductor light sources may be configured on the same substrate.

In embodiments, a COB is a multi LED chip configured together as a single lighting module. The light sources may comprise one or more of mini LEDs and micro LEDs. Especially, in embodiment the light sources comprise micro LEDs or “microLEDs” or “pLEDs”. Herein, the term mini size or mini LED especially indicates to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm - 1 mm. Herein, the term p size or micro LED especially indicates to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm and smaller. MicroLEDs are especially LEDs with submillimeter size, like a (circular equivalent) diameter selected from the range of about of 10-100 pm. Also a mini LED or micro LED may be provided with a luminescent material (layer). The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources. In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid state light source, such as a LED. In embodiments, the light source may comprise a LED with on-chip optics. The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid state light sources selected from the same bin.

The light sources have light emitting surfaces. The term “light emitting surface” may refer to a die, especially in embodiments wherein essentially downstream of the light emitting surface there are no further optics or light converting material. Hence, would an observer directly observe the die of a solid state light source, then the die may be the light emitting surface. However, downstream of a solid state light source, there may in specific embodiments be optics. Hence, would an observer directly observe the optics, then the optics is (are) or provide the light emitting surface. However, downstream of a solid state light source, there may in embodiments be a light converter material. Hence, would an observer directly observe the light converter material, then the light converter material is or provides the light emitting surface. Hence, essentially an end face from which the light source light emanates is the light emitting surface. Therefore, especially in embodiments the light generating device does not comprise further optics downstream of the light emitting surfaces, like a homogenizer, or other optical elements, except for the shielding elements. In embodiments, there may be only a light transparent exit window. Hence, especially in the angular range of 0-60° downstream of the light emitting surface, there are no optical elements, except for a light transparent exit window. An example of a shielding element is a louvre.

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”.

Especially, in embodiments the light sources have light emitting surfaces having dimensions (d) of at maximum 3 mm. This implies that the solid state light sources are relatively small. The sizes of the light emitting surface of the solid state light sources are in embodiments at maximum 3 mm, but may in the case of some embodiments with luminescent material and/or optics be smaller, or even much smaller, like at maximum 1 mm, such as selected from the range of 10-100 pm. Especially, the apparent source (i.e. as perceived by an observer) may have sizes of at maximum 3 mm.

As indicated above, the term “light source” especially refers to a solid state light source, especially a small solid state light source, such as having a mini size or micro size. For instance, the light sources may comprise one or more of mini LEDs and micro LEDs. Especially, in embodiment the light sources comprise micro LEDs or “microLEDs” or “pLEDs”. Herein, the term mini size or mini LED especially indicates to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm - 1 mm. Herein, the term p size or micro LED especially indicates to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm and smaller.

The term “dimensions (d)” may refer to length and width, or to diameter(s). it may especially refer to dimensions in a plane parallel to the light generating device. It appears that dimensions over about 3 mm may lead to more discomfort, such as at customary distances selected from the range of 2-6 m, whereas dimensions of 3 mm or smaller, the sparkle effect may be appreciated. Smaller dimensions may even be more desirable. Hence, in specific embodiments the light sources have light emitting surfaces having dimensions (d) of at maximum 2 mm, such as at maximum 1 mm.

As indicated above, the light sources are configured to generate light source light. In embodiments this may refer to colored light of a solid state light source, i.e. of the bare solid state light source die. Alternatively or additionally, this may be the light of a luminescent material. As indicated above (and further elucidated below), one or more light sources may comprise a luminescent material. The solid state light source is configured to generate solid state light source light. The luminescent material may convert at least part of the solid state light source light into luminescent material light. The luminescent material light may be white light or colored light. In embodiments, the combination of solid state light source light and luminescent material light from a single light source may provide white light source light.

Further, it appears that the desired sparkle effect may essentially only obtained when the luminous flux of the light sources is not too high, especially not over about 10 lumen, like at maximum 8 lumen, even more especially not over about 6 lumen. As will be further elucidated below, the light sources may all generate the same type of light, but in other embodiments two or more light sources may generate different types of light. Hence, the luminous flux may be averaged over the light sources. Therefore, in specific embodiments the light sources are configured to generate the light source light in a first operational mode of the light generating device with an average a luminous flux selected from the range of up to 10 lm, such as up to 8 lm, even more especially up to 6 lm, such as at least 0.01, such as at least 0.1 lm, like at least 0.3 lm. Especially, however, essentially none of the light sources may in the first operational mode provide a luminous flux over 10 lumen (lm), such as not over 8 lumen. Further, especially the lowest luminous flux is at least about 0.1 lumen. Especially, in such embodiments the pitch is at least about 3 mm.

As indicated above, the luminous flux should not be too high. Especially, the average luminous flux is even a bit lower than the above indicated 6 lm. Hence, in specific embodiments the light sources may be configured to generate the light source light in the first operational mode of the light generating device with an average a luminous flux selected from the range of 0.1-3 lm, like especially 0.5-3 lm. This may be perceived as even more comfortable sparkly.

Here, the term “first operational mode” is used. In embodiments, the light sources may be controllable (in power). In such embodiments, there may a first operation mode wherein the luminous flux is as indicated herein. This does not exclude that there are other operational modes wherein the maximum luminous flux and/or average luminous flux is different than described herein. The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface. The control system may also be configured to receive and execute instructions form a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc.. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system. Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, WIFI, ZigBee, BLE or WiMAX, or another wireless technology. The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation”. The term “mode” may also be indicated as “controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed. However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability). Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme.

The plurality of light sources are especially configured in an array. The array may be a ID array or a 2D array. Especially, the light sources are configured in a 2D array. The array may be regular, random, or quasi random. Distances between (nearest) neighbors are especially selected from the range of 0.5-24 mm, such as 1-24 mm, such as 3-24 mm. Even more especially, distances between (nearest) neighbors are especially selected from the range of 0.5-12 mm, such as 1-12 mm, such as 3-12 mm. Especially, the array is regular ID array or a regular 2D array, even more especially a 2D array. A 2D array may have a single pitch or two pitches (in different directions). Here below, the invention is further especially described in relation to regular arrays with one or two pitches. When there are two pitches, for each pitch applies the herein described conditions for the pitch. Further, to obtain the desired sparkle effect it appears that the light sources (or more precisely their light emitting surfaces) should not be configured to close to each other, but should also not be configured to far from each other. It especially appears that a pitch smaller than about 30 mm, even more especially equal to or smaller than 24 mm is desirable. Hence, in specific embodiments the light emitting surfaces have a pitch (p) selected from the range of 0.5-24 mm. Even more desirable may be embodiments wherein the light emitting surfaces have a pitch (p) selected from the range of 0.5-12 mm, like 1-12 mm, such as especially 3-12 mm. For instance, in embodiments the pitch may be at least 1 mm, like at least 3 mm. As will be clear from the above, especially p>d, especially p>2*d. In these equations, the parameter d especially refers to the dimension along the pitch direction.

As also indicated above, the light generating device comprises shielding elements. The shielding elements are especially configured to reduce (direct) glare, especially over angles of about 70°, even more especially over angles of about 65°, even more especially over angles of about 60°. Hence, in specific embodiments the shielding elements are configured to prevent a direct view of the light emitting surfaces under first angles (a) with normals to the light emitting surfaces, wherein first angles (a) are selected from the range of 70-90°, especially selected from the range of 65-90°. This implies that under angles in the range of 70-90°, especially selected from the range of 65-90° with the normal, an observer cannot observe (directly) the light emitting surfaces. Even more especially, the first angles (a) are selected from the range of 65-90°. Yet even more especially, the first angles (a) are selected from the range of 60-90°, such as selected from the range of 55-90°, or even 50-90°, such as 45-90°. Note that the term “light emitting surfaces” does not imply that the respective light source is necessarily always switched on. Hence, especially the shielding elements define cavities for the light sources.

The shielding elements and some further specific embodiments are further elucidated below.

When luminescent material is available, it may be provided as layer on a die, it may be provided as remote layer, or it may be provided as (remote) body. As indicated above, a face of such luminescent material may thus provide the light emitting surface. The term “luminescent material” especially refers to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the second radiation has a spectral power distribution at larger wavelengths than the first radiation, which is the case in the so-called down- conversion. In specific embodiments, however the second radiation has a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up-conversion.

In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and/or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation and blue radiation, into visible light. The luminescent material may in specific embodiments also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. In general, the luminescent material will be a down converter, i.e. radiation of a smaller wavelength is converted into radiation with a larger wavelength ( _eX < _em ), though in specific embodiments the luminescent material may comprise down-converter luminescent material, i.e. radiation of a larger wavelength is converted into radiation with a smaller wavelength ( _ex > _em ).

In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and/or fluorescence. The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below.

In embodiments, luminescent materials are selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc.

In specific embodiments, the term “luminescent material” may also refer to a material comprising the luminescent material. For instance, a converter material may comprise a luminescent material. For instance, a light transmissive body may comprise a luminescent material embedded therein.

Hence, in embodiments the solid state light sources have light emitting surfaces, wherein one or more of the light sources further comprise a layer on the light emitting surface of the solid state light source, wherein the layer comprises a luminescent material, and wherein the layer (i.e. a luminescent material comprising layer) defines the light emitting surface of the light source. The luminescent material comprising layer may be relatively thin, like e.g. equal to or smaller than 250 pm, such as at least about 25 pm, like selected from the range of 25-150 mih. This may allow a relatively thin light generating device and/or may provide relatively small light emitting surfaces.

In embodiments, this may apply to all light sources. In yet other embodiments, only a subset (i.e. smaller than N) of the light sources may comprise such layer on the light emitting surface. In embodiments, all layers are essentially the same. In yet other embodiments, two or more layers may differ in e.g. composition and or thickness. In this way, different colors and/or color points, and/or color temperatures may be provided.

Alternatively or additionally, in embodiments the solid state light sources have light emitting surfaces, wherein the light generating device further comprises one or more light converter elements, each configured downstream of a respective solid state light source, wherein the light converter elements comprise a luminescent material, wherein the light converter elements have cross-sectional dimensions larger than the solid state light sources configured upstream of the light converter elements, and wherein the light converter elements define the light emitting surfaces of one or more of the light sources comprising the light converter elements. In embodiments, the light converter elements may be converter bodies, like small plates or small cubes or small cylinders, etc. etc. Light converter elements may be easier to handle and/or thermal dissipation may be easier.

In embodiments, this may apply to all light sources. In yet other embodiments, only a subset (i.e. smaller than N) of the light sources may comprise such light converter element on the light emitting surface. In embodiments, all light converter elements are essentially the same. In yet other embodiments, two or more 1 light converter elements may differ in e.g. composition and or thickness. In this way, different colors and/or color points, and/or color temperatures may be provided.

As indicated above, in embodiments the shielding elements may define cavities for the light sources. The light source light of the light source in the cavity may essentially only escape via an opening defined by the cavity. In this way, desirable glare conditions can be met. As indicated above, the shielding elements are configured to prevent a direct view of the light emitting surfaces under first angles (a) with normals to the light emitting surfaces, wherein first angles (a) are selected from the range of 70-90°. In other words, the cavities may (thus) be configured to prevent a direct view of the light emitting surfaces under first angles (a) with normals to the light emitting surfaces, wherein first angles (a) are selected from the range of 70-90°, or 65-90°, or even 60-90°. As will be clear from the above, especially each cavity includes a single light emitting surface. Therefore, in embodiments each cavity may host a single light source. Especially, in embodiments shortest distances between neighboring light sources are equal to (or larger than) about p-d (i.e. the pitch minus the dimension). Further, in specific embodiments all cavities have essentially the same dimensions and all cavities host the same type of light source.

As indicated herein, the cavity is especially reflective for the light source light. The shielding elements are especially used to shape a beam of light escaping from the cavity.

The shielding elements may be provided by a plate-like element. Such plate like element may include openings wherein the light sources may be configured. In this way, walls of the openings may provide the desired shielding. Hence, in embodiments the light generating device may further comprise a plate-like element, wherein the plate like element comprise the cavities. The plate-like element may comprise a light transmissive, or even light transparent material. Hence, in embodiments the plate-like element may have light guiding or waveguiding properties.

Especially, at angles about equal to or larger than 65°, there may be no direct view to the light source, such as a LED, but only indirect via the light guide that either creates a diffuse blob of light or a distribution of tiny virtual sources spread over a larger area (depending on whether the light outcoupling of the light guide is diffuse (paint dots, roughness) or specular (facets, V-grooves, guide edges)). In specific embodiments, the walls of the openings may have a diffuse reflective surface (like in embodiments holes in a white opaque plate). Alternatively, in specific embodiments, the walls of the openings may be provided by a diffuse transmissive surface (like holes in a light guide that is volume scattering by particles in the guide, or by surface scattering on all surfaces (e.g. sandblasted or etched), etc.

Alternatively or additionally, shielding elements may be provided by structures extending from a support, like a checkerboard configuration of shielding elements, or a honeycomb configuration of shielding elements, etc.. Hence, in embodiments the light generating device may further comprise a support configured to support the plurality of N light sources and the shielding elements. A part of the support may be reflective for the light source light.

The shielding elements may be reflective for the light source light. Hence, the shielding elements may comprise a light reflective material and/or may be configured under light reflective conditions (such as under angles larger than the critical angle).

Hence, in specific embodiments the cavities have cavity walls, wherein the cavity walls are diffuse reflective. Alternatively, the cavity walls may be specular reflective. The former embodiments may provide a more robust solution. The latter embodiments may provide more control of the reflected light.

Further, for desirable sparkling effect it may also be useful when the light emitting surfaces and the shielding elements have a minimum distance of about at least 0.5 mm, such as at least about 1 mm. Hence, in embodiments the light emitting surfaces have a shortest distance (dl) to the shielding elements, wherein dl > 1 mm.

In embodiments, the light generating device may be (essentially) rigid. In yet other embodiments, the light generating device may be flexible. In embodiments, the light generating device is planar. However, in yet other embodiments the light generating device is ID or 2D curved.

In embodiments, one or more light sources may be controllable in power. Further, when there is a plurality of light sources, it may be possible to control whether or not one or more light sources are switched on or off. In specific embodiments, one or more light sources may be individually controllable. Therefore, in specific embodiments the light generating device may be functionally coupled to or comprise a control system. Especially, in embodiments the light generating device may further comprise a control system configured to control the plurality of N light sources. Further, when there are more than one light sources, it may in principle also be possible to not only control intensity of the light generated by the light generating device, but in specific embodiments also to control one or more other lighting properties, such as selected from the group consisting of color point, color temperature, color rendering.

The term “individually controllable” may especially indicate that the individually controllable light source or subset of light sources may be switched from an off- state to an on-sate (or vice versa) and/or may be dimmed in intensity. The latter may e.g. refer to a stepwise or stepless up dimming (increasing intensity) or down dimming (decreasing intensity). In such embodiments, the one or more individually controllable light sources or subset of light sources may provide a dimming range of the light source light. In yet other embodiments, both options may be applied (on different controllable subsets). Hence, in embodiments the lighting device light is thus also controllable in intensity. As indicated above, in specific embodiments the lighting device light is thus also controllable in one or more of color point, color temperature, color rendering, etc. The terms “device light” or “lighting device light”, and similar terms, refer to the light emanating from the light generating device. Such device light comprises the light source light of one or more light sources. Especially, in embodiments the light generating device is configured to generate white light in the first operation mode. 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 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700-20000 K, for general lighting especially in the range of about 2700 K and 6500 K. In embodiments, for backlighting purposes the correlated color temperature (CCT) may especially be in the range of about 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is 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. However, it is not excluded that in the first operation mode the light generating device generates colored light.

Especially, the light generating device is configured to provide at least visible light. The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm.

In yet a further aspect, the invention also provides a luminaire comprising the light generating device as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... Especially, when the optical element would include a cover plate, such optical element may be essentially transparent.

Yet further, in an aspect the invention provides an indoor workplace lighting system, such as an office lighting system, comprising the light generating device as defined herein or the luminaire as defined herein. Such indoor workplace lighting system may further comprise a control system (see also above) for controlling the light generating device(s). Especially, the indoor workplace lighting system comprises a plurality of light generating devices (and the control system).

The lighting device may be part of or may be applied in e.g. office lighting systems (see also above), 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, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. 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:

Figs la-lf schematically depicts some aspects;

Fig. 2 schematically depicts an embodiment of a luminaire; and Fig. 3 depicts some limitations on the LED flux and LED pitch. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

LED luminaires may need measures to reduce the average luminance at large angles (like reflectors or lenses) to comply with (shielding, direct and indirect glare) norms, but aside from the glare norms, the direct view of bright point sources for people that glance up into the luminaire may also be uncomfortable.

MicroLEDs may become the basis for low-cost large-area sources that consist of many small bright points. The combination of low-cost point source arrays and point sources with a flux that is an order of magnitude lower than low power LEDs surprisingly appears to solve discomfort related to uncovered point architectures.

Amongst others, in a subset of embodiments a planar light source (may be flexible) containing microLEDs on a substrate at a LED pitch smaller than 24 mm, with a LED flux less than 6 lm, but preferably with a pitch smaller than 12 mm and a LED flux less than 3 lm is proposed. In the pitch range 8-12 mm and a flux range 0.5-3 lm various luminaire types (ranging low glare to e.g. glare acceptable for corridors) may be constructed with a sparkly, non-glary appearance in foveal view, but a uniform appearance in peripheral view. In specific embodiments, the LEDs are shielded from view at angles beyond -60° (e.g. an angle selected from 45-65°) by a diffuse shield that is diffuse reflective (may also be partly diffusely transmissive). The combination of LED pitch, LED flux and shielding angle may ensures reduction or absence of (undesired) glare and may provide a sparkly, non-glary appearance of the LED points when viewed directly.

In embodiments, a substrate is provided with a square, hexagonal or even slightly irregular array of microLEDs with an average luminous flux per LED f and an average LED pitch w. The microLEDs may be phosphor converted white light emitting as separate packages, or blue (or UV) emitting microLEDs on a substrate, with a second, white reflecting layer with holes that can be filled with light conversion material (phosphor). In between the microLEDs there are reflecting walls to shield the LEDS from viewing at angles of e.g. 60 degrees to the vertical or larger. The reflecting walls may be tapered or straight, see the drawings.

In a specific embodiment, the source (e.g. micro LED with phosphor) may have a diameter less than 3 mm, or preferably even less than 1 mm to ensure a sparkling appearance in direct view. Furthermore, a separation distance between the source and the closest part of the shielding wall of in embodiments at least 2 mm may make sure that the source is in direct view a separate bright point: at a closer distance the bright part of the walls may blend in with the source to form a larger, more glary source. This less desired situation might occur in the top embodiment in Fig. le.

Fig. la may schematically depict a white phosphor converted micro LED on a substrate (rectangular, square, or hexagonal array, with pitch p). Diffuse reflection (optionally partially diffuse transmissive) glare shield, either a mesh or a sheet with (optionally tapered) holes may be applied.

Fig. la schematically depicts an embodiment of a light generating device 1000 comprising a plurality of N light sources 100 (here by way of example N=4) and shielding elements 200. Especially, however N>16.

The light sources 100 have light emitting surfaces 105 having dimensions d of in embodiments at maximum 3 mm. The light sources 100 comprise solid state light sources 110. The light sources 100 are configured to generate light source light 101.

The light sources 100 are configured to generate the light source light 101 in a first operational mode of the light generating device 1000 with an average a luminous flux selected from the range of up to 10 lm, such as up to 8 lm, even more especially 0.01-6 lm. In embodiments, the light sources 100 are configured to generate the light source light 101 in the first operational mode of the light generating device 1000 with an average a luminous flux selected from the range of 0.1-3 lm.

The light emitting surfaces 105 have a pitch p selected from the range of 0.5- 24 mm, such as at least about 3 mm. As shown, p>d. In embodiments, the light sources 100 have light emitting surfaces 105 having dimensions d of at maximum 2 mm. Further, in embodiments the light emitting surfaces 105 have a pitch p selected from the range of 3-12 mm. The light emitting surfaces 105 may have a shortest distance dl to the shielding elements 200, wherein in specific embodiments dl > 1 mm. For instance, in specific embodiments dl > 2 mm. The shielding elements 200 define cavities 210 for the light sources 100. Especially, the shielding elements 200 are configured to prevent a direct view of the light emitting surfaces 105 under first angles a with normals 106 to the light emitting surfaces 105. In embodiments, the first angles a are selected from the range of 65-90°, such as from the range of 60-90°. The cavities 210 have cavity walls 211. In embodiments, the cavity walls 211 are diffuse reflective. The light generating device 1000 may further comprise a support 420 configured to support the plurality of N light sources 100 and the shielding elements 200. The light generating device 1000 may further comprise a control system 300 configured to control the plurality of N light sources 100.

Fig. lb schematically depicts a similar device 1000 as schematically depicted in Fig. la. Especially, as indicated above, the solid state light sources 110 have light emitting surfaces 115. In embodiments, the light generating device 1000 further comprises one or more light converter elements 135, each configured downstream of a respective solid state light source 110. The light converter elements 135 comprise a luminescent material 120. In embodiments, the light converter elements 135 have cross-sectional dimensions larger than the solid state light sources 110 configured upstream of the light converter elements 135. Especially, the light converter elements 135 define the light emitting surfaces 105 of one or more of the light sources 100 comprising the light converter elements 135.

Fig. lb also schematically depicts an embodiment of the light generating device 1000 further comprising a plate-like element 410, wherein the plate like element 410 comprise the cavities 210.

Fig. lc schematically depict a few possible embodiments wherein the light source 100 comprises a solid state light source 110 and a luminescent material 120. The solid state light source 110 is configured to generate solid state light source light 111, of which at least part is converted by the luminescent material 120 into luminescent material light. In embodiments, the light source light 101 may comprise at least luminescent material light, and optionally also (unconverted) solid state light source light 111. In the drawing on the left, the solid state light source 110 may have a light emitting surface 115. The light source 100 further comprise a layer 125 on the light emitting surface 115 of the solid state light source 110. The layer 125 comprises a luminescent material 120. The layer 125 defines the light emitting surface 105 of the light source 100.

In the embodiments in the middle and on the right, the light source 100 further comprises a light converter element 135 configured downstream of the solid state light source 110. The light converter elements 135 comprise a luminescent material 120. In embodiments, the light converter elements 135 have cross-sectional dimensions larger than the solid state light sources 110 configured upstream of the light converter elements 135. Especially, the light converter elements 135 define the light emitting surfaces 105 of one or more of the light sources 100 comprising the light converter elements 135. In the embodiment in the middle, the luminescent material 120 is configured remote from the solid state light source 110; in the embodiment on the right, the solid state light source 110 is at least partly embedded in the converter element 135.

Fig. Id schematically depict some possible shapes of the light emitting surface 105, and their dimensions d. In the left, a square light emitting surface 105 is depicted, where the height H and the width W are dimensions d. In the middle, a hexagonal light emitting surface 105 is depicted, where the height H and the width W are dimensions d. On the right, a circular light emitting surface 105 is depicted, where the diameter D is the dimension d.

Fig. le schematically depict several possible shapes of the shielding elements 200. However, more shapes may be possible, like curved shapes. Reference d2 indicates the width of the shielding element 200.

Fig. If schematically depicts an embodiment of a luminaire 2 comprising the light generating device 1000. Here, by way of example circular cavities 210, but also a rectangular cavity 210, (are) is schematically depicted.

Fig. 2 schematically depicts an embodiment of a luminaire 2 comprising the light generating device 1000. For instance, the luminaire 2 may be an indoor workplace lighting system or may be comprised by a workplace lighting system. Hence, an indoor workplace lighting system may comprise the light generating device 1000 or the luminaire 2. An example of a workplace lighting system is an office lighting system. Reference 1001 indicates the device light of the light generating device 1000. The device light 1001 comprises the light source light of one or more light sources. During the first operational mode, the device light 1001 may thus comprise the light source light of all active light sources. Reference 301 indicates a user interface. Examples of user interface devices include a manually actuated button, a display, a touch screen, a keypad, a voice activated input device, an audio output, an indicator (e.g., lights), a switch, a knob, a modem, and a networking card, among others. Especially, the user interface device may be configured to allow a user instruct the device or apparatus or system, with which the user interface is functionally coupled or by with the user interface is functionally comprised. The user interface may comprise a graphical user interface. The term “user interface” may also refer to a remote user interface, such as a remote control. A remote control may be a separate dedicate device. However, a remote control may also be a device with an App configured to (at least) control the system or device or apparatus. A user interface is especially functionally coupled to the control system or may be comprised by the control system.

For very small sources, the experience of glare and sparkle may be essentially independent of the actual size of the source. It may essentially only depend on the intensity of the source, which for Lambertian sources may be directly related to the source flux. — |It surprisingly appears that in a relatively dark room, tiny sources are more likely to be perceived as sparkly rather than glary when the source flux is e.g. equal to or less than 3 lm. Further, it appears that in a brightly lit room (typical for offices), this maximum acceptable flux may increase to about 6 lm.

Fig. 3 depicts the luminous flux (in lumen) versus the pitch p (in mm). It appears that when luminous fluxes over the line FMB are chosen, that the light generating device is considered glary in direct view. It also appears that when pitches larger than the line DPR are chosen, the light generating device is considered non-uniform in peripheral view. Hence, in specific embodiments the invention is at least defined by the lines FMB and DPR, and especially also by the line FR. Then, glare may be low or absent, and sparkling is desirable. Especially, at pitches p smaller than FR, the luminaire essentially always appear uniform at typical viewing distances (3 meter), even in foveal view.

Further, it appears that the area defined by FMD, FMB and PR (and FR) may provide light generating devices with sparkling in direct foveal view in a bright room and may be perceived uniform in peripheral view.

Further, it appears that the area defined by FMD, FMB, PR, and DPR may provide light generating devices with sparkling in direct foveal view in a bright room and may be experienced as acceptably uniform in peripheral view (though less uniform than at pitches smaller than the line indicated PR).

Yet further, it appears that the area defined by FMD, PR, and DPR (and the horizontal axis) may provide light generating devices with sparkling in direct foveal view and may be experienced as acceptably uniform in peripheral view.

Yet further, it appears that the area defined by FMD and PR (and FR) may provide light generating devices which are sparkling in direct foveal view and are experienced as uniform in peripheral view. Hence, a pitch of at maximum 12 mm and a flux of at maximum 3 lm appears to provide best results. Further, best results may in embodiments be obtained between the lines F22 and FI 6. Best results are obtained in embodiments between F 19 and FI 6, especially between FI 9, F16 and FMD. The curves FI 6, F19 and F22 indicate the combinations of LED flux and LED pitch for which the UGR (Unified glare rating) value of a luminaire according to the invention is 16, 19 or 22. These curves are drawn for a specific embodiment in which the device is 575 by 575 mm ² , a typical office luminaire size, and in which a diffuse reflecting tapered glare shield was applied.

Those skilled in the art will realize that the UGR value may change when the luminaire size or details of the glare shield are varied, though the herein indicated range may still give good results when the luminaire size and/or details may change.

For office lighting, especially the area between F19 and F16 may be relevant and perceived pleasant by users. The area between F22 and F19 may especially be relevant for applications where users do not stay for longer periods, like corridors, hallways, etc.

The term “plurality” refers to two or more.

The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” 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%.

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, apparatus, or systems may herein amongst others be 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, apparatus, or systems 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. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

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 a device claim, or an apparatus claim, or a system 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 also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or system 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. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.