DE102017210526A1 - Lighting unit for emitting illumination light - Google Patents

Abstract

The present invention relates to an illumination unit (1) for emitting illumination light (6), having a pump radiation source (2) for emitting pump radiation (4), a phosphor element (3) for at least partial conversion of the pump radiation (4) and a reflector (3). 8), via whose reflection surface (9) which the pump radiation (4) to the phosphor element (3) is guided, wherein the reflection surface (9) at least partially (9 a) is concavely curved and viewed in a sectional plane has the shape of a parabola portion, and wherein an incident beam (21), along which the pump radiation (4) falls on the reflection surface area (9a), is tilted to a parabolic axis (28) of the parabola P on which the parabolic section is based.

Description

Technical area

The present invention relates to a lighting unit with a pump radiation source for emitting pump radiation and a phosphor element for the at least partial conversion of the pump radiation into a conversion light.

State of the art

With the combination of a pump radiation source of high power density, such as a laser, and a spaced apart arranged fluorescent element that emits light in response to the pump radiation towards conversion light, light sources high luminance can be realized. The pump radiation is incident on an irradiation surface of the phosphor element, and the conversion light is emitted at a radiating surface. When operated in transmission, the Einstrahl- and the radiating surface are opposite to each other, when operating in reflection they coincide. Not necessarily the entire pump radiation must be converted (full conversion), but also an unconverted part thereof with the conversion light in mixture can be used as illumination light (partial conversion).

Presentation of the invention

The present invention is based on the technical problem of specifying a particularly advantageous lighting unit.

According to the invention we achieved this with a lighting unit according to claim 1. The pump radiation is guided via a reflection surface to the phosphor element, which is concavely curved and parabolic in section at least in the region onto which the pump radiation falls. With reference to the parabola on which the parabola is based, the pump radiation is guided tilted onto the reflection surface. An incident beam, along which the pump radiation falls on the reflection surface area, is thus not parallel to the axis, but tilted to the parabolic axis.

Preferred embodiments can be found in the dependent claims and the entire disclosure, wherein in the representation of the features is not always distinguished in detail between device and process or use aspects; In any case, implicitly, the disclosure must be read with regard to all categories of claims.

With regard to the desired high power and thus luminance, it is on the one hand of interest to bundle the pump radiation onto the phosphor element, which is achieved in principle with the at least partially concave reflection surface. On the other hand, the inventor has found that, with the beam guidance tilted towards the parabola axis, that is to say, for example, through the deliberate introduction of aberrations or an etendue enlargement, a certain homogenization of the irradiance profile generated with the pump radiation on the phosphor element can ideally be achieved. Figuratively speaking, such a spot generated by the pump radiation on the irradiation surface of the phosphor element can be smeared a little. This can be prevented, for example, a local increase in the irradiance, ie a hot-spot formation, which could otherwise lead to damage to the phosphor element.

The area of the reflection surface irradiated with the pump radiation is referred to as the "reflection surface area". Downstream of this, the pumping radiation impinges on the irradiation surface of the phosphor element, the area irradiated therefrom being referred to as a "spot". Preferably, the reflection surface area and / or the spot are each part of an overall larger area, ie, the reflection surface area does not completely fill the reflection area and / or the spot does not fill the irradiation area. For the size of reflection surface area and / or spot, the irradiance generated on the reflection or irradiation surface is considered; Although the extent of the irradiance distribution could generally be measured even after a decrease to 1 / e ^{2 of} a maximum irradiance, it is preferred to use a decrease to 1/2, ie the half width.

Viewed in section, the reflection surface area has the shape of a parabolic section, ie a section of a parabola. The parabola has a vertex and a parabolic branch on both sides, also called a parabola leg. The parabola axis results as a connecting line from the apex to the focal point, the parabola branches are mutually with the parabolic axis as the axis of symmetry mirror symmetry. The reflective surface area can generally also extend over the vertex, ie have a share of both parabola branches, but it is preferably located exclusively in one of the parabola branches, more preferably at a distance from the vertex (see below in detail). Nevertheless, the parabola section clearly defines a parabola whose vertex and focus are uniquely determined (just as, for example, a circular arc clearly defines a circle).

The "incident beam" corresponds to the center axis of the radiation beam of the pump radiation impinging on the reflection surface area. The center axis lies parallel to the direction of gravity of the radiation beam and in the center thereof, ie viewed in sectional planes perpendicular to the direction of gravity, in each case in the centroid (the cross-sectional area of the radiation beam). Insofar as reference is generally made within the scope of this disclosure to a "direction of gravity" of radiation or light, this results in each case as the average value of all the directional vectors of the respective considered beam at the respectively considered point, wherein in averaging each directional vector is weighted with its associated beam intensity becomes.

In a preferred embodiment, the incident beam is tilted to the parabolic axis by at least 5 °, in the order of entry more preferably at least 6 °, 7 °, 8 °, 9 °, 10 °, 11 ° or 12 °. Preferred upper limits are at most 50 °, 40 °, 35 °, 30 ° and 25 ° (in the order of naming increasingly preferred), the upper and lower limits are generally disclosed independently. Considered is the smaller of two angles, the incident and the parabola axes enclosing each other (and adding up to 180 °). The mentioned angles can be advantageous, for example, in that, with the tilt, on the one hand a sufficient "smearing" of the spot is achieved, but on the other hand the aberrations do not become too dominant.

In a preferred embodiment, the concave curved reflection surface area, on which the pump radiation is incident and reflected, has the shape of a parabolic section in all sectional planes, each of which includes an optical axis of the reflector. The optical axis of the reflector results, for example, as the axis of symmetry about which the reflection surface or at least the reflection surface region is at least rotational, preferably rotationally symmetrical. Preferably, the reflector as a whole, ie the reflector body, on the side surface of the reflection surface is formed, at least rotationally symmetrical about the optical axis. Irrespective of this, the reflector body can be provided, for example, of plastic or glass or also of metal, it being possible for a reflection layer applied separately in the last-mentioned case to form the reflection surface, for example a silver film.

In a preferred embodiment, the reflection surface area is rotationally symmetrical about the optical axis of the reflector. Preferably, the reflection surface as a whole is rotationally symmetrical about the optical axis, this is particularly preferred for the entire reflector (including the reflector body). However, the rotational symmetry does not necessarily imply an encircling closed geometry, so the reflection surface does not have to be closed around the optical axis. As far as a reflection surface is present, but it should be correspondingly symmetrical. Preferably, the optical axis and a failure beam intersect, particularly preferably exactly in the incident surface.

In a preferred embodiment, the reflective surface area is not too far away from the parabola axis. For this purpose, reference is made to a distance d, which results in the sectional plane as the smallest distance between the reflection surface area and the parabolic axis, which is taken perpendicular to the latter. In the case of a reflection surface area containing the vertex, d = 0, the reflection surface area is preferably at a distance from the vertex, ie d> 0. On the other hand, the smallest distance d should not be too large, namely less than half the width p of the parabola. The width is taken at the height of its focal point, the half-width p thus results as taken perpendicular to the parabola axis distance between focus and parabola.

In a preferred embodiment, the distance d is at most 0.9 × p (0.9 times the half-width), with further preferred upper limits being at most 0.8 × p, 0.7 × p, 0.6 × p or 0.5 · p. A preferred lower limit is at least 0.1 × p, with at least 0.15 × p or 0.2 × p being further and particularly preferred. In general, the lower and upper limits should also be disclosed independently of one another; the distance d is preferably within a corresponding interval with upper and lower limits.

In general, a laser source is preferred as the pump radiation source, that is, the pump radiation is laser radiation. Particularly preferred is a laser diode as a pump radiation source, wherein a total of a plurality of pump radiation sources can be provided. These can be around the optical Be arranged axis of the reflector, preferably rotationally symmetrical to each other. The spots superimposed on the irradiation surface can, for example, describe a rosette shape. In general, "one" and "one" without expressly indicating otherwise are to be read as indefinite articles and thus always as "at least one" and "at least one".

In a preferred embodiment, an emission surface of the pump radiation source, which in the case of the laser diode is also referred to as a "facet", has an elongate shape. The emission surface has taken along a length axis at least 0.5 times greater extent than along a perpendicular axis width. Further lower limits are increasingly preferred in the order in which they are mentioned, with at least the 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9-, 10-, 11-, 12- , 13-, 14- resp. 15 times greater extension along the length axis; possible upper limits (independent of these) are at most 500, 400, 300, 200, 100, 90, 80, 70, 60, 50, 40, 30 and 25, respectively -fold larger extension. The emission surface preferably has its smallest extent on the width axis. Preferably, the emission surface has a rectangular shape. In general, the emission area is preferably flat.

In the case of the laser diode, a corresponding rectangular facet may result as a result of the layer structure. In absolute values, the emission area on the width axis may, for example, have an extension of at least 0.5 μm, further and particularly preferably at least 0.7 μm or 0.8 μm, with possible upper limits of at most 1.5 μm, 1.3 μm or 1.2 μm (increasingly preferred in the order of entry). On the length axis, the emission surface may, for example, over at least 15 microns, further and more preferably at least 17 microns or 18 microns, with possible (independent) upper limits at most 500 microns, 400 microns, 300 microns, 200 microns, 100 microns , 50 .mu.m, 25 .mu.m, 23 .mu.m and 22 .mu.m, respectively (increasingly preferred in the order in which they are mentioned). In the present case, an emission surface with an elongated shape may be of particular interest, because the main beam guide (tilted to the parabolic axis) may allow a uniform (round or square) spot shape on the irradiation surface, despite the elongated initial shape. This will be described below. Typical spot sizes, taken in each case as the average value of the smallest and largest extent, may be, for example, at least 20 .mu.m, 50 .mu.m, 100 .mu.m, 150 .mu.m or 200 .mu.m, with possible (independent) upper limits, for example at most 1 mm , 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm and 0.4 mm, respectively.

In a preferred embodiment, the emission surface is imaged with the reflection, that is, the reflector is part of an imaging optics or it forms such for itself. By way of illustration, the parabola may, for example, have a focal length of 14 mm and an upstream collimating lens a focal length of 4 mm, which then has a magnification of 3.5 × ( 14 / 4 ). The inventor has generally found that the reflection surface due to the tilted radiation not only has a focus as it would have a paraboloidal shape with paraxial radiation. Instead, a first focus results in the sectional plane containing the optical axis of the reflector and a second focus in a sectional plane perpendicular thereto, which includes the failure beam leading away from the reflection surface area. As a result of the combination of tilting and rotational symmetry, the reflection surface area in this sectional plane may have a comparatively complex shape, which may possibly be approximated as a paraboloid or ellipsoid of a higher order. The failure beam is analogous to the incident beam as the center axis of the beam, in this case after reflection.

Relative to the imaging of the emission surface, a first and a second image plane result, these image planes are offset from one another along the emission beam. The size of the offset also depends on the tilt, etc., but may well assume for illustration purposes values that correspond on the order of magnitude to the distance of the first image plane from the reflection surface area. The first image plane is the proximal to the reflection surface area, the second the distal one. Based on the distance which has the first image plane from the reflection surface area, the two image planes can be spaced apart from one another by at least 20%, 40% or 60%, for example, with possible (independent) upper limits of, for example, at most 200%, 150%, 100% and 80% respectively (the distances are taken along the failure beam).

In a preferred embodiment, a first image of the emission surface, which lies in the first image plane, and a second image thereof, which lies in the second image plane, are mutually rotated. This refers to a rotation about the failure beam as a rotation axis. The two images are preferably rotated by 90 ° to each other. This can be achieved, for example, by forming the reflection surface area in that plane which the incident and the exit beam span with one another, in the shape of a parabola and otherwise by a rotation (see above).

In a preferred embodiment, the phosphor element, specifically the Einstrahlfläche, arranged between the two image planes. This may be advantageous in the emitting surface of elongate shape. In each of the image planes, the elongated shape would be displayed, with the placement in between, it can be, at least partially or even completely offset, also due to the twisted images. If the width and the length axis are imagined with the incident surface, the spot dimensions taken along both axes differ less than on the emission surface. For example, the larger dimension may be at most the 2, 1.5, 1.3, 1.2, and 1.1 times the smaller extent. Preferably, the spot dimensions taken in each case along the length and width axes depicted on the irradiation surface can be of equal size (for technical reasons, lower limits may lie with a difference of at least 1%, 2% or even 5%).

In a preferred embodiment, based on the propagation of the pump radiation, a collimating lens is arranged between the emission surface and the reflection surface. The beam with the pump radiation passes through them and is thereby essentially collimated. The latter means that the full width half maximum (FWHM) of the beam of collimating lens taken after the half-width is at most 5 °, in the order of the designation increasingly preferably at most 4 °, 3 °, 2 °, 1.5 ° , 1 °, 0.8 °, 0.7 ° and 0.6 °, respectively. If the beam should have a different opening angle in different sectional planes, each including the center axis, a mean value formed over the revolution about the center axis is taken as the basis. Correspondingly collimated, the pump radiation falls on the reflection surface, with the reflection, it is bundled.

In general, the collimating lens can also be constructed in several parts from a plurality of individual lenses, preferably it is exactly one single lens. Upstream of the collimating lens, the pump radiation beam can have a different opening angle on different axes. This may be due to the emission area of elongated shape, on the length axis the opening angle is then smaller than on the width axis, the former is also referred to as "slow axis", the latter as "fast axis".

In a preferred embodiment, the full opening angle of the beam with the pumping radiation of the collimating lens immediately downstream is at least 0.1 °, in the order of naming increasingly preferred at least 0.2 °, 0.3 °, 0.4 ° and 0.5 °. The beam is therefore intentionally not perfectly collimated beyond a possible accuracy. Decollimation can be achieved by a (slight) divergence, but also by convergence; the opening angle in the latter case is that angle which the beam would have deposited downstream of a focal point. The inventor has found that deviating from the perfect collimation (0 °) in terms of the desired spot homogenization can be advantageous.

In this case, an optimal position of the irradiation surface can also shift, namely, tend to be closer to the first image plane. Another observation is that decollimation has different effects on the image planes. In summary, a slight decollimation with regard to the homogenization, that is to say the avoidance of "peaks" or edge-side "overshoots" in the irradiance profile on the irradiation surface, may be of interest.

The phosphor element may be, for example, a phosphor applied in particle form, but it may also be a phosphor ceramic, which may in particular be monocrystalline. "Phosphor" is also to read on a mixture of several individual phosphors. A preferred single phosphor may be cerium doped yttrium aluminum garnet (YAG: Ce). The phosphor element can be antireflection-coated at the irradiation / emission surface, for example with a dichroic layer system. If such antireflection coating is provided, it is considered as part of the phosphor element and forms its outer surface the Einstrahl- / radiating surface.

In general, the phosphor element is preferably operated in reflection, that is to say the irradiation surface is at the same time also the emission surface at which the conversion light is removed (possibly in a mixture with proportionally unconverted pump radiation). For this purpose, the emission surface can preferably be associated with an illumination optics; This can, for example, map every point of the incident / radiating surface to infinity.

In a preferred embodiment, the illumination light of the illumination optics is guided downstream via a reflective area light modulator, in particular via a micromirror array (DMD, digital micromirror device). At least 20, 40, 60, 80 or 100 micromirrors, but also significantly more micromirrors are possible, for example at least 1,000, 5,000 or 10,000, or even at least 20,000, 40,000, 60,000 and 80,000 micromirrors, respectively. Possible upper limits may be (independently of), for example, at most 1 × 10 ⁷ , 1 × 10 ⁶ , 5 × 10 ⁵ , 2 × 10 ^5, or 1 × 10 ⁵ . The micro-mirror array has a Nutzlichtkegel, which is supplied depending on the mirror position of individual of the mirrors with illumination light, or not. The useful light cone is that solid angle area associated with the micromirror array which is completely filled with illumination light when all micromirrors are switched on. The illumination light in the useful light cone then passes to the illumination application, for example, via a further optics, such as a reflector.

A preferred field of application may be in the field of vehicle lighting, in particular the vehicle exterior lighting. In general, use in ships or aircraft (helicopter / aircraft) is possible, preferred are motor vehicles, such as trucks or motorcycles, particularly preferably passenger cars (cars). Preferred is an application in a headlight, in the case of the motor vehicle (motor vehicle) for street lighting.

With the area light modulator, an adaptive street illumination is advantageously possible; by adding or removing the individual micromirrors, a respective solid angle range can be selectively supplied with light, that is, the illumination light supply can be switched on or off in the space angle range. Thus, for example, an oncoming or preceding vehicle can be excluded from the illumination beam to avoid glare, with the micromirror array (and the large number of micromirrors) even with a very high resolution. For example, it may even illuminate the other vehicle and only the passenger compartment will be excluded from the lighting.

list of figures

In the following, the invention will be explained in more detail with reference to embodiments, wherein the individual features in the context of the independent claims in another combination may be essential to the invention and continue to distinguish not in detail between the different categories of claims.

• 1 eine erfindungsgemäße Beleuchtungseinheit mit Pumpstrahlungsquellen, Reflektor und Leuchtstoffelement;
• 2 einen Teil der Anordnung gemäß 1 in einer Detailansicht;
• 3a-c mit dem Reflektor erzeugte Abbildungen einer Emissionsfläche der Pumpstrahlungsquelle der Anordnung gemäß 2 in unterschiedlichen Bildebenen.

In detail shows

• 1 a lighting unit according to the invention with pump radiation sources, reflector and phosphor element;
• 2 a part of the arrangement according to 1 in a detailed view;
• 3a-c with the reflector generated images of an emission surface of the pump radiation source of the arrangement according to 2 in different picture levels.

Preferred embodiment of the invention

1 shows a lighting unit according to the invention 1 with pump radiation sources 2 (Laser diodes) and a phosphor element 3 , The pump radiation sources 2 each emit a pump radiation 4 on an irradiation surface 5 of the phosphor element 3 to be led. In the present case, it is the pump radiation 4 to blue laser light, the phosphor element 3 has YAG: Ce as a phosphor. This emits the excitation with the pump radiation 4 towards a yellow conversion light, which together with partially unconverted pump radiation, an illumination light 6 forms, namely white light. Surrounding are several pump radiation sources 2 provided, two are shown.

The phosphor element 3 is operated in reflection, the Einstrahlfläche 5 is therefore at the same time radiating surface in which the illumination light 6 is emitted. The radiating surface 5 is a lighting look 7 assigned to a part of the radiating surface 5 emitted illumination light 6 collects, bundles and supplies a lighting application, via a non-illustrated area light modulator (micromirror array, DMD). The phosphor element 3 is on a heat sink 11 mounted, this in turn on a mounting plate 10 which also carries the laser diodes.

The pump radiation 4 is doing over a reflector 8th , specifically its reflection surface 9 , on the irradiation surface 5 guided. 2 illustrates this for one of the pump radiation sources 2 further in detail. The pump radiation 4 becomes the pump radiation source 2 immediately downstream with a collimating lens 20 essentially collimated (see below). It falls along an incident ray 21 to one area 9a the reflection surface. There it is reflected and then spreads along a failure beam 22 to the Einstrahlfläche 5 of the phosphor element 3 out.

The reflector 8th has an optical axis 25 , this lies in the plane of the drawing, ie the section plane shown. In this section has the reflection surface 9 the shape of a parabolic section, this is a parable P based. The parable P has a vertex 26 , a focal point 27 and a connecting parabolic axis 28 , To the parabolic axis 28 parallel incident rays would be at the focal point 27 bundled.

How out 2 can be seen, is the incident beam 21 tilted to the parabolic axis by slightly more than 20 °. This deliberately generates an aberration or an increase in the size of the Etendue, which results in a certain homogenization of the irradiance profile on the irradiation surface 5 of the phosphor element 3 results. The reflection surface 9 is about the optical axis 25 rotationally symmetric and has the incident beam perpendicular to the plane of the drawing 21 Containing cutting planes considered a comparatively complex shape.

An emission surface of the pump radiation source 2 from which the laser radiation is emitted, has an elongated shape, namely in the plane of the drawing has an extent of about 20 microns, perpendicular to it only about 1 micron. With the in the section shown parabolic reflection surface 9 the emission surface becomes a first image plane 30 displayed. As a result of the tilted radiation, however, there is also a second image plane 31 , which also contains an image of the emission area. The two pictures are rotated by 90 ° to each other.

This is illustrated by the 3a and b, which each schematically represent the result of a ray tracing simulation. The 3a shows the picture 40 the emission surface in the first image plane 30 in oblong shape. The second picture 41 in the second picture plane 31 shows a comparable elongated shape, but is rotated by 90 ° (around the failure beam 22 ). How out 2 can be seen, the phosphor element 3 with the irradiation surface 5 between the picture planes 30 . 31 arranged what the in 3 shown spot 42 results. Thus, in spite of the originally elongated shape of the emission surface, a substantially square irradiance profile can be achieved. The irradiance is approximated to a so-called flat top shape.

The pump radiation 4 is done with the collimation lens 20 not completely collimated (0 °), but has the collimation lens 20 downstream of an opening angle (FWHM) of about 0.5 °. Thus, a further homogenization of the irradiance distribution can be achieved and, if necessary, peaks in the irradiance profile can be avoided. In 1 not shown is the holder of the Kollimationslinsen 20 , To recognize, however, is a support plate 10 , on the one hand the pump radiation sources 2 and on the other hand, a heat sink 11 is mounted, on which the phosphor element 3 sitting.

LIST OF REFERENCE NUMBERS

lighting unit 1 Pump radiation source 2 Fluorescent element 3 pump radiation 4 irradiation surface 5 illumination light 6 illumination optics 7 reflector 8th reflecting surface 9 Reflection surface area 9a mounting plate 10 heatsink 11 collimating lens 20 incident beam 21 failure beam 22 Optical axis 25 focus 27 parabola axis 28 First picture plane 30 Second picture plane 31 First picture 40 Second picture 41 commercial 42 parabola P Half width of the parabola P Smallest distance (Reflection surface area / parabola axis) d Angle (incident beam / parabolic axis) α

Claims (15)

Lighting unit (1) for emitting illumination light (6), with a pump radiation source (2) for emitting pump radiation (4), a phosphor element (3) for the at least partial conversion of the pump radiation (4) into a conversion light (6) which at least partially forms the illumination light (6), and a reflector (8) having a reflection surface (9), via which the pump radiation (4) is guided by the pump radiation source (2) to the phosphor element (3), wherein the reflection surface (9) is in any case concavely curved in a region (9a) on which the pump radiation (4) falls and, viewed in a sectional plane, has the shape of a parabolic section, and wherein an incident beam (21), along which the pump radiation (4) falls on the reflection surface area (9a), is tilted to a parabolic axis (28) of the parabola P on which the parabolic section is based. Lighting unit (1) after Claim 1 in which the incident beam (21) is tilted to the parabolic axis (28) by at least 5 ° and at most 50 °. Lighting unit (1) after Claim 1 or 2 in which the reflector (8) has an optical axis (25) and the reflection surface area (9a), on which the pump radiation (4) falls, has the form of a parabolic section in all sectional planes including the optical axis (25). Lighting unit (1) after Claim 3 in which the reflection surface area (9a) on which the pump radiation (4) falls is rotationally symmetrical about the optical axis (25). Lighting unit (1) according to one of the preceding claims, wherein the reflection surface area (9a), on which the pump radiation (4) falls, in the sectional plane has a smallest distance d to the parabola axis (28) of the parabola P, on which the parabolic section is based is smaller than half a width p of the parabola P at the height of the focal point (27). Lighting unit (1) after Claim 5 in which the distance d is at least 0.1 · p and at most 0.9 · p, 0.1 · p ≤ d ≤ 0.9 · p. Lighting unit (1) according to one of the preceding claims, in which an emission surface of the pumping radiation source (2), at which the pumping radiation (4) is emitted, has an elongated shape, ie taken along a longitudinal axis, at least 0.5 times larger Extension as has taken along a perpendicular axis width. Lighting unit (1) according to one of the preceding claims, in which the reflection surface area (9a) has a first image plane (30) in which a first image (40) of an emission surface of the pump radiation source (2) lies, and also a second image plane (31). in which there is a second image (41) of the emission surface, wherein the first (30) and the second image plane (31) relate to a failure beam (22) along which the pump radiation (4) emerges from the reflection surface region (9a) spread, are offset from each other. Lighting unit (1) after the Claims 7 and 8th in which the first (40) and the second image (41) are rotated around one another by the exit beam (22), preferably by 90 °. Lighting unit (1) according to one of Claims 7 to 9 in which the phosphor element (3) is arranged relative to the reflection surface region (9a) such that an irradiation surface (5) of the phosphor element (3) on which the pump radiation (4) falls falls between the first (30) and the second image plane (31) lies. Lighting unit (1) after Claim 10 in which a spot (42) generated by the pump radiation (4) on the irradiation surface (5) of the phosphor element (3) is taken along two axes which result from imaging the length and width axes on the irradiation surface (5) has an extension that differs from the respective other extent by no more than 20%. Lighting unit (1) according to one of the preceding claims with a collimating lens (20), which passes through the pump radiation (4) of the reflection surface (9) upstream, wherein a beam with the pump radiation (4) of the collimating lens (20) immediately downstream of a full opening angle of 5 ° at the most. Lighting unit (1) after Claim 12 in which the full opening angle of the beam with the pump radiation (4) of the collimating lens (20) immediately downstream is at least 0.1 °. Lighting unit (1) according to one of the preceding claims with a reflective surface light modulator, via which the light emitted at a radiating surface of the phosphor element (3) illumination light (6) is supplied to a lighting application. Use of a lighting unit (1) according to one of the preceding claims for lighting, in particular for the exterior lighting of a motor vehicle, in particular for adaptive street lighting.

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