LIGHTING DEVICE INCLUDING PUMP RADIATION SOURCE

Abstract

A lighting device is provided with a pump radiation source for emitting pump radiation, a first phosphor element for converting the radiation into a first conversion light, a second phosphor element for generating a second conversion light, and a coupling-out mirror arranged downstream of the first element in a beam path with at least part of the first light. The first light is a broadband conversion light having components in first and second spectral ranges, and the coupling-out mirror is transmissive only in one of the two ranges such that, lights having first and second spectral components in the first and second spectral ranges are separated. The second element is arranged in a beam path with the light having the second component and, in response to this excitation, emits the second light, which can be used jointly with the light having the first component in order to increase the efficiency.

Claims

1. A lighting device comprising a pump radiation source for emitting pump radiation, a first phosphor element for converting the pump radiation into a first conversion light, a second phosphor element for generating a second conversion light, and a coupling-out mirror, which is arranged downstream of the first phosphor element in a beam path with at least part of the first conversion light, wherein the first conversion light is a broadband conversion light having components in a first spectral range and a second spectral range, which is different from the first spectral range, wherein the coupling-out mirror arranged in the beam path with at least part of the first conversion light is transmissive only in one of the two spectral ranges but is reflective in the other spectral range, such that, downstream of the coupling-out mirror, light having a first spectral component in the first spectral range and light having a second spectral component in the second spectral range are present in a separated fashion, wherein at least part of the light having the first spectral component is available at an output of the lighting device, and wherein the second phosphor element is arranged in a beam path with at least part of the light, separated by the coupling-out mirror, having the second spectral component and, in response to this excitation, emits the second conversion light, which can be used jointly with the light having the first spectral component in order to increase the efficiency.

2. The lighting device as claimed in claim 1, wherein the light having the second spectral component, with which the second phosphor element is excited, has a shorter wavelength than the light having the first spectral component, and the second conversion light emitted by the second phosphor element has a longer wavelength than the light having the second spectral component.

3. The lighting device as claimed in claim 2, wherein the first conversion light is yellow light, the light having the first spectral component is red light, the light having the second spectral component is green light, and the second conversion light is red light.

4. The lighting device as claimed in claim 3, wherein the light having the first spectral component has a dominant wavelength of at least 580 nm and the second conversion light is deep-red light having a dominant wavelength of at least 605 nm.

5. The lighting device as claimed in claim 1, wherein the coupling-out mirror is transmissive in the first spectral range and reflective in the second spectral range.

6. The lighting device as claimed in claim 1, wherein a limiting wavelength between the first spectral range and the second spectral range is at least 570 nm and at most 610 nm.

7. The lighting device as claimed in claim 1, wherein at least part of the light having the first spectral component, downstream of the coupling-out mirror is available in an output beam path at the output of the lighting device, wherein a beam path having at least part of the second conversion light, at least in sections, is guided along the same output beam path and is available at the same output.

8. The lighting device as claimed in claim 1, wherein the first and the second phosphor elements are provided in each case in layer form, wherein these phosphor element layers are arranged in direct optical contact with one another.

9. The lighting device as claimed in claim 7, wherein a coupling-in mirror is arranged in the beam path having at least part of the first conversion light, on which coupling-in mirror the beam path having at least part of the second conversion light is incident, wherein the coupling-in mirror is transmissive for the first conversion light and reflects the second conversion light or is reflective for the first conversion light and transmits the second conversion light, such that the beam path having at least part of the second conversion light, downstream of the coupling-in mirror and the coupling-out mirror, is coupled to the output beam path.

10. The lighting device as claimed in claim 1, wherein the second phosphor element is operated in transmission, and wherein the beam path having at least part of the light having the second spectral component that is separated by the coupling-out mirror is guided onto an incidence side of the second phosphor element and the second conversion light is guided away from an emission side opposite thereto.

11. The lighting device as claimed in claim 10, wherein a decoupling mirror is arranged between the first and the second phosphor elements, the decoupling mirror being reflective in the first spectral range and transmissive in the second spectral range.

12. The lighting device as claimed in claim 11, wherein the decoupling mirror is provided in a direct optical contact with the first and/or the second phosphor element.

13. The lighting device as claimed in claim 11, wherein at least part of the light having the first spectral component, downstream of the coupling-out mirror is available in an output beam path at the output of the lighting device, wherein a beam path having at least part of the second conversion light, at least in sections, is guided along the same output beam path and is available at the same output, wherein a coupling-in mirror is arranged in the beam path having at least part of the first conversion light, on which coupling-in mirror the beam path having at least part of the second conversion light is incident, wherein the coupling-in mirror is transmissive for the first conversion light and reflects the second conversion light or is reflective for the first conversion light and transmits the second conversion light, such that the beam path having at least part of the second conversion light, downstream of the coupling-in mirror and the coupling-out mirror, is coupled to the output beam path, and wherein the beam path having at least part of the second conversion light is guided past the first and the second phosphor elements to the coupling-in mirror.

14. The lighting device as claimed in claim 1, wherein the second phosphor element is arranged upstream of the coupling-out mirror in the beam path having at least part of the first conversion light, wherein the coupling-out mirror guides a part not converted upon the first passage through the second phosphor element as the light having the second spectral component back to the second phosphor element.

15. The lighting device as claimed in claim 1, wherein the first phosphor element is provided on a rotary body, which is mounted rotatably about a rotation axis.

16. The lighting device as claimed in claim 15, wherein the second phosphor element is provided on a rotary body, which is mounted rotatably about a rotation axis.

17. The lighting device as claimed in claim 16, wherein the first and the second phosphor elements are arranged on the same rotary body which is mounted rotatably, wherein the first and the second phosphor elements are arranged on different sides of a main body of a phosphor wheel.

18. The lighting device as claimed in claim 15, wherein the coupling-out mirror is provided on a rotary body, which is mounted rotatably about a rotation axis.

19. The lighting device as claimed in claim 15, wherein the coupling-out mirror is transmissive or reflective for the pump radiation.

20. The use of a lighting device for illumination with a mixture of a light having a first spectral component and a second conversion light comprising, emitting pump radiation by a pump radiation source, converting the pump radiation into a first conversion light by a first phosphor element, generating the second conversion light by a second phosphor element, and arranging a coupling-out mirror, downstream of the first phosphor element in a beam path, with at least part of the first conversion light, wherein the first conversion light is a broadband conversion light having components in a first spectral range and a second spectral range, which is different from the first spectral range, wherein the coupling-out mirror arranged in the beam path with at least part of the first conversion light is transmissive in one of the two spectral ranges but is reflective in the other spectral range, such that, downstream of the coupling-out mirror, light having the first spectral component in the first spectral range and light having a second spectral component in the second spectral range are present in a separated fashion, wherein at least part of the light having the first spectral component is available at an output of the lighting device, and wherein the second phosphor element is arranged in a beam path with at least part of the light, separated by the coupling-out mirror, having the second spectral component and, in response to this excitation, emits the second conversion light, which can be used jointly with the light having the first spectral component in order to increase the efficiency.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present disclosure is explained in greater detail below on the basis of exemplary embodiments, wherein the individual features in the context of the alternative independent claims may also be essential to the present disclosure in a different combination and, furthermore, no distinction is also drawn specifically between the claim categories.

[0059] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the disclosed embodiments. In the following description, various embodiments described with reference to the following drawings, in which:

[0060] FIG. 1 shows a schematic diagram of a spectrum for illustrating the concept according to the present disclosure;

[0061] FIG. 2 shows a first lighting device according to the present disclosure including two phosphor elements arranged at a distance from one another, said phosphor elements being operated in each case in reflection;

[0062] FIG. 3 shows a second lighting device according to the present disclosure, the basic construction of which corresponds to that of the lighting device in accordance with FIG. 2, but is optimized for a more efficient utilization of the second conversion light;

[0063] FIG. 4 shows a third lighting device according to the present disclosure, the basic construction of which corresponds to that of the lighting device in accordance with FIG. 3, but is optimized toward a more compact arrangement;

[0064] FIG. 5 shows a fourth lighting device according to the present disclosure, the basic construction of which corresponds to those of the lighting devices in accordance with FIGS. 3 and 4, but is realized with an integrated coupling-out/coupling-in mirror element;

[0065] FIG. 6 shows a fifth lighting device according to the present disclosure, in which the two phosphor elements are provided in direct optical contact with one another;

[0066] FIG. 7 shows a sixth lighting device according to the present disclosure including a first phosphor element operated in reflection and a second phosphor element arranged at a distance therefrom;

[0067] FIG. 8 shows a seventh lighting device according to the present disclosure including a first phosphor element operated partly in reflection, partly in transmission, and a second phosphor element arranged at a distance therefrom and operated in reflection;

[0068] FIG. 9 shows an eighth lighting device according to the present disclosure including a first phosphor element operated in reflection and a second phosphor element provided in direct optical contact therewith and operated in transmission;

[0069] FIG. 10 shows a ninth lighting device according to the present disclosure, the basic construction of which corresponds to that of the lighting device in accordance with FIG. 9, but in which the coupling-out mirror is provided at a distance from the first phosphor element.

DETAILED DESCRIPTION

[0070] FIG. 1 shows, in a schematic diagram, spectra for illustrating the concept of the present disclosure. The short-wave pump radiation 1, namely blue pump light having a dominant wavelength of approximately 450 nm, is converted into yellow broadband conversion light 2 by a first phosphor element (YAG:Ce). For the red channel of a multi-channel light source, however, it is possible to use thereof only a first spectral component 3a in a first spectral range 4a, that is to say the component in the red. If this were achieved merely by filtering, a second spectral component 3b in a second spectral range 4b would remain unused.

[0071] The present approach now consists in firstly using the first spectral component 3a directly as red light and making the second spectral component 3b, separated therefrom for this purpose, likewise usable for the red channel, to be precise by means of a renewed conversion. With the second spectral component 3b, that is to say the green/yellow-green light, a second phosphor element (EU-doped Ca, Sr, Ba).sub.2Si.sub.5N.sub.8) is excited, which emits a second, deep-red conversion light 5 in response to this excitation. Said conversion light is usable jointly with the light having the first spectral component 3a for the red channel.

[0072] The yellow broadband conversion light 2 also has another spectral component 3c at lower energies relative to the first spectral component 3a, namely in the deep-red. Although this component could also be used for the red channel, it is cut off as explained below with reference to FIG. 2.

[0073] FIG. 2 then shows a first corresponding lighting device 6 including a first phosphor element 7 and a second phosphor element 8. The first phosphor element 7 is provided on a phosphor wheel 10 mounted rotatably about a rotation axis 9, said phosphor wheel being shown in a schematic section in the figure (the sectional plane includes the rotation axis 9).

[0074] At the point in time shown in FIG. 2, that is to say at the shown rotary position of the phosphor wheel 10, a beam path 11 of the pump radiation is incident on the first phosphor element 7, which emits the first conversion light (yellow broadband conversion light) in response to this excitation. The first phosphor element 7 is operated in reflection, and a beam path 12 of the first conversion light is guided in sections along the beam path 11 of the pump radiation (in the opposite direction). By means of a first optical unit 13, illustrated schematically as a converging lens in the present case, firstly the pump radiation is focused onto the first phosphor element 7 and secondly the first conversion light emitted divergently with a Lambertian emission characteristic is collimated.

[0075] A wavelength-dependent pump radiation mirror 14 positioned downstream of the first optical unit 13 relative to the first conversion light is reflective for the pump radiation, but transmits the first conversion light. The latter penetrates through a further wavelength-dependent mirror (which in this respect is likewise transmissive), explained in detail below, and is focused onto a coupling-out mirror 15. Said coupling-out mirror 15 is mounted rotatably in a manner comparable with the first phosphor element 7, specifically on a filter wheel 16 (the sectional plane once again contains the rotation axis 17).

[0076] The coupling-out mirror 15 is transmissive in the first spectral range 4a but reflective in the second spectral range 4b. Therefore, the first spectral component 3a of the first conversion light is transmitted and is available as red light at an output 18 of the lighting device 6. On account of the wavelength-dependent mirror 23, however, the entire first conversion light does not arrive at the coupling-out mirror 15, rather a deep-red component 3c is reflected out of the beam path, cf. FIG. 1.

[0077] The light having the second spectral component 3b, that is to say green light, is reflected at the coupling-out mirror 15. The second phosphor element 8 is arranged in a beam path 19 of the light having a second spectral component; the light having the second spectral component is focused thereon, specifically by means of a first phosphor element optical unit 20a assigned to the second phosphor element 8. The second conversion light thereupon emitted thereby is collimated by means of a second phosphor element optical unit 20b. In this case, the entire second conversion light is not collected, but rather only the part at a corresponding solid angle.

[0078] A coupling-in mirror 23 is arranged in a beam path 21 of the second conversion light, which beam path is guided via a mirror (full reflective coating) 22, said coupling-in mirror being reflective for the second conversion light, but transmissive for the first conversion light apart from the deep-red component thereof. The light having the first spectral component has a dominant wavelength of approximately 600 nm, and the second conversion light has a dominant wavelength of more than 620 nm. Ideally, the spectra do not overlap (in contrast to what is shown in FIG. 1) and the coupling-in mirror 23 is transmissive for the entire first conversion light.

[0079] Downstream of the coupling-in mirror 23, the beam path 21 of the second conversion light extends along the beam path 12 of the first conversion light, that is to say is focused jointly with the latter onto the coupling-out mirror 15 by means of a focusing optical unit 24. Said coupling-out mirror is not only transmissive in the first spectral range, but as a low-pass filter is then generally transmissive at longer wavelengths, that is to say that the second, deep-red conversion light is coupled out jointly with the red light; an output beam path is present downstream of the coupling-out mirror 15.

[0080] At a different point in time than that shown in the figure, the phosphor wheel 10 may then have rotated further somewhat and a different phosphor element than the first phosphor element 7 may be excited, for example for emitting green conversion light, which may then pass through both the pump radiation mirror 14 and the coupling-in mirror 23 in transmission. The filter wheel 16 has then also rotated further in a manner corresponding to the phosphor wheel 10, such that the green conversion light is not incident on the coupling-out mirror 15 and green light is present at the output 18.

[0081] To summarize, therefore, the wavelength-dependent pump radiation mirror 14 is reflective for the pump radiation, but transmissive for the rest; its limiting wavelength may be 460 nm, for example. The coupling-in mirror 23 is transmissive up to a limiting wavelength of approximately 620 nm, and is reflective thereabove, that is to say at lower energies (high-pass filter). The coupling-out mirror 15 is a low-pass filter having a limiting wavelength at approximately 590 nm, which thus transmits longer-wavelength (red and deep-red) light with respect thereto.

[0082] FIG. 3 shows a further lighting device 6 according to the present disclosure, which in terms of its basic construction corresponds to the lighting device in accordance with FIG. 2. In this respect and generally, the same reference signs designate parts having the same function and reference is then also made in each case to the corresponding description of the other figures.

[0083] The first conversion light emitted by the first phosphor element 7 in response to the excitation with the pump radiation is in turn guided to the coupling-out mirror 15, which transmits the red component to the output 18 and reflects the green component to the second phosphor element 8. The latter is thus in turn arranged in a beam path 19 of the light having the second spectral component, but the beam guidance differs from that of the lighting device 6 in accordance with FIG. 2.

[0084] This is because the green light reflected divergently from the coupling-out mirror 15 is firstly collimated by means of a collimation optical unit 31 and is then focused onto the second phosphor element 8 via the phosphor element optical unit 20. In this case, a centroid direction of the excitation light, that is to say of the green light, is perpendicular to the second phosphor element 8, that is to say to the incidence side 32 thereof. The second phosphor element 8 is operated in reflection; the incidence side 32 is identical to the emission side 33. The second conversion light is guided via the same phosphor element optical unit 20, wherein, on account of the arrangement thereof with the optical axis parallel to a main emission direction, the second conversion light is collected from a solid angle range in which the light intensity is the highest on account of the Lambertian emission characteristic.

[0085] In order then to decouple the collected second conversion light from the beam path 19 of the light having the second spectral component (of the green light), a conversion light mirror 34 is provided downstream of the phosphor element optical unit 20, said conversion light mirror being transmissive in the second spectral range, but reflecting the second conversion light. Downstream thereof, the beam path then once again corresponds to that of the lighting device 6 in accordance with FIG. 2; the second, deep-red conversion light is available jointly with the red light at the output 18.

[0086] The lighting device 6 in accordance with FIG. 4 corresponds in principle to that in accordance with FIG. 3, just the angle between the beam path 19 of the light having the second spectral component, that is to say of the reflected green light, and the beam path 12 of the first conversion light at the coupling-out mirror 15 is smaller; the first conversion light (a centroid direction thereof) impinges on the coupling-out mirror 15 more steeply, that is to say at a smaller angle with respect to an axis perpendicular to the coupling-out mirror 15. In the case of the lighting devices 6 in accordance with FIGS. 2 and 3, the angle between centroid direction of the first conversion light and axis was 45°, that is to say that the angle between the two centroid directions (of the first conversion light and of the light having the second spectral component) was correspondingly 90°.

[0087] In the present case, said angle is smaller and the collimation optical unit 31 and the entire downstream part with the second phosphor element 8 accordingly move nearer to the beam path 12 of the first conversion light. This may enable a more compact construction. Moreover, the second conversion light downstream of the conversion light mirror 34 is not additionally guided via a dedicated mirror 22, but rather is guided directly to the coupling-in mirror 23, which in this respect necessitates one component fewer.

[0088] The lighting device 6 in accordance with FIG. 5 is also optimized with regard to the space requirement. In contrast to the previous lighting devices 6, in this case the coupling-out mirror 15 is not arranged on a filter wheel 16, but rather is provided jointly with the coupling-in mirror 23 in an integrated component, namely a so-called X-Cube. The two mirrors 15, 23 thus cross one another, and the beam path 19 of the green light (the light having the second spectral component) and the beam path 21 of the second conversion light run away from the X-Cube and toward the latter along the same path.

[0089] In the X-Cube, the light having the first spectral component is transmitted by both mirrors 15, 23 (the coupling-in mirror 23, which is reflective for the deep-red second conversion light, is also transmissive up to approximately 620 nm, see above), but the light having the second spectral component (green light) is reflected from the coupling-out mirror 15 to the phosphor element optical unit 20. The second, deep-red conversion light emitted by the second phosphor element 8 in response to the excitation is reflected at the coupling-in mirror 23 and is available jointly with the red light at the output 18 of the lighting device 6. The coupling-out mirror 15 may also be designed in a more complex manner with regard to other channels, for instance as a band-stop filter, in order for example to be transmissive for a blue channel (at a different point in time).

[0090] The lighting device 6 in accordance with FIG. 6 differs fundamentally from the embodiments discussed previously insofar as the two phosphor elements 7, 8 previously were provided in a manner spaced apart from one another via an air gap. By contrast, in the case of FIG. 6, they are provided in direct optical contact, to be precise one on top of another. The first phosphor element 7 is in turn provided on a phosphor wheel 10, but the second phosphor element 8 is arranged between a substrate body 60 of the phosphor wheel 10 and the first phosphor element 7. Therefore, the second phosphor element 8 is applied to the substrate body 60 and the first phosphor element 7 is then applied to the second phosphor element 8.

[0091] In response to the excitation with the pump radiation, the first phosphor element 7 emits the first conversion light, to be precise in principle omnidirectionally, that is to say in substantially equal parts at an incidence side 61, which in the present case is also simultaneously an emission side 62, and a rear side opposite thereto. The second phosphor element 8 is provided in a manner adjoining the latter. Such omnidirectional emission behavior is exhibited in general by the phosphor elements 7, 8 discussed in the present case; the fact of whether the conversion light is guided away at an emission side 62 opposite to the incidence side 61 (transmission) or indeed in reflection then depends on the specific arrangement.

[0092] In the case of the lighting device 6 in accordance with FIG. 6, a beam path 12 of the first conversion light emitted at the emission side 62 of the first phosphor element 7 (toward the right in the figure) is in turn focused onto a coupling-out mirror 15 provided on a filter wheel 16. The light having the first spectral component is transmitted thereby and is available as red light at the output 18. However, the coupling-out mirror 15 arranged on a substrate body 63 reflects the light having the second spectral component, that is to say the green light, to be precise back along the same path.

[0093] The green light passes through the wavelength-dependent pump radiation mirror 14, which is thus designed as a low-pass filter having a limiting wavelength between the pump radiation and the broadband conversion light (e.g. at 460 nm). The green light is then incident on the first phosphor element 7 and penetrates through the latter, apart from possible scattering losses, to the second phosphor element 8, where the green light is converted into second, deep-red conversion light, which is guided by the first phosphor element 7 along the beam path 12 of the first conversion light to the wavelength-dependent coupling-out mirror 15 and passes through this low-pass filter, which has its limiting wavelength at approximately 590 nm, and is available at the output 18.

[0094] First conversion light emitted by the first phosphor element 7 at its rear side, opposite to the emission side 62, to the second phosphor element 8 is partly converted by the second phosphor element 8 into deep-red light, which then passes to the coupling-out mirror 15 in the manner just described. The light having the first spectral component, that is to say the red light, penetrates through the second phosphor element 8, apart from scattering, etc., and is reflected at the substrate body 60, which is provided with a specularly reflective surface in order to increase the efficiency, in the direction of the emission side 62 and passes from there via the coupling-out mirror 15 to the output 18.

[0095] In the case of the lighting device 6 in accordance with FIG. 7, the two phosphor elements 7, 8 are arranged once again in a manner spaced apart from one another, wherein the second phosphor element, in contrast to the embodiments in accordance with FIGS. 2 to 5, is arranged directly in the beam path 12 of the first conversion light. The second phosphor element 8 is arranged jointly with the coupling-out mirror 15 on the filter wheel 16, to be precise in direct optical contact with the coupling-out mirror 15 on the other side of the transparent main body 63, namely upstream of the coupling-out mirror 15.

[0096] During passage through the second phosphor element 8, part of the green light contained in the first conversion light is already converted into deep-red light (partial conversion); the transmitted, non-converted part impinges jointly with the rest of the first conversion light on the coupling-out mirror 15. The latter in turn transmits the red light to the output 18, but reflects the light having the second spectral component, that is to say the green light. The latter impinges on the phosphor element 8, which emits second, deep-red conversion light in response to the excitation.

[0097] The deep-red light emitted by the second phosphor element 8 in its side facing the coupling-out mirror 15 passes through the coupling-out mirror 15 jointly with the red light. The deep-red light emitted at the opposite side of the second phosphor element 8 may be guided to the first phosphor element 7 and reflected by it on the rear side thereof, that is to say then back to the coupling-out mirror 15 again. In order to avoid scattering losses here, the rear side of the second phosphor element 8 may, however, also be reflectively coated, namely with an (optional) high-pass filter 71 having a limiting wavelength at approximately 620 nm.

[0098] In the case of the lighting device 6 in accordance with FIG. 8, the two phosphor elements 7, 8 and the coupling-out mirror 15 are arranged on the same phosphor wheel 10, but the two phosphor elements 7, 8 are nevertheless spaced apart from one another. This is because the first 7 and the second phosphor element 8 extend in each case in a dedicated segment, which segments lie on opposite sides relative to the rotation axis 9. Looking at the phosphor wheel 10 along the rotation axis 9, the arrangement is rotationally symmetrical insofar as one segment can be converted into the other segment by a rotation by 180° (about the rotation axis 9).

[0099] Relative to the pump radiation, the coupling-out mirror 15 is arranged upstream of the first phosphor element 7, namely in direct optical contact with the first phosphor element 7. The pump radiation penetrates through the coupling-out mirror, which is designed as a band-stop filter in this case, and is incident on the first phosphor element 7. The first conversion light emitted thereby in response to the excitation is separated by the coupling-out mirror 15, which in turn reflects the green light and transmits the red light (the band-stop filter is reflective in the stop band). The side of the first phosphor element 7 opposite to the coupling-out mirror 15 is optionally provided with a mirror (not illustrated in the present case) which is transmissive in the second spectral range, that is to say transmits the green light; however, red light (the light having the first spectral component) is reflected thereby and guided to the coupling-out mirror 15.

[0100] On the rear side of the first phosphor element 7, the beam path 19 of the green light is guided via an optical unit, in the present case two mirrors 80 (full reflective coating), to the second phosphor element 8. The second, deep-red conversion light emitted by the second phosphor element 8 in response to the excitation is then guided back via the same optical unit 80, penetrates through the optional mirror on the rear side of the first phosphor element 7 (which mirror is again transmissive in the deep-red as a band-stop filter) and also the first phosphor element 7 and passes through the coupling-out mirror 15. The deep-red light is then available jointly with the red light at the output 18.

[0101] In order to supply a blue channel using the lighting device 6 in accordance with FIG. 8 at a different point in time than as shown, the phosphor wheel 10 is provided in a corresponding section with two segments embodied as passages. The blue pump light can pass through these passages, that is to say that the main body 60 of the phosphor wheel 16 may be provided with corresponding slots, for example. Downstream of the first passage, that is to say on the rear side of the phosphor wheel 16, the blue pump light is then guided via the same optical unit 80 as the green light before it passes through the phosphor wheel 16 though the second passage. On the front side of the phosphor wheel (dashed) it may then be directed by a mirror 81 to the pump radiation mirror 14 and be reflected by the latter to the output 18.

[0102] In the embodiment in accordance with FIG. 9, too, the two phosphor elements 7, 8 are arranged on the same phosphor wheel 10, but in direct optical contact with one another; the light thus does not pass through an air gap therebetween in contrast to the arrangement just described. The pump radiation is once again incident on the first phosphor element 7 through the coupling-out mirror 15. From that part of the first conversion light which is emitted toward the coupling-out mirror 15, the coupling-out mirror reflects the green light, that is to say the light having the second spectral component; the red light is transmitted to the output 16.

[0103] A decoupling mirror 90 is arranged between the two phosphor elements 7, 8, that part of the first conversion light which is emitted toward the other side impinging on said decoupling mirror. Said decoupling mirror 90 is a high-pass filter having a limiting wavelength at approximately 590 nm, that is to say transmits the green component of the first conversion light and reflects the red component; the latter is available at the output 16. On the other hand, the green light passes through the decoupling mirror 90, to be precise both green light originally emitted in this direction and green light previously reflected at the coupling-out mirror 15.

[0104] The second phosphor element 8 is arranged downstream of the decoupling mirror 90, said second phosphor element emitting the second, deep-red conversion light in response to the excitation. The beam path 21 of the deep-red light is guided by an optical unit 91 around the phosphor wheel 16 and is coupled to the beam path of the red light, that is to say to the output beam path, by the pump radiation mirror 14, which is simultaneously a coupling-in mirror 23. The mirror 14, 23 is provided for this purpose as a bandpass filter, that is to say is transmissive between two limiting wavelengths at approximately 460 nm and 620 nm, but is reflective therebelow (for the pump radiation) and thereabove (for the deep-red light).

[0105] In the case of the embodiment in accordance with FIG. 10, too, the two phosphor elements 7, 8 are provided in direct optical contact with one another on the same phosphor wheel 10. Equally, a decoupling mirror 90 that is transmissive in the second spectral range is provided between the two phosphor elements 7, 8, and the beam path 21 of the deep-red, second conversion light also corresponds to that in the case of the embodiment in accordance with FIG. 9.

[0106] In contrast thereto, however, in the case of the embodiment in accordance with FIG. 10 the coupling-out mirror 15 is not arranged on the same phosphor wheel 10, but rather at a distance therefrom on a dedicated filter wheel 16. First conversion light emitted by the first phosphor element 7 toward the coupling-out mirror 15 (toward the right in the figure) partly passes through the coupling-out mirror 15, that is to say that once again the red light is transmitted to the output 16, but the green light is reflected back.

[0107] The latter penetrates through the combined pump radiation/coupling-in mirror 14, 23, which as a bandpass filter is transmissive between approximately 460 nm and 620 nm, penetrates through the first phosphor element and is also transmitted by the decoupling mirror 90; the green light thus passes to the second phosphor element 8. The second conversion light emitted thereby in response to this excitation is guided in the manner as explained with reference to FIG. 9.

[0108] While the disclosed embodiments have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosed embodiments as defined by the appended claims. The scope of the disclosed embodiments is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.