A laser-phosphor based light generating system
The described light generating system enhances optical performance and brightness by optimizing light emission and polarization through a combination of solid-state light sources and optical elements, addressing issues in existing laser-phosphor systems.
Patent Information
- Application Number
- PCT/EP2025/068504
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-07-09
- Filing Date
- 2025-06-30
- Publication Date
- 2026-01-15
AI Technical Summary
Existing laser-phosphor based light generating systems face challenges in improving optical performance, brightness, and minimizing light losses.
A light generating system comprising a combination of solid-state light sources, dichroic mirrors, polarizing beam splitters, and polarization rotators to optimize the emission and polarization of light, including blue, green-yellow, and red light components, to enhance brightness and quality.
The system achieves improved brightness and quality of light output with reduced losses, enabling applications such as stage lighting and automotive lighting.
Smart Images
Figure EP2025068504_15012026_PF_FP_ABST
Abstract
Description
[0001] A laser-phosphor based light generating system
[0002] FIELD OF THE INVENTION
[0003] The invention relates to a light generating system configured to, in operation, emit system light. The invention further relates to a lamp or a luminaire comprising such a light generating system.
[0004] As used herein, the term “blue light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 420 nm to 490 nm, or the wavelength interval of 440 nm to 460 nm.
[0005] As used herein, the term “green light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 490 nm to 520 nm, or the wavelength interval of 500 nm to 520 nm.
[0006] As used herein, the term “yellow light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 520 nm to 590 nm.
[0007] As used herein, the term “short wavelength green light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 490 nm to 520 nm.
[0008] As used herein, the term “long wavelength green light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 520 nm to 550 nm.
[0009] As used herein, the term “red light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 620 to 660 nm.
[0010] The term “centroid wavelength”, also indicated as Xc, as used herein is known in the art, and refers to the wavelength value where half of the light energy of a given light beam is at shorter wavelengths and half the energy of the given light beam 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 Zc = X X*I(X) / (S I( X)), where the summation is over the wavelength range of interest, and I(X) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions.
[0011] As used herein, the terms “upstream” and “downstream” are intended to be understood relative to the direction of propagation of light through the light generation system. In other words, when a first component or feature is arranged “downstream” of a second component or feature, it may be understood that the first component or feature is arranged in a light receiving relationship with the second component or feature.
[0012] As used herein, the term “solid state light source” is intended to refer to any solid state light source, including diode lasers, super-luminescent diodes, and multi -junction diodes, comprising one or more LEDs, including one or more LEDs without any additional optics.
[0013] BACKGROUND OF THE INVENTION
[0014] Laser lighting is used in high-brightness lighting applications such as headlamps, projectors, and stage-lighting.
[0015] WO 2022 / 143318 Al discloses a light emitting device comprising a first light source emitting blue light, a second light source emitting blue light, a dichroic mirror, a wavelength conversion apparatus, a first light path adjusting apparatus or a second light path adjusting apparatus, and a first scattering optical system.
[0016] It is desired to improve the optical performance and / or functionality of laser- phosphor lighting. Especially, it is desired to improve the brightness and the quality of the light provided by laser-phosphor based light generating systems and to lower or minimize light losses in laser-phosphor based light generating systems.
[0017] SUMMARY OF THE INVENTION
[0018] It is an object of the present invention to overcome this problem, and to provide a laser-phosphor based light generating system with which the optical performance and / or functionality is improved.
[0019] It is a further object of the invention to provide a laser-phosphor based light generating system providing system light with an improved brightness and / or an improved quality, and to lower or minimize light losses in laser-phosphor based light generating systems.
[0020] According to a first aspect of the invention, this and other objects are achieved by means of a light generating system configured to, in operation, emit system light, the light generating system comprising a first solid-state light source configured to, in operation, emit first light source light having a peak emission wavelength, b I . in a wavelength range from 400 nm to 490 nm, the first solid-state light source being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a luminescent element being arranged downstream of the first solid-state light source and being configured to, at least partly, convert the first light source light into green-yellow converted light having a peak emission wavelength, Xg, in a wavelength range from 500 nm to 590 nm, the green-yellow converted light comprising short wavelength green-yellow converted light having a first centroid emission wavelength, Zcl . and long wavelength green-yellow converted light having a second centroid emission wavelength, Zc2. where Zc2 > Zcl . a first dichroic mirror being arranged downstream of the first solid-state light source, wherein (i) the first dichroic mirror is transparent for the first light source light and reflective for the long wavelength greenyellow converted light, or (ii) wherein the first dichroic mirror is reflective for the first light source light and transparent for the long wavelength green-yellow converted light, and wherein the first dichroic mirror is being arranged to direct the first light source light in a direction towards the luminescent element, a second dichroic mirror being arranged downstream of the luminescent element, wherein the second dichroic mirror is transparent for the long wavelength green-yellow converted light and reflective for the short wavelength green-yellow converted light, and wherein the second dichroic mirror is being arranged to direct the short wavelength green-yellow converted light in a direction towards the luminescent element, the luminescent element further being configured to receive the short wavelength green-yellow converted light reflected by the second dichroic mirror, and, at least partly, convert the short wavelength green-yellow converted light into long wavelength green-yellow converted light, a second solid-state light source configured to, in operation, emit second light source light having a first linear polarization, pbl, and having a peak emission wavelength, Xb2. in a wavelength range from 430 nm to 490 nm, the second solid- state light source being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a third solid-state light source configured to, in operation, emit short wavelength green light source light having a first linear polarization, pg’l, and having a peak emission wavelength, Xg’, in a wavelength range from 500 nm to 540 nm, the third solid-state light source being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a first polarizing beam splitter being arranged downstream of the second solid-state light source and of the third solid-state light source, the first polarizing beam splitter being transparent for the second light source light and the short wavelength green light source light, or being reflective for the second light source light and the short wavelength green light source light, a first diffusing element being arranged downstream of the first polarizing beam splitter, the first diffusing element being configured to diffuse the second light source light to provide diffuse blue light and to diffuse the short wavelength green light source light to provide diffuse short wavelength green light, and a first polarization rotator element being arranged between the first diffusing element and the first polarizing beam splitter, the first polarization rotator element being configured to rotate the polarization of the diffuse blue light such that the diffused blue light transmitted through the first polarization rotator element has a second linear polarization, pb2, different from the first linear polarization, pbl, to provide polarization rotated diffuse blue light and to rotate the polarization of the diffuse short wavelength green light such that the diffuse short wavelength green light transmitted through the first polarization rotator element has a second linear polarization, pg’2, different from the first linear polarization, pg’ 1, to provide polarization rotated diffuse short wavelength green light, the first polarizing beam splitter further being reflective for the polarization rotated diffuse blue light and the polarization rotated diffuse short wavelength green light, or being transparent for the polarization rotated diffuse blue light and the polarization rotated diffuse short wavelength green light, wherein in an operational mode of the light generating system the system light comprises the long wavelength green-yellow converted light, the polarization rotated diffuse blue light, and the polarization rotated diffuse short wavelength green light.
[0021] Thereby, a laser-phosphor based light generating system is provided with which system light with an improved brightness and / or an improved quality may be provided, and with which light losses in the laser-phosphor based light generating system may be lowered or minimized. This in turn provides for a laser-phosphor based light generating system with which the optical performance and / or functionality is improved.
[0022] The first polarizing beam splitter may be configured to combine the polarization rotated diffuse blue light, and the polarization rotated diffuse short wavelength green light to form the system light.
[0023] Thereby, a structurally simpler light generating system is provided for.
[0024] The second dichroic mirror may further be arranged upstream of the first dichroic mirror. When the second dichroic mirror is arranged between the first dichroic mirror and the first phosphor element, then the second dichroic mirror needs to be transparent for the first light source light.
[0025] The second dichroic mirror may also be arranged between the first dichroic mirror and the first polarizing beam splitter. In this case, the first dichroic element further needs to be reflective for the short wavelength green-yellow converted light. Furthermore, in this case, it is not needed that the second dichroic mirror is transparent for the first light source light. The second light source light may have a first linear polarization and a peak emission wavelength, b2. in a wavelength range from 440 nm to 465 nm, i.e., royal blue.
[0026] Thereby, a laser-phosphor based light generating system is provided with which system light with a further improved brightness and / or a further improved quality may be provided.
[0027] The short wavelength green light source light may have a first linear polarization and a peak emission wavelength, g’, in a wavelength range from 505 nm to 530 nm.
[0028] This wavelength interval is advantageous because lower wavelengths are easier to combine with the long wavelength green-yellow converted light.
[0029] The first polarizing beam splitter may for instance also be transparent for the long wavelength green-yellow converted light.
[0030] The reason is that the long wavelength green-yellow converted light can then also be combined with the second light source light and the short wavelength green light source light by another dichroic element.
[0031] The first polarization rotator element may for instance be a quarter wavelength plate.
[0032] Thereby, a structurally simple polarization rotator element is provided for. The first polarization rotator element may be configured to rotate the polarization of the diffuse blue light such that the diffused blue light transmitted through the first polarization rotator element has a second linear polarization, pb2, being rotated by 90 degrees with respect to the first linear polarization, pbl, and to rotate the polarization of the diffuse short wavelength green light such that the diffuse short wavelength green light laser light transmitted through the first polarization rotator element has a second linear polarization, pg’2, being rotated by 90 degrees with respect to the first linear polarization, pg’l.
[0033] Thereby, a structurally simpler light generating system is provided for.
[0034] The green light source light may have a peak emission wavelength in the range from 500 nm to 520 nm.
[0035] The first polarizing beam splitter may be configured to combine the polarization rotated diffuse blue light, the polarization rotated diffuse short wavelength green light, and the long wavelength green-yellow converted light.
[0036] Alternatively, the light generating system may further comprise a further light beam combining element, the further light beam combining element being configured to combine the polarization rotated diffuse blue light, the polarization rotated diffuse short wavelength green light, and the long wavelength green-yellow converted light.
[0037] In either case the system light is thus formed in a simple and straight forward manner. The first mentioned alternative is furthermore particularly structurally simple.
[0038] The light generating system may further comprise a third dichroic mirror being arranged downstream of the second solid-state light source and downstream of the third solid-state light source, wherein the third dichroic mirror is transparent for the second light source light and reflective for the short wavelength green light source light, or wherein the third dichroic mirror is reflective for the second light source light and transparent for the short wavelength green light source light, wherein the first polarizing beam splitter further is arranged downstream of the third dichroic mirror.
[0039] Thereby, the second solid state light source and the third solid state light source may be arranged spaced apart, which in turn lower the light losses in the light generation system even further.
[0040] The light generating system may further comprise a mirror, the mirror being arranged downstream of the third solid-state light source and configured to reflect the short wavelength green light source light towards the third dichroic mirror.
[0041] Thereby all three solid state light sources may be arranged in the same plane, or at least on the same side of the light generation system, which enables providing a more compact light generation system.
[0042] The light generating system may further comprise a fourth solid-state light source configured to, in operation, emit red light source light having a peak emission wavelength, Xr, in a wavelength range from 600 nm to 670 nm and a first linear polarization, prl, the fourth solid-state light source being selected from the group of diode lasers, super- luminescent diodes, and multi -junction diodes, a second polarizing beam splitter being arranged upstream of the first polarizing beam splitter and downstream of the fourth solid- state light source, the second polarizing beam splitter being transparent for the red light source light, a second diffusing element being arranged downstream of the second polarizing beam splitter, the second diffusing element being configured to diffuse the red light source light to provide diffuse red light, and a second polarization rotator element arranged downstream of the second diffusing element, the second polarization rotator element being configured to rotate the polarization of the diffuse red light such that the diffuse red light transmitted through the second polarization rotator element has a second linear polarization, pr2, different from the first linear polarization, prl, to provide polarization rotated diffuse red light, wherein in an operational mode of the light generating system the system light further comprises the polarization rotated diffuse red light.
[0043] By thus adding red light to the system light, a laser-phosphor based light generating system is provided with which system light with a further improved brightness and / or a further improved quality may be provided.
[0044] The red light source light may have a peak emission wavelength in a wavelength range from 630 to 660 nm.
[0045] Since efficient red solid-state light sources emit light in this particular range, the efficiency of the light generation system may thus be improved.
[0046] The second polarizing beam splitter may further be reflective for the polarization rotated diffuse red light, such that the polarizing beam splitter is configured to combine the polarization rotated diffuse blue light, the polarization rotated diffuse short wavelength green light, the long wavelength green-yellow converted light, and the polarization rotated diffuse red light.
[0047] Thereby, a structurally simpler light generating system is provided for.
[0048] The second polarization rotator element may be configured to rotate the polarization of the diffuse red light such that the diffuse red light transmitted through the second polarization rotator element has a second linear polarization, pr2, different from the first linear polarization, prl, by 90 degrees.
[0049] Thereby, a structurally simpler light generating system is provided for.
[0050] The second polarization rotator element may be a quarter wavelength plate. Thereby, a structurally simpler polarization rotator element is provided for. The second polarizing beam splitter may further be arranged upstream of the first dichroic mirror, and the first dichroic mirror may further be transparent for the polarization rotated diffuse red light. Alternatively, the second polarizing beam splitter may further be arranged downstream of the first dichroic mirror, and the second polarizing beam splitter may further be transparent for the long wavelength green-yellow converted light.
[0051] Thereby, a structurally simpler light generating system is provided for.
[0052] The system light may be white light having a color rendering index, CRI, of at least 65, and a correlated color temperature, CCT, of in a range from 2000 K to 8000 K.
[0053] The system light may have a color rendering index, CRI, of at least 70, at least 75, at least 80, or even at least 85. The system light may have a correlated color temperature, CCT, of in a range from 2500 K to 8000 K, or from 3000 K to 8000 K, or from 3900 K to 8000 K, or from 2000 K to 10000 K or from 3900 K to 10000 K.
[0054] The system light may have a correlated color temperature, CCT, of at least 2000 K and / or at most 10000 K.
[0055] Such system light comprises a particularly good brightness and / or a particularly high quality making it especially useful for such applications as for instance stage lighting, projection lighting and automotive lighting.
[0056] The light generating system may further comprise any one or more of (i) a first optical element arranged downstream of the first solid-state light source and configured to collimate the first light source light, (ii) a second optical element arranged downstream of the second solid-state light source and configured to collimate the second light source light, (iii) a third optical element arranged downstream of the third solid-state light source and configured to collimate the short wavelength green light source light, (iv) a fourth optical element arranged downstream of the luminescent element and upstream of the second dichroic mirror, the fourth optical element being configured to focus the first light source light on the first luminescent element and being configured to collimate at least the long wavelength green-yellow converted light of the green-yellow converted light, and (v) a fifth optical element arranged downstream of the first diffusing element and upstream of the first polarization rotator element, the fifth optical element being configured to focus the second light source light and the short wavelength green light source light on the first diffusing element and being configured to collimate the diffuse blue light and the diffuse short wavelength green light.
[0057] By collimating one or more of the first light source light, the second light source light, the short wavelength green light source light, the long wavelength green-yellow converted light and the diffuse blue light and the diffuse short wavelength green light, it is ensured that the resulting added light beam of system light comprises an improved homogeneity. By focusing the first light source light on the luminescent element, and by focusing the short wavelength green light source light on the first diffusing element, it is ensured that all of the respective light beam is impinging on the luminescent element and the first diffusing element, respectively, and thus becomes converted and diffused, respectively. Thereby light losses in the system are lowered.
[0058] The light generating system may further comprise any one or more of a sixth optical element arranged downstream of the fourth solid-state light source and configured to collimate the red light source light, and a seventh optical element arranged downstream of the second diffusing element and upstream of the second polarization rotator element, the seventh optical element being configured to focus the red light source light on the second diffusing element and being configured to collimate the diffuse red light.
[0059] By collimating one or more of the red light source light and the diffuse red light, it is ensured that the resulting added light beam of system light comprises an improved homogeneity.
[0060] Any one or more of the first optical element, the second optical element, the third optical element, the fourth optical element and the fifth optical element may be lenses.
[0061] Any one or more of the sixth optical element and the seventh optical element may be lenses.
[0062] Thereby, a structurally simple optical elements is provided for.
[0063] The second dichroic mirror may comprise a cut-off at a cut-off wavelength in a wavelength range of 510 to 530 nm, or 515 - 525 nm, or 518 - 522 nm, such as at 520 nm, for the short wavelength green-yellow converted light, and the long wavelength green-yellow converted light.
[0064] Thereby, it becomes possible to obtain a high transmission, e.g., of more than 80%, for the long wavelength green light and a high reflection, e.g., of more than 80%, for the short wavelength green light. The obtained effect is thus an improved efficiency.
[0065] One, two or more of the following may apply:
[0066] Xcl is in the range of 500 nm to 520 nm,
[0067] Xc2 is in the range of 530 nm to 570 nm, the short wavelength green light has a peak emission wavelength, Xg’, in the range of 500 nm to 520 nm, the first light source light has a peak emission wavelength, Zb I , in the range of 430 nm to 470 nm, the second light source light has a peak emission wavelength, Xb2, in the range of 440 nm to 465 nm, and the red light source light has a peak emission wavelength, Xr, in the range of 630 to 660 nm.
[0068] Providing the first light source light with a peak emission wavelength, Xbl, in the range of 430 nm to 470 nm as the effect of enabling using a relative low cost laser and providing the best excitation light. Providing the second light source light with a peak emission wavelength, Xb2. in the range of 440 nm to 465 nm has the advantage that the wavelength range corresponds to royal blue which provides the best blue light quality.
[0069] Providing the red light source light with a peak emission wavelength, Xr, in the range of 630 to 660 nm, has the advantage of enabling using the most efficient red solid-state light source.
[0070] The first dichroic mirror may be transparent for the red light source light with the peak emission wavelength, Xr.
[0071] The light generating system may further comprise a controller configured to individually control the first solid-state light source, the second solid-state light source, the third solid-state light source, and where provided the fourth solid-state light source.
[0072] Thereby, the controller may individually control the first light source light, the second light source light, the short wavelength green light source light, and where provided the red light source light. Thereby relevant parameters of the first light source light, the second light source light, the short wavelength green light source light, and the red light source light, respectively, may be controlled in a simple and straight forward manner to ensure the desired system light is provided. Relevant parameters may encompass a peak wavelength, a peak frequency, a (peak) color temperature, and a (peak) correlated color temperature.
[0073] The light generating system may further comprise one or more of a sensor device and a memory device configured to provide one or more of sensor input and memory input to the controller, and the controller may be configured to maintain one or more of the color point, the correlated color temperature, CCT, or the relative contributions of the first solid state light source, the second solid state light source, the third solid state light source, and where provided the fourth solid state light source, within a predefined range.
[0074] The predefined range may for instance be within 7 standard deviation color matching (SDCM) or within 300 K. Alternatively, or additionally, the predefined range may for instance be within a difference of 0.03 or 0.05 for the x and / or y coordinates of the color point.
[0075] Thereby, it may in a simple and straight forward manner be ensured that the desired system light is provided continuously over time and / or at all times.
[0076] The luminescent element may comprise a phosphor of the type A3B5O12: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. Such phosphors are stable and efficient phosphors and can be applied directly on top of solid state light sources with good lifetime.
[0077] The invention further relates to a lamp or a luminaire comprising a light generating system according to the invention.
[0078] The lamp or the luminaire may, thanks to the light generating system, provide system light with an improved brightness and / or an improved color quality.
[0079] The lamp or luminaire may be any type of lamp and luminaire, but particularly a vehicle light, a projection device, a search light, an automotive lighting device or a stage lighting device.
[0080] It is noted that the invention relates to all possible combinations of features recited in the claims.
[0081] BRIEF DESCRIPTION OF THE DRAWINGS
[0082] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.
[0083] Fig. 1 schematically shows a light generating system configured to, in operation, emit system light according to the present invention.
[0084] Fig. 2 schematically shows another light generating system configured to, in operation, emit system light according to the present invention.
[0085] Fig. 3 schematically shows another light generating system configured to, in operation, emit system light according to the present invention.
[0086] Fig. 4 schematically shows another light generating system configured to, in operation, emit system light according to the present invention.
[0087] Figs. 5A and 5B illustrate the result of a first simulation on a light generating system according to the invention, where Fig. 5A shows a color space diagram showing a line indicating the black body locus, BBL, and Fig. 5B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light.
[0088] Figs. 6A and 6B illustrate the result of a second simulation on a light generating system according to the invention, where Fig. 6A shows a color space diagram showing a line indicating the black body locus, BBL, and Fig. 6B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light.
[0089] Figs. 7 A and 7B illustrate the result of a third simulation on a light generating system according to the invention, where Fig. 7A shows a color space diagram showing a line indicating the black body locus, BBL, and Fig. 7B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light.
[0090] Figs. 8A and 8B illustrate the result of a fourth simulation on a light generating system according to the invention, where Fig. 8A shows a color space diagram showing a line indicating the black body locus, BBL, and Fig. 8B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light.
[0091] Figs. 9 A and 9B illustrate the result of a fifth simulation on a light generating system according to the invention, where Fig. 9A shows a color space diagram showing a line indicating the black body locus, BBL, and Fig. 9B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light.
[0092] Figs. 10A and 10B illustrate the result of a sixth simulation on a light generating system according to the invention, where Fig. 10A shows a color space diagram showing a line indicating the black body locus, BBL, and Fig. 10B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light.
[0093] Fig. 11 shows a graph of the intensity in arbitrary units as a function of the wavelength of emission and excitation, respectively, for a LuAG phosphor.
[0094] Figs. 12A-F schematically shows different exemplary lamps and luminaires which may comprise a light generating system according to the invention.
[0095] As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.
[0096] DETAILED DESCRIPTION
[0097] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.
[0098] Fig. 1 schematically shows a light generating system 1 according to the present invention. The light generating system 1 is configured to, in operation, emit system light 2. The system light 2 may be white light. The system light 2 may comprise a color rendering index, CRI, of between 65 and 85, and a correlated color temperature, CCT, of between 3900 K and 8000 K. The system light 2 may be white light. The system light 2 may comprise a color rendering index, CRI, of at least 65. Alternatively, the system light 2 may comprise a color rendering index, CRI, of at least 70, at least 75, at least 80, or even at least 85. The system light 2 may comprise a correlated color temperature, CCT, of in a range from 2000 K to 8000 K. Alternatively, the system light 2 may comprise a correlated color temperature, CCT, of in a range from 2500 K to 8000 K, or from 3000 K to 8000 K, or from 3900 K to 8000 K, or from 2000 K to 10000 K or from 3900 K to 10000 K. Alternatively, the system light 2 may comprise a correlated color temperature, CCT, of at least 2000 K and / or at most 10000 K.
[0099] Generally, and irrespective of the embodiment, the light generating system 1 comprises a first solid-state light source 3, a luminescent element 5, a first dichroic mirror 7, a second dichroic mirror 8, a second solid-state light source 9, a third solid-state light source 11, a first polarizing beam splitter 15, a first diffusing element 16, and a first polarization rotator element 19.
[0100] The first solid-state light source 3 is configured to, in operation, emit first light source light 4. The first light source light 4 has a peak emission wavelength, Xbl. The peak emission wavelength, Xbl, may be in the range of 440 nm to 460 nm, or 420 nm to 490 nm, or 400 nm to 490 nm. The first light source light 4 is blue light. The first solid-state light source 3 is selected from the group of diode lasers, super-luminescent diodes, and multijunction diodes.
[0101] The luminescent element 5 is arranged downstream of the first solid-state light source 3. The luminescent element 5 is configured to, at least partly, convert the first light source light 4 into green-yellow converted light 6. The green-yellow converted light 6 has a peak emission wavelength, Xg, where 500 nm < Xg < 590 nm. The green-yellow converted light 6 comprises short wavelength green-yellow converted light 61 and long wavelength green-yellow converted light 62. The short wavelength green-yellow converted light 61 has a first centroid emission wavelength, Xcl. The long wavelength green-yellow converted light 62 has a second centroid emission wavelength, Xc2. The second centroid emission wavelength Xc2 is larger than the first centroid emission wavelength Xcl. The first centroid emission wavelength, Xcl, of the short wavelength green-yellow converted light 61 may be the range of 490 nm to 520 nm, or 500 nm to 520 nm. The second centroid emission wavelength, Xc2, of the long wavelength green-yellow converted light 62 may be in the range of 520 nm to 550 nm, or 520 nm to 570 nm. The first dichroic mirror 7 is arranged downstream of the luminescent element 5. The first dichroic mirror 7 is transparent for the first blue light 4 and reflective for the long wavelength green-yellow converted light 62. Alternatively, the first dichroic mirror 7 is reflective for the first blue light 4 and transparent for the long wavelength green-yellow converted light 62.
[0102] The second dichroic mirror 8 is arranged downstream of the luminescent element 5 and upstream of the first dichroic mirror 7. The second dichroic mirror 8 is transparent for the long wavelength green-yellow converted light 62 and reflective for the short wavelength green-yellow converted light 61. The second dichroic mirror 8 may be or is also transparent for the first light source light 4. The luminescent element 5 is further configured to receive the short wavelength green-yellow converted light 61 reflected by the second dichroic mirror 8 and convert at least a part of the short wavelength green-yellow converted light 61 into long wavelength green-yellow converted light 62. The second dichroic mirror 8 comprises a cut-off. The cut-off may for instance be at a wavelength of 520 nm.
[0103] The second solid-state light source 9 is configured to, in operation, emit second light source light 10. The second light source light 10 has a first linear polarization, pbl. The second light source light 10 has a peak emission wavelength, kb2. The peak emission wavelength, kb2. may be in the range of 440 nm to 460 nm, or 420 nm to 490 nm. The second light source light 10 is blue light. The second solid-state light source 9 is selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes.
[0104] The third solid-state light source 11 is configured to, in operation, emit short wavelength green light source light 12. The short wavelength green light source light 12 has a first linear polarization, pg’ 1. The short wavelength green light source light 12 has a peak emission wavelength, kg’. The third peak emission wavelength, kg’, may be in the range of 520 nm to 550 nm, or 520 nm to 570 nm. The third solid-state light source 11 is selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes.
[0105] The first polarizing beam splitter 15 is arranged downstream of the second solid-state light source 9 and of the third solid-state light source 11. The first polarizing beam splitter 15 is transparent for the second light source light 10, and for the short wavelength green light source light 12. Alternatively, the first polarizing beam splitter 15 is reflective for the second light source light 10, and for the short wavelength green light source light 12.
[0106] The first diffusing element 16 is arranged downstream of the first polarizing beam splitter 15. The first diffusing element 16 is configured to diffuse the second light source light 10, thereby providing diffuse blue light 17. The first diffusing element 16 is further configured to diffuse the short wavelength green light source light 12, thereby providing diffuse short wavelength green light 18.
[0107] The first polarization rotator element 19 is arranged downstream of the first diffusing element 16. More particularly, the first polarization rotator element 19 is arranged in an optical path between the first diffusing element 16 and the first polarizing beam splitter 15. The first polarization rotator element 19 is configured to rotate the polarization of the diffuse blue light 17. The first polarization rotator element 19 is configured to provide the diffuse blue light 17 transmitted through the first polarization rotator element 19 with a second polarization, pb2, being different from the first polarization, pbl. Thereby polarization rotated diffuse blue light 20 is provided. The first polarization rotator element 19 may for instance be configured to rotate the polarization of the diffuse blue light 17 by 90 degrees. The first polarization rotator element 19 is further configured to rotate the polarization of the diffuse short wavelength green light 18. The first polarization rotator element 19 is configured to provide the diffuse short wavelength green light 18 with a second polarization, pg’2, being different from the first polarization, pg’l. Thereby polarization rotated diffuse short wavelength green light 21 is provided. The first polarization rotator element 19 may for instance be configured to rotate the polarization of the diffuse short wavelength green light 18 by 90 degrees. The first polarization rotator element 19 may for instance be a quarter wavelength plate. The first polarization rotator element 19 may be or is transparent for the second light source light 10 and for the short wavelength green light source light 12.
[0108] The first polarizing beam splitter 15 is furthermore reflective for the polarization rotated diffuse blue light 20 and reflective for the polarization rotated diffuse short wavelength green light 21. Alternatively, the first polarizing beam splitter 15 is furthermore transparent for the polarization rotated diffuse blue light 20 and transparent for the polarization rotated diffuse short wavelength green light 21.
[0109] Thus, in an operational mode of the light generating system 1, the system light 2 comprises the long wavelength green-yellow converted light 62, the polarization rotated diffuse blue light 20, and the polarization rotated diffuse short wavelength green light 21.
[0110] The first polarizing beam splitter 15 may further be configured to combine the long wavelength green-yellow converted light 62, the polarization rotated diffuse blue light 20, and the polarization rotated diffuse short wavelength green light 21 to form the system light 2. In an alternative, the light generating system 1 further comprises a further light beam combining element, such as a further dichroic mirror, the further light beam combining element being configured to combine the polarization rotated diffuse blue light 20, the polarization rotated diffuse short wavelength green light 21, and the long wavelength greenyellow converted light 62.
[0111] It is noted that as an alternative to a single polarizing beam splitter 15, diffusing element 16, and polarization rotator element 19, for both blue light and short wavelength green light, it is also possible to provide separate elements, that is a separate polarizing beam splitter 15, diffusing element 16, and polarization rotator element 19, for blue light and for short wavelength green light, respectively. For instance, the first polarizing beam splitter 15 may be a primary first polarizing beam splitter for the blue (i. e. , the first and / or second) light source light 4 and / or 10, and a secondary first polarizing beam splitter may be provided for the short wavelength green light 12. Likewise, the first diffusing element 16 may be a primary first diffusing element for the blue (i.e. , the first and / or second) light source light 4 and / or 10, and a secondary diffusing element may be provided for the short wavelength green light 12. Likewise, the polarization rotator element 19 may be a primary first polarization rotator element for the blue (i.e., the first and / or second) light source light 4 and / or 10, and a secondary polarization rotator element may be provided for the short wavelength green light 12.
[0112] As show in Fig. 1 the light generating system 1 may further comprise one or more of a number of optional optical elements. A first optical element 29 may be arranged downstream of the first solid-state light source 3. The first optical element 29 is configured to collimate the first light source light 4. A second optical element 30 may be arranged downstream of the second solid-state light source 9. The second optical element 30 is configured to collimate the second light source light 10. A third optical element 31 may be arranged downstream of the third solid-state light source 11. The third optical element 31 is configured to collimate the short wavelength green light source light 12. A fourth optical element 32 may be arranged downstream of the luminescent element 5 and upstream of the second dichroic mirror 8. The fourth optical element 32 is configured to focus the first light source light 4 on the first luminescent element 5. The fourth optical element 32 is further configured to collimate at least the long wavelength green-yellow converted light 62 of the green-yellow converted light 6. A fifth optical element 33 may be arranged downstream of the first diffusing element 16 and upstream of the first polarization rotator element 19. The fifth optical element 33 is configured to focus the second light source light 10 and the short wavelength green light source light 12 on the first diffusing element 16. The fifth optical element 33 is further configured to collimate the diffuse blue light 17 and the diffuse short wavelength green light 18. Any one or more of the first optical element 29, the second optical element 30, the third optical element 31, the fourth optical element 32 and the fifth optical element 33 may be collimating lenses.
[0113] As show in Fig. 1 the light generating system 1 may further comprise a controller 40. The controller 40 is an optional element. The controller 40 is configured to individually control the first solid-state light source 3, the second solid-state light source 9 and the third solid-state light source 11.
[0114] As show in Fig. 1 the light generating system 1 may further comprise one or more of a sensor device 50 and a memory device 60. The sensor device 50 and the memory device 60 are optional elements. The sensor device 50 and / or the memory device 60 are configured to compensate a drop-off in brightness of the polarization rotated diffuse blue light 20. The sensor device 50 and / or the memory device 60 are further configured to provide one or more of sensor input and memory input to the controller 40. Thereby, the controller 40 may be configured to maintain one or more of the color point, the correlated color temperature, CCT, or the relative contributions of the first solid-state light source 3, the second solid-state light source 9 and the third solid-state light source 11 within a predefined range. The predefined range may for instance be within seven standard deviation color matching (SDCM) or within 300 K. Alternatively, or additionally, the predefined range may for instance be within a difference of 0.03 or 0.05 for the x and / or y coordinates of the color point.
[0115] Fig. 2 shows a light generating system 100 according to the present invention. The light generating system 100 differs from the light generating system 1 shown in Fig. 1 and described above in virtue of the following features.
[0116] The light generating system 100 and further comprises a third dichroic mirror 14. The third dichroic mirror 14 is arranged downstream of the second solid-state light source 9 and downstream of the third solid-state light source 11. The third dichroic mirror 14 is transparent for the second light source light 10 and reflective for the short wavelength green light source light 12. Alternatively, the third dichroic mirror 14 is reflective for the second light source light 10 and transparent for the short wavelength green light source light 12. Also, the first polarizing beam splitter 15 of the light generating system 100 is arranged downstream of the third dichroic mirror 14. Fig. 3 shows a light generating system 101 according to the present invention. The light generating system 101 differs from the light generating system 100 shown in Fig. 2 and described above in virtue of the following features.
[0117] The light generating system 101 further comprises a mirror 13. The mirror 13 is arranged downstream of the third solid-state light source 11. The mirror 13 is configured to reflect the short wavelength green light source light 12 towards the third dichroic mirror 14.
[0118] Fig. 4 shows a light generating system 102 according to the present invention. The light generating system 102 differs from the light generating systems 1, 100 and 101 shown in Figs. 1-3 and described above in virtue of the following features.
[0119] The light generating system 102 further comprises a fourth solid-state light source 22, a second polarizing beam splitter 24, a second diffusing element 25, and a second polarization rotator element 27.
[0120] The fourth solid-state light source 22 is configured to, in operation, emit red light source light 23. The red light source light 23 comprises a first polarization, prl. The red light source light 23 has a peak emission wavelength, Xr. The peak emission wavelength, Xr, may be in the range of 620 to 660 nm, or 630 to 660 nm, or 620 nm to 670 nm, or 600 nm to 670 nm. The fourth solid-state light source 22 is selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes.
[0121] The second polarizing beam splitter 24 is arranged upstream of the first polarizing beam splitter 15 and downstream of the fourth solid-state light source 22. The second polarizing beam splitter 24 is transparent for the red light source light 23.
[0122] The second diffusing element 25 is arranged downstream of the second polarizing beam splitter 24. The second diffusing element 25 is configured to diffuse the red light source light 23, thereby providing diffuse red light 26.
[0123] The second polarization rotator element 27 is arranged downstream of the second diffusing element 25. The second polarization rotator element 27 is configured to rotate the polarization of the diffuse red light 26. Thereby, polarization rotated diffuse red light 28 is provided. The second polarization rotator element 27 is configured to provide the diffuse red light 26 transmitted through the second polarization rotator element 27 with a second polarization, pr2, being different from the first polarization, prl. Thereby, polarization rotated diffuse red light 28 is provided. The second polarization rotator element 27 may for instance be configured to rotate the polarization of the diffuse red light 26 by 90 degrees. The second polarization rotator element 27 may for instance be a quarter wavelength plate. The second polarizing beam splitter 24 may exhibit a dip in the wavelength range of the polarization rotated diffuse red light 28. The second polarization rotator element 27 may further be transparent for the diffuse the red light source light 23.
[0124] The second polarizing beam splitter 24 may further be arranged upstream of the first dichroic mirror 7 as shown in Fig. 4. The first dichroic mirror 7 is then transparent for the polarization rotated diffuse red light 28. Alternatively, the second polarizing beam splitter 24 may further be arranged downstream of the first dichroic mirror 7. Then, the second polarizing beam splitter 24 further is transparent for the long wavelength greenyellow converted light 62. The first dichroic mirror 7 may also be transparent for the red light source light 23.
[0125] In an operational mode of the light generating system 102, the system light 2 thus comprises the long wavelength green-yellow converted light 62, the polarization rotated diffuse blue light 20, the polarization rotated diffuse short wavelength green light 21, and the polarization rotated diffuse red light 28.
[0126] The polarizing beam splitter 15 may be configured to combine the short wavelength green-yellow converted light 61, the polarization rotated diffuse blue light 20, the polarization rotated diffuse long wavelength green light 21, and the polarization rotated diffuse red light 28.
[0127] In an alternative, the light generating system 102 further comprises a further light beam combining element, such as a further dichroic mirror, the further light beam combining element being configured to combine the polarization rotated diffuse blue light 20, the polarization rotated diffuse short wavelength green light 21, the long wavelength green-yellow converted light 62, and the polarization rotated diffuse red light 28.
[0128] As show in Fig. 4 the light generating system 102 may further comprise one or both of two optional optical elements. A sixth optical element 34 may be arranged downstream of the fourth solid-state light source 22. The sixth optical element 34 is configured to collimate the red light source light 23. A seventh optical element 35 may be arranged downstream of the second diffusing element 25 and upstream of the second polarization rotator element 27. The seventh optical element 33 is configured to focus the red light source light 23 on the second diffusing element 25. The seventh optical element 35 is further configured to collimate the diffuse red light 26. Any one or more of the sixth optical element 34 and the seventh optical element 35 may be collimating lenses.
[0129] The light generating system 102 may optionally further comprise a controller 40. The controller 40 is configured to individually control the first solid-state light source 3, the second solid-state light source 9, the third solid-state light source 11, and the fourth solid- state light source 22.
[0130] The light generating system 102 may further comprise one or more of a sensor device 50 and a memory device 60. The sensor device 50 and the memory device 60 are optional elements. The sensor device 50 and / or the memory device 60 are configured to compensate a drop-off in brightness of the polarization rotated diffuse blue light 20. The sensor device 50 and / or the memory device 60 are further configured to provide one or more of sensor input and memory input to the controller 40. Thereby, the controller 40 is configured to maintain one or more of the color point, the correlated color temperature, CCT, or the relative contributions of the first solid-state light source 3, the second solid-state light source 9, the third solid-state light source 11, and the fourth solid-state light source 22 within a predefined range. The predefined range may for instance be within 7 standard deviation color matching (SDCM) or within 300 K. Alternatively, or additionally, the predefined range may for instance be within a difference of 0.03 or 0.05 for the x and / or y coordinates of the color point.
[0131] It is noted that even though the light generating system 102 is very similar to the light generating system 101 of Fig. 3 and thus also comprises a first polarizing beam splitter 14 and a mirror 13, it is also feasible to provide the addition features of a fourth solid- state light source 22, a second polarizing beam splitter 24, a second diffusing element 25, and a second polarization rotator element 27 to any of the light generating systems 1 and 100 of Figs. 1 and 2.
[0132] Simulations
[0133] Referring now to Figs. 5A to 10B the results of a number of simulations performed on a light generating system 101 or 102 according to the present invention and as shown in Fig. 3 or Fig. 4 using different parameters is shown.
[0134] Figs. 5A and 5B illustrate the result of a first simulation on a light generating system 101 as shown in Fig. 3. Fig. 5 A shows a color space diagram showing a line indicating the black body locus, BBL, and illustrating the resulting system light 2. The system light 2 comprises a correlated color temperature, CCT, of 6297 K, a color rendering index, CRI, of 65 and a R9 value of -25. Fig. 5B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light 2. The blue component of the system light 2 comprises a peak wavelength of 450 nm and a peak intensity of about 20 W / nm2. The green component of the system light 2 comprises a peak wavelength of 520 nm and a peak intensity of about 4 W / nm2. The luminescent element 5 used was a YAG phosphor with 0.5 % Cerium (Ce).
[0135] Figs. 6 A and 6B illustrate the result of a second simulation on the light generating system 101. Fig. 6A shows a color space diagram showing a line indicating the black body locus, BBL, and illustrating the resulting system light 2. The system light 2 comprises a CCT of 7945 K, a CRI of 68 and a R9 value of -12. Fig. 6B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light 2. The blue component of the system light 2 comprises a peak wavelength of 450 nm and a peak intensity of about 25 W / nm2. The green component of the system light 2 comprises a peak wavelength of 520 nm and a peak intensity of about 6 W / nm2. The luminescent element 5 used was a YAG phosphor with 0.5 % Ce.
[0136] Figs. 7 A and 7B illustrate the result of a third simulation, this time performed on a light generating system 102 as shown in Fig. 4. Fig. 7A shows a color space diagram showing a line indicating the black body locus, BBL, and illustrating the resulting system light 2. The system light 2 comprises a CCT of 7122 K, a CRI of 81 and a R9 value of 14. Fig. 7B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light 2. The blue component of the system light 2 comprises a peak wavelength of 450 nm and a peak intensity of about 6 W / nm2. The green component of the system light 2 comprises a peak wavelength of 510 nm and a peak intensity of about 3 W / nm2. The red component of the system light 2 comprises a peak wavelength of 640 nm and a peak intensity of just over 3 W / nm2. The luminescent element 5 used was a LuAG phosphor with 3 % Ce.
[0137] Figs. 8A and 8B illustrate the result of a fourth simulation, again on a light generating system 102 as shown in Fig. 4. Fig. 8A shows a color space diagram showing a line indicating the black body locus, BBL, and illustrating the resulting system light 2. The system light 2 comprises a CCT of 5714 K, a CRI of 77 and a R9 value of -23. Fig. 8B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light 2. The blue component of the system light 2 comprises a peak wavelength of 450 nm and a peak intensity of about 10 W / nm2. The green component of the system light 2 comprises a peak wavelength of 510 nm and a peak intensity of about 6 W / nm2. The red component of the system light 2 comprises a peak wavelength of 640 nm and a peak intensity just above 10 W / nm2. The luminescent element 5 used was a LuAG phosphor with 3 % Ce. It is noted that the peak intensity of all three light components of the system light are in this case considerably higher than for the simulation shown in Figs. 7A and 7B. Figs. 9 A and 9B illustrate the result of a fifth simulation on a light generating system 102 as shown in Fig. 4. Fig. 9A shows a color space diagram showing a line indicating the black body locus, BBL, and illustrating the resulting system light 2. The system light 2 comprises a CCT of 3906 K, a CRI of 69 and a R9 value of -70. Fig. 9B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light 2. The blue component of the system light 2 comprises a peak wavelength of 450 nm and a peak intensity of about 6 W / nm2. The green component of the system light 2 comprises a peak wavelength of 510 nm and a peak intensity of about 6 W / nm2. The red component of the system light 2 comprises a peak wavelength of 640 nm and a peak intensity of about 16 W / nm2. The luminescent element 5 used was a LuAG phosphor with 3 % Ce.
[0138] Finally, Figs. 10A and 10B illustrate the result of a sixth simulation on a light generating system 102 as shown in Fig. 4. Fig. 10A shows a color space diagram showing a line indicating the black body locus, BBL, and illustrating the resulting system light 2. The system light 2 comprises a CCT of 5573 K, a CRI of 75 and a R9 value of 7. Fig. 10B shows a graph showing the intensity in W / nm2as a function of wavelength of the resulting system light 2. The blue component of the system light 2 comprises a peak wavelength of 450 nm and a peak intensity of about 10 W / nm2. The green component of the system light 2 comprises a peak wavelength of 520 nm and a peak intensity of about 5.5 W / nm2. The red component of the system light 2 comprises a peak wavelength of 640 nm and a peak intensity of about 8 W / nm2. The luminescent element 5 used was a LuAG phosphor with 3 % Ce.
[0139] Phosphors
[0140] Referring now to Fig. 11, different suitable phosphor elements for a light generating system 1, 100-111 according to the invention will be described.
[0141] Garnet class
[0142] Generally, garnet class phosphors are particularly suitable for use as the luminescent element 5. Garnet class phosphors are luminescent materials of the type A3B5O 12: Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. Embodiments of garnets especially include A3B5O12 garnets, wherein A comprises at least yttrium or lutetium and wherein B comprises at least aluminum. Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. Especially, B may comprise aluminum (Al); however, in addition to aluminum, B may also partly comprise gallium (Ga) and / or scandium (Sc) and / or indium (In), especially up to about 20% of B, more especially up to about 10 % of B (i.e. the B ions essentially consist of 90 or more mole % of Al and 10 or less mole % of one or more of Ga, Sc and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and / or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Yi-xLux)3B50i2:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Yi-xLux)3AlsOi2:Ce, part ofY and / or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Yo.iLuo.89Ceo.oi)3A150i2. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art.
[0143] (oxy)nitride class
[0144] This class comprises phosphors of the type M2Si5N8:Eu2+ , or MAlSiN3:Eu2+ or Ca2AlSi3O2N5:Eu2+, etc., wherein M comprises one or more of Ba, Sr, and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu.
[0145] Narrow-band redMn activated class
[0146] This class comprises phosphors of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetraval ent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine. Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Fig. 11 shows a graph of the intensity in arbitrary units as a function of the wavelength of emission (solid line) and excitation (dashed line), respectively, for one suitable garnet class phosphor, namely a Lutetium Aluminum Garnet (LuAG) phosphor. LuAG phosphors offer performance comparable to YAG phosphor elements. LuAG phosphors may have dominant emission wavelengths ranging from 520nm to 540 nm. LuAG phosphors are generally used in conjunction with red phosphor elements for high CRI full spectrum coverage. LuAG phosphors can be effectively excited by a 450nm blue LED with an emission peak wavelength in the 510-540 nm range. Combined with a nitride red phosphor, a high CRI spectrum with Ra above 95 can be achieved. LuAG phosphors are particularly suitable for use as the luminescent element 5.
[0147] Turning finally to Fig. 12, an exemplary lamp (Fig. 12A) and different exemplary luminaires (Figs. 12B-12F) comprising a light generating system 1, 100-106 according to the invention is shown schematically. Fig. 12A shows a lamp 201. Fig. 11B shows a luminaire 202. Fig. 12C shows a vehicle with a vehicle light 203. Fig. 12D shows a projection device 204. Fig. 12E shows a search light 205. Fig. 12F shows a stage lighting luminaire or fixture 206. In any event, the lamp 201 or the luminaire 202-206 may, thanks to the light generating system 1, 100-106, provide system light with an improved brightness and / or an improved color quality.
[0148] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.
[0149] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.
Claims
CLAIMS:
1. A light generating system (1; 100) configured to, in operation, emit system light (2), the light generating system comprising: a first solid-state light source (3) configured to, in operation, emit first light source light (4) having a peak emission wavelength, b I . in a wavelength range from 400 nm to 490 nm, the first solid-state light source (3) being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a luminescent element (5) being arranged downstream of the first solid-state light source and being configured to, at least partly, convert the first light source light (4) into green-yellow converted light (6) having a peak emission wavelength, g, in a wavelength range from 500 nm to 590 nm, the green-yellow converted light comprising short wavelength green-yellow converted light (61) having a first centroid emission wavelength, Zc I . and long wavelength green-yellow converted light (62) having a second centroid emission wavelength, Zc2. where Zc2 > Zcl . a first dichroic mirror (7) being arranged downstream of the first solid-state light source (3), wherein (i) the first dichroic mirror (7) is transparent for the first light source light (4) and reflective for the long wavelength green-yellow converted light (62), or (ii) wherein the first dichroic mirror (7) is reflective for the first light source light (4) and transparent for the long wavelength green-yellow converted light (62), and wherein the first dichroic mirror is being arranged to direct the first light source light in a direction towards the luminescent element, a second dichroic mirror (8) being arranged downstream of the luminescent element (5), wherein the second dichroic mirror (8) is transparent for the long wavelength green-yellow converted light (62) and reflective for the short wavelength green-yellow converted light (61), and wherein the second dichroic mirror is being arranged to direct the short wavelength green-yellow converted light (61) in a direction towards the luminescent element (5), the luminescent element (5) further being configured to receive the short wavelength green-yellow converted light (61) reflected by the second dichroic mirror (8),and, at least partly, convert the short wavelength green-yellow converted light (61) into long wavelength green-yellow converted light (62), a second solid-state light source (9) configured to, in operation, emit second light source light (10) having a first linear polarization, pbl, and having a peak emission wavelength, b2. in a wavelength range from 430 nm to 490 nm, the second solid-state light source (9) being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a third solid-state light source (11) configured to, in operation, emit short wavelength green light source light (12) having a first linear polarization, pg’ 1, and having a peak emission wavelength, g’, in a wavelength range from 500 nm to 540 nm, the third solid-state light source (11) being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a first polarizing beam splitter (15) being arranged downstream of the second solid-state light source (9) and of the third solid-state light source (11), the first polarizing beam splitter (15) being transparent for the second light source light (10) and the short wavelength green light source light (12), or being reflective for the second light source light (10) and the short wavelength green light source light (12), a first diffusing element (16) being arranged downstream of the first polarizing beam splitter (15), the first diffusing element (16) being configured to diffuse the second light source light (10) to provide diffuse blue light (17) and to diffuse the short wavelength green light source light (12) to provide diffuse short wavelength green light (18), and a first polarization rotator element (19) being arranged between the first diffusing element (16) and the first polarizing beam splitter (15), the first polarization rotator element (19) being configured to rotate the polarization of the diffuse blue light (17) such that the diffused blue light (17) transmitted through the first polarization rotator element (19) has a second linear polarization, pb2, different from the first linear polarization, pbl, to provide polarization rotated diffuse blue light (20) and to rotate the polarization of the diffuse short wavelength green light (18) such that the diffuse short wavelength green light (18) transmitted through the first polarization rotator element (19) has a second linear polarization, pg’2, different from the first linear polarization, pg’ 1, to provide polarization rotated diffuse short wavelength green light (21), the first polarizing beam splitter (15) further being reflective for the polarization rotated diffuse blue light (20) and the polarization rotated diffuse shortwavelength green light (21), or being transparent for the polarization rotated diffuse blue light (20) and the polarization rotated diffuse short wavelength green light (21), wherein in an operational mode of the light generating system the system light (2) comprises the long wavelength green-yellow converted light, the polarization rotated diffuse blue light (20), and the polarization rotated diffuse short wavelength green light (21).
2. A light generating system according to claim 1, wherein the first polarizing beam splitter (15) is configured to combine the polarization rotated diffuse blue light (20), the polarization rotated diffuse short wavelength green light (21), and the long wavelength green-yellow converted light (62), or wherein the light generating system further comprises a further light beam combining element, the further light beam combining element being configured to combine the polarization rotated diffuse blue light (20), the polarization rotated diffuse short wavelength green light (21), and the long wavelength green-yellow converted light (62).
3. A light generating system according to claim 1 or 2, and further comprising: a third dichroic mirror (14) being arranged downstream of the second solid- state light source (9) and downstream of the third solid-state light source (11), wherein the third dichroic mirror (14) is transparent for the second light source light (10) and reflective for the short wavelength green light source light (12), or wherein the third dichroic mirror (14) is reflective for the second light source light (10) and transparent for the short wavelength green light source light (12), wherein the first polarizing beam splitter (15) further is arranged downstream of the third dichroic mirror (14).
4. A light generating system according to any one of the above claims, and further comprising: a fourth solid-state light source (22) configured to, in operation, emit red light source light (23) having a first linear polarization, prl, and a peak emission wavelength, Xr, in a wavelength range from 600 nm to 670 nm, the fourth solid-state light source (22) being selected from the group of diode lasers, super-luminescent diodes, and multi -junction diodes, a second polarizing beam splitter (24) being arranged upstream of the first polarizing beam splitter (15) and downstream of the fourth solid-state light source (22), the second polarizing beam splitter (24) being transparent for the red light source light (23),a second diffusing element (25) being arranged downstream of the second polarizing beam splitter (24), the second diffusing element (25) being configured to diffuse the red light source light (23) to provide diffuse red light (26), and a second polarization rotator element (27) arranged downstream of the second diffusing element (25), the second polarization rotator element (27) being configured to rotate the polarization of the diffuse red light (26) such that the diffuse red light (26) transmitted through the second polarization rotator element (25) has a second linear polarization, pr2, different from the first linear polarization, prl, to provide polarization rotated diffuse red light (28), wherein in an operational mode of the light generating system the system light (2) further comprises the polarization rotated diffuse red light (28).
5. A light generating system according to claim 4, wherein the second polarizing beam splitter (24) further is arranged upstream of the first dichroic mirror (7), and wherein the first dichroic mirror (7) further is transparent for the polarization rotated diffuse red light (28), or wherein the second polarizing beam splitter (24) further is arranged downstream of the first dichroic mirror (7), and wherein the second polarizing beam splitter (24) further is transparent for the long wavelength green-yellow converted light (62).
6. A light generating system according to any one of the above claims, wherein the system light (2) is white light having a color rendering index, CRI, of at least 65, and a correlated color temperature, CCT, of in a range from 2000 K to 8000 K.
7. A light generating system according to any one of the above claims, and further comprising: a first optical element (29) arranged downstream of the first solid-state light source (3) and configured to collimate the first light source light (4), a second optical element (30) arranged downstream of the second solid-state light source (9) and configured to collimate the second light source light (10), a third optical element (31) arranged downstream of the third solid-state light source (11) and configured to collimate the short wavelength green light source light (12), a fourth optical element (32) arranged downstream of the luminescent element (5) and upstream of the second dichroic mirror (8), configured to focus the first light sourcelight (4) on the first luminescent element (5) and configured to collimate at least the long wavelength green-yellow converted light (62) of the green-yellow converted light (6), and a fifth optical element (33) arranged downstream of the first diffusing element (16) and upstream of the first polarization rotator element (19), configured to focus the second light source light (10) and the short wavelength green light source light (12) on the first diffusing element (16) and configured to collimate the diffuse blue light (17) and the diffuse short wavelength green light (18).
8. A light generating system according to any one of the above claims 4 to 7, and further comprising: a sixth optical element (34) arranged downstream of the fourth solid-state light source (22) and configured to collimate the red light source light (23), and a seventh optical element (35) arranged downstream of the second diffusing element (25) and upstream of the second polarization rotator element (27), the seventh optical element (33) being is configured to focus the red light source light (23) on the second diffusing element (25) and being configured to collimate the diffuse red light (26).
9. A light generating system according to any one of the above claims, wherein the second dichroic mirror (8) comprises a cut-off at a cut-off wavelength in a wavelength range of 510 to 530 nm for the short wavelength green-yellow converted light (61) and the long wavelength green-yellow converted light (62).
10. A light generating system according to any one of the above claims, wherein two or more of the following applies:Xcl is in the range of 500 nm to 520 nm,Xc2 is in the range of 530 nm to 570 nm, the short wavelength green light (12) has a peak emission wavelength, Xg’, in the range of 500 nm to 520 nm, the first light source light (4) has a peak emission wavelength, Zb I . in the range of 430 nm to 470 nm, the second light source light (10) has a peak emission wavelength, Xb2, in the range of 440 nm to 465 nm, and the red light source light (23) has a peak emission wavelength, Xr, in the range of 630 to 660 nm.
11. A light generating system according to any one of the above claims 4 to 10, wherein the first dichroic mirror (7) is transparent for the red light source light (23) with the peak emission wavelength, Xr.
12. A light generating system according to any one of the above claims, wherein the light generating system further comprises a controller (40) configured to individually control the first solid-state light source (3), the second solid-state light source (9), the third solid-state light source (11), and where provided the fourth solid-state light source (22).
13. A light generating system according to claim 12, wherein the light generating system further comprises one or more of a sensor device (50) and a memory device (60) configured to provide one or more of sensor input and memory input to the controller (40), and wherein the controller (40) is configured to maintain one or more of the color point, the correlated color temperature, CCT, or the relative contributions of the first solid-state light source (3), the second solid-state light source (9), the third solid-state light source (11), and where provided the fourth solid-state light source (22), within a predefined range.
14. A light generating system according to any one of the above claims, wherein the luminescent element (5) comprises a phosphor of the type AsBsOn 'e. wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc.
15. A lamp, a luminaire, a vehicle light, projection device, a search light, or a stage lighting device comprising a light generating system (1) according to any one of the above claims.