Multispectral light source and method

Abstract

The invention relates to a multispectral light source (10) for producing an output radiation (12), said multispectral light source comprising: - a first light source (14), wherein a first light beam (16) having a first wavelength (λ1) can be emitted from the first light source (14), - a second light source (18), wherein a second light beam (20) having a second wavelength (λ2) can be emitted from the second light source (18), - a third light source (22), wherein a third light beam (24), which has a wavelength range of λ3min to λ3max, can be emitted from the third light source (22), wherein the first light source (14), the second light source (18), and the third light source (22) are arranged at a distance from one another, - at least one first dichroic mirror (32) for combining the first light beam (16) and the second light beam (20) into a fourth light beam (76), wherein the first dichroic mirror (32) is designed to reflect the second light beam (20) and transmit the first light beam (16), and wherein the first dichroic mirror (32) is arranged in such a way that the second light beam (20) can be reflected by the first dichroic mirror (32) and the first light beam (16) can be transmitted by the first dichroic mirror (32), and - a beam splitter (34) positioned downstream of the first dichroic mirror (32), wherein the beam splitter (34) is designed to divide the fourth light beam (76), formed from the first light beam (16) and the second light beam (20), into a first power component (36) and a second power component (37), and to divide the third light beam (24) into a third power component (38) and a fourth power component (39), wherein the first power component (36) can be superimposed on the fourth power component (39) by the beam splitter (34) in order to form the output radiation (12), and the second power component (37), together with the third power component (38), can be output as a residual radiation (86) or an additional output radiation (86).

Description

[0001] Multispectral light source and method

[0002] The invention relates to a multispectral light source for generating an output radiation with a plurality of color channels having the features of independent patent claim 1 and to a method for generating a multispectral output radiation having the features of independent patent claim 11.

[0003] EP 3 193 503 A1 discloses an illumination system with three wavelength bands (color channels). Two wavelength bands share the same beam path and are alternately activated by a rotating disk containing two different phosphor agents. This has the disadvantage that setting a specific coordinate in the color space or white balance is difficult to achieve.

[0004] A laser phosphor projector is known from EP 3 409 011 A1. The disadvantage is its complicated design.

[0005] US Pat. No. 8,608,329 A1 discloses an illumination system with a rotating disk containing phosphor agents. The disadvantage is the use of rotating parts in the beam path.

[0006] EP 2 530 520 A1 discloses an optical illumination system with a single primary light source. This has the disadvantage that setting a specific coordinate in the color space or white balance is difficult to achieve.

[0007] RU 51 734 U1 discloses a light source in which the light from three light-emitting diodes is superimposed by two dichroic mirrors. The achievable color rendering index may be too low for demanding applications.

[0008] EP 1 024 539 A2 discloses a solid-state light source with dichroic reflectors. The achievable color rendering index may be too low for applications with high requirements.

[0009] US 2018 / 0210213 A1 discloses a multispectral laser projector comprising three laser light sources with different wavelengths, a first beam splitter that combines the radiation from the first two light sources, and a second beam splitter that splits the radiation from the third light source and combines a partial beam thereof with the combined radiation from the first and second light sources to form an output beam. A disadvantage is that the achievable color rendering index is rather low.

[0010] US 2012 / 0307514 A1 discloses a multispectral light source comprising three light-emitting diodes with different wavelengths and two dichroic mirrors, with which a common output beam is generated. In this case, the achievable color rendering index may be too low for applications with high requirements. CN 1 11399241 A discloses another multispectral light source comprising three light sources with different wavelengths, as well as a narrowband, i.e., wavelength-dependent, polarization beam splitter and a dichroic mirror, with which a common output beam is generated. In this case, the achievable color rendering index may also be too low for applications with high requirements. Furthermore, the polarization beam splitter used may be expensive.

[0011] It is therefore an object of the present invention to at least partially overcome at least one of the disadvantages described above. In particular, the object of the invention is to provide a simple light source for generating multispectral output radiation with a high power density.

[0012] The above object is achieved by a multispectral light source having the features of independent patent claim 1 and by a method having the features of independent patent claim 11. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the multispectral light source according to the invention naturally also apply in connection with the method according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0013] A first aspect of the invention is a multispectral light source for generating output radiation. The output radiation is a visible light beam. This can comprise several, preferably at least three, spectral components. The spectral components can each have different peak wavelengths and / or centroid wavelengths. The individual spectral components can be generated using color channels, i.e., using components of different wavelengths. A color channel can be referred to as the part of the multispectral light source with which a respective spectral component of the output radiation is generated.

[0014] For this purpose, the multispectral light source comprises: a first light source, wherein a first light beam having a first wavelength can be emitted from the first light source; a second light source, wherein a second light beam having a second wavelength can be emitted from the second light source; and a third light source, wherein a third light beam having a wavelength range A3min to A3max can be emitted from the third light source. The third light beam has a peak wavelength A3.

[0015] The wavelengths can each be determined as peak wavelengths. The first and second light beams can be narrowband, for example, with a spectral width, which can be determined as the full width at half maximum (FWHM), of less than 100 nm, preferably less than 50 nm. A narrowband light source can also be referred to as monochrome. The third light beam can be broadband, for example, with a spectral width (full width at half maximum) of more than 100 nm, preferably more than 200 nm. This can be white light, for example, warm white, neutral white, or cool white.

[0016] A bundle of light rays, also known as a light beam bundle, is defined as a light beam. This beam can be partially divergent or convergent, or parallel (collimated) in a beam path. A bundle of light rays can have a central ray, which can represent the main direction of the beam.

[0017] The first light source (first color channel), the second light source (second color channel), and the third light source (third color channel) are arranged at a distance from one another. These can therefore be individual light sources. A first beam path of the first light beam, a second beam path of the second light beam, and a third beam path of the third light beam can differ from one another in their paths, at least in sections.

[0018] In addition, the multispectral light source comprises at least one first dichroic mirror for combining the first and second light beams to form a fourth light beam. The fourth light beam can propagate in a direction z, as the direction of the central ray of the fourth light beam. For this purpose, the first dichroic mirror is designed to reflect the second light beam and transmit the first light beam. The second light beam can be incident on the first dichroic mirror in a direction y perpendicular to the direction z. The first dichroic mirror can therefore be arranged in the first beam path and the second beam path such that the second light beam can be reflected by the first dichroic mirror and the first light beam can be transmitted by the first dichroic mirror.The fourth light beam can thus be formed from the transmitted first light beam and the reflected second light beam by spatially superimposing them. Due to the dichroic design of the mirror, the first and second light beams can be superimposed with virtually no loss. This can mean that the fourth light beam contains more than 90%, advantageously more than 95%, of the first and second light beams.

[0019] The first dichroic mirror can be designed as a cube with an interior flat mirror layer. In this case, the mirror layer can be delimited by two parallel surface diagonals and two edges of the cube. However, the first dichroic mirror can also be designed as a plate-shaped mirror having a mirror layer. The plate-shaped mirror can be arranged at an angle of 45° to the first light beam and at an angle of 135° to the second light beam. The first and second light beams can be arranged perpendicular to each other with respect to their central rays. The mirror normal can lie in the plane spanned by the central rays of the first and second light beams, and the plate plane or the mirror layer plane can form an angle bisector of these two central rays.The mirror layer of the first dichroic mirror can be formed, for example, as a dichroic dielectric coating.

[0020] Furthermore, a beam splitter is provided downstream of the first dichroic mirror. The beam splitter can be designed as a beam splitter cube with an internal planar mirror layer. In this case, the mirror layer can be defined by two parallel surface diagonals and two edges of the cube. However, the beam splitter can also be designed as a plate-shaped mirror having a mirror layer. The plate-shaped mirror can be arranged at an angle of 45° to the fourth light beam and at an angle of 135° to the third light beam. The third and fourth light beams can be arranged perpendicular to each other with respect to their central rays. The mirror normal can lie in the plane spanned by the central rays of the third and fourth light beams, and the plate plane can form an angle bisector of these two central rays.The mirror layer of the beam splitter can be formed, for example, as a dielectric coating. Alternatively, the mirror layer of the beam splitter can be formed as a thin metal layer, which is, for example, semi-transparent to the incident light. The beam splitter can be non-polarizing, i.e., with a polarization-independent splitting ratio.

[0021] The beam splitter is designed to split the fourth light beam formed from the first light beam and the second light beam into a first power component and a second power component and to split the third light beam into a third power component and a fourth power component.

[0022] The beam splitter also allows the first power component to be superimposed on the fourth power component to form the output radiation. The output radiation can thus be understood as a spatial superposition of the first and fourth power components. The second power component, together with the third power component, can be output as residual radiation or further output radiation. The residual radiation can be discarded, for example, using an absorber or other beam trap if it is not needed. The second and third power components together can have the same radiant power as the first and fourth power components combined.

[0023] Spatial superposition means that the superimposed beams of rays are located at the same point (location) and have the same direction of propagation.

[0024] The fourth light beam can be incident on the beam splitter in the z direction. The third light beam can be incident on the beam splitter in the y direction. The first power component and the fourth power component can leave the beam splitter in the z direction. The second power component and the third power component can leave the beam splitter in the y direction. In a further embodiment, for the aforementioned directions of incidence, the first power component and the fourth power component can leave the beam splitter in the y direction, and the second power component and the third power component can leave the beam splitter in the z direction.

[0025] By means of the beam splitter, the power components of the fourth light beam formed from the first and second light beams and the power components of the third light beam can be divisible, or reflected and transmitted, regardless of wavelength, subject to a tolerance of the beam splitter. Therefore, the beam splitter can be understood as non-dichroic within the meaning of the present invention. The output radiation can be formed from the portion of the fourth beam transmitted through the beam splitter (first power component) and the portion of the third beam reflected by the beam splitter (fourth power component). The output radiation can also be formed from the portion of the third beam transmitted through the beam splitter (fourth power component) and the portion of the fourth beam reflected by the beam splitter (first power component).This depends on the positioning of the beam splitter in the beam paths of the multispectral light source.

[0026] Because the beam splitter essentially splits the power components of the first, second, and third light beams independently of wavelength, an output beam with a homogeneous power across the spectral range of the light beam can be generated, free of spectral power peaks, and thus with particularly good color rendering. This can be a continuous power spectrum with respect to the wavelength. This allows the white balance of the light source to be optimized, allowing the homogeneous output beam to be generated.

[0027] The beam splitter is thus designed to generate a useful beam, i.e., the output radiation, and a residual beam. The residual beam can be discarded if only one output radiation is required. In a further embodiment, the residual beam can be utilized and thus represent a second output radiation. In this invention, the residual radiation can inevitably arise due to the wavelength-independent splitting ratio of the beam splitter. The advantage of perfect color rendering of the multispectral light source can be associated with the disadvantage that a portion of the generated light must be discarded as residual radiation. Ideally, the output radiation can contain a luminous efficacy of 50% of the first, second, and third light beams generated by the light sources.Due to the arrangement according to the invention and due to technical losses, the luminous efficacy of the output radiation can be 30% to 50% of the first, second and third light beam bundles combined.

[0028] Using the multispectral light source, white light radiation with a high color rendering index can now be generated. A color rendering index of Rf>92 can be achieved. The color rendering index can be determined according to the IES TM 30-18 standard.

[0029] It is particularly advantageous if the first beam path of the first light beam and the second beam path of the second light beam have a common first beam section between the first dichroic mirror and the beam splitter, wherein the first beam section has a first direction, for example the z direction. The fourth light beam can be understood as this first beam section. This means that the first beam path of the first light beam and the second beam path of the second light beam can be arranged so as to be spatially superimposed. Furthermore, the third light beam can be guided to the beam splitter on the third beam path in a second direction, for example the y direction, wherein the second direction differs from the first direction, in particular by 90°.

[0030] Within the scope of the invention, it may be advantageous to provide a second mirror, wherein the second mirror is designed to reflect the first light beam, and wherein the second mirror is arranged in the first beam path such that the first light beam can be reflected by the second mirror before it strikes the first dichroic mirror. The reflection can advantageously occur at a right angle.

[0031] The second mirror allows for a free choice of the arrangement of the first light source for generating the first light beam, as it now allows for redirection of the first light beam through reflection. This increases the flexibility of the arrangement of the individual light sources, allowing for a more flexible design of the installation space for the multispectral light source without sacrificing the ability to generate homogeneous output radiation with a high power density.

[0032] Within the scope of the invention, it is conceivable that the first light source for providing the first light beam has a first luminous element and a first converter element, wherein a first primary light can be emitted from the first luminous element, and wherein the first light beam can be emitted from the first converter element by irradiation with the first primary light, wherein the second dichroic mirror is arranged in the first beam path between the first luminous element and the first converter element in such a way that the first primary light can be transmitted through the second mirror and the first light beam can be reflected by the second mirror. For this purpose, the second mirror can be dichroic, ie for example transmissive for the wavelength of the primary light and reflective for the first light beam.

[0033] The first converter element can be fluorescent and / or phosphorescent. The first converter element can be a wavelength converter, which can also be referred to as a phosphor. Phosphors are usually designed such that the primary wavelength of the first primary light is shorter than the respective secondary wavelength of the first light beam. However, they can also be up-conversion elements, which can convert a longer primary wavelength to shorter wavelengths, for example through multi-photon processes. The first light beam emitted by the converter element can have a short coherence length of less than 1 mm and a spectral bandwidth (FWHM) of more than 30 nm.It can be provided within the scope of the invention that the second light source for providing the second light beam has a second luminous body and a second converter element, wherein a second primary light can be emitted from the second luminous body, and wherein the second light beam can be emitted from the second converter element by irradiation with the second primary light, wherein the first dichroic mirror is arranged in the second beam path between the second luminous body and the second converter element such that the second primary light can be transmitted and the second light beam can be reflected.

[0034] The second converter element can also be fluorescent and / or phosphorescent. The second converter element can be a wavelength converter, which can also be referred to as a phosphor. Phosphors are usually designed such that the primary wavelength of the second primary light is shorter than the respective secondary wavelength of the second light beam. However, they can also be up-conversion elements, which can convert a longer primary wavelength to shorter wavelengths, for example through multi-photon processes. The second light beam emitted by the photoluminescent bodies can have a short coherence length of less than 1 mm and a spectral bandwidth (FWHM) of more than 30 nm.

[0035] It is further conceivable that the third light source for providing the third light beam comprises a third luminous body, a third converter element and a third dichroic mirror, wherein a third primary light can be emitted from the third luminous body, and wherein the third light beam can be emitted from the third converter element by irradiation with the third primary light, wherein the third dichroic mirror is arranged between the beam splitter and the third converter element such that the third primary light can be reflected and the third light beam can be transmitted.

[0036] The third converter element can also be fluorescent and / or phosphorescent. The third converter element can be a wavelength converter, which can also be referred to as a phosphor. Phosphors are usually designed such that the primary wavelength of the third primary light is shorter than the respective secondary wavelength of the third light beam. However, they can also be up-conversion elements, which can, for example, convert a longer primary wavelength to shorter wavelengths through multi-photon processes. The third light beam emitted by the photoluminescent bodies can have a short coherence length of less than 1 mm and a spectral bandwidth (FWHM) of more than 30 nm.

[0037] In particular, if a first, second, and / or third converter element is provided, it may be advantageous to design the associated first, second, and / or third primary light source for generating the respective primary light as a laser diode. It is also conceivable to provide a wavelength filter between the third light source, in particular a broadband third light source, and the beam splitter, wherein the wavelength filter is designed to filter a predetermined wavelength from the third light beam.

[0038] These wavelength filters can be used when the wavelength range A3min to A3max of the third light source covers a very large range; the wavelength filter can then filter out spectral components that are not required to generate the output radiation or are already covered by the first light beam or the second light beam.

[0039] In particular, the third light source may have an excessive peak in the blue wavelength range, which can then be eliminated by the filter. The wavelength filter may advantageously be a blue filter. This may be a blue light blocking filter.

[0040] The filter can be formed by means of dielectric interference layers and / or as an optical color filter made of colored glass.

[0041] Within the scope of the invention, it is optionally possible for the first dichroic mirror and / or the second dichroic mirror to be designed as a short-pass mirror and / or the third dichroic mirror to be designed as a long-pass mirror.

[0042] A short-pass mirror refers to a mirror configured as a short-pass filter, and a long-pass mirror refers to a mirror configured as a long-pass filter. Characteristic of this filter option, either a short-pass mirror or a long-pass mirror, is the short transition between the pass band and the stop band. With a short-pass mirror, wavelengths shorter than the wavelength separating the absorption and transmission bands are transmitted, while longer wavelengths are reflected. Long-pass mirrors, on the other hand, transmit wavelengths longer than the wavelength separating the reflection and transmission bands and reflect the shorter wavelengths.

[0043] Accordingly, the wavelengths of the first light beam, the second light beam and the third light beam, which are superimposed to form the output radiation, can be easily determined and reflected or transmitted by means of the respective dichroic mirrors in such a way that the superposition can be carried out without significant losses.

[0044] Furthermore, within the scope of the invention, it can be provided that the beam splitter is designed to superimpose the first light beam, the second light beam, and the first power component of the third light beam to form the output radiation in a ratio of 80:20 to 20:80, preferably 70:30 to 30:70, more preferably 60:40 to 40:60. This can be achieved by the fourth light beam, formed from the superimposed first and second light beams, arriving at a first input of the beam splitter, and the first power component of this fourth light beam being output to a useful beam splitter output with the fourth power component of the third light beam arriving at a second beam splitter input.

[0045] The beam splitter can be configured to split the fourth light beam, formed from the first and second light beams, arriving in the first direction in such a way that between 20% and 80% of the first and second light beams arriving on the first and second beam paths are superimposed in the first direction to form the output radiation. Furthermore, between 80% and 20% of the third light beam arriving at the beam splitter in the second direction on the third beam path can be redirected in the first direction to superimpose the first and second beam paths.

[0046] Due to scattering and absorption at the components, losses of the first, second and third light beams of up to 5%, preferably up to 1%, can occur.

[0047] With regard to the present invention, it is conceivable that the second wavelength of the second light beam is greater than the third wavelength of the third light beam and that the third wavelength of the third light beam is greater than the first wavelength of the first light beam.

[0048] This sequence of wavelengths leads to an optimized behavior of the different lights or wavelengths, so that the final superimposed output radiation has a high light density with an optimized white balance.

[0049] Furthermore, it is conceivable that the first light source and / or the second light source and / or the third light source or the first luminous element and / or the second luminous element or the third luminous element are designed as a light-emitting diode or as a laser diode or as a light exit end of an optical fiber.

[0050] These allow for a space-saving design and easily and reliably generate the required spectral components of the first, second, and third light beams. Furthermore, they are inexpensive and have a long service life.

[0051] Advantageously, the first, second, and / or third light sources can be operated in continuous-wave mode. Likewise, one, several, or all of the light sources can be operated in pulsed mode. The pulse length can be, for example, between 1 ns and 1000 ms. The light sources can be operated in synchronous mode or sequentially pulsed.

[0052] Advantageously, a collimating lens system can be provided for collimating each of the first, second, and third beams. Collimating can be understood as the conversion of a divergent beam, as emitted by the respective light source, into a parallel beam. These collimating lenses can be lens groups or individual lenses. These can be arranged such that the beam paths (first beam path, second beam path, and third beam path) at the first dichroic mirror and at the beam splitter each have sections designed as collimated beams (parallel beams). This can be achieved by positioning the respective light source at the focal point of the associated lens group or individual lens. This can minimize chromatic aberrations in the output radiation due to any angular dispersion of the first dichroic mirror and / or the beam splitter.

[0053] A second aspect of the invention is a method for generating a multispectral output radiation, in particular a white light radiation with a high color rendering index, in particular Rf>92, with a multispectral light source, in particular a multispectral light source according to a first aspect of the invention, comprising the following steps:

[0054] - Providing a first light beam with a first wavelength, Providing a second light beam with a second wavelength, Providing a third light beam having a wavelength range A3min to A3max with a peak wavelength A3,

[0055] - combining the first light beam with the second light beam by means of a dichroic mirror to form a fourth light beam,

[0056] - guiding the fourth light beam to a beam splitter in a first direction,

[0057] - guiding the third light beam to the beam splitter in a second direction,

[0058] - dividing the fourth light beam by means of the beam splitter into a first power component and a second power component,

[0059] - dividing the third light beam into a third power component and a fourth power component by means of the beam splitter,

[0060] - combining the first power component with the fourth power component by means of the beam splitter to form a fifth light beam,

[0061] - Outputting the fifth light beam as output radiation

[0062] - Outputting the second power component and the third power component as residual radiation or further output radiation, wherein the beam splitter is designed as a partially transparent mirror and has a wavelength-independent splitting ratio between 30:70 and 70:30, in particular a splitting ratio of 50:50, up to a certain tolerance. The splitting ratio can be defined as the ratio between transmitted and reflected light. The splitting ratio can be the same for both beam splitter inputs. The splitting ratio can be determined with respect to the power of the respective light beams.

[0063] The fourth light beam can be guided to the first input of a beam splitter in a first direction. The third light beam can be guided to the second input of the beam splitter in a second direction, which can be perpendicular to the first direction.

[0064] The combination of the first power component with the fourth power component can also be referred to as superimposing these two power components. These superimposed power components can form the fifth light beam and have the same location and direction within the fifth light beam.

[0065] A useful beam output can be provided for outputting the fifth light beam as output radiation. The output radiation can be output as a parallel beam (collimated beam). It is also possible to focus the output radiation using a sixth single lens or lens group, for example, to output the output radiation into a waveguide, in particular an optical fiber.

[0066] The second power component and the third power component can be output to a residual beam output of the beam splitter. This can be designed as a beam trap or an absorber that converts the residual radiation into heat. The residual beam output can also be designed as a sensor. The sensor can be used to measure the light output, the color temperature, and / or other parameters. The residual beam output can also be designed as a photovoltaic generator to recover electrical energy from the discarded residual radiation.

[0067] The residual radiation may represent a superposition of the second and third power components. This may mean that these two power components are present together.

[0068] Instead of discarding the residual radiation, it may be advantageous to use the residual radiation as additional output radiation.

[0069] The splitter ratio may have a tolerance. The tolerance can be specified as a percentage based on the sum of transmitted and reflected light. The tolerance can manifest itself in a wavelength dependence within the tolerance range and / or a wavelength-independent deviation from the target value. The tolerance of the splitter ratio can be, for example, ±10%. In the case stated above, for example, a specified splitter ratio of 30:70 can be between 20:80 and 40:60 due to tolerance constraints.

[0070] Advantageously, the output radiation can be focused onto a focal point by means of a focusing optic, for example a single lens or lens group, for example an achromat or apochromat, and / or coupled into a waveguide, for example an optical fiber.

[0071] The output radiation can be multi-mode. The output radiation can be advantageously used to illuminate scenes for color-true viewing and / or for recording images or videos. In particular, it can be used to illuminate handcrafted items, especially jewelry items, as well as works of art. Color-true illumination with the output radiation can be advantageous for visual quality control, for example, of wallpaper or other printed matter. The output radiation can also be used to illuminate microscopic objects for microscopy and photomicrography.

[0072] Further advantages, features, and details of the invention will become apparent from the following description, which describes several embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. The invention is illustrated in the following figures:

[0073] Figure 1 is a schematic representation of a first embodiment of a multispectral light source,

[0074] Figure 2 is a schematic representation of the beam paths of the first embodiment of a multispectral light source,

[0075] Figure 3 is a schematic representation of a modification of the first embodiment of a multispectral light source,

[0076] Figure 4 is a schematic representation of a further modification of the first embodiment of a multispectral light source,

[0077] Figure 5 is a schematic representation of a second embodiment of a multispectral light source,

[0078] Figure 6 is a schematic representation of a third embodiment of a multispectral light source.

[0079] Figure 7 is a schematic representation of a method for generating output radiation.

[0080] Fig. 1 to Fig. 4 illustrate an embodiment of a multispectral light source 10 for generating output radiation 12. Several modifications of this exemplary embodiment are described. The multispectral light source 10 comprises a first light source 14, from which a first light beam 16 having a first wavelength A1 can be emitted, a second light source 18, from which a second light beam 20 having a second wavelength A2 can be emitted, and a third light source 22, from which a third light beam 24 having a wavelength range A3min to A3max can be emitted.

[0081] The first light source 14, the second light source 18 and the third light source 22 are arranged at a distance from one another, so that a first beam path 26 of the first light beam 16 and a second beam path 28 of the second light beam 20 and a third beam path 30 of the third light beam 24 differ from one another in their course at least in sections.

[0082] Additionally, at least one first dichroic mirror 32 is provided, wherein the first dichroic mirror 32 is configured to reflect the second light beam 20 and transmit the first light beam 16, and wherein the first dichroic mirror 32 is arranged in the first beam path 26 and the second beam path 28 such that the second light beam 20 is reflectable by the first dichroic mirror 32 and the first light beam 16 is transmittable by the first dichroic mirror 32. The first 16 and second 20 light beams are combined by means of the dichroic mirror to form a fourth light beam 76.

[0083] Additionally, a beam splitter 34 is provided, which is arranged downstream of the first dichroic mirror 32. The beam splitter 34 splits the fourth light beam 76, which is formed from the superimposed first light beam 16 and second light beam 20 and is incident on the beam splitter in the z direction, into a first power component 36 and a second power component 37. Perpendicular to the fourth light beam 76, the third light beam 30 is incident on the beam splitter 34 in the y direction. The third light beam is split at the beam splitter into a third power component 38 and a fourth power component 39.

[0084] The first power component 36 can be superimposed on the fourth power component 39 by the beam splitter 34 to form the output radiation 12. The combined first 36 and fourth 39 power components represent a fifth light beam 82. In addition, the second power component 37 and the third power component 38 can be superimposed on the beam splitter 34 to form the residual radiation 86.

[0085] A wavelength filter 62 is optionally provided between the third light source 22, which in this case is a broadband third light source 22, and the beam splitter 34. This wavelength filter 62 filters a predetermined wavelength, in this case a shade of blue, from the third light beam 24. In a modification of the exemplary embodiments not shown in the figures, such a filter can be omitted.

[0086] The beam splitter 34 is designed to superimpose the first light beam 16, the second light beam 20, and the second power component 37 of the third light beam 24 to form the output radiation 12 in a ratio of ideally 50:50. However, the ratio may vary slightly within the spectral range of the output radiation due to the tolerance of the beam splitter, for example, between 40:60 and 60:40. In further modifications of the exemplary embodiment, a different splitter ratio may be provided.

[0087] In a special case of the first exemplary embodiment, the light sources of Fig. 1 to 3 are provided such that the second wavelength A2 of the second light beam 20 is greater than the third wavelength A3 (peak wavelength) of the third light beam 24 and that the third wavelength A3 (peak wavelength) of the third light beam 24 is greater than the first wavelength A1 of the first light beam 16.

[0088] Figure 1 shows a schematic representation of the first embodiment. The light beams are shown schematically as arrows. For clarity, the superimposed light beams are represented by parallel arrows. In fact, the central beams, drawn parallel to one another in the figure, are positioned identically on top of each other (see Figure 2).

[0089] Figure 2 shows the marginal rays of the beam bundles. The superposition of the beam bundles is evident here. In the first exemplary embodiment, the beam splitter 34 can be plate-shaped, as shown in Figure 1, or, in an advantageous modification, as a beam splitter cube, as shown in Figure 2. In the plate-shaped embodiments of the first dichroic mirror 32 or the beam splitter 34, the functional coating can be located, as shown, on the side of the plate on which the second light beam 20 or the third light beam 30 impinges.

[0090] In the first embodiment, the output radiation can be focused by a sixth lens 74 and output into an optical fiber 88. The lens 74 can be a single lens or composed of several individual lenses in the sense of a lens group. It is advantageous to use an achromatic lens. The residual radiation 86 can be blocked by outputting it into a beam trap 90. In a modification, the beam trap 90 can be omitted and the residual radiation used as further output radiation 84. The further output radiation can represent a sixth beam bundle 86, which is formed from the union of the third 37 and fourth 38 power components.

[0091] In a modification of the first embodiment shown in Fig. 3, the output radiation 12 and the residual radiation 36 are arranged in reverse. The optional focusing optics (sixth lens) would then be positioned accordingly in the modified output beam 12. In this modification, the residual radiation 86 is directed to a detector 92, which can be used to determine light parameters such as power or spectrum.

[0092] In a further modification of the first embodiment, as shown in Fig. 4, a second mirror 40 is additionally provided. The second mirror 40 is designed to reflect the first light beam 16. This allows the first light source 14, the second light source 18, and the third light source 22 to be arranged side by side.

[0093] In the multispectral light source 10 of the second embodiment shown in Fig. 4, a second dichroic mirror 40 is additionally provided. The second dichroic mirror 40 is designed to reflect the first light beam 16. It is arranged in the first beam path 26 such that the first light beam 16 can be reflected by the second dichroic mirror 40. In the third embodiment, a third dichroic mirror 58 is also provided; this will be discussed further below.

[0094] The first dichroic mirror 32 of Figs. 1 to 4 is designed as a short-pass mirror.

[0095] Furthermore, in Figs. 1 and 2, the first light source 14, the second light source 18 and the third light source 22 are designed as a light-emitting diode.

[0096] Fig. 5 schematically shows a second embodiment of a multispectral light source 10. In this embodiment, the first light source 14 for providing 110 the first light beam 16 has a first illuminating element 42 and a first converter element 44. A first primary light 46 can be emitted from the first illuminating element 42, and the first light beam 16 can be emitted from the first converter element 44 by irradiation with the first primary light 46. The second mirror 40 is dichroic and is arranged in the first beam path 26 between the first illuminating element 42 and the first converter element 44, the first primary light 46 being transmittable by the second dichroic mirror 40 and the first light beam 16 being reflected by the second dichroic mirror 40.

[0097] In addition, the second light source 18 has a second illuminating element 48 and a second converter element 50 for providing the second light beam 20. A second primary light 52 can be emitted from the second illuminating element 48, so that the second light beam 20 can be emitted from the second converter element 50 by irradiation with the second primary light 52. Here, the first dichroic mirror 32 is arranged in the second beam path 28 between the second illuminating element 48 and the second converter element 50 such that the second primary light 52 is transmissive and the second light beam 20 is reflective. The third light source 22 is designed as a light-emitting diode. Fig. 6 schematically shows a third exemplary embodiment of a multispectral light source 10.In this exemplary embodiment, the third light source 22 for providing 110 the third light beam 24 has a third illuminating element 54, a third converter element 56, and the third dichroic mirror 58. The third dichroic mirror 58 is designed as a long-pass mirror.

[0098] A third primary light 60 can be emitted from the third luminous element 54, and the third light beam 24 can be emitted from the third converter element 56 by irradiation with the third primary light 60. The third dichroic mirror 58 is arranged between the beam splitter 34 and the third converter element 56 such that the third primary light 60 is reflected and the third light beam 24 is transmitted.

[0099] The multispectral light source 10 has laser diodes as the first illuminating element 42, second illuminating element 48, and third illuminating element 54. Alternatively, some or all of the illuminating elements can be designed as light-emitting diodes. In Figs. 1 to 4, the first beam path 26 comprises a first collimating optical unit 64 with the first lens 64, the second beam path 37 comprises a second collimating optical unit 66 with the second lens 66, and the third beam path 30 comprises a third collimating optical unit 68 with the third lens 68. The components referred to as lenses can each be an individual lens or composed of several individual lenses in the sense of a lens group. For example, achromats can be used, which can be composed of two cemented lenses. In Figs. 1 to 3, the first lens 64 is arranged between the first light source 14 and the first dichroic mirror 32, and in Fig. 4, between the first light source 14 and the second mirror 40.The second lens 66 is arranged between the second light source 18 and the first dichroic mirror 32, and the third lens 68 is arranged between the third light source 22 and the beam splitter 34. As a result, the beam paths (first beam path 26, second beam path 28, and third beam path 30) at the first dichroic mirror and at the beam splitter each have sections formed as collimated beams (parallel beams). This minimizes chromatic aberrations of the output radiation 12 caused by any angular dispersion of the first dichroic mirror 32 and / or the beam splitter 34.

[0100] In the second and third exemplary embodiments according to Figures 5 and 6, a first imaging optics system 64, 70 of the first beam path 26 has a fourth lens 70, which is arranged between the illuminant 14, 42 and the second dichroic mirror 40, and a first lens 64, which is arranged between the first converter element 44 and the second dichroic mirror 40. Furthermore, the multispectral light source 10 has a third lens 68 and a seventh lens 75 in the second imaging optics system. A fifth lens 72 is arranged between the illuminant 18, 48 and the first dichroic mirror 32, and the second lens 66 is arranged between the first dichroic mirror 32 and the second converter element 50. The third imaging optics system 68, 75 of the third exemplary embodiment in Fig.6 also has a seventh lens 75 between the illuminant 22, 54 and the third dichroic mirror 58 and the third lens 68 between the third dichroic mirror 58 and the third converter element 56.

[0101] The first imaging optics 64, 70 serve to image the first illuminating element 42 onto the first converter element 44. It shares the first lens 64 with the first collimating optics. The second imaging optics 66, 72 serve to image the second illuminating element 48 onto the second converter element 50. It shares the second lens 66 with the second collimating optics. The third imaging optics 68, 75 serve to image the third illuminating element 54 onto the third converter element 56. It shares the third lens 68 with the third collimating optics.

[0102] Fig. 7 shows the method 100 for generating a multispectral output radiation 12, in particular a white light radiation with a high color rendering index, in particular Rf>92, with a multispectral light source 10 according to one of Figs. 1 to 3.

[0103] The method 100 has the following steps: a. Providing 110 a first light beam 16 with a first wavelength A1, b. Providing 110 a second light beam 20 with a second wavelength A2, c. Providing 110 a third light beam 24 which has a wavelength range A3min to A3max with a peak wavelength A3, d. Combining 120 the first light beam 16 with the second light beam 20 by means of a first dichroic mirror 32 to form a fourth light beam 76, e. Feeding 130 the fourth light beam 76 to the beam splitter 34 in a first direction 78, f. Feeding 130 the third light beam 24 to the beam splitter 34 in a second direction 80, g. Dividing 140 the fourth light beam 76 by means of the beam splitter 34 into a first power component 36 and a second power component 37, h.Dividing 140 the third light beam 24 by means of the beam splitter 34 into a third power component 38 and a fourth power component 39, i. Combining 150 the first power component 36 of the fourth light beam 76 with the fourth power component 39 of the third light beam 24 by means of the beam splitter 34 to form a fifth light beam 82, j. Outputting 160 the fifth light beam 82 as output radiation 12, k. Outputting 160 the second power component (37) and the third power component (38) as a residual radiation (86) or a further output radiation (84), wherein the beam splitter 34 is designed as a partially transparent mirror and has a splitting ratio (ratio between transmitted and reflected light) between 30:70 and 70:30, in particular a splitting ratio of 50:50, which is wavelength-independent up to a tolerance of +-10%.

[0104] List of reference signs

[0105] 10 Multispectral light source

[0106] 12 Output radiation

[0107] 14 first light source

[0108] 16 first light beam

[0109] 18 second light source

[0110] 20 second light beam

[0111] 22 third light source

[0112] 24 third light beam

[0113] 26 first beam path

[0114] 28 second beam path

[0115] 30 third beam path

[0116] 32 first dichroic mirror

[0117] 34 beam splitters

[0118] 36 first performance component

[0119] 37 second performance component

[0120] 38 third performance component

[0121] 39 fourth performance component

[0122] 40 second mirror

[0123] 42 first luminous bodies

[0124] 44 first converter element

[0125] 46 first primary light

[0126] 48 second luminaires

[0127] 50 second converter element

[0128] 52 second primary light

[0129] 54 third luminous element

[0130] 56 third converter element

[0131] 58 third dichroic mirror

[0132] 60 third primary light

[0133] 62 wavelength filters

[0134] 64 First lens group, first single lens

[0135] 66 Second lens group, second single lens

[0136] 68 Third lens group, third single lens

[0137] 70 Fourth lens group, fourth single lens

[0138] 72 Fifth lens group, fifth single lens

[0139] 74 Sixth lens group, sixth single lens

[0140] 75 Seventh lens group, seventh single lens

[0141] 76 fourth light beam

[0142] 78 first direction 80 second direction

[0143] 82 fifth light beam

[0144] 84 further output radiation, sixth light beam

[0145] 86 Residual radiation

[0146] 88 waveguides, optical fibers

[0147] 90 beam trap

[0148] 92 detector

[0149] A1 first wavelength

[0150] A2 second wavelength

[0151] A3 third wavelength

[0152] 100 procedures

[0153] 110 Provision

[0154] 120 Unite

[0155] 130 feeders

[0156] 140 parts

[0157] 150 Unite

[0158] 160 Issues

Claims

Patent claims 1. A multispectral light source (10) for generating an output radiation (12), comprising: a first light source (14), wherein a first light beam (16) having a first wavelength (λ1) can be emitted from the first light source (14), a second light source (18), wherein a second light beam (20) having a second wavelength (λ2) can be emitted from the second light source (18), a third light source (22), wherein a third light beam (24) can be emitted from the third light source (22), which has a wavelength range λ3min to λ3max with a peak wavelength λ3, wherein the first light source (14), the second light source (18), and the third light source (22) are arranged at a distance from one another, at least one first dichroic mirror (32) for combining the first (16) and second light beams (20) into a fourth light beam (76),wherein the first dichroic mirror (32) is designed to reflect the second light beam (20) and transmit the first light beam (16), and wherein the first dichroic mirror (32) is arranged such that the second light beam (20) is reflectable by the first dichroic mirror (32) and the first light beam (16) is transmittable by the first dichroic mirror (32), and a beam splitter (34) arranged downstream of the first dichroic mirror (32), wherein the beam splitter (34) is designed to split the fourth light beam (76) formed from the first light beam (16) and the second light beam (20) into a first power component (36) and a second power component (37) and to split the third light beam (24) into a third power component (38) and a fourth power component (39),wherein the first power component (36) can be superimposed on the fourth power component (39) by the beam splitter (34) to form the output radiation (12), and the second power component (37) together with the third power component (38) can be output as a residual radiation (86) or a further output radiation (86).

2. Multispectral light source (10) according to claim 1, characterized in that a second mirror (40) is provided, wherein the second mirror (40) is designed to reflect the first light beam (16), and wherein the second mirror (40) is arranged such that the first light beam (16) is reflectable by the second mirror (40) before it strikes the first dichroic mirror (32).

3. Multispectral light source (10) according to claim 2, characterized in that in that the first light source (14) for providing the first light beam (16) has a first illuminating body (42) and a first converter element (44), wherein a first primary light (46) can be emitted from the first illuminating body (42), and wherein the first light beam (16) can be emitted from the first converter element (44) by irradiation with the first primary light (46), wherein the second mirror (40) is dichroic and is arranged between the first illuminating body (42) and the first converter element (44) such that the first primary light (46) can be transmitted through the second mirror (40) and the first light beam (16) can be reflected by the second mirror (40).

4. Multispectral light source (10) according to one of claims 1 to 3, characterized in that the second light source (18) for providing the second light beam (20) has a second luminous body (48) and a second converter element (50), wherein a second primary light (52) can be emitted from the second luminous body (48), and wherein the second light beam (20) can be emitted from the second converter element (50) by irradiation with the second primary light (52), wherein the first dichroic mirror (40) is arranged between the second luminous body (48) and the second converter element (50) such that the second primary light (52) can be transmitted and the second light beam (20) can be reflected.

5. Multispectral light source (10) according to one of claims 1 to 4, characterized in that the third light source (22) for providing the third light beam (24) has a third luminous element (54), a third converter element (56) and a third dichroic mirror (58), wherein a third primary light (60) can be emitted from the third luminous element (54), and wherein the third light beam (24) can be emitted from the third converter element (56) by irradiation with the third primary light (60), wherein the third dichroic mirror (58) is arranged between the beam splitter (34) and the third converter element (56) such that the third primary light (60) can be reflected and the third light beam (24) can be transmitted.

6. Multispectral light source (10) according to one of claims 1 to 4, characterized in that a wavelength filter (62) is provided between the third light source (22), in particular a broadband third light source (22), and the beam splitter (34), wherein the wavelength filter (62) is designed to filter a predetermined wavelength from the third light beam (24).

7. Multispectral light source (10) according to one of claims 1 to 6, characterized in that that the first dichroic mirror (32) and / or the second dichroic mirror (40) is designed as a short-pass mirror and / or the third dichroic mirror (58) is designed as a long-pass mirror.

8. Multispectral light source (10) according to one of the preceding claims, characterized in that the beam splitter (34) is designed to superimpose the first power component (36) with the fourth power component (37) to form the output radiation (12) in a ratio of 80:20 to 20:80, preferably of 70:30 to 30:70, more preferably of 60:40 to 40:

60.

9. Multispectral light source (10) according to one of the preceding claims, characterized in that the second wavelength (A2) of the second light beam (20) is greater than the peak wavelength (A3) of the third light beam (24) and that the peak wavelength (A3) of the third light beam (24) is greater than the first wavelength (A1) of the first light beam (16).

10. Multispectral light source (10) according to one of the preceding claims, characterized in that the first light source (14) and / or the second light source (18) and / or the third light source (22) or the first luminous element (42) and / or the second luminous element (48) or the third luminous element (54) are designed as a light-emitting diode or as a laser diode or as a light exit end of an optical fiber.

11. Method (100) for generating multispectral output radiation (12), in particular white light radiation with a high color rendering index, in particular Rf>92, with a multispectral light source (10), in particular a multispectral light source (10) according to one of the preceding claims, comprising the following steps: a. providing (110) a first light beam (16) with a first wavelength (λ1), b. providing (110) a second light beam (20) with a second wavelength (λ2), c. providing (110) a third light beam (24) which has a wavelength range λ3min to λ3max with a peak wavelength λ3, d. combining (120) the first light beam (16) with the second light beam (20) by means of a first dichroic mirror (32) to form a fourth light beam (76), e. guiding (130) the fourth light beam (76) to a beam splitter (34) in a first direction (78), f. guiding (130) the third light beam (24) to the beam splitter (34) in a second direction (80), g. splitting (140) the fourth light beam (76) by means of the beam splitter (34) into a first power component (36) and a second power component (37), h. splitting (140) the third light beam (24) by means of the beam splitter (34) into a third power component (38) and a fourth power component (39), i. combining (150) the first power component (36) with the fourth power component (39) by means of the beam splitter (34) to form a fifth light beam (82), j. outputting (160) the fifth light beam (82) as the output radiation (12), k.Outputting (160) the second power component (37) and the third power component (38) as a residual radiation (86) or a further output radiation (84), wherein the beam splitter (34) is designed as a partially transparent mirror and has a splitting ratio between 30:70 and 70:30, in particular a splitting ratio of 50:50, which is wavelength-independent up to a tolerance.

Images