New configuration for eye-safe laser lighting using depolarizing diffuser

Abstract

The invention provides a light generating system (1000) comprising a first light generating device (110), a first depolarizing diffuser (410), a first polarizing beam splitter (PBS1), a first dichroic beam splitter (DBS1), a luminescent material (200), and a light exit (1090); wherein: (A) the first light generating device (110) is configured to provide first device light (111), wherein the first light generating device (110) comprises a laser light source; the light generating system (1000) is configured such that the first device light (111) reaching the first depolarizing diffuser (410) comprises polarized light having a first linear polarization; (B) the first depolarizing diffuser (410) is configured to diffuse at least part of the first device light (111) and change at least part of the polarized light having the first linear polarization into unpolarized light; (C) the first polarizing beam splitter (PBS1) is configured downstream of the first depolarizing diffuser (410) and is configured to direct the first device light (111) in dependence of its linear polarization (a) in an optical path to the luminescent material (200) or (b) in an optical path in a direction of the light exit (1090); (D) the luminescent material (200) is configured to convert at least part of the first device light (111) received via the first polarizing beam splitter (PBS1) into luminescent material light (201); (E) the first dichroic beam splitter (DBS1) is configured to receive luminescent material light (201) from the luminescent material (200) and to direct the luminescent material light (201) in an optical path to the light exit (1090); and (F) the light generating system (1000) is configured to generate in an operational mode of the light generating system (1000) system light (1001) at least comprising luminescent material light (201) and at least part of the first device light (111).

Description

[0001] NEW CONFIGURATION FOR EYE-SAFE LASER LIGHTING USING DEPOLARIZING

[0002] DIFFUSER

[0003] FIELD OF THE INVENTION

[0004] The invention relates to a light generating system and to a lighting device comprising such light generating system.

[0005] BACKGROUND OF THE INVENTION

[0006] Light engines comprising a laser are known in the art. US2015204514 describes a light engine comprises: a wavelength conversion device, receiving source light of a first wavelength range and a first polarization, generating light of a second wavelength range from a portion of the received source light, at least a portion of the second wavelength range being non-overlapping with the first wavelength range, the wavelength conversion device reflects output light comprising the generated light and comprises a polarization converter that sets at least some of the output light to a second polarization, different from the first polarization; and a dichroic element, that receives the reflected output light and directs light of the first polarization differently from light of the second polarization. The document also indicates that source light of a first color is provided from a polarized source, such as a laser, which is typically polarized, for example as blue light with p polarization.

[0007] SUMMARY OF THE INVENTION

[0008] High brightness light sources can be used in various applications including spots, stage-lighting, headlamps, home and office lighting, and automotive lighting. For this purpose, laser-phosphor technology can be used, wherein a laser provides laser light and a remote phosphor converts laser light into converted light. A relatively straightforward way to produce white light using lasers is to use (blue) laser light in combination with a (yellow) phosphor to generate phosphor converted light. Laser-phosphor systems may allow generation of high brightness light and may therefore be used in projection systems, including displays such as cinema projectors and projectors for home, school, and office applications, car front lighting, search lighting, stage lighting, architectural lighting, and special lighting applications. In general, a laser-phosphor light engine may be capable to generate only a single color point as defined by the luminescent converter. Creation of a product range providing different color points may be costly as it requires multiple unique components to be designed, qualified, produced, and kept in stock. In other cases, e.g. in RGB LCD-based projection systems, the maximum brightness is limited by the components used, the engine volume is large due to the many components, and the system cost are high due to the many dedicated components.

[0009] Laser-phosphor systems may be capable to generate only a single color point as defined by the luminescent converter, the wavelength of the blue pump light source, and the realized ratio of blue and luminescent light in the output light. Creation of a product range providing different color points of the output beam may in this case be elaborate as it requires multiple unique components to be designed, qualified, produced, and kept in stock. In other cases, e.g. in RGB LCD-based projection systems, the maximum brightness may be limited by the components used, the engine volume may be large due to the many components, and the system cost are high due to the many dedicated components.

[0010] It appears desirable to construct high power light sources as safe as possible. Hence, it is an aspect of the invention to provide an alternative light generating system which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0011] According to a first aspect, the invention provides a light generating system (“system”) comprising a first light generating device, a luminescent material, and a light exit. Further, the light generating system may comprise a first depolarizing diffuser, a first polarizing beam splitter (PBS1), and a first dichroic beam splitter (DBS1). Especially, the first light generating device may be configured to provide first device light (e.g. blue light). In specific embodiments, the first light generating device may comprise a laser light source (herein also indicated as “laser”), such as a diode laser (or laser diode), or laser bank comprising a plurality of (diode) lasers. Further, in embodiments the light generating system may be configured such that the first device light reaching the first depolarizing diffuser comprises polarized light having a first linear polarization. Further, in embodiments the first depolarizing diffuser may be configured to diffuse at least part of the first device light (received by the first depolarizing diffuser) and change at least part of the polarized light having the first linear polarization into unpolarized light. Especially, the first linear polarization (and the second linear polarization) may be selected from s-polarization and p- polarization. Further, in embodiments the first polarizing beam splitter (PBS1) may be configured downstream of the first depolarizing diffuser and may be configured to direct first device light (received by the first polarizing beam splitter (PBS1)) in dependence of its linear polarization (a) in an optical path to the luminescent material or (b) in an optical path in a direction of the light exit. In embodiments, the luminescent material may be configured to convert at least part of the first device light received via the first polarizing beam splitter (PBS1) into luminescent material light. In embodiments, the first dichroic beam splitter (DBS1) may be configured to receive luminescent material light from the luminescent material and (to) direct (the luminescent material light) in an optical path to the light exit, Yet, in embodiments the light generating system may be configured to generate (in an operational mode of the light generating system) system light at least comprising luminescent material light (and optionally also at least part of the first device light). Hence, amongst others the invention provides a light generating system comprising a first light generating device, a first depolarizing diffuser, a first polarizing beam splitter (PBS1), a first dichroic beam splitter (DBS1), a luminescent material, and a light exit; wherein: (A) the first light generating device is configured to provide first device light, wherein the first light generating device comprises a laser (light source); the light generating system is configured such that the first device light reaching the first depolarizing diffuser comprises polarized light having a first linear polarization; (B) the first depolarizing diffuser is configured to diffuse at least part of the first device light and change at least part of the polarized light having the first linear polarization into unpolarized light; (C) the first polarizing beam splitter (PBS1) is configured downstream of the first depolarizing diffuser and is configured to direct the first device light in dependence of its linear polarization (a) in an optical path to the luminescent material or (b) in an optical path in a direction of the light exit; (D) the luminescent material is configured to convert at least part of the first device light received via the first polarizing beam splitter (PBS1) into luminescent material light; (E) the first dichroic beam splitter (DBS1) is configured to receive luminescent material light from the luminescent material and to direct (the luminescent material light) in an optical path to the light exit; and (F) the light generating system is configured to generate (in an operational mode of the light generating system (1000)) system light at least comprising luminescent material light. In an operational mode (of the light generating system) the system light may comprise the luminescent material light and at least part of the first device light.

[0012] With such system, relatively easy a high power beam of light may be provided, that may have a controllable production plant set spectral power distribution and / or a user controllable spectral power distribution, which may also be relatively robust and safe. A limited number of optical components may be applied, and damage of some critical optical components may not lead to escape of a high power beam with too high intensity from the system, or may not lead to an escape of a high power beam from the system at all. Further, with such system high intensity light with correlated color temperatures selected from the range of 1800-12000 K may be possible, such as correlated color temperatures selected from the range of 2000-10000 K. Hence, amongst others the invention provides a new configuration for eye-safe laser lighting using depolarizing diffuser.

[0013] As indicated above, the invention provides a light generating system comprising a first light generating device, a luminescent material, and a light exit, which may also comprise a first depolarizing diffuser, a first polarizing beam splitter , and a first dichroic beam splitter . Embodiments of the system are described below.

[0014] The light generating system comprises a first light generating device. In embodiments, the light generating system may also comprise a second light generating device. For the light generating device(s), some embodiments are described below.

[0015] The light generating device(s) may be configured to generate device light. Therefore, in embodiments, the light generating device(s) may comprise solid-state light source(s). 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 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). 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 comprising a plurality of first lasers. 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.

[0016] In embodiments, 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). Especially, a laser bank may comprise a light emitting arrangement comprising an (2D) array of a plurality of laser diodes arranged on a thermally conductive carrier and a (lens array having a) plurality of collimator lenses corresponding to the laser diodes such that each laser diode of the plurality of laser diodes comprises a collimator lens for collimating laser light emitted by the laser diode. The arrangement may comprise a package architecture or a canned architecture. In case of the package architecture a laser diode chip array is arranged on the thermally conductive carrier. A plurality of electrodes may be present for electrically connecting the plurality of laser diodes. The 2D array may e.g. comprise at least 8 laser diodes. 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. Laser banks may be used to boast the input power.

[0017] Note that an array of solid state light sources may provide multiple light generating devices, such as a first light generating device and a second light generating device. For instance, a subset of laser diodes of an array of laser diodes may be used as first light generating device, and its device light may at least partially follow another optical path than device light of another subset of laser diodes from that array (of laser diodes). Hence, in embodiments a single laser bank may be applied, of which the light is split in multiple portions, effectively providing multiple light generating devices. In general, this may imply the application of optics, allowing to divide the laser light of multiple subsets of lasers from the same bank into their respective (separate) beams of light that at least partially do not have identical optical paths (in the light generating system). The subsets may comprise one or more of the laser diodes of the laser bank. However, especially a single laser diode may only be comprised by a single subset. Notwithstanding such embodiments, of course also multiple laser banks may be used to provide multiple light generating devices.

[0018] In some embodiments, the one or more light generating devices may comprise a first light generating device (e.g. a first laser bank) and a discrete second light generating device (e.g. a second laser bank). In such embodiments, characteristics of the system light may be controllable through (i) individual control (or manipulation) of the (e.g. radiant flux) of the light generating devices, (ii) individual control (or manipulation) of light characteristics such as polarization of the device light generated by the respective light generating devices, and / or (iii) control (or configuration) of optical (beam splitting / combining) components downstream of the light generating devices, see also further below. Hence, such embodiments may provide controllability at the device, downstream of the device, and at the optics.

[0019] Additionally or alternatively, in some embodiments, the one or more light generating devices may comprise a (single) light generating device (e.g. a laser bank) comprising a multiple subsets of (solid state) light sources (e.g. a laser bank comprising a first subset of lasers and a second subset of lasers). In such embodiments, characteristics of the system light may be controllable through (i) individual control (or manipulation) of the (e.g. radiant flux) of the subsets of (solid state) light sources in the light generating device, (ii) individual control (or manipulation) of light characteristics such as polarization of the device light generated by the respective subsets of (solid state) light sources in the light generating device, and / or (iii) control (or configuration) of optical (beam splitting / combining) components downstream of the light generating device, see also further below. Hence, such embodiments may provide controllability at the device, downstream of the device, and at the optics.

[0020] Yet additionally or alternatively, in some embodiments, the one or more light generating devices may comprise a single light generating device (e.g. a laser bank). In such embodiments, characteristics of the system light may be controllable through (i) control (or manipulation) of light characteristics such as polarization of the device light generated by the light generating device, and / or (ii) control (or configuration) of optical (beam splitting / combining) components downstream of the light generating device, see also further below. Hence, such embodiments may provide controllability downstream of the device and at the optics.

[0021] It may also be possible to control subsets of lasers from a laser bank, like e.g. a laser bank comprising two or more strings of laser. Together with optics, it may be possible to provide two or mor individually controllable beams of light from a single laser bank.

[0022] However, it may also be possible to split laser light from a laser bank with optics in two (or more beams), e.g. with a (neutral) beam splitter, or with controllable polarization (as also described herein.

[0023] In embodiments the first light generating device may comprise a laser bank. In embodiments, wherein the optional second light generating device is applied, the second light generating device may comprise a laser bank. Each laser bank(s) described herein may comprise a plurality of diode laser (in an array).

[0024] Further, in embodiments, the first light generating device may especially be configured to generate first device light having a first centroid wavelength (Xci). Especially, in embodiments, the first device light may have a first centroid wavelength (Xci) selected from the wavelength range of 400-500 nm, such as from the range of 400-490 nm, especially from the range of 430-490 nm. Hence, in embodiments the first device light may have a peak emission wavelength selected from the wavelength range of 430-490 nm. In specific embodiments, the first device light may be blue light. For laser diodes, the peak emission wavelength and centroid wavelength may essentially be the same (difference may be less than 10 nm, such as less than about 5 nm, or may even essentially be zero). Yet, in specific embodiments the first device light may have a first centroid wavelength (Xci) selected from the wavelength range of 440-460 nm.

[0025] The term “centroid wavelength”, also indicated as , e.g., as Xci for the centroid wavelength of the first device light, 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 kc = X I(k) / (S I( A)), where the summation is over the wavelength range of interest, and I(k) 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.

[0026] Hence, in embodiments the first light generating device may comprise a solid- state light source selected from the group of diode lasers, superluminescent diodes, and multi -junction light emitting diodes, wherein the first light generating device is configured to generate first device light. Especially, the first light generating device may comprises a diode laser (or “laser diode” or “semi-conductor diode”). As indicated above, in embodiments the first light generating device may comprise a laser bank (comprising a plurality of diode lasers).

[0027] As indicated above, the first device light reaching the first depolarizing diffuser may comprise polarized light having a first linear polarization. Yet, the light generating system may be configured such that the first device light reaching the depolarizing diffuser comprises linear polarized light. Hence, the first device light may comprise linear polarized light and / or a polarizer may be configured downstream of the first light generating device and upstream of the depolarizing diffuser such that the first device light reaching the depolarizing diffuser may comprise linear polarized light. The term “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%. 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., polarizing 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).

[0028] The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”.

[0029] Therefore, in embodiments the first light generating device may be configured to provide first device light, wherein the first light generating device comprises a laser, and wherein the light generating system may be configured such that the first device light reaching the first depolarizing diffuser comprises polarized light having a first linear polarization (which may especially be s-polarization or p-polarization, see also below).

[0030] As indicated above, the system may especially be configured such that the first device light reaching the first depolarizing diffuser comprises linear polarized light, more especially, may be substantially linearly polarized, like elliptically polarized, or essentially linearly polarized light. However, to allow part of the device light propagate to the luminescent material (via the first polarizing beam splitter), and allow part of the device light propagate in the direction (via the first polarizing beam splitter), the first device light reaching the first polarizing beam splitter may especially comprise both linear polarized light of the s type and linear polarized light of the p-type.

[0031] Hence, especially the first depolarizing diffuser may be configured to convert at least part of the linearly polarized into depolarized light. The depolarized light may be separated by the first polarizing beam splitter into s-polarized light and p-polarized light. Hence, the application of the first depolarizing diffuser may lead to a redistribution of the polarizations. For instance, would light having only the first linear polarization reach the first depolarizing diffuser, a percentage of the light having the first linear polarization is converted into depolarized light, which will be separated by the first polarizing beam splitter into first linear polarized light (propagating in one direction) and second linear polarized light propagating in another direction (orthogonal to the one direction). The first depolarizing diffuser and the polarized device light reaching the first depolarizing diffuser may be configured such, i.e. the system may be configured such, that the first device light downstream of the first depolarizing diffuser has a predefined ratio of s-polarized light and p- polarized light. For instance, the ratio (on a power basis) may be selected between 0.005-0.35 or between 0.66-0.995, such as selected between 0.01-0.3 or between 0.7-0.99. The ratio as well as the choice of the first polarizing beam splitter may be selected such that a larger part of the first device light propagates to the luminescent material than in the direction of the light exit. Hence, the ratio of the spectral power of the first device light propagating to the luminescent material to the spectral power of the first device light propagating in the direction of the light exit may be selected from 0.66-0.995.

[0032] Further, the first depolarizing diffuser may be configured to diffuse the first device light. By diffusing the first device light, first device light that may escape from the system via the light exit may not be (essentially) coherent light, but may be diffused light. Hence, even when the first light generating device would be a high intensity light source, like a laser or a laser bank, the first device light escaping from the system may be safe as it is diffused light. Would for whatever reason the first depolarizing diffuser or the first polarizing beam splitter get damaged, then the chance that first device light escapes from the system may be very low, or essentially negligible. For instance, would the first depolarizing diffuser be damaged or broken, and would (a) the polarization of the device light reaching the first depolarizing diffuser, and (b) the first polarizing beam splitter be configured such that first device light essentially propagates to the luminescent material in the absence of the first depolarizing diffuser, then, would the first depolarizing diffuser be damaged or broken, essentially all first device light may propagate to the luminescent material and thus essentially not escape from the system.

[0033] Hence, especially (a) the polarization of the first device light reaching the first depolarizing diffuser, and (b) the first polarizing beam splitter may be configured such that the main linear polarization of the first device light (reaching the first depolarizing diffuser) may propagate via the first polarizing beam splitter to the luminescent material, whereas the less available (or absent) complementary polarization of the first device light reaching the first depolarizing diffuser may propagate via the first polarizing beam splitter in the direction of the light exit (of course unless the complementary polarization would be absent). Hence, would the first device light be elliptically polarized, the light with main axis polarization may propagate via the first polarizing beam splitter to the luminescent material, whereas the light with the minor axis polarization may propagate via the first polarizing beam splitter in the direction of the light exit.

[0034] Returning to the diffusing aspect of the first depolarizing diffuser, the diffusing action of the first depolarizing diffuser may lead to a broadening of the beam of first device light. Hence, in embodiments the first depolarizing diffuser may have a diffusion angle of at maximum 30°. The first depolarizing diffuser 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 smallangle transmissive diffusive material (e.g. a volume diffuser, textured surface diffuser, meta surface diffuser, etc.) 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 the first depolarizing diffuser may be realized by a stack of a small-angle transmissive diffuser and a specular mirror. Especially, the first depolarizing diffuser may comprise a first device light transmissive or reflective element comprising surface structures or a volumetric scatterer.

[0035] In embodiments, the first depolarizing diffuser may comprise an optical element comprising (i) scattering surface structures or (ii) a volumetric scatterer elements, or may comprise both scattering surface structures volumetric scatterer elements. The scattering structures may especially be scattering for the first device light. The scattering structures may e.g. comprise (small) indents, that may vary in shape along a surface of the optical element. Such optical element may be reflective or transmissive. The volumetric scattering elements may comprise (first device) light scattering particles, e.g. BaSCU, TiCh, ZrCh, boron nitride, ...), that may be embedded in an (inorganic) matrix (e.g. glass, ceramic, ...).

[0036] 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 first depolarizing diffuser 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°), such as at least about 2°, but at maximum about 30°, like selected from the range of about 2-30°, more especially selected from the range of 5-30°. Hence, in embodiments the first depolarizing diffuser has a diffusion angle selected from the range of 5-30°. A pencil light source may be configured to generate a (non-diffused) pencil beam, i.e. a collimated beam.

[0037] The first depolarizing diffuser may be a transmissive first depolarizing diffuser or a reflective first depolarizing diffuser. In specific embodiments, the first depolarizing diffuser comprises (more especially is) a transmissive first depolarizing diffuser.

[0038] Therefore, in embodiments the first depolarizing diffuser may be configured to diffuse at least part of the first device light and change at least part of the polarized light having the first linear polarization into unpolarized light. Especially, the first linear polarization and the second linear polarization are selected from s-polarization and p- polarization. In general the first depolarizing diffuser may be configured to change part of the polarized light having the first linear polarization into polarized light having a second linear polarization.

[0039] As indicated above, a (first) polarizing beam splitter may be applied.

[0040] A polarizing beam splitter may be considered an example of redirectional optics. Light propagating to the polarizing beam splitter, and comprising both linear polarizations, like elliptically polarized light, may be split in two orthogonally propagating beams of light with complementary linear polarizations. Hence, this provides the polarizing beam splitter its beam splitting function. However, the opposite may also be true: two beams of light with complementary linear polarizations orthogonally propagating to the polarizing beam splitter may be combined (by the polarizing beam splitter) in a single beam comprising both complementary linear polarizations and propagating along an axis parallel to an axis of one of the two beams of light with complementary linear polarizations orthogonally propagating to the polarizing beam splitter.

[0041] For the polarizing beam splitter may apply that for a first linear polarization, the transmission may be higher, like at least 10% points higher, such as at least 20% points higher, or even at least 30 % points, than for a second linear polarization. Similarly, for a first linear polarization, the reflection may be lower, like at least 10% points lower, such as at least 20% points lower, or even at least 30 % points, than for a second linear polarization. Especially, in embodiments, the polarizing beam splitter may be configured to direct at least 60%, like at least 80%, more especially at least 90%, such as at least about 95%, of the light of the first linear polarization to a first direction and at least 60%, like at least 80%, more especially at least 90%, such as at least about 95%, of the light of the second linear polarization to a second direction, wherein the directions may in embodiments have a mutual angle selected from the range 45-135°, such as about 90°. The percentage of the light may refer to a spectral power (e.g. in Watt). Especially, the first linear polarization and the second linear polarization may comprise linear polarizations such as selected from s polarization and p polarization. Optionally, device light comprising the first linear polarization and the second linear polarization may be selected from different elliptically polarized light (i.e. device light having s-polarization as the main axis or device light having p-polarization as the main axis). In embodiments, the polarizing beam splitters herein may be selected from reflective polarizing beam splitters (reflective polarizers).

[0042] Hence, in embodiments for the polarizing beam splitter may apply that for a s- polarization, the transmission may be higher, like at least 10% points higher, such as at least 20% points higher, or even at least 30 % points, than for p-polarization. Alternatively, in embodiments for the polarizing beam splitter may apply that for a p-polarization, the transmission may be higher, like at least 10% points higher, such as at least 20% points higher, or even at least 30 % points, than for s-polarization. Further embodiments are also described in the preceding paragraph.

[0043] Therefore, in embodiments the first polarizing beam splitter may be configured downstream of the first depolarizing diffuser and may be configured to direct first device light (received via the first depolarizing diffuser) in dependence of its linear polarization (a) in an optical path to the luminescent material or (b) in an optical path in a direction of the light exit.

[0044] Hence, in embodiments the first polarizing beam splitter may be configured to (a) transmit first device light being s-polarized in an optical path to the luminescent material and reflect first device light being p-polarized in an optical path to the light exit, or (b) transmit first device light being p-polarized in an optical path to the luminescent material and reflect first device light being s-polarized in an optical path to the light exit, or (c) reflect first device light being s-polarized in an optical path to the luminescent material and transmit first device light being p-polarized in an optical path to the light exit, or (d) reflect first device light being p-polarized in an optical path to the luminescent material and transmit first device light being s-polarized in an optical path to the light exit.

[0045] The system may especially configured such that (in an operational mode) (essentially all of) the first device light directed in an optical path to the luminescent material may also reach the luminescent material. However, in embodiments the system may also be configured that only part, or even no, first device light directed in an optical path to the light exit, indeed reaches the light exit and escapes from the system. These latter embodiments will further be elucidated below.

[0046] The light generating system may thus comprise a luminescent material, especially a luminescent element comprising a luminescent material. The luminescent material may be configured to convert light received by the luminescent material into luminescent material light. Especially, in embodiments, the luminescent element may comprise a first luminescent material configured to convert light received by the first luminescent material into first luminescent material light. The luminescent material may be configured to convert at least part of first radiation (selected from one or more of UV radiation and visible radiation), into luminescent material light. Especially, in embodiments, the luminescent material may be configured to convert at least part of first device light, such as blue light (as radiation), into luminescent material light. The first radiation may especially be provided by a (solid state) light source. Hence, in embodiments, the luminescent material may be configured to convert at least part of (combined) device light received by the luminescent material into luminescent material light. Especially, in embodiments, the luminescent material may be configured to convert at least 50%, such as at least 60%, like at least 70% of the (combined) device light received by the luminescent material (arrangement) into luminescent material light. Especially, in embodiments, the luminescent material may be configured to convert at least 80%, more especially at least 90%, including 100% of the (combined) device light received by the luminescent material (arrangement) into luminescent material light.

[0047] The phrase “... light received by ...”, and similar phrases, such as “device light received by the luminescent material” (or “ . . . by a polarizing beam splitter”, etc.) may especially indicate that when the light is actually received by the element, 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 element receives light may e.g. depend on e.g. a controlling mode (for instance whether or not a light generating device provides light).

[0048] 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. The term “luminescent material” especially refers to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and the 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 down-conversion. In specific embodiments, however the second radiation has a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up- conversion.

[0049] 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 (other) 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.

[0050] The term “luminescence” may herein also refer to phosphorescence and / or fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. In embodiments, the term “luminescent material” may herein also refer to a phosphorescent material and / or to a fluorescent material.

[0051] The term “luminescent material” may also refer to a plurality of different luminescent materials. 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. Examples of possible luminescent materials are indicated further below.

[0052] Hence, the luminescent material may in embodiments especially be configured to convert first device light received by the luminescent material into luminescent material light. Likewise, would a second device be applied, the luminescent material may in embodiments especially be configured to convert (also) second device light received by the luminescent material into luminescent material light. Whether or not first device light and / or second device light is received by the luminescent material may depend upon the (temporary) settings of the system during operation of the system. Phrases like “configured to convert first device light received by the luminescent material into luminescent material light”, and similar phrases, may indicate that at least part of the first device light received by the luminescent material is converted into luminescent material light. However, this does not exclude that some of the first device light received by the luminescent material may be reflected (e.g. due to scattering at the surface) and / or part of the first device light received by the luminescent material is not converted into luminescent material light, but converted into heat (e.g. due to Stokes losses).

[0053] 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. Especially, the luminescent material may be configured to convert at least part of the device light into luminescent material light, especially wherein the luminescent material comprises a (garnet) (first) luminescent material of the type AsEEOn 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%.

[0054] 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.

[0055] Hence, in specific embodiments the luminescent material comprises a (first) luminescent material of the type AsBsOn Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. 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, Sc, and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and / or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Yi-xLux)3B50i2:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Yi-xLux)3A150i2:Ce, part of Y and / or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Yo.iLuo.89Ceo.oi)3A150i2. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art.

[0056] In specific embodiments, the luminescent material may comprise at least two different luminescent materials configured to provide luminescent material light having different spectral power distributions. As can be derived from the above, the term “different luminescent materials” may refer to luminescent materials that are different, or to two compositions, each including at least one luminescent material in common, but wherein the compositions differ. For instance, a primary luminescent material comprising luminescent materials A and B, and a secondary luminescent material comprising only A or only B, or comprising both A and B, but in a different weight ratio. Such primary luminescent material and secondary luminescent material may have different spectral power distributions of their respective luminescent material light.

[0057] 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.

[0058] 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. As indicated above, other luminescent materials may also be possible. Hence, in specific embodiments the luminescent material may be selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures. Quantum structures may also comprise photonic crystals.

[0059] The luminescent material may be 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). 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 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.

[0060] In specific embodiments, the luminescent material may be configured to convert at least part of the first device light received by the luminescent material into luminescent material light having spectral power, especially its centroid wavelength, in the green-yellow wavelength range. Hence, the luminescent material may have spectral power at one or more wavelengths in the wavelength range of 490-590 nm, such as a centroid wavelength in this wavelength range.

[0061] The luminescent material may be configured in thermal contact with a thermally conductive material. Similarly, in some embodiments, the diffuser may be configured in thermal contact with a thermally conductive material. An element may be considered in “thermal contact” with another element if it can exchange energy through the process of heat. Hence, the elements may be thermally coupled. In embodiments, thermal contact can be achieved by physical contact. In embodiments, thermal contact may be achieved via a thermally conductive material, such as a thermally conductive glue (or thermally conductive adhesive). Thermal contact may also be achieved between two elements when the two elements are arranged relative to each other at a distance of equal to or less than about 10 pm, though larger distances, such as up to 100 pm may be possible. The shorter the distance, the better the thermal contact. Especially, the distance is 10 pm or less, such as 5 pm or less, such as 1 pm or less. The distance may be the distanced between two respective surfaces of the respective elements. The distance may be an average distance. In embodiments, the thermally conductive material may be comprised by and / or configured in thermal contact with one or more of a heatsink, a heat spreader, and a two-phase cooling device.

[0062] Another solution for the thermal management of the luminescent material may be to, in embodiments, apply (or mount) the (luminescent element especially the) luminescent material onto a rotating element, such as e.g. a rotating (phosphor-)wheel (or disk) or a rotating rod (or cylinder). Such embodiments may enable thermal spreading and cooling without the need for e.g. active water cooling, and thereby enabling maximum possible irradiance values. Hence, in embodiments, the luminescent material may be configured onto a rotating element. In embodiments, the rotating element may be thermally conductive.

[0063] As indicated above, especially the luminescent material may be configured to convert at least part of the first device light received via the first polarizing beam splitter into luminescent material light. The luminescent material light may have spectral power in the visible wavelength range; especially have a centroid wavelength in the visible wavelength range, such as within a wavelength range selected from 400-700 nm, and especially larger than the centroid wavelength of the first device light, such as in embodiments selected from the 510-750 nm wavelength range.

[0064] Having generated luminescent material light, it has to be guided to the light exit. To this end, (amongst others) a dichroic beam splitter may be applied.

[0065] Hence, in specific embodiments the light generating system may further comprise a dichroic element (herein also called “dichroic beam splitter”), that may be (a) configured to transmit or reflect the light from a light source, and / or (b) configured to reflect or transmit the luminescent material light (generated by the luminescent material e.g. due to conversion of the light from the light source). The dichroic element may be an embodiment of a color separation element, such as described in US7070300, which is herein incorporated by reference. Especially, the color separation element may be selected from the group of a dichroic mirror, a dichroic cube, and a diffractive optical element. Optionally, the color separation element maybe provided using a hologram. Especially, the dichroic element may be a dichroic mirror or reflector.

[0066] Hence, in a light generating system comprising a source of light, like a light generating device (e.g. comprising a solid state light source) that emits light having a first wavelength range along a first beam path, a wavelength converting element may be configured in the first beam path. Such wavelength converting element may in embodiments be physically separated from source of light. Further, such wavelength converting element may be configured to convert at least part of the light having a first wavelength range into light having a second wavelength range along a second beam path. Especially, in embodiments a color separation element, especially a dichroic element, may be disposed between the source of light and the wavelength converting element. In embodiments, the color separation element may be configured to prevent substantially all of the light having the second wavelength range from being incident on the source of light. Hence, such color separation element may in embodiments be configured to (a) transmit at least part of the light having the first wavelength range and reflect at least part of the light having the second wavelength range, or (b) reflect at least part of the light having the first wavelength range and transmit at least part of the light having the second wavelength range.

[0067] A dichroic beam splitter may be considered an example of redirectional optics (like polarization beam splitter, as described elsewhere herein). Light propagating to the dichroic beam splitter, and comprising intensity at different spectral positions, like light having a broad spectral power distribution, or light having different spectral peaks, or like light comprising a combination of first light having a first centroid wavelength and second light having a second centroid wavelength, different from the first centroid wavelength, etc., may be split in two orthogonally propagating beams of light with complementary linear polarizations. Hence, this provides the dichroic beam splitter its beam splitting function. However, the opposite may also be true, two beams of light with different spectral power distributions orthogonally propagating to the dichroic beam splitter may be combined in a single beam comprising both spectral power distributions and propagating along an axis parallel to an axis of one of the two beams of light with spectral power distributions orthogonally propagating to the dichroic beam splitter.

[0068] Hence, for the dichroic beam splitter may apply that for a first wavelength range, the wavelength averaged transmission may be higher, like at least 10% points higher, such as at least 20% points higher, or even at least 30 % points, than for a second wavelength range (different from the first wavelength range). Similarly, for a first wavelength range, the wavelength averaged reflection may be lower, like at least 10% points lower, such as at least 20% points lower, or even at least 30 % points, than for a second wavelength range. Especially, in embodiments, the dichroic beam splitter may be configured to direct at least 60%, like at least 80%, more especially at least 90%, such as at least about 95%, of (first) light having the first wavelength to a first direction and at least 60%, like at least 80%, more especially at least 90%, such as at least about 95%, of (second) light of the second wavelength to a second direction, wherein the directions may in embodiments have a mutual angle selected from the range 45-135°, such as about 90°. In embodiments, the first light may have a first centroid wavelength and the second light may have a second centroid wavelength, which may differ at least 5 nm, more especially at least about 10 nm. In embodiments the centroid wavelengths may differ at least about 15 nm. The percentage of the light may refer to a spectral power (e.g. in Watt). In embodiments the centroid wavelengths may differ at least about 20 nm.

[0069] Therefore, in specific embodiments the first dichroic beam splitter may be configured in an optical path between the first depolarizing diffuser and the luminescent material. Hence, the first dichroic beam splitter may be configured upstream of the luminescent material (relative to the propagation of the first device light). This may especially be the case when the luminescent material is configured in the reflective mode.

[0070] However, the luminescent material may also be configured in the transmissive mode. In such embodiments, the first dichroic beam splitter may be configured downstream of the luminescent material (relative to the propagation of the first device light). In such embodiments the first dichroic beam splitter may be configured in an optical path between the luminescent material and the light exit (such as in embodiments between the luminescent material and a second dichroic beam splitter, see also below).

[0071] Hence, in embodiments the luminescent material may be operated in the reflective mode, wherein the first dichroic beam splitter may be configured in an optical path between the first depolarizing diffuser and the luminescent material, whereas in other embodiments the luminescent material may be operated in the transmissive mode, wherein the first dichroic beam splitter may be configured in an optical path between the luminescent material and the light exit. Therefore, in embodiments one of the following may apply: (a) the luminescent material is operated in the transmissive mode, wherein the first dichroic beam splitter is configured downstream of the luminescent material, or (b) the luminescent material is operated in the reflective mode, wherein the first dichroic beam splitter is configured downstream of the first polarizing beam splitter and upstream of the luminescent material (with respect to the first device light propagating via the first dichroic beam splitter to the luminescent material).

[0072] In the transmissive mode, it may be chosen to have full conversion, i.e. essentially no first device light is transmitted through the luminescent material. In the reflective mode, a (specular) reflector may be configured downstream of the luminescent material.

[0073] When the first device light is at least partially converted by the luminescent material, diffused luminescent material light may be generated, which may not necessarily be (further) diffused. Note that the first device light received by the luminescent material is more diffuse than generated by the first light generating device due to the first depolarizing diffuser in an optical path from the first light generating device to the luminescent material.

[0074] Whether the transmissive or reflective mode is chosen, the first dichroic beam splitter may direct the luminescent material, received by the first dichroic beam splitter, in the direction of the light exit. The remaining first device light, if any, propagating along with the luminescent material light propagating to the first dichroic beam splitter, will not follow that optical path in the direction of the light exit, and will be transmitted or reflected in an orthogonal direction. Hence, especially, in embodiments the first dichroic beam splitter may be configured to receive luminescent material light from the luminescent material and direct (the luminescent material) in an optical path to the light exit.

[0075] Hence, in embodiments the first dichroic beam splitter may be configured to

[0076] (a) transmit at least part of the first device light in an optical path to the luminescent material and reflect at least part of the luminescent material light in an optical path to the light exit, or

[0077] (b) transmit first device light in an optical path to the luminescent material and reflect at least part of the luminescent material light in an optical path to the light exit.

[0078] Referring to both the first polarizing beam splitter and first dichroic beam splitter, in embodiments the following may apply: (A) the first polarizing beam splitter may be (a) transmissive for light having the first linear polarization and reflective for light having the second linear polarization, or (b) reflective for light having the first linear polarization and transmissive for light having the second linear polarization, and (B) the first dichroic beam splitter may be (i) transmissive for first device light and reflective for luminescent material light, or (ii) reflective for first device light and transmissive for luminescent material light.

[0079] In specific embodiments, the first polarizing beam splitter and / or first dichroic beam splitter are transmissive for the (diffused) first device light propagating to the luminescent material; this may be a relatively safe option. Hence, in embodiments the first polarizing beam splitter may be transmissive for light having the first linear polarization (e.g. s polarization) and reflective for light having the second linear polarization (e.g. p polarization). However, when the first dichroic beam splitter is configured downstream of the luminescent material (in the transmissive mode), the first dichroic beam splitter may be transmissive for luminescent material light and reflective for first device light.

[0080] Hence, from the system luminescent material light may escape via the light exit and optionally (diffused) first device light may (also) escape via the light exit. In this way, system light may escape from the system. Therefore, the light generating system may be configured to generate (in an operational mode of the light generating system) system light at least comprising the luminescent material light. Especially, the system may be configured such that in an operational mode of the light generating system, the system light comprises both diffused) first device light and luminescent material light. This may especially be dependent upon the extend of depolarization by the first depolarizing diffuser as well as whether or not measures are taken to influence the contribution of the (diffused) first device light to the system light (see also below).

[0081] The spectral power distribution of the system light may be preset, e.g. during production. For instance, the system light may be white light. Therefore, in embodiments in an operational mode of the light generating system the system light is white light comprising the luminescent material light and diffused first device light.

[0082] 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 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.

[0083] In embodiments, the white light may have a correlated color temperature selected from the range from 1800-10000 K, such as selected from the range of 2000-10000 K, and a color rendering index of at least 60, such as at least 65. In specific embodiments, the CRI may be at least 70.

[0084] 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.

[0085] In embodiments, the CRI may also be higher, such as at least about 75, like at least about 80.

[0086] However, the system light may also be colored light. Yet, the system light may in (other) embodiments have a controllable spectral power distribution, e.g. by the introduction of further optics and / or a further light generating device. Embodiments thereof will be described below.

[0087] 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.

[0088] 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.

[0089] Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

[0090] 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. The terms “operational mode” or "first operational mode”, and similar terms, may also refer to a plurality of (such) operational modes.

[0091] 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).

[0092] 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.

[0093] As indicated above, the luminescent material light may propagate in the direction of the light exit, and escape from the system via the light exit. The (diffused) first device light may also propagate in the direction of the light exit, and escape from the system via the light exit, unless (substantially) attenuated (see also below). In general, one or more redirectional elements may combine the diffused) first device light and the luminescent material light, and direct it in an optical path to the light exit. For instance, this may be a dichroic beam splitter (here thus effectively having the function of a beam combiner) or a polarizing beam splitter (here thus effectively having the function of a beam combiner). Especially, herein a dichroic beam splitter may be applied, or a combination of a dichroic beam splitter and a polarizing beam splitter, like an orthogonal configuration of a dichroic beam splitter and a polarizing beam splitter. Hence, in specific embodiments the first polarizing beam splitter and the first dichroic beam splitter may be configured in an orthogonal configuration.

[0094] Hence, in specific embodiments the light generating system may be configured such that at least part of the device light (i.e. the diffused first device light) directed by the first polarizing beam splitter in an optical path in the direction of the light exit and (b) at least part of the luminescent material light directed by the first dichroic beam splitter in an optical path to the light exit propagate colinear in the direction of the light exit. In general, the (diffused) first device light and the luminescent material light escaping from the system via the light exit may have at the light exit essentially parallel optical axes. Especially, the term “optical axis” may be defined as an imaginary line that defines the path along which light propagates through a system starting from the light generating element, here especially the light source. Especially, the optical axis may coincide with the direction of the light with the highest radiant flux.

[0095] Note that the luminescent material light may be diffused as such. Hence, the luminescent material light generated may not necessarily be (further) diffused, whereas the relatively coherent first device light used for excitation of the luminescent material and / or as contribution to the system light, may at least partially be diffused (see above).

[0096] As indicated above, it may be possible to control the contribution of the (diffused) first device light to the system light. For instance, a (controllable) color filter may be applied, which may e.g. be configured to transmit at least part of the luminescent material light, and block (by reflection or absorption) at least part of the (diffused) first device light. Another option may be the use of a reflective polarizer that is reflective for the (main) linear polarization of the (diffused) first device light propagating in the direction of the light exit, while being light transmissive for at least part of the luminescent material light. For instance, by rotation of the reflective polarizer, the contribution of the (diffused) first device light to the system light may be controlled. Therefore, in embodiments the light generating system may comprise a reflective polarizer configured upstream of the light exit and downstream of the first polarizing beam splitter , wherein the reflective polarizer may be transmissive for first device light having one of the linear polarizations and reflective for first device light having the other one of the linear polarizations. Further, in embodiments the system may also comprise a control system. Especially, in embodiments the control system may be configured to control a rotation of the reflective polarizer (and / or a movement or other way of controlling of a (controllable) color filter), wherein the control system may be configured to control a radiant flux of the first device light escaping from the light generating system via the first polarizing beam splitter by controlling the rotation of the reflective polarizer.

[0097] Other constructions as defined above may also be possible. For instance, the first polarizing beam splitter and the first dichroic beam splitter may not be configured at essentially the same position (though orthogonally). For instance, in such embodiments the beam of luminescent material light and the beam of (diffused) device light may have to be combined at another position. To this end, e.g. a second dichroic beam splitter may be applied. In such embodiments, one or more additional reflectors (or reflective elements) may be applied to direct the beams to the second dichroic beam splitter. Hence, in embodiments the light generating system may further comprise a specular reflective element and a second dichroic beam splitter (DBS2). Especially, the first polarizing beam splitter may in embodiments be configured to direct first device light in dependence of its linear polarization in an optical path in a direction of the light exit, wherein said optical path propagates via the second the second dichroic beam splitter (DBS2). Hence, in embodiments part of the first device light received by the first polarizing beam splitter may, when it comprises the first linear polarization, be directed in the direction of the light exit; such first device light may reach the second dichroic beam splitter , and then be directed in the direction of the light exit (and optionally escape from the system); first device light comprising the second linear polarization may be directed to the luminescent material. Alternatively, in embodiments part of the first device light received by the first polarizing beam splitter, may when it comprises the second linear polarization, be directed in the direction of the light exit; such first device light may reach the second dichroic beam splitter , and then be directed in the direction of the light exit (and optionally escape from the system); first device light comprising the first linear polarization may be directed to the luminescent material.

[0098] Further, in embodiments the first dichroic beam splitter may be configured to direct luminescent material light, received by the first dichroic beam splitter , in an optical path to the light exit, wherein said optical path propagates via the second dichroic beam splitter . Hence, luminescent material light received by the first dichroic beam splitter may be directed to the light exit, more especially to the second dichroic beam splitter ; luminescent material light received by the second dichroic beam splitter may (then) be directed to the light exit (and escape from the system).

[0099] Yet, in embodiments the specular reflective element may be configured upstream of the second dichroic beam splitter and downstream of one of the first polarizing beam splitter and the first dichroic beam splitter . For instance, the (diffused) first device light may propagate via the first polarizing beam splitter and the specular reflective element to the second dichroic beam splitter , or the luminescent material light may propagate via the first dichroic beam splitter and the specular reflective element to the second dichroic beam splitter . The terms “reflector” or “reflective element” may also refer to a plurality of reflectors.

[0100] It may be possible to use more than one depolarizing diffusers. This may increase the diffusion and / or may allow to less diffuse the first device light reaching the first polarizing beam splitter, and subsequently further diffused the (diffused) first device light that is directed by the first polarizing beam splitter in a direction of the light exit. It may also allow diffusing the first device light reaching the first polarizing beam splitter such that optimal polarization based splitting is possible by the first polarizing beam splitter and a subsequent further diffusing the (diffused) first device light that is directed by the first polarizing beam splitter in a direction of the light exit, in order to match the diffused beam with the bean of luminescent material light. Hence, in embodiments a second diffuser may be applied, upstream of the light exit but downstream of the first polarizing beam splitter. Therefore, in embodiments the light generating system may further comprise a second depolarizing diffuser configured downstream of the first polarizing beam splitter and upstream of the second dichroic beam splitter . Especially, in embodiments, the second depolarizing diffuser has 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°), such as at least about 2°, but at maximum about 30°, like selected from the range of about 2-30°, more especially selected from the range of 5-30°. Hence, in embodiments second depolarizing diffuser has a diffusion angle selected from the range of 5-30°.

[0101] Further, in specific embodiments a total diffusion angle of the first depolarizing diffuser and second depolarizing diffuser together may be selected from the range of 4-90°, more especially 5-60°, like 5-40°. This may be determined by using a pencil light source (see also above) and define the diffusion angle after having the light of the pencil source pass the first depolarizing diffuser and the second depolarizing diffuser. Hence, a second polarizing diffuser may further diffuse diffused light obtained from a first polarizing diffuser.

[0102] Another way to it control the contribution of the (diffused) first device light to the system light may be done by controlling the polarization of the first device reaching the first polarizing beam splitter. This may be done by rotating the first light generating device along the optical axis of the (beam of) first device light, especially when such device light comprises linear polarized light, such as essentially linear polarized light or elliptically polarized light having a dominant linear polarization (major axis), and control this rotation. Alternatively or additionally, this may be done by inserting a polarization rotator in the optical path of the first device light propagating to the depolarizing diffuser (or optionally in the optical path of the first device light propagating from the depolarizing diffuser to the first polarizing beam splitter), an control the rotation of the polarization rotator. Hence, the light generating system may further comprise a polarization control system.

[0103] In embodiments, the polarization control system may comprise a polarization rotator, especially a birefringent rotator (or especially a Faraday rotator). The term “birefringent rotator” may herein refer to an element having a refractive index that may depend on the polarization of light incident on the birefringent rotator, i.e., the element may be characterized by two perpendicular optical axes in the plane of the element, with different refractive indices for perpendicularly incoming light with polarizations along these respective axes. In embodiments, through rotation of the birefringent rotator, and thus the rotation of the orientation of the optical axis of the birefringent rotator in a plane perpendicular to the optical axis of the incident light, relative to the plane of (linear) polarization of the incident light the linear polarization of that light may be changed. As such, in embodiments, the birefringent rotator may be configured to receive the device light emitted by the first light generating device and may be configured to adjust (or control) the polarization of the device light, such that the (combined) first (and / or optional third) device light having a predetermined (linear) polarization will be provided to the central redirection optics (CBS). Especially, in embodiments, the polarization control system may be configured to control rotation of the birefringent rotator, such that the polarization of the device light reaching the central redirection optics (CBS) is adjusted. The birefringent rotator may therefore, in embodiments, comprise a X / 2 waveplate, wherein the wavelength ‘X’ refers to a representative wavelength of the incoming beam of the device light, with which, upon rotation about the optical axis (of the birefringent rotator), the polarization of the incoming (linearly polarized) beam of device light can be rotated by any angle. In embodiments, with a X / 2 waveplate configured in an optical path between (a) the first (and / or optional third) light generating device(s) and (b) the central redirection optics (CBS), a linearly polarized beam of device light may thus be adjusted such that a beam of device light comprising any ratio of p / (s+p) and s / (s+p) may be provided to the central redirection optics (CBS), wherein ‘p’ refers to the p-polarized fraction and ‘s’ refers to the s-polarized fraction relative to a splitting (transmitting vs reflecting) plane of the central redirection optics (CBS). Hence, in embodiments, the polarization rotator may comprise a birefringent rotator, wherein the birefringent rotator comprises a X / 2 waveplate, and wherein the polarization control system is configured to control rotation of the birefringent rotator. Especially, the control system may be configured to control the spectral power distribution of the system light by controlling the rotation of the birefringent rotator (by controlling the polarization control system).

[0104] Instead of a birefringent rotator, another optical retarder, providing a defined phase shift between the polarization components projected along the fast and slow axes of birefringent material may be used.

[0105] For a X / 4 phase shift, herein a zero-order waveplate may be applied. A same effect can be achieved with multiple order waveplates (integer+X / 4 phase shift). Fresnel rhomb retarders may be also used to result in lambda / 4 phase shift. Faraday rotators are typically used to rotate direction of linear polarized light as well. Finally, metamaterials or metasurfaces, comprising geometric and repeating sub -wavelength structures can be designed to provide quarter wave retardation as well. Likewise, for X / 2 waveplate alternatives may be applied.

[0106] The polarization of the device light received by the first polarization redirection optics may further be controlled by controlling an orientation of the light generating devices, especially by controlling an orientation of the first light generating device light generating device. Hence, in embodiments, the control system, may be configured to control a (rotational) orientation of the first light generating device relative to an optical axis of the (beam of light) directed to the first polarizing beam splitter, especially a rotational orientation around a (first) optical axis of the first device light.

[0107] Hence, in embodiments the polarization control system may comprise a polarization rotator configured downstream of the first light generating device and upstream of the first polarizing beam splitter, wherein the control system may be configured to control the spectral power distribution of the system light by controlling (a rotation of) the polarization rotator, wherein the polarization rotator may especially comprise a birefringent rotator, wherein the birefringent rotator may comprise a X / 2 waveplate. Especially, the polarization control system may be configured to control rotation of the birefringent rotator (and the control system may control the polarization control system).

[0108] Another way, which may be chosen to (further) control the spectral power distribution of the system light is to include device light of a second light generating device.

[0109] For the second light generating device may apply essentially the same embodiments as described above in relation to the first light generating device, though the second device light may have (but not necessarily has) a spectral power distribution different from the spectral power distribution of the first device light. Hence, in embodiments the second light generating device may comprise a solid-state light source selected from the group of diode lasers, superluminescent diodes, and multi -junction light emitting diodes, wherein the second light generating device is configured to generate second device light. Especially, the second light generating device (may comprises a diode laser (or “laser diode” or “semi-conductor diode”). Further, in embodiments the second light generating device may comprise a laser bank (comprising a plurality of diode lasers).

[0110] Note that an array of solid state light sources, such as provided by a laser bank, may provide multiple light generating devices, such as a first light generating device and a second light generating device. For instance, a subset of laser diodes of an array of laser diodes may be used as first light generating device, and its device light may at least partially follow another optical path than device light of another subset of laser diodes from that array (of laser diodes). Hence, in embodiments a single laser bank may be applied, of which the light is split in multiple portions, effectively providing multiple light generating devices. In general, this may imply the application of optics, allowing to divide the laser light of multiple subsets of lasers from the same bank into their respective (separate) beams of light that at least partially do not have identical optical paths (in the light generating system). The subsets may comprise one or more of the laser diodes of the laser bank. However, especially a single laser diode may only be comprised by a single subset. Notwithstanding such embodiments, of course also multiple laser banks may be used to provide multiple light generating devices. Hence, in embodiments the first light generating device may comprise a first laser bank and the second light generating device may comprise a second laser bank.

[0111] Such second device light may be introduced as such, and end up in the system light. In such embodiments, the second device light may also have to be diffused. Hence, either the existing diffuser(s) may be applied, or one or more additional diffusers may be applied. However, when the second device light is at least partially converted by the luminescent material, diffused luminescent material light may be generated, which may not necessarily be (further) diffused. Here below, embodiments are described wherein the second device light is also at least partially converted by the luminescent material.

[0112] Would the second device light also at least partially be converted by the luminescent material, then the second device light may in embodiments have a peak wavelength similar to peak wavelength of the first device light. Anyhow, they may desirably in a wavelength range where the luminescent material is well excitable. When adding the second device light to the first device light that is propagating in the direction of the luminescent material, dichroic combining or polarization combining may be applied. Would the second device light be introduced in the system upstream of the first polarizing beam splitter, dichroic combining may be desirable, especially when the first device light and second device light reaching the first polarizing beam splitter comprise light having the same linear polarization. Would the second device light be introduced in the system downstream of the first polarizing beam splitter, dichroic combining or polarization combining may be applied. However, for dichroic combining, the peak wavelengths of the first device light and second device light may especially be different, like differing at least about 5 nm, such as at least about 10 nm. In other embodiments, for dichroic combining, the peak wavelengths of the first device light and second device light may be selected to differ at least 15 nm.

[0113] Therefore, in (specific) embodiments the light generating system may further comprise a (i) a second light generating device and (ii) a redirectional optical element. Especially, the second light generating device may be configured to provide second device light. In specific embodiments, the second light generating device may comprise a (diode) laser. Further, in embodiments the redirectional optical element may comprise one or more of a second polarizing beam splitter (PBS2) and a third dichroic beam splitter. In embodiments, the redirectional optical element may be configured (a) upstream of the first polarizing beam splitter or (b) downstream of the first polarizing beam splitter and upstream of the luminescent material. Yet, in embodiments the second light generating device may be configured upstream of the redirectional optical element. Further, in embodiments the following may apply: when (a) the first device light and the second device light have peak wavelengths differing less than x nm, the redirectional optical element may comprise the second polarizing beam splitter (PBS2), and when (b) the first device light and the second device light have peak wavelengths differing at least x nm, the redirectional optical element may comprise the second polarizing beam splitter (PBS2) or the third dichroic beam splitter. Especially, in embodiments x may be selected from the range of 2-10 nm.

[0114] In embodiments, the first device light and the second device light may have peak wavelengths differing at least 10 nm, such as in specific embodiments at least 15 nm; in such embodiments the redirectional optical element may comprise the second polarizing beam splitter or the third dichroic beam splitter. Yet, in embodiments the first device light and the second device light may have peak wavelengths differing less than 15 nm, such as in specific embodiments at maximum 10 nm; in such embodiments the redirect! onal optical element may comprise the second polarizing beam splitter.

[0115] In specific embodiments, the redirectional optical element may be configured (a) upstream of the first polarizing beam splitter , and the second light generating device may be configured to generate one or more of green, yellow, orange, and red second device light. Further, the light generating system may be configured such that the second device light reaching the first depolarizing diffuser (also) comprises polarized light having the first linear polarization. In embodiments, alternatively, the redirectional optical element may be configured downstream of the first polarizing beam splitter and upstream of the luminescent material, the second light generating device may be configured to generate second device light; wherein the first device light and the second device light may have peak wavelengths differing at most 50 nm, and wherein the luminescent material may be configured to convert at least part of the second device light received by the luminescent material into luminescent material light.

[0116] When both a first light generating device and a second light generating device is applied, the control system may further be configured to control the radiant fluxes of the first light generating device and the second light generating device. This may in embodiments allow a further control of the spectral power distribution of the system light.

[0117] In embodiments, the system may comprise a light exit, like an end window or an (other) optical element, 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.

[0118] Optics other than described herein may also be applied, as will be clear to a person skilled in the art. The term “optics” may especially refer to (one or more) optical elements. Hence, the terms “optics” and “optical elements” may refer to the same items. The optics may include one or more or mirrors, reflectors, collimators, lenses, prisms, diffusers, phase plates, polarizers, diffractive elements, gratings, dichroics, arrays of one or more of the afore-mentioned, etc. Alternatively or additionally, the term “optics” may refer to a holographic element or a mixing rod. In embodiments, the optics may include one or more of beam expander optics and zoom lens optics. See also herein for examples of optics.

[0119] Phrase like “in embodiments the first polarizing beam splitter may be configured downstream of the first depolarizing diffuser and may be configured to direct the first device light in an optical path ....”, and similar phrases, may especially indicate that at least part of the first device light received by the first polarizing beam splitter may be directed in an optical path. Hence, phrases like “....an element configured to direct a type of light to another optical element or in an optical path to ...”, and similar phrases, may especially indicated that at least part of the light of the type of light received by the element may be directed to the other optical element or in the optical path to...

[0120] In embodiments, the light generating system is configured to generate in an operational mode of the light generating system, system light at least comprising luminescent material light and at least part of the first device light. However, in the same or other embodiments of the light generating system, in another operational mode of the light generating system, the system light may comprise luminescent material light only. Dependent upon the controllability of the light generating device (preset during production or control means like rotation of the light source, controllable optical filters, etc., see also above), the contribution of the luminescent material light and the first device light, and optionally the second device light, may be controlled.

[0121] Note that the first device light received at the first polarizing beam splitter may thus in embodiments be more diffused than the first device light received by the first depolarizing diffuser. Unless a further diffuser is applied, like the second depolarizing diffuser, the first device light that may escape from the system may in embodiments have (essentially) the same diffusion as the first device light downstream of the first depolarizing diffuser. Hence, in embodiments the beam angle defined by the full width half maximum of a beam of first device light received by the first depolarizing diffuser may be smaller than such beam angle of a beam of first device light downstream of the first depolarizing diffuser. Would in embodiments a second depolarizing diffuser, the beam angle defined by the full width half maximum of a beam of first device light received by the second depolarizing diffuser may be smaller than such beam angle of a beam of first device light downstream of the second depolarizing diffuser.

[0122] 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.

[0123] 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. The terms “violet light” or “violet emission”, and similar terms, may especially relate to light having a wavelength in the range of about 380-440 nm. In specific embodiments, the violet light may have a centroid wavelength in the 380-440 nm range. The terms “blue light” or “blue emission”, and similar terms, may especially relate to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues). In specific embodiments, the blue light may have a centroid wavelength in the 440-490 nm range. The terms “green light” or “green emission”, and similar terms, may especially relate to light having a wavelength in the range of about 490-560 nm. In specific embodiments, the green light may have a centroid wavelength in the 490-560 nm range. The terms “yellow light” or “yellow emission”, and similar terms, may especially relate to light having a wavelength in the range of about 560-590 nm. In specific embodiments, the yellow light may have a centroid wavelength in the 560-590 nm range. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590-620 nm. In specific embodiments, the orange light may have a centroid wavelength in the 590-620 nm range. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-750 nm. In specific embodiments, the red light may have a centroid wavelength in the 620-750 nm range. The terms “cyan light” or “cyan emission”, and similar terms, especially relate to light having a wavelength in the range of about 490-520 nm. In specific embodiments, the cyan light may have a centroid wavelength in the 490-520 nm range. The terms “amber light” or “amber emission”, and similar terms, may especially relate to light having a wavelength in the range of about 585-605 nm, such as about 590-600 nm. In specific embodiments, the amber light may have a centroid wavelength in the 585-605 nm range. The phrase “light having one or more wavelengths in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least intensity or intensities at these one or more wavelengths in the indicate wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at one or more wavelengths in the 440-490 nm wavelength range.

[0124] In yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a lighting device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system as defined herein. In an aspect the invention also provides a lighting device selected from the group of an automotive headlamp and a search light, 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 depolarizing diffuser, the first polarizing beam splitter, the first dichroic beam splitter, the luminescent material, etc.

[0125] BRIEF DESCRIPTION OF THE DRAWINGS

[0126] 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:

[0127] Figs, la-ld schematically depict some embodiments and

[0128] Fig. 2 schematically depicts application embodiments. The schematic drawings are not necessarily to scale.

[0129] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0130] Figs, la-ld schematically depicts embodiments of a light generating system 1000 comprising a first light generating device 110, a first depolarizing diffuser 410, a first polarizing beam splitter PBS1, a first dichroic beam splitter DBS1, a luminescent material 200, and a light exit 1090.

[0131] The first light generating device 110 may be configured to provide first device light 111. The first light generating device 110 may comprise a laser light source. Especially, the light generating system 1000 may be configured such that the first device light 111 reaching the first depolarizing diffuser 410 may comprise polarized light having a first linear polarization. For instance, the first device light of a laser light source may be linearly polarized. In embodiments, the first device light 111 may have a peak emission wavelength selected from the wavelength range of 430-490 nm.

[0132] The first depolarizing diffuser 410 may be configured to diffuse at least part of the first device light 111 and change at least part of the polarized light having the first linear polarization into unpolarized light. Further, the first polarizing beam splitter PBS1 may be configured downstream of the first depolarizing diffuser 410 and may be configured to direct first device light 111 in dependence of its linear polarization (a) in an optical path to the luminescent material 200 or (b) in an optical path in a direction of the light exit 1090. Whether or not the first device light reaches the light exit (via the first polarizing beam splitter PBS1) may depend upon the optional presence of a reflective diffuser 430 and its position. As this optical element is option, it is indicated dashed. Note such optical element may also be present in the other embodiments, though not (always) depicted.

[0133] Hence, in embodiments the system may comprise a reflective polarizer 430 configured upstream of the light exit 1090 and downstream of the first polarizing beam splitter PBS1. Especially, the reflective polarizer 430 may be transmissive for first device light 111 having one of the linear polarizations and reflective for first device light having the other one of the linear polarizations. Further, a control system 300 may be configured to control a rotation of the reflective polarizer 430, wherein the control system 300 may be configured to control a radiant flux of the first device light 111 escaping from the light generating system 1000 via the first polarizing beam splitter PBS1 by controlling the rotation of the reflective polarizer 430. Note that the control system may alternatively or additionally also be used for other purposes, like control of the radiant flux of the first device light, (optional) control of the radiant flux of the optional second device light, and optional control of other aspects, like rotation of the first light generating device about its optical axis and / or rotation of an optional birefringent rotator (see further also below). The luminescent material 200 may be configured to convert at least part of the first device light 111 received via the first polarizing beam splitter PBS1 into luminescent material light 201. Further, the first dichroic beam splitter DBS1 may be configured to receive luminescent material light 201 from the luminescent material 200 and direct (the luminescent material light 201 received by the first dichroic beam splitter DBS1) in an optical path to the light exit 1090.

[0134] Especially, the light generating system 1000 may be configured to generate (in an operational mode of the light generating system 1000) system light 1001 at least comprising the luminescent material light 201.

[0135] In embodiments, the luminescent material 200 may be operated in the reflective mode (see Figs, la-lc). Especially then, the first dichroic beam splitter DBS1 may be configured in an optical path between the first depolarizing diffuser 410 and the luminescent material 200.

[0136] However, in other embodiments the luminescent material 200 may be operated in the transmissive mode (see Fig. Id). Especially, in such embodiments the first dichroic beam splitter DBS1 may be configured in an optical path between the luminescent material 200 and the light exit 1090.

[0137] In embodiments, the first light generating device 110 may comprise a laser bank comprising a plurality of diode laser.

[0138] Further, in embodiments the light generating system 1000 may be configured such that at least part of the device light 111 directed by the first polarizing beam splitter PBS1 in an optical path in the direction of the light exit 1090 and (b) at least part of the luminescent material light directed by the first dichroic beam splitter DBS1 in an optical path to the light exit 1090 propagate colinear in the direction of the light exit 1090.

[0139] Especially, in an operational mode of the light generating system 1000 the system light 1001 is white light comprising the luminescent material light 201 and diffused first device light 111. In specific embodiments, the white light may have a correlated color temperature selected from the range from 2000-10000 K and a color rendering index of at least 65.

[0140] Especially, the luminescent material 200 at least may comprise a luminescent material of the type AsBsOn Ce, wherein A may comprise one or more of Y, La, Gd, Tb and Lu, and wherein B may comprise one or more of Al, Ga, In and Sc.

[0141] In embodiments, the first depolarizing diffuser 410 may comprise a transmissive first depolarizing diffuser 410. Especially, the first depolarizing diffuser 410 may have a diffusion angle selected from the range of 5-30°. In embodiments, the first depolarizing diffuser 410 may comprise (i) a first device light transmissive or reflective element comprising surface structures or (ii) a volumetric scatterer.

[0142] As schematically depicted in Fig. la, the first polarizing beam splitter PBS1 and the first dichroic beam splitter DBS1 are configured in an orthogonal configuration.

[0143] Referring to Figs, la-ld, in embodiments the first polarizing beam splitter PBS1 may be (a) transmissive for light having the first linear polarization and reflective for device light having the second linear polarization, or (b) reflective for light having the first linear polarization and transmissive for light having the second linear polarization. Referring to Figs, la-ld, in embodiments the first dichroic beam splitter DBS1 may be (i) transmissive for first device light 111 and reflective for luminescent material light 201, or (ii) reflective for first device light 111 and transmissive for luminescent material light 201.

[0144] Referring to Figs, la-ld, in embodiments the first polarizing beam splitter PBS1 may be transmissive for light having the first linear polarization and reflective for light having the second linear polarization.

[0145] Referring to Figs, lb and Id, in embodiments the light generating system 1000 may further comprise a specular reflective element 440 and a second dichroic beam splitter DBS2. In embodiments, the first polarizing beam splitter PBS1 may be configured to direct first device light 111 in dependence of its linear polarization in an optical path in a direction of the light exit 1090 wherein said optical path propagates via the second dichroic beam splitter DBS2. Further, in embodiments, the first dichroic beam splitter DBS1 may be configured to direct luminescent material light 201, received by the first dichroic beam splitter DBS1, in an optical path to the light exit 1090, wherein said optical path propagates via the second dichroic beam splitter DBS2. Especially, in embodiments one of the following may apply: (a) the luminescent material 200 is operated in the transmissive mode, wherein the first dichroic beam splitter DBS1 may be configured downstream of the luminescent material 200, or (b) the luminescent material 200 is operated in the reflective mode, wherein the first dichroic beam splitter DBS1 may be configured downstream of the first polarizing beam splitter and upstream of the luminescent material 200. Further, especially the specular reflective element 440 may be configured upstream of the second dichroic beam splitter DBS2 and downstream of one of the first polarizing beam splitter PBS1 and the first dichroic beam splitter DBS1.

[0146] Referring also to Figs, lb and Id, optionally the system 1000 may further comprise a second depolarizing diffuser 420 configured downstream of the first polarizing beam splitter PBS1 and upstream of the second dichroic beam splitter DBS2. Especially, the second depolarizing diffuser 420 may have a diffusion angle selected from the range of 5- 30°.

[0147] Referring to Fig. 1c, the light generating system 1000 may further comprising a (i) a second light generating device 120 and (ii) a (further) redirect! onal optical element 505. Note that this embodiments is only depicted in the embodiment of Fig. 1c, which is in fact the same as the schematically depicted embodiment of Fig. la, but that this embodiment or variant of the additional light generating device may also be applied in the embodiments schematically depicted in Figs, lb and Id, or other embodiments described herein.

[0148] The second light generating device 120 may be configured to provide second device light 121. Especially, the second light generating device 120 may comprise a laser light source.

[0149] Further, in embodiments the redirectional optical element 505 may comprise one or more of a second polarizing beam splitter PBS2 (as schematically depicted) and a third dichroic beam splitter (depicted with the dashed option; the related reference numbers are also indicated with ‘). Especially, the redirectional optical element 505 may be configured (a) upstream of the first polarizing beam splitter PBS1 (depicted with the dashed option; the related reference numbers are also indicated with ‘) or (b) downstream of the first polarizing beam splitter PBS1 and upstream of the luminescent material 200 (depicted in Fig. lb). Other options may also be possible, though at least some of these may imply an additional diffuser.

[0150] Fig. 1c schematically depicts two options, which may also be applied both. Especially, the second light generating device 120 may be configured upstream of the redirectional optical element 505. With the second light generating device 120, second device light 121 may be introduced in the system 1000 that may excite the luminescent material as well, and will thus at least partly be converted, or may be introduced as such and may at least partially be comprised in the system light (in one or more operational modes). Would for instance two second light generating devices be applied, then the second device light 121 of these two second light generating devices may differ, e.g. at least 10 nm.

[0151] In embodiments, when (a) the first device light 111 and the second device light 121 have peak wavelengths differing less than x nm, the redirectional optical element 505 may comprise the second polarizing beam splitter PBS2, and when (b) the first device light 111 and the second device light 121 have peak wavelengths differing at least x nm, the redirectional optical element 505 may comprise the second polarizing beam splitter PBS2 or the third dichroic beam splitter. Especially, this may apply when x is selected from the range of 2-10 nm.

[0152] Hence, in embodiments the second light generating device 120 may provide a second device light 121 comprising a different polarization than the first device light 111 reaching the luminescent material 200. In such embodiments, a polarizing beam splitter (or beam combiner) may be needed. However, when in other embodiments the first device light 111 and the second device light 121 have (substantial) different peak wavelengths, they may be combined via a dichroic beam splitter (or beam combiner).

[0153] Referring to Fig. 1c, the second light generating device 120’ (left in the drawing), in embodiments the redirectional optical element 505 (i.e. here also indicated with reference 505’) may be configured upstream of the first polarizing beam splitter PBS1, and the second light generating device 120 (i.e. here also indicated in Fig. 1c with reference 120’) may be configured to generate one or more of green, yellow, orange, and red second device light 121 (here also indicated with reference 121’), especially one or more of , orange, and red second device light 121. Further, in embodiments the light generating system 1000 may be configured such that the second device light 121 reaching the first depolarizing diffuser 410 (also) may comprise polarized light having the first linear polarization. However, the complementary linear polarization, i.e. the second linear polarization may also be possible.

[0154] Referring to Fig. 1c, the second light generating device 120 (right in the drawing), in embodiments the redirectional optical element 505 may be configured downstream of the first polarizing beam splitter PBS1 and upstream of the luminescent material 200. Especially, in such embodiments the second light generating device 120 may be configured to generate second device light 121, wherein the first device light 111 and the second device light 121 may have peak wavelengths differing at most 50 nm. Further, in embodiments the luminescent material 200 may be configured to convert at least part of the second device light 121 received by the luminescent material 200 into luminescent material light 201. Hence, the difference in peak wavelength may be chosen such that dichroic beam combining is possible, and both peak wavelengths may excite at wavelengths where the luminescent material 200 is relatively well excitable (like e.g. at least 10 nm, such as at least about 15 nm).

[0155] Fig. Id is essentially the same embodiments as Fig. lb, but now with the luminescent material 200 in the transmissive mode, as also discussed above. Hence, as indicated above in embodiments, the first dichroic beam splitter DBS1 may be configured to direct luminescent material light 201, received by the first dichroic beam splitter DBS1, in an optical path to the light exit 1090, wherein said optical path propagates via the second dichroic beam splitter DBS2. Hence, the second dichroic beam splitter DBS2 may be configured upstream of the light exit 1090 and downstream of the luminescent material 200. Therefore, the luminescent material light 201 may in such embodiments propagate in an optical path from the luminescent material 200 via the first dichroic beam splitter DBS1 and (subsequently) via the second dichroic beam splitter DBS2 to the light exit 1090.

[0156] Further, the second dichroic beam splitter DBS2 may be configured downstream of the first polarizing beam splitter PBS1.

[0157] Optionally, the reflective polarizer 430 may be applied to further control the spectral power distribution of the system light 1001.

[0158] Fig. Id schematically depict some further embodiments that may also apply to the other embodiments described herein and / or schematically depicted in Figs, la-lc, visually the polarization control by rotation of the first light generating device 110 via the optical axis of the first device light 111 received by the first depolarizing diffuser 410. Alternatively or additionally, a birefringent rotation 650 may be rotated, when positioned downstream of the first light generating device 110 and upstream of the first depolarizing diffuser 410. A movement device 630 (such as an (rotary) actuator) may control a rotation of one or more of the first light generating device 110 and the optional birefringent rotator 650. Especially, the birefringent rotator may comprise a X / 2 plate.

[0159] Reference 600 refers to a polarization control system comprising the movement of device 630 and one or more of a rotatable first light generating device 110 and a birefringent rotator 650. The control system 300 may control the polarization control system 600.

[0160] Note that for the luminescent material 200 in the transmissive mode, it may be chosen to have full conversion, i.e. essentially no first device light I l l is transmitted through the luminescent material. The dashed line right of the luminescent material 200 indicates the possible presence of first device light 111, which may anyhow be filtered out from the beam of luminescent material light 201 in the optical path to the light exit 1090 by the first dichroic beam splitter DBS1.

[0161] Note that the control system 300 may alternatively or additionally also be used for other purposes, like control of the radiant flux of the first device light, (optional) control of the radiant flux of the optional second device light, and optional control of other aspects, like rotation of the first light generating device about its optical axis and / or rotation of an optional birefringent rotator (see further also below). Fig. 2 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. 2 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig. 2 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. Note that the invention may also provide a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, an automotive headlamp, and a search light, comprising the light generating system 1000 as defined herein.

[0162] The term “plurality” refers to two or more. The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’. The term “and / or” especially relates to one or more of the items mentioned before and after “and / or”. For instance, a phrase “item 1 and / or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0163] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0164] 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.

[0165] 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.

[0166] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0167] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method as described herein.

[0168] 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.

[0169] The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and / or shown in the attached drawings.

[0170] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. A light generating system (1000) comprising a first light generating device(110), a first depolarizing diffuser ( 10), a first polarizing beam splitter (PBS1), a first dichroic beam splitter (DBS1), a luminescent material (200), and a light exit (1090); wherein: the first light generating device (110) is configured to provide first device light(111), wherein the first light generating device (110) comprises a laser light source; the light generating system (1000) is configured such that the first device light (111) reaching the first depolarizing diffuser (410) comprises polarized light having a first linear polarization; the first depolarizing diffuser (410) is configured to diffuse at least part of the first device light (111) and change at least part of the polarized light having the first linear polarization into unpolarized light; the first polarizing beam splitter (PBS1) is configured downstream of the first depolarizing diffuser (410) and is configured to direct the first device light (111) in dependence of its linear polarization (a) in an optical path to the luminescent material (200) or (b) in an optical path in a direction of the light exit (1090); the luminescent material (200) is configured to convert at least part of the first device light (111) received via the first polarizing beam splitter (PBS1) into luminescent material light (201); the first dichroic beam splitter (DBS1) is configured to receive luminescent material light (201) from the luminescent material (200) and to direct the luminescent material light (201) in an optical path to the light exit (1090); and the light generating system (1000) is configured to generate in an operational mode of the light generating system (1000) system light (1001) at least comprising luminescent material light (201) and at least part of the first device light (111).

2. The light generating system (1000) according to claim 1, wherein the luminescent material (200) is operated in the reflective mode, and wherein the first dichroic beam splitter (DBS1) is configured in an optical path between the first depolarizing diffuser (410) and the luminescent material (200).

3. The light generating system (1000) according to claim 1, wherein the luminescent material (200) is operated in the transmissive mode, and wherein the first dichroic beam splitter (DBS1) is configured in an optical path between the luminescent material (200) and the light exit (1090).

4. The light generating system (1000) according to claim 1, wherein the first light generating device (110) comprises a laser bank comprising a plurality of laser diodes, wherein the light generating system (1000) is configured such that at least part of the device light (111) directed by the first polarizing beam splitter (PBS1) in an optical path in the direction of the light exit (1090) and (b) at least part of the luminescent material light directed by the first dichroic beam splitter (DBS1) in an optical path to the light exit (1090) propagate colinear in the direction of the light exit (1090); wherein in an operational mode of the light generating system (1000) the system light (1001) is white light comprising the luminescent material light (201) and diffused first device light (111); wherein the white light has a correlated color temperature selected from the range from 2000-10000 K and a color rendering index of at least 65; wherein the first device light (111) has a peak emission wavelength selected from the wavelength range of 430-490 nm, and wherein the luminescent material at least comprises a luminescent material of the type AsBsO Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc.

5. The light generating system (1000) according to any one of the preceding claims, wherein the first depolarizing diffuser (410) comprises a transmissive first depolarizing diffuser (410); and wherein the first depolarizing diffuser (410) has a diffusion angle selected from the range of 5-30°.

6. The light generating system (1000) according to any one of the preceding claims, wherein the first polarizing beam splitter (PBS1) and the first dichroic beam splitter (DBS1) are configured in an orthogonal configuration.

7. The light generating system (1000) according to any one of the preceding claims, wherein (A) the first polarizing beam splitter (PBS1) is (a) transmissive for light having the first linear polarization and reflective for device light having the second linear polarization, or (b) reflective for light having the first linear polarization and transmissive forlight having the second linear polarization; and wherein (B) the first dichroic beam splitter (DBS1) is (i) transmissive for first device light (111) and reflective for luminescent material light (201), or (ii) reflective for first device light (111) and transmissive for luminescent material light (201).

8. The light generating system (1000) according to claim 7, wherein the first polarizing beam splitter (PBS1) is transmissive for light having the first linear polarization and reflective for light having the second linear polarization.

9. The light generating system (1000) according to any one of the preceding claims, further comprising: a reflective polarizer (430) configured upstream of the light exit (1090) and downstream of the first polarizing beam splitter (PBS1); wherein the reflective polarizer (430) is transmissive for first device light (111) having one of the linear polarizations and reflective for first device light having the other one of the linear polarizations; and a control system (300) configured to control a rotation of the reflective polarizer (430), wherein the control system (300) is configured to control a radiant flux of the first device light (111) escaping from the light generating system (1000) via the first polarizing beam splitter (PBS1) by controlling the rotation of the reflective polarizer (430).

10. The light generating system (1000) according to any one of the preceding claims, further comprising a specular reflective element (440) and a second dichroic beam splitter (DBS2), wherein: the first polarizing beam splitter (PBS1) is configured to direct first device light (111) in dependence of its linear polarization in an optical path in a direction of the light exit (1090) wherein said optical path propagates via the second dichroic beam splitter (DBS2); the first dichroic beam splitter (DBS1) is configured to direct luminescent material light (201), received by the first dichroic beam splitter (DBS1), in an optical path to the light exit (1090), wherein said optical path propagates via the second dichroic beam splitter (DBS2); wherein one of the following applies: (a) the luminescent material (200) is operated in the transmissive mode, wherein the first dichroic beam splitter (DBS1) is configured downstream of the luminescent material (200), or (b) the luminescent material (200) is operated in the reflective mode, wherein the first dichroic beam splitter (DBS1) isconfigured downstream of the first polarizing beam splitter and upstream of the luminescent material (200); and the specular reflective element (440) is configured upstream of the second dichroic beam splitter (DBS2) and downstream of one of the first polarizing beam splitter (PBS1) and the first dichroic beam splitter (DBS1).

11. The light generating system (1000) according to claim 10, further comprising a second depolarizing diffuser (420) configured downstream of the first polarizing beam splitter (PBS1) and upstream of the second dichroic beam splitter (DBS2), wherein the second depolarizing diffuser (420) has a diffusion angle selected from the range of 5-30°.

12. The light generating system (1000) according to any one of the preceding claims, further comprising a (i) a second light generating device (120) and (ii) a redirectional optical element (505), wherein: the second light generating device (120) is configured to provide second device light (121), wherein the second light generating device (120) comprises a laser light source; the redirectional optical element (505) comprises one or more of a second polarizing beam splitter (PBS2) and a third dichroic beam splitter; wherein the redirectional optical element (505) is configured (a) upstream of the first polarizing beam splitter (PBS1) or (b) downstream of the first polarizing beam splitter (PBS1) and upstream of the luminescent material (200); the second light generating device (120) is configured upstream of the redirectional optical element (505); and when (a) the first device light (111) and the second device light (121) have peak wavelengths differing less than 15 nm, the redirectional optical element (505) comprises the second polarizing beam splitter (PBS2), and when (b) the first device light (111) and the second device light (121) have peak wavelengths differing at least 15 nm, the redirectional optical element (505) comprises the second polarizing beam splitter (PBS2) or the third dichroic beam splitter.

13. The light generating system (1000) according to claim 12, wherein the redirectional optical element (505) is configured upstream of the first polarizing beam splitter (PBS1); wherein the second light generating device (120) is configured to generate one ormore of green, yellow, orange, and red second device light (121); and wherein the light generating system (1000) is configured such that the second device light (121) reaching the first depolarizing diffuser (410) comprises polarized light having the first linear polarization.

14. The light generating system (1000) according to claim 12, wherein the redirectional optical element (505) is configured downstream of the first polarizing beam splitter (PBS1) and upstream of the luminescent material (200); wherein the second light generating device (120) is configured to generate second device light (121); wherein the first device light (111) and the second device light (121) have peak wavelengths differing at most 50 nm, and wherein the luminescent material (200) is configured to convert at least part of the second device light (121) received by the luminescent material (200) into luminescent material light (201).

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

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