Color control using high frequency wavelength scanning light source and phosphor

Abstract

The invention provides, inter alia, a light generating system (1000) comprising a first light generating device (110), a second light generating device (120) and a luminescent material (200), wherein: (A) the first light generating device (110) is configured to generate first device light (111); 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 different spectral power distributions; (B) the luminescent material (200) is configured to convert at least part of one of the first device light (111) and the second device light (121) into luminescent material light (201); (C) the first light generating device (110) comprises a wavelength variable light generating device configured to generate the first device light (111) in an operational mode of the light generating system (1000), the first device light (111) varying between at least two centroid wavelengths (I) having a wavelength difference of at least 10 nm at a variation frequency of at least 40 Hz; and (D) the light generating system (1000) is configured to generate, in the operational mode of the light generating system (1000), a white system light (1001) comprising the luminescent material light (201) and the first device light (111) and the second device light (121).

Description

TECHNICAL FIELD

[0001] The present invention relates to a light generating system. The present invention further relates to a light generating device comprising such a light generating system. BACKGROUND

[0002] Devices comprising vertical cavity lasers are known in the art. For example, WO 2004 / 107512 describes a white light laser integrated structure comprising: a) a substrate and b) one or more individually addressable laser pixels formed on the substrate for emitting a white laser beam normal to the substrate, each of the one or more individually addressable laser pixels comprising one or more organic light emitting diodes (OLEDs) and a plurality of organic vertical cavity lasers arranged to be pumped by the one or more OLEDs, wherein the plurality of organic vertical cavity lasers emit light of different colors when combined with light of different colors and the one or more individually addressable laser light emitting pixels emit light that is substantially white. The plurality of organic vertical cavity lasers emit light of two different colors. SUMMARY

[0003] White LED sources can give intensities of e.g. up to about 300 lm / mm 2 ; static phosphor converted laser white sources can give intensities of even up to about 20.000 lm / mm 2 . Ce-doped garnets (e.g. YAG, LuAG) can be the most suitable luminescence converters, since the garnet host has a very high chemical stability, which can be used for pumping with blue lasers. Moreover, at low Ce concentrations (e.g. below 0.5%), temperature quenching can only occur above about 200°C. Furthermore, the emission from Ce has a very fast decay time, so that optical saturation can be essentially avoided. Assuming e.g. a reflective mode operation, the blue laser can be incident on the phosphor. In embodiments, this can enable almost complete conversion of the blue light, resulting in the emission of converted light. It is for this reason that the use of a garnet phosphor with a relatively high stability and thermal conductivity is suggested. However, other phosphors can also be applied. When using very high power densities, thermal management remains an issue.

[0004] High brightness light sources can be used in applications such as projection, stage lighting, spot lighting and automotive lighting. For this purpose, laser-phosphor technology can be used, in which a laser provides a laser light and e.g. (remote) phosphor converts the laser light into converted light. In embodiments, the phosphor can be arranged on or inserted in a heat sink to improve thermal management and thus increase brightness.

[0005] One of the problems that can be associated with such (laser) light sources is the thermal management of the (ceramic) phosphor. Other problems that can be associated with such laser light sources can be the need to manufacture compact high power devices. Further, it can be desirable to provide a wavelength tunable light source. However, typically laser based light sources are not wavelength tunable.

[0006] It is therefore an aspect of the present application to provide an alternative light generating system that preferably also at least partially obviates one or more of the above disadvantages. It can be an object of the present application to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0007] In an aspect, the present application provides a light generating system (“system”) comprising a first light generating device, a second light generating device, and a luminescent material. In particular, the first light generating device can be configured to generate first device light. Further, in particular, the second light generating device can be configured to generate second device light. Further, especially (in an operational mode of the system) the first device light and the second device light have different spectral power distributions. Further, in particular, the luminescent material can be configured to convert at least part of one or more of (a) the first device light and (b) the second device light into luminescent material light. In particular, the first light generating device can comprise a wavelength variable light generating device. The wavelength variable light generating device can be configured to generate, in an operational mode of the light generating system, the first device light varying between at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) of the first light. In particular, the two centroid wavelengths can have a wavelength difference of at least 10 nm, such as at least 20 nm. Further, the wavelength variable light generating device can be configured to generate, in an operational mode of the light generating system, the first device light varying between at least two centroid wavelengths (λ 1c,1 , λ 1c,2) with a variation frequency of at least 40 Hz, in particular at least 50 Hz. Further, the light generating system can be configured to generate, in an operational mode of the light generating system, white system light comprising the first device light and the second device light (at least one of) and the luminescent material light. In particular, in embodiments, the present invention provides a light generating system comprising a first light generating device, a second light generating device and a luminescent material, wherein: (A) the first light generating device is configured to generate first device light; the second light generating device is configured to generate second device light; wherein the first device light and the second device light have different spectral power distributions; (B) the luminescent material is configured to convert at least part of one or more of the first device light and the second device light into luminescent material light; (C) the first light generating device comprises a wavelength variable light generating device configured to generate, in an operational mode of the light generating system, the first device light varying between at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) with a wavelength difference of at least 10 nm with a variation frequency of at least 40 Hz; and (D) the light generating system is configured to generate, in an operational mode of the light generating system, white system light comprising the first device light and the second device light (at least one of) and the luminescent material light.

[0008] With such a system, a relatively large color gamut and / or a relatively large CCT tunability can be provided with a limited number of light sources. Further, with such a system, white light with controllable CCT (substantially along the black body locus) can be provided. Further, with a limited number of light sources, a relatively high CRI can be provided. Further, with the system a relatively strong light can be provided.

[0009] As indicated above, the light generating system can especially comprise a first light generating device, a second light generating device and a luminescent material.

[0010] In particular, the first light generating device is configured to generate first device light. Further, in particular, the second light generating device is configured to generate second device light. In particular, in an operational mode of the system, the first device light and the second device light have different spectral power distributions.

[0011] The first light generating device can comprise one or more (first) light sources, more in particular one or more (first) solid state light sources. Further, the first light generating device can comprise optics. In embodiments, light escaping from the one or more light sources, i.e. first light source light (from the one or more first light sources) can be beam shaped via the optics. The first device light can especially comprise the first light source light. More in particular, the first device light can consist of (first light source) light of the one or more first light sources.

[0012] The second light generating device can comprise one or more (second) light sources, more particularly one or more (second) solid state light sources. Further, the second light generating device can comprise optics. In embodiments, light escaping from the one or more light sources, i.e. second light source light (from the one or more second light sources) can be beam shaped via the optics. The second device light can in particular comprise the second light source light. More particularly, the second device light can consist of (second light source) light of the one or more second light sources.

[0013] Some general aspects relating to a light source are described below, which can apply to the light source of the first light generating device and the light source of the second light generating device.

[0014] The term "light source" can in principle relate to any light source known in the art. It can be a conventional (tungsten) bulb, a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, an LED (light emitting diode).

[0015] In a particular embodiment, the light source comprises a solid state LED light source, such as an LED or a laser diode (or "diode laser").

[0016] The term "light source" can also relate to a plurality of light sources, such as 2-200 (solid state) LED light sources. Hence, the term LED can also refer to a plurality of LEDs. Further, the term "light source" can in embodiments also refer to a so-called chip-on-board (COB) light source. The term "COB" in particular refers to an LED chip in the form of a semiconductor chip that is neither encapsulated nor connected but mounted directly onto a substrate such as a PCB. Hence, a plurality of light emitting semiconductor light sources can be configured on the same substrate. In embodiments, the COB is a multi-LED chip that is configured together as a single lighting module.

[0017] The light source has a light escape surface. With reference to a conventional light source, such as a bulb or a fluorescent lamp, this can be the outer surface of the glass or quartz envelope. For an LED, it can for example be the outer surface of the LED die, or when resin is applied to the LED die, it can be the outer surface of the resin. In principle, it can also be the termination of an optical fiber. The term escape surface in particular relates to the part of the light source from which light actually exits or escapes from the light source. The light source is configured to provide a light beam. This light beam (therefore) escapes from the light exit surface of the light source.

[0018] Likewise, the light generating device can comprise a light escape surface, such as an end window. Further, likewise, the light generating system can comprise a light escape surface, such as an end window.

[0019] The term "light source" can refer to a semiconductor light emitting device such as a light emitting diode (LED), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSEL), an edge emitting laser, or the like. The term "light source" can also refer to an organic light emitting diode (OLED), such as a passive-matrix (PMOLED) or active-matrix (AMOLED). In a particular embodiment, the light source comprises a solid state light source such as an LED or laser diode. In one embodiment, the light source comprises an LED (light emitting diode). The term "light source" or "solid state light source" can also refer to a superluminescent diode (SLED).

[0020] The term LED can also refer to a plurality of LEDs. Further, the term "light source" can also refer to a so-called chip-on-board (COB) light source in embodiments. The term "COB" especially refers to an LED chip in the form of a semiconductor chip that is neither encapsulated nor connected but mounted directly onto a substrate such as a PCB. Thus, a plurality of semiconductor light sources can be configured on the same substrate. In embodiments, the COB is a multi-LED chip that is configured together as a single lighting module.

[0021] The term "light source" can also relate to a plurality of (essentially identical (or different)) light sources, e.g. 2-2000 solid state light sources. In embodiments, the light source can comprise one or more micro-optical elements (microlens array) downstream of a single solid state light source such as an LED or downstream of a plurality of solid state light sources, i.e. e.g. shared by a plurality of LEDs. In embodiments, the light source can comprise an LED with on-chip optics. In embodiments, the light source comprises a pixelated single LED (with or without optics) (providing on-chip beamsteering in embodiments).

[0022] In embodiments, the light source can be configured to provide primary radiation which is used as such, such as e.g. a blue light source like a blue LED, or a green light source such as a green LED, and a red light source such as a red LED. Such LEDs which can not comprise luminescent material ("phosphor") can be denoted as direct colored LEDs.

[0023] However, in other embodiments, the light source can be configured to provide primary radiation, and part of the primary radiation is converted into secondary radiation. The secondary radiation can be based on a conversion by a luminescent material. Hence, the secondary radiation can also be denoted as luminescent material radiation. In embodiments, the luminescent material can be comprised by the light source, such as a LED with a luminescent material layer or a dome comprising a luminescent material. Such a LED can be denoted as a phosphor-converted LED or PC LED. In other embodiments, the luminescent material can be configured at a distance ("remote") from the light source, such as a LED with a luminescent material layer not in physical contact with the die of the LED. Hence, in specific embodiments, the light source can be a light source that emits at least light of a wavelength selected from the range of 380-470 nm during operation. However, other wavelengths are also possible. Such light can be partly used by the luminescent material.

[0024] In embodiments, the light generating device can comprise a luminescent material. In embodiments, the light generating device can comprise a PC LED. In other embodiments, the light generating device can comprise a direct LED (i.e. without phosphor). In embodiments, the light generating device can comprise a laser device, like a laser diode. In embodiments, the light generating device can comprise a superluminescent diode. Hence, in specific embodiments, the light source can be selected from the group of laser diodes and superluminescent diodes. In other embodiments, the light source can comprise a LED.

[0025] The light source can especially be configured to generate light source light having an optical axis (O) (beam shape) and a spectral power distribution. In embodiments, the light source light can comprise one or more bands, with a bandwidth known for lasers.

[0026] The term "light source" can (hence) refer to a light generating element, e.g. a solid state light source, or to a package of light generating elements, such as a solid state light source, and one or more of an element comprising a luminescent material and (other) optical means (e.g. a lens, a collimator). A light converter element ("converter element" or "converter") can comprise an element comprising a luminescent material. For example, a solid state light source like a blue LED is a light source. The combination of a solid state light source (as light generating element) and a light converter element optically coupled to the solid state light source, such as a blue LED and a light converter element, can also be a light source (but can also be denoted as a light generating device). Hence, a white LED is a light source (but can also be denoted as a (white) light generating device), for example.

[0027] The term "light source" herein can refer to a light source comprising a solid state light source, such as a LED or a laser diode or a superluminescent diode.

[0028] Hence, the term "light source" in embodiments can also mean a light source that is (also) based on light conversion, such as a light source in combination with a luminescent converter material. Hence, the term "light source" can also mean the combination of an LED and a luminescent material configured to convert at least part of the LED radiation, or the combination of a (diode) laser and a luminescent material configured to convert at least part of the (diode) laser radiation.

[0029] In embodiments, the term "light source" can also mean the combination of a light source, like an LED, and an optical filter, which can change the spectral power distribution of the light produced by the light source. In particular, the term "light generating device" can be used to describe a light source and further (optical components), like optical filters and / or beam-shaping elements, etc.

[0030] The phrase "different light sources" or "a plurality of different light sources" and similar phrases can in embodiments refer to a plurality of solid state light sources selected from at least two different bins. Likewise, the phrase "same light sources" or "a plurality of same light sources" and similar phrases can in embodiments refer to a plurality of solid state light sources selected from the same bin.

[0031] The term "solid state light source" or "solid state material light source" and similar terms can especially refer to a semiconductor light source, such as a light emitting diode (LED), a diode laser or a superluminescent diode.

[0032] The term "laser source" especially refers to a laser. Such a laser can especially be configured to generate laser source light having one or more wavelengths in the UV, visible or infrared, especially having a wavelength selected from the spectral wavelength range of 200-2000 nm, such as 300-1500 nm. The term "laser" especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

[0033] In particular, in embodiments, the term "laser" can refer to a solid state laser. In a specific embodiment, the term "laser" or "laser source" or similar terms refer to a laser diode (or diode laser).

[0034] Thus, in embodiments, the light source comprises a laser light source. In embodiments, the term "laser" or "solid state laser" can refer to one or more of: cerium-doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), chromium-doped alexandrite laser, chromium ZnSe (Cr:ZnSe) laser, divalent samarium-doped calcium fluoride (Sm:CaF2) laser, Er:YAG laser, erbium-doped and erbium-ytterbium co-doped glass laser, F-center laser, holmium YAG (Ho:YAG) laser, Nd:YAG laser, NdCrYAG laser, neodymium-doped yttrium calcium borate Nd:YCa4O(BO3)3or Nd:YCOB, neodymium-doped yttrium orthovanadate (Nd:YVO4) laser, neodymium glass (Nd:glass) laser, neodymium YLF (Nd:YLF) solid state laser, praseodymium 147-doped phosphate glass (147Pm 3+ :glass) solid state laser, ruby laser (Al2O3:Cr 3+ ), thulium YAG (Tm:YAG) laser, titanium sapphire (Ti:sapphire; Al2O3:Ti 3+ ) laser, trivalent uranium calcium fluoride (U:CaF2) solid state laser, ytterbium-doped glass laser (rod, slab / chip, fiber), ytterbium YAG (Yb:YAG) laser, Yb2O3(glass or ceramic) laser, and the like.

[0035] For example, embodiments including second and third harmonic generation, the light source can comprise one or more of: F-center laser, yttrium orthovanadate (Nd:YVO4) laser, praseodymium 147-doped phosphate glass (147Pm 3+ :glass), and titanium sapphire (Ti:sapphire; Al2O3:Ti 3+ ) laser. For example, such light sources can be used to generate blue light, taking into account the generation of second and third harmonics. Further, for example, InGaN lasers can be applied.

[0036] In embodiments, the term "laser" or "solid state laser" can refer to one or more semiconductor laser diodes, such as GaN, InGaN, AlGalnP, AlGaAs, InGaAsP, lead salts, vertical cavity surface emitting lasers (VCSELs), quantum cascade lasers, hybrid silicon lasers, and the like.

[0037] The laser can be combined with an up-converter in order to reach shorter (laser) wavelengths. For example, up-conversion can be obtained with some (trivalent) rare earth ions, or with a nonlinear crystal. Alternatively, the laser can be combined with a down-converter, such as a dye laser, to reach longer (laser) wavelengths.

[0038] As can be derived from the following, the term "laser light source" can also refer to a plurality of (different or identical) laser light sources. In particular embodiments, the term "laser light source" can refer to N (identical) laser light sources. In embodiments, N = 2 or more. In specific embodiments, N can be at least 5, such as in particular at least 8. In this way, a higher brightness can be obtained. In embodiments, the laser light sources can be arranged in a laser bank (see also above). In embodiments, the laser bank can comprise heat sinks and / or optics, such as lenses for collimating the lasers.

[0039] The laser light source is configured to generate laser light source light (or "laser light"). The light source light can essentially consist of the laser light source light. The light source light can also comprise laser light source light of two or more (different or identical) laser light sources. For example, laser light source light of two or more (different or identical) laser light sources can be coupled into a light guide to provide a single beam of light comprising laser light source light of two or more (different or identical) laser light sources. In particular embodiments, the light source light is thus in particular collimated light source light. In other embodiments, the light source light is in particular (collimated) laser light source light.

[0040] In embodiments, the laser light source light can comprise one or more bands, the bandwidth of which is known for the laser. In particular embodiments, the band(s) can be a relatively sharp line(s), such as having a full width at half maximum (FWHM) in the range of less than 20 nm at RT, such as equal to or less than 10 nm. Thus, the light source light has a spectral power distribution (intensity on an energy scale as a function of wavelength) which can comprise one or more (narrow) bands.

[0041] The beam (of light source light) can be a focused or collimated beam of (laser) light source light. The term "focusing" refers in particular to converging into a small spot. This small spot can be at or (slightly) upstream or (slightly) downstream of the discrete converter region. In particular, the focusing and / or collimating can be such that the (perpendicular to the optical axis) cross-sectional shape of the beam at the discrete converter region (at the side) is substantially no larger than the (perpendicular to the optical axis) cross-sectional shape of the discrete converter region (where the light source light illuminates the discrete converter region). The focusing can be performed with one or more optical elements like (focusing) lenses. In particular, two lenses can be applied to focus the laser light source light. The collimating can be performed with one or more (other) optical elements, like collimating elements, such as lenses and / or parabolic mirrors. In embodiments, the (laser) light source beam can be relatively highly collimated, such as in embodiments < 2° (FWHM), more in particular < 1° (FWHM), most in particular < 0.5° (FWHM). Thus, < 2° (FWHM) can be considered (highly) collimated light source light. Optical elements can be used to provide (highly) collimated (see also above).

[0042] The term "solid state material laser" and similar terms can refer to a solid state laser, e.g. based on a crystal or a glass doped with ions such as transition metal ions and / or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, e.g. a vertical cavity surface emitting laser (VCSEL) or the like.

[0043] The term "solid state light source" and similar terms can especially refer to a semiconductor light source such as a light emitting diode (LED), a diode laser or a superluminescent diode.

[0044] Superluminescent diodes are known in the art. A superluminescent diode can be denoted as a semiconductor device that is capable of emitting a broad spectrum of low coherent light like an LED, while having the brightness of a laser diode.

[0045] For example, US2020192017 states that “With current technology, a single SLED can emit over a bandwidth of, for example, up to 50-70 nm in the 800-900 nm wavelength range with sufficient spectral flatness and sufficient output power. In the visible range for display applications, i.e. in the 450-650 nm wavelength range, with current technology, a single SLED can emit over a bandwidth of up to 10-30 nm. These emission bandwidths are too small for display or projector applications that require red (640 nm), green (520 nm), and blue (450 nm), i.e. RGB emission”. Further, superluminescent diodes are described in “Edge Emitting Laser Diodes and Superluminescent Diodes”, Szymon Stanczyk, Anna Kafar, Dario Schiavon, Stephen Najda, Thomas Sligh, Piotr Perlin, Book Editor(s): Fabrizio Roccaforte, Mike Leszczynski (First published: 03 August 2020, https: / / doi.org / 10.1002 / 9783527825264.ch9, in Chapter 9.3 Superluminescent Diodes). This book, in particular Chapter 9.3, is hereby incorporated by reference. Therein, it is stated that superluminescent diodes (SLDs) are emitters combining features of both laser diodes and light emitting diodes. SLD emitters utilize stimulated emission, which means that these devices operate at current densities similar to laser diodes. The main difference between LDs and SLDs is that in the latter case we design the device waveguide in a special way that prevents standing wave formation and lasing. Also, the presence of the waveguide ensures the emission of a high-quality light beam with a high degree of optical spatial coherence, but the light is characterized by a low temporal coherence at the same time. And “Currently, the most successful designs of nitride SLDs are bent, curved, or tilted waveguide geometries and tilted facet geometries, while in all cases the front end of the waveguide meets the device facet in a tilted manner, as shown in Fig. 9.10. Tilted waveguides suppress the reflection of light from the facet to the waveguide by guiding it outside the lossy, un-pumped region of the device chip”. Thus, SLDs can be semiconductor light sources in particular, in which the spontaneous emission light is amplified by stimulated emission in the active region of the device. This emission is called “superluminescence”. Superluminescent diodes combine the high power and brightness of laser diodes with the low coherence of conventional light emitting diodes. The advantage of the low (temporal) coherence of the source is that speckle is significantly reduced or not visible, and the spectral distribution of the emitted light is much wider than in laser diodes, which can be better suited for illumination applications.In particular, the spectral power distribution of a superluminescent diode can vary with a change in the current. In this way, the spectral power distribution can be controlled, see also Abdullah A. Alatawi et al., Optics Express vol. 26, Issue 20, pp. 26355-26364, https: / / doi.org / 10.1364 / OE.26.026355.

[0046] Vertical cavity surface emitting lasers or VCSELs are known in the art and can in particular be semiconductor laser diodes of the type having a laser beam emission perpendicular to the top surface, as opposed to edge emitting semiconductor lasers (also planar lasers) that emit from a surface formed by cleaving individual chips from a wafer. VCSELs can be tunable in emission wavelength, as known in the art. For example, Dupont et al., Applied Physics Letters 98(16): 161105-161105-3, DOI: 10.1063 / 1.3569591, or Wendi Chang et al., Applied Physics Letters 105(7): 073303, DOI: 10.1063 / 1.4893758, or Thor Ansbaek, IEEE Journal of Selected Topics in Quantum Electronics 19(4): 1702306-1702306, DOI: 10.1109 / JSTQE.2013.2257164, or C. J. Chang-Hasnain, IEEE Journal of Selected Topics in Quantum Electronics (Volume: 6, Issue: 6, Nov.-Dec. 2000), DOI: 10.1109 / 2944.902146, describe tunable emission wavelength VCSELs (all documents incorporated herein by reference). In particular, the spectral power distribution of a VCSEL can vary with a change in the voltage.

[0047] The light generating device can comprise a plurality of different light sources, such as two or more subsets of light sources, each subset comprising one or more light sources configured to generate light source light having substantially the same spectral power distribution, but wherein the light sources of different subsets are configured to generate light source light having different spectral distributions. In such embodiments, the control system can be configured to control the plurality of light sources. In particular embodiments, the control system can individually control the subsets of light sources, see also below.

[0048] In the following, some embodiments regarding the luminescent material are described, after which we return to some embodiments regarding the first light generating device and the second light generating device, respectively.

[0049] As mentioned above, the system can also comprise a luminescent material.

[0050] The term "luminescent material" especially refers to a material which can convert one or more of a first radiation, especially UV radiation and blue radiation, into a second radiation. Typically, the first and second radiation have a different spectral power distribution. Hence, instead of the term "luminescent material", also the term "luminescence converter" or "converter" can be applied. Typically, the second radiation has a spectral power distribution at a larger wavelength than the first radiation, which is the case in so-called down-conversion. However, in specific embodiments, the second radiation has a spectral power distribution with an intensity at a smaller wavelength than the first radiation, which is the case in so-called up-conversion.

[0051] In embodiments, "luminescent material" can especially refer to a material which can convert radiation into e.g. visible light and / or infrared light. For example, in embodiments, the luminescent material is capable of converting one or more of UV radiation and blue radiation into visible light. In specific embodiments, the luminescent material can also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. Typically, the luminescent material will be a down-converter, i.e. a smaller wavelength of radiation is converted into radiation with a larger wavelength (λ ex <λ em ), although in specific embodiments, the luminescent material can comprise an up-converter luminescent material, i.e. a larger wavelength of radiation is converted into radiation with a smaller wavelength (λ ex >λ em ).

[0052] In embodiments, the term "luminescence" can refer to phosphorescence. In embodiments, the term "luminescence" can also refer to fluorescence. Instead of the term "luminescence", also the term "emission" can be applied. Hence, the terms "first radiation" and "second radiation" can refer to excitation radiation and emission (radiation), respectively. Likewise, the term "luminescent material" can in embodiments refer to phosphorescence and / or fluorescence.

[0053] The term "luminescent material" can also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are shown below. Hence, the term "luminescent material" can in specific embodiments also refer to a luminescent material composition.

[0054] In embodiments, the luminescent material is selected from garnets and nitrides, in particular doped with trivalent cerium or divalent europium, respectively. The term "nitride" can also refer to oxynitride or nitridosilicate, etc.

[0055] In a particular embodiment, the luminescent material includes Al2B5O. 12 Ce-containing luminescent materials, wherein A in the 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 the embodiments comprises one or more of Al, Ga, In, and Sc. In particular, A may comprise one or more of Y, Gd, and Lu, for example, especially one or more of Y and Lu. Specifically, B may comprise one or more of Al and Ga, more particularly at least Al, for example, substantially entirely Al. Therefore, cerium-containing garnet materials are particularly suitable luminescent materials. Examples of garnet particularly include Al₂B₅O. 12 Garnet, wherein A comprises at least yttrium or lutetium, and wherein B comprises at least aluminum. This garnet may be doped with cerium (Ce), praseodymium (Pr), or a combination of cerium and praseodymium; however, it is particularly doped with Ce. Specifically, B comprises aluminum (Al), however, B may also partially comprise gallium (Ga) and / or scandium (Sc) and / or indium (In), particularly up to about 20% Al, more particularly up to about 10% Al (i.e., the B ions are essentially composed of 90 or more mol% Al and 10 or less mol% of one or more of Ga, Sc, and In); B may particularly comprise up to about 10% gallium. In another variant, B and O may be at least partially replaced by Si and N. Element A may be selected in particular from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb), and lutetium (Lu). Furthermore, Gd and / or Tb are particularly present only in amounts up to about 20% A. In one specific embodiment, the garnet luminescent material includes (Y 1-x Lu x )3B5O 12 :Ce where x is equal to or greater than 0 and equal to or less than 1. The term ":Ce" indicates that a portion of the metal ions in the luminescent material (i.e., in garnet, the portion of the "A" ions) is replaced by Ce. For example, in (Y 1-x Lu x )3Al5O 12 In the case of Ce: A portion of Y and / or Lu is substituted by Ce. This is known to those skilled in the art. Ce will generally replace no more than 10% of A; typically, the concentration of Ce (relative to A) is in the range of 0.1% to 4%, particularly between 0.1% and 2%. Assuming 1% Ce and 10% Y, the perfectly correct molecular formula could be (Y... 0.1 Lu 0.89 Ce 0.01 )3Al5O 12 As is known to those skilled in the art, Ce in garnet is essentially or only in the trivalent state.

[0056] In an embodiment, the luminescent material thus comprises A3B5O 12 , where in a specific embodiment, up to 10% of the B-O can be replaced by Si-N.

[0057] In a specific embodiment, the luminescent material comprises (Y x1-x2-x3 A’ x2 Ce x3 )3(Al y1-y2 B’ y2 )5O 12 , where x1 + x2 + x3 = 1, where x3 > 0, where 0 < x2 + x3 ≤ 0.2, where y1 + y2 = 1, where 0 ≤ y2 ≤ 0.2, where A’ comprises one or more elements selected from the group consisting of lanthanide elements, and where B’ comprises one or more elements selected from the group consisting of Ga, In, and Sc. In an embodiment, x3 is selected from the range of 0.001 - 0.1. In the present invention, particularly x1 > 0, such as > 0.2, e.g., at least 0.8. Garnets with Y can provide a suitable spectral power distribution.

[0058] In a specific embodiment, up to 10% of the B-O can be replaced by Si-N. Here, B in B-O refers to one or more of Al, Ga / In, and Sc (and O refers to oxygen); in a specific embodiment, B-O can refer to A l-O. As described above, in a specific embodiment, x3 can be selected from the range of 0.001 - 0.04. Particularly, such a luminescent material can have a suitable spectral distribution (however, see below), have a relatively high efficiency, have a relatively high thermal stability, and allow a high CRI (in combination with the first light source light and the second light source light (and the filter)). Thus, in a specific embodiment, A can be selected from the group consisting of Lu and Gd. Alternatively or additionally, B can include Ga. Thus, in an embodiment, the luminescent material comprises (Y x1-x2-x3 (Lu,Gd) x2 Ce x3 )3(Al y1-y2 Ga y2 )5O 12 , where Lu and / or Gd are available. Even more particularly, x3 is selected from the range of 0.001 - 0.1, where 0 < x2 + x3 ≤ 0.1, and where 0 ≤ y2 ≤ 0.1. Further, in a specific embodiment, up to 1% of the B-O can be replaced by Si-N. Here, the percentage refers to the number of moles (as known in the art); also see, for example, EP3149108. In yet another specific embodiment, the luminescent material comprises (Y x1-x3 Ce x3 )3Al5O 12 , where x1 + x3 = 1, and where 0 < x3 ≤ 0.2, such as 0.001 - 0.1.

[0059] In a specific embodiment, the light generating device can comprise only luminescent material selected from the group of cerium containing garnet type luminescent materials. In a further specific embodiment, the light generating device comprises a single type of luminescent material, such as (Y x1-x2-x3 A’ x2 Ce x3 )3(Al y1-y2 B’ y2 )5O 12 Thus, in a specific embodiment, the light generating device comprises luminescent material, wherein at least 85 weight (wt.) %, even more particularly at least about 90 wt. %, for example still even more particularly at least about 95 wt. % of the luminescent material comprises (Y x1-x2-x3 A’ x2 Ce x3 )3(Al y1-y2 B’ y2 )5O 12 wherein A’ comprises one or more elements selected from the group consisting of elements of the lanthanide series, and wherein B’ comprises one or more elements selected from the group consisting of Ga, In and Sc, wherein x1+x2+x3=1, wherein x3>0, wherein 0

[0060] In a specific embodiment, A can particularly at least comprise Y, and B can particularly at least comprise Al.

[0061] Alternatively or additionally, wherein the luminescent material can comprise a luminescent material of the type A3Si6N 11 :Ce 3+ wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as one or more of La and Y in embodiments.

[0062] In embodiments, the luminescent material can alternatively or additionally comprise one or more of: M2Si5N8:Eu 2+ and / or MAlSiN3:Eu 2+ and / or Ca2AlSi3O2N5:Eu 2+where M comprises one or more of Ba, Sr and Ca, in particular at least Sr in embodiments. Thus, in embodiments, the luminescent material can comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu. In these compounds, the europium (Eu) is essentially or only divalent and replaces one or more of the indicated divalent cations. Typically, Eu will not be present in an amount larger than 10% of the cations; its presence is in particular in the range of about 0.5-10%, more in particular in the range of about 0.5-5% relative to the cation(s) it replaces. The term ":Eu" indicates that part of the metal ions are replaced by Eu (in these embodiments by Eu 2+ ). For example, assuming that Eu in CaAlSiN3:Eu is 2%, the correct formula can be (Ca 0.98 Eu 0.02 )AlSiN3. The divalent europium typically replaces a divalent cation, such as the above-mentioned divalent alkaline earth cations, in particular Ca, Sr or Ba. The material (Ba,Sr,Ca)S:Eu can also be denoted as MS:Eu, where M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); in particular, M comprises calcium or strontium, or calcium and strontium, more in particular calcium in this compound. Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr and Ca. Further, the material (Ba,Sr,Ca)2Si5N8:Eu can also be denoted as M2Si5N8:Eu, where M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); in particular, M comprises Sr and / or Ba in this compound. In another specific embodiment, M consists of Sr and / or Ba (not taking into account the presence of Eu), in particular 50-100% Ba and 50-0%, in particular 50-10% Sr, such as Ba 1.5 Sr 0.5 Si5N8:Eu (i.e. 75% Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr and Ca. Also, the material (Ba,Sr,Ca)AlSiN3:Eu can also be denoted as MAlSiN3:Eu, where M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); in particular, M comprises calcium or strontium, or calcium and strontium, more in particular calcium in this compound. Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr and Ca. The Eu in the above luminescent materials is essentially in or only in the divalent state, as known to the skilled person.

[0063] In embodiments, the red luminescent material can comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu. In these compounds, europium (Eu) is essentially or only divalent and replaces one or more of the specified divalent cations. Typically, Eu will not be present in an amount larger than 10% of the cations; its presence is especially in the range of about 0.5-10%, more especially in the range of about 0.5-5% relative to the cation(s) it replaces. The term ":Eu" indicates that part of the metal ions are replaced by Eu (in these embodiments by Eu 2+ For example, assuming that the Eu in CaAlSiN3:Eu is 2% correct the formula can be (Ca 0.98 Eu 0.02 )AlSiN3. The divalent europium typically replaces a divalent cation, such as the above-mentioned divalent alkaline earth cations, in particular Ca, Sr or Ba.

[0064] The material (Ba,Sr,Ca)S:Eu can also be denoted as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); in particular, M comprises calcium or strontium, or calcium and strontium, in this compound, more in particular, M comprises calcium. Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr and Ca.

[0065] Further, the material (Ba,Sr,Ca)2Si5N8:Eu can also be denoted as M2Si5N8:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); in particular, M comprises Sr and / or Ba in this compound. In another specific embodiment, M consists of Sr and / or Ba (not taking into account the presence of Eu), in particular 50-100% Ba and 50-0%, in particular 50-10% Sr, for example Ba 1.5 Sr 0.5 Si5N8:Eu (i.e. 75% Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr and Ca.

[0066] Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be denoted as MAlSiN3:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); in particular, M comprises calcium or strontium, or calcium and strontium, in this compound, more in particular, M comprises calcium. Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr and Ca.

[0067] As known to the person skilled in the art, Eu in the above luminescent material is essentially or only in the divalent state.

[0068] The blue luminescent material can comprise YSO (Y2Si05:Ce 3+ ), or similar compounds, or BAM (BaMgAl 10 11O 17 :Eu 2+ ), or similar compounds.

[0069] The term "luminescent material" herein relates inter alia to inorganic luminescent materials.

[0070] The term "phosphor" is also used instead of the term "luminescent material". These terms are known to the person skilled in the art.

[0071] Alternatively or additionally, other luminescent materials can also be applied. For example, quantum dots and / or organic dyes can be applied and can optionally be embedded in a transmissive matrix, for example a polymer, such as PMMA or polysiloxane, etc.

[0072] Quantum dots are small crystals of semiconductor material, typically having a width or diameter of only a few nanometers. When excited by incident light, quantum dots emit light of a color determined by the size and material of the crystal. Thus, a specific color of light can be produced by adjusting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with a shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium-free quantum dots such as indium phosphide (InP) and copper indium sulfide (CuInS2) and / or silver indium sulfide (AgInS2) can also be used. Quantum dots show very narrow emission bands and thus they show saturated colors. Furthermore, the emission color can be easily adjusted by adjusting the size of the quantum dots. Any type of quantum dots known in the art can be used in the present application. However, for environmental safety and concern reasons, cadmium-free quantum dots or at least quantum dots with very low cadmium content are preferred.

[0073] Instead of or in addition to quantum dots, other quantum confinement structures can also be used. In the context of the present application, the term "quantum confinement structure" is to be understood as for example quantum wells, quantum dots, quantum rods, tripods, tetrapods or nanowires, etc.

[0074] Organic phosphors can also be used. An example of a suitable organic phosphor material is an organic luminescent material based on a perylene derivative, for example the compound sold by BASF under the name Lumation® F Yellow-03. Examples of suitable compounds include, but are not limited to Lumation® F Red 305, Lumation® F Orange 240, Lumation® F Yellow-03, yellow F083 and F170.

[0075] The different luminescent materials can have different spectral power distributions of the respective luminescent material light. Alternatively or additionally, such different luminescent materials can especially have different color points (or dominant wavelengths).

[0076] As mentioned above, other luminescent materials are possible as well. Thus, in specific embodiments, the luminescent material is selected from the group consisting of: divalent europium containing nitrides, divalent europium containing oxonitrides, divalent europium containing silicates, cerium containing garnets and quantum structures. Quantum structures can for example include quantum dots or quantum rods (or other quantum type particles) (see above). Quantum structures can also include quantum wells. Quantum structures can also include photonic crystals.

[0077] Also as mentioned above, the solid state material laser can comprise a luminescent material for generating the laser light, such as a single crystal or a glass comprising the luminescent material. Above, when discussing solid state light sources, more particularly laser light sources, some examples of such lasers are provided. One or more of the above embodiments regarding the luminescent material can also apply to such solid state material lasers. However, the luminescent material described herein as one of at least three elements of the system can especially be configured to convert at least part of one or more of the first device light and the second device light into the luminescent material light. Thus, such luminescent material can convert laser light and can not necessarily be configured such that it also generates laser light. Thus, the luminescent material light can not necessarily be laser light, although laser light is not excluded herein either. However, especially, the luminescent material light generated by the luminescent material is not laser light. More especially, the luminescent material can be chosen such that an emission band with a full width at half maximum (of the luminescent material light) of at least 40 nm, for example at least 50 nm, is obtained. For example, the luminescent material can be chosen such that an emission band with a full width at half maximum of at least 60 nm is obtained. This can for example be the case for a trivalent cerium containing garnet luminescent material (as described herein). Thus, especially, the luminescent material can comprise a broadband emitter. The luminescent material can also comprise a plurality of broadband emitters. Especially, when two or more luminescent materials are applied to convert at least part of the first device light and / or at least part of the second device light, at least two of the two or more luminescent materials can be configured to provide a respective luminescent material light, each luminescent material light having an emission band with a full width at half maximum (of the luminescent material light) of at least 40 nm, for example at least 50 nm.

[0078] In particular, the luminescent material light can comprise visible light. The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. The terms “light” and “radiation” are used interchangeably herein unless the context clearly suggests that the term “light” refers only to visible light. Hence, the terms “light” and “radiation” can refer to UV radiation, visible light and IR radiation. In particular embodiments, especially for lighting applications, the terms “light” and “radiation” refer at least to visible light.

[0079] In particular, the first light generating device can comprise a wavelength variable light generating device. In particular embodiments, the first light generating device can comprise a (emitting) color variable light generating device.

[0080] For example, in embodiments, the first light generating device comprises one or more of a vertical cavity surface emitting laser (VCSEL) and a superluminescent diode.

[0081] Hence, in particular, the first light generating device can provide first device light having at least two different spectral power distributions at different moments in time, respectively. Hence, in particular, the first light generating device is operated in a pulsed mode.

[0082] In embodiments of the operating mode of the system, the change between the at least two different spectral power distributions can be faster than perceivable by the human eye. Hence, the change between the at least two different spectral power distributions can be within 0.025 seconds, such as within 0.02 seconds, even within about 0.0167 seconds.

[0083] In embodiments, the first light generating device can scan between (at least) two spectral power distributions, one spectral power distribution having a first centroid wavelength λ 1c,1 , one spectral power distribution having a second centroid wavelength λ 1c,2 .

[0084] A spectral power distribution can be characterized by a centroid wavelength. The term “centroid wavelength”, also denoted as λc, is known in the art and refers to the wavelength value at which half of the light energy lies at shorter wavelengths and half of the energy at longer wavelengths; this value is expressed in nanometers (nm). It is the wavelength that divides the integral of the spectral power distribution into two equal parts, as expressed by the formula λc = ∑λ*I(λ) / (∑I(λ), where the summations are over the wavelength range of interest, and I(λ) is the spectral energy density (i.e. the integral of the product of wavelength and intensity normalized to the integral intensity over the emission band). The centroid wavelength can be determined, for example, under operating conditions.

[0085] Hence, in particular, the first light generating device comprises a wavelength variable light generating device configured to generate, in the operational mode of the light generating system, first device light varying between at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ). Hence, effectively in the operational mode, the first light generating device (or more precisely its device light) can be scanned between two centroid wavelengths. There can be intermediate centroid wavelengths when varying from the first centroid wavelength and the second centroid wavelength. Hence, the term "at least two centroid wavelengths (λ 1c,1 , λ 1c,2 )" is used. In embodiments, the at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) can also be denoted as outer centroid wavelengths. The first and second centroid wavelengths (λ 1c,1 , λ 1c,2 ) can have a difference of at least 10 nm, such as at least 20 nm, like at least 30 nm, or even in embodiments at least 40 nm (like even at least 60 nm, or even at least 80 nm, such as in particular embodiments at least 100 nm). In particular embodiments, the difference between the at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) can be at least 50 nm. Further, the variation from the first centroid wavelength to the second centroid wavelength can be at a frequency of at least 40 Hz, like at least 50 Hz, or more in particular at least 60 Hz, like at least 80 Hz (and in particular embodiments (even) at least 100 Hz). Hence, in embodiments, the first light generating device comprises a wavelength variable light generating device configured to generate, in the operational mode of the light generating system, first device light varying between at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) with a difference in wavelength of at least 10 nm at a variation frequency of at least 40 Hz. In particular, the variation frequency can be at least 60 Hz.

[0086] The luminescent material can be configured to convert at least part of the first device light and / or at least part of the second device light. Hence, the luminescent material can be configured downstream of the first light generating device and / or the second light generating device. The terms "upstream" and "downstream" relate to the arrangement of items or features with respect to the propagation of light from a light generating device (here in particular a light source), wherein a second position in the light beam closer to the light generating device is "upstream" with respect to a first position in the light beam from the light generating device, and a third position in the light beam further away from the light generating device is "downstream". In particular, the luminescent material can be configured to convert at least part of the first device light or at least part of the second device light.

[0087] Hence, the luminescent material can be configured to convert at least part of the first device light. Hence, in particular, the operating conditions of the luminescent material and the first light generating device are selected in the operational mode such that the luminescent material converts the first device light having the first centroid wavelength and the first device light having the second centroid wavelength. However, as mentioned above, the luminescent material can be configured to convert at least part of the second device light. If the second light generating device is configured to generate the second device light in the operational mode of the light generating system, which second device light varies between at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) having a wavelength difference of at least 10 nm at a variation frequency of at least 40 Hz (see also below), and if the luminescent material is configured to convert at least part of the second device light, the luminescent material and the second light generating device can be selected in the operational mode such that the luminescent material converts the second device light having the first centroid wavelength (of the second device light) and the second device light having the second centroid wavelength (of the second device light).

[0088] In the operational mode, the system can be configured to generate white light. The white light can in particular comprise one or more of (a) the first device light and (b) the second device light and the luminescent material light. Even more in particular, the white light can in particular comprise the luminescent material light, the first device light and the second device light. However, in a particular embodiment, the white light can essentially consist of the luminescent material light, the first device light and the second device light. Hence, in embodiments, the light generating system can be configured to generate, in the operational mode of the light generating system, white system light comprising at least one of the first device light and the second device light and the luminescent material light.

[0089] The term "white light" herein is known to the person skilled in the art. It relates in particular to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, e.g. between 2000 K and 20000 K, in particular between 2700-20000 K, for general lighting in particular in the range of about 2700 K and 6500 K. In embodiments, for the purpose of backlighting, the correlated color temperature (CCT) can in particular be in the range of about 7000 K and 20000 K. Further, in embodiments, the correlated color temperature (CCT) is in particular within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), in particular within about 10 SDCM from the BBL, even more in particular within about 5 SDCM from the BBL.

[0090] With the present application, it is possible to provide white light with controllable CCT substantially along the black body locus, such as within 15 SDCM of the BBL, more particularly within 10 SDCM, even more particularly within about 5 SDCM. Moreover, in particular, the CCT tunability can exceed at least 500 K, more particularly at least 1000 K, such as at least 1500 K, even more particularly at least 2000 K. For example, the system light can be tunable between about 4500-6500 K (2000 K tunability), or between about 2200-4200 K (also 2000 K tunability), or in embodiments for example exceeding 2200-6500 K (even 4300 K tunability), although other ranges are possible as well.

[0091] It is noted that in further embodiments, the system can have a further operational mode in which the system light can comprise one or more of the luminescent material light, the first device light and the second device light. However, in particular embodiments, further light generating devices are available that are configured to generate device light having a spectral power distribution different from the first device light and the second device light, and that (in the operational mode(s)) contribute their light to the system light.

[0092] In particular, the first device light and the second device light can have different spectral power distributions. Whatever centroid wavelength the first device light can have, it can be (substantially) different from the second device light. For example, the centroid wavelength(s) of the first device light and the centroid wavelength(s) of the second device light can differ by at least 30 nm, such as at least 50 nm, like at least 80 nm. However, in further particular embodiments, the centroid wavelength(s) of the first device light and the centroid wavelength(s) of the second device light can differ by at least 60 nm, such as at least 90 nm, like at least 105 nm, or even at least about 115 nm. Moreover, in embodiments, the spectral overlap of the smaller emission band with the larger emission band can be less than 20% of the smaller emission band, such as less than 10%.

[0093] In particular embodiments, the first light generating device and the second light generating device can be substantially uncontrollable to the extent of obtaining an overlapping spectral power distribution of the first device light and the second device light. In particular, the spectral overlap of the smaller emission band with the larger emission band can be less than 1%, such as less than 0.5%.

[0094] As mentioned above, the first light generating device can comprise one or more light sources, in particular solid state light sources. Moreover, the first device light can be controllable. This can mean that the light source light of the one or more light sources is controllable. For example, the one or more light sources of the first device can comprise one or more of the above-mentioned vertical cavity surface emitting lasers (VCSELs) and superluminescent diodes.

[0095] As mentioned above, in embodiments the first device light can essentially consist of the light source light of the one or more light sources. However, other embodiments are possible as well. For example, while the first device light can be visible light, the light source light can not be visible light. Or in embodiments the light source light can be red and the first device light can be blue. In particular, this can be achieved when using up-converter materials. Thus, in particular embodiments the first light generating device comprises: (a) a wavelength variable first light source configured to generate, in the operational mode of the light generating system, a first light source light varying between at least two centroid wavelengths ((λ pc,1 , λ pc,2 ) having a wavelength difference of at least 20 nm at a variation frequency of at least 40 Hz, such as in particular at least 50 Hz; and (b) an up-converter material configured downstream of the wavelength variable first light source and configured to convert at least part of the first light source light varying between the at least two centroid wavelengths ((λ pc,1 , λ pc,2 ) into the first device light varying between the at least two centroid wavelengths ((λ 1c,1 , λ 1c,2 ). In particular, the up-converter material comprises one or more of an up-converter luminescent material and a frequency doubling material.

[0096] The up-conversion can for example be based on an up-converter luminescent material or a frequency doubling conversion material. Both are denoted herein with the general term “converter material”. The up-conversion can be frequency doubling (or halving of the wavelength), which can be achieved with a frequency doubling material, for example a second harmonic generation crystal, such as BiBo (BiB3O6), lithium iodate LiLO3, BBO (beta-BaB2O4), KH2PO4, etc., or based on a luminescent material, for example based on Yb 3+ -Er 3+ pairs (e.g. systems based on “addition of photons by energy transfer” (APTE), now commonly referred to as energy transfer up-conversion (ETU)), or via a two-step absorption process, which can use systems based on Er 3+ , or via a synergistic sensitization process, which can use Yb 3+ -Tb 3+ pairs, or via a synergistic luminescence process, or via a two-photon excitation process, for example can use some systems based on Eu 2+ . Other pairs are possible as well, for example Yb 3+ -Tm 3+ .

[0097] Another system can be based on Pr 3+ , and / or Ho 3+ , Tb 3+ , Tm 3+ , Er3+ One or more of the above, as described in US2010 / 0297206, are incorporated herein by reference.

[0098] For example, in the embodiments, the material (which may also be referred to as the "body material") may be selected from NaLnF4, LiLnF4, KLnF4, LnF3, BaLn2F8, SrLn2F8, CaLn2F8, MgLn2F8; wherein Ln is (a) Pr 3+ Yb 3+ Ho 3+ Tm 3+ and Er 3+ One or more of them; more specifically, of which Ln 3+ It's Gd 3+ and (b)Pr 3+ Yb 3+ HO 3+ Tm 3+ and Er 3+ One or more of the following, wherein the material specifically includes at least a first lanthanide ion and a second lanthanide ion different from the first lanthanide ion. For example, in embodiments, the material may be selected from NaLnF4, LiLnF4, NaLnF4, LiLnF4, KLnF4, LnF3, LiYF4, KYF4, BaLn2F8, SrLn2F8, CaLn2F8, MgLn2F8, BaLn2F8, SrLn2F8, CaLn2F8, or MgLn2F8, wherein Ln includes (a) selected from Gd 3+ Pr 3+ Tm 3+ Or Er 3+ The first lanthanide ion of group (b) and (b) are selected from Pr 3+ Yb 3+ Ho 3+ Tm 3+ Er 3+ The material comprises at least a first lanthanide ion and a second lanthanide ion different from the first lanthanide ion. Specifically, in embodiments, Ln may comprise one or more of Lu and La, and at least one or more first lanthanide ions and one or more second lanthanide ions. Furthermore, particularly in embodiments, Ln may comprise at least Gd, and optionally one or more of Lu and La, and at least one or more second lanthanide ions.

[0099] Furthermore, also semiconductor nanoparticles can be used. For example, perovskite CsPbBr3 nanocrystals with a molecular synthesizer show emission with a conversion efficiency of more than 10% in the range of 340-400 nm obtainable by excitation at 440 nm. For example, reference can be made to Wieghold S, Nienhaus L Correction: Engineering 3D perovskites for photon interconversion applications. PLOS ONE 15(4): e0232196. https: / / doi.org / 10.1371 / journal.pone.0232196.

[0100] Other upconversion examples can for example be UV Pr 3+ doped crystals, such as Lu7O6F9:Pr 3+ or Y2SiO5:Pr 3+ ) or NaYF4:Yb 3+ , Tm 3+ . Other examples can be found in Bright Infrared-to-Ultraviolet / Visible Upconversion in Small Alkaline Earth-Based Nanoparticles with Biocompatible CaF2 Shells Fischer - 2020 - Angewandte Chemie International Edition - Wiley Online Library Figures 1-7 Figures 8A-9C which is incorporated herein by reference and which describes sub-15 nm alkaline earth rare earth fluoride UCNPs (M 1-x Ln x F 2+x with CaF2 shells with NIR-UV / visible emission. Different alkaline earth host materials doped with Yb 3+ and Tm 3+ , wherein the alkaline earth (M) comprises Ca, Sr and Ba, MgSr, CaSr, CaBa, SrBa and CaSrBa.

[0101] Furthermore, reference is made to US2010 / 0297206, which is incorporated herein by reference. More information on upconversion can also be found in for example G. Blasse et al., Luminescent Materials, Springer Verlag 1994, chapter 10.1. Hence, in embodiments, the first converter material can comprise an upconverter luminescent material. Alternatively or additionally, the first converter material can comprise a frequency doubling (crystal) material.

[0102] As mentioned above, in embodiments, the luminescent material can comprise a luminescent material of the A3B5O 12 :Ce type, 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.

[0103] In embodiments, the luminescent material can comprise a single crystal, a glass or a ceramic body. In specific embodiments, the system can (thus) comprise a ceramic body, wherein the ceramic body comprises the luminescent material.

[0104] Above, the first light generating device was described in more detail. The second light generating device can in particular also comprise a solid state light source, such as a solid state material light source. In particular, the second light generating device can comprise one or more of a diode laser and a superluminescent diode. However, in embodiments, the second light generating device comprises a vertical cavity surface emitting laser (VCSEL).

[0105] Thus, in specific embodiments, the second light generating device can also comprise a wavelength variable light generating device. Thus, in embodiments, the second light generating device can comprise a (emitting) color variable light generating device.

[0106] Thus, in specific embodiments, the second light generating device can comprise a wavelength variable light generating device configured to generate, in the operational mode of the light generating system, a second device light that varies between at least two centroid wavelengths (λ 2c,1 , λ 2c,2 ) having a wavelength difference of at least 10 nm, such as at least 30 nm, even at least 40 nm, with a variation frequency of at least 40 Hz, in particular at least 50 Hz, even more in particular at least 60 Hz, for example at least 80 Hz (and in specific embodiments (even) at least 100 Hz). Thus, in specific embodiments, the second light generating device can operate in a pulsed mode.

[0107] Thus, in specific embodiments, the second light generating device can provide a second device light having at least two different spectral power distributions at different moments in time, respectively.

[0108] As mentioned above, in embodiments of the operational mode of the system, the variation between the at least two different spectral power distributions can be faster than perceivable by the human eye. Thus, the variation between the at least two different spectral power distributions can be within 0.025 seconds, such as within 0.02 seconds, even within approximately 0.0167 seconds.

[0109] Thus, in embodiments, the second light generating device can scan between (at least) two spectral power distributions, one spectral power distribution having a first centroid wavelength λ 2c,1 , and one spectral power distribution having a second centroid wavelength λ 2c,2 .

[0110] Further, the second light generating device can also comprise an up-conversion material. Thus, embodiments described with respect to the first light generating device can also apply with respect to the second light generating device. However, in particular, the devices are chosen such that the first device light and the second device light have different spectral power distributions (see also above).

[0111] In embodiments, the first light generating device can comprise an IR VCSEL or an IR superluminescent diode, assuming up-conversion in case of the first light generating device. In embodiments, the second light generating device can comprise an IR VCSEL or an IR superluminescent diode, assuming up-conversion in case of the second light generating device.

[0112] In embodiments, the luminescent material can be configured to generate luminescent material light having a color point in the green, yellow or orange, in particular green or yellow. Further, in embodiments, the first light generating device can be configured to generate blue light or red light. However, in embodiments, the second light generating device can be configured to generate red light or blue light. Thus, in particular embodiments, (a) the first light generating device can be configured to generate first device light having a centroid wavelength in the blue wavelength range, and wherein the second light generating device is configured to generate second device light having a centroid wavelength in the red wavelength range; or (b) the first light generating device can be configured to generate first device light having a centroid wavelength in the red wavelength range, and wherein the second light generating device is configured to generate second device light having a centroid wavelength in the blue wavelength range.

[0113] The term "violet light" or "violet emission" relates especially to light having a wavelength in the range of about 380-440 nm. The term "blue light" or "blue emission" relates especially to light having a wavelength in the range of about 440-495 nm (including some violet and cyan hues). The term "green light" or "green emission" relates especially to light having a wavelength in the range of about 495-570 nm. The term "yellow light" or "yellow emission" relates especially to light having a wavelength in the range of about 570-590 nm. The term "orange light" or "orange emission" relates especially to light having a wavelength in the range of about 590-620 nm. The term "red light" or "red emission" relates especially to light having a wavelength in the range of about 620-780 nm. The term "pink light" or "pink emission" refers to light having a blue and a red component. The term "cyan" can refer to one or more wavelengths selected from the range of about 490-520 nm. The term "amber" can refer to one or more wavelengths selected from the range of about 585-605 nm, such as about 590-600 nm. The phrase "light having one or more wavelengths in a range of wavelengths" and similar phrases can especially indicate that the indicated light (or radiation) has a spectral power distribution with at least an intensity or a plurality of intensities at the one or more wavelengths in the indicated range of wavelengths. For example, a blue-emitting solid state light source will have a spectral power distribution with an intensity at one or more wavelengths in the range of 440-495 nm.

[0114] In a particular embodiment, the system can further comprise a control system configured to control the system light, especially in dependence of one or more of an input signal of a user interface, a sensor signal of a sensor, and a timer, and especially by (separately) controlling the first light generating device and the second light generating device.

[0115] The term "control" and similar terms refer, inter alia, to at least determining a behavior of an element or supervising a running of an element. Hence, "control" and similar terms here can refer, for example, to exerting a behavior on an element (determining a behavior or supervising a running of an element), for example, measuring, displaying, actuating, opening, displacing, changing a temperature, etc. In addition thereto, the term "control" and similar terms can also include monitoring. Hence, the term "control" and similar terms can include exerting a behavior on an element as well as exerting a behavior on an element and monitoring the element. The control of an element can be done with a control system, which can also be denoted as "controller". The control system and the element can thus be functionally coupled at least temporarily or permanently. The element can comprise the control system. In embodiments, the control system and the element can not be physically coupled. The control can be done via wired and / or wireless control. The term "control system" can also refer to a plurality of different control systems, which are functionally coupled, inter alia, and wherein, for example, one control system can be a master control system and one or more other control systems can be slave control systems. The control system can comprise or can be functionally coupled to a user interface.

[0116] The control system can also be configured to receive and execute instructions from a remote control. In embodiments, the control system can be controlled via an App on a device, for example, a portable device, such as a smartphone or I-phone, a tablet, etc. Hence, the device does not have to be coupled to the lighting system, but can be (temporarily) functionally coupled to the lighting system.

[0117] Hence, in embodiments, the control system can (also) be configured to be controlled by an App on a remote device. In such embodiments, the control system of the lighting system can be a slave control system or control in slave mode. For example, the lighting system can be identified with a code, in particular a unique code for the respective lighting system. The control system of the lighting system can be configured to be controlled by an external control system, which has access to the lighting system based on knowledge of the (unique) code (input by a user interface with an optical sensor, for example, a QR code reader). The lighting system can also comprise means for communicating with other systems or devices, such as based on Bluetooth, WIFI, LiFi, ZigBee, BLE, or WiMAX, or other wireless technologies.

[0118] A system, device or apparatus can perform an action in a "mode" or "operating mode" or "mode of operation" or "operational mode". The term "operational mode" can also be denoted as "control mode". Likewise, in a method, an action or phase or step can be performed in a "mode" or "operating mode" or "mode of operation" or "operational mode". This does not exclude that the system, device or apparatus can also be adapted to provide another control mode or a plurality of other control modes. Likewise, this can not exclude that one or more other modes can be performed before and / or after the performance of the mode.

[0119] However, in embodiments, a control system can be available which is adapted to provide at least a control mode. If other modes are available, the selection of such mode can be performed in particular via a user interface, although other options (like performing a mode according to a sensor signal or a (time) scheme) are possible as well. In embodiments, the operational mode can also refer to a system, device or apparatus which is only capable of operating in a single operational mode (i.e. "on", without further tunability).

[0120] Hence, in embodiments, the control system can 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" can refer to a clock and / or a predetermined time scheme.

[0121] It is also desirable to tune the spectral power composition of the system light. This can be achieved in particular by controlling the first light generating device and the second light generating device. In particular, this can be achieved by controlling the duty cycle of the first device light (and / or optionally the second device light). In this way, the (varying) frequency of the first device light can be kept substantially the same, but the spectral power distribution can be controlled by increasing or shortening the pulse time of the respective pulse of the first or second centroid wavelength. Hence, in embodiments, the control system can be configured to control the first light generating device by pulse width modulation, wherein the control system is configured to control the spectral power distribution of the system light in the operational mode by controlling the duty cycle of the first device light. In particular, in embodiments, the wavelength variable light generating device is configured to generate, in the operational mode, a first pulse of the first device light having a centroid wavelength (λ 1c,1 ) and a second pulse of the first device light having a centroid wavelength (λ 1c,2 ), each pulse having a pulse frequency of at least 40 Hz (more particularly at least 50 Hz, still even more particularly at least 60 Hz), wherein the spectral power distribution of the system light in the operational mode comprises controlling the duty cycle of the first pulse and the duty cycle of the second pulse separately.

[0122] Hence, in embodiments, pulse width modulation can be applied to control the spectral power distribution of the first device light, and thereby the spectral power distribution of the system light. Alternative solutions for controlling the spectral power distribution of the first device light are also possible, such as by controlling the pulse height(s). Note that the spectral power distribution of the system light can also be controlled by controlling the second device light. In particular embodiments, this can also be achieved via pulse width modulation, but other solutions can also be applied, such as varying the power provided to the second light generating device.

[0123] Further, in particular embodiments, the luminescent material can comprise a luminescent material of the A3B50i type, wherein A can comprise one or more of Y, La, Gd, Tb and Lu, and wherein B can comprise one or more of Al, Ga, In and Sc; the light generating system can comprise a ceramic body, wherein the ceramic body can comprise the luminescent material; wherein the second light generating device can comprise one or more of a diode laser and a superluminescent diode; wherein the first light generating device can be configured to generate first device light having a centroid wavelength in a blue wavelength range, and wherein the second light generating device can be configured to generate second device light having a centroid wavelength in a red wavelength range. 12 :Ce type, wherein A can comprise one or more of Y, La, Gd, Tb and Lu, and wherein B can comprise one or more of Al, Ga, In and Sc; the light generating system can comprise a ceramic body, wherein the ceramic body can comprise the luminescent material; wherein the second light generating device can comprise one or more of a diode laser and a superluminescent diode; wherein the first light generating device can be configured to generate first device light having a centroid wavelength in a blue wavelength range, and wherein the second light generating device can be configured to generate second device light having a centroid wavelength in a red wavelength range.

[0124] Further, in particular embodiments, the control system can be configured to control the system light in the operational mode of the light generating system to be in a correlated color temperature range of 2000-6500K, such as 2200-6500K, even more particularly 2700-6500K. Alternatively or additionally, the control system can be configured to control the system light in the operational mode of the light generating system to have a color rendering index of at least 80. Hence, in particular, the control system can be configured to control the system light in the operational mode of the light generating system to be in a correlated color temperature range of 2700-6500K and to have a color rendering index of at least 80.

[0125] The light generating system can be part of or applied in, for example, an office lighting system, a home application system, a shop lighting system, a home lighting system, a spot lighting system, a spotlighting system, a theater lighting system, a fiber application system, a projection system, a self-luminous display system, a pixelated display system, a segmented display system, a warning sign system, a medical lighting application system, an indication sign system, a decorative lighting system, a portable system, a car application, a (outdoor) road lighting system, a city lighting system, a greenhouse lighting system, horticulture lighting, digital projection or LCD backlighting. The light generating system (or luminaire) can be part of or can be applied in, for example, an optical communication system or a disinfection system.

[0126] In yet another aspect, the present application also provides a lamp or luminaire comprising a light generating system as defined herein. The luminaire can further comprise a housing, optical elements, louvers, etc. The lamp or luminaire can further comprise a housing encapsulating the light generating system. The lamp or luminaire can comprise a light window or housing opening in the housing through which system light can escape from the housing. In yet another aspect, the present application also provides a projection device comprising a light generating system as defined herein. In particular, a projection device or "projector" or "image projector" can be an optical apparatus that projects an image (or moving images) onto a surface such as a projection screen. The projection device can comprise one or more light generating systems as described herein. Thus, in an aspect, the present application also provides a light generating device selected from the group of a lamp, a luminaire, a projector device, a disinfection device and an optical wireless communication device, the light generating device comprising a light generating system as defined herein. The light generating device can comprise a housing or carrier configured to house or support one or more elements of the light generating system. For example, in embodiments, the light generating device can comprise a housing or carrier configured to house or support one or more of a first light generating device, a second light generating device and a luminescent material. BRIEF DESCRIPTION OF DRAWINGS

[0127] Embodiments of the application are described by way of example only, with reference to the accompanying drawings, in which corresponding reference signs indicate corresponding parts, and in which:

[0128] Figure 10 Some embodiments and examples are schematically depicted;

[0129] Figure 1 Some embodiments and aspects are schematically depicted; and

[0130] Figure 2 Some applications are schematically described.

[0131] The drawings are not necessarily to scale. DETAILED DESCRIPTION

[0132] Wavelength tunable VCSELs are for example available in the red-IR range using MEMs. Such light sources can be used to generate wavelength tunable lasers in the blue region by for example frequency doubling. In addition to such VCSELs, emission in the blue region has appeared and their efficiency and power has reached several watts.

[0133] It is described below how such wavelength tunable lasers can be used to generate a BBL tunable white light source. In embodiments, a wavelength tunable blue laser, a red laser (which can also be wavelength tunable) and a ceramic phosphor for partially converting the blue light can be used for wavelength tuning.

[0134] If we consider a Ce-doped YAG ceramic with an absorbance of 0.42 at 465 nm, which is close to the peak absorbance. Using the absorbance curve of Ce:YAG as a function of wavelength, we can calculate the amount of blue light that passes through the ceramic and the amount of yellow light emitted by the Ce:YAG as a result of absorbing the blue light. Figure 3 The color points at discrete blue wavelengths are shown.

[0135] For example, if a light source is used that can scan between 440 nm and 465 nm and is combined with a laser that emits at 625 nm, a light source can be made that can produce color points in the triangle shown. Figure 3 A light source that can produce any color point within the triangle shown. The CCT can then be changed along the BBL in the range of about 3000-7000 K.

[0136] It is also possible to move the color point continuously along the BBL between 7000 K and 2700 K by continuously scanning the blue laser between 440 nm and 460 nm and by adjusting the relative intensities of the blue and red light sources.

[0137] In Figure 4 , the use of a YAG ceramic is shown with an absorbance of 0.56 at 465 nm and a light source is used that can scan between 440 nm and 465 nm and is combined with a laser that emits at 625 nm. A light source can now be made that can produce color points in the triangle shown. Figure 5 A light source that can produce any color point within the triangle shown. This allows for a scan of (the system light) for example between about 4800 K and 2200 K.

[0138] Table 1 shows the properties of the white light on the BBL at the wavelengths obtained during the scan:

[0139]

[0140] Laser-phosphor based light sources are of great interest due to their potential in producing extremely high intensities. There are already products on the market such as automotive headlamps and projectors in which lasers are used to pump phosphors. Laser phosphors can also be used for other lighting applications. However, for BBL dimming, at least red, green and blue individually controllable laser based light sources are needed.

[0141] Among others, it is suggested herein to use BBL dimming using at least a high frequency wavelength scanning laser and a ceramic phosphor. The high frequency wavelength scanning laser can be a VCSEL that can be switched between orange and red light. By using such a source in combination with a blue laser and a YAG / LuAG ceramic phosphor brick, it is possible to follow a BBL, e.g. for BBL dimming. Alternatively, or in addition, a blue (or green) high frequency wavelength scanning laser can be used to adjust the blue (or green) wavelength. PWM (pulse width modulation) can be used to control the intensity of the laser.

[0142] Figure 6 Schematically shown are several color points that can be obtained using a blue laser of about 450 nm, a green / yellow emitting material with a color point at 560 nm and a VCSEL emitting about orange / red at different wavelengths. Note that the white light can have a controllable CCT (essentially along the black body locus). The different circles represent color points that can be selected according to the wavelength of the tunable device light, such as a VCSEL (which is shown as an example).

[0143] Among others, it is suggested herein to use tunable lasers in the production of light sources with tunable properties such as (i) color temperature, (ii) CRI and / or (iii) R9 values. It can also be used for other effects that need to be compensated. Among others, it is suggested to use a wavelength tunable IR vertical cavity surface emitting laser (VCSEL) in combination with a suitable non-linear optical (NLO) crystal to generate a second harmonic, and thereby obtain a tunable visible laser.

[0144] Figure 7 Schematically shown is the spectrum of a possible wavelength tunable VCSEL.

[0145] For example, a tunable visible laser can be used to adjust the color point / color temperature. This can be done directly by the tunable visible laser, or indirectly by pumping a phosphor, where the conversion rate depends on the pump wavelength. For the latter configuration, a dichroic element (e.g. a dichroic mirror for splitting the laser beam) can be used to enhance the effect. Multiple peaks are shown. Intermediate peaks are also possible.

[0146] Alternatively, for example, it is known that the absorption level of a garnet phosphor at a given wavelength decreases with increasing temperature. As a result, the color point of the light source changes as a function of the light intensity. A tunable blue laser can be used to compensate for the temperature absorption and thus maintain the color point of the phosphor as a function of temperature.

[0147] In an embodiment, a tunable red emitting laser can be obtained which emits light in the wavelength range from 620 nm to 675 nm after frequency doubling of a tunable IR laser emitting in the wavelength range from 1240 nm to 1350 nm. Thus, with a wavelength tunable light source tunable in the IR, a wavelength tunable light source tunable in the visible light can also be obtained (see also below).

[0148] Likewise, tunable IR emitting lasers in the wavelength ranges from 900-990 nm and 990-1140 nm can be used to generate tunable lasers emitting in the blue 450-495 nm and green 495-570 nm, respectively.

[0149] Figure 7 A spectrum of a light source comprising a combination of a blue laser at 440 nm with a YAG:Ce 2% phosphor and a red laser at 610 nm is shown. For example, light can be obtained with CCT = 3000 K, CRI = 66, R9 = -64 and a conversion efficiency of 373 lm / W. The continuously increasing curve schematically depicts the spectral power distribution of a black body radiator at approximately 3000 K (see also Figure 8A ).

[0150] Figures 8A-8B A spectrum with a higher light quality is shown, i.e. at the same CCT = 3000 K, CR1 = 90 and R9 = 92, but with a blue laser at 470 nm and a red laser at 630 nm with a lower efficiency of 330 Lm / W.

[0151] With reference to Figure 8A , in an embodiment, the light generating system 1000 can comprise a first light generating device 110, a second light generating device 120 and a luminescent material 200.

[0152] The first light generating device 110 can be configured to generate first device light 111. The second light generating device 120 can be configured to generate second device light 121. The first device light 111 and the second device light 121 have different spectral power distributions.

[0153] The luminescent material 200 can be configured to convert at least part of one or more of the first device light 111 and the second device light 121 into luminescent material light 201. The luminescent material 200 can comprise A3B5O 12 :Ce 3+The light-emitting material 200 is described. A may include one or more of Y, La, Gd, Tb, and Lu, and B may include one or more of Al, Ga, In, and Sc. The light-generating system 1000 may include a ceramic body 210, and the ceramic body 210 may include the light-emitting material 200. Reference numeral 550 indicates an optical device, which may include, for example, a beam-forming element such as a collimator or lens. Other optical devices (not shown) are also possible. Specifically, optical device 550 refers to an optical device disposed downstream of the first light-generating device, the second light-generating device, and the light-emitting material.

[0154] In an embodiment, the light generation system 1000 may further include a control system 300 configured to control the system light 1001 by controlling the first light generation device 110 and the second light generation device 120 based on one or more of an input signal from a user interface, a sensor signal (of a sensor), and a timer.

[0155] refer to Figure 8C First light generating device 110 (see Figure 8B The system may include a wavelength-variable light generating device configured to generate a first device light 111 in an operating mode of the light generating system 1000, the first device light 111 having a wavelength difference of at least 10 nm (denoted as λ in the figure). 1c At least two centroid wavelengths (λ) 1c,1 , λ 1c,2 The wavelengths vary between these bands at a frequency of at least 40 Hz. The frequency of variation can be at least 50 Hz, and even more particularly at least 60 Hz. The smallest wavelength band (on the left) can have a centroid wavelength λ. 1c,1 The largest wavelength band (on the right) can have a centroid wavelength λ. 1c,2 Therefore, these at least two centroid wavelengths λ 1c,1 , λ 1c,2 It can be represented as the wavelength of the outer centroid.

[0156] The light generating system 1000 can be configured to generate white system light 1001 in an operating mode of the light generating system 1000. The white system light 1001 includes at least one of a first device light 111 and a second device light 121 and a light-emitting material light 201.

[0157] In a particular embodiment of the light generation system 1000, the first light generation device 110 may include one or more of a vertical cavity surface-emitting laser (VCSEL) and a superluminescent diode.

[0158] Figure 8DAn embodiment is schematically shown in which the luminescent material is configured to convert a portion of the first device light 11 having a controllable centroid wavelength (see Figure 8A ).

[0159] Figure 8E An embodiment is schematically shown in which the luminescent material is configured to convert a portion of the second device light 121. Further, the schematically shown embodiment is essentially the same as the embodiment schematically shown in Figure 8F .

[0160] Figure 8F An embodiment is schematically depicted in which the second light generating device 120 can comprise a wavelength variable light generating device configured to generate the second device light 121 in an operational mode of the light generating system 1000 varying between at least two centroid wavelengths (l 2c,1 , l 2c,2 ) having a wavelength difference of at least 10 nm at a variation frequency of at least 40 Hz, in particular at least 50 Hz, such as at least 60 Hz.

[0161] Figures 9A-9B An aspect of possible overlap (emission) bands is schematically shown. The overlap region is indicated with hatching. The percentage of overlap of the smaller band is larger than the percentage of overlap of the larger (here: wider) band. Here, an emission band can be smaller than another emission band in particular when the spectral power (integrated power) of the former is smaller than the latter. In Figure 9A , the overlap can be about 50% (of the narrow band emission) (only about 10% of the wide band emission can overlap with the narrow band emission).

[0162] With reference to Figure 8A , embodiment I, the first light generating device 110 can comprise (a) a wavelength variable first light source 10 configured to generate first light source light 11 in an operational mode of the light generating system 1000 varying between at least two centroid wavelengths (l pc,1 , l pc,2 ) having a wavelength difference of at least 20 nm at a variation frequency of at least 50 Hz. Further, the (first) up-converter material 410 is configured downstream of the wavelength variable first light source 10 and configured to convert at least a portion of the first light source light 11 varying between the at least two centroid wavelengths (l pc,1 , l pc,2 ) into the second device light 121 varying between the at least two centroid wavelengths (l 1c,1 , l 1c,2the first device light 111 varies between at least two centroid wavelengths having a wavelength difference of at least 20 nm.

[0163] The up-converter material 410 can comprise one or more of an up-converter luminescent material and a frequency-doubling material.

[0164] In embodiments, the second light generating device 120 can comprise one or more of a diode laser and a superluminescent diode. In embodiments, the second light generating device 120 can comprise a vertical cavity surface emitting laser (VCSEL).

[0165] Thus, in embodiments of the light generating system 1000, Figure 8D In embodiments II of the light generating system 1000, embodiments are schematically depicted in which the second light generating device 120 comprises a second light source 20 configured to generate second light source light 21 in the operational mode of the light generating system 1000, the second light source light 21 varying between at least two centroid wavelengths having a wavelength difference of at least 20 nm at a variation frequency of at least 50 Hz. Further, the (second) up-converter material 420 is configured downstream of the wavelength- variable second light source 20 and is configured to convert at least part of the second light source light 21 varying between the at least two centroid wavelengths into second device light 121 varying between the at least two centroid wavelengths.

[0166] The first light generating device 110 can be configured to generate first device light 111 having a centroid wavelength in the blue wavelength range, and the second light generating device 120 can be configured to generate second device light 121 having a centroid wavelength in the red wavelength range. Alternatively, the first light generating device 110 can be configured to generate first device light 111 having a centroid wavelength in the red wavelength range, and the second light generating device 120 can be configured to generate second device light 121 having a centroid wavelength in the blue wavelength range.

[0167] In embodiments, the first light source 10 can comprise an IR superluminescent diode or an IR VCSEL.

[0168] The control system (not shown, but see e.g. Figure 9C or Figure 10 ) can be configured to control the first light generating device 110 by pulse width modulation. In particular, the control system can be configured to control the spectral power distribution of the system light 1001 in the operational mode by controlling the duty cycle of the first device light 111.

[0169] The wavelength-variable light generating device can be configured to generate in the operational mode first pulses of the first device light 111 having a centroid wavelength (l 1c,1 ) and second pulses of the first device light 111 having a centroid wavelength (l 1c,2a second pulse of the first device light 111, each pulse having a pulse frequency of at least 40 Hz, wherein controlling the spectral power distribution of the system light 1001 in the operational mode can comprise individually controlling the duty cycle of the first pulse and the duty cycle of the second pulse.

[0170] It is noted that in embodiments the control system can (also) be configured to control the second light generating device by pulse width modulation.

[0171] Reference is made to Figure 10 , schematically showing an example of pulse width modulation. By shortening the pulse width in the second embodiment, the contribution of the light provided in the first type of pulse to the system light is reduced. In this way, the color can be tuned, e.g. along the BBL. The two different pulses represented by the unshaded and shaded rectangles can refer to, e.g., pulses of the first device light having a centroid wavelength λ 1c,1 , λ 1c,2 In this way, the light generating device can scan between two (or more) different spectral power distributions by which the spectral power distribution of the system light can be controlled, in particular with PWM.

[0172] The control system can be configured to control the system light 1001 in an operational mode of the light generating system 1000 to be in the range of 2700-6500 K of correlated color temperature and to have a color rendering index of at least 80.

[0173] Figure 10 One embodiment of a luminaire 2 comprising a light generating system 1000 as described above is schematically shown. Reference 301 denotes a user interface which can be functionally coupled to a control system 300 comprised by the light generating system 1000 or functionally coupled to the light generating system 1000. ​ One embodiment of a lamp 1 comprising a light generating system 1000 is also schematically shown. Hence, ​ An embodiment of a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device, a disinfection device and an optical wireless communication device comprising a light generating system 1000 as described herein is schematically depicted. In embodiments, such lighting device can be a lamp 1, a luminaire 2, a projector device, a disinfection device or an optical wireless communication device. The lighting device light escaping from the lighting device 1200 is denoted by reference 1201. The lighting device light 1201 can essentially consist of the system light 1001 and hence in particular embodiments can be the system light 1001.

[0174] The term “a plurality of” means two or more.

[0175] The terms "substantially" or "essentially" and similar terms in the present text will be understood by the skilled person. The terms "substantially" or "essentially" can also include embodiments with "completely", "entirely", "all" and the like. Thus, in embodiments, the adjective "substantially" or "essentially" can also be removed. Where applicable, the term "substantially" or the term "essentially" can also relate to 90% or more, such as 95% or more, especially 99% or more, even more especially 99.5% or more, including 100%.

[0176] The term "comprising" also includes embodiments in which the term "comprising" is interpreted as "consisting of".

[0177] The term "and / or" relates especially to one or more of the items referred to before and after "and / or". For example, the phrase "item 1 and / or item 2" and similar phrases can relate to one or more of item 1 and item 2. The term "comprising" can in one embodiment mean "consisting of", but can in another embodiment also mean "including at least the defined species and optionally one or more other species".

[0178] 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 application described herein are capable of operation in other sequences than described or illustrated herein.

[0179] These devices, apparatus or systems can here be described during operation. It will be understood by the skilled person that the application is not limited to methods of operation, or devices, apparatus or systems in operation.

[0180] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0181] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0182] The use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in the claims. Unless otherwise defined, all terminology used herein, including words and phrases other than in the claims, is intended to be interpreted in accordance with the ordinary meaning of such terms under the given circumstances (e.g., dictionary definitions, to the extent applicable), and not electrically or in a manner typically used in the patent or legal context.

[0183] The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0184] The application can be implemented by means of hardware comprising several distinct elements, and by a suitably programmed computer. In the device claim or claims or system claim or claims enumerating several means, several of these means can 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 another aspect, the application (thus) provides a software product, which, when run on a computer, is able to implement a method (embodiment(s)) as described herein.

[0185] The application also provides a control system, which can control an apparatus, device or system, or which can execute a method or process as described herein. Furthermore, the application also provides a computer program product, which, when run on a computer functionally coupled to or comprised by an apparatus, device or system, controls one or more controllable elements of such apparatus, device or system.

[0186] The application also applies to an apparatus, device or system comprising one or more characterising features described in the description and / or shown in the attached drawings. The application further relates to a method or process comprising more characterising features described in the description and / or shown in the attached drawings.

[0187] The various aspects discussed in this patent can be combined to provide additional advantages. Furthermore, those skilled in the art will appreciate that embodiments can be combined and more than two embodiments can be combined. Furthermore, some features can form the basis of one or more divisional applications.

[0188] In particular, the application can provide a combination of a wavelength scanning laser and a phosphor and a second laser. In an embodiment, the wavelength scanning laser can be a red laser and the second laser can be a blue laser, and in another embodiment vice versa.

Claims

1. A light generating system (1000) comprising a first light generating device (110), a second light generating device (120) and a luminescent material (200), wherein: the first light generating device (110) is configured to generate first device light (111); 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 different spectral power distributions; the luminescent material (200) is configured to convert at least part of one or more of the first device light (111) and the second device light (121) into luminescent material light (201); The first light generating device (110) comprises a wavelength variable light generating device configured to generate a first device light (111) in an operating mode of the light generating system (1000), the first device light (111) varying between at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ) having a wavelength difference of at least 10 nm at a variation frequency of at least 50 Hz; and the light generating system (1000) is configured to generate, in the operational mode of the light generating system (1000), white system light (1001) comprising the luminescent material light (201), the first device light (111) and the second device light (121).

2. The light generating system (1000) according to claim 1, wherein the first light generating device (110) comprises one or more of a vertical cavity surface emitting laser, VCSEL, and a superluminescent diode.

3. The light generating system (1000) according to any one of the preceding claims, wherein the first light generating device (110) comprises: (a) a wavelength- variable first light source (10) configured to generate first light source light (11) in an operating mode of the light generating system (1000) varying between the at least two centroid wavelengths (λ pc,1 , λ pc,2 ) with a variation frequency of at least 60 Hz having a wavelength difference of at least 20 nm; and (b) an up-converter material (410) configured downstream of the wavelength- variable first light source (10) and configured to convert at least a portion of the first light source light (11) varying between the at least two centroid wavelengths (λ pc,1 , λ pc,2 ) into the first device light (111) varying between the at least two centroid wavelengths (λ 1c,1 , λ 1c,2 ).

4. The light generating system (1000) according to claim 3, wherein the up-converter material (410) comprises one or more of an up-converter luminescent material and a frequency doubling material.

5. The light-generating system (1000) according to claim 1 or 2, wherein the light-emitting material (200) comprises A3B5O. 12 Ce-type luminescent materials, wherein A includes one or more of Y, La, Gd, Tb and Lu, and wherein B includes one or more of Al, Ga, In and Sc.

6. The light generating system (1000) according to claim 1 or 2, comprising a ceramic body (210), wherein the ceramic body (210) comprises the luminescent material (200).

7. The light generating system (1000) according to claim 1 or 2, wherein the second light generating device (120) comprises one or more of a diode laser and a superluminescent diode.

8. The light generating system (1000) according to claim 1 or 2, wherein the second light generating device (120) comprises a wavelength variable light generating device configured to generate second device light (121) in an operational mode of the light generating system (1000), the second device light (121) varying between the at least two centroid wavelengths (λ 2C,1 , λ 2C,2 ) having a wavelength difference of at least 10 nm at a variation frequency of at least 50 Hz.

9. The light generating system (1000) according to claim 1 or 2, wherein: the first light generating device (110) is configured to generate first device light (111) having a centroid wavelength in a blue wavelength range, and wherein the second light generating device (120) is configured to generate second device light (121) having a centroid wavelength in a red wavelength range; or the first light generating device (110) is configured to generate first device light (111) having a centroid wavelength in a red wavelength range, and wherein the second light generating device (120) is configured to generate second device light (121) having a centroid wavelength in a blue wavelength range.

10. The light generating system (1000) according to claim 1 or 2, further comprising a control system (300) configured to control the system light (1001) in dependence on one or more of an input signal of a user interface, a sensor signal and a timer, by individually controlling the first light generating device (110) and the second light generating device (120).

11. The light generating system (1000) according to claim 10, wherein the control system (300) is configured to control the first light generating device (110) by pulse width modulation, wherein the control system is configured to control the spectral power distribution of the system light (1001) in the operational mode by controlling the duty cycle of the first device light (111).

12. The light generating system (1000) according to claim 11, wherein the wavelength- variable light generating device is configured to generate, in the operational mode, first pulses of first device light (111) having a centroid wavelength (λ 1c,1 ) and second pulses of first device light (111) having a centroid wavelength (λ 1c,2 ), each pulse having a pulse frequency of at least 50 Hz, wherein controlling the spectral power distribution of the system light (1001) in the operational mode comprises individually controlling a duty cycle of the first pulses and a duty cycle of the second pulses.

13. The light-generating system (1000) according to claim 1 or 2, wherein the light-emitting material (200) comprises A3B5O. 12 The light-emitting material is of the Ce type, wherein A includes one or more of Y, La, Gd, Tb and Lu, and wherein B includes one or more of Al, Ga, In and Sc; the light-generating system (1000) includes a ceramic body (210), wherein the ceramic body (210) includes the light-emitting material (200); wherein the second light-generating device (120) includes one or more of a diode laser and a superluminescent diode; wherein the first light-generating device (110) is configured to generate a first device light (111) having a centroid wavelength in the blue wavelength range, and wherein the second light-generating device (120) is configured to generate a second device light (121) having a centroid wavelength in the red wavelength range.

14. The light generating system (1000) according to claim 10, wherein the control system (300) is configured to control the system light (1001) in an operational mode of the light generating system (1000) to have a correlated color temperature in a range from 2700 K to 6500 K and a color rendering index of at least 80.

15. A light generating device (1200) selected from the group of a lamp (1), a luminaire (2), a projector device, a disinfection device, and an optical wireless communication device, the light generating device (1200) comprising a light generating system (1000) according to claim 1 or 2.

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