Multi-channel light source with modulatable channels and use of a multi-channel light source

Abstract

Multi-channel light source (1) with channels that can be individually modulated for imaging, comprising: a pump radiation source (2) for the emission of pump radiation, a phosphor element (3) with a phosphor for at least partial conversion of the pump radiation into conversion light, which phosphor element is arranged in a beam path (4) of the pump radiation, a first (12) and a second area light modulator (13) for imaging and a beam splitter (8) which is arranged downstream of the phosphor element (3) such that a useful light, which contains at least part of the conversion light, falls on the beam splitter (8), wherein the useful light has a first spectral component in a first spectral range and a second spectral component in a different second spectral range and the beam splitter (8) is transmissive only in one of the two spectral ranges, but reflective in the other, so that the useful light is split downstream of the beam splitter (8) into a first beam path (10) with the first spectral component and a second beam path (11) with the second spectral component, wherein in the first beam path (10) the first area light modulator (12) is arranged as the first channel and in the second beam path (11) the second area light modulator (13) is arranged as the second channel, so that several channels are available based on the useful light, wherein the phosphor element (3) is operated in transmission, i.e. the pump radiation falls on a pump radiation input side of the phosphor element (3) which is opposite a conversion light emission side of the phosphor element (3) and the conversion light is emitted from the conversion light emission side of the phosphor element (3), where the pump radiation is only partially converted and the useful light is a mixture of the pump radiation and the conversion light, wherein the useful light is split downstream of the beam splitter (8) into the pump radiation in the first beam path and the conversion light in the second beam path, characterized by the fact that the phosphor element (3) comprises a first phosphor for emitting the broadband conversion light as a first conversion light and a second phosphor for emitting a second conversion light, wherein the broad-spectrum conversion light is a first useful light and the mixture of the pump radiation and the second conversion light is a second useful light, wherein the beam splitter (8) is provided as a bandpass or bandstop filter, wherein the first and the second useful light fall on the same side of the beam splitter (8) and downstream of the beam splitter (8) a short-wavelength spectral component of the first useful light is combined with a long-wavelength spectral component of the second useful light in the first beam path (10) and a long-wavelength spectral component of the first useful light is combined with a short-wavelength spectral component of the second useful light in the second beam path (11).

Description

Technical field

[0001] The present invention relates to a multi-channel light source with channels that can be individually modulated for imaging. State of the art

[0002] A typical application for such a multi-channel light source is in projection; it can therefore be part of a projection device. If an image of a different color is modulated onto each channel, a mixed image results on average when these images are displayed sequentially. A combination of a pump radiation source and a phosphor element positioned at a distance from it can be used as the light source, allowing for high luminance. Upon excitation with the pump radiation, the phosphor element emits conversion light of a specific color, which can then be assigned to a channel. To provide multiple colors and thus multiple channels, different phosphors, which differ in the color of their respective conversion light, are illuminated sequentially. For this purpose, the phosphors are arranged, for example, on a rotating phosphor wheel.

[0003] DE 10 2012 221 467 A1 relates to a light module for a projection device with a LARP module, wherein a phosphor emitting in the yellow wavelength range is used. The radiation emitted by the phosphor is split into an s-polarized and a p-polarized component by means of a polarization beam splitter. The s-polarized component is further split into a green and a red component by means of a dichroic beam splitter. These components are each fed to an LCD panel of a beamcube. Another LCD panel of the beamcube is driven by radiation from a laser device that emits in the blue wavelength range. A p-polarized RGB signal is therefore available at the output of the beamcube. This is directed to a polarization beam splitter, where it is superimposed with the p-polarized radiation in the yellow wavelength range that has previously passed through an LCD panel.An RGBY signal is available at the output, in which the entire output radiation of the phosphor has been converted without any loss of étendue.

[0004] DE 10 2012 201 192 A1 describes a lighting device equipped with a light-generating unit for producing primary light and with at least one fluorescent wheel optically downstream of the light-generating unit. The fluorescent wheel comprises at least one phosphor for converting the wavelength of the primary light into secondary light, and several fluorescent wheels are optically downstream of the light-generating unit.

[0005] In the publication “Highly Crystalline Rod-Shaped Zn2SiO4:Mn 2+ Phosphorus Particles Prepared in Frontal Exothermic Waves. " by HH Nersisyan et al., published in 2012 in the "Journal of The Electrochemical Society", 159 B406-B410, describes a method for the synthesis of Zn2SiO4:Mn 2+- Phosphor particles with a defined morphology in exothermic frontal waves are enabled. The investigated process involves mixing SiO2, ZnO, and MnCO3 starting particles with a KClO3+CO(NH2)2 redox mixture and an NH4F additive, and combusting the mixture under an argon atmosphere. Zn2SiO4:Mn 2+ Phosphor particles are extracted from the KCl salt formed during synthesis. Characterization of the obtained particles revealed the role of the molten KCl and F ions in the growth process of Zn₂SiO₄:Mn. 2+ - Phosphor particles. The relative emission intensity of the particles produced in this way when excited by UV light is comparable to that of a reference substance.

[0006] EP 1 471 746 A2 relates to a projection device with a light source system whose emitted light is split into different colors, in particular primary colors, and then transferred to corresponding light valves. The light source system comprises a plurality of light sources, a plurality of reflectors for focusing the light beams of the light sources, and separating elements for splitting and interlacing the light from the light sources. Additional reflective means, preferably mirrors, are provided in the optical path between the light sources and the separating elements.

[0007] US 2011 / 0228 232 A1 concerns a projector of this type.

[0008] US 2013 / 0 271 954 A1 concerns another projection system in which a transmissive wavelength conversion element is included.

[0009] The present invention is based on the technical problem of providing a particularly advantageous multi-channel light source. Description of the invention

[0010] According to the invention, this problem is solved by a multi-channel light source according to independent claim 1. The multi-channel light source comprises, among other things, channels that can be individually modulated for imaging, comprising a pump radiation source for emitting pump radiation, a phosphor element with a phosphor for at least partially converting the pump radiation into conversion light, which phosphor element is arranged in a beam path of the pump radiation, a first and a second area light modulator for imaging, and a beam splitter, which is arranged downstream of the phosphor element such that useful light, which at least partially contains the conversion light, falls on the beam splitter, wherein the useful light has a first spectral component in a first spectral range and a second spectral component in a second spectral range different from the first, and the beam splitter is transmissive only in one of the two spectral ranges.However, in the other one it is reflective, so that the useful light is split downstream of the beam splitter into a first beam path with the first spectral component and a second beam path with the second spectral component, wherein the first area light modulator is arranged in the first beam path as the first channel and the second area light modulator is arranged in the second beam path as the second channel, so that several channels are available based on the useful light.

[0011] Preferred embodiments are found in the dependent claims and the present description, whereby a distinction is not always made in detail between a representation of the multi-channel light source and its use; in any case, the disclosure is to be read implicitly with regard to all claim categories.

[0012] According to the invention, the useful light, which is present downstream of the phosphor element at a given time, is not used for just one channel, but for at least two channels. These channels are thus supplied simultaneously by means of the useful light. For this purpose, the useful light is spectrally split by the beam splitter in such a way that the first and second beam paths are present downstream; the light in the beam paths differs in its respective spectral component.

[0013] A "channel" is defined as a beam path of light with specific spectral properties guided through a particular area light modulator; if, over time, light with different spectral properties is guided through the same area light modulator, this constitutes a different channel. Therefore, at any given time, there is one channel per area light modulator, as long as the area light modulator is supplied with light.

[0014] The useful light "contains" the conversion light at least partially; that is, at least one spectral range of the useful light should correspond to at least one spectral range of the conversion light (when considering spectral ranges with non-zero intensity). Put simply, the useful light can be solely the conversion light or a mixture of it with the pump radiation, which is the subject of the preferred embodiments. Since the advantages of the combination of features according to the invention are most clearly illustrated by referring to these two possibilities, details regarding the nature of the useful light will now be given priority over a discussion of the remaining main claim features.

[0015] In preferred embodiments, the useful light is identical to the conversion light, and the latter is broadband conversion light emitted by a broadband phosphor. Such a broadband phosphor can be more readily available or less expensive than a narrowband phosphor, for example. As an alternative to the present approach, the inventors considered filtering the broadband conversion light, which would have provided a single channel. By splitting the broadband conversion light instead of using it for just one channel, the spectral components are utilized more efficiently.

[0016] The useful light source can also be a mixture of unconverted pump radiation, preferably blue pump light, and conversion light. Adding conversion light can, for example, improve the color point; mixing it with cyan conversion light can, for instance, reduce the color temperature (making the light "warmer").

[0017] If, in the case of useful light consisting of pump radiation and conversion light, the pump radiation is assigned to one channel and the conversion light (for improving the color coordinates) to the other, the color coordinates can be adjusted. For example, the ratio of blue pump light to cyan conversion light, and thus the color temperature and / or the dominant wavelength, can be set. This adjustment can be achieved by changing the average ratio between the two channels over time.

[0018] Regardless of the specific composition of the useful light, the beam splitter is positioned within the beam path of the useful light. Part of the useful light is reflected, and another part is transmitted, resulting in a reflected and a transmitted beam path downstream of the beam splitter. If the beam splitter is, for example, a low-pass filter (also known as a long-pass filter), the long-wavelength spectral component is found in the transmitted beam path, and the short-wavelength spectral component in the reflected beam path; in the case of a high-pass filter (also known as a short-pass filter), this is exactly the opposite. One of the two beam paths (the "first"), equipped with the first area light modulator, then constitutes the first channel, and the other ("second") beam path, equipped with the second area light modulator, constitutes the second channel.

[0019] The multi-channel light source according to the invention can provide the first and second channels simultaneously; thus, a superimposed image does not, for example, only appear over time. This initially refers, of course, only to the channels separated by the beam splitter, which can preferably be supplemented with one or more further channels that can be applied simultaneously and / or sequentially. Furthermore, during operation, the first and second channels can be switched on for different durations via the area light modulators, for example, for adjustment purposes (see above).

[0020] In general, the light with the first spectral component and / or the light with the second spectral component can be spectrally modified downstream of the beam splitter and upstream of the respective area light modulator. For example, a wavelength range can be filtered out for spectral matching; a filter can therefore be arranged in the respective beam path between the beam splitter and the area light modulator. In this respect, spectral modification of one channel is possible independently of the other. Preferably, however, the light is not spectrally modified downstream of the beam splitter, which can also be advantageous for efficiency reasons.

[0021] In a preferred embodiment, the phosphor element can be a phosphor element moving through the beam path of the pump radiation, in particular a rotating phosphor element, such as a phosphor wheel or a phosphor roller. Although this can generally be advantageous for thermal reasons alone, a further (second) phosphor is then preferably provided in addition to the (first) phosphor whose useful light is split by the beam splitter. In general, the phosphors could, for example, also be arranged on different tracks; however, they preferably follow one another in segments with respect to rotation, so that the respective conversion light is present sequentially. A separate area light modulator can then be assigned to a channel that is provided in addition to the first and second channels; however, due to the sequential order, it can also be routed via the first and / or second area light modulator.

[0022] Typically, the phosphor emits the conversion light with a Lambertian emission characteristic; to direct the conversion light from the phosphor element, optics are preferably provided, which can be imaging or non-imaging, for example in the case of a Compound Parabolic Concentrator (CPC). Between the individual optical elements, i.e., for example, a collimation lens downstream of the pump radiation source, the beam splitter, the phosphor element, and the area light modulators, the radiation / light preferably passes through a gas volume, generally an inert gas, preferably air.

[0023] The conversion light is preferably of a longer wavelength than the pump radiation (down-conversion). "At least partial" conversion of the pump radiation into conversion light means that, for example, at least 10%, 20%, 30%, or 40% of the pump radiation incident on the phosphor element is converted, with the percentages being increasingly preferred in that order. In the case of full conversion, all of the incident pump radiation is converted.

[0024] Returning to the beam splitter, which is reflective in one of the two spectral ranges and transmissive in the other, "transmissive" means, for example, that at least 60%, preferably at least 70%, and more preferably at least 80% of the light in the corresponding spectral range is transmitted; "reflective" means, for example, that at least 60%, preferably at least 70%, and more preferably at least 80% of the light in the corresponding spectral range is reflected. These specifications refer specifically to the situation in the multi-channel light source, also because reflection and transmission can depend on the angle of incidence.

[0025] Preferably, the useful light falls at an angle within a range of 45° + / - 10°, more preferably + / -5°, particularly preferably + / -2°, on the beam splitter, wherein the angle between a surface normal at the point of incidence and the direction of incidence (which may optionally be formed as the center of gravity direction weighted according to the luminous flux) is considered.

[0026] The beam splitter is preferably an interference mirror (also called a "dichroic mirror"), for example a multilayer system composed of at least two dielectric layer materials that differ in their refractive indices, wherein the layer materials are arranged alternately. A first layer material can be, for example, silicon dioxide and a second, for example, titanium dioxide. According to the invention, the beam splitter can be designed as a high-pass or low-pass filter, i.e., with exactly one cutoff wavelength. According to the invention, the beam splitter is designed as a band-pass or band-stop filter with two cutoff wavelengths. In its passband, the beam splitter transmits; in its stopband, it reflects.The beam splitter generally does not need to be statically arranged, but can, for example in the case of a rotating phosphor element, rotate synchronously with it, so that different reflection / transmission properties can be set depending on the segment (in adaptation to the phosphor of the respective segment).

[0027] The pump radiation source is preferably a laser source, including an array of several laser sources. Laser sources of different wavelengths can be combined; however, the laser sources in the array preferably have the same wavelength, and are particularly preferably identical in construction. A laser diode is preferred as the laser source. The pump radiation is preferably blue pump light, for example with a dominant wavelength of 405 nm or 450 nm.

[0028] As already mentioned, in preferred embodiments the phosphor is a broadband phosphor, and the broadband conversion light is split by the beam splitter. The "broadband conversion light" can, for example, have a spectral intensity distribution which, over a wavelength range of at least 50 nm, preferably at least 100 nm, and more preferably at least 150 nm, exhibits an intensity that is at least 10%, preferably at least 20%, and more preferably at least 30% of a maximum intensity value in the visible spectral range (between 380 nm and 780 nm).

[0029] By definition, the first and second spectral ranges should border each other at a cutoff wavelength, with one range extending over wavelengths smaller and the other over wavelengths larger than the cutoff wavelength. Downstream of the beam splitter, however, the light in each (first or second) beam path can also have a certain intensity outside its respective spectral range, i.e., in the spectral range divided between the other beam path.

[0030] One reason for this could be the technical limitations of the beam splitter, which does not necessarily cut off sharply at the cutoff wavelength. However, the intensity in the respective other spectral range—that is, in the second spectral range in the case of the first beam path and in the first spectral range in the case of the second beam path—should, for example, be at most 30%, preferably at most 20%, and more preferably at most 10% of the intensity of the useful light upstream of the beam splitter in that spectral range. In the respective spectral range (the first spectral range in the case of the first beam path and the second in the case of the second), the intensity upstream of the beam splitter should be, for example, at least 70%, preferably at least 80%, and more preferably at least 90% of the intensity of the useful light in that corresponding spectral range.

[0031] In a preferred embodiment, the broadband conversion light is yellow light, the dominant wavelength of which can be, for example, at least 572.5 nm, preferably at least 575 nm, and, for example, at most 585 nm, preferably at most 582.5 nm, and more preferably at most 580 nm (the upper and lower limits can also be of interest independently of each other). The yellow light is then preferably split by the beam splitter into green light in the first beam path and red light in the second beam path. The dominant wavelength of the green light can, for example, be at least 520 nm, preferably at least 530 nm, and more preferably at least 535 nm, and at most 570 nm, preferably at most 565 nm, and more preferably at most 560 nm (again, the upper and lower limits can be of interest independently of each other).The dominant wavelength of the red light can be, for example, at least 590 nm, preferably at least 595 nm.

[0032] In general, the term "phosphor" in this disclosure does not necessarily refer to a single phosphor (of a specific chemical composition), but may also refer to a mixture of several single phosphors; however, "phosphor" preferably refers to a single phosphor.

[0033] A garnet phosphor, such as yttrium aluminum garnet (YAG) or lutetium aluminum garnet (LuAG), each doped with cerium, may be preferred as a single phosphor. YAG:Ce and LuAG:Ce are single phosphors which, as described above, may also be used in mixtures, but are preferably alternatives.

[0034] As mentioned earlier, the useful light can also be a mixture of the conversion light and the pump radiation. In this case, not all of the pump radiation is converted, and the unconverted portion is used as part of the useful light. Only a portion of the pump radiation is converted into conversion light by the phosphor, for example, no more than 80% or 70%, with possible lower limits being at least 20% or 30%, respectively (and the upper and lower limits can also be of interest independently of each other). This refers to a specific phosphor, generally as a time average; preferably, however, a corresponding ratio exists at every point in time as long as the phosphor is excited. The phosphor can therefore be, for example, uniformly thin and thus partially transmissive, or provided with a multitude of small pores (through which the pump radiation, unconverted at the same time, passes).

[0035] According to the invention, the relevant useful light (containing a component of pump radiation) is then split by the beam splitter in such a way that, downstream of the beam splitter, the pump radiation is found in the first beam path and the conversion light in the second beam path. In other words, the pump radiation is located in the first spectral range and the conversion light in the second spectral range.

[0036] In a preferred embodiment, the conversion light mixed with the pump radiation is cyan light with a dominant wavelength of, for example, at least 490 nm, preferably at least 500 nm, and, for example, at most 530 nm, preferably at most 520 nm (the upper and lower limits can also be of interest independently of each other). Although, in general, for example, a blue phosphor can also be provided for the blue channel and operated in full conversion, blue pump light is preferably used as the blue channel. Its color coordinates can be improved by mixing in the cyan light, i.e., with the cyan channel.

[0037] In a preferred embodiment, manganese-activated ZnSiO (Mn:ZnSiO) or europium-doped nitridorthosilicate (Eu:NOS) or europium-doped SiON (Eu:SiON) is provided as the single phosphor emitting the cyan-colored conversion light.

[0038] The pump radiation strikes a pump radiation input side of the phosphor element, and the conversion light is emitted from it at a conversion light emission side. In the case of reflective operation, the pump radiation input side and the conversion light emission side coincide; in transmission operation, they are opposite each other. To increase efficiency, and thus allow more conversion light to be emitted, the side of the phosphor element opposite the conversion light emission side can be reflectively mirrored for the conversion light; in the case of transmission operation, it can be dichroic, i.e., transmissive for the pump radiation. In a phosphor element operating in reflective mode, a fully mirrored surface and / or a heat sink can also be provided on this rear side.

[0039] Transmission operation may be preferable, particularly in the case of partial conversion. Generally, the multi-channel light source can be used for reflection operation ( Fig. 1) or transmission ( Fig. 3) be set up, but a combination is also possible ( Fig. 2), the light can therefore be directed through some of the channels in transmission and through other parts of the channels in reflection.

[0040] In a preferred embodiment, at least one of the area light modulators is a digital micromirror device (DMD) array or a liquid crystal-based imager, for example an LCD (liquid crystal display) or LCoS (liquid crystal on silicon) imager, wherein the LCD imager operates in transmission mode and the LCoS imager operates in reflection mode. Preferably, the first and second imagers are two separate components of the same type (DMD, LCD, or LCoS); more preferably, they are identical in construction.

[0041] Generally, a "surface light modulator" refers to a component with a modulation surface subdivided into pixels; an image can be superimposed onto a beam of light falling on the modulation surface by either transmitting the signal to a specific pixel or not, thus allowing individual pixels to be switched on and off. This "transmission" can occur through reflection or transmission to a subsequent (projection) optical system.

[0042] Although the separation of broadband conversion light and the separation of conversion light mixed with pump radiation have so far been described as two separate concepts, these can, of course, be integrated together into a multi-channel light source. According to the invention, a first phosphor is provided for emitting broadband conversion light, and a second phosphor is provided for emitting a second conversion light, which, when mixed with the pump radiation, constitutes a second useful light. Preferably, the broadband conversion light (first useful light) and the second useful light are present sequentially during operation; for example, the first and second phosphors are arranged on a rotating phosphor element as described herein.

[0043] In a multi-channel light source with first and second useful light sources (not according to the invention), the beam splitter is configured as a high-pass or low-pass filter. The first useful light is directed onto the beam splitter from one side, and the second useful light from the opposite side. The useful light falls onto the beam splitter in such a way that, downstream, the reflected portion of the first useful light lies in a beam path with the transmitted portion of the second useful light, and / or the transmitted portion of the first useful light lies in a beam path with the reflected portion of the second useful light.

[0044] The beam splitter then separates the broadband conversion light (first useful light) into a short-wavelength and a long-wavelength spectral component. If the second useful light were directed to the beam splitter from the same side, the path taken by at least its short-wavelength component (the pump light) would be the same; thus, the short-wavelength, and therefore higher-energy, components of both the first and second useful light would be assigned to the same area light modulator (at least over time). However, by directing the useful light onto opposite sides of the beam splitter, the path distribution is exactly reversed, and the long-wavelength spectral component of the first useful light is combined with the short-wavelength spectral component of the second useful light, preferably with the entire second useful light.

[0045] For example, yellow light can fall on one side as the first useful light and a mixture of cyan conversion light with blue pump light on the opposite side, whereby the red spectral component of the yellow light is then combined with the second useful light downstream of the beam splitter; the green spectral component of the yellow useful light is found in the other beam path.

[0046] According to the invention, the beam splitter is configured as a bandpass or bandstop filter, with the first and second useful light sources incident on the same side of it, preferably from the same direction and at the same point. Regardless of whether it is a bandpass or bandstop filter, the beam splitter in this case has two cutoff wavelengths, one of which lies in the spectrum of the first useful light source and the other in the spectrum of the second useful light source. At its two cutoff wavelengths, the beam splitter exhibits exactly inverse behavior; for example, in the case of a bandpass filter, it is transmissive above the lower cutoff wavelength and reflective above the upper cutoff wavelength, and vice versa in the case of a bandstop filter.

[0047] As a result, downstream of the beam splitter, a short-wavelength spectral component of the first useful light is combined with a long-wavelength component of the second useful light in one beam path, and a long-wavelength spectral component of the first useful light is combined with a short-wavelength component of the second useful light in the other beam path.

[0048] In the case of the yellow primary light and the mixture of cyan conversion light and blue pump light as the secondary light, the green component of the primary light is combined with the cyan conversion light in one beam path, and the red component of the primary light is combined with the pump light in the other beam path. As with the previously described embodiment, this allows, for example, the thermal stress on the components in the individual beam paths to be at least somewhat homogenized.

[0049] The invention also relates to a set of multiple multi-channel light sources, the respective useful light (optionally also first and second useful light) of which has the same spectral properties from one multi-channel light source to the next. However, the multi-channel light sources of the set differ in their respective beam splitters, each with a different cutoff wavelength, so that the multi-channel light sources differ accordingly in their respective division between the first and second spectral ranges.

[0050] The invention also relates to the use of a multi-channel light source disclosed herein for imaging, preferably as an imaging component in a projection device. Preferably, the first and second channels are used simultaneously. Further advantageous applications may lie in the field of lighting; the multi-channel light source can thus be part of a headlight, for example in the field of stage or effect lighting, or also in the automotive sector. In an application in the automotive sector, the channels can, for example, be assigned to paths with different white light (different color coordinates); thus, for example, white light adjustment may also be possible, for example within an ECE-standardized field, i.e., a sub-area in the standard color chart (ECE, Economic Commission for Europe). Brief description of the drawings

[0051] The invention will be explained in more detail below using exemplary embodiments, whereby no distinction will be made in detail between the claim categories and the individual features within the scope of the dependent claims may also be essential to the invention in other combinations.

[0052] In detail: Fig. 1 a multi-channel light source according to the invention with two simultaneously output channels; Fig. 2 a multi-channel light source according to the invention, with two simultaneously output channels and a further channel output sequentially thereto; Fig. 3 a multi-channel light source according to the invention for outputting four channels, wherein in this case the phosphor element is operated exclusively in transmission. Preferred embodiment of the invention

[0053] Fig. Figure 1 shows a multi-channel light source 1 according to the invention, comprising a pump radiation source 2 and a phosphor element 3. The pump radiation emitted by the pump radiation source 2 is blue laser light with a wavelength of 450 nm. The beam path 4 of the pump radiation passes through a dichroic mirror 5 and, downstream of it, strikes the phosphor element 3. This element is made of a YAG:Ce phosphor and emits yellow conversion light upon excitation. In this case, the phosphor element 3 is static.

[0054] For the sake of clarity, the beam paths (pump radiation and conversion / useful light) are simplified in the present figures, as the divergence / focusing of the light is neglected and, accordingly, no lenses or light guides are shown. In reality, for example, a collimation lens would be provided immediately downstream of the pump radiation source 2, which collimates the slightly divergent pump radiation. A lens positioned upstream of the phosphor element 3 would, for example, focus the pump radiation onto the phosphor element 3, and the same lens could then be used to collimate the divergent conversion light.

[0055] The phosphor element 3 emits conversion light upon excitation with the pump radiation, which is directed away at the pump radiation input side 7 of the phosphor element 3 in a beam path 6 (operation in reflection). The phosphor element 3 can be provided with a mirror / heat sink (not shown) on its rear side.

[0056] The dichroic mirror 5 is reflective to the yellow conversion light and thus decouples it from the beam path 4 of the pump radiation. Downstream of the dichroic mirror 5 is a beam splitter 8, also a dichroic mirror, specifically a low-pass filter. The beam splitter 8 therefore transmits long-wavelength light and reflects shorter-wavelength light. The yellow conversion light is broadband conversion light, which has spectral components in the red and green ranges.

[0057] The broadband conversion light is split by the beam splitter 8 into a first beam path 10 containing the green component and a second beam path 11 containing the red component of the broadband conversion light. A first area light modulator 12 is arranged in the first beam path 10, and a second area light modulator 13 is arranged in the second beam path 11. In this case, each is a DMD array, with which an image can be modulated onto the respective beam path 10, 11. The second beam path 11 falls directly onto the second area light modulator 13 downstream of the beam splitter 8, while the first beam path 10 is guided via a mirror 14 (fully reflective).

[0058] Each area light modulator 12, 13 provides one channel. The multi-channel light source 1 according to Fig. In the next step, the two channels are combined, i.e., superimposed, and passed through the projection optics of a projection device. In this case, a blue channel, for example, can be routed separately via its own area light modulator and superimposed with the two channels (red and green).

[0059] Fig. Figure 2 shows a multi-channel light source 1, in which the blue channel is already integrated. The green and red channels of the multi-channel light source 1 according to Fig. 2 are analogous to the multi-channel light source 1 according to Fig. 1 provided. Upon excitation with the blue pump light, the phosphor element 3 emits yellow broadband conversion light, the beam path 6 of which is decoupled from the beam path 4 of the pump radiation by the dichroic mirror 5 ( Fig. 2a). The yellow broadband conversion light falls on the beam splitter 8 (also a low-pass filter), which reflects the green component of the broadband conversion light into the first beam path 10 to the first area light modulator 12, but transmits the red component into the second beam path 11 to the second area light modulator 13 ( Fig. 2a).

[0060] In the case of the multi-channel light source 1, the fluorescent element 3 is according to Fig. However, 2 is not static, but rather designed as a rotating fluorescent wheel. The YAG:Ce phosphor is also only present in segments, alternating with a blue segment. In the simplest case, the fluorescent wheel could have a through-opening in the blue segment, allowing the pump light to pass through the fluorescent element 3 without interaction and be used for the blue channel. The blue channel and the yellow broadband conversion light (i.e., the green and red channels) are then present sequentially.

[0061] In this design, the phosphor element 3 in the blue channel segment is not completely transparent; instead, a thin layer of a cyan phosphor (manganese-activated ZnSiO₂) is provided. A portion of the blue pump light is converted by this phosphor to cyan conversion light. The mixture of unconverted blue pump light and cyan conversion light is referred to as the second useful light, with the yellow broadband conversion light being the first useful light.

[0062] Fig. Figure 2a shows a first time point t1 at which a segment is excited with YAG:Ce, and Fig. 2b a second time t2, at which the blue segment is excited. In the blue segment, the phosphor element 3 is operated in transmission mode, meaning that the second useful light is emitted from a conversion light emission side 21 opposite the pump radiation input side 7. The second useful light is also directed onto the beam splitter 8, for which purpose two mirrors 22 are arranged in the beam path 23 of the second useful light.

[0063] Compared to the first useful light ( Fig. 2a) The second useful light is directed to the opposite side of the beam splitter ( Fig. 2b). Since the beam splitter 8 is a low-pass filter, it is reflective for the second useful light. The second useful light is reflected into the second beam path 11, i.e., into the same beam path as the red component of the first useful light (and thus to the second area light modulator 13). Therefore, the green component of the first useful light and the second useful light (mixture of pump light and cyan conversion light) are assigned to different area light modulators 12, 13.

[0064] The multi-channel light source 1 according to Fig. 3 provides four channels: red and green simultaneously, and blue and cyan sequentially. Fluorescent element 3 is therefore again a fluorescent wheel divided into segments, and during operation it emits yellow broadband conversion light and, sequentially, a mixture of blue pump light and cyan conversion light.

[0065] The phosphor element 3 is now also operated in transmission mode in the case of the yellow broadband conversion light; the broadband conversion light is thus emitted from a conversion light emission side 21 opposite the pump radiation input side 7. To increase efficiency, the phosphor element 3 can be dichroic mirrored on the pump radiation input side 7, so that the pump light is transmitted, while the conversion light, which would otherwise also be emitted from the pump radiation input side 7, is reflected to the conversion light emission side 21 (this is also the case for the blue channel of the embodiment according to Fig. 2 possible).

[0066] Unlike previous embodiments, the beam splitter 8 is not designed as a low-pass filter (i.e., with only one cutoff wavelength), but as a band-pass filter. The beam splitter 8 is therefore reflective below a lower cutoff wavelength, transmissive above this and below an upper cutoff wavelength (i.e., between the cutoff wavelengths), and then reflective again above the upper cutoff wavelength.

[0067] If yellow broadband conversion light falls on the beam splitter 8 only at a first time t1, the green component is transmitted into the first beam path 10 and the red component is reflected into the second beam path 11. The green component falls on the first area light modulator 12, and the red component on the second area light modulator 13. In this case, the upper cutoff wavelength (which lies at lower energies) separates the beams, so the beam splitter 8 acts as a high-pass filter.

[0068] When the blue channel is sequentially applied, a mixture of the blue pump light and the cyan conversion light falls on the beam splitter 10. The lower cutoff wavelength, which occurs at higher energies, lies in this range, and the beam splitter acts as a low-pass filter. The cyan conversion light is thus transmitted into the first beam path 10 and falls on the first area light modulator 12. The blue pump light is reflected into the second beam path 11 and falls on the second area light modulator 13. Again, the green and blue light are assigned to different beam paths 10 and 11.

Claims

[1] Multi-channel light source (1) with channels that can be individually modulated for imaging, comprising: a pump radiation source (2) for the emission of pump radiation, a phosphor element (3) with a phosphor for at least partial conversion of the pump radiation into conversion light, which phosphor element is arranged in a beam path (4) of the pump radiation, a first (12) and a second area light modulator (13) for imaging and a beam splitter (8) which is arranged downstream of the phosphor element (3) such that a useful light, which contains at least part of the conversion light, falls on the beam splitter (8), wherein the useful light has a first spectral component in a first spectral range and a second spectral component in a different second spectral range and the beam splitter (8) is transmissive only in one of the two spectral ranges, but reflective in the other, so that the useful light is split downstream of the beam splitter (8) into a first beam path (10) with the first spectral component and a second beam path (11) with the second spectral component, wherein in the first beam path (10) the first area light modulator (12) is arranged as the first channel and in the second beam path (11) the second area light modulator (13) is arranged as the second channel, so that several channels are available based on the useful light, wherein the phosphor element (3) is operated in transmission, i.e. the pump radiation falls on a pump radiation input side of the phosphor element (3) which is opposite a conversion light emission side of the phosphor element (3) and the conversion light is emitted from the conversion light emission side of the phosphor element (3), where the pump radiation is only partially converted and the useful light is a mixture of the pump radiation and the conversion light, wherein the useful light is split downstream of the beam splitter (8) into the pump radiation in the first beam path and the conversion light in the second beam path, characterized by , that the phosphor element (3) comprises a first phosphor for emitting the broadband conversion light as a first conversion light and a second phosphor for emitting a second conversion light, wherein the broad-spectrum conversion light is a first useful light and the mixture of the pump radiation and the second conversion light is a second useful light, wherein the beam splitter (8) is provided as a bandpass or bandstop filter, wherein the first and the second useful light fall on the same side of the beam splitter (8) and downstream of the beam splitter (8) a short-wavelength spectral component of the first useful light is combined with a long-wavelength spectral component of the second useful light in the first beam path (10) and a long-wavelength spectral component of the first useful light is combined with a short-wavelength spectral component of the second useful light in the second beam path (11). [2] Multi-channel light source (1) according to claim 1, in which the phosphor is a broadband phosphor and the useful light is conversion light emitted therefrom with a broad spectrum, which is split downstream of the beam splitter (8) into the first beam path (10) and the second beam path (11). [3] Multi-channel light source (1) according to claim 2, wherein the conversion light is yellow light with a broad spectrum, wherein the split useful light in the first beam path (10) is green light and the split useful light in the second beam path (11) is red light. [4] Multi-channel light source (1) according to claim 3, wherein the broadband phosphor is a garnet phosphor. [5] Multi-channel light source (1) according to claim 1, wherein the conversion light is cyan light. [6] Multi-channel light source (1) according to claim 5, wherein the phosphor comprises at least one of Mn:ZnSiO, Eu:NOS and Eu:SiON. [7] Multi-channel light source (1) according to one of the preceding claims, wherein at least one of the first (12) and the second area light modulator (13) is a micromirror array or a liquid crystal-based imager. [8] Set of multiple multi-channel light sources (1) according to one of the preceding claims, wherein the useful light has the same spectral properties in each of the multi-channel light sources (1), but the multi-channel light sources (1) differ in their respective beam splitter (8), so that the multi-channel light sources (1) differ in the first and the second spectral range. [9] Use of a multi-channel light source (1) according to any one of claims 1 to 7 or of a set of multi-channel light sources (1) according to claim 8 for imaging, wherein preferably the first and the second channel are used simultaneously.

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