Tunable beam combining laser phosphor engine

Abstract

The invention provides a light generating system (1000) comprising a first light generating device (110), a second light generating device (120), a luminescent material (200), a diffuser element (710), and optics (500); wherein - the optics (500) comprise (a) a first beam splitter arrangement (1500), configured between the first light generating device (110) and the luminescent material (200), and (b) a second beam splitter arrangement (2500), configured between the second light generating device (120) and the diffuser element (710); - the first light generating device (110) is configured to generate first device light (111), having a first peak wavelength λ1; the second light generating device (120) is configured to generate second device light (121), having a second peak wavelength λ2; - wherein one of the beam splitter arrangements (1500,2500) is configured to combine the luminescent material light (201) and diffused second device light (711) received by that beam splitter arrangement; - the optics (500) comprise (c) a first lens arrangement (1510), configured between the first beam splitter arrangement (1500) and the luminescent material (200), and (d) a second lens arrangement (1520), configured between the second beam splitter arrangement (2500) and the diffuser element (710); - the optics (500) comprise (e) a primary angular spreader (TD11), configured between the first light generating device (110) and the first lens arrangement (1510), and (f) a secondary angular spreader (TD12), configured between the second light generating device (120) and the second lens arrangement (1520); - the light generating system (1000) is configured to generate system light (1001) comprising one or more of luminescent material light (201) and diffused second device light (711).

Description

[0001] TUNABLE BEAM COMBINING LASER PHOSPHOR ENGINE

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a light generating system. The invention further relates to a lighting device comprising such light generating system.

[0004] BACKGROUND OF THE INVENTION

[0005] Laser-phosphor based stage lighting engines are known in the art. For instance, WO2022143318 describes a light emitting device, comprising a first light source, a second light source, a dichroic mirror, a wavelength conversion apparatus, a first light path adjusting apparatus or a second light path adjusting apparatus, and a first scattering optical system. The light mixing effect of emergent light can be improved by using the first scattering optical system. Light emitted by the first light source is all used for exciting the wavelength conversion apparatus.

[0006] SUMMARY OF THE INVENTION

[0007] High brightness light sources can be used in various applications including spots, stage-lighting, headlamps, home and office lighting, and automotive lighting. For this purpose, laser-phosphor technology can be used, wherein a laser provides laser light and a remote phosphor converts laser light into converted light. A relatively straightforward way to produce white light using lasers is to use laser light in combination to generate phosphor converted light. Laser-phosphor systems may allow generation of high brightness light and may therefore be used in projection systems, including displays such as cinema projectors and projectors for home, school, and office applications, car front lighting, search lighting, stage lighting, architectural lighting, and special lighting applications. However, such light engine may be capable to generate only a single color point as defined by the luminescent converter. Creation of a product range providing different color points may be difficult as it may require multiple unique components to be designed, qualified, produced, and kept in stock. In other cases, e.g. in RGB LCD-based projection systems, the maximum brightness may be limited by the components used, the engine volume may be large due to the many components, and the system cost may be high due to the many dedicated components. A way to combine pump light and luminescent light may be to use a polarizing beam splitter for the pump light, by which part of the light is reflected to the luminescent material and part is transmitted to a diffuser. However, in general the diffused light may to a large degree be depolarized, which may result in relatively high losses of diffused blue light at the beam combiner where it is combined with the luminescent light into white output light.

[0008] Hence, it is an aspect of the invention to provide an alternative light generating system, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as an objective to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0009] According to a first aspect, the invention provides a light generating system (“system”) comprising a first light generating device, a second light generating device, a luminescent material, a diffuser element, and optics. Yet, the light generating system may comprise a control system. Especially, the optics may comprise a first beam splitter arrangement. The first beam splitter arrangement may be configured between the first light generating device and the luminescent material. Further, the optics may comprise a second beam splitter arrangement. The second beam splitter arrangement may be configured between the second light generating device and the diffuser element. Further, the first light generating device may especially be configured to generate first device light. The first device light may have a first peak wavelength Al . In embodiments, the first light generating device comprises a first solid state light source. Further, the second light generating device may especially be configured to generate second device light. The second device light may have a second peak wavelength X2. In embodiments, the second light generating device comprises a second solid state light source. In embodiments, the optics and the second light generating device may be configured such that the second device light, wherein incident on the second beam splitter arrangement , comprises polarized light having a p-polarization or an s-polarization. Further, in embodiments the luminescent material may especially be configured to convert first device light received by the luminescent material into luminescent material light. Yet, in embodiments the diffuser element may be configured to diffuse at least part of the second device light received by the diffuser element thereby providing diffused second device light. Especially, however, the diffuser element may be configured to diffuse at least part of the second device light received by the diffuser element thereby providing diffused second device light while maintaining at least part of the polarization of the second device light incident on the diffuser element. Further, especially the luminescent material and / or the diffuser element, especially both are configured in the reflective mode. In embodiments, one of the beam splitter arrangements may (also) be configured to combine the luminescent material light and diffused second device light received by that beam splitter arrangement. Further, in embodiments the optics may (further) comprise a first lens arrangement. The first lens arrangement may be configured between the first beam splitter arrangement and the luminescent material. Yet, the optics may (further) comprise a second lens arrangement. The second lens arrangement may be configured between the second beam splitter arrangement and the diffuser element. In embodiments, the first lens arrangement may comprises a first primary lens (LI 1) and a second primary lens (L12). The first primary lens (LI 1) and the second primary lens (L12) may have a first inter-lens distance (dl). Further, in embodiments the second lens arrangement may comprise a first secondary lens (L21) and a second secondary lens (L22). The first secondary lens (L21) and the second secondary lens (L22) may have a second inter-lens distance (d2). In specific embodiments, | l-d2 / dl |>0.1. Further, the optics may (also) comprise a primary angular spreader (TD11). The primary angular spreader (TD11) may be configured between the first light generating device and the first lens arrangement. Yet, the optics may comprise a secondary angular spreader (TD12). The secondary angular spreader (TD12) may be configured between the second light generating device and the second lens arrangement. Further, in embodiments the primary angular spreader (TD11) may be configured to diffuse first device light received by the primary angular spreader (TD11). Yet, in embodiments the secondary angular spreader (TD12) may be configured to diffuse second device light received by the secondary angular spreader (TD12). Especially, the light generating system may be configured to generate system light comprising one or more of luminescent material light and diffused second device light. Further, the control system may be configured to control a spectral power distribution of the system light. Therefore, in embodiments the invention provides a light generating system comprising a first light generating device, a second light generating device, a luminescent material, a diffuser element, optics, and a control system; wherein: (A) the optics comprise (a) a first beam splitter arrangement, configured between the first light generating device and the luminescent material, and (b) a second beam splitter arrangement, configured between the second light generating device and the diffuser element; (B) the first light generating device is configured to generate first device light, having a first peak wavelength I; wherein the first light generating device comprises a first solid state light source; (C) the second light generating device is configured to generate second device light, having a second peak wavelength X2; wherein the second light generating device comprises a second solid state light source; (D) the optics and the second light generating device are configured such that the second device light, wherein incident on the second beam splitter arrangement , comprises polarized light having a p-polarization or an s-polarization; (E) the luminescent material is configured to convert first device light received by the luminescent material into luminescent material light; the diffuser element is configured to diffuse at least part of the second device light received by the diffuser element thereby providing diffused second device light while maintaining at least part of the polarization of the second device light incident on the diffuser element; the luminescent material and the diffuser element are configured in the reflective mode; (F) wherein one of the beam splitter arrangements is configured to combine the luminescent material light and diffused second device light received by that beam splitter arrangement; (G) the optics comprise (c) a first lens arrangement, configured between the first beam splitter arrangement and the luminescent material, and (d) a second lens arrangement, configured between the second beam splitter arrangement and the diffuser element; (H) the first lens arrangement comprises a first primary lens (LI 1), and a second primary lens (LI 2), wherein the first primary lens (LI 1) and the second primary lens (L12) have a first inter-lens distance (dl); (I) the second lens arrangement comprises a first secondary lens (L21), and a second secondary lens (L22), wherein the first secondary lens (L21) and the second secondary lens (L22) have a second inter-lens distance (d2); wherein | l-d2 / dl |>0.1; (J) the optics (further) comprise (e) a primary angular spreader (TD11), configured between the first light generating device and the first lens arrangement, and (f) a secondary angular spreader (TD12), configured between the second light generating device and the second lens arrangement; (K) the primary angular spreader (TD11) is configured to diffuse first device light received by the primary angular spreader (TD11); the secondary angular spreader (TD12) is configured to diffuse second device light received by the secondary angular spreader (TD12); and (L) the light generating system is configured to generate system light comprising one or more of luminescent material light and diffused second device light; and the control system is configured to control a spectral power distribution of the system light.

[0010] The invention provides a light engine architecture comprising two different types of optical elements / functions. This may enable far better color homogenization in high brightness and high flux laser-phosphor engines than what is observed from commercially available devices in which just a single diffuser is added, while still being highly efficient. Further, the system may provide color and / or correlated color temperature controllable light. Further, the system may be relatively simple. As indicated above, the light generating system may especially comprise a first light generating device and a second light generating device. However, the light generating system may also comprise a third light generating device (see also below).

[0011] Each light generating device may comprise a solid state light source. In embodiments, the solid state light source(s) may each individually be selected from laser diode, a multi -junction light emitting diode, a superluminescent diode, and diode array (especially a laser diode array). Hence, the first solid state light source and the second solid state light source (and the optional third solid state light source) may individually be selected from the group of a laser diode, a multi -junction light emitting diode, a superluminescent diode, and diode array. A diode array may include a laser bank comprising an array of multiple laser chips, or an array of superluminescent diodes, or an array of multi -junction light emitting diodes, etc. Each light source may be configured to generate light source light, like diode laser light, superluminescent diode light, multi -junction light emitting diode light, etc. Alternatively or additionally, the solid state light source(s) may comprise fiber coupled solid state diode lasers.

[0012] The light generating device may be configured to generate device light, comprising such light. As indicated above, the first light generating device may be configured to generate first device light, which may especially comprise on or more of light source light, like diode laser light, superluminescent diode light, multi -junction light emitting diode light, etc. Likewise, the second light generating device may be configured to generate second device light, which may especially comprise on or more of light source light, like diode laser light, superluminescent diode light, multi -junction light emitting diode light, etc. Yet, assuming the presence of a further (such as a third) light generating device, the further (such as a third) light generating device may be configured to generate further (such as third) device light, which may especially comprise on or more of light source light, like diode laser light, superluminescent diode light, multi -junction light emitting diode light, etc. The light source may all be of the same type, though this is not necessarily the case. For instance, the first light generating device may comprise a solid state laser and the second light generating device may comprise a solid state laser (and the optional third light generating device may comprise a solid state laser).

[0013] Hence, the first light generating device may comprise a first solid state light source. Further, the first device light may have a first peak wavelength LI . Especially, the first peak wavelength may be selected from the blue wavelength range (see also below). Yet, the second light generating device may comprise a second solid state light source. Further, the second device light may have a second peak wavelength 2. The luminescent material (see also below) may especially be excited by UV or blue light. Herein, the invention is further explained in relation to blue light. Hence, in embodiments the first device light and the second device light may comprise blue light. Especially, (both) the first device light and the second device light are blue light. Hence, in embodiments the first peak wavelength XI and the second peak wavelength X2 may individually be selected from the wavelength range of 430-490 nm. Especially, the second peak wavelength may be selected from the blue wavelength range. In embodiments, | XI- 2| < 10 nm, more especially | 1- 2| < 5 nm. Hence, in specific embodiments l= X2 may apply. Essentially the same spectral power distributions may be obtained when the first light generating device and the second light generating device may be selected from the same bin. Hence, the peak wavelengths may be essentially the same. In other embodiments, however, 10 nm < | kl - 2| < 60 nm, such as 15 nm < | XI- 2| < 50 nm.

[0014] Yet, the optional third device light (see further below) may have a third peak wavelength 3. Especially, the third peak wavelength may be selected from the blue wavelength range. In embodiments, | XI- 3| < 10 nm, more especially | 1- 3| < 5 nm, and | 2- 3| < 10 nm, more especially | 2- 3| < 5 nm. Essentially the same spectral power distributions may be obtained when the third light generating device and one or more of the first light generating device and the second light generating device may be selected from the same bin. Hence, the peak wavelengths may be essentially the same. In other embodiments, one or more of the following may apply: (i) 10 nm < | kl - 3| < 60 nm, such as 15 nm < | I- X3| < 50 nm, and (ii) 10 nm < | X2- X3| < 60 nm, such as 15 nm < | X2- X3| < 50 nm.

[0015] Further, the light generating system may comprise a luminescent material (see further also below). Especially, the luminescent material may be configured to convert first device light received by the luminescent material into luminescent material light. Further, in embodiments the luminescent material light may have spectral power in one or more of the following spectral ranges: green, yellow, orange, and red. Note that the term “luminescent material” may also refer to a plurality of different luminescent materials.

[0016] Yet, the light generating system comprises optics. The term “optics” may especially refer to (one or more) optical elements. Hence, the terms “optics” and “optical elements” may refer to the same items. The optics may include one or more or mirrors, reflectors, collimators, lenses, prisms, diffusers, phase plates, polarizers, diffractive elements, gratings, dichroics, arrays of one or more of the afore-mentioned, etc. Alternatively or additionally, the term “optics” may refer to a holographic element or a mixing rod. In embodiments, the optics may include one or more of beam expander optics and zoom lens optics. See further above for examples of optics. In embodiments, the optics may comprise an integrator, like a “Koehler integrator” (or “Kohler integrator”). The light generating system comprises optics may comprise a plurality of optical elements, like lenses and mirrors. Specific optical elements are herein described in further detail.

[0017] Amongst others, the optics may comprise a first beam splitter arrangement. Especially, the first beam splitter arrangement may be configured to (i) receive first device light and direct it to the luminescent material, and (ii) receive luminescent material light, and direct this luminescent material to elsewhere in the system, e.g. to a light exit, optionally using further optical elements. Especially, the first beam splitter arrangement may “split” the first device light and luminescent material light in that either the first device light is transmitted by the first beam splitter arrangement and the luminescent material is reflected by the first beam splitter arrangement, or the first device light is reflected by the first beam splitter arrangement and the luminescent material is transmitted by the first beam splitter arrangement. In specific embodiments, the first beam splitter arrangement comprises a dichroic beam splitter (or dichroic beam combiner). Further, in embodiments, an optical axis of the first device light may be incident in a first direction and the luminescent material light escaping from the first beam splitter arrangement may have an optical axis in a second direction, which may be orthogonal to the first direction. Especially, the first beam splitter arrangement may be configured between the first light generating device and the luminescent material. The phrase “the first beam splitter arrangement may be configured between the first light generating device and the luminescent material” may especially indicate that the first device light may reach the luminescent material via the optics, including at least via (reflected or transmitted) by the first beam splitter arrangement. Especially, the luminescent material is configured in the reflective mode, though a transmissive mode is not excluded herein.

[0018] Examples of such dichroic beam splitter are e.g. a short-pass cut-off dichroic plate, or a long-pass cut-off dichroic plate. In specific embodiments, the first dichroic beam splitter is designed for a 45° angle of incidence of the (first) device light).

[0019] Amongst others, the optics may comprise a second beam splitter arrangement. Especially, the second beam splitter arrangement may be configured to (i) receive second device light and direct it to the diffuser element, and (ii) diffused second device light, and direct this diffused second device light to elsewhere in the system, e.g. to a light exit, optionally using further optical elements. Especially, the second beam splitter arrangement may “split” the second device light and diffused second device light in that either the second device light is transmitted by the second beam splitter arrangement and the diffused second device light is reflected by the second beam splitter arrangement, or the second device light is reflected by the second beam splitter arrangement and the diffused second device light is transmitted by the second beam splitter arrangement. In specific embodiments, the second beam splitter arrangement comprises a polarizing beam splitter (or polarizing beam combiner). Further, in embodiments, an optical axis of the second device light may be incident in a first direction and the diffused second device light escaping from the second beam splitter arrangement may have an optical axis in a second direction, which may be orthogonal to the first direction. Especially, the second beam splitter arrangement may be configured between the second light generating device and the diffuser element. The phrase “the second beam splitter arrangement may be configured between the second light generating device and the diffuser element” may especially indicate that the second device light may reach the diffuser element via the optics, including at least via (reflected or transmitted) by the second beam splitter arrangement.

[0020] In embodiments, the first beam splitter arrangement and the second beam splitter arrangement are physically separated optical elements. However, it is herein not excluded that an integrated optical element may be used having the functionality of both the first beam splitter arrangement and the second beam splitter arrangement.

[0021] Hence, in specific embodiments the light generating system may further comprise a dichroic element, configured to transmit or reflect the light and configured to reflect or transmit the luminescent material light. The dichroic element may be an embodiment of a color separation element, such as described in US7070300, which is herein incorporated by reference. Especially, the color separation element may be selected from the group of a dichroic mirror, a dichroic cube, and a diffractive optical element. Optionally, the color separation element maybe provided using a hologram. Especially, the dichroic element may be a dichroic mirror or reflector.

[0022] Hence, in a light generating system comprising a source of light, like a light generating device (e.g. comprising a solid state light source) that emits light having a first wavelength range along a first beam path, a wavelength converting element may be configured in the first beam path. Such wavelength converting element may in embodiments be physically separated from source of light. Further, such wavelength converting element may be configured to convert at least part of the light having a first wavelength range into light having a second wavelength range along a second beam path. Especially, in embodiments a color separation element, especially a dichroic element, may be disposed between the source of light and the wavelength converting element. In embodiments, the color separation element may be configured to prevent substantially all of the light having the second wavelength range from being incident on the source of light. Hence, such color separation element may in embodiments be configured to (a) transmit at least part of the light having the first wavelength range and reflect at least part of the light having the second wavelength range, or (b) reflect at least part of the light having the first wavelength range and transmit at least part of the light having the second wavelength range.

[0023] Hence, for the dichroic beam splitter may apply that for a first wavelength range, the wavelength averaged transmission may be higher, like at least 10% points higher, such as at least 20% points higher, or even at least 30 % points, than for a second wavelength range. Similarly, for a first wavelength range, the wavelength averaged reflection may be lower, like at least 10% points lower, such as at least 20% points lower, or even at least 30 % points, than for a second wavelength range. Especially, in embodiments, the dichroic beam splitter may be configured to direct at least 60% of the light of the first wavelength range to a first direction and at least 60% of the light of the second wavelength range to a second direction, wherein the directions may in embodiments have a mutual angle selected from the range 45-135°, such as about 90°. The percentage of the light may refer to a spectral power (e.g. in Watt).

[0024] Hence, for the polarizing beam splitter may apply that for a first polarization, the transmission may be higher, like at least 10% points higher, such as at least 20% points higher, or even at least 30 % points, than for a second polarization. Similarly, for a first polarization, the reflection may be lower, like at least 10% points lower, such as at least 20% points lower, or even at least 30 % points, than for a second polarization. Especially, in embodiments, the dichroic beam splitter may be configured to direct at least 60% of the light of the first polarization to a first direction and at least 60% of the light of the second polarization to a second direction, wherein the directions may in embodiments have a mutual angle selected from the range 45-135°, such as about 90°. The percentage of the light may refer to a spectral power (e.g. in Watt). Especially, the first polarization and the second polarization may comprise linear polarizations such as selected from s polarization and p polarization. Optionally, the first polarization and the second polarization may be selected from different elliptically polarized light. In embodiments, the polarizing beam splitters herein may be selected from reflective polarizing beam splitters (reflective polarizers). As indicated above, for the second beam splitter arrangement a polarizing beam splitter (or “first polarizing beam splitter”) may be applied. This may thus also imply that the second device radiation received by the second beam splitter arrangement is polarized light. This can be achieved by one or more of (i) using a second light generating device that generates polarized light, like a solid state laser, and (ii) using polarizer optics, providing the second device light with the desired polarization. Especially, the polarization is selected from s-polarization and p-polarization. Hence, the optics and the second light generating device may be configured such that the second device light, wherein incident on the second beam splitter arrangement , comprises polarized light having a p-polarization or an s-polarization.

[0025] Examples of such polarizing beam splitter are e.g. a thin film polarization beam splitter plates, polarization beam splitter cubes, reflecting s-polarized light and transmitting p-polarized light, with respect to the plane of incidence upon the beam splitter. Also polarizing beam splitter plates which are partially transmitting and reflecting light of orthogonal polarization may be applied, e.g. with a particular reflection / transmission splitting ratio for a certain polarization. In specific embodiments, the polarizing beam splitters are designed for a 45° angle of incidence of the (second) device light.

[0026] Getting back to the diffuser element, the luminescent material light generated by conversion of at least part of the first device light may be diffuse by definition. However, the (second) device light that may be admixed by the luminescent material light for color purposes, like color tuning, may not necessarily be diffuse, or at least less diffuse, if no measures are taken. To this end, the light generating system may comprise amongst others the diffuser element. Hence, the diffuser element may be configured to diffuse at least part of the second device light received by the diffuser element thereby providing diffused second device light.

[0027] As the second beam splitter arrangement may be used to split between different polarizations, desirable the diffused second device light may also be polarized. Hence, especially the diffuser element may be configured to diffuse at least part of the second device light received by the diffuser element thereby providing diffused second device light while maintaining at least part of the polarization of the second device light incident on the diffuser element (see also below).

[0028] Especially, the diffuser element is configured in the reflective mode. More especially, the luminescent material and the diffuser element are configured in the reflective mode. The luminescent material light and the diffused second device light, when both generated, may desirably combined into one beam. To this end, a beam combiner may be applied. Especially, one of the beam splitter arrangements may (also) be configured to combine the luminescent material light and diffused second device light received by that beam splitter arrangement. Hence, in embodiments the first beam splitter arrangement may be configured in a light receiving relationship with the second beam spitter arrangement, and may also have the function of a beam combiner, and in other embodiments the second beam splitter arrangement may be configured in a light receiving relationship with the first beam spitter arrangement, and may also have the function of a beam combiner. The beam combiner may receive in orthogonal direction the luminescent material light and the diffused second device light, and transmit one of the luminescent material light and the diffused second device light and reflect the other one of the luminescent material light and the diffused second device light, thereby combining these. Due to the fact that the second device light that is admixed in the luminescent material light is diffused, the (diffused) second device and the luminescent material light may be homogeneously distributed over a beam of light comprising both.

[0029] Further, the optics may comprise (c) a first lens arrangement, configured between the first beam splitter arrangement and the luminescent material, and (d) a second lens arrangement, configured between the second beam splitter arrangement and the diffuser element. The first lens arrangement may be configured (i) to provide a desired spot of first device light on the luminescent material, and (ii) to collected luminescent material light. Hence, in embodiments, the first lens arrangement may be configured to condense first device light on the luminescent material and to collect luminescent material light emanating from the luminescent material. Similarly, the second lens arrangement may be configured (i) to provide a desired spot of second device light on the diffuser element, and (ii) to collected diffused second device light. Hence, in embodiments, the second lens arrangement may be configured to condense second device light on the diffuser element and to collect diffused second device light emanating from the diffuser element.

[0030] The first lens arrangement may in embodiments comprise two lenses. In other embodiments, the first lens arrangement may comprise three lenses; more lenses, however, are not excluded. Likewise, the second lens arrangement may in embodiments comprise two lenses. In other embodiments, the second lens arrangement may comprise three lenses; more lenses, however, are not excluded. Yet, in embodiments each of the first lens arrangement and the second lens arrangement may have the same number of lenses. In embodiments, the first lens arrangement may comprise a first primary lens (LI 1), and a second primary lens ( I 2). Especially, the first primary lens (LI 1) and the second primary lens (L12) may have a first inter-lens distance (dl). Likewise, the second lens arrangement may comprise a first secondary lens (L21), and a second secondary lens (L22). Especially, the first secondary lens (L21) and the second secondary lens (L22) may have a second inter-lens distance (d2). The inter-lens distances may be the shortest distance between (the) two adjacent lenses.

[0031] Especially, in embodiments the intern-lens distances may be different. For instance, this may allow providing a large spot on the diffuser element than on the luminescent material. In specific embodiments, | l-d2 / dl |>0.1 (may apply). Hence, the first primary lens (LI 1) and a second primary lens (L12) may be configured at a non-zero distance (from each other), like e.g. at least 1 mm, for instance at least 5 mm, like at least 10 mm, such as at least 15 mm, or even at least 30 mm. Likewise, the first secondary lens (L21) and the second secondary lens (L22) may be configured at a non-zero distance (from each other), like e.g. at least 5 mm, like at least 10 mm, such as at least 15 mm, or even at least 30 mm.

[0032] In embodiments, dl>d2, and in other embodiments, dl<d2. Especially, in embodiments d2<dl. Further, in embodiments d2 / dl<0.9. However, herein dl=d2 embodiments may also be possible. In embodiments, with essentially two identical lens arrangements and xl=x2, making the two inter-lens distances unequal may provide a way to correct for the different reflection from the reflective diffuser or the luminescent material. In such embodiments, especially d2<dl may apply, as then dl may be chosen to set the luminescent material in focus (smallest spot) and d2 may then be chosen to be smaller to broaden the spot on the reflective diffuser while also limiting the losses which would result from a lower collection efficiency at larger inter-lens distances. In other embodiments, lens arrangements may not be fully identical, and then xl and x2 are (also) not necessarily identical. In such embodiments, e.g. d2>dl may be chosen.

[0033] Would e.g. three lenses be chosen, then especially both lens arrangements may consist of three lenses. Then there are three types of lenses, LI, L2, and L3. This may imply distance dl 1 and dl2, between the first lens and second lens of the respective lens arrangements, d21 and d22, between the second lens and the third lens of the respective lens arrangements. In such embodiments, e.g. the condition d21<dl 1 or d22<dl2 may apply.

[0034] Further, for e.g. homogenization of the light of the luminescent material and the diffused second device light, upstream an optical element that may be used to combine the light of the luminescent material and the diffused second device light, an angular spreader may be applied. Hence, in embodiments, the optics may (further) comprise (e) a primary angular spreader (TD11), configured between the first light generating device and the first lens arrangement, and / or (f) a secondary angular spreader (TD12), configured between the second light generating device and the second lens arrangement. Especially, the primary angular spreader (TD11) may be configured to diffuse first device light received by the primary angular spreader (TD11). Further, especially the secondary angular spreader (TD12) is configured to diffuse second device light received by the secondary angular spreader (TD12). This may also improve homogenization of the system light (see also below).

[0035] Note that the diffuser element may especially be configured in the reflective mode, whereas the primary angular spreader and the secondary angular spreader may especially be in the transmissive mode.

[0036] The primary angular spreader and the secondary angular spreader may especially be top-hat diffusers. Further, their diffusion angles, defined by the full width half maximum (FWHM) may be relatively small, like individually selected from the range of 0.5- 20°, more especially individually selected from the range of 1-15°. Especially, the values for the diffusion angle may refer to a mean diffusion angle (as the diffusion may be angular dependent). A mean diffusion angle may be defined as the FWHM angle of the intensity- weighted and rotationally integrated angular diffusion profile for an incident pencil beam at normal incidence (zero angle of incidence) at a specific wavelength. Herein, a pencil beam may be a narrow beam with a low divergence angle, e.g. with divergence of less than 0.5°.

[0037] The primary angular spreader (TD11) may have a first diffusion angle 91, defined at full width half maximum, which may especially be selected from the range of 1- 15°, more especially selected from the range of 1-10°. Further, the secondary angular spreader (TD12) may have a second diffusion angle 92, defined at full width half maximum, which may especially be selected from the range of 1-15°, more especially selected from the range of 1-1 °. Further, as it may be desirable that the diffusion may at least be equal, or especially be larger, for the second device light, in embodiments 92 / 91>l, such as 92 / 91>1. Further, in embodiments 92 / 91>l .1. Further, in embodiments 92 / 91<2.

[0038] Especially, in the optical path between the first light generating device and the luminescent material, the primary angular spreader (TD11) may be configured. In order to diffuser the first device light (and not further diffused luminescent material light), the primary angular spreader (TD11) may be configured between the first light generating device and the first beam splitter arrangement (and e.g. not between the first beam splitter arrangement and the luminescent material, although such embodiments are not excluded herein. Similarly, the secondary angular spreader (TD12) may be configured between the second light generating device and the second beam splitter arrangement.

[0039] Especially, the light generating system is configured to generate system light comprising one or more of luminescent material light and diffused second device light. Whether or not the system light comprises the luminescent material light and diffused second device light may depend upon the control of the light generating devices. Assuming only a first light generating device and a second light generating device, the system light may comprise luminescent material light only, when only the first light generating device is operating. Similarly, the system light may comprise diffused second device light only, when only the second light generating device is in operation. In this way, a spectral power distribution of the system light may be controlled. Hence, the light generating system may further comprise a control system. Especially, the control system may be configured to control a spectral power distribution of the system light. For instance, in embodiments the control system may control the color rendering index and / or correlated color temperature of the system light. Amongst others, the control system may control a spectral power distribution of the system light by controlling the first light generating devices and second light generating devices, and optional further light generating devices (like the optional third light generating devices). Further control options of the spectral power distribution are described elsewhere herein. In embodiments, the control system may also control a radiant flux of the system light by controlling the first light generating devices and second light generating devices, and optional further light generating devices (like the optional third light generating devices).

[0040] In embodiments the first primary lens (Li l) and the first secondary lens (L21) may essentially be the same in terms of material, size, and effective focal length. However, this is not necessarily the case. Alternatively or additionally, embodiments the second primary lens (LI 2) and the second secondary lens (L22) may essentially be the same in terms of material, size, and effective focal length . However, this is also not necessarily the case. Essentially identical first primary and first secondary lenses, and / or essentially identical second primary and second secondary lenses may provide a relatively simple configuration. However, this is not necessarily the case.

[0041] Especially, in embodiments the angular spread of the light exiting second primary lens (LI 2) towards the luminescent material may be larger than the angular spread of the light exciting first primary lens (Li l) towards the luminescent material (and the same may apply for the incident angular spread of the luminescent material light in the direction away from the luminescent material). Likewise, especially in embodiments the angular spread of the light exiting second secondary lens (L22) towards the diffuser element may be larger than the angular spread of the light exciting first secondary lens (L21) towards the diffuser element (and the same may apply for the incident angular spread of the diffused second device light in the direction away from the diffuser element). Hence, in embodiments, the first primary lens (LI 1) has a first primary optical power Pl 1, the second primary lens (LI 2) has a second primary optical power Pl 2, the first secondary lens (L21) has a first secondary optical power P21, and the second secondary lens (L22) has a second secondary optical power P22, wherein in specific embodiments P12>P11 and / or P22>P21. In further specific embodiments P12 / P11>1.1 and / or P22 / P21> 1.1. Further, in embodiments P12 / P11<5, such as in embodiments at maximum 3, and / or P22 / P21<5, such as in embodiments at maximum 3. Especially, optical power may refer to the degree to which an optical element like a lens, a mirror, or other optical element, converges or diverges light. It may especially be equal to the reciprocal of the focal length of the optical element: P = 1 / f.

[0042] Further, the first primary lens (Li l) may have a first primary numerical aperture N11, the second primary lens (LI 2) may have a second primary numerical aperture N12, the first secondary lens (L21) has a first secondary numerical aperture N21, and the second secondary lens (L22) has a second secondary numerical aperture N22. In embodiments, especially when the first primary lens (Li l) and the first secondary lens (L21) are essentially the same and the second primary lens (LI 2) and the second secondary lens (L22) are essentially the same, one or more of the following may apply: (i) N12>N11 and (ii) N22>N21. Further, in specific embodiments O.9<N11 / N21<1.1 and 0.9<N21 / N22<l.l. However, other values may also be possible; for instance, N12<N 11 and / or N22<N21 are herein not excluded, and may be chosen in dependence of the chosen types of lenses.

[0043] Further, the luminescent material and the first lens arrangement may have a first shortest distance (xl) and the diffuser element and the second lens arrangement may (also) have a second shortest distance (x2). Especially, xl is the shortest distance between the second primary lens and a surface of the luminescent material and x2 is the shortest distance between the second secondary lens L22 and a surface of the reflective diffuser. In embodiments, x2=xl. In other embodiments, however x2^xl. In specific embodiments, x2 / xl<0.9 or x2 / xl>l.l. Yet, in embodiments 0.2<x2 / xl<5.

[0044] As indicated above, the second beam splitter arrangement may discriminate light on the basis of polarization. Hence, in such embodiments it may be desirable that the second device light and the diffused second device light have different polarizations. This may be well achieved when having a configuration with a polarization change element configured in the optical path of the second device light (and the diffuse second device light) between the second beam splitter arrangement and the diffuser element. Especially, such polarization change element may comprises a X / 4 waveplate. Hence, in embodiments the system may comprise a polarization change element, wherein the polarization change element comprises a X / 4 waveplate, wherein the polarization change element is configured between second beam splitter arrangement and the second lens arrangement. Especially, the X / 4 waveplate is a X / 4 waveplate optimized for a wavelength range including the second peak wavelength.

[0045] Especially, the polarization changing element is configured to change s- polarized light or p-polarized light to circular polarized light. The diffuser element may change the direction of the polarized light, but the circular polarized light may essentially stay circular polarized light. At least part of the diffused light, having circular polarization, will propagate from the diffuser element to the polarization changing element, and then be converted to (diffused) s-polarized light and / or (diffused) p-polarized light, which may further propagate to one of the beam splitter arrangements, especially the (at least) the second beam splitter arrangement. Therefore, in embodiments the polarization changing element may comprise a X / 4 waveplate. With the polarization changing element configured between second beam splitter arrangement and the second lens arrangement, p-polarized light can be converted in diffused s-polarized light, and s-polarized light can be converted in diffused p- polarized light.

[0046] Especially, the polarization changing element may be an element that induces a 90° phase shift between the two orthogonal linear polarization components (s and p) of the light. The most common way is to use birefringent material (birefringent rotators), such as a quarter-wave plate (1 / 4 X plate). An alternative may be to use the Faraday effect, in which case the phase shift is caused by an applied magnetic field (Faraday rotators). Typically, a retarder, may provide a defined phase shift between the polarization components projected along the fast and slow axes of birefringent material. A X / 4 phase shift may be desired for our case. The same effect can be achieved with a multiple order waveplate (n+X / 4 phase shift), wherein n is an integer. However, Fresnel rhomb retarders may be also used to result in X / 4 phase shift. Faraday rotators may typically be used to rotate direction of linear polarized light. Combination of 45° Faraday rotator with an end reflector may form a Faraday mirror, able to isolate incoming and back-propagating beams on their polarization. The essentially non-diffused second device light may e.g. comprise light having a first linear polarization, which is turned, upon passage through the polarization changing element, such as a 1 / 4 Z. plate, into elliptically polarized light having a first rotation direction, like right circular polarized light. The diffuser element may convert this elliptically polarized non-diffused light having a first rotation direction, into elliptically polarized diffused light having a second rotation direction, opposite of the first rotation, i.e. e.g. left circular polarized light (in line with the example above). This elliptically polarized diffused light having a second rotation direction is turned, upon passage again through the polarization changing element, such as a 1 / 4 plate, into diffused light comprising a second linear polarization. The first linear polarization differs from the second linear polarization, and are both selected from s-polarization and p-polarization. Hence, in embodiments the non-diffused second device light may e.g. comprise p-polarized light, which is turned, upon passge through the QWP (quarter wave plate), into e.g. left-handed circular polarized light, that is diffused by the reflective diffuser into right-handed polarized diffused light, which, upon passage through the QWP again, is turned into s-polarized light. Depending on the orientation of the QWP, incident p-polarized light may alternatively be converted by the QWP into right-handed circular polarized light, and then s-polarized light is converted into left-handed circular polarized light.

[0047] Hence, would the undiffused second device light comprise p-polarized light, then the diffused second device light may comprise s-polarized light. Likewise, would the undiffused second device light comprise s-polarized light, then the diffused second device light may comprise p-polarized light. Therefore, the phrase “maintaining at least part of the polarization of the second device light incident on the diffuser element”, and similar phrases may especially indicate that the elliptical polarization of the second device light after reflection at the diffuser element is still present, though its handedness may have changed from left elliptical polarized light to right elliptical polarized light, or vice versa.

[0048] In embodiments, in addition to the first light generating device and the second light generating device, a third light generating device may be applied. A third light generating device may be applied to increase the maximum spectral power receivable by the luminescent material or to increase the maximum spectral power receivable by the diffuser element. Further, the third light generating device may allow, if desired, a further color tuning of the system light, when the spectral power distribution of the third device light generated by the third light generating device differs from the spectral power distribution of the light generating device that is configured to pump the same item (selected from the luminescent material and the diffuser element). Here below, embodiments are described where the third light generating device is also used to pump the luminescent material. However, the invention is not limited to such embodiments. Would the third light generating device is also used to pump the diffuser element, diffused third device light would be generated.

[0049] The third light generating device is configured to generate third device light, having a third peak wavelength 3. As indicated above, this third device light may comprise blue light (see further above). The first device light and the second device light may be combined before reaching the luminescent material. To this end, a beam combiner ( or “beam splitter”) may be applied, configured to combine both beams into a single beam. Such beam combiner may be a polarizing beam combiner (or polarizing beam splitter), which may be based on (orthogonally) incident light having different polarizations, or may be a dichroic beam combiner (or dichroic beam splitter), which may be based on (orthogonally) incident light having different spectral power distributions. In embodiments, the beam combiner may be selected from a dichroic beam combiner, and a polarization beam combiner.

[0050] Hence, in embodiments the system may further comprise (i) a third light generating device, and (ii) a further beam combiner. Especially, the third device light comprises polarized light having a p-polarization or an s-polarization, wherein the first device light comprises polarized light having a p-polarization or an s-polarization; wherein the polarization of the first device light and the third device light differ. Alternatively or additionally, the third device light and the first device light have different spectral power distributions, especially with peak wavelengths differing at least about 10 nm. Further, in embodiments the further beam combiner, such as a second polarizing beam combiner or a second dichroic beam combiner, may be configured upstream of the first beam splitter arrangement and may be configured to combine the first device light and the third device light received by the further beam combiner and direct to the first beam splitter arrangement. For instance, in specific embodiments the light generating system according may further comprising (i) a third light generating device, and (ii) a (second) polarizing beam combiner, wherein: (A) the third device light comprises polarized light having a p-polarization or an s- polarization; (B) the first device light comprises polarized light having a p-polarization or an s-polarization; the polarization of the first device light and the third device light differ; and (C) the (second) polarizing beam combiner may be configured upstream of the first beam splitter arrangement and may be configured to combine the first device light and the third device light received by the second polarizing beam splitter and direct to the first beam splitter arrangement.

[0051] Having generated luminescent material light and diffused second device light, these may have to be combined, such that in an operational mode of the light generating system wherein both the first light generating device and the second light generating device provide device light, the system light comprises both the luminescent material light and diffused second device light. Several solutions may be possible, amongst other embodiments wherein one of the beam splitter arrangements is also configured as beam combiner. Note that a polarizing beam splitter may also have the function of a polarizing beam combiner; likewise, a dichroic beam splitter may also have the function of a dichroic beam combiner.

[0052] Hence, in specific embodiments the second beam splitter arrangement may comprise polarizing beam splitting and dichroic beam combiner functionalities. The former aspect has been described above, the latter aspect indicates that the second beam splitter arrangement may also combine the luminescent material light and diffused second device light received by the second beam splitter arrangement. For instance, in embodiments the polarization function is used to separate (split) the reflectively diffused device light from the non-reflectively-diffused device light and the combine the reflectively-diffused device light with the luminescent light; the dichroic functionality is found in the requirement of the element to be transmissive for luminescent light while being reflective for s-polarized (second) device light and thus combine luminescent light with s-polarized (second) device light. Especially, in embodiments the second beam splitter arrangement may be configured (a) such that: in dependence of the polarization of the second device light, second device light is directed to the first beam splitter arrangement or to the diffuser element, and (b) to combine diffused second device light and luminescent material light received by the second beam splitter arrangement.

[0053] Further control may be provided when the light generating system further comprises a polarization controlling element, which may be configured to control the polarization of the second device light received by the second beam splitter arrangement. In embodiments, the polarization controlling element may comprise a birefringent rotator, wherein the polarization controlling element is configured between the second light generating device and the second beam splitter arrangement. Instead of, or in addition to the birefringent rotation, a waveplate or polarization retarder may be applied. Yet, in other embodiments, the polarization control element may comprise an actuator, configured to control rotation of the second light generating device around the optical axis of its optical output beam (of second device light).

[0054] In embodiments, the polarization controlling element may comprise a rotatable birefringent rotator. More especially, the (rotatable) birefringent rotator comprises a X / 2 waveplate. However, other phase-shift inducing components for the two linear orthogonal polarization components which can change the ratio of transmitted versus reflected light may also be applied. With a half-wavelength plate, s-polarized light can be transformed for 0- 100% into p-polarized light. With a quarter-wavelength plate that may be only 0-50%. With a 3 / 8th-wavelength plate 0-75%, and with a l / 8th-wavelength plate 0-25%. So, a halfwavelength plate may give full flexibility (and independence of the actual polarization direction of the source), while the other options may give more limitations, both in terms of the fraction of light that can be transformed into required polarized components and in terms of the orientation of the polarization direction of the source.

[0055] With the polarization controlling element, the polarization of the second device light may be controlled. For instance, with a (rotatable) X / 2 retarder (see also below), in embodiments polarizations between fully s polarization and fully p polarization may be chosen. Hence, in embodiments the polarization controlling element may especially be configured to control polarization of the second device light. In embodiments, the polarization controlling element may especially be configured to control a degree of polarization of the polarized light.

[0056] Especially, in embodiments the degree of polarization may be defined as a percentage of the p-polarized light or the s-polarized light relative to the total of s-polarized light and p-polarized light. For determining the percentages, the angular luminance of the second device light having s polarization and the angular luminance of the second device light having p polarization may be applied. For instance, the second device light, downstream of the polarization controlling element, may have 20% s polarization and 80% p polarization. For the angular luminance, see e.g. Blom, S. et al., Towards a polarized light-emitting backlight: Micro-structured anisotropic layers, DOI- 10.1889 / 1.1827869, Journal of the Society for Information Display, September 2002, p. 209-213. Instead of the angular luminance, also the luminance may be applied.

[0057] Yet, (in general) the term “degree of polarization” is known in the art. Especially, in embodiments the degree of polarization may be defined as a percentage of the p-polarized light and / or the s-polarized light relative to the total of p-polarized light and s- polarized light. Measurement of the degree of polarization is known in the art, and may be based on Stokes parameters.

[0058] The system may comprise an actuator configured to control the polarization controlling element. The control system may control the actuator for controlling the polarization controlling element.

[0059] 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”.

[0060] Yet, in further embodiments, the system may (further) comprise a tertiary angular spreader (TD13), configured between (i) the second beam splitter arrangement and the second lens arrangement or (ii) the first beam splitter arrangement and the second beam splitter arrangement. This may further allow controlling of the beam widths. The tertiary angular spreader may especially (also) be a top-hat diffuser. Further, the diffusion angle, defined by the full width half maximum may be relatively small, like individually selected from the range of 0.5-20°, more especially individually selected from the range of 1-15°. Especially, the value for the diffusion angle may refer to a mean diffusion angle (as the diffusion may be angular dependent) (see also above). In embodiments, the tertiary angular spreader (TD13) has a third diffusion angle (03) selected from the range of 1-15°, more especially selected from the range of 1-10°.

[0061] The angular spreaders, such as the primary angular spreader, the secondary angular spreader, and the tertiary angular spreader, may each individually be selected from the group of transmissive diffusers, a lens array, and a fly-eye lens array pair. The reference TD may thus in embodiments refer to a transmissive diffuser, but may in other embodiments refer to a lens array or a fly-eye lens array pair. Angular spreaders may also be indicated as integrators. The angular spreaders may especially be applied for (i) reducing the hot spots in the projection on the diffuser element (and, similarly, on the luminescent material) (thereby potentially increasing lifetime) and (ii) defining an angular range of the light that is transformed by the condenser lens system into a spatial range of the light on the target plane (diffuser or luminescent material), i.e., a defined spot size, for a desired irradiance distribution at that spot. The diffuser may (thus) have a function of defining an initial etendue of the luminescent light, linked to the final etendue of the system light. As indicated above, whether or not the system light comprises the luminescent material light and diffused second device light may depend upon the control of the light generating devices. Hence, in specific embodiments, in an operational mode of the light generating system the system light comprises both the luminescent material light and diffused second device light. Further, in specific embodiments the system light may have a correlated color temperature selected from the range of 1500-12000 K, such as 1600-10000 K. Alternatively or additionally, in specific embodiments the system light may have a color rendering index of at least 65, such as at least about 70.

[0062] The control system may be configured to control the first light generating device and the second light generating device. When also a third light generating device is available, the control system may be configured to control the first light generating device, the second light generating device, and the third light generating device. Especially, such controlling may in embodiments include controlling the spectral power (i.e. including up dimming and down dimming). Further, the control system may control the optional polarization control element. In these ways, the spectral power distribution of the system light may be controlled. Yet, would a rotatable element (for supporting one or more of the luminescent material and the diffuser element) be available (see also below), the control system may also be configured to control rotation (speed) of such rotatable element (in an operational mode of the light generating system.

[0063] Hence, in embodiments one or more of the luminescent material and the diffuser element are comprised by the rotatable element. This may allow distribution of the device light over a larger cooling area, thereby allowing a better heat dissipation. Phosphor wheels are known in the art. Hence, the rotatable element may comprise a phosphor wheel, with a ring-like distribution of the luminescent material and / or a ring-like distribution of the diffuser element. The rotatable element may support the luminescent material.

[0064] In an aspect, the invention (also) provides light generating system comprising a first light generating device, a second light generating device, a luminescent material, a diffuser element, optics, and a control system; wherein the optics comprise (a) a first beam splitter arrangement, configured between the first light generating device and the luminescent material, and (b) a second beam splitter arrangement, configured between the second light generating device and the diffuser element; the first light generating device is configured to generate first device light, having a first peak wavelength I; wherein the first light generating device comprises a first solid state light source; the second light generating device is configured to generate second device light, having a second peak wavelength Z2; wherein the second light generating device comprises a second solid state light source; the luminescent material is configured to convert first device light received by the luminescent material into luminescent material light; the diffuser element is configured to diffuse at least part of the second device light received by the diffuser element thereby providing diffused second device light while maintaining at least part of the polarization of the second device light incident on the diffuser element; the luminescent material and the diffuser element are configured in the reflective mode; wherein one of the beam splitter arrangements is (also) configured to combine the luminescent material light and diffused second device light received by that beam splitter arrangement; the optics (further) comprise (c) a first lens arrangement, configured between the first beam splitter arrangement and the luminescent material, and (d) a second lens arrangement, configured between the second beam splitter arrangement and the diffuser element; the first lens arrangement comprises a first primary lens (LI 1), and a second primary lens ( I 2), wherein the first primary lens (LI 1) and the second primary lens (LI 2) have a first inter-lens distance (dl); the second lens arrangement comprises a first secondary lens (L21), and a second secondary lens (L22), wherein the first secondary lens (L21) and the second secondary lens (L22) have a second inter-lens distance (d2); the optics (further) comprise (e) a primary angular spreader (TD11), configured between the first light generating device and the first lens arrangement, and (f) a secondary angular spreader (TD12), configured between the second light generating device and the second lens arrangement; the primary angular spreader (TD11) is configured to diffuse first device light received by the primary angular spreader (TD11); the secondary angular spreader (TD12) is configured to diffuse second device light received by the secondary angular spreader (TD12); the primary angular spreader (TD11) has a first diffusion angle 91, defined at full width half maximum, selected from the range of 1-15° (especially selected from the range of 1-10°); wherein the secondary angular spreader (TD12) has a second diffusion angle 92, defined at full width half maximum, selected from the range of 1-15° (especially selected from the range of 1-1 °); the luminescent material and the first lens arrangement have a first shortest distance (xl), wherein the diffuser element and the second lens arrangement have a second shortest distance (x2); the light generating system is configured to generate system light comprising one or more of luminescent material light and diffused second device light; and the control system is configured to control a spectral power distribution of the system light; and one or more of the following applies: (i) | l-d2 / dl |>9.1, (ii) 92 / 91>l (such as wherein 92 / 91> 1), and (iii) x2^xl, (such as x2 / xl<9.9).

[0065] Further, as indicated above, especially the optics and the second light generating device are configured such that the second device light, wherein incident on the second beam splitter arrangement , comprises polarized light having a p-polarization or an s- polarization.

[0066] Here below, some further embodiments are described.

[0067] The term “light source” may in principle relate to any light source known in the art. In a specific embodiment, the light source comprises a solid state LED light source (such as an LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of light sources, such as 2-2999 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs.

[0068] Further, the term “light source” may in embodiments also refer to a so-called chip-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 light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module. The term “light source” may also refer to a chip scaled package (CSP). A CSP may comprise a single solid state die with provided thereon a luminescent material comprising layer. The term “light source” may also refer to a midpower package. A midpower package may comprise one or more solid state die(s). The die(s) may be covered by a luminescent material comprising layer. The die dimensions may be equal to or smaller than 2 mm, such as in the range of e.g. 9.2-2 mm. Hence, in embodiments the light source comprises a solid state light source. Further, in specific embodiments, the light source comprises a chip scale packaged LED. Herein, the term “light source” may also especially refer to 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.

[0069] The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a laser diode, a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser (EEL), a photonic crystal surface emitting laser (PCSEL), a vertical external cavity surface emitting laser (VECSEL), etc... In a specific embodiment, the light source comprises a solid-state light source (such as an LED or laser diode). In an embodiment, the light source comprises an LED (light emitting diode). The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED).

[0070] The term LED may also refer to a plurality of LEDs.

[0071] The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 solid state 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 an LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise an LED with on-chip optics. In embodiments, the light source comprises pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering).

[0072] The light source may especially be configured to generate light source light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light source light may in embodiments comprise one or more bands, having band widths as known for lasers.

[0073] The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid state light source as such, like a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source (but may also be indicated as light generating device). Hence, a white LED is a light source (but may e.g. also be indicated as (white) light generating device).

[0074] The term “light source” herein may also refer to a light source comprising a solid state light source, such as an LED or a laser diode or a superluminescent diode.

[0075] The term “light generating device” may be used to address a light source and further (optical components), like an optical filter and / or a beam shaping element, etc.

[0076] 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.

[0077] The term “solid state light source”, or “solid state material light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, or a superluminescent diode. Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, refer to a laser diode (or diode laser). In embodiments, the terms “laser” or “solid state laser” or “solid state material laser” may refer to one or more of a semiconductor laser diodes, such as GaN, InGaN, AlGalnP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc. In embodiments, laser light sources may be arranged in a laser bank (see also above). The laser bank may in embodiments comprise heat sinking and / or optics e.g. a lens to collimate the laser light. Hence, in embodiments lasers in a laser bank (or “laser array bank”) may share the same optics.

[0078] The laser light source is configured to generate laser light source light (or “laser light”). The light source light may essentially consist of the laser light source light. The light source light may also comprise laser light source light of two or more (different or identical) laser light sources. For instance, the laser light source light of two or more (different or identical) laser light sources may be coupled into a light guide, to provide a single beam of light comprising the laser light source light of the two or more (different or identical) laser light sources. In specific embodiments, the light source light is thus especially collimated light source light. In yet further embodiments, the light source light is especially (collimated) laser light source light.

[0079] The laser light source light may in embodiments comprise one or more bands, having band widths as known for lasers. In specific embodiments, the band(s) may be relatively sharp line(s), such as having full width half maximum (FWHM) in the range of less than 20 nm at RT, such as equal to or less than 10 nm. Hence, the light source light has a spectral power distribution (intensity on an energy scale as function of the wavelength) which may comprise one or more (narrow) bands.

[0080] The term “solid state material laser”, and similar terms, may refer to a solid state laser like based on a crystalline or glass body dopes with ions, like transition metal ions and / or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, such as e.g. a vertical cavity surface-emitting laser (VCSEL), etc.

[0081] The term “solid state light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, or a superluminescent diode.

[0082] Spectral power distributions may differ or may be the same. For instance, the spectral power distributions of the first device light and the second device light may be different or may be the same. In specific embodiments, colors or color points of a first type of light and a second type of light may be different when the respective color points of the first type of light and the second type of light differ with at least 0.01 for u’ and / or with at least 0.01 for v’, even more especially at least 0.02 for u’ and / or with at least 0.02 for v’. In yet more specific embodiments, the respective color points of first type of light and the second type of light may differ with at least 0.03 for u’ and / or with at least 0.03 for v’. Here, u’ and v’ are color coordinates of the light in the CIE 1976 UCS (uniform chromaticity scale) diagram. Spectral power distributions of different sources of light having centroid wavelengths differing least 10 nm, such as at least 20 nm, or even at least 30 nm may be considered different spectral power distributions, e.g. different colors. In general, the differences in centroid wavelengths will not be larger than about 400 nm, such as not more than 350 nm. In other specific embodiments, colors or color points of a first type of light and a second type of light may be essentially the same when the respective color points of the first type of light and the second type of light differ with at maximum 0.03 for u’ and / or with at maximum 0.03 for v’, even more especially at maximum 0.02 for u’ and / or with at maximum 0.02 for v’. In yet more specific embodiments, the respective color points of first type of light and the second type of light may differ with at maximum 0.01 for u’ and / or with at maximum 0.01 for v’. Here, u’ and v’ are color coordinate of the light in the CIE 1976 UCS (uniform chromaticity scale) diagram. The color points indicated with u’,v’ especially refer to the CIE 1976 color points (see ISO CIE 11664-5: Colorimetry - Part5: CIE 1976 L*u*v* color space and u', v' uniform chromaticity scale diagram). Further, the light generating system comprises a luminescent material. 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 downconversion. 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.

[0083] 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 (Xex<Xem), though in specific embodiments the luminescent material may comprise up-converter luminescent material, i.e. radiation of a larger wavelength is converted into radiation with a smaller wavelength ( x> m).

[0084] 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.

[0085] The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. Instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art.

[0086] 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. Alternatively or additionally, the luminescent material(s) may be selected from silicates, especially doped with divalent europium.

[0087] In specific embodiments the luminescent material comprises a luminescent material of the type AsBsOn Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. Embodiments of garnets especially include A3B5O12 garnets, wherein A comprises at least yttrium or lutetium and wherein B comprises at least aluminum. Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. Especially, B may comprise aluminum (Al); however, in addition to aluminum, B may also partly comprise gallium (Ga) and / or scandium (Sc) and / or indium (In), especially up to about 20% of B, more especially up to about 10 % of B (i.e. the B ions essentially consist of 90 or more mole % of Al and 10 or less mole % of one or more of Ga, Sc and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and / or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Yi-xLux)3B50i2:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Yi-xLux)3A150i2:Ce, part of Y and / or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Yo.iLuo.89Ceo.oi)3A150i2. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art.

[0088] In embodiments, the luminescent material (thus) comprises A3B5O12 wherein in specific embodiments at maximum 10% of B-0 may be replaced by Si-N.

[0089] In specific embodiments the luminescent material comprises (YxiA’X2CeX3)3(AlyiB’y2)5Oi2, wherein xl+x2+x3=l, wherein x3>0, wherein 0<x2+x3<0.2, wherein yl+y2=l, wherein especially 0<y2<0.2, wherein A’ comprises one or more elements selected from the group consisting of lanthanides, and wherein B’ comprises one or more elements selected from the group consisting of Ga, In and Sc. In embodiments, x3 is selected from the range of 0.001-0.1. In the present invention, especially xl>0, such as >0.2, like at least 0.8. Garnets with Y may provide suitable spectral power distributions.

[0090] In specific embodiments at maximum 10% of B-0 may be replaced by Si-N. Here, B in B-0 refers to one or more of Al, Ga, In and Sc (and O refers to oxygen); in specific embodiments B-0 may refer to Al-O. As indicated above, in specific embodiments x3 may be selected from the range of 0.001-0.04. Especially, such luminescent materials may have a suitable spectral distribution (see however below), have a relatively high efficiency, have a relatively high thermal stability, and allow a high CRI (optionally in combination with (the) light of other sources of light as described herein). Hence, in specific embodiments A may be selected from the group consisting of Lu and Gd. Alternatively or additionally, B may comprise Ga. Hence, in embodiments the luminescent material comprises (Yxi(Lu,Gd)x2Cex3)3(AlyiGay2)5Oi2, wherein Lu and / or Gd may be available. Even more especially, x3 is selected from the range of 0.001-0.1, wherein 0<x2+x3<0.1, and wherein 0<y2<0.1. Further, in specific embodiments, at maximum 1% of B-0 may be replaced by Si- N. Here, the percentage refers to moles (as known in the art); see e.g. also EP3149108. In yet further specific embodiments, the luminescent material comprises (YxiCexs^ALOn, wherein xl+x3=l, and wherein 0<x3<0.2, such as 0.001-0.1.

[0091] In specific embodiments, the light generating device may only include luminescent materials selected from the type of cerium comprising garnets. In even further specific embodiments, the light generating device includes a single type of luminescent materials, such as (YxiA’x2Cex3)3(AlyiB’y2)5Oi2. Hence, in specific embodiments the light generating device comprises luminescent material, wherein at least 85 weight%, even more especially at least about 90 wt.%, such as yet even more especially at least about 95 weight % of the luminescent material comprises (YxiA’x2CeX3)3(AlyiB’y2)5Oi2. Here, wherein A’ comprises one or more elements selected from the group consisting of lanthanides, and wherein B’ comprises one or more elements selected from the group consisting of Ga, In and Sc, wherein xl+x2+x3=l, wherein x3>0, wherein 0<x2+x3<0.2, wherein yl+y2=l, wherein 0<y2<0.2. Especially, x3 is selected from the range of 0.001-0.1. Note that in embodiments x2=0. Alternatively or additionally, in embodiments y2=0.

[0092] In specific embodiments, A may especially comprise at least Y, and B may especially comprise at least Al. Alternatively or additionally, the luminescent material may comprise a luminescent material of the type AsSieNiuCe3, wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y.

[0093] In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu2+and / or LSisNs Eu2and / or MAlSiNs Eu2and / or Ca2AlSi3O2Ns:Eu2+, etc., wherein M comprises one or more of Ba, Sr and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2SisN8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu2+). For instance, assuming 2% Eu in CaAlSi Eu, the correct formula could be (Cao.98Euo.o2)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr or Ba. The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Further, the material (Ba,Sr,Ca)2SisN8:Eu can also be indicated as NfcSis Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and / or Ba. In a further specific embodiment, M consists of Sr and / or Ba (not taking into account the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Bai.sSro.sSis Eu (i.e. 75 % Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca). Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSi Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art. In embodiments, a red luminescent material may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2SisN8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu2+). For instance, assuming 2% Eu in CaAlSi Eu, the correct formula could be (Cao.98Euo.o2)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr or Ba.

[0094] The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca).

[0095] Further, the material (Ba,Sr,Ca)2SisN8:Eu can also be indicated as NfcSis Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and / or Ba. In a further specific embodiment, M consists of Sr and / or Ba (not taking into account the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Bai.sSro.sSis Eu (i.e. 75 % Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca).

[0096] Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSi Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca).

[0097] Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.

[0098] The term “luminescent material” herein especially relates to inorganic luminescent materials.

[0099] Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and / or organic dyes may be applied and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc. etc. Quantum dots are small crystals of semiconducting material generally having a width or diameter of only a few nanometers. When excited by incident light, a quantum dot emits light of a color determined by the size and material of the crystal. Light of a particular color can therefore be produced by adapting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with a shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium free quantum dots such as indium phosphide (InP), and copper indium sulfide (CuInS?) and / or silver indium sulfide (AglnS?) can also be used. Quantum dots show very narrow emission band and thus they show saturated colors. Furthermore the emission color can easily be tuned by adapting the size of the quantum dots. Any type of quantum dot known in the art may be used in the present invention. However, it may be preferred for reasons of environmental safety and concern to use cadmium-free quantum dots or at least quantum dots having a very low cadmium content.

[0100] Instead of quantum dots or in addition to quantum dots, also other quantum confinement structures may be used. The term “quantum confinement structures” should, in the context of the present application, be understood as e.g. quantum wells, quantum dots, quantum rods, tripods, tetrapods, or nanowires, etcetera.

[0101] In embodiments, the luminescent material is comprised by a body, such as a ceramic body or a glass body or a polymeric body, especially a ceramic body.

[0102] Especially, instead of the term “s-polarized light”, and similar terms, also the term “linear s-polarized light” may be applied. Further, especially, instead of the term “p- polarized light”, and similar terms, also the term “linear p-polarized light” may be applied.

[0103] 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. Herein, UV may especially refer to a wavelength selected from the range of 190-380 nm, such as 200-380 nm.

[0104] The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to (at least) visible light.

[0105] The terms “violet light” or “violet emission”, and similar terms, may especially relate to light having a wavelength in the range of about 380-440 nm. In specific embodiments, the violet light may have a centroid wavelength in the 380-440 nm range. The terms “blue light” or “blue emission”, and similar terms, may especially relate to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues). In specific embodiments, the blue light may have a centroid wavelength in the 440-490 nm range. The terms “green light” or “green emission”, and similar terms, may especially relate to light having a wavelength in the range of about 490-560 nm. In specific embodiments, the green light may have a centroid wavelength in the 490-560 nm range. The terms “yellow light” or “yellow emission”, and similar terms, may especially relate to light having a wavelength in the range of about 560-590 nm. In specific embodiments, the yellow light may have a centroid wavelength in the 560-590 nm range. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590-620 nm. In specific embodiments, the orange light may have a centroid wavelength in the 590-620 nm range. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-750 nm. In specific embodiments, the red light may have a centroid wavelength in the 620-750 nm range. The terms “cyan light” or “cyan emission”, and similar terms, especially relate to light having a wavelength in the range of about 490-520 nm. In specific embodiments, the cyan light may have a centroid wavelength in the 490-520 nm range. The terms “amber light” or “amber emission”, and similar terms, may especially relate to light having a wavelength in the range of about 585-605 nm, such as about 590-600 nm. In specific embodiments, the amber light may have a centroid wavelength in the 585-605 nm range. The phrase “light having one or more wavelengths in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least intensity or intensities at these one or more wavelengths in the indicate wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at one or more wavelengths in the 440-490 nm wavelength range.

[0106] 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.

[0107] The control system may also be configured to receive and execute instructions from 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.

[0108] 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, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

[0109] The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. The term “operational mode may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational 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.

[0110] 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).

[0111] 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.

[0112] Further, in embodiments the luminescent material or the diffuser element or both may be configured in thermal contact with a thermally conductive material. For instance, the luminescent material may be configured in thermal contact with a thermally conductive element. A thermally conductive element may especially comprise thermally conductive material. A thermally conductive material may especially have a thermal conductivity of at least about 20 W / (m*K), like at least about 30 W / (m*K), such as at least about 100 W / (m*K), like especially at least about 200 W / (m*K). In yet further specific embodiments, a thermally conductive material may especially have a thermal conductivity of at least about 10 W / (m*K). In embodiments, the thermally conductive material may comprise one or more of copper, aluminum, silver, gold, silicon carbide, aluminum nitride, boron nitride, aluminum silicon carbide, beryllium oxide, a silicon carbide composite, aluminum silicon carbide, a copper tungsten alloy, a copper molybdenum carbide, carbon, diamond, and graphite. Alternatively, or additionally, the thermally conductive material may comprise or consist of aluminum oxide. In embodiments, the thermally conductive element may comprise one or more of a heatsink, a heat spreader, and a two-phase cooling device. In yet other embodiments, the thermally conductive element may be configured in thermal contact with one or more of a heatsink, a heat spreader, and a two-phase cooling device, and may e.g. transfer heat to such heatsink, heat spreader, or two-phase cooling device, via another thermally conductive element. An element may be considered in “thermal contact” with another element if it can exchange energy through the process of heat. Hence, the elements may be thermally coupled. In embodiments, thermal contact can be achieved by physical contact. In embodiments, thermal contact may be achieved via a thermally conductive material, such as a thermally conductive glue (or thermally conductive adhesive). Thermal contact may also be achieved between two elements when the two elements are arranged relative to each other at a distance of equal to or less than about 10 pm, though larger distances, such as up to 100 pm may be possible. The shorter the distance, the better the thermal contact. Especially, the distance is 10 pm or less, such as 5 pm or less, such as 1 pm or less. The distance may be the distanced between two respective surfaces of the respective elements. The distance may be an average distance. For instance, the two elements may be in physical contact at one or more, such as a plurality of positions, but at one or more, especially a plurality of other positions, the elements are not in physical contact.

[0113] The light generating system 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, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating system (or luminaire) may be part of or may be applied in e.g. optical communication systems or disinfection systems.

[0114] In yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a lighting device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system as defined herein. The lighting device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system. For instance, in embodiments the lighting device may comprise a housing or a carrier, configured to house or support one or more of the first light generating device, the second light generating device, the optics, etc.

[0115] BRIEF DESCRIPTION OF THE DRAWINGS

[0116] 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. 1-3 schematically depict some embodiments;

[0117] Fig. 4 schematically depicts a diffusion profile of a top-hat diffuser;

[0118] Figs. 5A-5B show some measurements; and

[0119] Fig. 6 schematically depict some application embodiments. The schematic drawings are not necessarily to scale.

[0120] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0121] Laser-phosphor systems are known for their ability to generate high brightness light and are therefore increasingly used in projection systems, including displays such as cinema projectors and projectors for home, school, and office applications, car front lighting, search lighting, stage lighting, architectural lighting, and special lighting applications. In many cases the light engine is capable to generate only a single color point as defined by the luminescent converter. Creation of a product range providing different color points is in this case costly as it requires multiple unique components to be designed, qualified, produced, and kept in stock. In other cases, e.g. in RGB LCD-based projection systems, the maximum brightness is limited by the components used, the engine volume is large due to the many components, and the system cost are high due to the many dedicated components. A possible method to combine pump-light and luminescent light is to use a polarizing beam splitter for the pump light, by which part of the light is reflected to the luminescent material and part is transmitted to a diffuser. However, in general the diffused light appears be to a large degree depolarized, resulting in relatively high losses of diffused blue light at the beam combiner where it is combined with the luminescent light into white output light.

[0122] As the engine output light may in an operational mode be a superposition of diffused device light and (device light converted into) luminescent light, the color uniformity depends on the relative spatial and angular luminance distributions of the respective virtual sources. The actual luminance distribution of the luminescent light is in principle different from the luminance distribution of a pure diffuser due to different absorption and scattering coefficients and differences in effective diffusion lengths. Such differences may be reduced by applying some additional scattering in one or both of the two color channels. However, it’s not only the full width at half maximum (FWHM) of the two distributions that may differ, but in fact the entire shape of the spatial distribution (as well as the angular distribution). With a single type of impacting optical component these two aspects cannot be tuned independently, and consequently there remains to be color non-uniformity in the beam, as efficiency requirements put significant limitations to the degree of diffusion that may be applied and to the minimum part / fraction of the beam that is emitted from the engine.

[0123] In embodiments, this invention may provide a light engine architecture comprising two different types of optical elements / functions. This may enable far better color homogenization in high brightness and high flux laser-phosphor engines than what is observed from commercially available devices in which just a single diffuser is added, while is still is highly efficient.

[0124] Amongst others, it is herein proposed to use a first transmissive diffuser to provide just sufficient homogenization as well as beam shaping to the device light (laser) beams directed to a luminescent converter and to a reflective diffuser to result, in combination with condenser lenses, in the requested spot size and source etendue of primarily the luminescent spot, an optional second transmissive diffuser in the device light beam that is projected onto the reflective diffuser, a first set of two condenser lenses to project device light onto the luminescent converter, a second set of two condenser lenses to project device light onto the reflective diffuser, where the condenser lenses in each of the first and the second set differ in effective numerical aperture and where the lenses in the two sets are identical, but where the inter-lens distance in the two sets of condenser lenses and optionally the distance from lens to target (i.e., diffuse reflector or luminescent material) as well is different. By selecting carefully an optimal distance between the two condenser lenses in the second lens set that is smaller than that in the first lens set, optionally in combination with the selection of the scattering characteristics of the second transmissive diffuser, where the degree of diffusion of the optional second transmissive diffuser is smaller than that of the first transmissive diffuser, improved color homogeneity at equal system efficiency compared to a system with two identical optical branches, or both improved color homogeneity and improved system efficiency, can be achieved.

[0125] Referring to Figs. 1-3, embodiments of a light generating system 1000 comprising a first light generating device 110, a second light generating device 120, a luminescent material 200, a diffuser element 710, optics 500, and a control system 300 are schematically depicted.

[0126] The optics 500 may comprise (a) a first beam splitter arrangement 1500, especially comprising a dichroic beam splitter, configured between the first light generating device 110 and the luminescent material 200, and (b) a second beam splitter arrangement 2500, especially comprising a polarizing beam splitter, configured between the second light generating device 120 and the diffuser element 710. The first beam splitter arrangement 1500 may comprise a dichroic beam splitter, and the second beam splitter arrangement 2500 comprises a first polarizing beam splitter.

[0127] The first light generating device 110 may be configured to generate first device light 111, having a first peak wavelength XL The first light generating device 110 may comprise a first solid state light source 10, such as a laser diode. The second light generating device 120 may be configured to generate second device light 121, having a second peak wavelength X2. The second light generating device 120 may comprise a second solid state light source 20, such as a laser diode. In embodiments, the first peak wavelength XI and the second peak wavelength X2 may individually be selected from the wavelength range of 430- 490 nm.

[0128] Especially, the optics 500 and the second light generating device 120 are configured such that the second device light 121, wherein incident on the second beam splitter arrangement 2500, comprises polarized light having a p-polarization or an s- polarization.

[0129] Further, the luminescent material 200 may be configured to convert first device light 111 received by the luminescent material 200 into luminescent material light 201. Further, the diffuser element 710 may be configured to diffuse at least part of the second device light 121 received by the diffuser element 710 thereby providing diffused second device light 711 while maintaining at least part of the polarization of the second device light 121 incident on the diffuser element 710. Yet, the luminescent material 200 and the diffuser element 710 may be configured in the reflective mode, as schematically depicted.

[0130] Further, one of the beam splitter arrangements 1500,2500 may also configured to combine the luminescent material light 201 and diffused second device light 711 received by that beam splitter arrangement.

[0131] Yet, the optics 500 may further comprise (c) a first lens arrangement 1510, configured between the first beam splitter arrangement 1500 and the luminescent material 200, and d a second lens arrangement 1520, configured between the second beam splitter arrangement 2500 and the diffuser element 710. The first lens arrangement 1510 may comprise a first primary lens LI 1 and a second primary lens L12. The first primary lens LI 1 and the second primary lens L12 have a first inter-lens distance dl. The second lens arrangement 1520 may comprise a first secondary lens L21, and a second secondary lens L22. The first secondary lens L21 and the second secondary lens L22 have a second interlens distance d2. In embodiments, | l-d2 / dl |>0.1. The optics 500 may further comprise e a primary angular spreader TD11, configured between the first light generating device 110 and the first lens arrangement 1510, and f a secondary angular spreader TD12, configured between the second light generating device 120 and the second lens arrangement 1520. Especially, the primary angular spreader TD11 may be configured to diffuse first device light 111 received by the primary angular spreader TD11 and the secondary angular spreader TD12 may be configured to diffuse second device light 121 received by the secondary angular spreader TD12. The primary angular spreader TD11 may have a first diffusion angle 01, defined at full width half maximum, selected from the range of 1-15°, like selected from the range of 1-10°. The secondary angular spreader TD12 may have a second diffusion angle 92, defined at full width half maximum, selected from the range of 1-15°, like selected from the range of 1-10°. In embodiments, 92 / 91>l.

[0132] Especially, the primary angular spreader TD11 may be configured between the first light generating device 110 and the first beam splitter arrangement 1500, and the secondary angular spreader TD12 may be configured between the second light generating device 120 and the second beam splitter arrangement 2500.

[0133] Especially, the light generating system 1000 is configured to generate system light 1001 comprising one or more of luminescent material light 201 and diffused second device light 711. The control system 300 may be configured to control a spectral power distribution of the system light 1001, amongst others by controlling the light generating devices, though other optional options are also described herein.

[0134] The first solid state light source 10 and the second solid state light source 20 may individually be selected from the group of a laser diode, a multi -junction light emitting diode, a superluminescent diode, and (laser) diode array. In embodiments, laser diodes may be applied.

[0135] Especially, the first primary lens Li l has a first primary optical power Pl 1 and the second primary lens L12 has a second primary optical power P12. In embodiments, P12>P11. Further, especially the first secondary lens L21 has a first secondary optical power P21 and the second secondary lens L22 has a second secondary optical power P22. In embodiments, P22>P21.

[0136] Especially, the luminescent material 200 and the first lens arrangement 1510 have a first shortest distance xl and the diffuser element 710 and the second lens arrangement 1520 have a second shortest distance x2. In embodiments, x2^xl though in other embodiments x2=xl. As schematically depicted, the system 1000 may further comprise a polarization change element 810. In embodiments, the polarization change element 810 may comprise a X / 4 waveplate. Especially, the polarization change element 810 may be configured between second beam splitter arrangement 2500 and the second lens arrangement 1520.

[0137] Reference IL refers to an optional integrated optics, like integrator lens, which may be comprised by the optics 500. Reference EL refers to an exit lens, which may be comprised by the optics 500. Reference AP refers to an exit opening or aperture, which may be comprised by the optics 500. Reference M refers to a mirror, which may be comprised by the optics 500. Multiple mirrors may be comprised by the optics 500.

[0138] Referring to Figs. 2-3, the light generating system 1000 may further comprising (i) a third light generating device 130, and (ii) a third beam combiner 3500, such as a second polarizing beam combiner 3525.

[0139] The third light generating device 130 may be configured to generate third device light 131, having a third peak wavelength 3. The third light generating device 130 may comprise a third solid state light source 30 selected from a laser diode, multi -junction light emitting diode, a multi -junction light emitting diode, and a superluminescent diode, and a diode array.

[0140] In embodiments, the third device light 131 may comprise polarized light having a p-polarization or an s-polarization. Especially, the first device light 111 may comprise polarized light having a p-polarization or an s-polarization, while the polarization of the first device light 111 and the third device light 131 differ. The second polarizing beam combiner 3525 may be configured upstream of the first beam splitter arrangement 1500 and is configured to combine the first device light 111 and the third device light 131 received by the second polarizing beam splitter 3525 and direct to the first beam splitter arrangement 1500.

[0141] Alternatively, the beam combiner 3500 may be a dichroic beam combiner when the wavelengths of the first device light 111 and the third device light 131 are sufficiently different).

[0142] Referring to Figs. 2-3, the second beam splitter arrangement 2500 may comprise polarizing beam splitting and dichroic beam combiner functionalities.

[0143] Referring to Fig. 3, the light generating system 1000 may further comprises a polarization controlling element 610. In embodiments, the polarization controlling element 610 may comprise a birefringent rotator. Other embodiments are also described above, such as a waveplate, a retarder, or an actuator configured to rotate the third light generating device.

[0144] The polarization controlling element 610 may be configured between the second light generating device 120 and the second beam splitter arrangement 2500, and may be configured to control the polarization of the second device light 121 received by the second beam splitter arrangement 2500. Especially, the second beam splitter arrangement 2500 may be configured (a) such that: in dependence of the polarization of the second device light 121, second device light 121 is directed to the first beam splitter arrangement 1500 or to the diffuser element 710, and (b) to combine diffused second device light 711 and luminescent material light 201 received by the second beam splitter arrangement 2500.

[0145] Referring to Fig. 2, the light generating system 1000 may further comprise a tertiary angular spreader TD13, configured between (i) the second beam splitter arrangement 2500 and the second lens arrangement 1520 depicted in Fig. 2 or (ii) the first beam splitter arrangement 1500 and the second beam splitter arrangement 2500, not depicted. Especially, the tertiary angular spreader TD13 has a third diffusion angle 03 selected from the range of 1- 15°, like selected from the range of 1-10°.

[0146] In an operational mode of the light generating system 1000, the system light 1001 may comprise both the luminescent material light 201 and diffused second device light 711. For instance, the system light 1001 may have a correlated color temperature selected from the range of 1500-12000 K and a color rendering index of at least 65.

[0147] Referring to Figs. 1-3, one or more of the luminescent material 200 and the diffuser element 710 may be comprised by the rotatable element 1200 here, embodiments are depicted where both are comprised by the rotatable element 1200. The control system 300 may be configured to control rotation of the rotatable element 1200 in an operational mode of the light generating system 1000.

[0148] In specific embodiments, such as schematically depicted in Figs. 1-2, the first beam splitter arrangement 1500 may be configured in a light receiving relationship with the second beam spitter arrangement 2500, and may also have the function of a beam combiner.

[0149] In specific embodiments, such as schematically depicted in Fig. 3, the second beam splitter arrangement 2500 may be configured in a light receiving relationship with the first beam spitter arrangement 1500, and may also have the function of a beam combiner. Especially, the dichroic functionality may be found in the requirement of the element to be transmissive for luminescent light while being reflective for s-polarized (second) device light and thus combine luminescent light with s-polarized (second) device light The transmissive diffusers may especially be transmissive top-hat diffusers with a diffusion angle as indicated above. Likewise this may apply to other angular spreaders. Basically, the function of the transmissive diffusers may be two-or three-fold: 1. Homogenization of the device light beams that may comprise multiple individual collimated laser diode beams (from a laser bank), i.e., reduce the hot spots in the overall beam; 2. Increase the divergence of the beams to achieve a targeted spot diameter on the reflective diffuser and on the luminescent material, such as the targeted full width at half maximum (FWHM) value; 3. Optionally adjust the spatial (or radial) beam profile on the target planes (i.e., at the reflective diffuser and at the luminescent material) to achieve the targeted radial profiles by adjustment of the angular profiles of the device light beams. This may be realized by engineered diffusers, diffractive diffusers, volume and / or surface textured diffusers, or by regular or irregular lens arrays, either as single lens arrays or as lens array pairs such as the well-known fly-eye lens array pairs or Kohler integrators.

[0150] The optional third angular spreader may typically have small-angle diffusion characteristics with a mean diffusion angle 03 that may be smaller than that of first and second angular spreaders, especially only 50%, or even only 25% thereof. The exact functionality (or type of impact) of TD13 may depend on its location in the system. Depending on the diffusion profile it may have different impact on the spatial distribution of the device light at the reflective diffuser. E.g., it may be used to change the slope of the radial irradiance distribution while keeping the beam width (e.g. the FWHM) more or less constant. Additionally, it may diffuse the diffused light reflected from the reflective diffuser as well, thereby also increasing the diameter of the image on the aperture that is typically located outside of the laser-phosphor engine, yet inside the fixture that provides the final output beam with adjustable beam angle, beam shape, etc.

[0151] Fig. 4 schematically depicts a diffusion provide of a top-hat diffuser. On the x- axis the diffusion angle (here 9) is indicated. On the y-axis a relative intensity is indicated. The arrow indicates the value of the FWHM (full width at half-maximum intensity) diffusion angle.

[0152] For achieving high system efficiency and manageable system dimensions (e.g., limited diameters of the optical components and limited increase of the beam diameters inside the light engine) the projected device light spots on the reflective diffuser and the luminescent material may be relatively small, and the light collection angles of the lenses in front of these surfaces may be relatively large (e.g., > 70°, such as > 80°). The associated numerical apertures of a condenser lens assembly may not be realized by a single lens; therefore the condenser assemblies may typically comprise 2 or even 3 (condenser) lenses. Typically, at least one of the lenses is an aspherical lens, e.g. LI. For the LI 1,L21 lenses, the absorption of blue laser light through 10 mm of the glass material may be < 2% and the thermal expansion coefficient of the glass material may be < IE'5. For the L21,L22 lenses, the absorption through 10 mm of the material may be < 1%, such as < 0.5%, and the thermal expansion coefficient may be < 5E'6, such as < IE'6. Suitable glass materials for one or both of the lenses are e.g. N-BK7, H-K9L, or fused silica.

[0153] The reflective diffuser typically may be a surface textured and metal or metallized substrate material that substantially maintains the degree of polarization. I.e., incident linearly polarized light may substantially remain linearly polarized while maintaining the plane of polarization, and circularly polarized light would substantially remain circularly polarized albeit with inversed direction (i.e., incident left-circularly- polarized light would return upon reflection as right-circularly polarized light). However, other reflective diffusion implementations that are substantially polarization maintaining are possible as well.

[0154] The luminescent material may be either configured as a static converter or a dynamic converter such as a rotating disc (“phosphor wheel”) comprising a ring-shaped (full / monolithic or segmented) luminescent conversion element.

[0155] Referring to Figs. 2-3, in an alternative embodiment the device light beam used to excite the luminescent material may be composed of two device light beams with orthogonal polarizations. These two device light beams are provided by two device light sources that typically each comprise multiple laser diodes with corresponding collimator lenses, and are combined by a polarizing beam combiner (or polarizing beam splitter, PBS). An additional mirror is introduced to enable the three device light sources to be mounted on a shared heat spreader to spread and transfer the heat to a further heat sink and eventually to ambient. When in such configurations a third device light source is used for the blue channel light, significantly less power output is needed from this third light source (typically, for a CCT of ca. 7000K, in a 1 :4 ratio with respect to the pump device light used to excite luminescent converter). Therefore, for efficient spreading of the thermal power in a heat spreader plate, this second device light is preferably located in between the two first device light sources to realize the lowest possible laser diode temperatures.

[0156] Fig. 2 shows a configuration that has been realized experimentally and from which measurement results have been taken. For optimization of the system, first the position of the exit lens needs to be determined for a given position of the aperture. Both the power throughput and the irradiance profile at the aperture need to be optimized. Measurements have been performed to determine the dependence of the luminescent throughput power as a function of the inter-lens distance dl with the exit lens position as a parameter. A requirement in entertainment applications may be to have an irradiance at the edge that is not less than 70% of the center irradiance. This requirement could be met by choosing the exit lens position at a suitable position and the inter-lens distance dl at ca 3.15 mm, in which case the efficiency is still close to maximum. Therefore, this setting of dl = 3.15 mm serves as a reference.

[0157] The first and second angular spreaders may typically be top-hat diffusers with essentially the same diffusion profiles, such as profiles with a 4 or 5 degrees half width at half maximum (HWHM) diffusion angle (sometimes called the diffusion half-angle). The impact of changing the diffusion angle of the top-hat diffuser TD12 in the blue color channel on the illuminance profile is presented in Fig. 5a. Herein a dotted line Ty TH5 refers to illuminance profile distribution of the luminescent material light at the exit opening / aperture AP while using TD11 diffuser with HWHM = 5deg - a reference distribution; Tz TH5 refers to illuminance profile distribution of the blue color channel at the AP with TD12 diffuser with HWHM = 5deg; Tz TH4 refers to illuminance profile distribution of the of the blue color channel at the AP with TD12 diffuser with HWHM = 4°.

[0158] From this Fig. 5a we clearly see that the width (e.g., the FWHM) of the blue profile (“Tristimulus Z”, Tz) increases when changing from a 4° HWHM top-hat diffuser (TH4) to a 5° HWHM top-hat diffuser (TH5). The dashed curve is the profile of the luminescent channel (“Tristimulus Y”, Ty) with a 5° HWHM top-hat diffuser, and this is the targeted profile for the blue channel. Therefore, still some further spatial broadening of the blue spot may be desirable, but there may also be still some adaptation of the flanks of the profile desirable to get to improve matching for good color uniformity in the white light output beam of the module.

[0159] In order to quantify the color uniformity, measurements have been performed by imaging the light distribution at the exit aperture (i.e., the light focused by the exit lens EL on the aperture AP that typically is externally from the laser-phosphor light engine but inside the fixture providing the final beam) on a screen using an achromatic lens. With a luminance camera, an image can be taken of the resulting beam profiles and the X, Y and Z tristimulus values can be extracted. Increasing the color uniformity is done by matching the Z tristimulus profile, which is mostly influenced by the blue channel, to the Y tristimulus profile, which is a measure for the luminescent channel beam profile. The blue channel profile can be adapted by using an additional diffuser, and / or changing the inter-lens distance d2, and / or changing the lens-to-reflective-diffuser distance x2. The effect of the first two types of adaptations on the diffused device light output beam profile is visualized in Fig. 5B. In this figure, cross-sections of the normalized tristimulus values retrieved from a camera measurement showing the effect of different d2 distances (left plot), and of different types of added diffusers and its position (right plot). The tristimulus Y graph is used as a target for the tristimulus Z graph. In both channels TH4 (i.e., a top-hat diffuser with 4° HWHM) is used and an aperture with a diameter of 6 mm is placed. In the left figure Ty refers to illuminance profile distribution of the luminescent material light at the AP; Tz 2.50 mm refers to illuminance profile distribution of the blue color channel at the AP with d2 = 2.5mm; Tz 3.15 mm refers to illuminance profile distribution of the blue color channel at the AP with d2 = 3.15mm; Tz 1.5 mm refers to illuminance profile distribution of the blue color channel at the AP with d2 = 1.5mm. In the right part of the Figure 5B, Ty refers to illuminance profile distribution of the luminescent material light at the AP; Tz A refers to illuminance profile distribution of the blue color channel at the AP with additional Hl type TD13 diffuser; Tz B refers to illuminance profile distribution of the blue color channel at the AP without any additional TD13 diffuser; and Tz C refers to illuminance profile distribution of the blue color channel at the AP with additional TH1.5 type TD13 diffuser. The position of the TD13 diffuser for all these cases in the Figure 5B corresponds to its position on the drawing of Figure 2.

[0160] Here, and indication Hl would refer to a 1 degree HWHM Gaussian diffuser, and TH1 would refer to a 1 degree HWHM top-hat diffuser, and TH1.5 would refer to a 1.5 degree HWHM top-hat diffuser, etc.. The Tristimulus Y profile (dotted curves Ty in Figure 5B) shows the luminescent distribution and acts as the target for the blue distribution. Changing the inter-lens distance has a different influence on the blue channel profile compared to adding a diffuser. While the FWHM changes with a different inter-lens distance, the addition of a small-angle diffuser has little to no influence on the FWHM. This latter observation can be understood since the addition of a diffuser can be modeled as a convolution of the two diffuser profiles, which, for a combination of top-hat diffusers, influences the slope of the tails but not the FWHM. For the combination of (generalized) Gaussian diffusers both the FWHM and the slope of the radial profiles are affected, and the FWHM can be determined from quadratic summation of the individual contributors. In this case, if one is small with respect to the other, it doesn't change the FWHM much (e.g. H5 x Hl — > sqrt(25+l) ). In the preferred case of using top-hat diffusers, changing (i.e., reducing) the d2 distance to 2.0 mm gives a very acceptable color uniformity (color variation in du ’v ’<=0.01 along the beam cross-section) and no additional diffuser is required. There may be other luminescence profiles, however, that would require addition of a diffuser to change the shape or slopes of the profile.

[0161] Several parameters of interest have been tested as a function of inter-lens distance and as a function of the degree of diffusion. It was found that the FWHM in the blue channel increases with decreasing inter-lens distance d2. Further, was found the FWHM is substantially independent of the degree of diffusion of an additional diffuser. It was found that the slope of the luminance profile decreases with decreasing inter-lens distance d2, while it decreases with increasing degree of diffusion of an additional diffuser. Since the deformation of the illuminance profile as a result of changing d2 or as a result of changing the degree of diffusion is quite different (i.e., not opposite but complementary), a combination of both operations may be used to reach the required color uniformity.

[0162] A good color uniformity is achieved when du’v’<0.010 (correlated with the requirement of acceptable color deviations within 5 SDCM). But also a good blue channel efficiency is requested. It was observed that by just changing the inter-lens distance, a better color uniformity may be achieved compared to adding a diffuser, while also having a relatively higher flux. This may be understood by the broadening of the tails that result from adding a diffuser, and by realizing that these tails are blocked by the aperture in the fixture that defines the edge of the beam. While dl = 3.15 mm, we see that we need to set d2 to a value somewhere between 1.5 and 2.0 mm, preferably ~1.7 mm. It might be possible to improve the overall performance a bit further by combining a d2 value somewhere in the range 1.75 - 2.25 mm with an additional small-angle TD13 with top-hat profile.

[0163] As mentioned before, a third parameter that may be adjusted to achieve optimal color uniformity in the output white light at the exit aperture is the distance x2 between the reflective diffuser and the condenser lens L22. Good results so far were achieved with x2 = xl. Some ray -trace simulations have been performed, to check the impact of varying x2. In a first ray -trace modelling experiment, the blue power at the exit aperture has been measured as a function of x2 with the inter-lens distance d2 as a parameter.

[0164] In the luminescent channel, xl = 0.8 mm and dl = 3.15 mm for a good luminescent irradiance profile at the exit aperture in combination with a good efficiency. It was found that at d2 = 2.0 mm the blue channel efficiency is optimal at x2 = 0.9 mm. Therefore, optimization of the system efficiency may be a driver for selection of x2 > xl, because we observe best overall performance for d2 significantly smaller than dl.

[0165] In a second ray trace modelling experiment, the blue irradiance profile at the exit aperture has been measured for multiple x2 values at an inter-lens distance d2 = 2.0 mm while keeping all other parameters constant. Amongst others, ray-trace simulated tristimulus Z profiles, corresponding primarily with the blue irradiance profiles, at the exit aperture for multiple values of the distance x2 between the reflective diffuser RD 710 and the condenser lens L22 located just in front of the RD, with the inter-lens distance d2 = 2.0 mm were executed. In this configuration, TD11 and TD12 are top-hat diffusers with HWHM = 4° (TH4), there is no TD13 diffuser present, and the exit aperture is 6 mm in diameter. For reference, the luminescent channel has been designed with xl = 0.8 mm and dl = 3.15 mm. It was derived from these modelling results that for a chosen inter-lens distance d2 near a preferred value as determined for x2 = xl, variation of x2 away from xl results in a reduced slope of the blue irradiance profile at the exit aperture as well as in a reduced FWHM. In other words, the distribution becomes more peaked, and less top-hat profiled. However, would d2 ~ dl be chosen, then the impact of variation of x2 may be different. Ray -trace modelling has been performed for this case as well. Ray-trace simulated tristimulus Z profiles, corresponding primarily with the blue irradiance profiles, at the exit aperture for multiple values of the distance x2 between the reflective diffuser RD 710 and the condenser lens L22 located just in front of the RD, with the inter-lens distance d2 = 3.25 mm were executed. In this configuration, TD11 and TD12 are top-hat diffusers with HWHM = 4deg (TH4), there is no TD13 diffuser present, and the exit aperture is 6 mm in diameter. For reference, the luminescent channel has been designed with xl = 0.8 mm and dl = 3.15 mm. In this case it was found that selecting x2 > xl has an opposite effect as compared to selecting x2 < xl; in the former situation a similar trend as before was found: the profile becomes more peaked and the slope of the irradiance profile reduces. In the latter situation, however, the profile becomes more top-hat shaped, and the slope of the irradiance profile increases.

[0166] Hence, it was found that changing x2 (substantially) from xl while using the same lenses in the condenser lens assemblies in the blue diffusion channel and the luminescent channel may be a very relevant option. This allows adjusting the blue irradiance profile to the luminescent irradiance profile for optimization of color uniformity and system efficiency. In an alternative embodiment of the embodiment schematically depicted in Fig. 1, an additional beam-shaping angular spreader may be placed between the second beam splitter arrangement 2500 (PBS) in the blue channel and the first beam splitter arrangement 1500 (DBS). This may have the advantage that the collection efficiency at the reflective diffuser is not impacted, as the spot on the reflective diffuser is not changed. At the same time, it gives the opportunity to modify the diameter of the projection of the (blue) diffused device light on an exit aperture that typically is placed downstream of the exit lens, independent of the luminescent light projection on this aperture. The additional transmissive small-angle diffuser may in this way not substantially impact the size of the device light spot as projected on the reflective diffuser but only impacts the size of the diffused device light spot on the (external) aperture, independent of the projection of the luminescent light on that aperture.

[0167] In an alternative embodiment of the embodiment schematically depicted in Fig. 1, an additional beam-shaping angular spreader may be placed between the second light generating device 120 providing the device light beam that is to be diffused by the reflective diffuser and the PBS that splits the reflectively diffused device light from the non-reflectively diffused device light that is projected onto the reflective diffuser. For this configuration, the diffuser broadens the spot that is projected onto the reflective diffuser and may alter the radial profile just as described before, but in this case it does not impact the diffuse reflected device light any at all. All the matching of the luminescent and the device light projections on the (external) aperture is done by optimization of the luminance distributions on the reflective diffuser and on the luminescent material. The additional transmissive small-angle diffuser may thus impact the size and / or irradiance profile of the device light spot as projected on the reflective diffuser but does not impact the projection of the diffused device light onto the (external) aperture.

[0168] In practice, the configurations as presented in the accompanying drawings appear to provide relatively good results in terms of balancing system efficiency, radiance profile and color uniformity at the exit aperture (given the limited set of components that we have available to experiment with).

[0169] Fig. 6 schematically depicts an embodiment of a luminaire 2 comprising the light generating system 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the light generating system 1000. Fig. 3 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig. 6 schematically depicts embodiments of a lighting device 1600 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system 1000 as described herein. In embodiments, such lighting device may be a lamp 1, a luminaire 2, a projector device 3, a disinfection device, or an optical wireless communication device. Lighting device light escaping from the lighting device 1600 is indicated with reference 1201. Lighting device light 1201 may essentially consist of system light 1001, and may in specific embodiments thus be system light 1001. Reference 1300 refers to a space, such as a room. Reference 1305 refers to a floor and reference 1310 to a ceiling; reference 1307 refers to a wall. Further embodiments of lighting device 1600 may be an entertainment light generating device, a (entertainment) spot fixture, a stage lighting device, a search light, etc.

[0170] 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” also includes 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". 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0175] 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. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method as described herein.

[0176] 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.

[0177] 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.

[0178] 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.

Claims

CLAIMS:

1. A light generating system (1000) comprising a first light generating device(110), a second light generating device (120), a luminescent material (200), a diffuser element (710), optics (500), and a control system (300); wherein the optics (500) comprise (a) a first beam splitter arrangement (1500), configured between the first light generating device (110) and the luminescent material (200), and (b) a second beam splitter arrangement (2500), configured between the second light generating device (120) and the diffuser element (710); the first light generating device (110) is configured to generate first device light (111), having a first peak wavelength I; wherein the first light generating device (110) comprises a first solid state light source (10); the second light generating device (120) is configured to generate second device light (121), having a second peak wavelength X2; wherein the second light generating device (120) comprises a second solid state light source (20); the optics (500) and the second light generating device (120) are configured such that the second device light (121), wherein incident on the second beam splitter arrangement (2500), comprises polarized light having a p-polarization or an s-polarization; the luminescent material (200) is configured to convert first device light (111) received by the luminescent material (200) into luminescent material light (201); the diffuser element (710) is configured to diffuse at least part of the second device light (121) received by the diffuser element (710) thereby providing diffused second device light (711) while maintaining at least part of the polarization of the second device light (121) incident on the diffuser element (710); the luminescent material (200) and the diffuser element (710) are configured in the reflective mode; wherein one of the beam splitter arrangements (1500,2500) is configured to combine the luminescent material light (201) and diffused second device light (711) received by that beam splitter arrangement; the optics (500) comprise (c) a first lens arrangement (1510), configured between the first beam splitter arrangement (1500) and the luminescent material (200), and(d) a second lens arrangement (1520), configured between the second beam splitter arrangement (2500) and the diffuser element (710); the first lens arrangement (1510) comprises a first primary lens (LI 1), and a second primary lens ( I 2), wherein the first primary lens (LI 1) and the second primary lens (L12) have a first inter-lens distance (dl); the second lens arrangement (1520) comprises a first secondary lens (L21), and a second secondary lens (L22), wherein the first secondary lens (L21) and the second secondary lens (L22) have a second inter-lens distance (d2); wherein | l-d2 / dl |>0.1; the optics (500) comprise (e) a primary angular spreader (TD11), configured between the first light generating device (110) and the first lens arrangement (1510), and (f) a secondary angular spreader (TD12), configured between the second light generating device (120) and the second lens arrangement (1520); the primary angular spreader (TD11) is configured to diffuse first device light (111) received by the primary angular spreader (TD11); the secondary angular spreader (TD12) is configured to diffuse second device light (121) received by the secondary angular spreader (TD12); the light generating system (1000) is configured to generate system light (1001) comprising one or more of luminescent material light (201) and diffused second device light (711); and the control system (300) is configured to control a spectral power distribution of the system light (1001).

2. The light generating system (1000) according to claim 1, wherein d2 / dl<0.9; wherein the first solid state light source (10) and the second solid state light source (20) are individually selected from the group of a laser diode, a multi -junction light emitting diode, a superluminescent diode, and diode array.

3. The light generating system (1000) according to any one of the preceding claims, wherein the first primary lens (LI 1) has a first primary optical power Pl 1, the second primary lens (LI 2) has a second primary optical power Pl 2, and wherein P12>P11; wherein the first secondary lens (L21) has a first secondary optical power P21, the second secondary lens (L22) has a second secondary optical power P22, wherein P22>P21.

4. The light generating system (1000) according to any one of the preceding claims, wherein the primary angular spreader (TD11) has a first diffusion angle 01, defined atfull width half maximum, selected from the range of 1-15°; wherein the secondary angular spreader (TD12) has a second diffusion angle 02, defined at full width half maximum, selected from the range of 1-15°; and wherein 02 / 01>l .

5. The light generating system (1000) according to claim 4, wherein 02 / 01> 1.1.

6. The light generating system (1000) according to any one of the preceding claims, wherein the luminescent material (200) and the first lens arrangement (1510) have a first shortest distance (xl), wherein the diffuser element (710) and the second lens arrangement (1520) have a second shortest distance (x2), wherein x2 / xl.

7. The light generating system (1000) according to claim 6, wherein x2 / xl<0.9.

8. The light generating system (1000) according to any one of the preceding claims, comprising a polarization change element (810), wherein the polarization change element (810) comprises a X / 4 waveplate, wherein the polarization change element (810) is configured between second beam splitter arrangement (2500) and the second lens arrangement (1520).

9. The light generating system (1000) according to any one of the preceding claims, wherein the first beam splitter arrangement (1500) comprises a dichroic beam splitter, and wherein the second beam splitter arrangement (2500) comprises a polarizing beam splitter; wherein the first peak wavelength XI and the second peak wavelength X2 are individually selected from the wavelength range of 430-490 nm.

10. The light generating system (1000) according to any one of the preceding claims, further comprising (i) a third light generating device (130), and (ii) a polarizing beam combiner (3525), wherein: the third light generating device (130) is configured to generate third device light (131), having a third peak wavelength X3; wherein the third device light (131) comprises polarized light having a p-polarization or an s-polarization; wherein the third light generating device (130) comprises a third solid state light source (30) selected from a laser diode, multijunction light emitting diode, a multi -junction light emitting diode, and a superluminescent diode, and a diode array;wherein the first device light (111) comprises polarized light having a p- polarization or an s-polarization; wherein the polarization of the first device light (111) and the third device light (131) differ; the polarizing beam combiner (3525) is configured upstream of the first beam splitter arrangement (1500) and is configured to combine the first device light (111) and the third device light (131) received by the second polarizing beam splitter (3525) and direct to the first beam splitter arrangement (1500).

11. The light generating system (1000) according to any one of the preceding claims, wherein the second beam splitter arrangement (2500) comprises polarizing beam splitting and dichroic beam combiner functionalities; wherein the light generating system (1000) further comprises a polarization controlling element (610), wherein the polarization controlling element (610) comprises a birefringent rotator, wherein the polarization controlling element (610) is configured between the second light generating device (120) and the second beam splitter arrangement (2500), and is configured to control the polarization of the second device light (121) received by the second beam splitter arrangement (2500); wherein the second beam splitter arrangement (2500) is configured (a) such that: in dependence of the polarization of the second device light (121), second device light (121) is directed to the first beam splitter arrangement (1500) or to the diffuser element (710), and (b) to combine diffused second device light (711) and luminescent material light (201) received by the second beam splitter arrangement (2500).

12. The light generating system (1000) according to any one of the preceding claims, wherein the primary angular spreader (TD11) is configured between the first light generating device (110) and the first beam splitter arrangement (1500), and wherein the secondary angular spreader (TD12) is configured between the second light generating device (120) and the second beam splitter arrangement (2500).

13. The light generating system (1000) according to any one of the preceding claims, further comprising a tertiary angular spreader (TD13), configured between (i) the second beam splitter arrangement (2500) and the second lens arrangement (1520) or (ii) the first beam splitter arrangement (1500) and the second beam splitter arrangement (2500); wherein the tertiary angular spreader (TD13) has a third diffusion angle (03) selected from the range of 1-10°.

14. The light generating system (1000) according to any one of the preceding claims, wherein in an operational mode of the light generating system (1000) the system light (1001) comprises both the luminescent material light (201) and diffused second device light (711), has a correlated color temperature selected from the range of 1500-12000 K and a color rendering index of at least 65; wherein the first device light (111) and the second device light (121) are blue light; wherein one or more of the luminescent material (200) and the diffuser element (710) are comprised by the rotatable element (1200); wherein the control system (300) is configured to control rotation of the rotatable element (1200) in an operational mode of the light generating system (1000); and wherein the luminescent material (200) at least comprises a luminescent material of the type AsBsO Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc.

15. A lighting device (1600) selected from the group of a lamp (1), a luminaire (2), a projector device (3), a stage lighting device, a headlamp, and an optical wireless communication device, comprising the light generating system (1000) according to any one of the preceding claims.

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