WO2021219442A1

WO2021219442A1 - High intensity light source with high cri for low ctt using green laser pumped phosphor

Info

Publication number: WO2021219442A1
Application number: PCT/EP2021/060243
Authority: WO
Inventors: Rifat Ata Mustafa Hikmet; Ties Van Bommel; Olexandr Valentynovych VDOVIN; Robert Van Asselt; Hugo Johan Cornelissen
Original assignee: Signify Holding B.V.
Priority date: 2020-04-30
Filing date: 2021-04-20
Publication date: 2021-11-04

Abstract

The invention provides a light generating device (1000) configured to generate device light (1001), wherein the light generating device (1000) comprises a first light source (110), a second light source (120), and a first luminescent material (210), wherein: the first light source (110) is configured to generate blue first light source light (111) having a first peak wavelength λ₁ selected from the spectral wavelength range of 440- 480 nm, wherein the first light source (110) is a first laser light source (10); the second light source (120) is configured to generate green second light source light (121) having a second peak wavelength λ₂ selected from the spectral wavelength range of 495-570 nm, wherein the second light source (120) is a second laser light source (20); the first luminescent material (210) is configured to convert part of the second light source light (121) into first luminescent material light (211) having a first luminescent material dominant wavelength λ_dL1in the spectral wavelength range of 575-605 nm; the light generating device (1000) is configured to provide in a first operational mode white device light (1001) comprising the first light source light (111), the second light source light (121), and the first luminescent material light (211), with a correlated color temperature selected from the range of equal to or smaller than 3200 K and a color rendering index of equal to or larger than 80.

Description

HIGH INTENSITY LIGHT SOURCE WITH HIGH CRI FOR LOW CTT USING GREEN LASER PUMPED PHOSPHOR

FIELD OF THE INVENTION

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

BACKGROUND OF THE INVENTION

White light sources using a laser diode and a phosphor are known in the art. US2018/0316160, for instance, describes a device and a method for an integrated white colored electromagnetic radiation source using a combination of laser diode excitation sources based on gallium and nitrogen containing materials and light emitting source based on phosphor materials. A violet, blue, or other wavelength laser diode source based on gallium and nitrogen materials may be closely integrated with phosphor materials, such as yellow phosphors, to form a compact, high-brightness, and highly efficient, white light source. The phosphor material is provided with a plurality of scattering centers scribed on an excitation surface or inside bulk of a plate to scatter electromagnetic radiation of a laser beam from the excitation source incident on the excitation surface to enhance generation and quality of an emitted light from the phosphor material for outputting a white light emission either in reflection mode or transmission mode.

SUMMARY OF THE INVENTION

While white LED sources can give an intensity of e.g. up to about 300 lm/mm²; static phosphor converted laser white sources can give an intensity even up to about 20.000 lm/mm². Ce doped garnets (e.g. YAG, LuAG) may be the most suitable luminescent convertors which can be used for pumping with blue laser light as the garnet matrix has a very high chemical stability. Further, at low Ce concentrations (e.g. below 0.5%) temperature quenching may only occur above about 200 °C. Furthermore, emission from Ce has a very fast decay time so that optical saturation can essentially be avoided. In applications, such as automotive, correlated color temperatures above about 5000 K at low CRI are desirable. However, in other applications e.g. light sources with a high CRI, like e.g. at least 90, and a relatively low CCT, like e.g. at maximum 3000 K, may be desirable. For instance, in some applications an intensity higher than 1 GCd/m² with CRI >90 and at lower CCT≤3000K appear desirable. Further, it appears that in present systems there may be still a relatively high heat generation at the phosphor. When increasing the power, this may increase temperature related problems.

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

In a first aspect, the invention provides a light generating device (“device” or “lighting device”) configured to generate device light. Especially, the light generating device comprises a first light source, a second light source, and a first luminescent material. In embodiments, the first light source is configured to generate blue first light source light having a first peak wavelength li. In specific embodiments, first peak wavelength li is selected from the spectral wavelength range of 440-480 nm. In yet further specific embodiments, the first light source is a first laser light source. In embodiments, the second light source is configured to generate green second light source light having a second peak wavelength λ₂. In specific embodiments, the second peak wavelength l2 is selected from the spectral wavelength range of 495-570 nm. In yet further specific embodiments, the second light source is a second laser light source. Yet further, the first luminescent material is configured to convert part of the second light source light into first luminescent material light having a first luminescent material dominant wavelength λdL1 .In specific embodiments, the first luminescent material dominant wavelength λdL is selected from the spectral wavelength range of 575-605 nm. In yet further specific embodiments, the first luminescent material is especially not configured to convert at least part of the first light source light. Further, in embodiments the light generating device may be configured to provide in a first operational mode white device light comprising the first light source light, the second light source light, and the first luminescent material light. Especially, such white device light (in the first operational mode) may have a correlated color temperature selected from the range of equal to or smaller than (about) 3200 K. Alternatively or additionally, in specific embodiments such white device light (in the first operational mode) may have a color rendering index of equal to or larger than 80. Hence, in specific embodiments the invention provides a light generating device configured to generate device light, wherein the light generating device comprises a first light source, a second light source, and a first luminescent material, wherein: (a) the first light source is configured to generate blue first light source light having a first peak wavelength li selected from the spectral wavelength range of 440-480 nm, wherein the first light source is a first laser light source; (b) the second light source is configured to generate green second light source light having a second peak wavelength l2 selected from the spectral wavelength range of 495-570 nm, wherein the second light source is a second laser light source; (c) the first luminescent material is configured to convert part of the second light source light into first luminescent material light having a first luminescent material dominant wavelength λdL1 in the spectral wavelength range of 575-605 nm; and (d) the light generating device is configured to provide in a first operational mode white device light comprising the first light source light, the second light source light, and the first luminescent material light, with a correlated color temperature selected from the range of equal to or smaller than 3200 K and a color rendering index of equal to or larger than 80.

With such device it is possible to provide white light with a relatively high intensity and with a relatively broad range of correlated color temperatures and with a relatively high color rendering index, such as at least 75, like even about 80, or even above, such as at least 85. It is also possible to have such high color rendering index at relatively low CCT, such as 3200 K or lower, like especially 3100 K or lower, like about 3000 K or lower. Further, with the present invention a relatively simple device may be provided which can provide a high power and/or high luminance. Yet further, it appears that less energy may be lost by heat.

As indicated above, the light generating device is configured to generate device light. To this end, the light generating device comprises a first light source, a second light source, and a first luminescent material. In embodiments, the device light may be white light (especially in the first operation mode). However, in specific embodiments the device may also be configured to generate, in other operational modes, colored device light.

As indicated above, in embodiments the light generating device comprises a first light source configured to generate blue first light source light. Hence, the first light source light may have a color point in the blue. Especially, the first light source comprises a first laser light source. The first laser light source is especially configured to generate first laser light source light. The first light source light may in embodiments essentially consist of the first laser light source light. Hence, in embodiments the first light source is a first laser light source. In embodiments, the term “first light source” may also refer to a plurality of the same first light sources. In embodiments, a bank of first laser light sources may be applied. Alternatively or additionally, the term “first light source” may also refer to a plurality of different first light sources. In embodiments, the term “first laser light source” may also refer to a plurality of the same first laser light sources. Alternatively or additionally, the term “first laser light source” may also refer to a plurality of different first laser light sources.

As indicated above, the light generating device comprises a second light source configured to generate green second light source light. Hence, the second light source light has a color point in the green. Especially, the second light source comprises a second laser light source. The second laser light source is especially configured to generate second laser light source light. The second light source light may in embodiments essentially consist of the second laser light source light. Hence, in embodiments the second light source is a second laser light source. In embodiments, the term “second light source” may also refer to a plurality of the same second light sources. In embodiments, a bank of second laser light sources may be applied. Alternatively or additionally, the term “second light source” may also refer to a plurality of different second light sources. In embodiments, the term “second laser light source” may also refer to a plurality of the same second laser light sources. Alternatively or additionally, the term “second laser light source” may also refer to a plurality of different second laser light sources.

As will be further elucidated below, the light generating device also comprises a third light source. The third light source is configured to generate red third light source light. Hence, the third light source light has a color point in the red. Especially, the third light source comprises a third laser light source. The third laser light source is especially configured to generate third laser light source light. The third light source light may in embodiments essentially consist of the third laser light source light. Hence, in embodiments the third light source is a third laser light source. In embodiments, the term “third light source” may also refer to a plurality of the same third light sources. In embodiments, a bank of third laser light sources may be applied. Alternatively or additionally, the term “third light source” may also refer to a plurality of different third light sources. In embodiments, the term “third laser light source” may also refer to a plurality of the same third laser light sources. Alternatively or additionally, the term “third laser light source” may also refer to a plurality of different third laser light sources.

In embodiments, laser light sources may be arranged in a laser bank. The laser bank may in embodiments comprise heat sinking and/or optics e.g. a lens to collimate the laser light. A laser bank may e.g. comprise at least 10, such as at least 20 laser light sources. In embodiments the laser bank may comprise the first light source. (s) Alternatively or additionally, the laser bank may comprise the second laser light source(s). Alternatively or additionally, the laser bank may comprise the (optional) third light source(s).

Herein, the terms “violet light” or “violet emission” especially relates to light having a wavelength in the range of about 380-440 nm. The terms “blue light” or “blue emission” especially relates to light having a wavelength in the range of about 440-495 nm (including some violet and cyan hues). The terms “green light” or “green emission” especially relate to light having a wavelength in the range of about 495-570 nm. The terms “yellow light” or “yellow emission” especially relate to light having a wavelength in the range of about 570-590 nm. The terms “orange light” or “orange emission” especially relate to light having a wavelength in the range of about 590-620 nm. The term “amber” may refer to one or more wavelengths selected from the range of about 585-605 nm, such as about 590- 600 nm. The terms “red light” or “red emission” especially relate 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 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.

Here below, some aspects in relation to the first light source, the second light source, and the (optional) third light source, are discussed. The first light source, the second light source, and the third light source may be individually chosen and are thus not necessarily of the same type (notwithstanding the fact that the first light source, the second light source, and the third light source are by definition different as the spectral power distributions mutually differ). Hence, the spectral power distributions of the first light source light, the second light source, and the third light source light mutually differ.

In specific embodiments, colors or color points (or spectral power distributions) of a first type of light and a second type of light may be different when the respective color points of the first type of light and the second type of light differ with at least 0.01 for u’ and/or with least 0.01 for v’, even more especially at least 0.02 for u’ and/or with least 0.02 for v’. In yet more specific embodiments, the respective color points of first type of light and the second type of light may differ with at least 0.03 for u’ and/or with least 0.03 for v’. Here, u’ and v’ are color coordinate of the light in the CIE 1976 UCS (uniform chromaticity scale) diagram.

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

In embodiments, a COB is a multi LED chip configured together as a single lighting module. The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 solid state light sources. In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid-state light source, such as a LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise a LED with on-chip optics. In embodiments, the light source comprises a pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering). The term “laser light source” especially refers to a laser. Such laser may especially be configured to generate laser light 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.

Especially, in embodiments the term “laser” may refer to a solid-state laser.

Hence, in embodiments the light source comprises a laser light source. In embodiments, the terms “laser” or “solid state laser” may refer to one or more of cerium doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), chromium doped chrysoberyl (alexandrite) laser, chromium ZnSe (CnZnSe) laser, divalent samarium doped calcium fluoride (Sm:CaF2) laser, Er:YAG laser, erbium doped and erbium-ytterbium codoped glass lasers, F-Center laser, holmium YAG (Ho:YAG) laser, Nd:YAG laser,

NdCrY AG laser, neodymium doped yttrium calcium oxoborate Nd:YCa₄0(B0₃)₃ or Nd:YCOB, neodymium doped yttrium orthovanadate (NdiYVCE) laser, neodymium glass (Nd:glass) laser, neodymium YLF (Nd:YLF) solid-state laser, promethium 147 doped phosphate glass (147Pm³⁺:glass) solid-state laser, ruby laser (Al₂0₃:Cr³⁺), thulium YAG (Tm:YAG) laser, titanium sapphire (Trisapphire; Al₂0₃:Ti³⁺) laser, trivalent uranium doped calcium fluoride (U:CaF2) solid-state laser, Ytterbium doped glass laser (rod, plate/chip, and fiber), Ytterbium YAG (Yb:YAG) laser, UΪ₂O₃ (glass or ceramics) laser, etc. In embodiments, the terms “laser” or “solid state laser” may refer to one or more of a semiconductor laser diode, such as GaN, InGaN, AlGalnP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc. A laser may be combined with an upconverter in order to arrive at shorter (laser) wavelengths. For instance, with some (trivalent) rare earth ions upconversion may be obtained or with non-linear crystals upconversion can be obtained. Alternatively, a laser can be combined with a downconverter, such as a dye laser, to arrive at longer (laser) wavelengths. As can be derived from the below, the term “laser light source” may also refer to a plurality of (different or identical) laser light sources. In specific embodiments, the term “laser light source” may refer to a plurality N of (identical) laser light sources. In embodiments, N=2, or more. In specific embodiments, N may be at least 5, such as especially at least 8. In this way, a higher brightness may be obtained. In embodiments, laser light sources may be arranged in a laser bank (see also above). The laser bank may in embodiments comprise heat sinking and/or optics e.g. a lens to collimate the laser light.

The laser light source is configured to generate laser light source light (or “laser light”). The light source light may essentially consist of the laser light source light. The light source light may also comprise laser light source light of two or more (different or identical) laser light sources. For instance, the laser light source light of two or more (different or identical) laser light sources may be coupled into a light guide, to provide a single beam of light comprising the laser light source light of the two or more (different or identical) laser light sources. In specific embodiments, the light source light is thus especially collimated light source light. In yet further embodiments, the light source light is especially (collimated) laser light source light. The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid- state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin.

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

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

The beams (of light source light) may be focused or collimated beams of (laser) light source light. The term “focused” may especially refer to converging to a small spot. This small spot may be at the discrete converter region, or (slightly) upstream thereof or (slightly) downstream thereof. Especially, focusing and/or collimation may be such that the cross-sectional shape (perpendicular to the optical axis) of the beam at the discrete converter region (at the side face) is essentially not larger than the cross-section shape (perpendicular to the optical axis) of the discrete converter region (where the light source light irradiates the discrete converter region). Focusing may be executed with one or more optics, like (focusing) lenses. Especially, two lenses may be applied to focus the laser light source light. Collimation may be executed with one or more (other) optics, like collimation elements, such as lenses and/or parabolic mirrors. In embodiments, the beam of (laser) light source light may be relatively highly collimated, such as in embodiments ≤2° (FWHM), more especially ≤1° (FWHM), most especially ≤0.5° (FWHM). Hence, <2° (FWHM) may be considered (highly) collimated light source light. Optics may be used to provide (high) collimation (see also above).

As indicated above, in embodiments the first light source light may essentially consist of the laser light source light. In further specific embodiments, the first light source light may essentially consist of first laser light source light of one or more essentially identical laser light sources (such as from the same bin). Further, as indicated above, in embodiments the second light may essentially consist of second laser light. In further specific embodiments, the second laser light may essentially consist of second light source light of one or more essentially identical laser light sources (such as from the same bin). Further, as indicated above, in embodiments the third light source light may essentially consist of the laser light source light. In further specific embodiments, the third light source light may essentially consist of third laser light source light of one or more essentially identical laser light sources (such as from the same bin).

In specific embodiments, the first light source is configured to generate blue first light source light having a first peak wavelength li selected from the spectral wavelength range of 440-480 nm. As indicated above, the first light source is especially a first laser light source. In specific embodiments, the first peak wavelength may be selected from the spectral wavelength range of 450-475 nm, especially selected from the spectral wavelength range of 455-475 nm. The wavelength around 470 nm (±5 nm) appears surprisingly to provide, especially in combination with the first luminescent material light, the second light source light, and the optional third light source light, relatively high CRI and/or desirable color temperatures in a relatively efficient way. In specific embodiments, the second light source is configured to generate green second light source light having a second peak wavelength l2 selected from the spectral wavelength range of 495-570 nm. As indicated above, the second light source is especially a second laser light source. Especially then, (the configuration may be chosen such that) conversion by the luminescent material (see also below) is less than 100%. Hence, at least part of the second light source light may be available in the device light. In specific embodiments, the second peak wavelength may be selected from the spectral wavelength range of 515-545 nm, especially selected from the spectral wavelength range of 530-545 nm, such as 530-540 nm. The wavelength around 535 nm (±5 nm) appears surprisingly to provide, especially in combination with the first luminescent material light, the first light source light, and the optional third light source light, relatively high CRI and/or desirable color temperatures in a relatively efficient way. In specific embodiments, the third light source is configured to generate red third light source light having a third peak wavelength l₃, in specific embodiments selected from the spectral wavelength range of 620-675 nm, such as 625-675 nm, even more especially 630-670 nm. As indicated above, especially the third light source is a third laser light source. In specific embodiments, the third peak wavelength l3 is selected from the spectral wavelength range of 635-665 nm, like especially selected from the spectral wavelength range of 640-665. The wavelength around 650 nm (±5 nm) appears surprisingly to provide, especially in combination with the first luminescent material light, the first light source light, and the second light source light, relatively high CRI and/or desirable color temperatures in a relatively efficient way.

As indicated above, the light generating device comprises a first luminescent material. Optionally, the light generating device may also comprise a second luminescent material. General remarks (embodiments) below in relation to the first luminescent material may also apply to the second luminescent material (and vice versa). The term “luminescent material” herein especially relates to inorganic luminescent materials, which are also sometimes indicated as phosphors. These terms are known to the person skilled in the art. In embodiments, quantum dots and/or organic dyes may be applied, and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc. etc. Quantum dots are small crystals of semiconducting material generally having a width or diameter of only a few nanometers. When excited by incident light, a quantum dot emits light of a color determined by the size and material of the crystal. Light of a particular color can therefore be produced by adapting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with a shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium free quantum dots such as indium phosphide (InP), and copper indium sulfide (CuInSi) and/or silver indium sulfide (AglnSi) can also be used. Quantum dots show very narrow emission band and thus they show saturated colors. Furthermore, the emission color can easily be tuned by adapting the size of the quantum dots. Any type of quantum dot known in the art may be used in the present invention. However, it may be preferred for reasons of environmental safety and concern to use cadmium-free quantum dots or at least quantum dots having a very low cadmium content. Instead of quantum dots or in addition to quantum dots, also other quantum confinement structures may be used. The term “quantum confinement structures” should, in the context of the present application, be understood as e.g. quantum wells, quantum dots, quantum rods, tripods, tetrapods, or nano-wires, etcetera. Organic phosphors can be used as well. Examples of suitable organic phosphor materials are organic luminescent materials based on perylene derivatives, for example compounds sold under the name Lumogen® by BASF. Examples of suitable compounds include, but are not limited to, Lumogen® Red F305, Lumogen®

Orange F240, Lumogen® Yellow F083, and Lumogen® F170.

As indicated above, the light generating device especially further comprises a first luminescent material configured to convert at least part of the first light source light into first luminescent material light having an emission band having wavelengths in one or more of (a) the green spectral wavelength range and (b) the yellow spectral wavelength range.

The term “luminescent material” especially refers to a material that can convert first radiation, especially (one or more of UV radiation and) blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the second radiation has a spectral power distribution at larger wavelengths than the first radiation, which is the case in the so-called down-conversion. In specific embodiments, however the second radiation has a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up-conversion. In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and/or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation and blue radiation, into visible light. The luminescent material may in specific embodiments also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. In general, the luminescent material will be a down converter, i.e. radiation of a smaller wavelength is converted into radiation with a larger wavelength (λ_ex<λ_em). In specific embodiments the luminescent material may comprise down-converter luminescent material, i.e. radiation of a larger wavelength is converted into radiation with a smaller wavelength (λ_ex<λ_em). In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and/or fluorescence. The term “luminescent material” may also refer to a plurality of different luminescent materials. The term “luminescent material” herein may also refer to a material comprising a luminescent material, such as a light transmissive host comprising the luminescent material.

Especially, the first luminescent material is configured to convert part of the green first light source light into first luminescent material light having an emission band having wavelengths in one or more of the yellow, amber, orange and red. Further, especially the first luminescent material light has one or more wavelengths in the range of about 570- 870 nm. Further, in specific embodiments the first luminescent material light has a full width half maximum (FWHM) of at least 25 nm, such as at least 40 nm, like in specific embodiments up to about 60 nm (at room temperature), though larger may be possible. A broad band may provide a higher CRI. Especially, the first luminescent material light has a color point in the orange-red, especially in the orange. Especially, in embodiments the first luminescent material light has a dominant wavelength ( λdL1) selected from the spectral wavelength range of 575-605 nm, more especially selected from the spectral wavelength range of 580-600 nm. Especially, the first luminescent material light has a color point in the amber and/orange. Especially, in embodiments the first luminescent material light has a dominant wavelength (λdL1) selected from the spectral wavelength range of 575-605 nm, more especially selected from the spectral wavelength range of 580-600 nm. Especially, at least 50% of the spectral power (in Watt) of the first luminescent material light, such as at least 70%, is within the range of 550-650 nm. The first luminescent material light may e.g. have a dominant wavelength in the amber and/or orange wavelength range. Examples of such first luminescent material may e.g. be M₂Si₅N₈:Eu²+ and/or MAlSiN3:Eu²⁺ and/or Ca₂AlSi₃0₂N₅:Eu²⁺, etc., wherein M comprises one or more of Ba, Sr and Ca, especially in embodiments at least Sr.

Hence, in embodiments, first luminescent may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu²⁺). For instance, assuming 2% Eu in CaAlSiN3:Eu, the correct formula could be (Cao_.98Eu_0.02)AlSiN₃. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr or Ba. The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Further, the material (Ba,Sr,Ca)2SisN8:Eu can also be indicated as MiSFNxHu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not taking into account the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Bai_.sSro_.sSisNsiEu (i.e. 75 % Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca). Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSiN3:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.

As indicated above, other first luminescent materials may also be possible. Hence, in specific embodiments the first luminescent material is selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures. Quantum structures may e.g. comprise quantum dots or quantum rods (or other quantum type particles) (see above). Quantum structures may also comprise quantum wells. Quantum structures may also comprise photonic crystals.

The lighting device may provide device light during operation. The device light may comprise the first light source light, the second light source light, and the first luminescent material light (in one or more operational modes). In embodiments, the first light source, the second light source, the first luminescent material, are chosen such that white device light may be generated. Hence, in specific embodiments the lighting device is configured to generate (in one or more modes of operation) (white) device light comprising the first light source light, the second light source light and the first luminescent material light. Hence, in embodiments white device light may be generated, comprising the first light source light, the second light source light and the first luminescent material light, with a correlated color temperature selected from the range of equal to or smaller than 3200 K and a color rendering index of equal to or larger than 80. For instance, the CCT may be selected from the range of 1800-3200 K (see also below).

In specific embodiments, the first luminescent material dominant wavelength λ_{dL 1} is selected from the range of 585-600 nm, like at least 588 nm, more especially 590-600 nm. Such embodiments may even allow generating of white device light even without the use of red source of light (such as a red luminescent material and/or a red solid state based light source). Hence, in specific embodiments in the first operational mode the white device light consists of the first light source light, the second light source light, and the first luminescent material light. Especially, the white device light has a CRI of at least 80, such as at least 85, like even at least 90. In embodiments, the device light may even have a CRI of at least 93, such as at least 95.

For instance, in embodiments without additional red light, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 4-20% of the (blue) first light source light, like up to about 19% of the first light source light, like in the range of 4-19%, such as especially in the range of 5-18%, of the first light source light, such as at least about 6%. Further, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 4-30% of the (green) second light source light, like up to about 25% of the first light source light, like in the range of 4-25%, such as especially in the range of 7-23%, of the first light source light, such as at least about 9%. Yet further, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 50-90% of the orange first luminescent material light, like up to about 85% of the first light source light, and/or at least about 55%, like in the range of 55-85%, such as especially in the range of 60-85%, of the first light source light, such as at least about 61%, like in the range of about 61-82%. Here, the percentage are based on the optical watts.

The device light may comprise the first light source light, the second light source light, the first luminescent material light, and one or more of the second luminescent material and the third light source light. In embodiments, the first light source, the second light source, the first luminescent material, and one or more of the second luminescent material and the third light source light, are chosen such that white device light may be generated. Hence, in specific embodiments the lighting device is configured to generate (in one or more modes of operation) (white) device light comprising the first light source light, the second light source light, the first luminescent material light, and one or more of the second luminescent material and the third light source light. Hence, in white device light may be generated comprising (i) the first light source light, (ii) the second light source light, (iii) the first luminescent material light, and (iv) one or more of the third light source light and the second luminescent material light, with a correlated color temperature selected from the range of equal to or smaller than 3200 K and a color rendering index of equal to or larger than 80.

In specific embodiments, the first luminescent material dominant wavelength λ_dL1 is selected from the range of 580-590 nm. Such embodiments may even allow generating of white device light especially with the use of red source of light (such as a red luminescent material and/or a red solid state based light source). Hence, in embodiments the light generating device may further comprise one or more of: (a) the third light source configured to generate red third light source light having a third peak wavelength λ₃ selected from the spectral wavelength range of 620-675 nm, such as 625-675 nm, wherein the third light source is a third laser light source; and (b) a second luminescent material configured to convert part of the first light source light and/or second light source light into second luminescent material light having a second luminescent material dominant wavelength λ_dL2 in the spectral wavelength range of 620-675 nm, such as 625-675 nm. Hence, in specific embodiments in the first operational mode (or a second operational mode) the white device light consists of the first light source light, the second light source light, the first luminescent material light, and one or more of the second luminescent material light and third light source light. Especially, the white device light has a CRI of at least 80, such as at least 85, like even at least 90. Note that the term “first light source” may also refer to a plurality of (different) first light sources, and/or the term “second light source” may also refer to a plurality of (different) second light sources, and/or the term “third light source” may also refer to a plurality of (different) third light sources. Further, note that the term “second luminescent material” may also refer to a plurality of (different) second luminescent materials.

For instance, in embodiments with additional red light, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 4-20% of the (blue) first light source light, like up to about 17% of the first light source light, like in the range of 4-17%, such as especially in the range of 5-16%, of the first light source light, such as at least about 6%. Further, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 4-30% of the (green) second light source light, like up to about 25% of the first light source light, like in the range of 4-25%, such as especially in the range of 6-23%, of the first light source light, such as at least about 7%. Yet further, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 20-85% of the orange first luminescent material light, like up to about 82% of the first light source light, and/or at least about 25%, like in the range of 25-82%, such as especially in the range of 29-80%, of the first light source light, such as at least about 30%, like in the range of about 32-80%. Further, the device light (escaping from the light generating device) may in embodiments comprise in the range of about 2-65% of the (red) third light source light and/or second luminescent material light, like up to about 60% of the first light source light, like in the range of 4-60%, such as especially in the range of 5-55%, of the first light source light, such as at least about 6%.

In specific embodiments, the CCT may be selected from the range of 2000- 3000 K. The color rendering index may in specific embodiments be selected from the rang of at least 85, like at least 90.

The second luminescent material may be one of the materials described above. Note that the first luminescent material and the second luminescent material may even be of the same or similar type of luminescent materials, as e.g. with different chemical compositions essentially the same type of materials may exhibit orange or red(dish) emission, as is e.g. known for M₂Si₅N8:²⁺ systems (see also above).

Hence, especially the first luminescent material and the second luminescent materials are chemically different luminescent materials and/or include different luminescent species, such as Ce³⁺ and Eu²⁺. Further, especially the spectral power distributions of the first luminescent material light and the second luminescent material light are different (especially differing with at least 0.01 for u’ and/or with least 0.01 for v’, see also above).

Note that especially the second luminescent material may not be configured to convert at least part of the first luminescent material light. Hence, the second luminescent material may one or more of (a) essentially not absorb at the wavelengths of the first luminescent material light, and (b) not be configured downstream of the first luminescent material. However, configuration may also be possible where the second luminescent material absorbs up to about 15%, such as up to about 10% of the first luminescent material light.

In embodiments, the second luminescent material light may be green light. In yet other embodiments, the second luminescent material light is red light. In yet further embodiments, two or more different luminescent materials are applied, having different spectral power distributions of the respective second luminescent material lights.

The term “white light” herein, is known to the person skilled in the art. It especially relates to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700-20000 K, for general lighting especially in the range of about 2700 K and 6500 K. In embodiments, for backlighting purposes the correlated color temperature (CCT) may especially be in the range of about 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL. Hence, in specific embodiments the device light has a correlated color temperature selected from the range of 2000-5000 K, such as 2000-4000 K, on or within 10 SDCM from the black body locus. In specific embodiments, the lighting device may be configured to generate (in one or more operation modes) white device light having a color rendering index selected from the range of at least 80 and having a correlated color temperature selected from the range of 1800-3200 K, like 2000-3100 K, such as at least 2000 K, like up to 3000 K. In specific embodiments, the CRI may be at least 85, even more especially at least 90.

Further, in specific embodiments the light generating device may comprise a control system configured to control one or more of the light sources. In specific embodiments, the control system is configured to control one or more optical properties of the device light, especially in further embodiments in dependence of a user interface, a sensor signal, and a timer. In specific embodiments, the one or more optical properties include the correlated color temperature and the color rendering index.

The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation”. The term “mode” may also be indicated as “controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed. However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability). Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme. See further also below. Especially, there may be a plurality of modes of operation, such as at least two, like at least three, such as at least five, like at least 8, such as at least 16. A change between the modes of operation may be stepwise or stepless. Control can be analogical or digital. The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc... Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface. The control system may also be configured to receive and execute instructions form a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc... The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system. Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, LiFi, WIFI, ZigBee, BLE or WiMAX, or another wireless technology.

The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

In specific embodiments, the light generating device may be comprise a control system configured to control the first light source, the third light source, and the optional second light source. This may allow controlling the correlated color temperature and/or the color rendering index, and/or the color point of the device light. Hence, in specific embodiments the light generating device may further comprise a control system, wherein the control system is configured to control one or more of the correlated color temperature and the color rendering index of the device light by controlling the first light source, the second light source, and optionally the third light source (when available). In even more specific embodiments the control system is configured to keep in a controlling mode the color rendering index over 85, even more especially at at least 90, and the correlated color temperature within the range of 1800-3200 K, especially in the range of 2000-3000 K. Further, the control system may control optional further light sources.

It may be desirable to (further) shape the device light into a beam of device light. Alternatively or additionally, it may be desirable to (further) homogenize the device light (into homogenized device light). To this end, an (beam shaping) optical element may be used. Hence, in embodiments the light generating device may further comprise an (beam shaping) optical element configured to beam shape the device light and/or configured to homogenize the device light. Especially, the (beam shaping) optical element is configured downstream of the first luminescent material. Further, the (beam shaping) optical element(s) may be configured downstream from one or more first light source and downstream of the second light source. Further, the (beam shaping) optical element may be configured downstream from the optional third light source and/or downstream of optional second luminescent material.

The (beam shaping) optical element may especially comprise a collimator used to convert (to “collimate”) a beam of light (to be (further) beam shaped) into a beam having a desired angular distribution. In embodiments, the (beam shaping) optical element may especially comprises a light transmissive body. Hence, the (beam shaping) optical element may be a body of light transmissive material that is configured to collimate the (to be (further) beam shaped). In specific embodiments, the (beam shaping) optical element comprises a compound parabolic like collimator, such as a CPC (compound parabolic concentrator). A massive collimator, such as a massive CPC, may especially be used as extractor of light (to be (further) beam shaped) and to collimate the light (to be (further) beam shaped). Alternatively or additionally, one or more lenses may be used for beam shaping light (to be (further) beam shaped). In this way, the device light may be beam shaped. The optical element may have a beam shaping function. Alternatively or additionally, it may have a homogenization and/or mixing function. Especially, this may be the case when using a collector, such as a CPC.

Here, the light (to be (further) beam shaped) especially refers to the one or more components of the device light, such as e.g. the first light source light, the second light source light, and first luminescent material light.

Further, the shape of the cross-section of the (beam shaping) optical element may vary with position along the optical axis. In a specific configuration, the aspect ratio of a rectangular cross-section may change, preferably monotonically, with position along the optical axis. In another preferred configuration, the shape of the cross-section of the (beam shaping) optical element may change from round to rectangular, or vice versa, with position along the optical axis.

Alternatively or additionally, the light generating device may comprise an optical element for combining two or more beams of light. Especially, the (beam combining) optical element may (then) be configured to combine two or more of (i) first light source light, (ii) the second light source light, (iii) the first luminescent material light, and optionally (iv) the third light source light and/or the second luminescent material light. In specific embodiments, the optical element may comprise one or more of (i) a dichroic beam combiner and (ii) an optical homogenizer (see also above where the beam shaping element is discussed). The dichroic beam combiner may in embodiments comprise a dichroic prism. A dichroic beam combiner may also be used to transmit a first type of light and to reflect a second type of light wherein tan optical axis of the transmitted first type of light and an optical axis of the second type of light may substantially coincide downstream of the dichroic beam combiner. Embodiments of a homogenizer are also indicated above. In embodiments, two or more dichroic beam combiners may be applied, for instance to introduce into the beam two or more of the first light source light, the second light source light, the first luminescent material light, and one or more of the optional third light source light and second luminescent material light.

Hence, in specific embodiments the light generating device may further comprise an optical element configured to combine the first light source light, the second light source light, and the first luminescent material light, wherein the first luminescent material is configured downstream of the second light source and is not configured downstream of the first light source. In specific embodiments, the light generating device may comprising a plurality of (such) optical elements, wherein the optical elements comprise one or more of dichroic mirrors and a cross-dichroic prism (X-cube), and wherein the plurality of optical elements are configured to combine the first light source light, (ii) the second light source light, (iii) the first luminescent material light, and optionally (iv) the third light source light as defined herein. Hence, in embodiments the optical elements may comprise one or more of a dichroic mirror and a cross-dichroic prism. More especially, embodiments the optical elements may comprise one or more dichroic mirrors and one or more cross-dichroic prisms. Hence, one or more optical elements may be configured to combine one or more beams of light and/or to beam shape the device light. The term “optical element” may also refer to a plurality of (different) optical elements.

During operation of the light generating device, it is not necessary that all types of light are available. This may depend e.g. on the mode of operation, such as whether or not white light or whether or not colored light is provided, or it may depend upon the correlated color temperature.

In specific embodiments, all second light source light that is comprised by the device light is one or more of (i) reflected, (ii) scattered, and (iii) transmitted by the first luminescent material. Note that there may also be more than one second light sources, of which one or more are radiationally coupled with the first luminescent material and one or more other light sources bypass the first luminescent material with their second light source light. Hence, at least part of the second light source light that is comprised by the device light may be one or more of (i) reflected, (ii) scattered, and (iii) transmitted by the first luminescent material.

In yet other embodiments, the second light source light may be splitted, e.g. with a beam splitter in two or more beams, of which at least one is used to irradiate the first luminescent material. Further, at least one may be directly introduced as component of the device light, without essentially any interaction with the first luminescent material. The same may in embodiments apply for the light source light that is used to irradiate the optional second luminescent material.

In embodiments, the first light source light does not have essentially any interaction with the first luminescent material, as it may be added to the first luminescent material light, i.e. downstream of the first luminescent material. Hence, in specific embodiments the first light source may be configured downstream of the first luminescent material, and the light generating device is configured to combine the first light source light and the first luminescent material light (downstream of the first luminescent material). To this end, also (optional) (second) optics may be applied, like a dichroic mirror (dichroic beam combiner). Especially, in (other) embodiments the first luminescent material is transmissive for at least part of the first light.

With respect to the optional third light source, the third light source light may in embodiments (also) be one or more of (i) reflected, (ii) scattered, and (iii) transmitted by the first luminescent material (see further also below). However, in (other) embodiments the third light source light (also) does not have essentially any interaction with the first luminescent material, as it may be added to the first luminescent material light, i.e. downstream of the first luminescent material. Hence, in specific embodiments the third light source is configured downstream of the first luminescent material, and the light generating device is configured to combine the third light source light and the first luminescent material light (downstream of the first luminescent material). To this end, also (optional) optics may be applied, like a dichroic mirror (dichroic beam combiner).

With respect to the optional second luminescent material light, this may be generated by the second luminescent material that is pumped with one or more of the first light source light, the second light source light, and other light source light.

Hence, one or more first light sources may be configured to generate the second luminescent material light. In such embodiments the second luminescent material may convert at least part of the first light source light. In yet other embodiments, one or more first light sources are radiationally coupled with the second luminescent material and one or more (other) first light sources are configured to bypass the second luminescent material (and optionally also the first luminescent material) with their first light source light. Hence, in specific embodiments the light generating device may comprise a plurality of first light sources, wherein a first set of one or more first light sources are configured upstream of the second luminescent material, and wherein a second set of one or more first light sources are configured to provide first light source light that bypasses the second luminescent material.

Alternatively or additionally, one or more second light sources may be configured to generate the second luminescent material light. In such embodiments the second luminescent material may convert at least part of the second light source light. In yet other embodiments, one or more second light sources are radiationally coupled with the second luminescent material and one or more (other) second light sources are configured to bypass the second luminescent material (and also the first luminescent material) with their second light source light.

It may also be possible to use yet other light sources to pump the second luminescent material, such as e.g. a UV light source though also a visible light generating light source may be envisaged. In such embodiments the second luminescent material may be configured to essentially convert all other light source light.

The term “first light source light” and similar terms especially indicate the light generated by a first light source. Likewise, the term “second light source light” and similar terms especially indicate the light generated by a second light source. Also, the term “third light source light” and similar terms especially indicate the light generated by a third light source.

The first luminescent material may be comprised by a body. Especially, in embodiments such body is a light transmissive body, such as in specific embodiments a light transparent body. Such body may be indicated as luminescent body. In embodiments, the luminescent body may thus be at least partially transmissive for visible light.

Hence, in embodiments the first luminescent material may be comprised or be configured as a light transmissive body, such as in specific embodiments a light transparent body. In such embodiments, the second light source may be configured upstream of the light transmissive body. Therefore, in specific embodiments the light transmissive body may be transmissive for at least part of the second light source light. Hence, the light transmissive body may be configured downstream of the second light source. During the one or more operational modes at least part of the second light source light may be transmitted through the light transmissive body to provide transmitted second light source light. Further, at least part of the second light source may be converted by the first luminescent material into first luminescent material light.

As indicated above, would such body be transmissive for at least part of the first light source light, the first light source could be configured upstream of the luminescent body. However, as also indicated above, in embodiments the first light source may be configured to bypass the luminescent body with its first light source light.

Further, would such body be transmissive for at least part of the optional third light source light, the optional third light source could be configured upstream of the luminescent body. However, as also indicated above, in embodiments the third light source may be configured to bypass the luminescent body with its third light source light.

Further embodiments in relation to luminescent bodies are described below.

The optional second luminescent material may be comprised by another luminescent body. Further embodiments in relation to luminescent bodies are described below.

In specific embodiments, however, the optional second luminescent material may be comprised by the same luminescent body as the first luminescent material.

In such embodiments, the second light source may be configured upstream of the light transmissive body. Therefore, in specific embodiments the light transmissive body may be transmissive for at least part of the second light source light. Hence, the light transmissive body may be configured downstream of the second light source. During the one or more operational modes at least part of the second light source light may be transmitted through the light transmissive body to provide transmitted second light source light. Further, at least part of the second light source may be converted by the first luminescent material into first luminescent material light.

As indicated above, would such body be transmissive for at least part of the first light source light, the first light source could be configured upstream of the luminescent body. However, as also indicated above, in embodiments the first light source may be configured to bypass the luminescent body with its first light source light. Hence, in specific embodiments, the luminescent body may further comprise the second luminescent material. Especially, in (such) embodiments the light generating device may in further embodiments comprise a plurality of first light sources, wherein a first set of one or more first light sources are configured upstream of the luminescent body, and wherein a second set of one or more first light sources are configured to provide first light source light that bypasses the luminescent body.

Especially, in embodiments the light generating device may comprise a luminescent body, wherein the luminescent body may comprise the first luminescent material. In such embodiments, it may also be possible to pump with a plurality of first light sources the luminescent body. This may further increase the output of the light generating device. Hence, in yet further specific embodiments the light generating device may comprise a plurality of first light sources, wherein the plurality of first light sources are configured to irradiate the luminescent body with the first light source light. Instead of the term “luminescent body”, and similar terms, also the term “light transmissive body”, and similar terms, may be applied, as the luminescent body is also transmissive for the first luminescent material light.

As indicated above, the light generating system especially comprises in embodiments a luminescent body. The luminescent body may comprise (N) side faces (over at least part of the length L), wherein N>3. Hence, especially the luminescent body has a cross-sectional shape that is square (N=4), rectangular (N=4), hexagonal (n=6), or octagonal (n=8), especially rectangular. Would the luminescent body have a circular cross-section, N may be considered ¥. The (elongated) body includes a first end or first face, in general configured perpendicular to one or more of the (n) side faces and a second end or second face, which may be configured perpendicular to one or more of the side faces, and thus parallel to the first face, but which also may be configured under an angle unequal to 90° and unequal to 180°. Hence, in embodiments in specific embodiments the radiation exit window has an angle unequal to 0° and unequal to 180° with one or more of the one or more side faces, especially all of the side faces. Note that the angle a may differ per for different side faces. For instance, a slanted radiation exit window of a bar shaped elongated body may have an angle of al with a first side face, an angle a2=180°-al with a second side face, and angles of 90° with the two other side faces. The (elongated) luminescent body may thus in embodiments include (n) side faces, which comprise a first side face, comprising a radiation input face, and a second side face configured parallel to the first side face, wherein the side faces define a height (H). The first and the second side face are configured parallel with luminescent body material in between, thereby defining the width of the luminescent body. The radiation input face is at least part of the first face which may be configured to receive the light source light. The (elongated) luminescent body further comprises a radiation exit window bridging at least part of the height (H) between the first side face and the second side face. Especially, the radiation exit window is comprised by the second face. Further embodiments are also elucidated below. As indicated above, in embodiments the radiation exit window and the radiation input face have an angle (a) unequal to 0° and unequal to 180°. Yet further, as also indicated above in embodiments the radiation exit window has an angle unequal to 0° and unequal to 180° with one or more of the one or more side faces.

The light transmissive body has light guiding or wave guiding properties. Hence, the light transmissive body is herein also indicated as waveguide or light guide. As the light transmissive body is used as light concentrator, the light transmissive body is herein also indicated as light concentrator. The light transmissive body will in general have (some) transmission of one or more of (N)UV, visible and (N)IR radiation, such as in embodiments at least visible light, in a direction perpendicular to the length of the light transmissive body. Without the activator (dopant) such as trivalent cerium, the internal transmission in the visible might be close to 100%.

The transmission of the light transmissive body for one or more (first) luminescence wavelengths may be at least 80%/cm, such as at least 90%/cm, even more especially at least 95%/cm, such as at least 98%/cm, such as at least 99%/cm. This implies that e.g. a 1 cm³ cubic shaped piece of light transmissive body, under perpendicular irradiation of radiation having a selected luminescence wavelength (such as a wavelength corresponding to an emission maximum of the luminescence of the luminescent material of the light transmissive body), will have a transmission of at least 95%. Hence, the luminescent body is herein also indicated “light transmissive body”, as this body is light transmissive for the luminescent material light. Herein, values for transmission especially refer to transmission without taking into account Fresnel losses at interfaces (with e.g. air). Hence, the term “transmission” especially refers to the internal transmission. The internal transmission may e.g. be determined by measuring the transmission of two or more bodies having a different width over which the transmission is measured. Then, based on such measurements the contribution of Fresnel reflection losses and (consequently) the internal transmission can be determined. Hence, especially, the values for transmission indicated herein, disregard Fresnel losses. In embodiments, an anti-reflection coating may be applied to the luminescent body, such as to suppress Fresnel reflection losses (during the light incoupling process). In addition to a high transmission for the wavelength(s) of interest, also the scattering for the wavelength(s) may especially be low. Hence, the mean free path for the wavelength of interest only taking into account scattering effects (thus not taking into account possible absorption (which should be low anyhow in view of the high transmission), may be at least 0.5 times the length of the body, such as at least the length of the body, like at least twice the length of the body. For instance, in embodiments the mean free path only taking into account scattering effects may be at least 5 mm, such as at least 10 mm. The wavelength of interest may especially be the wavelength at maximum emission of the luminescence of the luminescent material. The term “mean free path” is especially the average distance a ray will travel before experiencing a scattering event that will change its propagation direction. The transmission can be determined by providing light at a specific wavelength with a first intensity to the light transmissive body under perpendicular radiation and relating the intensity of the light at that wavelength measured after transmission through the material, to the first intensity of the light provided at that specific wavelength to the material (see also E-208 and E-406 of the CRC Handbook of Chemistry and Physics, 69th edition, 1088-1989).

The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to visible light. The light transmissive body may have any shape, such as beam (or bar) like or rod like, however especially beam like (cuboid like). The light transmissive body, such as the luminescent concentrator, might be hollow, like a tube, or might be filled with another material, like a tube filled with water or a tube filled with another solid light transmissive medium. The invention is not limited to specific embodiments of shapes, neither is the invention limited to embodiments with a single exit window or outcoupling face. Below, some specific embodiments are described in more detail. Would the light transmissive body have a circular cross-section, then the width and height may be equal (and may be defined as diameter). Especially, however, the light transmissive body has a cuboid like shape, such as a bar like shape, and is further configured to provide a single exit window.

In embodiments, one or more of the light source may be configured in a reflective configuration with the luminescent material. Further, in embodiments one or more of the light sources may be configured in a transmissive configuration.

Especially, in embodiments the solid state light source, or other light source, is not in (direct) physical contact with the light transmissive body.

Especially, in embodiments the light transmissive body comprises a radiation input face, configured in a light receiving relationship with the first light source, and a radiation exit face. Especially, in embodiments the radiation input face and the radiation exit face are not the same part of the light transmissive body, though it is not excluded that the same face may be used for providing the radiation input face and the radiation exit face. In specific embodiments, the radiation exit face and the radiation input face are comprises by different faces of the light transmissive body (see further also below).

Hence, the light transmissive body, more especially the radiation input face thereof, is configured downstream of the first light source. Or, in other words, the light transmissive body, more especially the radiation input face thereof, is radiationally coupled with the first light source.

The terms "radiationally coupled" or “optically coupled” may especially mean that (i) a light generating element, such as a light source, and (ii) another item or material, are associated with each other so that at least part of the radiation emitted by the light transmissive body is received by the item or material. In other words, the item or material is configured in a light-receiving relationship with the light transmissive body. At least part of the radiation of light transmissive body will be received by the item or material. This may in embodiments be directly, such as the item or material in physical contact with the (light emitting surface of the) light transmissive body. This may in embodiments be via a medium, like air, a gas, or a liquid or solid light guiding material. In embodiments, also one or more optics, like a lens, a reflector, an optical filter, may be configured in the optical path between light transmissive body and item or material.

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

Hence, the light transmissive body is especially transmissive for at least part of the second light source light propagating from the radiation input face to the radiation exit face. Further, the light transmissive body is especially further configured to convert part of the second light source light propagating through the light transmissive body into first luminescent material light. Light transmissive body are known in the art, such as e.g. described in W02006/054203, which is incorporated herein by reference.

As indicated above, the light transmissive body is especially configured to convert part of the (second) light source light propagating through the light transmissive body into first luminescent material light having a first luminescent material light spectral power distribution differing from the first spectral power distribution of the first light source light. The first luminescent material light may especially be due to down conversion, see also above.

In a specific embodiment, the light transmissive body may especially have an aspect ratio larger than 1, i.e. the length is larger than the width. In general, the light transmissive body is a rod, or bar (beam), or a rectangular plate, though the light transmissive body does not necessarily have a square, rectangular or round cross-section. In general, the light source is configured to irradiate one (or more) of the longer faces (side edge), herein indicated as radiation input face, and radiation escapes from a face at a front (front edge), herein indicated as radiation exit window. The light source(s) may provide radiation to one or more side faces, and optionally an end face. Hence, there may be more than one radiation input face. The generally rod shaped or bar shaped light transmissive body can have any cross-sectional shape, but in embodiments has a cross section the shape of a square, rectangle, round, oval, triangle, pentagon, or hexagon. The radiation exit window may especially have an angle unequal to 0° and unequal to 180° with the radiation input face, such as angle(s) of 90°. Further, in specific embodiments the radiation exit window has an angle unequal to 0° and unequal to 180° with one or more of the one or more side faces, such as angle(s) of 90°. Generally, the (ceramic or crystal) bodies are cuboid. In specific embodiments, the body may be provided with a different shape than a cuboid, with the light input surface having somewhat the shape of a trapezoid. By doing so, the light flux may be even enhanced, which may be advantageous for some applications. Hence, in some instances (see also above) the term “width” may also refer to diameter, such as in the case of a light transmissive body having a round cross section.

In (other) embodiments, the body further has a lateral dimensions width or length (W or L) or diameter (D) and a thickness or height (H). In embodiments, (i) D>H or (ii) and W>H and/or L>H. The luminescent tile may be transparent or light scattering. In embodiments, the tile may comprise a ceramic luminescent material. In specific embodiments, L≤10 mm, such as especially L≤5mm, more especially L≤3mm, most especially L≤2 mm. In specific embodiments, W≤10 mm, such as especially W≤5mm, more especially W≤3mm, most especially W≤2 mm. In specific embodiments, H≤10 mm, such as especially H≤5mm, more especially H≤3mm, most especially H≤2 mm. In specific embodiments, D≤10 mm, such as especially D≤5mm, more especially D≤3mm, most especially D≤2 mm. In specific embodiments, the body may have in embodiments a thickness in the range 50 μm - 1 mm. Further, the body may have lateral dimensions (width/diameter) in the range 100 pm - 10 mm. In yet further specific embodiments, (i) D>H or (ii) W>H and W>H. Especially, the lateral dimensions like length, width, and diameter are at least 2 times, like at least 5 times, larger than the height.

In embodiments, the luminescent material is comprised by or provided as a (light transmissive) body. In embodiment, the luminescent material is comprised by or provided as (light transmissive) layer. The layer may in embodiments also be indicated as body. In specific embodiments, the light generating device comprises a luminescent body, wherein the luminescent body comprises the first luminescent material, and wherein the luminescent body is a ceramic body. Likewise, this may apply to the second luminescent material. In specific embodiments, the body may comprise both the first luminescent material and the second luminescent material. Hence, in embodiments the luminescent body comprises the second luminescent material. Hence, in specific embodiment a ceramic body comprises the first luminescent material and the second luminescent material.

In embodiments, the (first) luminescent is comprised by a single crystal. In (other) embodiments, the (first) luminescent is comprised by a ceramic body. In yet other embodiments, the (first) luminescent is comprised by a polycrystalline material, such as a polycrystalline material layer. This may in embodiments be a powder layer or a compacted powder layer. In specific embodiments, a powder layer or a compacted powder layer may comprise both the first luminescent material and the second luminescent material. Hence, in embodiments a powder layer or a compacted powder layer comprises the second luminescent material. In yet other embodiments, a multi-layer may be applied, wherein a first layer comprises the first luminescent material (and essentially no second luminescent material) and a second layer comprises the second luminescent material (and essentially not the first luminescent material). Herein, “essentially not” may indicate a weight ratio of ≤0.1, such as ≤0.01. Therefore, in yet further specific embodiments the luminescent body may comprises one or more of a ceramic body and a multi-layer material. The multi-layer material may thus comprise the first luminescent material and the second luminescent material, and may in specific embodiments also be a ceramic body.

Light source light of one or more of the light sources may be provided to the first luminescent material in a transmissive configuration or a reflective configuration. When more than one light source is configured to provide light source light to the first luminescent material, the light source light of the two or more of the light sources may be provided to the first luminescent material in a transmissive configuration and a reflective configuration.

In embodiments, a dichroic filter may be configured between the second light source and the first luminescent material, i.e. downstream of the second light source and upstream of the first luminescent material. A dichroic filter may be applied to allow the light source light be transmitted by the dichroic filter and the first luminescent material light to be reflected back. In this way, first luminescent material light propagating in the direction of the second light source, may at least partly be reused.

The dichroic filter and (first) luminescent material may have a non-zero distance, such as e.g. selected from the range of 0.01-10 mm. Without physical contact, especially at a distance of at least about 0.001 mm, there may be less light loss. When there is no dichroic filter (or other optics), in embodiments the (second) light source may have a nonzero distance to the (second) luminescent material, such as e.g. selected from the range of 0.01-10 mm. Without physical contact, especially at a distance of at least about 0.001 mm, there may be less light loss. A non-zero distance may also allow different thermal pathways for the (second) light source and the (first) luminescent material.

One or more heat sinks may be configured in thermal contact with one or more of the first light source, the second light source, the optional third light source, the first luminescent material and the optional second luminescent material. Hence, the invention provides amongst others a high intensity light source with high CRI for low CCT using green laser pumped phosphor.

The luminous efficiency of the white device (light) may in embodiments be selected from the range of 290-370 Lm/W, such as 300-360 Lm/W. In embodiments, the light generating device is configured to provide the luminescent light with power emitted from a radiation exit face of the luminescent body having a power density of 4 W/mm², especially a power density at least 7 W/mm², more especially at least 9 W/mm², even more especially at least 13 W/mm². Hence, in embodiments in an operational mode of the light generating device, the light generating device is configured to generate the luminescent material light from a radiation exit surface (or radiation exit face) of the luminescent converter with a power density of at least 4 W/mm². In yet further specific embodiments, the lighting device may be configured to provide luminescent light in combination with blue and/or red laser light coming out the same surface as the luminescent light providing white light with a brightness of at least 2000 lm/mm², more especially at least 3000 lm/mm², even more especially at least 6000 lm/mm² Herein, “lm” refers to lumen.

In yet a further aspect, the invention also provides a lamp or luminaire comprising the light generating device as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc.

The lighting device (or luminaire) may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs, la-lg schematically depict some aspects and variants;

Figs. 2a-2e show some emission spectra of embodiments; here, on the x-axis the wavelength l in nanometers is indicated and on the y-axis the power in W/nm; Figs. 3a-3d schematically depict some embodiments; and Fig. 4 schematically depicts further embodiments. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figs, la-lg schematically depict embodiments of a light generating device 1000 configured to generate device light 1001. The light generating device 1000 comprises a first light source 110, a second light source 120, and a first luminescent material 210. The first light source 110 may be configured to generate blue first light source light 111 having a first peak wavelength li selected from the spectral wavelength range of 440-480 nm. Especially, the first light source 110 is a first laser light source 10. The second light source 120 may be configured to generate green second light source light 121 having a second peak wavelength l2 selected from the spectral wavelength range of 495-570 nm. Especially, the second light source 120 is a second laser light source 20. The first luminescent material 210 is configured to convert part of the second light source light 121 into first luminescent material light 211 having a first luminescent material dominant wavelength λ_dL1 in the spectral wavelength range of 575-605 nm. As schematically depicted in these embodiments, the first luminescent material is not configured to convert at least part of the first light source light 111.

Especially, the light generating device 1000 is configured to provide in a first operational mode (white) device light 1001 comprising the first light source light 111, the second light source light 121, and the first luminescent material light 211. The first device light 1001 may have a correlated color temperature selected from the range of equal to or smaller than 3200 K and a color rendering index of equal to or larger than 80.

In specific embodiments, li may be selected from the spectral wavelength range of 450-470 nm. Further, in specific embodiments l2 may be selected from the spectral wavelength range of 515-545 nm. Especially, the correlated color temperature may be selected from the range of 2000-3000 K. Further, in specific embodiments the first luminescent material dominant wavelength λ_dL1 may be selected from the range of 585-600 nm, such as especially 590-600 nm, see also Figs. 2a, 2b, and 2d. In such embodiments, in the first operational mode the white device light 1001 consists of the first light source light 111, the second light source light 121, and the first luminescent material light 211. For instance, the white device light 1001 may have a CRI of at least 90. Embodiments of such system are e.g. schematically depicted in Figs, la, lb, and Id.

In yet other embodiments, the first luminescent material dominant wavelength λ_dLi is selected from the range of 580-590 nm. The light generating device 1000 further comprises one or more of (a) a third light source 130 configured to generate red third light source light 131 having a third peak wavelength λ₃ selected from the spectral wavelength range of 620-675 nm, such as 625-675 nm, wherein the third light source 130 is a third laser light source 30; and (b) a second luminescent material 220 configured to convert part of the first light source light 111 and/or second light source light 121 into second luminescent material light 221 having a second luminescent material dominant wavelength λ_dL2 in the spectral wavelength range of 620-675 nm, such as 625-675 nm (and which may not be configured to convert at least part of the first luminescent material light 211). Embodiments of the former option are schematically depicted in Figs, lc, le, and If. An embodiment of the latter option is schematically depicted in Fig. lg.

In such embodiments with further source of light, especially about red light, in the first operational mode the white device light 1001 consists of (i) the first light source light 111, (ii) the second light source light 121, (iii) the first luminescent material light 211, and (iv) one or more of the third light source light 131 and the second luminescent material light 221. Especially, the white device light 1001 has a CRI of at least 90. Spectral power distributions with a red third light source are depicted in Figs. 2c and 2e.

As schematically depicted in Figs la-lg, the light generating device 1000 may further comprise one or more optical elements 420 configured to combine the first light source light 111, the second light source light 121, and the first luminescent material light 211. Especially, in embodiments the first luminescent material 210 may thus be configured downstream of the second light source 120 and is not configured downstream of the first light source 110. In yet other embodiments, one or more of the one or more optical elements 420 may be configured to combine the first light source light 111, the second light source light 121, the first luminescent material light 211, and optionally the third light source light 131 (see e.g. Fig. le, If and lg). Optical elements directly downstream of the luminescent material may be used to collimate the beam of luminescent material light. This may be useful for other optical elements downstream thereof, such as e.g. a dichroic beam combiner. For instance, such optical elements directly downstream of the luminescent material may be collimators, like in embodiments CPCs. In embodiments, one or more of the one or more optical elements 420 may comprise dichroic mirrors. Alternatively or additionally, one or more optical elements 420 may be configured to beam shape the device light 1001. For instance, a collimator element may be applied (see e.g. Fig. la).

Hence, in embodiments a luminescent body 1200 may comprise the second luminescent material 220. Referring to Fig. lg, the light generating device 1000 may comprises a plurality of first light sources 110, wherein a first set of one or more first light sources 110 are configured upstream of the luminescent body 1200, and wherein a second set of one or more first light sources 110 are configured to provide first light source light 111 that bypasses the luminescent body. Of course, similar solutions may be provided with a single light source, and a beam splitter.

In embodiments, the first luminescent material 210 is selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures.

Referring e.g. to Figs, la-lc the light generating device 1000 may further comprising a control system 300. In specific embodiments, the control system 300 may be configured to control one or more of the correlated color temperature and the color rendering index of the device light 1001 by controlling (i) the first light source 110, (ii) the second light source 120, and optionally (iii) the third light source 130. In an operational mode of the light generating device 1000, the light generating device 1000 is configured to generate the device light 1001 with a brightness of at least 2000 lm/mm².

As indicated above, optical element 420 may e.g. be a dichroic mirror or dichroic combiner. Optical element 420 may also be a combination of a plurality of dichroic mirrors or dichroic combiners. The device 1000 may further optionally comprise an optical element 420 configured to combine and/or homogenize optionally unconverted first light source light 111, the second light source light 121, the first luminescent material light 122, the optional third light source light 131 and/or the optional second luminescent material light 221„ to provide device light 1001. In specific embodiments, the optical element 420 may comprises one or more of (i) a dichroic beam combiner and (ii) an optical homogenizer. The optical element 420 may alternatively or additionally be configured to beam shape the device light 1001 and/or configured to homogenize the device light 1001. As schematically depicted the optical element 420 is configured downstream of the first luminescent material 210. For instance, the optical element 420 may comprise a CPC like optical element. The optical element 420 may include one or more of reflective and transmissive optics. In the schematic drawings, transmissive optics are schematically depicted, but this should not be interpreted as being limited to transmissive optics.

Focusing may be executed with one or more optics, like (focusing) lenses. Especially, two lenses may be applied to focus the laser light source light. Collimation may be executed with one or more (other) optics, like collimation elements, such as lenses and/or parabolic mirrors. References 410 indicate optics that may be used for focusing and/or collimation. Though a single lens is depicted, other types of lenses, a plurality of lenses, may also be applied, as reference 410 indicate optics, especially focusing and/or collimation optics, in general, especially the optics 410 may comprise focusing optics.

Referring to Figs. 3a-3d the first luminescent material 210 and/or the second luminescent 220 material may be comprised by a luminescent body 1200. In embodiments, the luminescent body 1200 may comprise at least the first luminescent material 210. In specific embodiments, the luminescent body 1200 comprises one or more of a ceramic body and a multi-layer material. Figs. 3a and 3b schematically depict some embodiments of the first luminescent material 210. Here, embodiments are depicted wherein the luminescent material is provided as body 1200 (see also above). The height is indicated with reference H, the width with reference W, the length with reference L, and the diameter with reference D. Note that in embodiments the body 1200 may also comprise two or more luminescent materials, such as the first luminescent material 210 and the second luminescent material 220. Hence, optionally reference 210 may also be interpreted as the first luminescent material 210 and the second luminescent material 220. Fig. 3c schematically depicts a multilayer, one comprising the first luminescent material 210 and one comprising the second luminescent material 220. Fig. 3d schematically depicts a body, such as a polymeric body or a ceramic body, comprising both the first luminescent material 210 and the second luminescent material 220. References 125 and 126 indicate a first and a second face, respectively, which may defined the height (thickness). Second light source light may e.g. be transmitted through the luminescent body 1200 parallel to the height (e.g. when perpendicularly irradiating the first face 125 or the second face 126).

Fig. 4 schematically depicts an embodiment of a luminaire 2 comprising the light generating device 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system (not depicted) comprised by or functionally coupled to the lighting system 1000. Fig. 4 also schematically depicts an embodiment of lamp 1 comprising the light generating device 1000. Amongst others, using a green laser instead of cerium doped garnet phosphor and pump orange emitting phosphor with green laser light is herein suggest. In this way problems with quenching may to be minimized. Blue laser light is thus not used for pumping the orange phosphor. We have found amongst others that by combining a blue (470nm) laser, a green (535nm) laser and an orange light emitting phosphor we could make white sources with CRI>80 in a wide CCT range on the black body line (BBL). In order to obtain CRI>90 below 3000K on the BBL, the dominant wavelength kd may especially be 590nm≤kd≤600 nm. In this range without a need for extra red laser CRI>90 at CCT≤3000 can be obtained. However, in this range extra red laser emission can be used kr≥ 650 nm for increasing the R9 of the white light. When the dominant wavelength of the phosphor is 580 nm ≤ kd≤ 590 nm then it is desirable to use a red laser emitting at 670 nm≥ kr≥ 630 nm for obtaining CRI>90 below CCT≤3000 K. For instance nitride and/or silicate phosphors can be used for emitting orange light. The emission line for green light source kg needs to be in the range 515 nm≤kg≤540 nm. The emission line for blue light source kb needs to be in the range 450 nm≤kb≤470nm. In order to obtain high CRI using garnet phosphor in combination with blue and red emitting lasers we found that it still necessary to use of orange color emitting phosphor in order to obtain CRI >90 for 2300≤CCT≤3000 K. In such a system blue laser pumped garnets emission from the phosphor is partially used for pumping the orange emitting phosphors leading to excess temperature increase due to the heating up of the YAG phosphor. In order to solve this problem, we suggest using green laser instead of Cerium doped garnet phosphor and pump the orange emitting phosphor with green laser light. In this way problems with quenching is to be minimized.

In Fig. 2a we show the modelling result for blue laser and green laser pumped orange phosphor with dominant wavelength k_d=596 nm (k_max=616 nm, FWHM=76 nm) white light on BBL with CCT=2656 K, CRI=90 and R9=52 was obtained. In table 1 various combinations are shown: TABLE 1:

Amongst others, in this table blue (470 nm), green (535 nm) lasers and orange light emitting phosphor with a dominant wavelength (λ_d) 590 nm ≤ λ_d ≤600 nm (emission maximum λ_max ≥ 610 nm full width at half maximum ≥ 60 nm) are used, which is already enough for a CRI 90 at CCT below 3000 K on the black body line. The percentual contribution of each laser and phosphor material to the spectral power distribution is provided as well in the tables.

In order to increase R9 it is possible to use an extra red emitter used with A,> 650 nm as shown in Table 2. TABLE 2:

When the dominant wavelength of the phosphor is 580 nm ≤ λ_d ≤590 nm then it is necessary to use a red laser emitting at 670 nm ≥ λ _r ≥ 630 nm. In Fig. 2b we show a spectrum with only blue and laser together with an orange phosphor emission giving CRI of 85. Fig. 2c shows a spectrum where red laser is added to the spectrum which increases CRI to 93. Table 3 shows various combinations to this end.

TABLE 3:

Fig. 2d and 2e we show modelling results for silicate phosphor with and without an additional red laser. The properties the white light source is shown in Table 4. The CRI improves from 86 to above 90 and the R9 improves from 16 to 77 or higher by using an extra red emitter with a dominant wavelength of about 650 nm, either in the form of a red laser light source or in the form of a red luminescent material.

In Table 5 the emission line for green light source λ_g needs to be in the range 515 nm ≤ λ_g≤ 540 nm.

TABLE 5:

In Table 6 the emission line for blue light source λ_g needs to be in the range 470 nm ≤ λ_g≤ 450 nm. TABLE 6:

Table 7 shows that the CRI improves from 86 to above 90 and the R9 improves from 16 to 52 or higher by using an extra red emitter with a dominant wavelength of about 625 nm, either in the form of a red laser light source or in the form of a red luminescent material.

TABLE 7:

Table 8 shows that the CRI improves from 86 to 92 and the R9 improves from 16 to 68 by using an extra red emitter with a dominant wavelength of about 675 nm, either in the form of a red laser light source or in the form of a red luminescent material. TABLE 8:

Table 9 shows that for an orange phosphor have a dominant wavelength of 575 nm or 605 nm that is excited by a green laser, combined with a blue laser and a red laser, white light with a CRI of at least 80, a good R9 value and a relatively high efficiency is obtained.

TABLE 9:

The term “plurality” refers to two or more.

The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.

The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’.

The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

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

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

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

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

Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

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

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

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

Claims

CLAIMS:

1. A light generating device (1000) configured to generate device light (1001), wherein the light generating device (1000) comprises a first light source (110), a second light source (120), and a first luminescent material (210), wherein: the first light source (110) is configured to generate blue first light source light (111) having a first peak wavelength li selected from the spectral wavelength range of 440- 480 nm, wherein the first light source (110) is a first laser light source (10); the second light source (120) is configured to generate green second light source light (121) having a second peak wavelength l2 selected from the spectral wavelength range of 495-570 nm, wherein the second light source (120) is a second laser light source (20); the first luminescent material (210) is configured to convert part of the second light source light (121) into first luminescent material light (211) having a first luminescent material dominant wavelength λdL1 in the spectral wavelength range of 575-605 nm; the light generating device (1000) is configured to provide in a first operational mode white device light (1001) comprising the first light source light (111), the second light source light (121), and the first luminescent material light (211), with a correlated color temperature selected from the range of equal to or smaller than 3200 K and a color rendering index of equal to or larger than 80, and wherein the light generating device (1000) further comprises one or more of: a third light source (130) configured to generate red third light source light (131) having a third peak wavelength l3 selected from the spectral wavelength range of 625- 675 nm, wherein the third light source (130) is a third laser light source (30); a second luminescent material (220) configured to convert part of the first light source light (111) and/or second light source light (121) into second luminescent material light (221) having a second luminescent material dominant wavelength A_<IL2 in the spectral wavelength range of 625-675 nm.

2. The light generating device (1000) according to claim 1, wherein one or more of the following applies: (i) li is selected from the spectral wavelength range of 450-470 nm, (ii) λ₂ is selected from the spectral wavelength range of 515-545 nm, and (iii) the correlated color temperature is selected from the range of 2000-3000 K.

3. The light generating device (1000) according to any one of the preceding claims, wherein the first luminescent material dominant wavelength λ_dL1 is selected from the range of 590-600 nm.

4. The light generating device (1000) according to claim 3, wherein in the first operational mode the white device light (1001) consists of the first light source light (111), the second light source light (121), and the first luminescent material light (211), wherein the white device light (1001) has a CRI of at least 90.

5. The light generating device (1000) according to any one of the preceding claims 1-2, wherein the first luminescent material dominant wavelength λ_dL1 is selected from the range of 580-590 nm.

6. The light generating device (1000) according to any one of the preceding claims, wherein λ3 is selected from the spectral wavelength range of 635-66 nm and wherein λ_dL2 is selected from the spectral wavelength range of 625-675 nm.

7. The light generating device (1000) according to claim 5 and 6, wherein in the first operational mode the white device light (1001) consists of (i) the first light source light (111), (ii) the second light source light (121), (iii) the first luminescent material light (211), and (iv) one or more of the third light source light (131) and the second luminescent material light (221), wherein the white device light (1001) has a CRI of at least 90.

8. The light generating device (1000) according to any one of the preceding claims, further comprising an optical element (420) configured to combine the first light source light (111), the second light source light (121), and the first luminescent material light (211), wherein the first luminescent material (210) is configured downstream of the second light source (120) and is not configured downstream of the first light source (110).

9. The light generating device (1000) according to claim 8, comprising a plurality of optical elements (420), wherein the optical elements (420) comprise one or more of a dichroic mirror and a cross-dichroic prism, and wherein the plurality of optical elements (420) are configured to combine the first light source light (111), (ii) the second light source light (121), (iii) the first luminescent material light (211), and optionally (iv) the third light source light (131) according to any one of claims 6-7.

10. The light generating device (1000) according to any one of the preceding claims, comprising a luminescent body (1200), wherein the luminescent body (1200) comprises the first luminescent material (210).

11. The light generating device (1000) according to claim 11, wherein the luminescent body (1200) comprises one or more of a ceramic body and a multi-layer material.

12. The light generating device (1000) according to any one of the preceding claims 10-11, wherein the luminescent body (1200) further comprises the second luminescent material (220), wherein the light generating device (1000) comprises a plurality of first light sources (110), wherein a first set of one or more first light sources (110) are configured upstream of the luminescent body (1200), and wherein a second set of one or more first light sources (110) are configured to provide first light source light (111) that bypasses the luminescent body.

13. The light generating device (1000) according to any one of the preceding claims, wherein the first luminescent material (210) is selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures.

14. The light generating device (1000) according to any one of the preceding claims, further comprising a control system (300), wherein the control system (300) is configured to control one or more of the correlated color temperature and the color rendering index of the device light (1001) by controlling (i) the first light source (110), (ii) the second light source (120), and optionally (iii) the third light source (130) as defined in any one of claims 6-7 and 9.

15. A lamp (1) or a luminaire (2) comprising the light generating device (1000) according to any one of the preceding claims.