Improved configuration for reducing phosphor heating in a blue light trap

Abstract

The invention provides a light generating system (1000) comprising a first light generating device (10), a first quarter wave plate (721), a polarization based beam director (1510), a dichroic filter (750), a luminescent material element (2000), and a light exit (1090), wherein: - the first light generating device (10) is configured to generate first device light (11); the luminescent material element (2000) is configured to convert part of the first device light (11) received by the luminescent material element (2000) into luminescent material light (201); - the light generating system (1000) is configured such that at least part of the reflected first device light (11), in an optical path (i) propagates away from the luminescent material element (2000) and (ii) also returns to the luminescent material element (2000); wherein this optical path is (a) at least twice via the polarization based beam director (1510), and (b) twice via the first quarter wave plate (721), whereby the luminescent material element (2000) converts at least part of the reflected first device light (11), received by the luminescent material element (2000) via this optical path, into further luminescent material light (201'); and - the light generating system (1000) is configured to generate system light (1001) comprising at least part of the luminescent material light (201) and at least part of the further luminescent material light (201').

Description

[0001] 2024PF80183

[0002] 1

[0003] Improved configuration for reducing phosphor heating in a blue light trap

[0004] FIELD OF THE INVENTION

[0005] The invention relates to a light generating system. The invention further relates to a lighting device comprising the light generating system.

[0006] BACKGROUND OF THE INVENTION

[0007] Lighting fixtures with built-in eye-safety are known in the art.

[0008] US2019323803 Al, for instance, describes a laser system comprising: an active laser with at least one beam guide and an effective range about an object / target when the active laser is in use; a protection device with at least one additional laser that operates in a visible spectral range, wherein the at least one additional laser is switched on if at least one person has been detected in the effective range of the active laser before the active laser is used.

[0009] US20190271907A1 discloses an illuminator that includes an array light source, a collimator system, a homogenizer system, an optical element that includes a polarization separation element, a retardation film, an optical integration system, a polarization conversion element and a wavelength conversion element for conversion of the light generated by the array light source. The optical element directs the light generated by the array light source to the wavelength conversion element and directs the converted light to the light exit.

[0010] SUMMARY OF THE INVENTION

[0011] 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 of generating 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 2024PF80183

[0012] 2 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, such prior art systems may have relatively high risks for eye-safety should one or more optical components break or malfunction. Therefore, it may be desired to improve the safety, compactness and / or performance / cost ratio of laser-phosphor technology.

[0013] 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 the above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0014] According to a first aspect, the invention provides a light generating system (“system”) comprising a first light generating device, a first retarder, such as a first quarter wave plate, a polarization based beam director (herein also indicated as “first polarizing beam splitter”), a dichroic filter, a luminescent material element, and a light exit. In embodiments, the first light generating device may be configured to generate first device light. Especially, the first light generating device may comprise a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multi -junction lightemitting diodes. Further, in embodiments the luminescent material element may be configured in a light receiving relationship with the first light generating device and may be configured to convert part of the first device light received by the luminescent material element into luminescent material light. Yet, in embodiments the light generating system may be configured such that at least part of the (generated) luminescent material light may propagate along an optical path via the dichroic filter to the light exit. Further, in embodiments the first retarder, especially the first quarter wave plate, and the polarization based beam director may be configured in an optical path between the first light generating device and the luminescent material element. Especially, in embodiments relative to a propagation of the first device light from the first light generating device to the luminescent material element, the first quarter wave plate may be configured downstream of the polarization based beam director. Yet, in embodiments the polarization based beam director may be configured to reflect or transmit (at least) first device light, received by the polarization based beam director, in dependence of its linear polarization. Further, in embodiments the light generating system may be configured such that the first device light from the first light generating device reaching the polarization based beam director may 2024PF80183

[0015] 3 comprise linear polarized light. Especially, in embodiments one or more of the following applies: (a) the light generating system may comprise a first reflector, configured downstream of the luminescent material element, wherein part of the first device light, received by the luminescent material element, may be transmitted by the luminescent material element, reflected at the first reflector, and transmitted (again) by the luminescent material element in an optical path to the polarization based beam director, thereby providing reflected first device light, and (b) part of the first device light may be reflected by the luminescent material element in an optical path to the polarization based beam director, thereby providing reflected first device light. In embodiments, the light generating system may (further) be configured such that at least part of the reflected first device light, in an optical path (i) may propagate away from the luminescent material element and (ii) may also return to the luminescent material element. Especially, (thereby) this optical path may be (a) at least twice via the polarization based beam director, and (b) twice (forth and back) via the first quarter wave plate, whereby the luminescent material element may convert at least part of the reflected first device light, received by the luminescent material element via this optical path, into further luminescent material light . Especially, the light generating system may be configured to generate system light comprising in embodiments at least part of the luminescent material light and at least part of the further luminescent material light (escaped from the light generating system via the light exit). Hence, in embodiments the invention provides a light generating system comprising a first light generating device, a first quarter wave plate, a polarization based beam director, a dichroic filter, a luminescent material element, and a light exit, wherein: (A) the first light generating device is configured to generate first device light; wherein the first light generating device comprises a solid state light source is selected from the group comprising laser diodes, superluminescent diodes, and stacked multi -junction light-emitting diodes; (B) the luminescent material element is configured in a light receiving relationship with the first light generating device and is configured to convert part of the first device light received by the luminescent material element into luminescent material light; wherein the light generating system is configured such that at least part of the (generated) luminescent material light propagates along an optical path via the dichroic filter to the light exit; (C) the first quarter wave plate and the polarization based beam director are configured in an optical path between the first light generating device and the luminescent material element, wherein relative to a propagation of the first device light from the first light generating device to the luminescent material element, the first quarter wave plate is configured downstream of the polarization based beam 2024PF80183

[0016] 4 director; (D) the polarization based beam director is configured to reflect or transmit (at least) first device light, received by the polarization based beam director, in dependence of its linear polarization; wherein the light generating system is configured such that the first device light from the first light generating device reaching the polarization based beam director comprises linear polarized light; (E) one or more of the following applies: (a) the light generating system comprises a first reflector, configured downstream of the luminescent material element; wherein part of the first device light, received by the luminescent material element, is transmitted by the luminescent material element, reflected at the first reflector, and transmitted (again) by the luminescent material element in an optical path to the polarization based beam director, thereby providing reflected first device light, and (b) part of the first device light is reflected by the luminescent material element in an optical path to the polarization based beam director, thereby providing reflected first device light; (F) the light generating system is (further) configured such that at least part of the reflected first device light, in an optical path (i) propagates away from the luminescent material element and (ii) also returns to the luminescent material element; wherein this optical path is (a) at least twice via the polarization based beam director, and (b) twice (forth and back) via the first quarter wave plate, whereby the luminescent material element converts at least part of the reflected first device light, received by the luminescent material element via this optical path, into further luminescent material light ; and (G) the light generating system is configured to generate system light comprising at least part of the luminescent material light and at least part of the further luminescent material light (escaped from the light generating system via the light exit).

[0017] Such a light generating system may provide high-brightness laser-phosphor based light. Furthermore, the light generating system may be relatively compact as a limited number of components are required. As a result, the system may further be relatively costefficient. Yet further, the light generating system of the invention may be relatively eye-safe in case of break or malfunction of components. Hence, the invention may provide an eye-safe high-brightness luminescent converter pumped by diffused laser light. Further, thinner luminescent material layers may be applied, as device light may be recycled. Thinner luminescent material layers may better be cooled. This may lead to a higher efficiency and / or a longer lifetime.

[0018] The light generating system (or “system”) may thus comprise a first light generating device, a first quarter wave plate, a polarization based beam director, a dichroic 2024PF80183

[0019] 5 filter, a luminescent material element, and a light exit. Here below, embodiments of the different elements of the light generating system will be described in further detail.

[0020] Especially, in embodiments during operation (linear polarized) first device light propagates via the polarization based beam director and the first quarter wave plate, where linear polarized light is converted into elliptical polarized light, to the luminescent material element, wherein at least part of the first device light is reflected. This reflection may be at the luminescent material, in the luminescent material, and via a reflector downstream of the luminescent material (see further also below). The reflected device light propagates (back) via the first quarter wave plate, where elliptical polarized light is converted into linear polarized light, and the polarization based beam director to a reflective element, where at least part of the reflected light is reflected and propagates back to the luminescent material element via the polarization based beam director first quarter wave plate, where again linear polarized light is converted into elliptical polarized light. After this recycling, at least part of the device light may be converted into further luminescent material light . In this way, the yield may be enhanced, and non-converted light in a first pass may at least partly be converted in a second pass.

[0021] Further, in this way, with the first device light, luminescent material light is provided. The luminescent material light may be substantially diffuse (e.g. Lambertian-type beam profile). Escape from luminescent material light from the system (via the light exit) may thus be essentially safe. With the current system, the at least one recycle reduces the available first device light that may escape from the system (unless a bypass-embodiment is applied, see also below). The first device light that might in principle escape from the system (via the light exit) may either be blocked (e.g. via the dichroic filter) or may also be diffused, e.g. via a polarization maintaining diffuser downstream of a first device light partially transmissive luminescent material element, before it may also escape from the system (via the light exit).

[0022] Further embodiments and aspects will be described below.

[0023] The light generating device may be configured to generate device light. Therefore, in embodiments, the light generating device may comprise a solid-state light source. In embodiments, the light generating system may comprise (at least) a first light generating device. The first light generating device may, in embodiments, be configured to generate first device light. Therefore, in embodiments, the first light generating device may comprise a first light source. The first light source may be essentially any light source, see also further below. Especially, in embodiments, the (first light source of the) first light 2024PF80183

[0024] 6 generating device may comprise a first solid state light source. Hence, in embodiments, the first light generating device may comprise one or more of a laser diode, a superluminescent diode, and a stacked multi -junction light-emitting diode (LED). In specific embodiments, the first light generating device may comprise at least two first solid-state light sources, such as e.g. two lasers. The first light generating device may herein also comprise a plurality of first (solid state) light sources. Especially, in specific embodiments, the first light generating device may comprise a first laser bank. In such embodiments, the first laser bank may comprise (a light emitting arrangement comprising) a first array comprising a plurality of first solid state light sources. Especially, in embodiments, the first laser bank may comprise a first array comprising a plurality of first lasers. For example, in embodiments, the first array may comprise a 2D array, such as an n*m array. In such embodiments, n and m may be individually selected from the range of 1-28, such as from the range of 2-20, like from the range of 4-14. A laser bank may comprise a relatively dense assembly of multiple laser diodes on a shared substrate provided with collimating optics, such as collimating lenses comprising one lens per laser diode (e.g. arranged in an array of lenses, see also further below). The use of laser banks may especially be convenient for projecting a beam of high- power laser light onto a luminescent converter without the need for using an inverse beam expander. Depending on the desired output beam characteristics, additional beam shaping optics may be needed. Hence, in embodiments, the first light generating device may comprise a first laser bank, wherein the first laser bank may comprise a light emitting arrangement comprising a 2D array of a plurality of first laser diodes arranged on a thermally conductive carrier and a lens array having a plurality of collimator lenses corresponding to the first laser diodes such that each laser diode of the plurality of first laser diodes may comprise a collimator lens for collimating laser light emitted by the laser diode.

[0025] Further, in embodiments, the first light generating device may especially be configured to generate first device light having a first centroid wavelength (Xci). In embodiments, the first centroid wavelength (Xci) may be essentially any wavelength. Especially, in embodiments, the first device light may have a first centroid wavelength (Xci) selected from the visible wavelength range. Hence, the first device light may have essentially any color. In specific embodiments, (at least part ol) the first device light may have a first centroid wavelength (Xci) selected from the wavelength range of 300-500 nm, such as from the range of 400-490 nm, for instance from the range of 420-490 nm, like from the range of 430-490 nm. More especially, in embodiments, (at least part ol) the first device light may have a first centroid wavelength (Xci) selected from the wavelength range of 440-490 nm, 2024PF80183

[0026] 7 such as from the wavelength range of 450-480 nm. Hence, in embodiments, the first device light may be blue light. 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). However, intensity at shorter wavelengths may also be possible, such as within the wavelength range of 400-440 nm. Especially, in embodiments the device light has a centroid wavelength selected from the blue wavelength range. However, in alternative embodiments, the first device light may have a first centroid wavelength (Xci) selected from for example the yellow or red wavelength range, see also further below. Hence, in embodiments, the first device light may comprise essentially any color, and may even be white light, see also further below.

[0027] The term “centroid wavelength”, also indicated as Xc, is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula Xc = X X*I(X) / (X I( X)), where the summation is over the wavelength range of interest, and I(X) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions,

[0028] Hence, in embodiments the first light generating device may be configured to generate first device light, wherein the first light generating device may comprise a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multi -junction light-emitting diodes.

[0029] In embodiments, the first device light may be polarized light or a polarization may be imposed to the first device light, e.g. with a polarizer. Hence, the first device light reaching the first polarizing beam splitter may comprise polarized light. In specific embodiments, the laser light may comprise linear polarized light. Linear polarized light (or “linearly polarized light”) may herein refer to light having (electric field) oscillations predominantly aligned in a single plane. Hence, it is not excluded that some oscillations occur outside of the single plane, such as in a plane perpendicular thereto. For instance, in embodiments, the linear polarized light may have at least 80% of (electric field) oscillations in a single plane, such as at least 90%, especially at least 95%, such as at least 99%, including 100%. In embodiments where the laser light comprises some (e.g. at most 10%, such as at most 5%, like at most 1%) oscillations occurring outside the single plane, the laser light may be partially polarized light comprising linear polarized light. 2024PF80183

[0030] 8

[0031] The linearly polarized light may, in embodiments, also comprise elliptically polarized light with a large ratio of perpendicular polarization components, such as a ratio > 4, especially > 6, such as > 10, especially > 20. As known in the art, linear polarized light may be generated by optical elements of solid state lasers, e.g., desired filters, laser cavity dimensional and / or structural characteristics, and / or intracavity elements. The linear polarizations s-polarized and p-polarized may be considered complementary polarizations (or orthogonal polarizations).

[0032] As indicated above, the luminescent material element may be configured in a light receiving relationship with the first light generating device. Hence, the luminescent material element may be configured downstream from the first light generating device. The terms “upstream” and “downstream”, such as in the context of propagation of light, may especially relate to an arrangement of items or features relative to the propagation of the light from a light generating element (here the especially the ....), wherein relative to a first position within a beam of light from the light generating element, a second position in the beam of light closer to the light generating element (than the first position) is “upstream”, and a third position within the beam of light further away from the light generating element (than the first position) is “downstream”. Instead of the term “light generating element” also the term “light generating means” may be applied.

[0033] The terms "radiationally coupled" or “optically coupled” or “radiatively coupled” may especially mean that (i) a light generating element, such as a light source, and (ii) another item or material, are associated with each other so that at least part of the radiation emitted by the light generating element is received by the item or material. In other words, the item or material is configured in a light-receiving relationship with the light generating element. At least part of the radiation of the light generating element will be received by the item or material. This may in embodiments be directly, such as the item or material in physical contact with the (light emitting surface of the) light generating element. This may in embodiments be via a medium, like air, a gas, or a liquid or solid light guiding material. In embodiments, also one or more optics, like a lens, a reflector, an optical filter, may be configured in the optical path between light generating element and item or material. The term “in a light-receiving relationship” does, as indicated above, not exclude the presence of intermediate optical elements, such as lenses, collimators, reflectors, dichroic mirrors, etc. In embodiments, the term “light-receiving relationship” and “downstream” may essentially be synonyms. 2024PF80183

[0034] 9

[0035] The luminescent element may comprise a luminescent material. Hence, the luminescent element may especially be configured to convert part of the first device light received by the luminescent material element into luminescent material light.

[0036] The term “luminescent material” especially refers to a material that can convert first radiati on, (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. Further, instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art. 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.

[0037] 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 (Xex>Xem).

[0038] The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. When different luminescent materials are applied, one or more luminescent materials may be configured to convert incident light into one or more of green and yellow luminescent material light, and one or more other luminescent materials may be configured to convert incident light into one or more of orange and red luminescent material light. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. The term “luminescent material” herein may also refer to a material comprising a luminescent material, such as a light transmissive host comprising the luminescent material. 2024PF80183

[0039] 10

[0040] 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.

[0041] Especially, the luminescent material is configured to convert at least part of the light source light into luminescent material light, wherein the luminescent material may comprise a (garnet) luminescent material of the type A^BsOn 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. Hence, the luminescent material light may e.g. be green light or yellow light (or in specific embodiments even orange (dependent upon the composition of the garnet and cerium concentration)). However, other embodiments are also possible, see below. In embodiments, 0.05-10% of the A elements comprise Ce, even more especially 0.05-5%, such as 0.1-5%. Especially, embodiments, 0.1-3% of the A elements comprise Ce, such as up to 2%, like selected from the range of 0.1-1.5%, such as at least above 0.5%.

[0042] The luminescent material may comprise an organic group that converts the light, or a molecule that converts the light, or an inorganic group that converts the light, etc. Such groups (or molecule) may be indicated as converter element. The garnet type material as indicated above, comprises cerium (Ce) as converter element. Cerium comprising garnets are well known in the art.

[0043] Hence, in specific embodiments the luminescent material comprises a luminescent material of the type A^BsOn 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 comprises aluminum (Al), however, B may also partly comprise gallium (Ga) and / or scandium (Sc) and / or indium (In), especially up to about 20% of Al, more especially up to about 10 % of Al (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, 2024PF80183

[0044] 11

[0045] 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)3BsOi2: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 ofY 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.

[0046] In specific embodiments the luminescent material comprises (Yxi-x2- x3A’x2Cex3)3(Alyi-y2B’y2)5Oi2, wherein xl+x2+x3=l, wherein x3>0, wherein 0<x2+x3<0.2, wherein yl+y 2=1, wherein 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.

[0047] 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-x2- x3(Lu,Gd)x2Cex3)3(Alyi-y2Gay2)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 2024PF80183

[0048] 12 further specific embodiments, the luminescent material comprises (Yxi-x3Cex3)3A150i2, wherein xl+x3=l, and wherein 0<x3<0.2, such as 0.001-0.1.

[0049] Alternatively or additionally, the luminescent material may comprise a luminescent material of the type AsSieNi i:Ce3. wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y.

[0050] In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu2+and / or I LSisNs Eu2and / or MAISiNsvEu2and / 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 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 CaAlSiN3: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.

[0051] In embodiments, the luminescent material may comprise a luminescent material of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine. A luminescent material of the type M’xM2-2xAX6 doped with tetravalent manganese is amongst others described in WO2013121355A1, which is herein incorporated by reference. Passages from WO2013121355A1 are also copied herein. Herein, M’xM2-2xAX6 doped with tetravalent manganese, may further also shortly be indicated as “phosphor”, i.e. the phrase " phosphor comprising M’xM2-2xAX6 doped with tetravalent manganese" may in an embodiment also be read as M’xM2-2xAXe doped with tetraval ent manganese phosphor, or (tetraval ent) Mn-doped M’XM2-2XAX6 phosphor, or shortly "phosphor".

[0052] Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Optionally, also lithium and / or cesium may be applied. In a preferred embodiment, M comprises at least potassium. In yet another embodiment, M comprises at least rubidium. The phrase “wherein M comprises at least potassium” indicates for instance that of all M cations 2024PF80183

[0053] 13 in a mole M’xM2-2xAX6 , a fraction comprises K+and an optionally remaining fraction comprises one or more other monovalent (alkaline) cations (see also below). In another preferred embodiment, M comprises at least potassium and rubidium. Optionally, the M’xNfc- 2xAXe luminescent material has the hexagonal phase. In yet another embodiment, the M’xNfc- 2xAXe luminescent material has the cubic phase. Relevant alkaline earth cations (M’) are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba. In an embodiment, a combination of different alkaline cations may be applied. In yet another embodiment, a combination of different alkaline earth cations may be applied. In yet another embodiment, a combination of one or more alkaline cations and one or more alkaline earth cations may be applied. For instance, KRbo.5Sro.25AX6 might be applied. As indicated above, x may be in the range of 0-1, especially x<l. In an embodiment, x=0.

[0054] The term “tetravalent manganese” refers to Mn4+. This is a well-known luminescent ion. In the formula as indicated above, part of the tetravalent cation A (such as Si) is being replaced by manganese. Hence, M’xM2-2xAXe doped with tetravalent manganese may also be indicated as M’xM2-2xAi-mMnmX6. The mole percentage of manganese, i.e. the percentage it replaces the tetraval ent cation A will in general be in the range of 0.1-15 %, especially 1-12 %, i.e. m is in the range of 0.001-0.15, especially in the range of 0.01-0.12.

[0055] In an embodiment, M’xM2-2xAX6 comprises K2SiFe (indicated herein also as KSiF system). As indicated above, in another preferred embodiment, M’xM2-2xAX6 comprises KRbSiFe (herein also indicated as K,Rb system). As indicated above, part of silicon is replaced by manganese (i.e. the formula may also be described as K2Sii-mMnmF6 or KRbSii-mMnmFe, with m as indicated above, or as KRbSiFe:Mn and K2SiFe:Mn, respectively). As manganese replaces part of a host lattice ion and has a specific function, it is also indicated as “dopant” or “activator”. Hence, the hexafluorosilicate is doped or activated with manganese (Mn4+). In specific embodiments, the luminescent material may comprise (K,Rb)2SiF6:Mn4+. Alternatively or additionally, in embodiments the third luminescent material may comprise K2SiFe:Mn4+. Alternatively or additionally, in embodiments the third luminescent material may comprise K2TiFe:Mn4+. In embodiments, the third luminescent material may comprise K2(Si,Ti)Fe:Mn4+. As can be derived from the above, “Si,Ti” may indicate one or more of Si and Ti.

[0056] Hence, when M refers to n different elements, this may imply that the relevant formula may comprise for the M position in the formula essentially any permutation of the n different elements. For instance, when M=Ba,Sr,Ca or when M comprises one or more of Ba,Sr,Ca or when M refers to Ba,Sr,Ca, this may imply that in the formula Ba, Sr, Ca, 2024PF80183

[0057] 14

[0058] (BaxSry), (BaxCay), (CaxSry), or (BaxSryCaz), may be available, wherein in general x+y+z=l. Referring to e.g. M’xM2-2xAX6, this may refer to e.g. one or more of K2SiFe:Mn4+and of Rb2SiFe:Mn4+, or (KxRby)2SiF6:Mn4+, etc. Further, indications like “K,Rb” or Ba,Sr,Ca, and similar indications (see also above), may indicate one or more of such elements. Hence, (K,Rb)2SiFe:Mn4+, may e.g. refer to K2SiFe:Mn4+and of Rb2SiFe:Mn4+, or (KxRby)2SiF6:Mn4+. Also herein in general x+y=l. Hence, when M may refer to n different elements, with n being at least two, 2n-l permutations may in principle be possible.

[0059] Especially, the luminescent material may be an inorganic luminescent material, such as one or more of the above-described trivalent cerium or divalent europium comprising oxides, oxynitrides, or nitrides.

[0060] 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.

[0061] The term “luminescent material” herein especially relates to inorganic luminescent materials.

[0062] 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 (CuInS2) and / or silver indium sulfide (AgInS2) can also be used. 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 nano-wires, etcetera.

[0063] As indicated above, the luminescent element may especially be configured to convert part of the first device light received by the luminescent material element into luminescent material light.

[0064] Further, the light generating system is configured such that at least part of the (generated) luminescent material light propagates along an optical path via the dichroic filter to the light exit. To this end, the light generating system may comprise optics or optical 2024PF80183

[0065] 15 elements. The optics may include the afore-mentioned first quarter wave plate, a polarization based beam director, a dichroic filter, but may also (additionally) comprise reflectors, lenses, etc.

[0066] 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 of mirrors, reflectors, collimators, lenses, prisms, diffusers, phase plates, polarizers, diffractive elements, gratings, dichroics, arrays of one or more of the aforementioned, 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”).

[0067] Especially, in embodiments, the optical elements further comprise one or more optical integrators. In embodiments, the optical integrators may be individually selected from the group comprising: a small-angle diffuser, a transmissive volume diffuser, a transmissive surface diffuser, a transmissive or reflective diffractive optical element, a transmissive holographic optical element, a single multi lens array, a double multi lens array such as a flyeye lens array, and an integrating polygonal light pipe.

[0068] At least one optical integrator may, in embodiments, be configured in an optical path between the first light generating device and the luminescent material.

[0069] Yet further, in embodiments, the optical elements may comprise an optical integrator configured between the luminescent material and the light exit.

[0070] Hence, in specific embodiments, the optical elements may further comprise one or more optical integrators, wherein the optical integrators may be individually selected from the group comprising: a small-angle diffuser, a transmissive volume diffuser, a transmissive surface diffuser, a transmissive or reflective diffractive optical element, a transmissive holographic optical element, a single multi lens array, a double multi lens array such as a fly-eye lens array, and an integrating polygonal light pipe; and wherein at least one optical integrator may be configured in an optical path between the first light generating device and the luminescent material. Such embodiments may be beneficial as the optical integrators may improve spot sizes and light distributions in spots of light on the different elements such as e.g. the diffuser and the luminescent material. Therewith, the lifetime of these elements may be improved. Furthermore, the optical integrators may help homogenize 2024PF80183

[0071] 16 the light propagating through the light generating system, which may provide the advantage of more homogeneously distributed system light.

[0072] Furthermore, in embodiments, the optical elements may comprise one or more of condensing (or focusing) optical elements and collecting (or collimating)) optical elements. In embodiments, at least one condensing and / or collimating optical element may be configured upstream of the (reflective) diffuser. Similarly, in embodiments, at least one condensing and / or collimating optical element may be configured upstream of the luminescent material. Further, in embodiments, at least one condensing and / or collimating optical element may be configured upstream of the light exit. Yet further, in embodiments, at least one condensing and / or collimating optical element may be configured downstream of the first (and optionally second) light generating device.

[0073] In embodiments, a condensing optical element may be configured to condense or focus the light received by the condensing optical element. The condensing optical element may thus, in embodiments, be configured to provide a focused beam of device light in an optical path to a downstream part of the light generating system (e.g. the luminescent material or the light exit). Conversely, in embodiments, the collecting optical element may be configured to collect and collimate the light received by the collecting optical element. The collecting optical element may thus, in embodiments, be configured to provide a collimated beam of light in an optical path to a downstream part of the light generating system (e.g. the luminescent material or the light exit). Therefore, in embodiments, the condensing optical element and the collimating optical element may both be configured transmissive for ((diffused) device and / or luminescent material) light.

[0074] In embodiments, a condensing and / or collecting optical element may comprise a lens. Especially, in embodiments, a condensing and / or collecting optical element may comprise a surface configured to condense and / or collimate an incoming parallel beam of light, such as a lens surface. In such embodiments, the condensing and collecting (or collimating) optical elements may comprise one or more positive lenses. In some embodiments, it may be preferred to apply a set of two, or possibly three positive condenser lenses to enable a large effective numerical aperture.

[0075] In embodiments, a condensing and / or collecting optical element may for example comprise one or a curved lens surface, a Fresnel-type lens surface, and a metasurface (i.e., a flat textured surface). Especially, in embodiments, a condenser and / or collecting optical element may comprise an aspherical lens. However, in alternative 2024PF80183

[0076] 17 embodiments (in dependence on desired requirements for the out-put system light), a condensing and / or collecting optical element may also comprise a spherical lens.

[0077] Furthermore, in embodiments, a condensing and / or collecting optical element may comprise a material having low absorption for (at least) the spectral range of the device light. For transmission efficiency as well as survival of the lenses, the induced stresses due to absorption of light may need to be limited. For this, in embodiments, a very low absorption glass with e.g. an internal transmission of at least 99.7% through 10 mm material may be applied. Hence, in embodiments, suitable glass materials may be selected from the group comprising: N-BK7, N-BK7HT, H-K9L, or H-K9LGT. Especially, in embodiments, the condensing and / or collecting optical elements may comprise fused silica (FS). Moreover, in embodiments, each condensing and / or collecting optical element may comprise a material having an absorption coefficient individually selected from the range of <0.01 cm'1for the spectral range of the received device light. More especially, in embodiments, each condenser and / or collecting optical element may comprise a material having an absorption coefficient individually selected from the range of <0.005 cm'1, such as from the range of <0.01 cm'1, for the spectral range of the received device light.

[0078] Note that, in embodiments, a condensing optical element and a collecting optical element may comprise essentially the same type of optical element. For example, in embodiments, a single positive lens may be applied for condensing (first) device light onto the diffuser, while that same lens may be applied for collimating diffused device light propagating from the diffuser. However, this may not necessarily be the case.

[0079] In embodiments, the system may comprise a light exit, like an end window or an (other) optical element, like a lens, or an opening, from which the system light may escape to the external of the system. The system may comprise a housing, comprising such light exit. The housing may at least partly enclose one or more light generating devices and one or more (other) optical elements.

[0080] As indicated above, a birefringent, such as (first) quarter wave plate may be applied. A birefringent rotator, more especially a / 4 waveplate (or quarter waveplate). Especially, in embodiments, the (diffuser assembly may comprise a) quarter waveplate configured in an optical path between the first light generating device and the luminescent material element.

[0081] As known from the art, a waveplate or retarder is an optical device that alters the polarization state of a light wave travelling through it. A halfwave plate may shift the polarization direction of linear polarized light (especially from s to p or from p to s- 2024PF80183

[0082] 18 polarization). Conversely, a quarter-wave plate may convert linear polarized light into elliptically (such as especially circularly) polarized light (and vice versa).

[0083] Especially, herein, in embodiments, the quarter waveplate may be configured to convert linear polarized (first) device light received by the quarter waveplate into elliptical (such as especially circularly) polarized (first) device light. Additionally or alternatively, in embodiments, the quarter waveplate may be configured to convert elliptical polarized (diffused) device light (such as especially circularly) received by the quarter waveplate into linear polarized light. Note that for other embodiments, such as with an additional light generating device, a second quarter waveplate may be applied (for which the same basic principles may apply); see further also below.

[0084] Especially, the first quarter wave plate and the polarization based beam director are configured in an optical path between the first light generating device and the luminescent material element. Further, relative to a propagation of the first device light from the first light generating device to the luminescent material element, the first quarter wave plate is configured downstream of the polarization based beam director.

[0085] Herein, the polarization based beam director and the dichroic filter may be indicated as redirection optical elements. Such polarization based beam director and the dichroic filter may e.g. be applied to direct light of a specific linear polarization and / or a specific color in one direction and to direct light of another specific linear polarization and / or another specific color in another direction. However, they may also be applied to combine light having different linear polarizations and / or having different spectral power distributions. The polarization based beam director may also be indicated as first redirection optical element. Further, the polarization based beam director may (thus) also be indicated as- polarization based beam redirection optical element, and the dichroic filter may also be indicated as dichroic based beam redirection optical element.

[0086] The phrase “to direct light”, and similar phrases, in relation to (redirection) optical elements, may (a) refer to redirecting light, whereby there may be a non-zero angle (e.g. an angle of 80-100°, such as an angle of 90°) between the optical axis of the light propagating to the (redirection) optical element and the optical axis of the light emanating from the (redirection) optical element, but may (b) also refer to allowing light to pass (i.e., transmitting light), whereby there may be an angle of < 10°, such as a zero angle (i.e. parallel) between the optical axis of the light propagating to the (redirection) optical element and the optical axis of the light emanating from the (redirection) optical element. For instance, a (redirection) optical element may direct light, received by the (redirection) optical 2024PF80183

[0087] 19 element to another optical element, whereby the redirection optical element receives light along two orthogonal (optical) paths, wherein the light from both paths may be of different types (e.g. of different polarizations, spectral power distributions, etc.), wherein one of the types of light (from one of the (optical) paths) is reflected by the (redirection) optical element to the other optical element (i.e. non-zero angle), and another one of the types of light (from the other (optical) path) is transmitted by the (redirection) optical element to the other optical element (i.e. zero angle) (and thus both are directed to that optical element). Therefore, a (redirection) optical element such as a reflector, a dichroic mirror, a polarizing beam splitter, and a lens, etc. may direct light received by such (redirection) optical element.

[0088] In embodiments, the optical elements may thus be configured to (help) propagate the different types of light through the light generating system. Especially, in embodiments, the polarization based beam director (or first redirection optical element) may be configured to direct the first device light in an optical path to the luminescent material element.

[0089] In embodiments, the (first) device light received by the first redirection optical element may especially be polarized light. Hence, in embodiments, the light generating system may be configured such that (both) the first device light and( / or) the diffused device received by the first redirection optical element may comprise polarized light (see also below).

[0090] The phrase “... light received by...”, and similar phrases, such as “device light received by the first redirection optical element” may especially indicate that when the light is actually received by an item, an action may take place. The action may in embodiments be one or more of conversion, reflection, and transmission. Further, the action may also include refraction. Whether or not such item receives light may e.g. depend on e.g. a controlling mode (for instance whether or not a light generating device provides light).

[0091] In embodiments, the second linear polarization may especially be different from the first linear polarization. Especially, in embodiments, the second linear polarization may be (about) 90° rotated relative to the first linear polarization. More especially, in some embodiments the first linear polarization may be p-polarization and the second linear polarization may be s-polarization. In other embodiments, the first polarization may be s- polarization and the second polarization may be p-polarization. Herein, the terms “p- polarization” and “s-polarization” may especially refer to the polarization of light when incident on (a light-receiving plane ol) the light-receiving element, such as e.g. the first polarization based redirection optics (especially the first polarizing beam splitter). 2024PF80183

[0092] 20

[0093] Hence, in embodiments the first device light and the diffused device light reaching the first (polarization based, see also further below,) redirection optical element may have essentially complementary polarizations. Hence, in embodiments the first device light reaching the first redirection optical element may essentially be p-polarized light and the diffused device light reaching the first redirection optical element may comprise or (essentially) be s-polarized light, or the first device light reaching the first redirection optical element may essentially be s-polarized light and the diffused device light reaching the first redirection optical element may comprise or (essentially) be p-polarized light. Therefore, the first redirection optical element may be polarization based. Hence, e.g. a beam of elliptically polarized light may be split into two (orthogonal) beams of s-polarized light and p-polarized light. For instance, one of the polarizations may be transmitted, and one of the polarizations may be reflected. This may also imply that a beam of light that consists of essentially linear polarized light may be (at least partly) reflected or (at least partly) transmitted at the polarization based redirection optics. Hence, the redirection optics may comprise a polarizing beam splitter. In other words, the first redirection optical element may also be referred to as a first polarizing beam splitter. Such optics, however, may also be used to combine a beam of light. Especially, e.g. a beam of s-polarized light and a beam of p-polarized light may be combined into a beam of light comprising both polarizations, i.e. light that can generally be described as elliptically polarized light (note that this may include the extremes of circular polarized light as well as linear polarized light). For instance, one of the beams may be transmitted, and one of the beams may be reflected. The combined beam may propagate in the same direction as one of the transmitted beam and reflected beam. Hence, the redirection optics may comprise a polarizing beam combiner. Such optics, however, may thus also be used to split beams of light. Hence, the herein described polarization based redirection optics are herein also indicated as-polarization beam combiners, or polarizing beam combiners, or polarization beam splitters, or polarizing beam splitters, and are shortly indicated as “PBS”.

[0094] In embodiments, in operation at least part of the first device light may propagate via the polarization based beam director (and the first quarter wave plate) to the luminescent material element.

[0095] In a first series of specific embodiments, first device light having a first linear polarization may be reflected at the polarization based beam director and reach via the first quarter wave plate the luminescent material element, which may be at least partially transmissive for first device light. Downstream of the (first device light transmissive) luminescent material element, a first reflector (for first device light), such as a metallic 2024PF80183

[0096] 21 reflector or a polarization maintaining diffuser, may be configured. Device light reflected at the first reflector may propagate through the luminescent material element (and partly also be configured into luminescent material light) via the via the first quarter wave plate to the polarization based beam director and be transmitted by the polarization based beam director (as the linear polarization may be different from the first device light from the first light generating device that is received by the polarization based beam director (see also above)). The reflected device light may (thus) at least partly be diffused. The reflected device light transmitted by the polarization based beam director may propagate to the dichroic filter or to a second reflector (for first device light), such as a metallic reflector or a polarization maintaining diffuser (see further below). The dichroic filter (or the second reflector) may reflect the (reflected) first device light back to the polarization based beam director, which directs (via transmission) it again to the luminescent material element, where it may arrive, via the quarter wave plate, and be at least partly converted (into further luminescent material light). In such embodiments, the polarization based beam director may especially be transmissive for luminescent material light (and further luminescent material light) in embodiments wherein the luminescent material light propagates to the light exit via the polarization based beam director. Would the dichroic filter be configured in the optical path between the polarization based beam director and the luminescent material element, then the dichroic filter may be reflective for luminescent material light and transmissive for first device light. Would however the dichroic filter be configured in an optical path between the polarization based beam director and the light exit, then especially the dichroic filter may be reflective for first device light and transmissive for luminescent material light. Note that variations on these embodiments may also be possible.

[0097] In a second series of specific embodiments, first device light having a first linear polarization may be transmitted via the polarization based beam director and reach via the first quarter wave plate the luminescent material element, which may be at least partially transmissive for first device light. Downstream of the (first device light transmissive) luminescent material element, a first reflector (for first device light), such as a metallic reflector (or a polarization maintaining diffuser (see further below), may be configured. Device light reflected at the first reflector may propagate through the luminescent material element (and partly also be configured into luminescent material light) via the via the first quarter wave plate to the polarization based beam director and be reflected by the polarization based beam director (as the linear polarization may different from the first device light from the first light generating device that is received by the polarization based 2024PF80183

[0098] 22 beam director (see also above) to a second reflector (for first device light), such as a metallic reflector or a polarization maintaining diffuser. The reflected device light may (thus) at least partly be diffused. The second reflector may reflect the (reflected) first device light back to the polarization based beam director, which directs (via reflection) it again to the luminescent material element, where it may arrive, via the quarter wave plate, and be at least partly converted (into further luminescent material light). In such embodiments, the polarization based beam director may especially be transmissive for luminescent material light (and further luminescent material light) in embodiments wherein the luminescent material light propagates to the light exit via the polarization based beam director. Would the dichroic filter be configured in the optical path between the polarization based beam director and the luminescent material element, then the dichroic filter may be reflective for luminescent material light and transmissive for first device light. Would however the dichroic filter be configured in an optical path between the polarization based beam director and the light exit, then especially the dichroic filter may be reflective for first device light and transmissive for luminescent material light.

[0099] In a third series of specific embodiments first device light having a first linear polarization may be transmitted via the polarization based beam director to a second reflector (for first device light), such as a metallic reflector or a polarization maintaining diffuser, especially a second reflector (for first device light), such as a metallic reflector or a polarization maintaining diffuser. In the optical path between the polarization based beam director and the polarization maintaining diffuser a second quarter wave plate may be configured. First device light may be diffused at the polarization maintaining diffuser, and the arrangement of the polarization maintaining diffuser and the second quarter wave plate may imply that first device light having a first linear polarization propagating tot the arrangement of the polarization maintaining diffuser and the second quarter wave plate of may be converted into diffused first device light having a second linear polarization. The diffused first device light having a second linear polarization is reflected at the polarization maintaining diffuser and directed to the luminescent material element and may reach, via the first quarter wave plate, the luminescent material element, which may be at least partially transmissive for first device light. Downstream of the (first device light transmissive) luminescent material element, a first reflector (for first device light), such as a metallic reflector (or a polarization maintaining diffuser (see further below), may be configured. Device light reflected at the first reflector may propagate through the luminescent material element (and partly also be configured into luminescent material light) via the via the first 2024PF80183

[0100] 23 quarter wave plate, to the polarization based beam director. As the linear polarization of the reflected device light has changed again in the (sub)cycle of polarization based beam director - first quarter wave plate - first reflector - first quarter wave plate, the reflected device light may now be transmitted by the polarization based beam director. In embodiments, however, a dichroic filter may be configured in the optical path between the polarization based beam director and the light exit, which dichroic filter may be configured to reflect device light. The dichroic filter may be reflective for first device light and transmissive for luminescent material light. This device light, reflected at the dichroic filter, may propagate (back) in the direction of the luminescent material element. Hence, device light that is not absorbed by the luminescent material may have one or more further chances to be absorbed and converted into luminescent material light by this recycle configuration. Hence, these third series of specific embodiments may allow a relatively efficient conversion of device light. This may also allow thinner luminescent material elements, and thus better thermal management.

[0101] The first series of specific embodiments, second series of specific embodiments, and third series of specific embodiments may be based on the use of a light transmissive, especially light transparent, luminescent material element, which may absorb part of the first device light and convert into luminescent material light, but which may also transmit part of the first device light. Further, behind the luminescent material element, a first reflector may be configured. Hence, the luminescent material element may have a relative low scattering for the first device light.

[0102] The luminescent material element may comprise a luminescent body. Hence, especially, the luminescent material is comprised by a luminescent body. The luminescent body may be a layer, like a self-supporting layer. The luminescent body may also be a coating. The luminescent body may also comprise a luminescent coating on a support (especially a light transmissive support in the transmissive mode, or a reflective support in the reflective mode). Especially, the luminescent body may essentially be self-supporting. In embodiments, the luminescent material may be provided as luminescent body, such as a luminescent single crystal, a luminescent glass, or a luminescent ceramic body. Such body may be indicated as “converter body” or “luminescent body”. In embodiments, the luminescent body may be a luminescent single crystal or a luminescent ceramic body. For instance, in embodiments a cerium comprising garnet luminescent material may be provided as a luminescent single crystal or as a luminescent ceramic body. In other embodiments, the luminescent body may comprise a light transmissive body, wherein the luminescent material is embedded. For instance, the luminescent body may comprise a glass body, with 2024PF80183

[0103] 24 luminescent material embedded therein. Or, the glass as such may be luminescent. In other embodiments, the luminescent body may comprise a polymeric body, with luminescent material embedded therein.

[0104] The luminescent body may have any shape. In general, however, the luminescent body may comprise two essentially parallel faces, defining a height (of the luminescent body). Further, the luminescent body may comprise an edge face, bridging the two essentially parallel faces. The edge face may be curved in one or two dimensions. The edge face may be planar. The luminescent body may have a rectangular or circular crosssection, though other cross-sections may also be possible, like e.g. hexagonal, octagonal, etc. Hence, the luminescent body may have a circular cross-section, an oval cross-section, square, or non-square rectangular. In embodiments, the luminescent body may have an n-gonal crosssection, wherein n is at least 3, like 4 (square or rectangular cross-section), 5 (pentagonal cross-section), 6 (hexagonal cross-section), 8 (octagonal cross-section) or higher. The two essentially parallel faces may also be indicated as “main faces”, as they may especially provide the largest external area of the luminescent body. Perpendicular to the aforementioned cross-section, may be another cross-section, which may in embodiments be rectangular. Hence, the luminescent body may e.g. have a cubic shape, a (non-cubic) cuboid shape, an n-gonal prism shape with n being at least 5 (such as pentagonal prism, hexagonal prism), and a cylindrical shape. Other shapes, however, may also be possible. Especially, the luminescent body may have a cuboid shape, a cylindrical shape, or an n-gonal prism shape wherein n is 6 or 8.

[0105] In embodiments, the luminescent body (or “body”) has lateral dimensions width or length (W1 or LI) or diameter (D) and a thickness or height (Hl). In embodiments, (i) D>H1 or (ii) and W1>H1 and / or L1>H1. The luminescent body may be transparent or light scattering. In embodiments, the luminescent body may comprise a ceramic luminescent material. In specific embodiments, Ll<10 mm, such as especially Ll<5mm, more especially Ll<3mm, most especially Ll<2 mm. In specific embodiments, Wl<10 mm, such as especially Wl<5mm, more especially Wl<3mm, most especially Wl<2 mm. In specific embodiments, Hl<10 mm, such as especially Hl<5mm, more especially Hl<3mm, most especially Hl<2 mm. In specific embodiments, D<10 mm, such as especially D<5mm, more especially D<3mm, most especially D<2 mm. In specific embodiments, the body may have in embodiments a thickness in the range 50 pm - 1 mm. Further, the body may have lateral dimensions (width / diameter) in the range 100 pm - 10 mm. In yet further specific embodiments, (i) D>H1 or (ii) W1>H1 and L1>H1. Especially, the lateral dimensions like 2024PF80183

[0106] 25 length, width, and diameter are at least 2 times, like at least 5 times, larger than the height. In specific embodiments, the luminescent body has a first length LI, a first height Hl, and a first width Wl, wherein Hl<0.5*Ll and Hl<0.5*WL In embodiments, the luminescent body may be a (small) tile.

[0107] In embodiments, the luminescent body may comprises a first face, a second face, and a side face bridging the first face and the second face. The first face and the second face may also be indicated as main faces. In the case of a cylindrical shape, the side face may be a single side face. In the case of a cuboid, the side face may comprise four facets. In the case of a hexagonal prism the side face may comprise six facets.

[0108] In specific embodiments, the luminescent material element, may have a scatter length of at least the length (or thickness) of the luminescent material element, such as at least twice the length of the light transmissive element. The scatter length may be defined as the length along a propagation direction along which light is lost due to scattering and drops thereby with a factor 1 / e. Here, the length may thus especially refer to the distance between a primary face and a secondary face of the luminescent material element.

[0109] Hence, note that light transmissive may thus herein in embodiments refer to a luminescent material element that transmits part of the first device light and converts part of the first device light, but which may have a relatively low scattering for the first device light. Hence, in embodiments the luminescent material element comprises one or more of a ceramic body or a single crystalline body. Luminescent materials like tetravalent manganese comprising fluoride systems as described above and A3B5O12 type system may e.g. be available as ceramic bodies (or single crystals).

[0110] However, in a fourth series of embodiments, essentially the same configuration is applied in is in the first series of embodiments, except that the luminescent material element may is not necessarily light transmissive for the first device light, and is at least scattering for the first device light. Hence, a scattering luminescent material element may be applied, like e.g. a poly crystalline luminescent material layer. With scattering, the reflected device light may become less-polarized or unpolarized. However, still reflected device light may be reflected back via the first quarter waveplate and reach the polarization based beam director. The reflected device light may comprise light having a first linear polarization and light having a second linear polarization. In dependence of the configuration of the which may allow to pass at least part of the polarization based beam director, part of the reflected device light may be reflected or transmitted. Hence, in the fourth series of embodiments also at least part of the reflected device light, reflected at the scattering 2024PF80183

[0111] 26 luminescent material element, may still be recycled as described above for the first series of embodiments.

[0112] Likewise, in a fifth series of embodiments, essentially the same configuration is applied in is in the second series of embodiments, except that the luminescent material element may is not necessarily light transmissive for the first device light, and is at least scattering for the first device light. See further also above at the fourth series of embodiments. Hence, also in the fifth series of embodiments at least part of the reflected device light, reflected at the scattering luminescent material element, may still be recycled as described above for the second series of embodiments.

[0113] Likewise, in a sixth series of embodiments, essentially the same configuration is applied in is in the third series of embodiments, except that the luminescent material element may is not necessarily light transmissive for the first device light, and is at least scattering for the first device light. See further also above at the fourth series of embodiments. Hence, in the sixth series of embodiments also at least part of the reflected device light, reflected at the scattering luminescent material element, may still be recycled as described above for the third series of embodiments.

[0114] It is noted that in the first series of specific embodiments, the second series of specific embodiments, and the third series of specific embodiments, also some of the device light may be scattered, as the light transmissive luminescent material element may still provide for some scattering, even though a high quality ceramic body or high quality single crystalline body is applied. Hence, for scattered first device light at the light transmissive luminescent material element, the same may apply as described in the fourth series of specific embodiments, the fifth series of specific embodiments, and the sixth series of specific embodiments.

[0115] Further, it is noted that in the first series of specific embodiments (and thus also in the fourth series of specific embodiments), and in the third series of specific embodiments (and thus also in the sixth series of specific embodiments) the dichroic filter may be configured perpendicular to an optical axis of propagation of the reflected first device and the luminescent material light, which may imply a co-linear reflection of the first device light at the dichroic filter (i.e. dichroic mirror, reflective for (reflected) first device light and transmissive for luminescent material light). However, in the second series of specific embodiments (and thus also in the fifth series of specific embodiments), the dichroic filter may be configured under an angle of 45° to an optical axis of propagation of the reflected first device and the luminescent material light. This may imply an orthogonal propagation of 2024PF80183

[0116] 27 the reflected first device and the luminescent material light, as one may be reflected (under an angle of 45°), and one may be transmitted by the dichroic filter. This may imply an angle of 90° of the optical axis of the reflected first device and the luminescent material light emanating from the dichroic filter.

[0117] For those (specific) embodiments (i.e. the second and fifth series of specific embodiments) wherein the dichroic filter may be configured under an angle of 45° to an optical axis of propagation of the reflected first device and the luminescent material light, the dichroic filter may in embodiments be configured external of the optical path between the polarization based beam directed and the luminescent material element, but may in other embodiments be configured in the optical path between the polarization based beam directed and the luminescent material element. In both embodiments, especially the dichroic filter may be reflective for luminescent material light and transmissive for (reflected) device light.

[0118] Note that the further luminescent material light may propagate via the same path as the luminescent material light and is based on the same luminescent material. Hence, the term “luminescent material light”, and similar terms, may refer to luminescent material light and further luminescent material light, unless it is explicitly refer to one of both.

[0119] As can be derived from the above, the polarization based beam director may be configured to reflect or transmit (at least) first device light, received by the polarization based beam director, in dependence of its linear polarization. Yet further, in embodiments the light generating system may be configured such that the first device light from the first light generating device reaching the polarization based beam director comprises linear polarized light.

[0120] Especially, in embodiments, the polarization based beam director (i.e. a polarizing beam splitter) may be configured to transmit (or reflect) at least 60%, such as at least 70%, like at least 80% of the light (comprising the first linear polarization) received by the first polarizing beam splitter. Especially, in embodiments, the polarization based beam director may be configured to transmit (or reflect) at least 90%, more especially at least 95%, including 100% of the light (comprising the first linear polarization) received by the polarization based beam director. Especially, in embodiments, the polarization based beam director may be configured to transmit first device light comprising the polarization based beam director. Alternatively, in embodiments, the polarization based beam director may be configured to reflect first device light comprising the first linear. Further, in such embodiments, the polarization based beam director may be configured to reflect (or transmit) light received by the polarization based beam director and (said (device) light) comprising a 2024PF80183

[0121] 28 second linear polarization. Especially, in embodiments, the polarization based beam director may be configured to reflect (or transmit) at least 60%, such as at least 70%, like at least 80% of the light (comprising the second linear polarization) received by the polarization based beam director. Especially, in embodiments, the polarization based beam director may be configured to reflect (or transmit) at least 90%, more especially at least 95%, including 100% of the light (comprising the second linear polarization) received by the polarization based beam director.

[0122] In embodiments, the polarization based beam director may be configured to (a) reflect at least 90% (first device) light having s-polarization, such as at least about 95%, like at least about 99%, and transmit at least 90% (first device) light having p-polarization, such as at least about 95%, like at least about 99%, or (b) reflect at least 90% (first device) light having p-polarization, such as at least about 95%, like at least about 99%, and transmit at least 90% (first device) light having s-polarization, such as at least about 95%, like at least about 99%. As indicated above, the polarization based beam director may be polarizing beam splitter (or polarizing beam combiner).

[0123] Percentage in relation to transmission and reflection may be based on energy (Watt).

[0124] In other embodiments, the polarization based beam director may be a partial polarizing beam splitter, i.e. (a) one polarization may be essentially transmitted, and another polarization may be partially transmitted and partially reflected or, (b) one polarization may be essentially reflected, and another polarization may be partially transmitted and partially reflected. This may be an embodiment when part of the first device light may be allowed to end up in the system light, via a dichroic filter that is also direct part of the first device light, received by the dichroic filter, to the light exit.

[0125] Further, in embodiments, the polarization based beam director may be configured to transmit at least 80%, such as at least about 85%, like in embodiment at least about 90% of the luminescent material light. Hence, in embodiments the polarization based beam director may discriminate between s-polarized first device light and p-polarized first device light, but may (essentially) be transmissive for luminescent material light, irrespective of its (linear) polarization. Hence, in embodiments the polarization based beam director may have DBS-functionality and PBS-functionality, and may in such embodiments be indicated as DBS-PBS. Such DBS-PBS may in embodiments be transmissive for luminescent material light, whereas for first device light it may at least partially be transmissive for first device light having a first linear polarization (one of s-polarization and p-polarization) and may at 2024PF80183

[0126] 29 least partially be reflective for first device light having a second linear polarization (the other one of s-polarization and p-polarization).

[0127] As indicated above, in embodiments, the second reflector may comprise a polarization maintaining diffuser. Especially, the second reflector may in embodiments comprise a (polarization maintaining) small-angle diffuse reflector. Further, in embodiments the first reflector may comprise a (polarization maintaining) small-angle diffuse reflector. Yet, in embodiments second polarization maintaining diffuser may in embodiments comprise a (polarization maintaining) small-angle diffuse reflector. Hence, in embodiments the polarization maintaining diffuser(s) may comprise small-angle diffuse reflector(s), with diffusion angle(s) of at maximum 10°.

[0128] With reference to a small-angle diffuse reflector, it is noted that they may have a diffusion angle of at maximum 10°. The small-angle diffuse reflector may comprise a textured metal surface (or metallized textured surface), a meta surface, a diffractive surface, a holographic (volume) diffuser, a stack of a multi-lens array with a specular mirror, a stack of a small-angle transmissive diffusive material (e.g. a volume diffuser, textured surface diffuser, meta surface diffuser, ... ) with a specular mirror, a retroreflector array with some beam broadening properties, such as a cat-eye spheres array, etc. (see also above). Hence, in embodiments a small-angle reflective diffuser may be realized by a stack of a small-angle transmissive diffuser and a specular mirror. In embodiments, the term “diffusion angle” may refer to the (relatively smooth) broadening of an incident beam of radiation that may be characterized by the full width at half maximum of the diffused radiant angular intensity distribution for an incident (non-diffused) pencil beam (i.e., an incident beam of radiation with a negligible angular extent (FWHM) compared to the FWHM of the diffused beam). In further embodiments, the small-angle diffuse reflector may have a diffusion angle of at minimum 1°, such as at least about 1.5° (the diffusion angle of a specular reflector may thus be 0°).

[0129] Further, as can be derived from the above, in embodiments one or more of the following may apply: (a) the light generating system comprises a first reflector, configured downstream of the luminescent material element, wherein part of the first device light, received by the luminescent material element, is transmitted by the luminescent material element, reflected at the first reflector, and transmitted (again) by the luminescent material element in an optical path to the polarization based beam director, thereby providing reflected first device light, and (b) part of the first device light is reflected by the luminescent material element in an optical path to the polarization based beam director, thereby providing reflected 2024PF80183

[0130] 30 first device light. Yet, as can be derived from the above, in embodiments the light generating system is (further) configured such that at least part of the reflected first device light, in an optical path (i) propagates away from the luminescent material element and (ii) also returns to the luminescent material element, wherein this optical path is (a) at least twice (forth and back) via the polarization based beam director, and (b) twice (forth and back) via the first quarter wave plate, whereby the luminescent material element converts at least part of the reflected first device light, received by the luminescent material element via this optical path, into further luminescent material light.

[0131] Hence, the light generating system may be configured to generate system light comprising in embodiments at least part of the luminescent material light and at least part of the further luminescent material light (escaped from the light generating system via the light exit). Optionally, the system light may also comprise diffused device light (see further also below).

[0132] Further embodiments are described below.

[0133] Especially, the first reflector may be reflective for first device light. Especially at least 90%, such as at least about 95%, like at least about 99% of first device light that perpendicularly irradiates the first reflector may be reflected. The first reflector may be a specular reflector or a dichroic reflector. In, embodiments, the first reflector may be a polarization maintaining diffuser, see also above. In, embodiments, the first reflector may be a polarization maintaining diffuser for first device light. Further, in embodiments the first reflector may be reflective for luminescent material light. Especially at least 90%, such as at least about 95%, like at least about 99% of luminescent material that perpendicularly irradiates the first reflector may be reflected.

[0134] In embodiments, the first reflector may be provided by a thermally conductive element, such as a thermally conductive element that is reflective for first device light (and luminescent material light. In embodiments, the thermally conductive element may be a heat sink (or a heat pipe), or other thermally conductive element.

[0135] A thermally conductive element 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 2024PF80183

[0136] 31 silicon carbide, beryllium oxide, a silicon carbide composite, aluminum silicon carbide, a copper tungsten alloy, a copper molybdenum carbide, carbon, diamond, and graphite. However, in embodiments also magnesium may be applied. 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.

[0137] In embodiments, the first light generating device may be configured to generate first device light having a first peak wavelength XPiselected from the wavelength range of 430-490 nm. Hence, in embodiments the first device light may be blue light. Yet, in embodiments the luminescent material element may be configured to convert part of the first device light received by the luminescent material element into luminescent material light (201,201’) having a centroid wavelength Xcselected from 500-680 nm. Hence, the luminescent material light may comprise one or more of green, yellow, orange, and red light. Especially, there may be difference between the first peak wavelength of the first device light and the centroid wavelength of the luminescent material light, which may facilitate separation of these two types of light by the dichroic filter. Especially, their spectral overlap may be relatively small, or even essentially zero. In embodiments, Xc- XPi> 10 nm, more especially Xc- XPi> 20 nm. Further, in specific embodiments Xc- XPi> 30 nm, more especially Xc- XPi> 40 nm, like Xc- XPi> 50 nm. Further, in embodiments Xc- XPi< 190 nm.

[0138] In embodiments, the first light generating device comprises a laser diode. This may allow generating a relatively high intensity system light. More especially, in embodiments the light generating system may comprise an arrangement of a plurality of first light generating devices. Yet more especially, in embodiments the light generating system may comprise a laser bank comprising a plurality of first light generating devices each comprising a laser diode. Therefore, in (other) embodiments the first light generating device may comprise a laser bank comprising a plurality of laser diodes (see also above).

[0139] In specific embodiments, wherein the light generating system comprises the first reflector (see also above), wherein the first reflector may be a metallic reflector. Further, in (such) embodiments, the luminescent material element may be configured to transmit at least 10% (and at maximum 95%, such as at maximum 90%) of the first device light (perpendicularly) received by the luminescent material element in a single pass. For instance, 2024PF80183

[0140] 32 in embodiments the luminescent material element may be configured to transmit at least 20% (and at maximum 90%, such as at maximum 80%) of the first device light (perpendicularly) received by the luminescent material element in a single pass.

[0141] In specific embodiments, the luminescent material element may have a layer thickness (h) selected from the range of 20 pm - 1 mm, such as in specific embodiments 50- 200 pm. Further, in embodiments the luminescent material element may be configured to convert selected from the range of 40-95%, such as 50-90%, like at least 60% and at most 90% of the first device light received by the luminescent material element in a single pass. In this way, there may be an optimum between conversion (directly and after recycling) and thermal management of the luminescent material.

[0142] Hence, for instance in embodiments one or more of the following may apply: (a) the luminescent material element may be transparent for the first device light, and (b) the (metallic) first reflector comprises a polarization maintaining (metallic) reflector.

[0143] As indicated above, in other embodiments a scattering luminescent material element may be applied. For instance, in embodiments the luminescent material element may be configured to scatter at least 10% (and at maximum 90%) of the first device light ((perpendicularly) received by the luminescent material element in a single pass). For instance, in embodiments the luminescent material element may be configured to scatter selected from the range of 15-70%, like selected from the range of 20-50% of the first device light ((perpendicularly) received by the luminescent material element in a single pass). The scattering may be volume scattering and / or surface scattering.

[0144] The phrase “in a single pass” may refer in embodiments to the moment that a package of photons of the first device light is received by the luminescent material element. Would the luminescent material element be configured in the transmissive mode, with the first reflector configured downstream of the luminescent material element, then such “package” may be offered twice, first on its way to the luminescent material element, and then for a second time when it is reflected back, and again offered to the luminescent material element. When via a recycling the package is again offered to the luminescent material element, then there will be again two passes. Each time, the package may lose photons which are converted into luminescent material light photons. Would the luminescent material element be configured as a scattering body, then such “package” may be offered once on its way to the luminescent material element. When via a recycling the package is again offered to the luminescent material element, then there will be again a pass. Each time, the package may lose photons which are converted into luminescent material light photons. 2024PF80183

[0145] 33

[0146] As indicated above, the dichroic filter may be a kind of exit port for the luminescent material light. In specific embodiments, the dichroic filter is configured to direct at least 60%, such as at least about 70%, like especially at least 80% of the luminescent material light (received by the dichroic filter) in an optical path to the light exit, for instance at least about 90%.

[0147] In embodiments, the dichroic filter may be configured to reflect a substantial part, like at least 80%, of the first device light received by the dichroic filter. Especially, the dichroic filter may in embodiments reflect at least about 90%, more especially at least about 95%, such as 99% of the first device light received by the dichroic filter. Hence, in embodiments the dichroic filter may be configured to prevent at least 95% of the first device light received by the dichroic filter from propagating in an optical path to the light exit, like at least about 97%, more especially at least about 99%, such as 100%.

[0148] However, in other embodiments, the dichroic filter may intentionally leak some of the first device light received by the dichroic filter. This may in embodiments allow generate white system light. Hence, in embodiments the dichroic filter may be configured to direct selected from the range of 5-95%, such as selected from the range of 5-60%, like in specific embodiments selected from the range of 10-40% of the first device light received by the dichroic filter in an optical path to the light exit, such as selected from the range of about 20-30%.

[0149] As can be derived from the above, in embodiments the dichroic filter may comprise a dichroic reflector or dichroic beam splitter configured to transmit first device light (received by the dichroic filter) and reflect luminescent material light (received by the dichroic filter). In other embodiments, the dichroic filter may comprise a dichroic reflector or dichroic beam splitter configured to reflect first device light (received by the dichroic filter) and transmit luminescent material light (received by the dichroic filter).

[0150] Further, as indicated above, in specific embodiments the dichroic filter may be configured in an optical path between the polarization based beam director and the luminescent material element. Especially, in such embodiments the dichroic filter may be (a) configured to reflect at least 80% of the first device light received by the dichroic filter and transmit at least 80% of the luminescent material light received by the dichroic filter, or (b) configured to transmit at least 80% of the first device light received by the dichroic filter and reflect at least 80% of the luminescent material light received by the dichroic filter. However, other values may also be possible. Especially, in such embodiments the dichroic filter may be (a) configured to reflect at least 90% of the first device light received by the dichroic filter 2024PF80183

[0151] 34 and transmit at least 90% of the luminescent material light received by the dichroic filter, or (b) configured to transmit at least 90% of the first device light received by the dichroic filter and reflect at least 90% of the luminescent material light received by the dichroic filter. Note that this may also apply to the dichroic filter in the second series of specific embodiments. Further, option (a) may especially apply to most of the other specific embodiments described above.

[0152] Yet, in (specific) embodiments, the dichroic filter may be configured to transmit at least 20% of the first device light and reflect at least 30% of the first device light. At least part of the transmitted device light may escape from the light generating system via the light exit. Further, at least part of the reflected device light may be reused and at least partly converted into (further) luminescent material light.

[0153] Referring to e.g. the third series of specific embodiments the light generating system may further comprise a second reflector and a second quarter wave plate. Further, especially, in embodiments the light generating system may be configured such that at least part of the reflected first device light propagates from the luminescent material element to the second reflector via (i) the first quarter wave plate, (ii) the polarization based beam director, and (iii) the second quarter wave plate, and back to the luminescent material element. As indicated above, especially, in (such) embodiments the second reflector may comprise a polarization maintaining diffuser.

[0154] A combination of a quarter wave plate and a polarization maintaining diffuser is herein in embodiments also indicated as a “diffuser system”.

[0155] In embodiments, a polarization maintaining diffuser may comprise small-angle diffuse reflector, with a diffusion angle of at maximum 10° (see also above).

[0156] The polarization maintaining diffuser comprised in embodiments by the second reflector may herein also be indicated as first polarization maintaining diffuser.

[0157] In embodiments, the system light may essentially consist of the luminescent material light. In other embodiments, the system light may comprise luminescent material light and (diffused) first device light, which may escapes from the system via the dichroic filter. As indicated above, in embodiments the dichroic filter may be configured to direct only luminescent material light in a specific direction (including allowing to be transmitted), whereas in other embodiments also part of the (diffused) first device light may be directed (including allowing to be transmitted) in the same direction as the luminescent material.

[0158] In yet other embodiments, however, part of the first device light may be branched off from the first device light reaching the polarization based beam director. The 2024PF80183

[0159] 35 system may be configured such, that after diffusion of the branched of first device light, it may also escape from the system via the light exit.

[0160] Irrespective of the embodiments described above, it may also be possible to include in the system a second light generating device, of which its second device light may be comprised by the system light. The terms “second light generating device” and “second device light”, and similar terms, may also refer to any further light generating device and its device light. Here below, embodiments of the invention are described in relation to the second light generating device (but thereby not excluding the presence of further light generating devices.

[0161] Note that the embodiments in relation to the type of first light generating devices may also apply to second light generating devices (see also above). In embodiments, the second light generating device may comprise a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multi -junction lightemitting diodes.

[0162] Hence, in embodiments one or more of the following may apply: (a) the light generating system may be configured such that at least part of the first device light is branched off in an optical path to the light exit, thereby bypassing the luminescent material element, and wherein (the light generating system is configured such that) the system light comprises part of the first device light that is branched off, and (b) the light generating system may comprise a second light generating device, wherein the second light generating device is configured to generated second device light, and wherein (the light generating system is configured such that) the system light comprises part of the second device light.

[0163] It may be desirable that the device light that escapes from the light generating system is (also) diffused. Hence, in specific embodiments, wherein branching of from the first device light is applied, the light generating system may be configured such that part of the first device light is branched off and guided to a (second) polarization maintaining diffuser via a third quarter wave plate, wherein the first device light reaching the second quarter wave plate comprises linear polarized light. Further, in (other) specific embodiments wherein the light generating system comprises the second light generating device, and further comprises a second polarization maintaining diffuser, and a third quarter wave plate, in embodiments (A) the light generating system may be configured such that at least part of the second device light is guided to the second polarization maintaining diffuser via the third quarter wave plate, wherein the second device light reaching the third quarter wave plate comprises linear polarized light; (B) the light generating system may further comprise a first 2024PF80183

[0164] 36 beam combiner; wherein the light generating system is configured such that at least part of the light (which may especially be second device light) received by the second polarization maintaining diffuser is diffused (by the second polarization maintaining diffuser), while maintaining at least part of (the polarization type (but changing the handedness ol)) the polarization, and guided in an optical path to the light exit via the first beam combiner (together with the luminescent material light); and (C) the light generating system may be configured to generate system light comprising in an operational mode of the light generating system at least part of the luminescent material light and at least part of the light diffused at the second polarization maintaining diffuser (and escaped from the light generating system via the light exit).

[0165] For embodiments of a quarter wave plate, see also above. For embodiments of a polarization maintaining diffuser, see also above. Further, the first beam combiner may have the function of a polarizing beam splitter.

[0166] A polarizing beam splitter may be used to split the (second) device light and diffused device light. Hence, this may imply that the (second) device light reaching the first polarizing beam splitter and the diffused device light reaching the first polarizing beam splitter have different polarizations. One may be s-polarized and the other one may be p- polarized. One may be elliptically polarized, and the other one may be s-polarized or p- polarized. Especially, however, the diffused device light and (second) device light differ in polarization, like s-polarized light and p-polarized light, or both elliptically polarized, but one comprising more s-polarization than p-polarization, and the other one comprising more p- polarization than s-polarization. For example, in embodiments, the (second) device light and the diffused device light may each comprise a linear polarization, wherein the linear polarizations of the (second) device light and the diffused device light may be about 90° rotated with respect to each other. In specific embodiments, one of the (second) device light and the diffused device light may comprise the first linear polarization and the other one of the (second) device light and the diffused device light may comprise the second linear polarization. In such embodiments, the first linear polarization and the second linear polarization may be about 90° rotated relative to each other, i.e., they may be (orthogonal or) complementary relative to each other.

[0167] Further, in embodiments the (second) device light reaching the first polarizing beam splitter and the diffused device light reaching the first polarizing beam splitter (having different polarizations) may be perpendicularly incident on the polarizing beam splitter. 2024PF80183

[0168] 37

[0169] Note that in embodiments the first beam combiner may be transmissive for the luminescent material light. Optionally, the first beam combiner may be transmissive for at least part of the diffused first device light reaching - in specific embodiments - the first beam combiner. Hence, in analogy to the polarization based beam director, in embodiments, the first beam combiner may be configured to transmit at least 80%, such as at least about 85%, like in embodiments at least about 90% of the luminescent material light. Hence, in embodiments the first beam combiner may discriminate between s-polarized first device light and p-polarized first device light, but may (essentially) be transmissive for luminescent material light, irrespective of its (linear) polarization. Hence, in embodiments the polarization based beam director may have DBS-functionality and PBS-functionality, and may in such embodiments be indicated as DBS-PBS (see also above).

[0170] In embodiments, the light generating system may further comprise a control system. In embodiments, the control system may be configured to control a spectral power distribution of the system light by controlling the first light generating device and the second light generating device.

[0171] In specific embodiments, in an operational mode of the light generating system, the system light may be white light having a color rendering index of at least 65 and a correlated color temperature selected from the range of 2000-12000 K.

[0172] 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.

[0173] The term “white light”, and similar terms, herein, is known to the person skilled in the art. It may especially relate to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700- 20000 K, for general lighting especially in the range of about 2000-7000 K, such as in the range of 2700 K and 6500 K. In embodiments, e.g. for backlighting purposes, or for other purposes, the correlated color temperature (CCT) may especially be in the range of about 2024PF80183

[0174] 38

[0175] 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL. In specific embodiments, the correlated color temperature (CCT) may be selected from the range of 6000-12000 K, like selected from the range of 7000-12000 K, like at least 8000 K. Yet further, in embodiments the correlated color temperature (CCT) may be selected from the range of 6000-12000 K, like selected from the range of 7000-12000 K, in combination with a CRI of at least 70.

[0176] 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. 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.

[0177] 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 2024PF80183

[0178] 39 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 440-495 nm wavelength range.

[0179] 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.

[0180] 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.

[0181] 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 2024PF80183

[0182] 40 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.

[0183] 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.

[0184] 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, which can only operate in a single operation mode (i.e. “on”, without further tunability).

[0185] 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.

[0186] 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 2024PF80183

[0187] 41 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 first quarter wave plate, the polarization based beam director, the dichroic filter, the luminescent material element, etc.

[0188] In yet a further aspect, the invention also provides a lighting fixture comprising the light generating system as defined herein. Hence, in yet a further aspect, the light generating system may comprise a device selected from the group of a lamp, a luminaire, or a lighting fixture, wherein the lamp, luminaire, or lighting fixture may comprise one or more elements of the light generating system, such as one or more of the first light generating device, the first quarter wave plate, the polarization based beam director, the dichroic filter, the luminescent material element and the light generating system may further comprise e.g. a control system configured to control the device.

[0189] The term “lighting fixture” may refer to a light emitting system like a moving head, a search light, a stage light, etc. Generally these fixtures may have various control options for changing one or more of the direction of the light (e.g. via gimbals or rotary stages), the beam angle / width (e.g. via zoom optics), the beam pattern (e.g. via mechanical selection of a specific aperture that defines a virtual and patterned source for the further projection optics), the color of the light (e.g. via mechanical selection of a certain color filter), and of course the luminous flux, and mostly these are remotely controllable.

[0190] BRIEF DESCRIPTION OF THE DRAWINGS

[0191] 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:

[0192] Figs, la-lc, 2a-2c, and Fig. 3 schematically depict some embodiments.

[0193] Figs. 4 schematically depicts a further embodiment.

[0194] Fig. 5 schematically depicts some (application) embodiments. The schematic drawings are not necessarily to scale. 2024PF80183

[0195] 42

[0196] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0197] Referring to Figs, la-lc, 2a-2c, and 3, in embodiments, the invention provides a light generating system 1000 comprising a first light generating device 10, a first quarter wave plate 721, a polarization based beam director 1510, a dichroic filter 750, a luminescent material element 2000, and a light exit 1090. Furthermore, in embodiments, the first light generating device 10 may be configured to generate first device light 11. Moreover, in embodiments, the first light generating device 10 may comprise a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multijunction light-emitting diodes. Further, in embodiments, the luminescent material element 2000 may be configured in a light receiving relationship with the first light generating device 10 and may be configured to convert part of the first device light 11 received by the luminescent material element 2000 into luminescent material light 201. Furthermore, in embodiments, the light generating system 1000 may be configured such that at least part of the (generated) luminescent material light 201 propagates along an optical path via the dichroic filter 750 to the light exit 1090. In further embodiments, the first quarter wave plate 721 and the polarization based beam director 1510 may be configured in an optical path between the first light generating device 10 and the luminescent material element 2000. Furthermore, in embodiments, relative to a propagation of the first device light 11 from the first light generating device 10 to the luminescent material element 2000, the first quarter wave plate 721 may be configured downstream of the polarization based beam director 1510. Especially, the polarization based beam director 1510 may be configured to reflect or transmit (at least) first device light 11, received by the polarization based beam director 1510, in dependence of its linear polarization. Further, in embodiments, the light generating system 1000 may be configured such that the first device light 11 from the first light generating device 10 reaching the polarization based beam director 1510 may comprise linear polarized light. Furthermore, in embodiments, one or more of the following applies: (a) the light generating system 1000 may comprise a first reflector 610, configured downstream of the luminescent material element 2000. Furthermore, in embodiments, part of the first device light 11, received by the luminescent material element 2000, may be transmitted by the luminescent material element 2000, reflected at the first reflector 610, and transmitted (again) by the luminescent material element 2000 in an optical path to the polarization based beam director 1510, thereby providing reflected first device light 11, and (b) part of the first device light 11 may be reflected by the luminescent material element 2000 in an optical path to the polarization based beam director 1510, thereby providing reflected first device light 11. 2024PF80183

[0198] 43

[0199] Furthermore, in embodiments, the light generating system 1000 may be (further) configured such that at least part of the reflected first device light 11, in an optical path (i) propagates away from the luminescent material element 2000 and (ii) also returns to the luminescent material element 2000. Especially, this optical path may be (a) at least twice via the polarization based beam director 1510, and (b) twice (forth and back) via the first quarter wave plate 721, whereby the luminescent material element 2000 converts at least part of the reflected first device light 11, received by the luminescent material element 2000 via this optical path, into further luminescent material light 201’. Especially, the light generating system 1000 may be configured to generate system light 1001 comprising at least part of the luminescent material light 201 and at least part of the further luminescent material light 201’ (escaped from the light generating system 1000 via the light exit 1090).

[0200] In further embodiments, the first light generating device 10 may be configured to generate first device light 11 having a first peak wavelength XPiselected from the wavelength range of 430-490 nm. Furthermore, in embodiments, the luminescent material element 2000 may be configured to convert part of the first device light 11 received by the luminescent material element 2000 into luminescent material light 201,201’ having a centroid wavelength Xcselected from 500-680 nm. Moreover, in embodiments, Xc- XPi> 40 nm.

[0201] In further embodiments, the first light generating device 10 may comprise a laser diode.

[0202] Moreover, in embodiments the light generating system 1000 may comprise an arrangement of a plurality of first light generating devices 10. In embodiments, the light generating system 1000 may comprise a laser bank comprising a plurality of first light generating devices 10 each comprising a laser diode.

[0203] Further, in embodiments, the light generating system 1000 may comprise the first reflector 610. Especially, the first reflector 610 may be a metallic reflector. Especially, the luminescent material element 2000 may be configured to transmit at least 10% (and at maximum 90%) of the first device light 11 (perpendicularly) received by the luminescent material element 2000 in a single pass.

[0204] Furthermore, in embodiments, one or more of the following applies: (a) the luminescent material element 2000 may be transparent for the first device light 11, and (b) the (metallic) first reflector 610 may comprise a polarization maintaining metallic reflector.

[0205] Hence, amongst others configurations are proposed where the first device light 11, like the laser light, may pass multiple times through the phosphor and until a substantial 2024PF80183

[0206] 44 part, such as even all, of the (blue) first device light is absorbed as shown in Figs, la, lb, and 1c, for a transparent phosphor.

[0207] For instance, in embodiments in Fig. 1c, first device light 11, e.g. blue laser light, with e.g. an s-polarization first goes through the PBS and then through a X / 4 plate and after getting reflected by the metallic reflector and transmitted by the X / 4 plate to become p- polarization and gets reflected by the PBS towards the phosphor. The first device light reflected (for the first time) at the first reflector 610 is indicated with reference 11’. The first device light 11 ’ that is reflected at the dichroic filter 750, and propagates back in the direction of the luminescent material element 2000, is indicated with reference 11”. P- polarized light then go through a second X / 4 plate to become circularly polarized and reaches transparent phosphor with a metallic reflector. After partial absorption (and generation of further luminescent material light 201’”) by the phosphor the rest of the blue light gets reflected by the metallic reflector and the sense of circularly polarized is reversed. This first device light 11, reflected again at the luminescent material element 2000, more especially the first reflector 610 downstream therefore, and propagating in the direction of the dichroic filter 750, is indicated with reference 11’”. After going through the X / 4 plate it becomes s- polarized and it goes through the PBS. On the other side of the PBS a dichroic filter reflects s-polarized light towards the phosphor where it gets a second chance to be absorbed by the phosphor. Part of the blue becomes p-polarized at the PBS and eventually gets directed back to the laser. The embodiments schematically depicted in Figs, la and lb essentially work in a similar fashion.

[0208] In further embodiments, the luminescent material element 2000 may be configured to scatter at least 10% (and at maximum 90%) of the first device light 11 (perpendicularly) received by the luminescent material element 2000 in a single pass.

[0209] The indications of the linear polarizations in the schematical drawings may not be limiting. For instance, it may also be possible that the first light generating device 100 generates first device light having a p-polarization.

[0210] In drawings of the embodiments, an optical element 510 has been indicated, this optical element may e.g. be an optical integrator element. An optical element, like an optical integrator, may also be configured in the optical path between the first light generating device 10 and the polarization based beam director 1510. Further, an optical element, like an optical integrator, may also be configured in the optical path between polarization based beam director 1510and the second quarter wave plate 722. 2024PF80183

[0211] 45

[0212] The luminescent material element 2000 may have a primary face, e.g. the face on the right which receives the device light 11, and a secondary face, e.g. the face on the left that is thermal contact, with the reflector 610 (which may e.g. be a reflective thermally conductive element or a reflector on a thermally conductive element).

[0213] For instance, in Fig. 2c, embodiments of a configuration is shown where scattering phosphor may be used. Here blue laser light with an s-polarization first goes through the PBS and then through a X / 4 plate and after getting reflected by the metallic reflector and transmitted by the X / 4 plate to become p-polarization and gets reflected by the PBS towards the phosphor. After partial absorption by the phosphor the rest of the blue light becomes depolarized and it is sent towards the PBS. At the PBS the p-polarized component of unpolarized light gets reflected towards the metallic mirror and thus becoming s-polarized after going through X / 4 plate and also getting reflected. This s component goes through the PBS and gets lost at the Laser. S-polarized component of depolarized blue light coming from the phosphor is transmitted by the PBS. A dichroic filter reflecting blue light can be used after the PBS sending s-polarized light back to the phosphor. This way s-polarized blue light gets trapped and gets reflected until all s-polarized blue light is totally absorbed by the phosphor and phosphor light. Figs. 2a 2b essentially work in a similar fashion. Unpolarized light is indicated with reference u.

[0214] In embodiments, the luminescent material element 2000 may have a layer thickness (h) selected from the range of 50-200 pm. Further, in embodiments, the luminescent material element 2000 may be configured to convert at least 60% and at most 90% of the first device light 11 received by the luminescent material element 2000 in a single pass.

[0215] Further, in embodiments, the dichroic filter 750 may be configured to direct at least 80% of the luminescent material light 201 (received by the dichroic filter 750) in an optical path to the light exit 1090. Moreover, in embodiments, the dichroic filter 750 may be configured to direct selected from the range of 10-40% of the first device light 11 received by the dichroic filter 750 in an optical path to the light exit 1090. Moreover, in embodiments, the dichroic filter 750 may be configured to reflect at least 80% of the first device light 11 received by the dichroic filter 750. Furthermore, in embodiments, the dichroic filter 750 may be configured to prevent at least 95% of the first device light 11 received by the dichroic filter 750 from propagating in an optical path to the light exit 1090. Moreover, in embodiments the dichroic filter 750 may comprise a dichroic reflector or dichroic beam splitter configured to transmit first device light 11 (received by the dichroic filter 750) and 2024PF80183

[0216] 46 reflect luminescent material light 201 (received by the dichroic filter 750). In further embodiments, the dichroic filter 750 may comprise a dichroic reflector or dichroic beam splitter configured to reflect first device light 11 (received by the dichroic filter 750) and transmit luminescent material light 201 (received by the dichroic filter 750).

[0217] Figs, la-lc may refer to examples of the above described first, second, and third series of specific embodiments. Further, Figs. 2a-2c may refer to examples of the above described fourth, fifth, and sixth series of specific embodiments.

[0218] Referring to Fig. 3, as a variant on the second series of embodiments, which may thus also be applied in the fifth series of embodiments, the dichroic filter 750 may be configured in an optical path between the polarization based beam director 1510 and the luminescent material element 2000.

[0219] Especially, the dichroic filter 750 may be (a) configured to reflect at least 80% of the first device light 11 received by the dichroic filter 750 and transmit at least 80% of the luminescent material light 201 received by the dichroic filter 750 (e.g. Figs, la, 1c, 2a, 2c), or (b) configured to transmit at least 80% of the first device light 11 received by the dichroic filter 750 and reflect at least 80% of the luminescent material light 201 received by the dichroic filter 750 (e.g. Figs, lb, 2b, 3).

[0220] Referring to e.g. Figs. 1c, 2c, though this may also apply to Figs, lb, 2b, and 3, in embodiments, the light generating system 1000 may further comprise a second reflector 620 and a second quarter wave plate 722. Moreover, in embodiments, the light generating system 1000 may be configured such that at least part of the reflected first device light 11 propagates from the luminescent material element 2000 to the second reflector 620 via (i) the first quarter wave plate 721, (ii) the polarization based beam director 1510, and (iii) the second quarter wave plate 722, and back to the luminescent material element 2000. Moreover, in embodiments, the second reflector 620 may comprise a (first) polarization maintaining diffuser.

[0221] Luminescent material element (phosphor) thicknesses where different degree of conversion is obtained for phosphor having different extinction coefficient have been calculated, and the results are shown in the Table below: 2024PF80183

[0222] In this table it can be seen that the thickness of the phosphor can be reduced by a factor of 2 with respect to sending the laser directly to the phosphor when the configurations shown in Figs, la-lc (using transparent phosphor) for different conversion rates and extinction coefficients. Regarding configuration shown in Figs. 2a-2c where a scattering phosphor is used the thickness can be reduced by a factor of 1.5 with respect to sending the laser directly to the phosphor, without using recycling.

[0223] In further embodiments, the light generating system 1000 may be configured such that at least part of the first device light 11 may be branched off in an optical path to the light exit 1090, thereby bypassing the luminescent material element 2000. Moreover, in embodiments, the system light 1001 may comprise part of the first device light 11 that may be branched off. Such embodiments are not depicted herein.

[0224] Referring to e.g. Fig. 4 in embodiments the light generating system 1000 may comprise a second light generating device 20. Further, in embodiments, the second light generating device 20 may be configured to generate second device light 21. Especially, the second light generating device 20 may comprise a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multi -junction lightemitting diodes. Especially, the light generating system 1000 may be configured such that the system light 1001 may comprise part of the second device light 21.

[0225] Moreover, in embodiments the light generating system 1000 may be configured such that part of the first device light 11 may be branched off and guided to a (second) polarization maintaining diffuser 710 via a third quarter wave plate 723. Especially, the first device light 11 reaching the second quarter wave plate 723 may comprise linear polarized light. Yet, in embodiments, the light generating system 1000 may comprise the second light generating device 20, and may further comprise a second polarization maintaining diffuser 710, and a third quarter wave plate 723. Further, in embodiments, the light generating system 1000 may be configured such that at least part of the second device light 21 may be guided to the second polarization maintaining diffuser 710 via the third 2024PF80183

[0226] 48 quarter wave plate 723. Especially, the second device light 21 reaching the third quarter wave plate 723 may comprise linear polarized light. Moreover, in embodiments, the light generating system 1000 may further comprise a first beam combiner 1520. Further, in embodiments, the light generating system 1000 may be configured such that at least part of the (second device) light received by the second polarization maintaining diffuser 710 may be diffused (by the second polarization maintaining diffuser 710), while maintaining at least part of (the polarization type (but changing the handedness ol)) the polarization, and guided in an optical path to the light exit 1090 via the first beam combiner 1520 (together with the luminescent material light 201). In further embodiments, the light generating system 1000 may be configured to generate system light 1001 comprising in an operational mode of the light generating system 1000 at least part of the luminescent material light 201 and at least part of the light diffused at the second polarization maintaining diffuser 710 (and escaped from the light generating system 1000 via the light exit 1090).

[0227] Further, an optical element, like an optical integrator, may also be configured in the optical path between first beam combiner 1520 and the third quarter wave plate 723.

[0228] Note that more optical elements may be comprised by the schematically depicted embodiments of Figs. la-4.

[0229] Furthermore, in embodiments, the system 1000 may comprise a control system 300. The control system 300 may be configured to control a spectral power distribution of the system light 1001 by controlling the first light generating device 10 and the second light generating device 20. Moreover, in embodiments, the first light generating device 10 and / or the second light generating device 20 may comprise a laser bank.

[0230] In specific embodiments, the luminescent material element 2000 may comprise a luminescent material 200 of the type AsBsOnT'e. Especially, A may comprise one or more of Y, La, Gd, Tb and Lu. Moreover, in embodiments, B may comprise one or more of Al, Ga, In and Sc.

[0231] In further embodiments, in an operational mode of the light generating system 1000, the system light 1001 may be white light having a color rendering index of at least 65 and a correlated color temperature selected from the range of 2000-12000 K.

[0232] Fig. 5 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. 5 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector 2024PF80183

[0233] 49 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. 5 schematically depicts embodiments of a lighting device 1200 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 1200 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.

[0234] Fig. 5 also schematically depicts an embodiment of an outdoor light, or stage light, or stadium light. Fig. 5 also schematically depicts a vehicle, like an automobile, but this may also be a truck, a motor cycle, etc. etc., with automotive lighting 4, e.g. headlights. These automotive lighting 4 may also comprise the lighting device 1200.

[0235] In specific embodiments, the invention provides a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a vehicle light, lighting fixture, an automotive lighting device, a stage lighting device.

[0236] 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 embodiments 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".

[0237] 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 2024PF80183

[0238] 50 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.

[0239] 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.

[0240] 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.

[0241] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0242] 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”.

[0243] The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0244] 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 ol) the method as described herein.

[0245] 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.

[0246] 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 2024PF80183

[0247] 51 more of the characterizing features described in the description and / or shown in the attached drawings.

[0248] 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

2024PF8018352CLAIMS:

1. A light generating system (1000) comprising a first light generating device(10), a first quarter wave plate (721), a polarization based beam director (1510), a dichroic filter (750), a luminescent material element (2000), and a light exit (1090), wherein: the first light generating device (10) is configured to generate first device light(11); wherein the first light generating device (10) comprises a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multijunction light-emitting diodes; the luminescent material element (2000) is configured in a light receiving relationship with the first light generating device (10) and is configured to convert part of the first device light (11) received by the luminescent material element (2000) into luminescent material light (201); wherein the light generating system (1000) is configured such that at least part of the luminescent material light (201) propagates along an optical path via the dichroic filter (750) to the light exit (1090); the first quarter wave plate (721) and the polarization based beam director (1510) are configured in an optical path between the first light generating device (10) and the luminescent material element (2000), wherein relative to a propagation of the first device light (11) from the first light generating device (10) to the luminescent material element (2000), the first quarter wave plate (721) is configured downstream of the polarization based beam director (1510); the polarization based beam director (1510) is configured to reflect or transmit first device light (11), received by the polarization based beam director (1510), in dependence of its linear polarization; wherein the light generating system (1000) is configured such that the first device light (11) from the first light generating device (10) reaching the polarization based beam director (1510) comprises linear polarized light; one or more of the following applies: (a) the light generating system (1000) comprises a first reflector (610), configured downstream of the luminescent material element (2000); wherein part of the first device light (11), received by the luminescent material element (2000), is transmitted by the luminescent material element (2000), reflected at the first reflector (610), and transmitted by the luminescent material element (2000) in an optical2024PF8018353 path to the polarization based beam director (1510), thereby providing reflected first device light (11), and (b) part of the first device light (11) is reflected by the luminescent material element (2000) in an optical path to the polarization based beam director (1510), thereby providing reflected first device light (11); the light generating system (1000) is configured such that at least part of the reflected first device light (11), in an optical path (i) propagates away from the luminescent material element (2000) and (ii) also returns to the luminescent material element (2000); wherein this optical path is (a) at least twice via the polarization based beam director (1510), and (b) twice via the first quarter wave plate (721), whereby the luminescent material element (2000) converts at least part of the reflected first device light (11), received by the luminescent material element (2000) via this optical path, into further luminescent material light (201’); the dichroic filter (750) is configured to direct at least 80% of the luminescent material light (201) in an optical path to the light exit (1090); the dichroic filter (750) is configured to transmit at least 20% of the first device light (11) and reflect at least 30% of the first device light (11); and the light generating system (1000) is configured to generate system light (1001) comprising at least part of the luminescent material light (201) and at least part of the further luminescent material light (201’).

2. The light generating system (1000) according to claim 1, wherein the first light generating device (10) is configured to generate first device light (11) having a first peak wavelength XPiselected from the wavelength range of 430-490 nm; wherein the luminescent material element (2000) is configured to convert part of the first device light (11) received by the luminescent material element (2000) into luminescent material light (201,201’) having a centroid wavelength selected from 500-680 nm, wherein kc- XPi> 40 nm; and wherein the first light generating device (10) comprises a laser diode.

3. The light generating system (1000) according to any one of the preceding claims 1-2, wherein the light generating system (1000) comprises the first reflector (610), wherein the first reflector (610) is a metallic reflector; and wherein the luminescent material element (2000) is configured to transmit at least 10% of the first device light (11) received by the luminescent material element (2000) in a single pass.2024PF80183544. The light generating system (1000) according to any one of the preceding claims, wherein one or more of the following applies: (a) the luminescent material element (2000) is transparent for the first device light (11), and (b) the first reflector (610) comprises a polarization maintaining metallic reflector.

5. The light generating system (1000) according to any one of the preceding claims, wherein the luminescent material element (2000) has a layer thickness (h) selected from the range of 50-200 pm; and wherein the luminescent material element (2000) is configured to convert at least 60% and at most 90% of the first device light (11) received by the luminescent material element (2000) in a single pass.

6. The light generating system (1000) according to any one of the preceding claims, wherein the dichroic filter (750) is configured to direct at least 90% of the luminescent material light (201) in an optical path to the light exit (1090).

7. The light generating system (1000) according to any one of the preceding claims 1-6, wherein the first light generating device (10) comprises a first laser bank.

8. The light generating system (1000) according to any one of the preceding claims, wherein the dichroic filter (750) is configured reflect at least 80% of the first device light (11) received by the dichroic filter (750).

9. The light generating system (1000) according to any one of the preceding claims 1-6, wherein the dichroic filter (750) is configured in an optical path between the polarization based beam director (1510) and the luminescent material element (2000); wherein the dichroic filter (750) is (a) configured to reflect at least 80% of the first device light (11) received by the dichroic filter (750) and transmit at least 80% of the luminescent material light (201) received by the dichroic filter (750), or (b) configured to transmit at least 80% of the first device light (11) received by the dichroic filter (750) and reflect at least 80% of the luminescent material light (201) received by the dichroic filter (750).

10. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) further comprises a second reflector (620) and a second quarter wave plate (722); wherein the light generating system (1000) is2024PF8018355 configured such that at least part of the reflected first device light (11) propagates from the luminescent material element (2000) to the second reflector (620) via (i) the first quarter wave plate (721), (ii) the polarization based beam director (1510), and (iii) the second quarter wave plate (722), and back to the luminescent material element (2000); wherein the second reflector (620) comprises a first polarization maintaining diffuser.

11. The light generating system (1000) according to any one of the preceding claims, wherein one or more of the following applies: (a) the light generating system (1000) is configured such that at least part of the first device light (11) is branched off in an optical path to the light exit (1090), thereby bypassing the luminescent material element (2000), and wherein the system light (1001) comprises part of the first device light (11) that is branched off, and (b) the light generating system (1000) comprises a second light generating device (20), wherein the second light generating device (20) is configured to generated second device light (21); wherein the second light generating device (20) comprises a solid state light source selected from the group comprising laser diodes, superluminescent diodes, and stacked multi -junction light-emitting diodes; and wherein the light generating system (1000) is configured such that the system light (1001) comprises part of the second device light (21).

12. The light generating system (1000) according to claim 11, wherein the light generating system (1000) comprises the second light generating device (20), and further comprises a second polarization maintaining diffuser (710), and a third quarter wave plate (723); wherein: the light generating system (1000) is configured such that at least part of the second device light (21) is guided to the second polarization maintaining diffuser (710) via the third quarter wave plate (723); wherein the second device light (21) reaching the third quarter wave plate (723) comprises linear polarized light; and the light generating system (1000) further comprises a first beam combiner (1520); wherein the light generating system (1000) is configured such that at least part of the light received by the second polarization maintaining diffuser (710) is, while maintaining at least part of the polarization, and guided in an optical path to the light exit (1090) via the first beam combiner (1520); and the light generating system (1000) is configured to generate system light (1001) comprising in an operational mode of the light generating system (1000) at least part2024PF8018356 of the luminescent material light (201) and at least part of the light diffused at the second polarization maintaining diffuser (710).

13. The light generating system (1000) according to claim 12, further comprising a control system (300); wherein the control system (300) is configured to control a spectral power distribution of the system light (1001) by controlling the first light generating device (10) and the second light generating device (20); wherein the first light generating device (10) and / or the second light generating device (20) comprises a laser bank.

14. The light generating system (1000) according to any one of the preceding claims, wherein the luminescent material element (2000) comprises a luminescent material (200) of the type AsBsOnT'e. 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, and wherein in an operational mode of the light generating system (1000), the system light (1001) is white light having a color rendering index of at least 65 and a correlated color temperature selected from the range of 2000-12000 K.

15. A lighting device (1200) selected from the group of a lamp (1), a luminaire (2), a projector device (3), a vehicle light, lighting fixture, an automotive lighting device, a stage lighting device, comprising the light generating system (1000) according to any one of the preceding claims.

Images