Helium filled enclosure inside a bulb

Abstract

The invention provides a light generating system comprising one or more first light generating devices, one or more second light generating devices, and a light transmissive enclosure, wherein: (A) the light transmissive enclosure comprises a light transmissive material; wherein the light transmissive enclosure defines an enclosure volume; wherein the light transmissive enclosure further contains a thermally conductive gas, wherein the thermally conductive gas comprises one or more of (i) He in a percentage of at least 1%, (ii) H2 in a percentage of at least 1%, and (iii) Ne; (B) the one or more first light generating devices are configured in the enclosure volume; wherein the one or more first light generating devices are configured to generate first device light having intensity at one or more wavelengths in the visible wavelength range; wherein the one or more first light generating devices comprise one or more first LED filaments; wherein the one or more first LED filaments comprise first solid state light sources and a first luminescent material, wherein the first solid state light sources are configured to generate first solid state light source light, and wherein the first luminescent material is configured to convert at least part of the first solid state light source light into first luminescent material light; wherein the first device light comprises at least part of the first luminescent material light; (C) the one or more second light generating devices are configured external from the enclosure volume; wherein the one or more second light generating devices comprise one or more second LED filaments; wherein the one or more second light generating devices are configured to generate second device light having intensity at one or more wavelengths in the visible wavelength range; and (D) the light generating system is (a) configured to generate system light comprising one or more of (i) at least part of the first device light, and (ii) at least part of the second device light, and (b) configured such that in a first operational mode of the light generating system the system light is white light.

Description

[0001] HELIUM FILLED ENCLOSURE INSIDE A BULB

[0002] FIELD OF THE INVENTION

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

[0004] BACKGROUND OF THE INVENTION

[0005] Light generating systems comprising a light transmissive enclosure are known in the art. For instance, US20190101248 describes a lamp including a substantially transparent housing tube, a first end cap at a first end of the housing tube and a second end cap at a second end of the housing tube. The end caps include contacts for electrically contacting a power supply. An LED-filament is arranged in the housing tube between the first end cap and the second end cap.

[0006] SUMMARY OF THE INVENTION

[0007] There is a desire for lighting devices that may especially be efficient and / or create desirable optical effects. Some of the known systems may be complicated to make, suffer from low lumen per Watt efficiency, and / or may not be able to provide desired optical effects. Further, there is a desire to provide lighting devices having an adjustable spectral power distribution. Prior art systems, however, may not provide one or more of such technical features. Hence, it is an aspect of the invention to provide an alternative light generating system, which preferably further at least partly obviates one or more of abovedescribed 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.

[0008] According to a first aspect, the invention provides a light generating system comprising one or more first light generating devices, one or more second light generating devices, and a light transmissive enclosure. In embodiments, the light transmissive enclosure (“first enclosure” or “first light transmissive enclosure”) may comprise a light transmissive material. Further, the light transmissive enclosure may define an enclosure volume (“first enclosure volume”). In embodiments, the light transmissive enclosure may further contain a thermally conductive gas. Especially, the thermally conductive gas may in embodiments comprise He, especially in a percentage of at least 10%. Additionally or alternatively, the thermally conductive gas may comprise H2, especially in a percentage of at least 1%. Further, in embodiments, the thermally conductive gas may comprise Ne, especially in a percentage of at least 1%. In embodiments, the one or more first light generating devices may be (at least partly) configured in the enclosure volume. Additionally, the one or more first light generating devices may be configured to generate first device light having intensity at one or more wavelengths in the visible wavelength range. Further, the one or more first light generating devices may comprise one or more first LED filaments. In such embodiments, the one or more first LED filaments may comprise (a plurality of) first solid state light sources and a first luminescent material. The first solid state light sources may especially be configured to generate first solid state light source light. Further, the first luminescent material may be configured to convert at least part of the first solid state light source light into first luminescent material light. In embodiments, the first device light may comprise at least part of the first luminescent material light. In embodiments, the one or more second light generating devices may be (at least partly) configured external from the enclosure volume (i.e., the enclosure volume may not comprise the one or more second light generating devices). Especially, in embodiments, the one or more second light generating devices may comprise one or more second LED filaments. In embodiments, the one or more second light generating devices may be configured to generate second device light having intensity at one or more wavelengths in the visible wavelength range. In embodiments, the light generating system may be configured to generate system light comprising at least part of the first device light. Additionally or alternatively, the light generating system may be configured to generate system light comprising at least part of the second device light. Further, in embodiments, the light generating system may be configured such that in a first operational mode of the light generating system the system light is white light.

[0009] Hence, in specific embodiments, the invention provides a light generating system comprising one or more first light generating devices, one or more second light generating devices, and a light transmissive enclosure, wherein: (A) the light transmissive enclosure comprises a light transmissive material; wherein the light transmissive enclosure defines an enclosure volume; wherein the light transmissive enclosure further contains a thermally conductive gas, wherein the thermally conductive gas comprises one or more of (i) He in a percentage of at least 1%, (ii) H2 in a percentage of at least 1%, and (iii) Ne in a percentage of at least 1%; (B) the one or more first light generating devices are configured in the enclosure volume; wherein the one or more first light generating devices are configured to generate first device light having intensity at one or more wavelengths in the visible wavelength range; wherein the one or more first light generating devices comprise one or more first LED filaments; wherein the one or more first LED filaments comprise first solid state light sources and a first luminescent material, wherein the first solid state light sources are configured to generate first solid state light source light, and wherein the first luminescent material is configured to convert at least part of the first solid state light source light into first luminescent material light; wherein the first device light comprises at least part of the first luminescent material light; (C) the one or more second light generating devices are configured external from the enclosure volume; wherein the one or more second light generating devices comprise one or more second LED filaments; wherein the one or more second light generating devices are configured to generate second device light having intensity at one or more wavelengths in the visible wavelength range; and (D) the light generating system is (a) configured to generate system light comprising one or more of (i) at least part of the first device light, and (ii) at least part of the second device light, and (b) configured such that in a first operational mode of the light generating system the system light is white light.

[0010] A light generating system comprising such a light transmissive enclosure may provide improved thermal management for at least the one or more first light generating devices configured in the enclosure volume. Hence, the temperature of the one or more first light generating devices may be decreased, thus extending their lifetime and / or improving the lumen output. Further, configuring the one or more first light generating devices in the enclosure volume, and the one or more second light generating devices external to the enclosure volume may decrease optical crosstalk between said first light generating devices and said second light generating devices (see below). Further, a light generating system comprising one or more first light generating devices and one or more second light generating devices may facilitate adjusting one or more of the spectral power distribution, light intensity, and correlated color temperature of the system light. Especially, a light generating system comprising one or more first light generating devices and one or more second light generating devices may facilitate generating colored light, especially in the RGB color space.

[0011] In embodiments, the light generating system may thus comprise the light transmissive enclosure. The light transmissive enclosure may comprise a light transmissive material, wherein the light transmissive material may especially be transmissive for one or more of the first device light and the second device light, such as transmissive for at least the first device light. In embodiments, the light transmissive material may be selected from the group comprising glass and (optically translucent and / or transparent) polymeric materials. Herein, the terms “optically transparent” material and “light transmissive” material may refer to a material transmissive for one or more wavelengths selected from the range of 190-1500 nm, such as selected from the range of 200-1000 nm, especially selected from the range of 380-780 nm. Further, in embodiments, the light transmissive material may be configured to transmit > 80%, such as > 90%, especially > 95%, including 100%, of the first device light incident perpendicular on the light transmissive material. Further yet, in embodiments, the light transmissive material may be configured to transmit > 80%, such as > 90%, especially > 95%, including 100%, of the second device light incident perpendicular on the light transmissive material. More especially, in embodiments the (first) light transmissive enclosure as such (i.e. not taking into account the optional optical filter (see below)) may be transparent for first device light. Further, in embodiments the (first) light transmissive enclosure as such (i.e. not taking into account the optional optical filter) may also be transparent for second device light.

[0012] The light transmissive enclosure may comprise an axis of elongation, an enclosure length Li defined parallel to the axis of elongation, and an enclosure width Wi perpendicular to the axis of elongation. In embodiments, the enclosure length Li may be selected from the range of 2-15.5 cm, such as from the range of 2.5-12.5 cm, especially from the range of 3-10 cm. Further, the enclosure width Wi may in embodiments be selected from the range of 1-12.5 cm, such as from the range of 2-10 cm, especially from the range of 2.5-8 cm. Other values, however, may also be possible. In embodiments, the light transmissive enclosure may have a substantially circular cross-section (perpendicular to the axis of elongation). Here, the term “substantially” is used, as in some embodiments there may be a relatively small modulation of the external surface, which is relatively small compared to the diameter. Alternatively, the light transmissive enclosure may have a substantially n-gonal cross-section (perpendicular to the axis of elongation), wherein n>2, such as n>6, especially n>8. When n=2, the external side faces may be curved, when n is 3 or larger, the external side faces may be curved or (substantially) planar. In embodiments, the light transmissive enclosure may have an n-gonal cross-section wherein n>12, such as n>24. In embodiments, n may be selected from the range of 2-48, such as 4-36. Further, in embodiments the light transmissive enclosure may have a tubular (or “cylindrical”) shape. Hence, the light transmissive enclosure may be a tubular enclosure or a cylindrical enclosure. Additionally or alternatively, in embodiments, the light transmissive enclosure may have a conical shape or pyramidal shape, i.e., the light transmissive enclosure may have (some) tapering over at least part of the axis of elongation of the light transmissive enclosure.

[0013] Especially, the light transmissive enclosure may be hollow, i.e., the light transmissive material may especially be configured as a wall surrounding the enclosure volume. Further, the light transmissive enclosure, especially the light transmissive material, may comprise an inner face and an outer face, wherein the inner face may be configured facing the enclosure volume (and the one or more first light generating devices), and wherein the outer face may be configured facing away from the light transmissive enclosure (towards the one or more second light generating devices). In embodiments, the light transmissive enclosure, especially the inner face, may define the enclosure volume. In specific embodiments, the light transmissive enclosure may comprise a first equivalent spherical diameter Di. In embodiments, the first equivalent spherical diameter Di may be selected from the range of 1-15 cm, such as from the range of 1.5-12 cm, like at least about 2 cm, especially from the range of 4-10 cm. The equivalent spherical diameter (or ESD) of an (irregularly) shaped three-dimensional object is the diameter of a sphere of equivalent volume. For instance, the equivalent spherical diameter (ESD) of a cube with a side a is 2 * a * ^ / 3 / (4 * n). For a sphere, the diameter D is the same as the equivalent spherical diameter D. Would a sphere in an xyz-coordinate system with a diameter D be distorted to any other shape (in the xyz-plane), without changing the volume, than the equivalent spherical diameter of that shape would be D.

[0014] In embodiments, the light transmissive enclosure may contain a thermally conductive gas, especially in the enclosure volume. Further, in embodiments, the light transmissive enclosure may be sealed, such that the thermally conductive gas may not escape the light transmissive enclosure (“gastight”). In embodiments, the thermally conductive gas may be configured in thermal contact with the one or more first light generating devices. Further, in embodiments, the thermally conductive gas may have a thermal conductivity (at 22 °C and a pressure of 1 bar) selected from the range of > 0.03 W*m'1*K'1, such as from the range of > 0.06 W*m'1*K'1, especially from the range of > 0.1 W*m'1*K'1. Additionally or alternatively, in embodiments, the thermally conductive gas may have a thermal conductivity (at 22 °C and a pressure of 1 bar) selected from the range of < 0.6 W*m'1*K'1, such as from the range of < 0.4 W*m'1*K'1, especially from the range of < 0.3 W*m'1*K'1.

[0015] Further, in embodiments, the thermally conductive gas may comprise helium (He). Especially, the thermally conductive gas may comprise He in a percentage of at least 5%, such as at least 10%, especially at least 25%, more especially at least 35%. Further, in embodiments, the thermally conductive gas may comprise helium in a percentage of at least 60%, such as at least 70%, especially at least 75%. Hence, in specific embodiments, the thermally conductive gas may comprise He in a percentage of at least 60%. Further, in embodiments, the thermally conductive gas may (essentially) consist of He, i.e., the thermally conductive gas may comprise He in a percentage of at least 90%, such as at least 95%, especially at least 99%, including 100%. Helium may have a relatively high thermal conductivity. Hence, a thermally conductive gas comprising helium may provide heat sinking, thus improving thermal management in the light generating system, especially in the enclosure volume. Improved thermal management may reduce the temperature of the one or more (first) light generating devices configured in the enclosure volume during operation of the light generating system. Consequently, the lifetime of the one or more (first) light generating devices may be extended. Further, in embodiments, improved thermal management may facilitate operating said one or more (first) light generating devices at higher currents without (overheating the (first) light generating devices.

[0016] In embodiments, the thermally conductive gas may comprise hydrogen (H2). Hydrogen may have a higher thermal conductivity than helium. In embodiments, the thermally conductive gas may comprise H2 in a percentage of at least 1%, such as at least 10%, especially at least 25%, more especially at least 35%. In embodiments, hydrogen may be relatively more reactive than helium. Hence, in embodiments, the thermally conductive gas may comprise H2 in a percentage of at most 70%, such as at most 60%, especially at most 50%. In embodiments wherein the thermally conductive gas comprises H2, the remainder of the thermally conductive gas may especially comprise inert gas, such as a noble gas (e.g. helium) and / or nitrogen gas. Especially, said remainder of the thermally conductive gas may comprise at most 15% oxygen, such as at most 10% oxygen, especially at most 5% oxygen. A thermally conductive gas comprising H2 and a noble gas such as helium may improve the thermal conductivity of the thermally conductive gas. Hence, in embodiments, the thermally conductive gas may comprise one or more of helium and hydrogen, such as helium, or such as hydrogen, or such as helium and hydrogen. In embodiments, wherein less than 1 % H2 is available, the O2 content may be at least about 5%.

[0017] Further, in embodiments, the thermally conductive gas may comprise neon (Ne). Especially, the thermally conductive gas may comprise Ne in a percentage of at least 1%, such as in embodiments at least 5%, such as at least 10%, especially at least 25%, more especially at least 35%. Further, in embodiments, the thermally conductive gas may comprise Ne in a percentage of at most 70%, such as at most 60%, especially at most 50%. In embodiments, the thermally conductive gas may comprise Ne in combination with (a) helium, (b) hydrogen, or (c) helium and hydrogen.

[0018] Hence, in specific embodiments the thermally conductive gas may comprise one or more of He, H2, and Ne, with these cases in total especially at least about 5%, more especially at least about 10%, such as at least about 25%.

[0019] In embodiments, instead of, or in addition to the thermally conductive gas, a thermally conductive liquid may be applied. In such embodiments, the thermally conductive liquid may (essentially) not conduct electricity. Further, especially the thermally conductive liquid is inert to the first light generating device(s). Hence, the liquid may in embodiments not substantially contain water. Yet, the thermally conductive liquid may be (light) transmissive, such as especially transmissive for light in the visible wavelength range (380- 780 nm), more especially light transparent for visible light Hence, in specific embodiments the free space in the first enclosure volume may be filled with a liquid. Hence, the first enclosure volume may in embodiments be filled with liquid, that is in contact with the one or more first light generating devices, also available in the first enclosure volume.. Suitable thermally conductive liquid may comprise one or more of glycerol and silicone oil. However, other thermally conductive liquids may also be possible. In embodiments, the liquid may comprise a fluorocarbon.

[0020] In embodiments, in the off-state of the light generating system, the thermally conductive gas may have a first pressure Pi (at a temperature of 22 °C) in the enclosure volume. In embodiments, the first pressure Pi may be selected from the range of 1-10 bar, such as from the range of 1.25-8 bar, especially from the range of 1.5-5 bar. Such a first pressure Pi may provide increased thermal conductivity of the thermally conductive gas, compared to the same gas at a pressure of 1 bar.

[0021] In embodiments, the light transmissive enclosure may at least partially enclose one or more light generating devices, such as especially the one or more first light generating devices. Specifically, in embodiments, the one or more first light generating devices may be configured in the enclosure volume.

[0022] The (first) light transmissive enclosure may form a hermetic seal (i.e., especially substantially watertight, more especially substantially airtight) with the support and thus, protect the light generating device from the ingress of dust, dirt and pollutants. For instance, in embodiments the first light transmissive enclosure together with the support may provide a (first) enclosure volume with an IP44 or higher classification. However, other embodiments may thus also be possible. Hence, in embodiments, the light generating system may comprise one or more first light generating devices. Especially, in embodiments, the light generating system may comprise 1-20 first light generating devices, such as 2-15 first light generating devices, especially 3-10 first light generating devices. In embodiments, the one or more first light generating devices may be configured to generate first device light. Further, the one or more first light generating devices may comprise one or more first LED filaments. In specific embodiments, each of the one or more first light generating devices may comprise one first LED filament. Hence, in embodiments, the light generating system may comprise 1-20, such as 2-15, especially 3-10 first LED filaments. In embodiments, the one or more first LED filaments may be configured to generate the first device light.

[0023] LED filaments as such are known, and are e.g. described in US 8,400,051 B2, W02020016058, WO2019197394, etc., which are herein incorporated by reference. In general, a LED filament may comprise (i) a plurality of light emitting diodes (LEDs), arranged on (at least a first major surface of) an elongated carrier, and (ii) an elongated encapsulant covering the plurality of LEDs and at least part of the elongated carrier. Especially, the encapsulant may cover essentially the entire elongated carrier. The LED filament may in embodiments be defined by a filament length LF, a filament width WF, and a filament thickness TF. Further, the LED filament may have relatively high aspect ratios (LF / WF or LF / TF), such as at least 10, especially at least 15, such as at least 20, more especially at least 50. Large aspect ratios may better mimic a filament. Yet, in embodiments, the aspect ratio (LF / WF and / or LF / TF) may be at most 200, such as at most 150, especially at most 100. Hence, in specific embodiments, 10*WF < LF < 200*WF, and 10*TF < LF < 200*TF. In some embodiments, the LED filament may be straight. In other embodiments, the LED filament may be curved. For instance, the filament may have a (2D or 3D) spiraling shape, (like) a helical shape, or another curved shape.

[0024] Further, as indicated, the LED filament may comprise an elongated carrier, solid state light sources, and an encapsulant. Especially, the elongated carrier may support the solid state light sources. The elongated carrier may e.g. comprise glass, quartz, metal, or sapphire. In other embodiments, the elongated carrier may e.g. comprise a polymeric material or (flexible) metal, e.g., a film or foil. The elongated carrier may be rigid (self-supporting), but may (in polymeric embodiments) also be flexible. In embodiments, the elongated carrier may be light transmissive, translucent, or transparent for light, especially for visible light. Alternatively, in embodiments, the carrier may be light reflective, especially reflective for one or more of the light source light and the LED filament light (see below), such as reflective for at least the light source light and the LED filament light. In specific embodiments, the carrier may be diffuse reflective. In embodiments, the elongated carrier may (essentially) define the filament length LF of the LED filament. Further, in embodiments, the (elongated) carrier may comprise a first major surface at a first side of the carrier and a second major surface at a second side of the carrier, opposite to the first side. In embodiments, the solid state light sources may be arranged on at least one of these surfaces. Hence, in embodiments, at least part of, such as all of, the solid state light sources may be mounted onto the first major surface. Additionally or alternatively, at least part of the solid state light sources may be mounted onto the second major surface. Hence, in embodiments, the solid state light sources may be arranged, mounted and / or mechanically coupled on / to the carrier, wherein the carrier may especially be configured to mechanically and / or electrically support the LEDs.

[0025] In embodiments, the solid state light sources may comprise LEDs. Alternatively or additionally, in embodiments, the solid state light sources may comprise diode lasers. Further, the LED filament may comprise one or more of LEDs, laser diodes, and superluminescent diodes. Especially, the LED filament comprises a plurality of light emitting diodes (LEDs). The (plurality of) solid state light sources may be arranged in an array (on the elongated carrier), especially over (at least part of) the filament length LF. The number of solid state light sources in the array may be at least 4, such as at least 8, especially at least 12. Especially, in embodiments the number of solid state light sources in the array may be selected from the range of 10-1000, such as from the range of 10-200. In embodiments, the solid state light sources may be configured in a ID (linear) array over at least part of the filament length LF. A first and a last solid state light source may, when measured along the LED filament, have a mutual distance of at least 0.5*LF, even more especially at least 0.7*LF. Further, in embodiments, the solid state light sources may be configured in two ID arrays, one on the first major surface of the elongated carrier and one on the second major surface. A 2D array of solid state light sources of n*m LEDs may also be possible. In embodiments, n may be selected from the range of 1-4, such as from the range of 1-3, like from the range of 1-2, and m may be selected from the range of > n, such as from the range of > 4 (when n<4), like from the range of >6, such as from the range of >8. Hence, a 2D array of solid state light sources may especially have a (much) smaller number of rows (n) than the number of solid state light sources in those respective rows (m), such as n / m <0.2, like n / m <0.1, especially n / m <0.05. In embodiments, the LED filament may comprise an encapsulant. The encapsulant may especially (at least partly) cover the plurality of solid state light sources, such as in embodiments > 50%, like >75%, especially >95%, including 100%, of the total number of solid state light sources in the array. Further, the encapsulant may (at least partly) cover at least part of the elongated carrier, such as at least (part of) one of the first major surface and the second major surface. In general, the encapsulant may be in contact with the elongated carrier and may cover all of the solid state light sources. Hence, in embodiments the encapsulant may be configured over a substantial part of the filament length LF of the LED filament (such as over more than 70% of the filament length LF). The encapsulant may be a continuous coating along the filament length LF.

[0026] In embodiments, the encapsulant may comprise one or more of a luminescent material and a light scattering material. The one or more of the luminescent material and the light scattering material may especially be configured embedded in an encapsulant material, e.g. a (flexible) polymer material (such as a silicone). In embodiments, the luminescent material may be configured to convert at least part, such as all, of the light source light (generated by the solid state light sources) into luminescent material light. Further, in embodiments, the light scattering material may be configured to scatter (or “diffuse”) the light source light, especially in a direction transverse to a normal of the (first and / or second) major surface. In specific embodiments, the light scattering material may comprise light scattering particles, such as e.g. at least one of BaSCU, A12O3 and TiCL particles.

[0027] In embodiments, the LED filament may be configured to generate filament light, which may comprise one or more of (scattered) light source light and luminescent material light. The term “LED filament light” may refer to the light emitted by the LED filament during operation of the LED filament. Further, the solid state light sources, comprised by the LED filament, may be configured to generate light source light. In embodiments, at least two, such as all, of the solid state light sources may be configured to emit light source light having different spectral power distributions. In other embodiments, at least two, such as all, of the solid state light sources may be configured to provide light source light having essentially the same spectral power distribution. In embodiments, the filament light may comprise the light source light, or may even essentially consist of (scattered) light source light. However, in embodiments wherein the encapsulant may comprise a luminescent material, the filament light may comprise luminescent material light, or may even essentially consist of luminescent material light. Further, in embodiments, the filament light may comprise luminescent material light and at least part of the (non-converted and / or scattered) light source light.

[0028] In embodiments, the one or more first LED filaments may be configured to generate first LED filament light. In embodiments, the first device light may comprise the first LED filament light, such as (essentially) consist of the first LED filament light. Further, in embodiments, the one or more first LED filaments may be configured to provide first LED filament light with a desired spectral light distribution, e.g., white light having a correlated color temperature selected from the range of 1500-8000 K. In such embodiments, the first filament light may comprise first luminescent material light and optionally transmitted (first) light source light. Further, the first LED filament light may at least comprise visible light. Here, 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. Further, in embodiments, the first LED filament light may at least comprise white light. Especially, the first filament light may be relatively warm (white) light, such as selected from the range of 1500 - 8000 K, especially selected from 1500 - 6500 K, most especially selected from the range of 1800- 6000 K.

[0029] In embodiments, the one or more first LED filaments may (each) comprise a plurality of first solid state light sources, configured to generate first solid state light source light. In embodiments, the first solid state light source light may have a centroid wavelength in the blue wavelength range, i.e., the first solid state light sources may be configured to (during operation) generate blue first solid state light source light. Further, in embodiments, the first solid state light source light may have a centroid wavelength selected from the range of 200-490 nm, such as from the range of 400-490 nm, especially from the range of 440-490 nm. The term “centroid wavelength”, also indicated as c, is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula kc = X I(k) / (S I( A)), where the summation is over the wavelength range of interest, and 1(A) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions.

[0030] In embodiments, the one or more first LED filaments (especially the first encapsulant) may comprise a first luminescent material. The first luminescent material may comprise a luminescent material selected from the group comprising divalent europium comprising oxynitride type luminescent materials, divalent europium comprising nitride type luminescent materials, trivalent cerium comprising garnet type luminescent materials, and tetravalent manganese comprising hexa-fluoride type luminescent materials (see below). In embodiments, a first luminescent material comprising one or more luminescent materials of the aforementioned types may especially facilitate the generation of first luminescent material light having intensity at one or more wavelengths in the visible wavelength range (upon irradiation with blue first solid state light source light), such as one or more of green, yellow, orange, and red first luminescent material light. In embodiments, admixing (a part of the) blue first solid state light source light into such first luminescent material light may provide white first device light. Hence, in specific embodiments, the one or more first LED filaments may be configured to generate white first device light.

[0031] The term “white light”, and similar terms, herein, is known to the person skilled in the art. It may especially relate to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700- 20000 K, for general lighting especially in the range of about 2000-7000 K, such as in the range of 2700-6500 K. In embodiments, the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), such as within about 10 SDCM from the BBL, especially within about 5 SDCM from the BBL.

[0032] The term “luminescent material” may especially refer 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, with the second radiation generally having a spectral power distribution at larger wavelengths than the first radiation (i.e. “down-conversion”). Hence, upon excitation with radiation, the luminescent material may emit radiation. In embodiments, the term “luminescence” may refer to one or more of phosphorescence and fluorescence. Instead of the term “luminescence”, also the term “luminescent material light” or “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. The term “luminescent material” may also refer to a plurality of different luminescent materials. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. Examples of possible luminescent materials are indicated below. Instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art. In embodiments, luminescent materials may be selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc. Alternatively or additionally, the luminescent material(s) may be selected from silicates, especially doped with divalent europium. In embodiments, the luminescent material may comprise a divalent europium comprising oxynitride luminescent material. Further, in embodiments, the luminescent material may comprise a divalent europium comprising nitride luminescent material.

[0033] In specific embodiments, the (first) luminescent material may (at least) comprise a trivalent cerium comprising garnet type luminescent material, i.e., a luminescent material of the type AsBsOn Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc; and wherein the solid state light source light may comprise blue solid state light source light. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. Further, in embodiments, garnets of the type AsBsOn may be doped with cerium (Ce), with praseodymium (Pr), or a combination of cerium and praseodymium; especially however with Ce. In a specific embodiment, the garnet luminescent material comprises (Yi.xLux)3B50i2:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Yi-xLux)3A150i2:Ce, part of Y and / or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art. In embodiments, such luminescent materials may have a suitable spectral distribution, have a relatively high efficiency, have a relatively high thermal stability, and allow a high CRI (optionally in combination with (the) light of other sources of light as described herein). In specific embodiments, the (first) luminescent material may only include luminescent materials selected from the type of cerium comprising garnets.

[0034] Further, in embodiments, the luminescent material may comprise a luminescent material of the type AsSieNiuCe3, wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y. In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu2+ and / or I hSisNs Eii2and / or MAlSiNvEu2and / or Ca2AlSi3O2Ns:Eu2+, etc., wherein M comprises one or more of Ba, Sr and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent material may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2SisN8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations, as is known to the person skilled in the art. 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 “luminescent material” herein especially relates to inorganic luminescent materials. Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and / or organic dyes may be applied and may optionally be embedded in transmissive (encapsulant) matrices like e.g. polymers, like PMMA, or polysiloxanes, etc.

[0035] In embodiments, the (first) luminescent material may comprise a tetravalent manganese comprising hexa-fluoride type luminescent material, i.e., a luminescent material of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises one or more alkaline earth cations, M comprises one or more alkaline cation, x may be selected from the range of 0-1, A comprises one or more tetravalent cations, for instance comprising one or more of silicon and titanium, and X comprises one or more monovalent anions, at least comprising fluorine. A luminescent material of the type M’xM2-2xAX6 doped with tetravalent manganese is amongst others described in WO2013121355A1, which is herein incorporated by reference. Passages from WO2013121355A1 are also copied herein. Relevant alkaline earth cations (M’) are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba. Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Optionally, also ammonium (NH / ), lithium (Li) and / or cesium (Cs) may be applied. In a preferred embodiment, M comprises at least potassium. In yet another embodiment, M comprises at least rubidium. In another preferred embodiment, M comprises at least potassium and rubidium.

[0036] The term “tetravalent manganese” refers to Mn4+. In the formula as indicated above, part of the tetravalent cation A (such as Si) is being replaced by manganese. Hence, M’XM2-2XAX6 doped with tetravalent manganese may also be indicated as M’XM2-2XAI.mMnmX6. The mole percentage of manganese, i.e. the percentage it replaces the tetravalent cation A will in general be in the range of 0.1-15 %, especially 1-12 %, i.e. m is in the range of 0.001-0.15, especially in the range of 0.01-0.12. As manganese replaces part of a host lattice ion and has a specific function, it is also indicated as “dopant”. Hence, the hexafluorosilicate is doped with manganese (Mn4+).

[0037] In embodiments, A may comprise one or more of silicon (Si), titanium (Ti), germanium (Ge), stannum (Sn) and zinc (Zn). Preferably, at least 80%, even more preferably at least 90%, such as at least 95%, of A consists of silicon. Further, in embodiments, X may comprise one or more of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), such as at least F. Preferably, at least 80%, even more preferably at least 90%, such as 95% of X consists of fluorine. Especially, X essentially consists of F (fluorine).

[0038] In an embodiment, M’xM2-2xAX6 comprises BGSiFe. In another preferred embodiment, M’xM2-2xAX6 comprises KRbSiFe. In specific embodiments, the indication M’XM2-2XAX6 may refer to one or more of (K,Rb)2SiFe:Mn4+, (K,Rb)2TiFe:Mn4+, K2(Si,Ti)Fe:Mn4+, and Rb2(Si,Ti)Fe:Mn4+, such as one or more of K2TiFe:Mn4+, of K2SiFe:Mn4+, and of Rb2SiFe:Mn4+. As can be derived from the above, “(Si,Ti)” may indicate one or more of Si and Ti. The luminescent material may also be coated, as also described in WO2013121355A1.

[0039] In embodiments, the first luminescent material may comprise one or more (types of) luminescent materials. Hence, in embodiments, (each of) the one or more first LED filaments may comprise one or more luminescent materials, such as selected from the group of divalent europium comprising oxynitride type luminescent materials, divalent europium comprising nitride type luminescent materials, trivalent cerium comprising garnet type luminescent materials, and tetravalent manganese comprising hexa-fluoride type luminescent materials. Such a configuration of one or more luminescent materials may facilitate generating first device light having a correlated color temperature (CCT) selected from the range of 1500-8000 K. Hence, in embodiments, the first device light may have a correlated color temperature selected from the range of 1500-8000 K, such as from the range of 1500- 6500 K, especially from the range of 1800-6500 K. Specifically, in embodiments, the one or more first LED filaments may be configured to generate first device light having a correlated color temperature selected from the range of 1500-6500 K. Such a range of correlated color temperatures may be beneficial, as light having a “warm” or “cool” temperature may be provided using the same (type of) first LED filaments. Further, such a configuration may facilitate generating first device light having a color rendering index (CRI) of at least 70. In embodiments, the first device light may thus have a color rendering index of at least 70, such as at least 80, especially at least 85. The terms “correlated color temperature” and “color rendering index” are known to a person skilled in the art. In embodiments, all of the one or more first LED filaments may provide light having the same correlated color temperature. Alternatively, each or a subset of the one of more first LED filaments may provide light having a different correlated color temperature. Hence, in embodiments, the light generating system, especially the one or more first light generating devices, may comprise at least two different types of first LED filaments. Especially, the light generating system may comprise at least two, such as at least 3, especially at least 4 different types of first LED filaments. Further, the light generating system may comprise at most 6, such as at most 5, especially at most 4 different types of first LED filaments. In embodiments, a first of the at least two different types of first LED filaments may be configured to generate first device light having a correlated color temperature Ti selected from the range of 1750-8000 K, such as from the range of 2000-8000 K, especially from the range of 2250-8000 K. Further, in embodiments, a second of the at least two different types of first LED filaments may be configured to generate first device light having a correlated color temperature T2 selected from the range of 1500-7000 K, such as from the range of 1500-6500 K, especially from the range of 1500-6000 K. Hence, in embodiments, the at least two different types of first LED filaments may be configured to generate first device light having correlated color temperatures differing at least 250 K, such as at least 500 K, especially at least 1000 K. Further, in embodiments, the at least two different types of first LED filaments may be configured to generate first device light having correlated color temperatures differing at most 5000 K, such as at most 4500 K, especially at most 4000 K. In specific embodiments, the light generating system may thus comprise at least two different types of first LED filaments configured to generate first device light having correlated color temperatures differing at least 500 K. Such a system may facilitate adjusting the correlated color temperature of the (combined) first device light by altering the relative intensities of the first device light generated by the first of the at least two different types of first LED filaments and the second of the at least two different types of first LED filaments, respectively. Especially, the correlated color temperature of the first device light may be adjusted during operation of the light generating system, such as when the system is in the first operational mode.

[0040] Here above, the first light generating devices are especially described in terms of LED filament embodiments. However, the one or more first light generating devices may comprise one or more first light emitting diode (LED) filaments, or one or more phosphor covered LEDs, or one or more (phosphor covered) COBs, or a combination of two or more of LED filaments, (phosphor covered) phosphor covered LEDs, and COBs. Hence, embodiments of light sources and luminescent materials may also relate to phosphor covered LEDs or (phosphor covered) COBs.

[0041] In embodiments, the light generating system may be configured to generate, in the first operational mode, system light comprising the first device light. Hence, in embodiments, the system light may be white light. Additionally, in embodiments, the system light may have a color rendering index of at least 70,. Further, in embodiments, the system light may have a correlated color temperature selected from the range of 1500-8000 K, such as from the range of 1500-6500 K, especially from the range of 1800-6500 K. In specific embodiments, the light generating system may be configured to in the first operational mode of the light generating system generate system light having a correlated color temperature selected from the range of 1500-6500 K. In embodiments, the system light may have a CRI of at least 80, especially at least 85. Further, the light generating system may be configured to, in the first operational mode, adjust the correlated color temperature of the system light. Especially, in embodiments, the light generating system may be configured to adjust the correlated color temperature of the system light by altering the correlated color temperature of the first device light (as described above). For instance, the intensity of the first device light generated by the second of the at least two different types of first LED filaments may be (essentially) 0 (i.e., the second of the at least two different types of first LED filaments may be switched off), such that the system light may have a correlated color temperature Ti as defined above. Conversely, the intensity of the first device light generated by the first of the at least two different types of first LED filaments may be (essentially) 0 (i.e., the first of the at least two different types of first LED filaments may be switched off), such that the system light may have a correlated color temperature T2 as defined above. Further, both the first of the at least two different types of first LED filaments and the second of the at least two different types of first LED filaments may generate light having (un)equal intensities, such that the system light may have a correlated color temperature between Ti and T2. In embodiments, the light generating system may thus be configured to generate, in the first operational mode, system light having a correlated color temperature selected from the range of Ti - T2, wherein IT1-T2I > 250 K, such as IT1-T2I > 500 K, especially IT1-T2I > 750 K, more especially IT1-T2I > 1000 K. Further, in embodiments, IT1-T2I < 5000 K, such as IT1-T2I < 4500 K, especially IT1-T2I < 4000 K. Such a light generating system may provide system light having a range of correlated color temperatures. Hence, the light generating system may be beneficial for applications where it is desired to alter the properties of the system light over time (such as during the day). Especially, in embodiments, the correlated color temperature of the system light (generated by the light generating system) may be altered by a control system (see below).

[0042] In embodiments, the system light may (further) comprise the second device light. The second device light may especially be generated by the one or more second light generating devices. Hence, in embodiments, the light generating system may comprise the one or more second light generating devices. Especially, in embodiments, the light generating system may comprise 1-20 second light generating devices, such as 2-15 second light generating devices, especially 3-10 second light generating devices. However, other numbers may also be possible. In embodiments, the one or more second light generating devices may be configured external from the light transmissive enclosure, especially from the enclosure volume. Further, in embodiments, the one or more second light generating devices may be configured radially surrounding the light transmissive enclosure. Especially, in embodiments, the one or more second light generating devices may be configured at a first distance di from the outer face of the light transmissive enclosure. In embodiments, the first distance di may be selected from the range of 0.1-65 mm, such as from the range of 0.5-50 mm, especially from the range of 1-40 mm. Such a distance di may in embodiments reduce the amount of heat transferred between the one or more second light generating devices and the light transmissive enclosure.

[0043] In embodiments, the one or more second light generating devices may comprise one or more second LED filaments. In specific embodiments, each of the one or more second light generating devices may comprise one second LED filament. Hence, in embodiments, the light generating system may comprise 1-20, such as 2-15, especially 3-10 second LED filaments. The one or more second LED filaments may be configured to generate the second device light. In embodiments, the one or more second LED filaments may (each) comprise second solid state light sources and a second (elongated) encapsulant. In embodiments, the second solid state light sources may be equal to the first solid state light sources, though this need not be the case. In embodiments, the second solid state light sources may be configured to, during operation, generate second solid state light source light. In specific embodiments, the second solid state light source light may be blue light, such as light having a centroid wavelength selected from the range of 200-490 nm, such as from the range of 400-490 nm, especially from the range of 440-490 nm. Further, in embodiments, the second encapsulant may comprise one or more of a (second) luminescent material and a light scattering material. In embodiments, at least one of the one or more second LED filaments may comprise a second encapsulant comprising a second luminescent material. In embodiments, the second luminescent material may be configured to convert at least part, such as all, of the (blue) second solid state light source light into second luminescent material light. In embodiments, the second luminescent material light may especially be colored light, such as selected from the group comprising green light, yellow light, orange light, and red light. Further, in embodiments, the second device light (of the at least one of the one or more second LED filaments) may comprise at least part of the second luminescent material light. Hence, in embodiments, the second device light (of the at least one of the one or more second LED filaments) may be colored light, such as selected from the group comprising green light, yellow light, orange light, and red light. Hence, in specific embodiments, at least one of the one or more second LED filaments may comprise second solid state light sources and a second luminescent material, wherein the second solid state light sources may be configured to generate second solid state light source light, and wherein the second luminescent material may be configured to convert at least part of the second solid state light source light into second luminescent material light; wherein the second device light of the at least one of the one or more second LED filaments may comprise at least part of the second luminescent material light, and wherein this second device light may be colored light. Generating colored (second) device light using a (second) luminescent material may be more energy-efficient than using solid state light sources configured to generate solid state light source light having the same color.

[0044] Further, in embodiments, the second solid state light sources of at least one of the one or more second LED filaments may be configured to (during operation) generate colored second solid state light source light. Especially, in embodiments, the second solid state light sources (of said at least one of the one or more second LED filaments) may be configured to generate one or more of blue solid state light source light, green solid state light source light, yellow solid state light source light, orange solid state light source light, and red solid state light source light. That is, the second solid state light sources (of said at least one of the one or more second LED filaments) may be one or more of blue LEDs, green LEDs, yellow LEDs, orange LEDs, and red LEDs. In such embodiments, the second encapsulant may not comprise the second luminescent material, i.e., the second solid state light source light may not be converted into second luminescent material light (in the second encapsulant). Further, in such embodiments, the second encapsulant may comprise the light scattering material. In embodiments, the light scattering material may be configured to scatter and / or diffuse the solid state light source light, especially in a direction transverse to a normal of the (first and / or second) major surface. In specific embodiments, the light scattering material may comprise light scattering particles, such as e.g. at least one of BaSCU, A12O3 and TiCh particles. In embodiments, the second encapsulant (of said at least one of the one or more second LED filaments) may thus be configured to provide scattered and / or diffused second solid state light source light (upon irradiation with second solid state light source light). Further, in embodiments, the device light (of said at least one of the one or more second LED filaments) may comprise at least part, such as all, of the (scattered and / or diffused) second solid state light source light. Hence, in embodiments, the device light may comprise (at least part of) the second solid state light source light, wherein the second solid state light source light may especially be colored light. Hence, in specific embodiments, at least one of the one or more second LED filaments may comprise second solid state light sources, wherein the second solid state light sources may be configured to generate second solid state light source light; wherein the second device light of the at least one of the one or more second LED filaments may comprise at least part of the second solid state light source light, and wherein this second device light may be colored light. Generating colored (second) device light using (second) solid state light sources configured to generate light having the desired color and / or centroid wavelength may provide colored light having improved color saturation, especially compared to a configuration using luminescent material light (of the same color).

[0045] In embodiments, at least one of the one or more second LED filaments may comprise a plurality of second solid state light sources, wherein the plurality of second solid state light sources are configured to generate second solid state light source light having the same spectral power distribution. Additionally or alternatively, in embodiments, at least one of the one or more second LED filaments may comprise a plurality of second solid state light sources, wherein the plurality of second solid state light sources are configured to generate second solid state light source light having different spectral power distributions. Further yet, in embodiments, the one or more second light generating devices (comprising the one or more second LED filaments) may be configured to generate second device light having different spectral power distributions. Hence, in embodiments, the light generating system, especially the one or more second light generating devices, may (at least) comprise (one or more of) a first type of second light generating device, wherein the first type of second light generating devices may be configured to generate first type of second device light. In such embodiments, the first type of second device light may especially have a first centroid wavelength. The first centroid wavelength may be selected from the blue wavelength range, such as from the range of 400-490 nm, especially from the range of 440-490 nm. In embodiments, the second device light may comprise the first type of second device light. Further, in embodiments, the light generating system, especially the one or more second light generating devices, may comprise (one or more of) a second type of second light generating device, wherein the second type of second light generating devices may be configured to generate second type of second device light. In such embodiments, the second type of second device light may especially have a second centroid wavelength. The second centroid wavelength may in specific embodiments be selected from the green wavelength range, such as from the range of 490-560 nm, especially from the range of 510-540 nm. In embodiments, the second device light may comprise the second type of second device light. Further, in embodiments, the light generating system, especially the one or more second light generating devices, may comprise (one or more of) a third type of second light generating device, wherein the third type of second light generating devices may be configured to generate third type of second device light. In such embodiments, the third type of second device light may especially have a third centroid wavelength. The third centroid wavelength may in specific embodiments be selected from the orange-red wavelength range (i.e. 590-780 nm wavelength range), such as from the range of 590-750 nm, especially from the range of 600-700 nm. In embodiments, the second device light may comprise the third type of second device light. In embodiments, the one or more second light generating devices may thus be configured to generate second device light having intensity at one or more wavelengths in the visible wavelength range. Further, in specific embodiments, the light generating system may comprise one or more of (i) a first type of second light generating devices configured to generate first type of second device light having a first centroid wavelength in the blue wavelength range, and (ii) a second type of second light generating devices configured to generate second type of second device light having a second centroid wavelength in the green wavelength range. Further yet, in specific embodiments, the light generating system may comprise a third type of second light generating devices configured to generate third type of second device light having a third centroid wavelength in the orange-red wavelength range. A light generating system comprising different types of second light generating devices as described here may facilitate generating system light having a specific color. Further, in embodiments, the different types of second light generating devices may facilitate changing the color of the system light, especially during operation of the light generating system. As such, the light generating system may provide decorative lighting effects.

[0046] In embodiments, the different types of second light generating devices described above may provide second device light comprising one or more of the three primary colors of light (i.e., (orange-)red (R), green (G), and blue (B)). As such, the color point of the system light, especially of the second device light, may be controlled within the RGB color space. Further, in embodiments, the first type of second device light, second type of second device light, and third type of second device light may be combined to provide white second device light, such as white second device light having a correlated color temperature selected from the range of 1500-8000 K. Additionally, one or more of the first type of second device light, second type of second device light, and third type of second device light may be admixed with the first device light. Admixing one or more of the first type of second device light, second type of second device light, and third type of second device light with the first device light may facilitate changing the correlated color temperature of the (white) system light to outside of the range of correlated color temperatures obtainable by the first device light (alone) (e.g. by increasing the red or blue component in the system light). Hence, in embodiments, the light generating system may be configured to generate (white) system light comprising one or more of (at least part of) the first device light and (at least part of) the second device light. In embodiments, the light generating system may especially be configured to generate (such) white system light in the first operational mode. Hence, in specific embodiments, the light generating system may be configured such that in the first operational mode of the light generating system the system light may be white light comprising at least part of the first device light and at least part of the second device light. Such a configuration of the light generating system may facilitate changing the correlated color temperature and / or CRI of the white system light by changing the relative intensities of the first device light and second device light.

[0047] Here above, the second light generating devices are especially described in terms of LED filament embodiments. However, the one or more second light generating devices may comprise one or more second light emitting diode (LED) filaments, or one or more (optionally phosphor covered) LEDs, or one or more (phosphor covered) COBs, or a combination of two or more of LED filaments, (optionally phosphor covered) phosphor covered LEDs, and COBs. Hence, embodiments of light sources and luminescent materials may also relate to (optionally phosphor covered) LEDs or (phosphor covered) COBs. Hence, the one or more second light generating devices may in embodiments also comprise direct LEDs (i.e. LEDs without phosphors). Yet, in embodiments the one or more second light generating devices may comprise one or more LED filaments, wherein the encapsulants of the one or more LED filaments do not comprise a luminescent material. Hence, the filament light of such LED filaments may essentially consist of the LED light of the LEDs of the filaments.

[0048] In embodiments, the light generating system may have a second operational mode. In the second operational mode, the light generating system may be configured to generate system light comprising the second device light, and optionally at least part of the first device light. Further, in the second operational mode, the light generating system may be configured to change the relative intensities of the first type of second device light, the second type of second device light, and the third type of second device light. Hence, in embodiments, in the second operational mode, the light generating system may be configured to generate system light comprising a relatively larger component of blue light, green light, and / or orange-red light. That is, in embodiments, in the second operational mode, the system light may be colored light, especially having a color from the RGB color space. Hence, in specific embodiments, the light generating system may be configured to generate in a second operational mode of the light generating system non-white system light. Such a second operational mode may provide decorative lighting effects. Further, such a second operational mode may be suitable for applications where e.g. it may be desired to reduce the ratio of blue light in the system light over time, e.g. to facilitate simulating a sunset.

[0049] As indicated, the light transmissive enclosure may be (at least partly) transmissive for the second device light. Hence, in embodiments, the second device light may be incident on the one or more first light generating devices, such as especially on the one or more first LED filaments. In embodiments, the blue light (generated by the first type of second light generating devices) may be absorbed by the first luminescent material comprised by the one or more first LED filaments, and subsequently converted into first luminescent material light. In embodiments, this may generate a soft glow around the one or more first light generating devices, leading to a decorative effect. Yet, in embodiments, such a glow may not be desired. Hence, the light generating system may comprise an optical filter. In embodiments, the optical filter may be at least partly configured between the one or more first light generating devices and the one or more second light generating devices. Further, in embodiments, the one or more second light generating devices and the optical filter may be configured such that at least part of the second device light (especially in the blue-green wavelength range) is reflected at the optical filter, especially in a direction away from the one or more first light generating devices. Additionally or alternatively, in embodiments, the one or more second light generating devices and the optical filter may be configured such that at least part of the second device light (especially in the blue-green wavelength range) may be absorbed by the optical filter. Hence, in specific embodiments, the light generating system may further comprise an optical filter at least partly configured between the one or more first light generating devices and the one or more second light generating devices; wherein the one or more second light generating devices and the optical filter may be configured such that at least part of the second device light (i) may be reflected at the optical filter in a direction away from the one or more first light generating devices, and / or (ii) may be absorbed by the optical filter. An optical filter configured between the one or more first light generating devices and the one or more second light generating devices may thus reduce the amount of second device light incident on the first luminescent material. As a result, optical crosstalk may be reduced, wherein the term “optical crosstalk” may refer to emission of first luminescent material light by the first luminescent material upon irradiation with (especially blue-green) second device light. As such optical crosstalk may alter the color and / or saturation of the system light, an optical filter may thus improve the color and / or saturation of the system light, especially in the second operational mode. Herein, the term “blue green” may in embodiments refer to light having a wavelength selected from blue-green wavelength, i.e. selected from the 440-560 nm wavelength range. Such light may in embodiments be blue, green, or comprise both colors. Note that white light may also have spectral intensity in the blue-green wavelength range.

[0050] As indicated, the optical filter may reflect and / or absorb second device light in the blue-green wavelength range. In embodiments, the optical filter may thus be reflective for at least part of the first type of second device light, and (further) optionally be reflective for at least part of the second type of second device light. Further, in embodiments, the optical filter may (thus) be transmissive for at least part of the third type of second device light. In embodiments, the optical filter may be configured to reflect and / or absorb at least 70%, such as at least 80%, especially at least 90%, including (essentially) all of the blue-green second device light received by the optical filter. Further, in specific embodiments, the optical filter may be configured to transmit at least 70%, such as at least 80%, especially at least 90%, including (essentially) all of the first device light (especially the first luminescent material light) received by the optical filter. Thus, in embodiments, the optical filter may be configured to have a higher transmission for the first device light than for the (first type of) second device light. Specifically, in embodiments, the optical filter may be transmissive for at least part of the first device light and reflective for at least part of the second device light. Such an optical filter may prevent at least part of the (especially blue-green) second device light from being incident on the one or more first light generating devices (especially the first luminescent material), yet may facilitate the transmission of first device light. Hence, the light output and / or efficiency of the light generating system may be minimally reduced, yet the optical properties (e.g. correlated color temperature, color point, etc.) of the system light may be preserved and / or increased. In embodiments, the optical filter may comprise one or more of a dichroic mirror (or “dichroic filter”), a semi-transparent mirror, a reflective mirror, and a white coating.

[0051] In embodiments, a dichroic mirror may be configured to transmit light within a first wavelength range, and reflect light within a second wavelength range. Specifically, in a first wavelength range, transmission of light (by the dichroic mirror) may be higher than reflection of light, while in a second wavelength range, reflection of light may be higher than transmission of light. Further, a dichroic mirror may have a cut-off and / or a cut-on wavelength, separating the two wavelength ranges. The cut-off wavelength may especially separate a transmissive range (shorter wavelengths) from a reflective range (longer wavelengths), while the cut-on wavelength may especially separate a reflective range (shorter wavelengths) from a transmissive range (longer wavelengths). In embodiments, an optical filter comprising a dichroic mirror may be configured to (a) reflect at least part of the second device light (especially in the blue-green wavelength range), and (b) to transmit at least part of the first device light, especially at least the first luminescent material light.

[0052] Further, in embodiments, a semi-transparent mirror may be configured to reflect part of the incoming light, and transmit the rest of the incoming light, regardless of direction, wavelength and / or polarization. Specifically, a semi-transparent mirror may be configured to (i) transmit or reflect at least 50%, such as at least 60%, especially at least 70% of the incoming light, and (ii) reflect or transmit at most 50%, such as at most 40%, especially at most 30% of the incoming light. In embodiments, a semi-transparent mirror may also be referred to as a “beam splitter”. In specific embodiments, the semi-transparent mirror may be configured such, that (i) at least 50%, such as at least 60%, especially at least 70% of the second device light is reflected, and / or (ii) at most 50%, such as at most 40%, especially at most 30% of the first device light is reflected.

[0053] In embodiments, a reflective mirror may be configured to reflect at least 70%, such as at least 80%, especially at least 90%, including (essentially) all of the incoming light, regardless of wavelength and / or polarization, while preserving the light properties (e.g. polarization). Further, in embodiments, a white coating may be configured to reflect at least 70%, such as at least 80%, especially at least 90%, including (essentially) all of the incoming light, and may optionally diffuse the incoming light upon reflection. In embodiments, a reflective mirror and / or a white coating may especially be used in an optical filter arrangement (see below).

[0054] Especially, the dichroic filter is (essentially) transparent for one or more wavelengths and (essentially) reflective for one or more other wavelengths (in the blue-green wavelength range). Especially, the absorption filter is (essentially) transparent for one or more wavelengths and (essentially) absorbing for one or more other wavelengths (in the bluegreen wavelength range).

[0055] In embodiments the optical filter may be less-transmissive for a first wavelength range 380 nm - XI and more transmissive for a second wavelength range XI - 780 nm. Defining the transmissiveness as the wavelength averaged transmission over the respective wavelengths, assuming perpendicular irradiation, the optical filter may have a ratio T1 / T2, wherein T1 is the wavelength averaged transmission of the optical filter over the wavelength range 380 nm - XI, and wherein T2 is the wavelength averaged transmission of the optical filter over the wavelength range XI - 780 nm. Especially, Tl / T2<0.5. Further, in specific embodiments Tl / T2<0.2, like Tl / T2<0.1. In specific embodiments, T1 / T2 may be essentially zero. Further, XI may be selected from the range of 450-550 nm, such as selected from the range of about 470-530 nm. For instance, XI may be selected from the range of 485- 520 nm. In embodiments, XI may be a cut-off wavelength of an optical filter.

[0056] Especially, an optical filter configured between the one or more first light generating devices and the one or more second light generating devices may thus reduce the amount of second device light incident on the first luminescent material. As a result, optical crosstalk may be reduced, wherein the term “optical crosstalk” may refer to emission of first luminescent material light (by the first luminescent material) upon irradiation with (especially blue-green) second device light.

[0057] In embodiments, the optical filter may be configured on one or more of the outer face and the inner face of the light transmissive enclosure. Hence, in embodiments, the optical filter may be configured on the inner face of the light transmissive enclosure. In such embodiments, the optical filter may have a lightguide function, i.e., the optical filter may facilitate (directing the) outcoupling of (especially) the first device light from the light transmissive enclosure. In specific embodiments, the optical filter may be configured within the enclosure. Further, in specific embodiments, the light transmissive enclosure may comprise the optical filter. Yet, especially, in embodiments the optical filter may be configured on the outer face of the light transmissive enclosure. Further, in embodiments, the optical filter may be configured (on average) closer to the one or more second light generating devices than to the one or more first light generating devices. In embodiments, the optical filter may (essentially) cover the full outer face of the light transmissive enclosure. In such embodiments, especially the blue component of the first device light may be reflected and / or absorbed by the optical filter, which may affect the correlated color temperature and / or the color rendering index of the white first device light. Hence, in such embodiments, in the first operational mode, the light generating system may be configured to generate white light comprising at least part of the first device light and at least part of the (first type of) second device light. Alternatively, the optical filter may cover 10-90%, such as 20-80%, especially 25-75% of the outer face of the light transmissive enclosure. In embodiments, the optical filter may comprise an optical filter arrangement of a plurality of optical filter parts spatially separated by light transmissive parts. The light transmissive parts may in embodiments be comprised by the light transmissive material (comprised by the light transmissive enclosure). Yet, in embodiments, the light transmissive parts may be separate light transmissive parts, e.g. configured on the outer face of the light transmissive enclosure. In embodiments, the plurality of optical filter parts may especially be configured in the optical path of the (blue-green) second device light towards the first luminescent material, i.e., the plurality of optical filter parts may be configured (on the outer face of the light transmissive enclosure) between a second light generating device and at least one closest first light generating device. Further, the optical filter arrangement may be configured such that at least part of the second device light (in the blue-green wavelength range) may be reflected at the optical filter parts in a direction away from the one or more first light generating devices. Additionally, in embodiments, another part of the second device light (in the blue-green wavelength range) may be transmitted via the light transmissive parts (yet without irradiating the one or more first light generating devices). Hence, in specific embodiments, the optical filter may comprise an optical filter arrangement of a plurality of optical filter parts spatially separated by light transmissive parts; wherein the optical filter arrangement is configured to such that at least part of the second device light may be reflected at the optical filter parts in a direction away from the one or more first light generating devices, whereas another part of the second device light may be transmitted via the light transmissive parts. An optical filter arrangement may reduce the absorption and / or reflection of (especially the blue component of) the first device light by the optical filter. Hence, the optical filter arrangement may improve the color rendering index and / or the correlated color temperature of the white first device light. In such embodiments, the (white) first device light outcoupled from the light generating system may therefore especially have intensity in the blue-green wavelength range. As such, the first device light may in embodiments not be admixed with (first type of) second device light to generate white light having a correlated color temperature in the range of 1500-8000 K (and optionally a color rendering index of at least 80). Hence, a light generating system comprising the optical filter arrangement may be configured to generate white system light consisting (only) of first device light. Specifically, the first device light may have intensity in the blue-green wavelength range; wherein at least one of the one or more first LED filaments and the optical filter may be configured such that in the first operational mode of the light generating system the system light is white light consisting of first device light. Generating white system light (only) consisting of first device light may provide white system light with increased homogeneity, as the blue component of the white light may not be generated by a light generating device separate from the light generating device generating the other (green and red) components.

[0058] As indicated, in embodiments, the light generating system may comprise a control system. The control system may especially be configured to control one or more of a spectral power distribution, a correlated color temperature, a color point, and a color rendering index of the system light. Further, the control system may be configured to switch the light generating system from the first operational mode to the second operational mode. Hence, in specific embodiments, the light generating system may further comprise a control system configured to control a spectral power distribution of the system light. The control system may allow a user to change the relative intensities of one or more of the different types of first device light, the first type of second device light, the second type of second device light, and the third type of second device light.

[0059] 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 on the element, such as e.g. measuring, displaying, actuating, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. The controlling of the element can be done with a control system. 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.

[0060] The control system may also be configured to receive and execute instructions from a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc.. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system. 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 light generating system may be identifiable with a code, especially a unique code for the respective light generating system. The control system of the light generating system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

[0061] Further, in embodiments, the light generating system may comprise a second light transmissive enclosure (“second enclosure”) . The second light transmissive enclosure may comprise a second light transmissive material. In embodiments, the second light transmissive material may be selected from the group comprising glass and (optically transparent) polymeric materials. Further, the second light transmissive enclosure may define a second enclosure volume. In embodiments, the second light transmissive enclosure may enclose at least part of the first enclosure. Further, in embodiments, the one or more second light generating devices may be (at least partly) configured in the second enclosure volume (yet not in the first enclosure volume). Hence, in specific embodiments, the light generating system may further comprise a second light transmissive enclosure, wherein the second light transmissive enclosure may comprise a second light transmissive material; wherein the second light transmissive enclosure may define a second enclosure volume; wherein the second light transmissive enclosure may enclose at least part of the first enclosure; wherein the one or more second light generating devices may be at least partly configured in the second enclosure volume. The second light transmissive enclosure may protect the one or more second light generating devices against dirt, ingress, and / or damage. Further, the second light transmissive enclosure may provide a decorative effect, e.g. when the second light transmissive enclosure is patterned. In embodiments, the second light transmissive enclosure may thus especially comprise the one or more second light generating devices. Specifically, in embodiments, the one or more second light generating devices may be (at least partly) configured in the second enclosure volume. Hence, in embodiments, the second light transmissive enclosure may be hollow, i.e., the second light transmissive material may especially be configured as a wall surrounding the second enclosure volume. Further, the second light transmissive enclosure, especially the second light transmissive material, may comprise a second inner face and a second outer face, wherein the second inner face may be configured facing the (first) light transmissive enclosure (and the one or more second light generating devices), and wherein the second outer face may be configured facing away from the light transmissive enclosure. Hence, in embodiments, the second light transmissive enclosure, especially the second inner face, may define the second enclosure volume. In embodiments, the second light transmissive enclosure may comprise a second equivalent spherical diameter D2. In embodiments, the second equivalent spherical diameter D2 may be selected from the range of 3-17 cm, such as from the range of 5-15 cm, especially from the range of 5-12 cm. Further, in embodiments, the second enclosure volume may especially be the volume between the second inner face and the (first) outer face (comprised by the light transmissive enclosure). Hence, in embodiments, the second enclosure volume V2 may essentially be determined by V2 = (l / 6)*7t*(D23-Di3). Especially, D2>DI, such as D2 / DI>1.1, such as D2 / DI>1.2. In embodiments, 1.1< D2 / DI<2.5.

[0062] Note that the volume between the second inner face and the (first) outer face (comprised by the light transmissive enclosure) may not be in gaseous contact with the first enclosure volume.

[0063] In embodiments, the second light transmissive enclosure may contain a second gas, especially in the second enclosure volume. Preferably, the second gas may be different from the thermally conductive gas. In embodiments, (i) the second gas may comprise air, (ii) the second gas and the thermally conductive gas may have different gas compositions (e.g. containing different substances / molecules and / or different substance / molecule concentrations), (iii) the thermally conductive gas may have a first pressure Pl in the enclosure volume, the second gas may have a second pressure P2 in the second enclosure volume, the second pressure P2 may be lower than the first pressure Pl, and / or (iv) the thermally conductive gas may have a thermal conductivity higher than the second gas. Such embodiments may provide improved reliability, optical performance and / or lifetime for the one or more first light generating devices which are e.g. more suspectable for reliability issues, thermal issues and / or degradation / lifetime issues than the one or more second light generating devices. In embodiments, the second gas may have a thermal conductivity (at 22 °C and a pressure of 1 bar) selected from the range of < 0.06 W*m'1*K'1, such as from the range of < 0.04 W*m'1*K'1, especially from the range of < 0.03 W*m'1*K'1. Additionally or alternatively, in embodiments, the second gas may have a thermal conductivity (at 22 °C and a pressure of 1 bar) selected from the range of > 0.01 W*m'1*K'1, such as from the range of > 0.015 W*m'1*K'1, especially from the range of > 0.02 W*m'1*K'1. In embodiments, the second gas may comprise (atmospheric) air. Especially, the second gas may comprise He in a percentage of at most 10%, such as at most 5%, especially at most 2%, including (essentially) 0%. Further, in embodiments, the second gas may comprise H2 in a percentage of at most 10%, such as at most 5%, especially at most 2%, including (essentially) 0%. Further yet, in embodiments, the second gas may comprise Ne in a percentage of at most 10%, such as at most 5%, especially at most 2%, including (essentially) 0%. In general, the concentration of at least one gas selected from He, Ne, and H2, in the first enclosure volume is higher than in the second enclosure volume.

[0064] In embodiments, the second gas may have a second pressure P2 (at a temperature of 22 °C) in the second enclosure volume. In embodiments, the second pressure P2 may be selected from the range of 0.5-5 bar, such as from the range of 0.8-2.5 bar, especially from the range of 1-2 bar. Further, in embodiments, the second pressure P2 may be lower than the first pressure Pi. In embodiments, P1-6 bar < P2 < Pi, such as Pi-4 bar < P2 < Pi, especially Pi-2 bar < P2 < Pi. Especially, when the light generating system is in the off- state, the second gas may have atmospheric pressure in the second enclosure volume (at 22 °C).

[0065] In embodiments, the second light transmissive enclosure may especially comprise a second light transmissive material. Especially, the second light transmissive material may transmit 90% or higher, such as 95% or higher, especially 99% or higher, more especially 99.5% or higher, including 100% of the first device light and the second device light when perpendicularly incident on the second light transmissive enclosure. Hence, the second light transmissive enclosure may especially be transmissive for incident second device light (and the first device light), and the second device light (and the first device light) may escape via the first light transmissive enclosure. Hence, in embodiments the second light transmissive enclosure may be transparent for the first device light and for the second device light. Furthermore, in some embodiments, the second light generating enclosure may form a hermetic seal (i.e., especially watertight, more especially airtight) with the support and thus, protect the light generating device from the ingress of dust, dirt, and pollutants. In embodiments the second light transmissive enclosure together with the support may provide a (second) enclosure volume with an IP44 or higher classification. However, other embodiments may thus also be possible.

[0066] The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to (at least) visible light. The terms “blue light” or “blue emission”, and similar terms, may especially relate to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues). In specific embodiments, the blue light may have a centroid wavelength in the 440-490 nm range. The terms “green light” or “green emission”, and similar terms, may especially relate to light having a wavelength in the range of about 490-560 nm. In specific embodiments, the green light may have a centroid wavelength in the 490-560 nm range. The terms “yellow light” or “yellow emission”, and similar terms, may especially relate to light having a wavelength in the range of about 560-590 nm. In specific embodiments, the yellow light may have a centroid wavelength in the 560-590 nm range. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590-620 nm. In specific embodiments, the orange light may have a centroid wavelength in the 590-620 nm range. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-750 nm. In specific embodiments, the red light may have a centroid wavelength in the 620-750 nm range. The phrase “light having a wavelength in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least an intensity or intensities at the wavelength in the indicated wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at at least a wavelength in the 440-495 nm wavelength range.

[0067] The system, or apparatus, or device may execute an action in a “mode” or “operational mode”. The term “operational mode may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operational mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and / or after executing the mode one or more other modes may be executed.

[0068] 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 operational mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operational mode (i.e. “on”, without further tunability).

[0069] 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.

[0070] In embodiments, the light generating system may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating system (or luminaire) may be part of or may be applied in e.g. optical communication systems or disinfection systems.

[0071] Hence, in a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc. The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a lighting device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, an automotive lighting device, and an optical wireless communication device, comprising the light generating system as defined herein. The lighting device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system.

[0072] BRIEF DESCRIPTION OF THE DRAWINGS

[0073] 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:

[0074] Fig. 1 A-D schematically depict embodiments of the light generating system;

[0075] Fig. 2 schematically depicts an embodiment of a first and second LED filament;

[0076] Fig. 3 A-B schematically depict embodiments of the system light; and Fig. 4 schematically depicts an embodiment of the lighting device. The schematic drawings are not necessarily to scale.

[0077] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0078] Fig. 1 A schematically depicts an embodiment of the light generating system 1000. The light generating system 1000 may comprise one or more first light generating devices 110, one or more second light generating devices 120, and a light transmissive enclosure 500. In embodiments, the light transmissive enclosure 500 may comprise a light transmissive material 505. Further, the light transmissive enclosure 500 may be hollow. Hence, the light transmissive enclosure 500, especially the light transmissive material 505, may comprise an inner face 501 and an outer face 502. The inner face 501 may especially be configured facing the center of the light transmissive enclosure 500, and the outer face 502 may be configured facing away from the light transmissive enclosure 500. In embodiments, the light transmissive enclosure 500 may comprise a first equivalent spherical diameter Di. In embodiments, the first equivalent spherical diameter Di may be selected from the range of 2- 15 cm. Further, the light transmissive enclosure 500 (especially the inner face 501) may define an enclosure volume 507. In embodiments, the light transmissive enclosure 500 may contain a thermally conductive gas 509. The thermally conductive gas 509 may in embodiments comprise He in a percentage of at least 10%. Further, the thermally conductive gas 509 may comprise He in a percentage of at least 60%. In specific embodiments, the thermally conductive gas 509 may comprise He in a percentage of at least 99%. Additionally or alternatively, the thermally conductive gas 509 may comprise H2 in a percentage of at least 1%. Further, in embodiments, the thermally conductive gas 509 may comprise Ne, such as at least 1%, like at least 10%. In embodiments, the thermally conductive gas 509 may have a thermal conductivity (at 22 °C and a pressure of 1 bar) selected from the range of > 0.06 W*m'1*K'1. In embodiments, the thermally conductive gas 509 may have a first pressure Pi (at a temperature of 22 °C) in the enclosure volume 507 selected from the range of 1-10 bar.

[0079] In embodiments, the one or more first light generating devices 110 may be configured in the enclosure volume 507. Additionally, the one or more first light generating devices 110 may be configured to generate first device light 111 having intensity at one or more wavelengths in the visible wavelength range. Further, the one or more first light generating devices 110 may comprise one or more first LED filaments 115. The one or more first LED filaments 115 may comprise (a plurality of) first solid state light sources 10 and a first luminescent material 210 (see Fig. 2). The first solid state light sources 10 may especially be configured to generate first solid state light source light 11. Further, the first luminescent material 210 may be configured to convert at least part of the first solid state light source light 11 into first luminescent material light 211. In embodiments, the first device light 111 may comprise at least part of the first luminescent material light 211. In embodiments, the one or more second light generating devices 120 may be configured external from the enclosure volume 507 (i.e., the enclosure volume 507 may not comprise the one or more second light generating devices 120). The one or more second light generating devices 120 may in embodiments comprise one or more second LED filaments 125. In embodiments, the one or more second light generating devices 120 may be configured to generate second device light 121 having intensity at one or more wavelengths in the visible wavelength range. In embodiments, the light generating system 1000 may be configured to generate system light 1001 comprising at least part of the first device light 111. Additionally or alternatively, the light generating system 1000 may be configured to generate system light 1001 comprising at least part of the second device light 121. Further, in embodiments, the light generating system 1000 may be configured such that in a first operational mode of the light generating system 1000 the system light 1001 is white light. Especially, the light generating system 1000 may be configured to generate, in the first operational mode of the light generating system 1000 system light 1001 having a correlated color temperature selected from the range of 1500-8000 K, such as from the range of 1500-6500 K.

[0080] In embodiments, the light generating system 1000 may comprise at least two different types of first LED filaments 115. In embodiments, a first of the at least two different types of first LED filaments 115 may be configured to generate first device light 111 having a correlated color temperature Ti selected from the range of 1750-8000 K. Further, in embodiments, a second of the at least two different types of first LED filaments 115 may be configured to generate first device light 111 having a correlated color temperature T2 selected from the range of 1500-7000 K. Hence, the light generating system 1000 may comprise at least two different types of first LED filaments 115 configured to generate first device light 111 having correlated color temperatures differing at least 500 K. Further, the light generating system 1000 may be configured to adjust the relative intensities of the first device light 111 generated by the first of the at least two different types of first LED filaments 115 and the second of the at least two different types of first LED filaments 115, respectively. Hence, the light generating system 1000 may be configured to generate in the first operational mode of the light generating system 1000 system light 1001 having a correlated color temperature selected from the range of Ti - T2, wherein |Ti - T2I > 1000 K.

[0081] The light generating system 1000 may further comprise a second light transmissive enclosure 1500. The second light transmissive enclosure 1500 may especially comprise a second light transmissive material 1505. Further, the second light transmissive enclosure 1500 may define a second enclosure volume 1507. In embodiments, the second light transmissive enclosure 1500 may enclose at least part of the first enclosure 500. Further, in embodiments, the one or more second light generating devices 120 may be (at least partly) configured in the second enclosure volume 1507 (yet not in the first enclosure volume 507). The second light transmissive enclosure 1500, especially the second light transmissive material 1505, may comprise a second inner face 1501 and a second outer face 1502, wherein the second inner face 1501 may be configured facing the light transmissive enclosure 500 (and the center of the second light transmissive enclosure 1500), and wherein the second outer face 1502 may be configured facing away from the light transmissive enclosure 500. In embodiments, the second light transmissive enclosure 1500 may comprise a second equivalent spherical diameter D2. In embodiments, the second equivalent spherical diameter D2 may be selected from the range of 3-17 cm. Further, in embodiments, the second enclosure volume 1507 may especially be the volume between the second inner face 1501 and the outer face 502 (comprised by the light transmissive enclosure 500). In embodiments, the second light transmissive enclosure 1500 may contain a second gas, especially in the second enclosure volume 1507. In embodiments, the second gas may comprise (atmospheric) air. The light generating system 1000 may further comprise an optical filter 550. The optical filter 550 may especially be configured between the one or more first light generating devices 110 and the one or more second light generating devices 120. In embodiments, optical filter 550 may be configured to reflect and / or absorb at least 70% of the blue-green second device light 121 received by the optical filter 550. Further, in embodiments, the optical filter 550 may be configured to transmit at least 70% of the first device light 111 (especially the first luminescent material light 211) received by the optical filter 550. Thus, in embodiments, the optical filter 550 may be configured to have a higher transmission for the first device light 111 than for (blue-green) second device light 121. Further, the one or more second light generating devices 120 and the optical filter 550 may be configured such that at least part of the second device light 121 (in the blue-green wavelength range) may be reflected at the optical filter 550 in a direction away from the one or more first light generating devices 110. Further, the one or more second light generating devices 120 and the optical filter 550 may be configured such that at least part of the second device light 121 (in the blue-green wavelength range) may be absorbed by the optical filter 550.

[0082] As depicted, the light generating system 1000 may comprise a control system 300. The control system 300 may be configured to control one or more of a spectral power distribution, a correlated color temperature, a color point, and a color rendering index of the system light 1001. Further, the control system 300 may be configured to switch the light generating system 1000 from the first operational mode to the second operational mode.

[0083] Fig. IB schematically depicts another embodiment of the light generating system 1000. In embodiments, as depicted in Fig. 1A, the optical filter 550 may be configured within the enclosure 500. Yet, as depicted here (in Fig. IB), the optical filter 550 may be comprised by the enclosure 500. In further embodiments, the optical filter 550 may be configured on one or more of the outer face 502 and the inner face 501 of the light transmissive enclosure 500. In embodiments, the optical filter 550 may comprise one or more of a dichroic mirror, a semi-transparent mirror, a reflective mirror, and a white coating. Especially, the optical filter 550 may be transmissive for at least part of the first device light 111 and reflective for at least part of the second device light 121 (in the blue-green wavelength range).

[0084] Fig. 1C schematically depicts a cross-sectional top view of an embodiment of the light generating system 1000. In embodiments, the light generating system 1000 may comprise a first type of second light generating devices 1210, wherein the first type of second light generating devices 1210 may be configured to generate first type of second device light 1211. The first type of second device light 1211 may especially have a first centroid wavelength in the blue wavelength range. Further, the second device light 121 may comprise the first type of second device light 1211. Additionally or alternatively, the light generating system 1000 may comprise a second type of second light generating devices 1220, wherein the second light generating devices 1220 may be configured to generate second type of second light 1221. In embodiments, the second type of second device light 1221 may have a second centroid wavelength in the green wavelength range. Further, the second device light 121 may comprise the second type of second light 1221. In embodiments, the optical filter 550 may be reflective for at least part of the first type of second device light 1211. Optionally, the optical filter 550 may be reflective for at least part of the second type of second device light 1221. Further, the light generating system 1000 may comprise a third type of second light generating devices 1230, wherein the third type of second light generating devices 1230 may be configured to generate third type of second device light 1231. In embodiments, the third type of second device light 1231 may especially have a third centroid wavelength in the orange-red wavelength range. Further, the second device light 121 may comprise the third type of second device light 1231. In embodiments, the optical filter 550 may be transmissive for at least part of the third type of second device light 1231.

[0085] Fig. ID schematically depicts an embodiment of the light generating system 1000 wherein the optical filter 550 may comprise an optical filter arrangement of a plurality of optical filter parts 5011 spatially separated by light transmissive parts 5012. Here, the light transmissive parts 5012 are comprised by the light transmissive material 505, though this need not be the case. In embodiments, the optical filter arrangement may be configured such that at least part of the second device light 121 (in the blue-green wavelength range) may be reflected at the optical filter parts 5011 in a direction away from the one or more first light generating devices 110, whereas another part of the second device light 121 (in the bluegreen wavelength range) may be transmitted via the light transmissive parts 5012. In such embodiments, the transmitted second device light 121 (in the blue-green wavelength range) may especially not irradiate the one or more first light generating devices 110. As depicted in Fig. ID, the plurality of optical filter parts 5011 may therefore especially be configured in the optical path of the (blue-green) second device light 121 towards the one or more first light generating devices 110 (especially towards the first luminescent material 210), i.e., the plurality of optical filter parts 5011 may be configured between a second light generating device 120 and at least one closest first light generating device 110. In the embodiment depicted in Fig. ID, the plurality of optical filter parts 5011 are each configured between a second light generating device 120 and the two closest first light generating devices 110.

[0086] In embodiments, the first device light 111 may have intensity in the blue-green wavelength range. Such blue-green first device light 111 may in embodiments be transmitted via the light transmissive parts 5012. Hence, at least one of the one or more first LED filaments 115 and the optical filter 550 may be configured such that in the first operational mode of the light generating system 1000 the system light 1001 may be white light consisting of first device light 111.

[0087] Fig. 2 schematically depicts an embodiment of a first LED filament 115 comprised by the one or more first light generating devices 110 (top) and a second LED filament 125 comprised by the one or more second light generating devices 120 (bottom). The one or more first LED filaments 115 may (each) comprise first solid state light sources 10, such as a plurality of light emitting diodes (LEDs). The first solid state light sources 10 (e.g. LEDs) may especially be arranged in a linear array, arranged on (at least) a first major surface 1051 of an elongated carrier 1050. Here, the first solid state light sources 10 are arranged on both the first major surface 1051 and a second major surface 1052 of the elongated carrier 1050. In embodiments, the first solid state light sources 10 may be configured to emit first solid state light source light 11, wherein the first solid state light source light 11 may have a centroid wavelength in the blue wavelength range. Further, each of the one or more first LED filaments 115 may comprise an encapsulant 200 at least partly covering (i) at least part of the total number of first solid state light sources 10, and (ii) at least one of the first major 1051 or the second major surface 1052. In embodiments, the one or more first LED filaments 115 (especially the encapsulant 200 comprised by the one or more first LED filaments 115) may comprise the first luminescent material 210 (configured embedded in the encapsulant 200). Yet, in embodiments, (each of) the one or more first LED filaments 115 may comprise one or more luminescent materials, such as selected from the group of divalent europium comprising oxynitride type luminescent materials, divalent europium comprising nitride type luminescent materials, trivalent cerium comprising garnet type luminescent materials, and tetravalent manganese comprising hexa-fluoride type luminescent materials. In embodiments, the first luminescent material 210 may be configured to convert light source light 11 received by the first luminescent material 210 into first luminescent material light 211. In embodiments, the first device light may comprise the first luminescent material light 211 and (optionally) at least part of the first solid state light source light 11. Turning to the second LED filament 125, in embodiments, at least one of the one or more second LED filaments 125 may comprise second solid state light sources 20 and a second luminescent material 220 (configured embedded in the encapsulant 200). The second solid state light sources 20 may especially be configured to generate second solid state light source light 21. Further, the second luminescent material 220 may be configured to convert at least part of the second solid state light source light 21 into second luminescent material light 221. In such embodiments, the second device light 121 of said at least one of the one or more second LED filaments 125 may comprise at least part of the second luminescent material light 211. Said second device light 125 may then especially be colored light. Alternatively, the encapsulant 200 comprised by the one or more second LED filaments 125 may not comprise the second luminescent material 220. However, in such embodiments, the encapsulant 200 (comprised by the one or more second LED filaments 125) may comprise a light scattering material, such as light scattering particles 230. In embodiments, at least one of the one or more second LED filaments 125 may comprise second solid state light sources 20 (and no second luminescent material 220), wherein the second solid state light sources 20 may be configured to generate (colored) second solid state light source light 21. In such embodiments, the second device light 121 of said at least one of the one or more second LED filaments 125 may comprise at least part of the second solid state light source light 21 (and not the second luminescent material light 221), wherein this second device light 125 may especially be colored light.

[0088] Fig. 3 A schematically depicts a spectral power distribution of the first device light 111 and the second device light 121 (especially the first type of second device light 1211). As depicted, the first device light 111 (especially the first solid state light source light 11) may have (emission) intensity in the blue-green wavelength region. Further, the first device light 111 (especially the first luminescent material light 211) may have broadband (emission) intensity in the longer wavelength range (such as in one or more of the green, yellow, orange, and red wavelength range). Such a combination of emission peaks may specially facilitate the generation of white light. Hence, the one or more first light generating devices 110 (especially the one or more first LED filaments 115) may be configured to generate white first device light 111. Especially, the one or more first LED filaments 115 may be configured to generate first device light 111 having a correlated color temperature selected from the range of 1500-6500 K. Additionally, the first device light 111 may have a color rendering index of at least 80. Further, as depicted, the second device light 121, especially the first type of second device light 1211, may have intensity in the blue-green wavelength range.

[0089] Fig. 3 A further schematically depicts two options for the optical filter 550, indicated by references A and B. As depicted, the first option A for the optical filter 550 has low transmittance for light in the blue-green wavelength region. Hence, such an optical filter 550 may reflect most (such as essentially all) of the first device light 111 having intensity in the blue-green wavelength region. As such, the first device light 111 outcoupled from the light generating system 1000 may (essentially) be devoid of light in the blue-green wavelength region. Further, the second option B for the optical filter 550 may have relatively higher transmittance for light in the blue-green wavelength region. Yet, some blue-green first device light 111 may still be reflected at the optical filter 550, resulting in outcoupled first device light 111 having one or more of an undesired color point, an undesired color rendering index, and an undesired correlated color temperature. Hence, it may be desired to admix some additional light having intensity in the blue-green wavelength region into the first device light. Such additional blue-green light may be provided by the second device light (121) (especially by the first type of second device light 1211). Hence, the light generating system 1000 may be configured such that in the first operational mode of the light generating system 1000 the system light 1001 may be white light comprising at least part of the first device light 111 and at least part of the second device light 121 (wherein optionally the second device light 121 comprises intensity in the blue wavelength range).

[0090] Fig. 3B schematically depicts the spectral power distribution of the first device light 111, the first type of second device light 1211, the second type of second device light 1221, and the third type of second device light 1231. As indicated, the first device light 111 may especially be white light. Further, the first type of second device light 1211 may be blue light, the second type of second device light 1221 may be green light, and the third type of second device light 1231 may be red light. In embodiments, the control system 300 may be configured to change the relative intensities of one or more of the first device light 111, the first type of second device light 1211, the second type of second device light 1221, and the third type of second device light 1231, especially in a second operational mode. By increasing the relative intensity of one (or more) of the types of second device light 1211,1221,1231, the light generating system may thus especially be configured to generate colored system light 1001, wherein the colored system light 1001 may especially have a color selected from the RGB color space. Hence, the light generating system 1000 may be configured to generate in a second operational mode of the light generating system 1001 nonwhite system light 1001.

[0091] Fig. 4 schematically depicts an embodiment of a luminaire 2 comprising the light generating system 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the light generating system 1000. Fig. 4 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig. 4 schematically depicts embodiments of a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device, a photochemical reactor, an automotive lighting device, and an optical wireless communication device, comprising the light generating system 1000 as described herein. Lighting device light escaping from the lighting device 1200 is indicated with reference 1201. Lighting device light 1201 may essentially consist of system light 1001, and may in specific embodiments thus be system light 1001. Reference 1300 refers to a space, such as a room. Reference 1305 refers to a floor and reference 1310 to a ceiling; reference 1307 refers to a wall.

[0092] 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%.

[0093] 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".

[0094] 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.

[0095] 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.

[0096] 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.

[0097] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the operational modes as described herein. Yet further, the invention also provides a computer program product which, 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.

[0098] 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.

[0099] 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.

[0100] Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. A light generating system (1000) comprising one or more first light generating devices (110), one or more second light generating devices (120), and a light transmissive enclosure (500), wherein: the light transmissive enclosure (500) comprises a light transmissive material (505); wherein the light transmissive enclosure (500) defines an enclosure volume (507); wherein the light transmissive enclosure (500) further contains a thermally conductive gas (509), wherein the thermally conductive gas (509) comprises one or more of (i) He in a percentage of at least 10%, (ii) H2 in a percentage of at least 1%, and (iii) Ne in a percentage of at least 1%; the one or more first light generating devices (110) are configured in the enclosure volume (507); wherein the one or more first light generating devices (110) are configured to generate first device light (111) having intensity at one or more wavelengths in the visible wavelength range; wherein the one or more first light generating devices (110) comprise one or more first LED filaments (115); wherein the one or more first LED filaments (115) comprise first solid state light sources (10) and a first luminescent material (210), wherein the first solid state light sources (10) are configured to generate first solid state light source light (11), and wherein the first luminescent material (210) is configured to convert at least part of the first solid state light source light (11) into first luminescent material light (211); wherein the first device light (111) comprises at least part of the first luminescent material light (211); the one or more second light generating devices (120) are configured external from the enclosure volume (507); wherein the one or more second light generating devices (120) comprise one or more second LED filaments (125); wherein the one or more second light generating devices (120) are configured to generate second device light (121) having intensity at one or more wavelengths in the visible wavelength range; and the light generating system (1000) is (a) configured to generate system light (1001) comprising one or more of (i) at least part of the first device light (111), and (ii) at least part of the second device light (121), and (b) configured such that in a first operational mode of the light generating system (1000) the system light (1001) is white light;wherein the light generating system further comprises a second light transmissive enclosure (1500), wherein the second light transmissive enclosure (1500) comprises a second light transmissive material (1505); wherein the second light transmissive enclosure (1500) defines a second enclosure volume (1507); wherein the second light transmissive enclosure (1500) encloses at least part of the first enclosure (500); wherein the one or more second light generating devices (120) are at least partly configured in the second enclosure volume (1507); wherein the second light transmissive enclosure (1500) contains a second gas (508) in the second enclosure volume (1507); and wherein (i) the second gas (508) comprises air; (ii) the second gas (508) and the thermally conductive gas (509) have different gas compositions; (iii) the thermally conductive gas has a first pressure Pl in the enclosure volume, the second gas has a second pressure P2 in the second enclosure volume, the second pressure P2 is lower than the first pressure Pl; and / or (iv) the thermally conductive gas has a thermal conductivity higher than the second gas.

2. The light generating system (1000) according to claim 1, wherein:(i) the second gas (508) comprises air and / or (iii) the thermally conductive gas has a first pressure Pl in the enclosure volume, the second gas has a second pressure P2 in the second enclosure volume, the second pressure P2 is lower than the first pressure Pl.

3. The light generating system (1000) according to claim 1 or 2, wherein the thermally conductive gas (509) comprises He in a percentage of at least 60%.

4. The light generating system (1000) according to any one of the preceding claims, wherein the one or more first LED filaments (115) are configured to generate white first device light (111); and wherein the one or more first LED filaments (115) are configured to generate first device light (111) having a correlated color temperature selected from the range of 1500-6500 K.

5. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) comprises at least two different types of first LED filaments (115) configured to generate first device light (111) having correlated color temperatures differing at least 500 K.

6. The light generating system (1000) according to any one of the preceding claims 1-5, wherein at least one of the one or more second LED filaments (125) comprises second solid state light sources (20) and a second luminescent material (220), wherein the second solid state light sources (20) are configured to generate second solid state light source light (21), and wherein the second luminescent material (220) is configured to convert at least part of the second solid state light source light (21) into second luminescent material light (221); wherein the second device light (121) of the at least one of the one or more second LED filaments (125) comprises at least part of the second luminescent material light (211), and wherein this second device light (125) is colored light.

7. The light generating system (1000) according to any one of the preceding claims 1-5, wherein at least one of the one or more second LED filaments (125) comprises second solid state light sources (20), wherein the second solid state light sources (20) are configured to generate second solid state light source light (21); wherein the second device light (121) of the at least one of the one or more second LED filaments (125) comprises at least part of the second solid state light source light (21), and wherein this second device light (125) is colored light.

8. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) comprises a first type of second light generating devices (1210) configured to generate first type of second device light (1211) having a first centroid wavelength in the blue wavelength range.

9. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) comprises, a second type of second light generating devices (1220) configured to generate second type of second device light (1221) having a second centroid wavelength in the green wavelength range.

10. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) comprises a third type of second light generating devices (1230) configured to generate third type of second device light (1231) having a third centroid wavelength in the orange-red wavelength range.

11. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) is configured such that in the first operational mode of the light generating system (1000) the system light (1001) is white light comprising at least part of the first device light (111) and at least part of the second device light (121).

12. The light generating system (1000) according to any one of the preceding claims, further comprising a control system (300) configured to control a spectral power distribution of the system light (1001).

13. The light generating system (1000) according to any one of the preceding claims, further comprising an optical filter (550) at least partly configured between the one or more first light generating devices (110) and the one or more second light generating devices (120); wherein the one or more second light generating devices (120) and the optical filter (550) are configured such that at least part of the second device light (121) (i) is reflected at the optical filter (550) in a direction away from the one or more first light generating devices (110), and / or (ii) is absorbed by the optical filter (550).14 The light generating system (1000) according to claim 13, wherein the optical filter (550) is transmissive for at least part of the first device light (111) and reflective for at least part of the second device light (121).

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

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