A light generating system

Abstract

A light generating system (1) configured to provide, in operation, system light and comprising a first laser bank (2) providing, in operation, first laser light (4), a phosphor wheel (8) with an illumination track (81, 82), comprising a light converting part (81) configured to convert at least a part of the first laser light (4) into converted light (13) having a Lambertian distribution, and a specular reflective part (82) configured to specularly reflect at least a part of the first laser light (4) into specularly reflected laser light (14), a first optical arrangement (9) configured (i) to off-axis focus the first laser light (4) onto the phosphor wheel, (ii) to collimate the converted light (13), and (iii) to off-axis collimate the specularly reflected laser light (14), a dichroic unit (10) configured to reflect the first laser light (4) towards the phosphor wheel (8) and (ii) to transmit the converted light (13) towards a beam splitting unit (11) and (iii) to transmit the specularly reflected laser light (14) towards the beam splitting unit (11) or to allow the specularly reflected laser light (14) to pass by towards the beam splitting unit (11), the beam splitting unit (11) being configured to split the specularly reflected laser light (14) and the converted light (13) such that the specularly reflected laser light (14) is transmitted through a quarter wave, ¼λ, plate (18) and focused onto a polarization maintaining reflective diffuser arrangement (15) being configured to diffuse the specularly reflected laser light (14) into diffused laser light (19), and a second optical arrangement (12) configured to combine the diffused laser light (19) and the converted light (13) into an added light beam (20) of system light.

Description

[0001] A light generating system

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a light generating system comprising a first laser bank providing first laser light and a phosphor wheel. The invention further relates to a light generating system further comprising a second laser bank providing second laser light and a laser light combiner arranged and configured to combine the first laser light and the second laser light into combined laser light. The invention still further relates to a lighting fixture 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.

[0005] As used herein, the term “green-yellow light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 500 nm to 585 nm.

[0006] As used herein, the term “green light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 500 nm to 550 nm.

[0007] As used herein, the term “yellow light” is intended to refer to light with a peak wavelength falling within the wavelength interval of 550 nm to 585 nm.

[0008] BACKGROUND OF THE INVENTION

[0009] Laser-phosphor technology uses a laser to pump a remote phosphor to obtain high brightness white light. A recent insight is that laser-phosphor products will be based on laser-banks instead of individual laser diodes.

[0010] For example, WO 2022 / 143318 Al discloses a light emitting device comprising a first light source, a second light source, 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. The first light source and the second light source are laser banks. A laser capable of emitting light of different dominant wavelengths can be used in the second light source to improve the color rendering index of the emergent light of the light emitting device. Light emitted by the first light source is all used for exciting the wavelength conversion apparatus. If a polarization selection element is used in the first light source in a matching mode, the output of light flux of the light emitting device can be further improved.

[0011] It is desired to provide a light generating system comprising a first laser bank providing first laser light, which light generating system provides high brightness white light, which exhibits an increased efficiency, and with which light loss in the system is minimized.

[0012] SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to overcome this problem, and to provide a light generating system providing high brightness white light, which exhibits an increased efficiency, and with which light loss in the system is minimized.

[0014] According to a first aspect of the invention, this and other objects are achieved by means of a light generating system configured to provide, in operation, system light, the light generating system comprising a first laser bank providing, in operation, first laser light, a phosphor wheel comprising an illumination track, the illumination track comprising a light converting part configured to convert at least a part of a laser light into converted light having a Lambertian distribution, and a specular reflective part configured to specularly reflect at least a part of the laser light, into specularly reflected laser light, the light converting part and the specular reflective part being sequentially arranged such that during rotation of the phosphor wheel the light converting part and the specular reflecting part are sequentially in time radiated with the first laser light, a first optical arrangement configured (i) to off-axis focus the laser light onto the phosphor wheel, (ii) to collimate the converted light, and (iii) to off-axis collimate the specularly reflected laser light, a dichroic unit configured to reflect the laser light towards the phosphor wheel and (ii) to transmit the converted light towards a beam splitting unit and (iii) to transmit the specularly reflected laser light towards the beam splitting unit or to allow the specularly reflected laser light to pass by towards the beam splitting unit, or to transmit the laser light towards the phosphor wheel and (ii) to reflect the converted light towards the beam splitting unit and (iii) to reflect the specularly reflected laser light towards the beam splitting unit, the laser light being the first laser light, the beam splitting unit being configured to split the specularly reflected laser light and the converted light such that the specularly reflected laser light is transmitted through a quarter wave, NX, plate and focused onto a (polarization maintaining) reflective diffuser arrangement, the (polarization maintaining) reflective diffuser arrangement being configured to diffuse the specularly reflected laser light into diffused laser light, and a second optical arrangement configured to combine the diffused laser light and the converted light into an added light beam of system light.

[0015] Thereby, and especially by providing that the light generating system enables off-axis focusing laser light from a laser bank onto a phosphor wheel which is partially specularly reflective and that enable subsequently reflected blue-laser and yellow-phosphor light to be separated such that blue-laser light is diffused by a reflective diffuser and next combined with the yellow-phosphor light to obtain white light, a light generating system providing high brightness white light, which exhibits an increased efficiency, and with which light loss in the system is minimized is provided for.

[0016] The light generating system may further comprise a second laser bank providing, in operation, second laser light, and a laser light combiner configured to combine the first laser light and the second laser light into combined laser light, where the laser light combiner is a dichroic mirror, where the first laser light is blue light having a first peak emission wavelength and a first polarization, Pl, where the second laser light is blue light having a second peak emission wavelength and a second polarization, P2, where the first peak emission wavelength is different from the second peak emission wavelength, where the first polarization is the same as the second polarization, and where the laser light is the converted laser light.

[0017] In other words, the objects of the invention are also achieved by means of a light generating system configured to provide, in operation, system light, the light generating system comprising a first laser bank providing, in operation, first laser light, a second laser bank providing, in operation, second laser light, and a laser light combiner configured to combine the first laser light and the second laser light into combined laser light, where the laser light combiner is a dichroic mirror, where the first laser light is blue light having a first peak emission wavelength and a first polarization, Pl, where the second laser light is blue light having a second peak emission wavelength and a second polarization, P2, where the first peak emission wavelength is different from the second peak emission wavelength, where the first polarization is the same as the second polarization, a phosphor wheel comprising an illumination track, the illumination track comprising a light converting part configured to convert at least a part of a laser light into converted light having a Lambertian distribution, and a specular reflective part configured to specularly reflect at least a part of the laser light, into specularly reflected laser light, the light converting part and the specular reflective part being sequentially arranged such that during rotation of the phosphor wheel the light converting part and the specular reflecting part are sequentially in time radiated with the first laser light, a first optical arrangement configured (i) to off-axis focus the laser light onto the phosphor wheel, (ii) to collimate the converted light, and (iii) to off-axis collimate the specularly reflected laser light, a dichroic unit configured to reflect the laser light towards the phosphor wheel and (ii) to transmit the converted light towards a beam splitting unit and (iii) to transmit the specularly reflected laser light towards the beam splitting unit or to allow the specularly reflected laser light to pass by towards the beam splitting unit, or to transmit the laser light towards the phosphor wheel and (ii) to reflect the converted light towards the beam splitting unit and (iii) to reflect the specularly reflected laser light towards the beam splitting unit, the laser light being the converted laser light, the beam splitting unit being configured to split the specularly reflected laser light and the converted light such that the specularly reflected laser light is transmitted through a quarter wave, 1 , plate and focused onto a polarization maintaining reflective diffuser arrangement, the polarization maintaining reflective diffuser arrangement being configured to diffuse the specularly reflected laser light into diffused laser light, and a second optical arrangement configured to combine the diffused laser light and the converted light into an added light beam of system light.

[0018] In addition to the above advantages, by providing a combined light beam which comprises a first or a second polarization different from each other, the eye safety will be increased, by making the blue laser light eye safe. Furthermore, laser light from two laser banks is combined and used to generate the eventually resulting white light of the light generating system. This in turn provides for white light with a higher intensity and / or brightness while still maintaining the above-mentioned advantages.

[0019] A difference between the first peak emission wavelength (XI) and the second peak emission wavelength (X2) may be equal to or larger than 10 nm, especially equal to or larger than 20 nm, such as equal to or larger than 30 nm.

[0020] The dichroic unit may comprise a dichroic mirror, where, during operation of the light generating system, the specularly reflected laser light is passing by the dichroic mirror, and where the converted light is partly passing by the dichroic mirror and partly transmitted through the dichroic mirror.

[0021] Dichroic mirrors have the advantage of reflecting unwanted light instead of absorbing the energy. Thus, a light generating system which is more robust, and which comprises a dichroic unit particularly suitable for the high energy laser light is provided for.

[0022] The dichroic unit may comprise a dichroic mirror and a specular mirror, where the dichroic mirror is configured to reflect the converted light and to transmit the first laser light or the specularly reflected laser light, and wherein the specular mirror is arranged in such a way with respect to the dichroic mirror that the specularly reflected laser light is reflected by the specular mirror and redirected towards the beam splitting unit.

[0023] Specular mirrors have the advantage of ensuring that rays reflect as a group at the same angle, and therefore enable a particularly precise redirection of the light with very low losses. Thus, a light generating system which is both more robust, and which comprises a dichroic unit particularly suitable for the high energy laser light and with which very low light losses are generated is provided for.

[0024] The specular mirror comprises a first center point, Cl, the dichroic mirror comprises a second center point, C2, and the specular mirror and the dichroic mirror may be arranged such that the second center point is offset from the first center point in such a way that the laser light is passing by the specular mirror.

[0025] Thereby, the light generating system is provided with a dichroic unit of a structurally particularly simple construction, while still achieving the desired redirection of light with a high degree of efficiency.

[0026] The first optical arrangement may be a lens or a lens array.

[0027] Thereby, a structurally particularly simple first optical array is provided for.

[0028] The polarization maintaining reflective diffuser arrangement may comprise a polarization maintaining diffuser, a third optical arrangement configured to focus the specularly reflected laser light onto the polarization maintaining diffuser, and the quarter wave plate which is configured to alter the polarization of specularly reflected laser light before being focused by the third optical arrangement.

[0029] The third optical arrangement may be a lens or a lens array.

[0030] Thereby, a structurally particularly simple third optical array is provided for.

[0031] Such an arrangement ensures that when the resulting light is eventually combined by the second optical arrangement, the resulting added light beam of system light is particularly homogeneous.

[0032] The third optical arrangement may be configured to collimate the diffuse laser light.

[0033] Thereby, the resulting added light beam of system light comprises a further improved homogeneity.

[0034] The second optical arrangement may comprise a further beam combiner configured and arranged to combine the diffuse laser light and the converted light into the added light beam.

[0035] Thereby, the added light beam is generated in a particularly simple manner. The second optical arrangement may be arranged downstream of the beam splitting unit. Alternatively, the second optical arrangement may be arranged at the beam splitting unit.

[0036] The second optical arrangement may comprise (i) a further beam combiner being configured and arranged to combine the diffused laser light and the converted light into an added light beam, (ii) a further beam splitting unit being configured to reflect the diffuse laser light and transmit the specularly reflected laser light, and (iii) a mirror configured to reflect the diffuse laser light reflected by the further beam splitting unit towards the further beam combiner.

[0037] Thereby, the final combination of the diffused laser light and the converted light into an added light beam of system light may be performed with an improved efficiency.

[0038] The beam splitting unit may be a dichroic mirror.

[0039] The further beam splitting unit may be a dichroic mirror.

[0040] Dichroic mirrors have the advantage of reflecting unwanted light instead of absorbing the energy. Thus, a light generating system which is more robust, and which comprises a dichroic unit particularly suitable for the high energy laser light is provided for.

[0041] The mirror may be a specular reflective mirror.

[0042] The specular reflective mirror may comprise a reflectivity of at least 80%, or at least 90%. In case of a specular reflective mirror optimized for a narrow wavelength bandwidth, such as of a blue laser, the specular reflective mirror may even comprise a reflectivity of at least 98%.

[0043] Specular reflective mirrors have the advantage of ensuring that rays reflect as a group at the same angle, and therefore enable a particularly precise redirection of the light with very low losses.

[0044] The light generating system may further comprise a flat polarization converter arranged downstream of the beam splitting unit to receive the specularly reflected laser light, the flat polarization converter being configured to convert the polarization of the specularly reflected laser light to generate polarization converted light, and a mirror configured to reflect the polarization converted light towards a polarizing beam splitting unit, where the polarization maintaining reflective diffuser arrangement comprises a polarization maintaining diffuser, and where the polarizing beam splitting unit is configured to reflect the polarization converted light towards the polarization maintaining reflective diffuser arrangement and to transmit the diffused light towards the second optical arrangement. Thereby, the final combination of the diffused laser light and the converted light into an added light beam of system light may be performed with an improved efficiency and lowered loss of light.

[0045] The light generating system may further comprise a controller configured to individually control the first laser bank and thus the first laser light. Where a second laser bank is provided, the controller may further be configured to control the second laser bank, and thus the second laser light, individually from or together with the first laser bank.

[0046] Thereby relevant parameters of the first laser light and of the second laser light 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.

[0047] The first laser light or the combined laser light may be blue light, the converted light may be green-yellow light, and the system light may be white light having a correlated color temperature in a range from 2000 K to 10000K, preferably in a range of 5000K to 9000K and a CRI of at least 70, preferably a CRI of at least 80.

[0048] The specular mirror comprises a first width, Wl, the dichroic mirror comprises a second width, W2, and the second width may be larger than the first width, i.e., W2 > Wl.

[0049] Thereby, the respective center points may be arranged offset with respect to one another while not influencing the size of the light generating system adversely, that is keeping the light generating system compact.

[0050] The invention further relates to a lighting fixture comprising a light generating system according to the invention.

[0051] It is noted that the invention relates to all possible combinations of features recited in the claims.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] 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.

[0054] Fig. 1 schematically shows an embodiment of a light generating system according to the invention.

[0055] Fig. 2 schematically shows another embodiment of a light generating system according to the invention.

[0056] Fig. 3 schematically shows another embodiment of a light generating system according to the invention. Fig. 4 schematically shows another embodiment of a light generating system according to the invention.

[0057] Fig. 5 schematically shows another embodiment of a light generating system according to the invention.

[0058] Fig. 6 schematically shows another embodiment of a light generating system according to the invention.

[0059] Figs. 7 A and 7B schematically illustrates light incident on and emitted from a specular reflective part of a phosphor wheel of a light generating system according to the invention, respectively, illustrating the light being off-axis focused and off-axis collimated, respectively.

[0060] Figs. 8 A and 8B schematically illustrates light incident on and emitted from a light converting part of a phosphor wheel of a light generating system according to the invention, respectively, illustrating the light being off-axis focused and collimated, respectively.

[0061] Figs. 9 A and 9B schematically illustrates light incident on and emitted from a specular reflective part of a phosphor wheel of a light generating system according to any one of Figs. 3 and 6.

[0062] Figs. 10A and 10B schematically illustrates light incident on and emitted from a light converting part of a phosphor wheel of a light generating system according to any one of Figs. 3 and 6.

[0063] Figs. 11 A and 1 IB schematically illustrates light incident on and emitted from a specular reflective part of a phosphor wheel of a light generating system according to any one of Figs. 1, 2, 4 and 5.

[0064] Figs. 12A and 12B schematically illustrates light incident on and emitted from a light converting part of a phosphor wheel of a light generating system according to any one of Figs. 1, 2, 4 and 5.

[0065] 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.

[0066] DETAILED DESCRIPTION

[0067] 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.

[0068] Fig. 1 schematically shows a light generating system 1 according to the invention. Generally, and irrespective of the embodiment, the light generating system 1 comprises a first laser light source 2 providing first laser light 4, a phosphor wheel 8 configured to provide converted light 13, a first optical arrangement 9, a dichroic unit 10, a beam splitting unit 11, a reflective diffuser arrangement 15 and a second optical arrangement 12 configured to provide an added light beam 20.

[0069] The first laser light source 2 is a first laser bank providing, when in operation, first laser light 4. The first laser bank 2 comprises a plurality, such as an array, of lasers. The first laser bank 2 may in this embodiment further comprise a plurality, such as an array, of collimating lenses configured and arranged to collimate the laser light emitted by the plurality of lasers. The first laser light 4 may be blue light. The first laser light 4 comprises a first peak emission wavelength XI and a first polarization Pl.

[0070] Generally, and irrespective of the embodiment, the phosphor wheel 8 comprises an illumination track 81, 82. The illumination track 81, 82 comprises a light converting part 81 and a specular reflective part 82. The light converting part 81 is configured to convert at least a part of laser light incident thereon into converted light 13. The converted light 13 is provided with a Lambertian distribution and is emitted from the phosphor wheel 8 under a first angle. Especially when the laser light is blue light, the converted light 13 may be green-yellow light. The specular reflective part 82 is configured to reflect, particularly specularly reflect, at least a part of laser light incident thereon to form specularly reflected light 14. The specularly reflected light 14 is emitted under a second angle. The second angle is different from the first angle. The light converting part 81 and the specular reflective part 82 are arranged sequentially on the illumination track 81, 82 of the phosphor wheel 8. Thereby, during rotation of the phosphor wheel 8 in a direction of rotation DR (cf. Figs. 9A-12B) the light converting part 81 and the specular reflective part 82 are sequentially in time radiated with the laser light.

[0071] Generally, and irrespective of the embodiment, the first optical arrangement 9 is arranged in front of the phosphor wheel 8. The first optical arrangement 9 is configured to off-axis focus the laser light onto the phosphor wheel 8, to collimate the converted light 13, and to off-axis collimate the specularly reflected light 14. The first optical arrangement 9 may be a lens or an array of lenses or a set of lenses.

[0072] Reference is now made to Figs. 7A, 7B, 8A and 8B. As used herein, the term “off-axis collimate” is intended to mean collimate such that the main axis or central axis CA of the collimated light beam, in practice herein being the specularly reflected light 14, does not coincide with the optical axis OA of the system as shown in Fig. 7B. For comparison, Fig. 8B illustrates the ordinary collimation of a light beam, in practice herein being the converted light 13, such that the main axis or central axis CA of the collimated light beam coincides with the optical axis OA of the system. As used herein, the term off-axis focus is intended to mean focusing a light beam with a main axis or central axis CA which does not coincide with the optical axis OA of the system such that the focal point P of the focused light beam coincides with the optical axis OA of the system shown in Figs. 7A and 8A.

[0073] Generally, and irrespective of the embodiment, the dichroic unit 10 is arranged between the first laser bank 2 and the phosphor wheel 8, and more particularly between the first laser bank 2 and the first optical arrangement 9. The dichroic unit 10 is configured to direct the laser light towards the phosphor wheel 8 and to direct the converted light 13 and the specularly reflected light 14 towards a beam splitting unit 11.

[0074] In the embodiment shown in Fig. 1 the dichroic unit 10 is a transmissive dichroic unit 10. In the embodiment shown in Fig. 1 the dichroic unit 10 comprises a dichroic mirror 21 and a specular mirror 22. The specular mirror 22 is arranged behind the dichroic mirror 21. More particularly, the specular mirror 22 comprises a first center point Cl, the dichroic mirror 21 comprises a second center point C2, and the specular mirror and the dichroic mirror are arranged such that the second center point C2 is offset from the first center point Cl. The dichroic mirror 21 is configured to transmit the specularly reflected light 14 and thus also the laser light in general, and to reflect the converted light 13. Thus, the specularly reflected light 14 is transmitted though the dichroic mirror 21 and reflected by the specular mirror 22 to redirect the specularly reflected light 14 towards the beam splitting unit 11. The converted light 13 is reflected by the dichroic mirror 21 towards the beam splitting unit 11. The specular mirror 22 comprises a first width Wl. The dichroic mirror 21 comprises a second width W2. The second width W2 is larger than the first width Wl, i.e., W2 > Wl.

[0075] In the embodiment shown in Fig. 1, the above-mentioned laser light is the first laser light 4 provided from the first laser bank 2. Therefore, and referring also to Figs. 12A and 12B, the light converting part 81 is thus configured to convert at least a part of the first laser light 4 into the converted light 13. Especially when the first laser light 4 is blue light, the converted light 13 may be green-yellow light. Referring also to Figs. 11 A and 1 IB, the specular reflective part 82 is configured to specularly reflect at least a part of the first laser light 4 into the specularly reflected light 14. The first optical arrangement 9 is configured to off-axis focus the first laser light 4 onto the phosphor wheel 8 (cf. Figs. 11 A and 12A), to collimate the converted light 13 (cf. Fig. 12B), and to off-axis collimate the specularly reflected light 14 (cf. Fig. 1 IB). The dichroic unit 10 is configured to direct the first laser light 4 towards the phosphor wheel 8 and to direct the converted light 13 and the specularly reflected light 14 towards a beam splitting unit 11. The dichroic mirror 21 is configured to transmit the specularly reflected light 14, and thus also the first laser light 4 in general, and to reflect the converted light 13.

[0076] The beam splitting unit 11 is configured to receive the specularly reflected light 14 and the converted light 13. The beam splitting unit 11 is configured to split the specularly reflected light 14 and the converted light 13 such that the specularly reflected light 14 is redirected onto a reflective diffuser arrangement 15, and such that the converted light 13 is redirected towards a light output of the light generating system 1.

[0077] The reflective diffuser arrangement 15 is configured to receive the specularly reflected light 14. The reflective diffuser arrangement 15 is configured to diffuse or convert the specularly reflected light 14 into diffuse laser light 19. The reflective diffuser arrangement 15 is a polarization maintaining reflective diffuser arrangement.

[0078] The reflective diffuser arrangement 15 comprises a diffuser 16, a third optical arrangement 17 and a wave plate 18. The third optical arrangement 17 is configured to focus the specularly reflected light 14 onto the diffuser 16. The third optical arrangement 17 is arranged in front of, or upstream of the diffuser 16. The third optical arrangement 17 may be a lens or an array of lenses or a set of lenses. The diffuser 16 is a polarization maintaining diffuser. The diffuser 16 is configured to receive the specularly reflected light 14, to generate diffuse laser light 19 and to reflect the diffuse laser light 19 back in a direction towards the third optical arrangement 17. The diffuser 16 may comprise a diffusing element or layer arranged on a reflective element or layer. The third optical arrangement 17 may further be configured to collimate the diffuse laser light 19. The wave plate 18 is configured to alter the polarization of the specularly reflected light 14 before the specularly reflected light 14 is focused by the third optical arrangement 8. The wave plate 18 is thus arranged in front of, or upstream of, the third optical arrangement 17. The wave plate 18 may be a quarter wave (1 / 4X) plate. The second optical arrangement 12 is arranged to receive the diffuse laser light 19 and the converted light 13. The second optical arrangement 12 configured to combine the diffuse laser light 19 and the converted light 13 into an added light beam 20. The added light beam 20 forms the light output of the light generating system 1. The second optical arrangement 12 is or comprises a beam combiner 23. The second optical arrangement 12 is as shown in Fig. 1 arranged downstream of the beam splitting unit 11.

[0079] The light generating system 1 may further comprise an optional controller 30. The controller 30 is configured to control the first laser bank 2 and thus the first laser light 4. The controller 30 may be configured to control one or more relevant parameters of the first laser light 4, the second laser light 5, or the system light, such as the peak wavelength, the peak frequency, and the peak (correlated) color temperature.

[0080] Fig. 2 schematically shows another embodiment of a light generating system 100 according to the invention. In the embodiment shown in Fig. 2 the dichroic unit 10 is a transmissive dichroic unit 10. In the embodiment shown in Fig. 2 the light generating system 100 is very similar to the light generating system 1 of Fig. 1 but differs therefrom in virtue of the following features.

[0081] The light generating system 100 comprises a second laser light source 3 providing second laser light 5, and a laser light combiner 6 arranged and configured to combine the first laser light 3 and the second laser light 5 into combined laser light 7.

[0082] The second laser light source 3 is a second laser bank providing second laser light 5. The second laser bank 3 comprises a plurality, such as an array, of lasers. The second laser bank 3 may in this embodiment further comprise a plurality, such as an array, of collimating lenses configured and arranged to collimate the laser light emitted by the plurality of lasers. The second laser light 5 may be blue light. The second laser light 5 comprises a second peak emission wavelength Z2 and a second polarization P2. The first peak emission wavelength XI is different from the second peak emission wavelength X2. The first polarization Pl is the same as the second polarization P2.

[0083] The laser light combiner 6 is arranged and configured to combine the first laser light 3 and the second laser light 5 into combined laser light 7. The combined laser light 7 may be blue light. The laser light combiner 6 may for instance be a reflective polarizer. The laser light combiner 6 is further configured to send the combined laser light 7 towards the phosphor wheel 8. Thus, in the embodiment shown in Fig. 2, the laser light incident on the parts 81, 82 of the phosphor wheel 8, off-axis focused by the first optical arrangement 9 and directed towards the phosphor wheel 8 by the dichroic unit 10, respectively, is the combined laser light 7.

[0084] The light converting part 81 is thus configured to convert a first part of the combined laser light 7 into the converted light 13. Especially when the combined laser light 7 is blue light, the converted light 13 may be green-yellow light. The specular reflective part 82 is configured to specularly reflect a second part of the combined laser light 7 into the specularly reflected light 14.

[0085] The first optical arrangement 9 is thus configured to off-axis focus the combined laser light 7 onto the phosphor wheel 8, to collimate the converted light 13, and to off-axis collimate the specularly reflected light 14.

[0086] The dichroic unit 10 is as shown in Fig. 2 arranged between the laser light combiner 6 and the phosphor wheel 8, and more particularly between the laser light combiner 6 and the first optical arrangement 9. The dichroic unit 10 is thus configured to direct the combined laser light 7 towards the phosphor wheel 8 and to direct the converted light 13 and the specularly reflected light 14 towards a beam splitting unit 11.

[0087] Like in the embodiment shown in Fig. 1 the dichroic unit 10 is a transmissive dichroic unit 10 and comprises a dichroic mirror 21 and a specular mirror 22. The dichroic mirror 21 is configured to transmit the specularly reflected light 14, and thus also the combined laser light 7 in general, and to reflect the converted light 13.

[0088] The light generating system 100 may further comprise an optional controller 30. The controller 30 is configured to, individually or together, control the first laser bank 2, and thus the first laser light 4, and the second laser bank 3, and thus the second laser light 5. The controller 30 may be configured to control one or more relevant parameters of the first laser light 4 and of the second laser light 5, respectively, such as the peak wavelength, the peak frequency, and the peak (correlated) color temperature.

[0089] Fig. 3 schematically shows another embodiment of a light generating system 101 according to the invention. The light generating system 101 differs from the light generating system 100 described above with reference to Fig. 2 in virtue of the following features.

[0090] In the embodiment shown in Fig. 3 the dichroic unit 10 is a reflective dichroic unit 10. In the embodiment shown in Fig. 3 the dichroic unit 10 comprises a dichroic mirror 21. The dichroic mirror 21 is configured to transmit the converted light 13, and to reflect the combined laser light 7, or if only a first laser bank 2 is provided the first laser light 4. Thus, the combined laser light 7, or if only a first laser bank 2 is provided the first laser light 4, is reflected by the dichroic mirror 21 to redirect the combined laser light 7, or if only a first laser bank 2 is provided the first laser light 4, towards the phosphor wheel 8 - cf. Fig. 9A and 10 A. The converted light 13 is in part transmitted through the dichroic mirror 21 towards the beam splitting unit 11, and in part led around the dichroic mirror 21 towards the beam splitting unit 11 as indicated by a wide arrow in Fig. 3 and as illustrated in Fig. 10B. The specularly reflected light 14 is led around the dichroic mirror 21 as indicated by a thin arrow in Fig. 3 and as illustrated in Fig 9B.

[0091] Fig. 4 schematically shows another embodiment of a light generating system

[0092] 102 according to the invention. In the embodiment shown in Fig. 3 the dichroic unit 10 is a transmissive dichroic unit 10. The light generating system 102 differs from the light generating systems 100 and 101 described above with reference to Figs. 2 and 3 in virtue of the following features.

[0093] In the embodiment shown in Fig. 4 the dichroic unit 10 is a transmissive dichroic unit 10. The light generating system 102 further comprises a flat polarization converter 26, a mirror 27 and a polarizing beam splitting unit 28.

[0094] The flat polarization converter 26 is arranged downstream of the beam splitting unit 11 to receive the specularly reflected light 14. The flat polarization converter 26 is configured to convert the polarization of the specularly reflected light 14 to generate polarization converted light 29.

[0095] The mirror 27 is arranged downstream of the flat polarization converter 26. The mirror 27 is configured to reflect the polarization converted light 29 towards the polarizing beam splitting unit 28.

[0096] The polarizing beam splitting unit 28 is arranged downstream of the mirror 27. The polarizing beam splitting unit 28 is configured to reflect the polarization converted light 29 towards the reflective diffuser arrangement 15. The polarizing beam splitting unit 28 is further configured to transmit the diffuse light 19 generated by the reflective diffuser arrangement 15 towards the second optical arrangement 12.

[0097] The added light beam 20 thus in this embodiment comprises the polarization converted light 29 and the converted light 13. It is noted that any one of the light generating systems 101, 103 and 104 described herein above or below may also be fitted with a flat polarization converter 26, a mirror 27 and a polarizing beam splitting unit 28 as described above.

[0098] Fig. 5 schematically shows another embodiment of a light generating system

[0099] 103 according to the invention. In the embodiment shown in Fig. 5 the dichroic unit 10 is a transmissive dichroic unit 10. The light generating system 103 differs from the light generating systems 100 and 101 described above with reference to Figs. 2 and 3 in virtue of the construction of the second optical arrangement 12 only.

[0100] As shown in Fig. 5, the second optical arrangement 12 of the light generating system 103 generally comprises a further beam splitting unit 24, a specular reflective mirror 25 and a further beam combiner 23. As shown in Fig. 5, the second optical arrangement 12 is thus arranged at the beam splitting unit 11.

[0101] The further beam splitting unit 24 is configured to transmit the specularly reflected light 14. The further beam splitting unit 24 is configured to reflect the diffuse laser light 19 towards the specular reflective mirror 25. The further beam splitting unit 24 is thus arranged between the beam splitting unit 11 and the reflective diffuser arrangement 15.

[0102] The specular reflective mirror 25 is configured to reflect the diffuse laser light 19 reflected by the further beam splitting unit 24 towards the further beam combiner 23. The specular reflective mirror 25 is thus arranged downstream of the further beam splitting unit 24. The specular reflective mirror 25 may have a reflectivity of at least 80%, preferably at least 90%.

[0103] The further beam combiner 23 is configured to combine the diffuse laser light 19 and the converted light 13 into the added light beam 20. The further beam combiner 23 is thus arranged downstream of the specular reflective mirror 25.

[0104] Fig. 6 schematically shows another embodiment of a light generating system 104 according to the invention. In the embodiment shown in Fig. 6 the dichroic unit 10 is a reflective dichroic unit 10. The light generating system 104 differs from the light generating system 101 described above with reference to Fig. 3 in virtue of the construction of the second optical arrangement 12 only.

[0105] As shown in Fig. 6, the second optical arrangement 12 of the light generating system 104 generally comprises a further beam splitting unit 24, a specular reflective mirror 25 and a further beam combiner 23.

[0106] The further beam splitting unit 24 is configured to transmit the specularly reflected light 14. The further beam splitting unit 24 is configured to reflect the diffuse laser light 19 towards the specular reflective mirror 25. The further beam splitting unit 24 is thus arranged between the beam splitting unit 11 and the reflective diffuser arrangement 15.

[0107] The specular reflective mirror 25 is configured to reflect the diffuse laser light 19 reflected by the further beam splitting unit 24 towards the further beam combiner 23. The specular reflective mirror 25 is thus arranged downstream of the further beam splitting unit 24.

[0108] The further beam combiner 23 is configured to combine the diffuse laser light 19 and the converted light 13 into the added light beam 20. The further beam combiner 23 is thus arranged downstream of the specular reflective mirror 25.

[0109] 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.

[0110] For instance, any of the light generating systems 101-104 shown in Figs. 3-6 may be made in a version comprising only the first laser bank 2, and thus no second laser bank 3. It may also be feasible to provide a light generating system according to the invention with a third laser bank configured to provide, in operation third laser light, and to provide one or more beam combiners configured to combine the first laser light 4, the second laser light 5 and the third laser light into combined laser light 7.

[0111] 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) configured to provide, in operation, system light, the light generating system comprising: a first laser bank (2) providing, in operation, first laser light (4), the first laser light (4) being blue light having a first peak emission wavelength (XI) and a first polarization (Pl), a second laser bank (3) providing, in operation, second laser light (5), the second laser light (5) being blue light having a second peak emission wavelength (X2) and a second polarization (P2), wherein the first peak emission wavelength (XI) is different from the second peak emission wavelength (X2), and wherein the first polarization (Pl) is the same as the second polarization (P2), a laser light combiner (6) configured to combine the first laser light (4) and the second laser light (5) into combined laser light (7), wherein the laser light combiner (6) is a dichroic mirror, and wherein the laser light is the combined laser light (7), a phosphor wheel (8) comprising an illumination track (81, 82), the illumination track comprising: a light converting part (81) configured to convert at least a part of a laser light into converted light (13) having a Lambertian distribution, and a specular reflective part (82) configured to specularly reflect at least a part of the laser light into specularly reflected laser light (14), the light converting part and the specular reflective part being sequentially arranged such that during rotation of the phosphor wheel the light converting part and the specular reflecting part are sequentially in time radiated with the laser light, a first optical arrangement (9) configured (i) to off-axis focus the laser light onto the phosphor wheel, (ii) to collimate the converted light (13), and (iii) to off-axis collimate the specularly reflected laser light (14), a dichroic unit (10) configured a. to reflect the laser light towards the phosphor wheel and (ii) to transmit the converted light (13) towards a beam splitting unit (11) and (iii) to transmit the specularlyreflected laser light (14) towards the beam splitting unit (11) or to allow the specularly reflected laser light (14) to pass by towards the beam splitting unit (11), or b. to transmit the laser light towards the phosphor wheel and (ii) to reflect the converted light (13) towards the beam splitting unit (11) and (iii) to reflect the specularly reflected laser light (14) towards the beam splitting unit (11), the beam splitting unit (11) being configured to split the specularly reflected laser light (14) and the converted light (13) such that the specularly reflected laser light (14) is transmitted through a quarter wave, 1 , plate (18) and focused onto a polarization maintaining reflective diffuser arrangement (15), the polarization maintaining reflective diffuser arrangement (15) being configured to diffuse the specularly reflected laser light (14) into diffused laser light (19), and a second optical arrangement (12) configured to combine the diffused laser light (19) and the converted light (13) into an added light beam (20) of system light, wherein the combined laser light (7) is blue light, wherein the converted light (13) is green-yellow light, and wherein the system light is white light having a correlated color temperature in a range from 2000 K to 10000K and a CRI of at least 70.

2. A light generating system according to claim 1, wherein the dichroic unit (10) comprises a dichroic mirror (21), wherein, during operation of the light generating system, the specularly reflected laser light (14) is passing by the dichroic mirror (21), and wherein the converted light (13) is partly passing by the dichroic mirror (21) and partly transmitted through the dichroic mirror.

3. A light generating system according to claim 1, wherein the dichroic unit (10) comprises a dichroic mirror (21) and a specular mirror (22), wherein the dichroic mirror (21) is configured to reflect the converted light (13) and to transmit the first laser light (4) or the specularly reflected laser light (14), and wherein the specular mirror (22) is arranged in such a way with respect to the dichroic mirror (21) that the specularly reflected laser light (14) is reflected by the specular mirror (22) and redirected towards the beam splitting unit (11).

4. A light generating system according to claim 3, wherein the specular mirror (22) comprises a first center point (Cl), wherein the dichroic mirror (21) comprises a second center point (C2), and wherein the specular mirror and the dichroic mirror are arranged suchthat the second center point is offset from the first center point in such a way that the laser light (4 or 7) is passing by the specular mirror (22).

5. A light generating system according to any one of the preceding claims, wherein a difference between the first peak emission wavelength (XI) and the second peak emission wavelength (12) is equal to or larger than 20 nm.

6. A light generating system according to any one of the above claims, wherein the polarization maintaining reflective diffuser arrangement (15) comprises: a polarization maintaining diffuser (16), a third optical arrangement (17) configured to focus the specularly reflected laser light (14) onto the polarization maintaining diffuser (16), and the quarter wave plate (18) configured to alter the polarization of specularly reflected laser light (14) before being focused by the third optical arrangement.

7. A light generating system according to claim 6, wherein one or more of the following apply: the third optical arrangement (17) is further configured to collimate the diffuse laser light (19), and the third optical arrangement (17) is a lens or a lens array.

8. A light generating system according to any one of the above claims, wherein the beam splitting unit (11) is a dichroic mirror and wherein the first optical arrangement (9) is a lens or a lens array.

9. A light generating system according to any one of the above claims, wherein the second optical arrangement (12) is arranged at or downstream of the beam splitting unit (11).

10. A light generating system according to any one of the above claims 1-9, wherein the second optical arrangement (12) comprises a further beam combiner (23) being configured and arranged to combine the diffused laser light (19) and the converted light (13) into an added light beam (20), or whereinthe second optical arrangement (12) comprises (i) a further beam combiner (23) being configured and arranged to combine the diffused laser light (19) and the converted light (13) into the added light beam (20), (ii) a further beam splitting unit (24) being configured to reflect the diffuse laser light (19) and transmit the specularly reflected laser light (14), and (iii) a mirror (25) configured to reflect the diffuse laser light reflected by the further beam splitting unit (24) towards the further beam combiner (23).

11. A light generating system according to claim 10, wherein at least one of the following apply: the further beam splitting unit (24) is a dichroic mirror, and the mirror (25) is a specular reflective mirror.

12. A light generating system according to any one of the above claims, and further comprising: a flat polarization converter (26) arranged downstream of the beam splitting unit (11) to receive the specularly reflected laser light (14), the flat polarization converter (26) being configured to convert the polarization of the specularly reflected laser light (14) to generate polarization converted light (29), and a mirror (27) configured to reflect the polarization converted light (29) towards a polarizing beam splitting unit (28), wherein the polarization maintaining reflective diffuser arrangement (15) comprises a polarization maintaining diffuser (16), and wherein the polarizing beam splitting unit (28) is configured to reflect the polarization converted light (29) towards the polarization maintaining reflective diffuser arrangement (15) and to transmit the diffused light (19) towards the second optical arrangement (12).

13. A light generating system according any one of the preceding claims, further comprising a controller (30) configured to individually control one or both of: the first laser bank (2), and thus the first laser light (4), and, the second laser bank (3), and thus the second laser light (5), individually from or together with the first laser bank.

14. A light generating system according to claim 12, wherein the controller (30) is further configured to control one or more of the first peak wavelength, first second peakwavelength, the first peak frequency, the second peak frequency, the correlated color temperature of the system light, and the CRI of the system light.

15. A lighting fixture comprising a light generating system according to any one of the above claims.

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