Irradiation device with radiation unit

Abstract

Irradiation device (1) with: a radiation unit (2) for the emission of radiation in the form of a beam of radiation in the temporal integral, a first microlens arrangement (4) downstream of the radiation unit (2) with a plurality of microconverging lenses (4a, b) arranged side by side in a common plane with respect to the direction of radiation propagation for dividing the beam into a partial beam (20a, b) for each microconverging lens (4a, b), and a converging lens (9) downstream of the microlens arrangement (4), which superimposes the partial beams (20a, b) in the temporal integral in an irradiation surface (5), wherein the microconcentrating lenses (4a, b) of the first microlens arrangement (4) are divided into at least a first group and a second group, each with a plurality of microconcentrating lenses (4a, b), wherein the microconverging lenses (4a, b) are identical in each group, but the microconverging lenses (4a) of the first group differ from the microconverging lenses (4b) of the second group in at least one aspect of their shape, size and focal length, such that a first area (21a) of the irradiation surface (5) irradiated by the microconverging lenses (4a) of the first group differs in at least one aspect of its shape and size from a second area (21b) of the irradiation surface (5) irradiated by the microconverging lenses (4b) of the second group; in which the microconcentrating lenses (4a) of the first group are irradiated with a first irradiance and the microconcentrating lenses (4b) of the second group are irradiated with a second irradiance, wherein the irradiation device (1) is configured to vary the ratio of first irradiance to second irradiance.

Description

Technical field

[0001] The invention relates to an irradiation device with a radiation unit for emitting radiation in the form of a beam and a downstream optics for beam beam shaping. State of the art

[0002] The radiation emitted by the irradiation device can, for example, be in the UV or short-wave visible range and can be used, for example, to irradiate a phosphor element, which then emits conversion radiation, such as visible conversion light, upon this excitation. By combining an irradiation device as a pump radiation source with a phosphor element arranged at a distance from it, high-luminance light sources can be realized, which can be used, for example, in projection devices. This is intended to illustrate one possible application area of ​​the irradiation device according to the invention, but does not limit the subject matter in its generality.

[0003] EP 1 210 749 B1 describes a laser system for the laser crystallization of semiconductor films. It comprises a laser source for generating a laser beam with a first intensity profile in a transverse direction and a lens system for modifying the first intensity profile, wherein the lens system comprises a plurality of lens elements configured to split the beam into a plurality of partial beams across the first intensity profile, wherein at least one of the partial beams emitted by the lens system is inverted relative to the others, such that a desired intensity profile is generated at the output of the laser system.

[0004] DE 10 2011 107 893 A1 relates to an optoelectronic module, in particular an optoelectronic chip-on-board module. The optoelectronic module comprises a substrate, the substrate being a planar surface. Furthermore, the optoelectronic module comprises a plurality of optoelectronic components arranged on the substrate. The optoelectronic module also includes at least one optical system mounted on the substrate, in particular a micro-optic system with a plurality of micro-optical elements. The optical system comprises at least one primary optical system adjacent to the optoelectronic components and at least one secondary optical system.

[0005] DE 10 2013 202 334 A1 relates to a lighting device for providing light. The lighting device comprises a light source, a collimator, a microlens layer, and at least one immersion layer. The light source generates inhomogeneous light. The collimator collimates the inhomogeneous light. The microlens layer homogenizes the collimated inhomogeneous light and has a first side facing the collimator and a second side facing away from the collimator. A microlens structure is formed on at least one of the two sides of the microlens layer. At least one immersion layer is arranged on the microlens structure.

[0006] DE 10 2007 056 402 A1 relates to an optical component comprising a carrier plate with a first main surface and a second main surface facing away from the first main surface and a first lens structure on the first main surface, wherein the first lens structure has at least a first lens element with a first polygonal shape and a second lens element with a second polygonal shape, the first lens structure completely covers the first main surface and the first lens element and the second lens element are not congruent to each other and / or differ in their orientation on the first main surface of the carrier plate. Description of the invention

[0007] Starting from the known state of the art, it is an object of the present invention to provide an irradiation device and a corresponding method in order to enable advantageous irradiation.

[0008] This problem is solved by an irradiation device having the features of claim 1 and a method having the features of claim 13. Advantageous embodiments are described in the dependent claims, the present description, and the figures.

[0009] Accordingly, an irradiation device is proposed with a radiation unit for emitting radiation in the form of a beam in the temporal integral, comprising a first microlens arrangement downstream of the radiation unit with a plurality of microconverging lenses arranged side by side with respect to the direction of radiation propagation for dividing the beam into a partial beam for each microconverging lens, and a converging lens downstream of the microlens arrangement which superimposes the partial beams in an irradiation surface in the temporal integral, the microconverging lenses being divided into at least a first group and a second group, each with a plurality of microconverging lenses, wherein the irradiation device is preferably configured for variable irradiation of the groups, and wherein the microconverging lenses are identical in each group.However, the microconverging lenses of the first group differ from the microconverging lenses of the second group in at least one aspect of their shape, size, and focal length, such that a first area of ​​the irradiation surface irradiated by the microconverging lenses of the first group differs from a second area of ​​the irradiation surface irradiated by the microconverging lenses of the second group in at least one aspect of its shape and size.

[0010] Preferred embodiments are found in the dependent claims and also in the rest of the disclosure, whereby the presentation does not always differentiate in detail between device and method or use aspects; in any case, the disclosure is to be read implicitly with regard to all claim categories.

[0011] The irradiation device according to the invention advantageously allows variable irradiation of the irradiation surface, e.g., by switching back and forth between beam guidance via the microconverging lenses of the first group (hereinafter also referred to as "first microlenses") and beam guidance via the microconverging lenses of the second group (hereinafter also referred to as "second microlenses"). If, for example, a phosphor element is arranged in the irradiation surface, different areas of it can thus be excited, and the conversion light is then emitted in correspondingly different areas (the emission and excitation areas are essentially congruent in the case of a phosphor element).

[0012] Using optics (in the simplest case, a converging lens), for example, converted light emitted from different areas (of the phosphor element) can be directed in different directions, thus converting the spatial distribution into an angular distribution. A preferred application is, for example, a car headlight, where the switching back and forth can correspond to the change between low and high beams.

[0013] The selection of the irradiation area is achieved by guiding the beam through the corresponding microlenses, which simultaneously homogenizes the distribution of the irradiance across the respective irradiation area. Advantageously, two functions are integrated: the radiation guided through the microlenses of the same group is distributed uniformly within the corresponding irradiation area. Furthermore, as described above, the irradiated area can also be adapted in shape and / or size.

[0014] In preferred embodiments, a phosphor element is arranged in the irradiation area, meaning the irradiation area lies approximately on a side surface of the phosphor element. The homogenization mentioned above can then help prevent, for example, local overheating and thus degradation of the phosphor element. Down-conversion is generally preferred, i.e., the pump radiation is converted into longer-wavelength radiation, preferably visible light. However, a surface light modulator, such as a micromirror array or an LCD or LCOS image sensor, can also be arranged in the irradiation area; homogenization can also help prevent damage in this case.

[0015] In general terms, the "irradiation area" is the intersection of the rear focal plane of the converging lens with all partial beams of light. The rear focal plane of the converging lens lies on the side of the converging lens facing away from the first microlens array (hereinafter also referred to simply as the "microlens array"), meaning that the latter is positioned downstream of it with respect to the direction of radiation propagation. Generally, "downstream" and "front / back focal plane" refer to the direction of radiation propagation along the path from the radiation unit to the irradiation area.

[0016] The shape of the first irradiation area corresponds to the shape of the first microlenses, and that of the second irradiation area corresponds to the shape of the second microlenses, provided the microlenses have the same orientation and the respective partial beams are superimposed (see below for details). For example, in the case of circular microlenses, the corresponding irradiation area is also circular, whereas in the preferred case of rectangular microlenses, it is also rectangular. Viewed in the direction of beam propagation, the microlenses can, for example, have a round, particularly circular, or polygonal shape, such as rectangular, particularly square, or hexagonal.

[0017] Furthermore, the size and focal length of the first / second microlenses determine the size of the first / second irradiation area, whereby the irradiation area increases with the size of the microlenses and decreases with their (increasing) focal length. The smaller a microlens / the greater its focal length, the smaller the divergence of the partial beam, which also reduces the irradiation area (see Figure 3 for illustration and accompanying description). The "size" of a microlens is its aperture; this is considered, for example, as the area of ​​a perpendicular projection of the microlens onto a plane perpendicular to its optical axis (and compared as its "size" to the corresponding value of another microlens). "Same shape" refers, for example, to shapes that can be transformed into one another by translational shift and / or rotation and / or scaling.

[0018] The microlenses can now be divided into at least two groups, meaning they can be categorized and assigned to a specific group. This group assignment generally has no implications for the spatial distribution of the microlenses within the microlens array. Therefore, the microlenses within a group do not necessarily have to be in close proximity to each other, although this may be preferable for the sake of simpler implementation of variable irradiation.

[0019] Each group comprises a plurality of identical microlenses, preferably at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 microlenses, with the number increasing in this order. Possible upper limits are, for example, at most 2,000, 1,500, 1,000, 500, or 250. In addition to the microlenses of the first and second groups, the microlens arrangement may also include further microlenses, generally also microlenses that differ from each other in shape, size, and / or focal length. Preferably, however, the further microlenses are also each assigned to a group, i.e., each microlens is assigned to a group with identical microlenses. There are at least two groups and preferably no more than 20, 15, 10, or 8 groups (increasingly preferred in the order of mention). The lower limits can be, for example, at least 2, 3, 4, or 5 groups.

[0020] The size and shape of each (first / second / subsequent) irradiation area are determined by the irradiance distribution when irradiated via the respective microlenses. By definition, the edge of each irradiance distribution should be located where the irradiance has dropped to half the average irradiance (achieved via the respective microlenses); this definition is preferred, but in general, the edge could also be located, for example, where the irradiance has dropped to 1 / e of the average irradiance.

[0021] The beam emitted by the radiation unit is considered in terms of its time integral because the irradiation device is configured for selective irradiation of the first or second microlenses. The beam is thus the union of a first beam passing through the first microlenses and a second beam passing through the second microlenses, and, if present, further beams from additional microlenses. The microlens array can also be scanned, for example, using a laser scanning method, in which case the beam is integrated over the entire scan field.

[0022] The variable irradiation, for which the irradiation device is preferably designed, can be achieved, for example, electronically by switching individual sources on or off and / or mechanically by moving optical elements, such as by tilting a mirror to change the beam deflection or moving a lens to change the beam expansion (see below for details). The microlens assembly can also be moved relative to the radiation unit (and the other components of the irradiation device), for example, by being subjected to a periodic oscillation (vibration).

[0023] In general, "variable transmission" means that at least the ratio of the radiation power directed through the first microlenses to the radiation power directed through the second microlenses can be changed; preferably, the transmission to at least one of the groups can be completely switched off during operation of the irradiation device; particularly preferably, the transmission can be switched on and off individually for each of the groups. However, variable transmission is not mandatory, as a pattern created by superimposing different irradiation areas can also be of interest in its static form.

[0024] The partial beams are superimposed in the irradiation area of ​​the variable transmission, at least in the time integral; that is, they all have a common intersection in the irradiation area. Preferably, the areas of the irradiation area emitted by each group of partial beams are congruent and thus coincident with the respective irradiation area region. Preferably, the superposition for each group occurs at a single point in time (not only in the time integral), i.e., it is not, for example, rasterized.

[0025] The centers of gravity of the first and second irradiation areas preferably coincide where the optical axis of the converging lens penetrates the irradiation area.

[0026] The microlens arrangement "divides" the beam into partial beams, which converge immediately downstream of the microlenses and are therefore spatially separated from each other, e.g. in the rear focal plane of the microlens arrangement; downstream of the rear focal plane, an overlap of the partial beams is then possible again.

[0027] In general, within the scope of this disclosure, the term "lens" refers to a transparent body with at least one curved refractive surface, which is preferably an outer surface of the body; the opposite outer surface can generally also be, for example, planar. The curved refractive surface of a microlens is preferably parabolic; the refractive surface of the downstream converging lens is preferably aspherical.

[0028] The converging lens can generally also be, for example, a lens system composed of a plurality of individual lenses (arranged one after the other). Preferably, however, the converging lens is a single lens in which the light-intake and light-outtake surfaces are preferably curved.

[0029] The lenses of the microlens arrangement are arranged "side by side" with respect to the direction of beam propagation, i.e., in a sense, parallel to each other; this means that radiation passing through one microlens is reflection-free, i.e., excluding backscattering and the like, and does not pass through any other microlens. Preferably, the microlenses lie in a common plane (each with the vertex of its respective refractive surface), on which the optical axis of the converging lens / the optical axes of the microlenses are perpendicular.

[0030] In this context, the optical axis of a rotationally symmetric lens is considered to be the axis to which the symmetry relates. Preferably, the microlenses of the microlens arrangement each have an optical axis; more preferably, these optical axes are parallel to each other. Preferably, the converging lens has an optical axis; more preferably, the optical axis of the converging lens is parallel to the (mutually parallel) optical axes of the microlens arrangement.

[0031] The radiation preferably strikes the microlens array in a collimated state. Generally, the radiation is preferably laser radiation, meaning the radiation unit is a laser unit. The radiation unit can preferably be composed of a plurality of radiation sources, for example, at least 2, 3, 4, 5, 6, 7, 8, 9, or 10 radiation sources, with possible upper limits being approximately 1,000, 800, 600, 400, 200, 100, or 50, respectively. The radiation sources can (at least in groups) emit radiation of different dominant wavelengths; preferably, they emit radiation of the same wavelength, and most preferably, they are identical in construction.

[0032] A light-emitting diode (LED) can be used as the radiation source, although a laser diode is preferred. Particularly preferably, a plurality of laser diodes arranged in an array form the radiation unit. More preferably, a collimated laser beam can then be directed onto the microlens arrangement from each laser diode, with the laser beams incident parallel to each other.

[0033] This example illustrates that the "beam" does not necessarily have to be continuous (despite the temporal integration), but can also be divided into sub-beams upstream of the microlens array. A plurality of sub-beams (laser beams) can then fall on the microlens array for each group, see Figure 2 for illustration. A sub-beam should preferably fall on at least 5, 10, or 15 microlenses (increasingly preferred in the order of mention); possible upper limits could be, for example, a maximum of 200, 150, or 100 microlenses. At least 20, 40, or 50 microlenses should preferably be irradiated through each group (increasingly preferred in the order of mention); possible upper limits could be, for example, a maximum of 2500, 1250, or 500 microlenses. Overall, the beam should preferably have at least 40, 80, or 50 microlenses.100 microlenses are used (increasingly preferred in order of mention); possible upper limits could be, for example, a maximum of 5000, 2500 or 1000 microlenses.

[0034] In a preferred embodiment, the microlenses of at least one of the groups have the same orientation; preferably, this applies to the microlenses of all groups (i.e., the microlenses in each group have the same orientation relative to each other). "Same orientation" means that they can be aligned solely by a translational shift. The areas of the irradiation surface that are irradiated by microlenses of the same orientation (and the same group) are congruent and correspond to the respective irradiation surface area (see above).

[0035] In a preferred embodiment, the microlenses of at least one of the groups, preferably the first and second groups, and particularly preferably all groups, have a rectangular shape. This refers to a top view, i.e., a view along the optical axis of the respective microlens. The side edges of each rectangle are preferably in a ratio (from shorter to longer side edge) of at least 1:10, increasingly preferably at least 1:8, 1:6, 1:4, 1:2, or 2:3, and square microlenses are particularly preferred.

[0036] In a preferred embodiment, the first and second microlenses differ (at least) in size, with the smaller microlenses being in a size ratio to the larger ones of, in this order, increasingly preferably at least 1:100, 1:80, 1:60, 1:40, 1:20, and 1:10, respectively. Advantageous upper limits may, for example, be, in this order, increasingly preferably at most 9:10, 4:5, 7:10, 3:5, and 1:2. The provision of an upper limit may also be of interest independently of the provision of a lower limit (and vice versa) and is to be disclosed in this form as well.

[0037] In a preferred embodiment, the first and second microlenses differ only in size, i.e., they have the same shape. If present, the microlenses of any further group(s) also have the same shape. A rectangular shape is particularly preferred.

[0038] In a preferred embodiment, the microlenses of at least one of the groups are parabolic, which in this context refers to the curvature of the refractive surface of the lens. Preferably, the first and second (and any further) microlenses are parabolic, and more preferably with the same radius of curvature. If the first and second microlenses differ, for example, in size, the sag (height of the spherical segment) is greater for the larger microlenses than for the smaller ones. The use of parabolic microlenses can advantageously reduce the complexity of designing a microlens arrangement.

[0039] In a preferred embodiment, the first microlenses are arranged in a first segment and the second microlenses in a second segment, the first being enclosed by the second segment, so that the second microlenses extend around the first like a frame. This refers to a top view of the microlens arrangement along the optical axes of the microlenses. With respect to the directions perpendicular to these optical axes, the first is enclosed by the second segment; thus, for each first microlens, at least one second microlens should extend outwards in each of the directions perpendicular to its optical axis, typically several in each direction perpendicular to the optical axis.

[0040] Preferably, microlenses with smaller irradiation areas—that is, those that are smaller and / or have a longer focal length—are positioned centrally. Since the irradiation area is smaller, the radiation power delivered via the corresponding microlenses will generally be lower. Accordingly, for example, more radiation sources can be assigned to the outer microlenses than to the inner ones. If the radiation sources are arranged in an array, the radiation sources assigned to the outer microlenses can be distributed more effectively around the few radiation sources assigned to the inner microlenses than vice versa.

[0041] In the case of a further group(s), their microlenses can also be arranged (each) in a segment, with the segments then preferably being nested within each other. Thus, a third segment encloses the first two, and (if present) a fourth segment encloses the first three, and so on.

[0042] In preferred embodiments, the term "microlens arrangement" can generally refer to microlenses whose relative positions are fixed. Preferably, the microlens arrangement is a single piece, meaning the microlenses cannot be separated from one another without damage (e.g., they are glued together). Particularly preferred is a monolithic microlens arrangement, formed from a single material without internal material boundaries. In principle, such a microlens arrangement can also be formed by material removal (e.g., by grinding); however, for mass production purposes, manufacturing by casting into a mold is preferred, meaning the microlens arrangement is an injection-molded part.

[0043] The microlens arrangement is not necessarily monolithic; alternatively, a microlens arrangement in which the first microlenses are movably mounted relative to the second (and vice versa) may also be of interest. Within each group, the microlenses are preferably fixed in their relative position to one another. The microlens arrangement can then preferably consist of several (corresponding to the number of groups) multi-part components, each containing the microlenses of one group and preferably being monolithic in the aforementioned sense.

[0044] In conjunction with the previously described variant "second microlenses enclosing first microlenses," the first group can, for example, be rotatably held within the second. However, the groups can also be displaced relative to each other in a direction of movement perpendicular to the (mutually parallel) optical axes of the microlenses. An advantageous application of the irradiation device with (groups of) relatively movable microlenses relative to each other can be found, for example, in the field of effect lighting.

[0045] In this respect, among others, moving the entire microlens arrangement relative to the rest of the irradiation device may also be of interest, such as rotating, preferably around an axis of rotation parallel to the optical axes of the microlenses, shifting and / or vibrating, i.e., a periodic movement.

[0046] In general, the microlenses can be relatively mobile relative to each other perpendicular to their (mutually parallel) optical axes, not just in groups. The microlens arrangement can be fanned out, meaning the distances between the microlenses can be increased. For example, the number of microlenses through which light passes can be changed by fanning out some of them and moving them out of the illuminated area. For this purpose, the microlenses can be embedded in a flexible and therefore deformable matrix material, perhaps as individual lenses between which at least optically functional cavities (without microlenses) are created. As described earlier, by varying the irradiation of the surface, for example in the case of a phosphor element arranged there, a radiation pattern with varying spatial distribution can be generated, which can be converted into an angular distribution using optics.The relative movement of the microlenses can therefore create an excitation pattern which can be used for effect lighting that varies in different spatial directions.

[0047] In general, an irradiation device with such a microlens arrangement, where the microlenses are relatively movable (in groups), could even be of interest if the irradiance falling on each group remains constant during operation. The movement within the microlens arrangement alone can generate varying irradiation.

[0048] In a preferred embodiment, the irradiation device is configured such that the ratio of the first irradiance (falling on the first microlenses) to the second irradiance (falling on the second microlenses) can be changed during operation. Preferably, the irradiation of at least one of the groups can be completely switched off (and switched back on) during operation. The ratio of the first to the second irradiance is considered as a time average. The irradiance can, for example, also be adjusted by pulse-width modulation; the time average is then calculated over the smallest possible period.

[0049] The irradiation unit can comprise a first radiation source, the radiation of which passes through the first microlenses to a greater extent, and a second radiation source, the radiation of which passes through the second microlenses to a greater extent (preferably, only the first or second microlenses are irradiated). The irradiation device is then preferably configured such that a change in the radiation power of the first radiation source results in a change in the radiation power of the second radiation source, preferably independently, if only with a linear or non-linear proportionality constant (m ≠ 1).

[0050] In preferred embodiments, the irradiance ratio can therefore be achieved via the average output power of the individual radiation sources in the case of a radiation unit composed of several radiation sources. For example, in the case of an array of laser diodes, each emitting collimated laser radiation in parallel sub-beams, the irradiance ratio can be varied even with an unchanged opening angle (e.g., 0°).

[0051] On the other hand, the irradiation device can also be configured such that the opening angle, which results from the volume filled by the radiation immediately in front of the microlens array, can be changed. The union of the volumes filled by the radiation corresponds to the beam; the volumes are therefore subsets of the latter. The volume, and thus the opening angle, is determined by the full width at half maximum (FWHM). The opening angle can be varied at least with respect to a cross-sectional plane intersecting the microlens array parallel to the optical axes of the microlenses, and preferably with respect to all cross-sectional planes (for example, in the case of a cone that can be expanded and contracted).

[0052] In the case of a small opening angle, for example in nested groups (see above for details) only the inner microlenses can be penetrated, and the expanded radiation can then fall on both the first and the second microlenses.

[0053] The previously mentioned "phosphor element" can be a static phosphor element, such as a phosphor plate. Alternatively, the phosphor element can also be moving, for example around an axis of rotation, such as a phosphor roller or, preferably, a phosphor wheel. In this case, the axis of rotation is preferably stationary relative to the rest of the irradiation device.

[0054] In a preferred embodiment, the irradiation device additionally comprises a second microlens arrangement, which is also composed of a plurality of adjacent microlenses. These microlenses are intended to correspond to the microlenses of the first microlens arrangement with respect to their size, shape, and relative arrangement to one another (within the respective microlens arrangement), and preferably also with respect to their focal length (see below for details), and are arranged between the latter and the converging lens with respect to the direction of radiation propagation. The microlenses of the first and second microlens arrangements are intended to "interact in pairs," meaning that each partial beam of radiation (which by definition is assigned to exactly one microlens of the first microlens arrangement) should pass through exactly one microlens of the second microlens arrangement.Two microlenses of the first and second microlens arrangements that interact accordingly are referred to as a "microlens pair".

[0055] For each pair of microlenses, it is preferred that the rear microlens is arranged in the rear focal plane of the front microlens and / or the front microlens is arranged in the front focal plane of the rear microlens; both are particularly preferred. Where statements are made regarding a pair of microlenses, this preferably applies to at least all microlenses of a group, more preferably to all microlenses attributable to a group, and most preferably to all microlenses of both arrangements. The advantage of two microlens arrangements connected in series (hereinafter also referred to as "dual microlens arrangement") can, for example, lie in an increased tolerance to tilted incident radiation. Within certain limits, tilted incident radiation can still be superimposed perfectly in the irradiation area (provided the microlenses are identical).

[0056] For example, in the case of collimated laser radiation (e.g., several individually collimated laser beams), a maximum tilt of no more than 3° may be preferred for a single microlens arrangement, with no more than 2° being further preferred and no more than 1° being particularly preferred (the tilt is taken relative to the parallel optical axes of the microlenses). Although collimated radiation incident parallel to the optical axes may also be preferred in the case of a dual microlens arrangement, the tolerance for tilt is increased; the latter should, for example, not exceed 15°, and in this order increasingly preferably not exceed 13°, 11°, 10°, 9°, 8°, 6°, or 5°.

[0057] Regarding the microlens pairs again: It can be advantageous for the microlens pairs of the different groups to have the same length. The length of a microlens pair is measured from the entrance surface of the microlens of the first arrangement to the exit surface of the microlens of the second arrangement. If the microlens pairs have the same length, this can, for example, simplify manufacturing, such as demolding an injection-molded part.

[0058] On the other hand, microlens pairs of different lengths can also be of interest, for example, microlens pairs that have the same length within each group, but different lengths between groups. In conjunction with the aforementioned requirement that the rear focal plane of the front microlens in each pair coincides with that of the rear microlens, and its front focal plane coincides with that of the front microlens, the microlens pairs of different lengths then also have different focal lengths.

[0059] In other words, by using microlens pairs of different lengths, the focal length of the microlens pairs in each group can be selected to achieve the desired size of the irradiation area. For example, to achieve the smallest possible irradiation area, the size of the microlenses can be chosen to be small; however, a certain minimum size may be necessary for manufacturing reasons. To further reduce the irradiation area, the focal length can then be increased. This also applies to an irradiation device with only a first microlens arrangement. If a second microlens arrangement is provided, the length of the microlens pairs with the longer focal length is preferably increased accordingly to ensure that the preferred focal plane condition is still met.

[0060] In general, the information disclosed above for the first microlens arrangement shall also apply to the second microlens arrangement, particularly regarding the preferred arrangement of the microlenses in a plane and their preferably one-piece / monolithic design. The first and second microlens arrangements may be composed of multiple parts and preferably spaced apart by an air gap. For example, a flat exit surface of the first microlens arrangement, opposite its curved entrance surface, may face a flat entrance surface of the second microlens arrangement (spaced apart by the air gap), and the curved light exit surface of the second microlens arrangement may face the flat entrance surface of the second microlens arrangement.

[0061] However, the first and second microlens arrays can also be formed as a single piece, preferably monolithically, for example as an injection-molded part. The microlenses of the first microlens array are then shaped as a curved surface on the inlet side of this monolithic part, and the microlenses of the second microlens array on the outlet side.

[0062] In a preferred embodiment, the rear focal planes of the microlenses lie in a common plane, and this "rear focal plane" of the microlens arrangement coincides with the front focal plane of the converging lens. Downstream of the converging lens, the partial beams of light are then collimated separately. In the case of a double microlens arrangement, the refractive surfaces of the second microlens arrangement facing the converging lens preferably lie in this plane, ideally touching the plane at their vertices.

[0063] In a preferred embodiment, which relates in particular to a simple microlens arrangement, the first microlens arrangement is provided on the entrance side of a base body, i.e., formed in its entrance surface. Each of the microlenses has a focus, and this focus should preferably be located outside the base body, and more preferably outside transparent optical elements in general, i.e., also outside the converging lens. The foci of the individual microlenses are then preferably located between the exit surface of the base body and the converging lens. Such focusing can, for example, prevent excessive power input into the base body or the converging lens and thus prevent overheating.

[0064] As already mentioned at the outset, the invention also relates to a method for operating an irradiation device disclosed herein. In this method, the first group of microlenses is irradiated with a first irradiance and the second group with a second irradiance, the ratio of the first to the second irradiance being varied in order to vary the irradiance accordingly in the respective irradiation area regions.

[0065] The first and / or second irradiance can also be set to zero, meaning that, for example, the system can switch back and forth between irradiating the first and second microlenses. Alternatively, it may be preferable to have one group continuously irradiated and the other switched on as needed; the irradiance on the microlenses of the continuously irradiated group can also be adjusted, for example, reduced when the other group is switched on, so that the overall irradiance is kept constant.

[0066] The invention also relates to the use of a irradiation device disclosed herein for motor vehicle exterior lighting, in particular for variable road illumination with a headlight. Advantageous applications may also lie in the field of effect lighting; on the other hand, the irradiation device can also serve for operating field illumination, where variably adjustable irradiation may also be of interest. The irradiation device can furthermore be used as a light source for a projection device, endoscope, or stage spotlight, for example for scene lighting in film, television, or theater. Brief description of the drawings

[0067] The invention will now be explained in more detail using exemplary embodiments, whereby the individual features within the scope of the dependent claims may also be essential to the invention in other combinations; furthermore, no distinction will be made between the different claim categories.

[0068] In detail, it shows 1 an irradiation device according to the invention in a schematic, partly cutaway side view; 2a, b schematic side views with microlenses of different sizes to illustrate the correspondingly different irradiation area areas; 3 a microlens arrangement of an irradiation device according to the invention in top view with several schematically shown laser spots; 4 a preferred beam path in the case of a simple microlens arrangement; 5 a diagram to illustrate the irradiance profile in the irradiation area as a function of the focal length. Preferred embodiment of the invention

[0069] Figure 1 shows a schematic side view of an irradiation device 1 according to the invention. The irradiation device 1 has a plurality of laser diodes 2 (in this case 16 laser diodes) as a radiation unit, whereby, for the sake of clarity, the beam propagation in Figure 1 is not shown and reference is made to the following figures.

[0070] Each laser beam emitted by one of the laser diodes 2 is collimated by a collimation lens 3. Downstream of the collimation lenses 3, the laser beams then fall onto a microlens arrangement 4, shown in cross-section. The microlenses 4 of this arrangement can be divided into a first group with small microlenses 4a and a second group with larger microlenses 4b. Within each group, the microlenses 4 are identical, meaning they have the same focal length (the same radius of curvature), the same size, and the same shape.

[0071] As explained in more detail in Figure 2, the differently sized first 4a and second microlenses 4b can be used to irradiate differently sized areas of an irradiation surface 5. As shown in Figure 1, a phosphor element 6 is arranged in the irradiation surface 5 (not shown in Figure 2). The radiation emitted by the laser diodes 2 is thus used as pump radiation to excite the phosphor element 6. If different areas of the phosphor element 6 are excited, the conversion light emitted in response to this excitation will also be emitted from different areas.

[0072] The fluorescent element 6 can, for example, be operated in transmission mode, and an imaging optic (not shown) can then be provided downstream of the fluorescent element 6 with respect to a direction of radiation propagation 7, which converts the spatial distribution (of the conversion light emission) into an angular distribution. The conversion light emitted at different locations is thus directed in different spatial directions.

[0073] The radiation from the first microlens array 4 is guided through a second microlens array 8, wherein the microlenses 8 of the second array are arranged in pairs corresponding to the microlenses 4 of the first array in size, shape, and focal length. The microlenses 4 and 8 are arranged such that each microlens 4 of the first array forms a functional pair with exactly one microlens 8 of the second array. The microlenses 4 of the first array subdivide a beam incident on the microlens array 4 into partial beams, with each of the partial beams then passing through exactly one microlens of the second microlens array 8 (namely, that of the respective functional pair). The beam array is the entirety of all laser beams.

[0074] A converging lens 9, located downstream of the second microlens arrangement 8, superimposes the partial beams in the irradiation area 5; the irradiation area 5 lies in the rear focal plane of the converging lens 9.

[0075] Figures 2a and 2b illustrate such partial beams 20a and 20b for the smaller microlenses 4a and 8a (2a) and for the larger microlenses 4b and 8b (2b). For clarity, only the partial beams 20a and 20b from two of the microlenses 4a, 8a, 4b, and 8b, which are actually provided in multiples, are shown. Since this setup refers to two microlens arrangements 4 and 8 with paired, functionally interacting microlenses, the following discussion refers to a respective partial beam 20a and 20b of a respective microlens pair 4 and 8 and the size, shape, and focal length of the microlens pair 4 and 8.

[0076] In each sub-area 21a, b of the irradiation area 5, the respective partial beams 20a, b are superimposed. Thus, each of the microlens pairs 4, 8 irradiates the entire respective irradiation area 21a, b. In conjunction with the superposition, uniform irradiation is achieved.

[0077] In this case, the microlens pairs 4, 8 are arranged in the front focal plane of the converging lens 9, and the partial beams 20a, b are each collimated separately. Thus, in the irradiation area 5, separately collimated, tilted partial beams 20a, b are superimposed.

[0078] In general, the arrangement of the microlens pairs 4, 8 in the front focal plane of the converging lens 9 is not mandatory; the respective partial beams 20a, b of the microlens pairs 4, 8 of each group would also be superimposed in the irradiation area 5 if the microlens pairs 4, 8 were offset from the front focal plane of the converging lens 9. If they were moved closer to the converging lens 9, the partial beams 20a, b would be divergent downstream of the converging lens 9; conversely, they would be convergent if the microlens pairs 4, 8 were located outside the front focal length of the converging lens 9.

[0079] Depending on whether the irradiation occurs via the microlens pairs 4a, 8a of the first group (2a) or via the microlens pairs 4b, 8b of the second group (2b), the irradiated area 21a, b is smaller or larger. The size of the irradiated area can therefore be adjusted by selecting the microlens pairs 4, 8 through which the radiation passes. For the sake of clarity, only two groups of microlens pairs 4, 8 of different sizes are shown here; however, in practice, there can be significantly more than two groups.

[0080] Figure 3 shows the microlens arrangement 4 in a top view, looking along the propagation direction 7 of the laser radiation. The microlenses 4a, b of different sizes are visible. Furthermore, essentially circular irradiation areas 31 are indicated, each marking the area of ​​the microlens arrangement 4 irradiated by a respective laser diode 2. The laser beams emitted by each laser diode 2 are individually collimated, parallel to each other, and propagate perpendicular to a common mounting surface of the laser diodes 2 (the laser diodes 2 are mounted in this flat mounting surface). The arrangement of the irradiation areas 31 corresponds to the arrangement of the laser diodes 2.

[0081] Each of the laser diodes 2 is assigned to exactly one group of microlenses 4 (the microlens pairs 4, 8), thus illuminating exclusively microlenses 4 of the same size. The four inner laser diodes 2 illuminate the small, first microlenses 4a, whereas the twelve outer laser diodes 2 illuminate the second, larger microlenses 4b.

[0082] A control / driver electronics unit can be designed to supply the outer 16 laser diodes 2 as one group and the inner four laser diodes 2 as another group. The output power of the laser diodes in one group can be set independently of that of the laser diodes in the other group; however, within a group, the output power of each laser diode 2 is the same.

[0083] In a first operating state, for example, only the four inner laser diodes 2 can be operated, and accordingly, the small microlenses 4a are illuminated. This means that the first, small irradiation area 21a of the irradiation surface 5 is irradiated, i.e., a small part of the phosphor element is excited. If, in another operating state, for example, only the twelve outer laser diodes 2 are operated, the second microlenses 4b are illuminated, and thus the correspondingly larger irradiation area 21b of the irradiation surface 5 is irradiated.

[0084] As an alternative to the arrangement shown in Figure 3, in the case of another group or groups of microlenses, the outer area supplied by the twelve laser diodes could be further subdivided, for example into rectangles formed by extending the side edges of the central rectangle (not shown). The rectangles above and below, as well as to the left and right of the central rectangle, would then each be supplied with two laser diodes 2, and the rectangles at the corners with each one laser diode 2.

[0085] The second microlenses 4b and the further group(s) can then be distributed across the rectangles according to power requirements, whereby rectangles with microlenses 4 of the same group do not have to be adjacent to each other.

[0086] One advantage of providing microlens pairs 4, 8, i.e., the second microlens arrangement 8, can be, for example, a certain tolerance for tilted incident radiation. The optical axes of the microlens pairs 4, 8 are parallel to the optical axis 10 of the converging lens 9, but for the sake of clarity, they are not shown in detail (see Figure 1 for illustration). Ideally, the laser beams of the laser diodes 2 are parallel to the optical axes of the microlens pairs 4, 8. However, if a tilt occurs, for example, due to manufacturing, the respective partial beam bundles 21a, b of each group can still be superimposed, provided the tilt does not exceed an acceptable angle of the microlens pairs 4, 8.

[0087] Within the acceptance angle range, the microlens 4a, b of the first arrangement focuses on the microlens 8a, b of the second arrangement that is part of the respective microlens pair 4, 8. Outside the acceptance angle range, the radiation also falls on other microlenses 8, and ghost images can occur.

[0088] In general, however, the provision of microlens pairs 4, 8 is not mandatory. For example, in the case of incident radiation parallel (to the optical axes of the microlenses 4a, b), a single microlens arrangement 4 can also superimpose the respective partial beams 20a, b of each group in the irradiation area 5 (together with the converging lens 9).

[0089] Figure 4 shows such a simple microlens arrangement 4 in a schematic section. The microlenses 4a, b are shaped on the entrance side of a base body 41. Its exit side 42, opposite the microlenses 4a, b, is planar. The downstream converging lens and the phosphor element are not shown for clarity; reference is made to the setup according to Figures 1 and 2 and the associated description.

[0090] The base body 41 is chosen in its length in the direction of radiation propagation 7 such that the foci 43 lie outside the base body 41, i.e., the partial beams 20 are focused downstream of the base body 41. This prevents, for example, excessive radiation from entering the base body 41.

[0091] Figure 2 illustrates the influence of the size of the microlenses 4a, b or microlens pairs 4, 8 on the size of the irradiated area 21a, b of the irradiation surface 5. The larger the microlenses 4a, b, the greater the divergence and, consequently, the larger the irradiated area.

[0092] The size of the respective irradiation area 21a, b can alternatively, or in combination with, an adjustment via the focal length. The shorter the focal length of the microlenses 4a, b, the greater the divergence and, consequently, the larger the irradiation area 21a, b.

[0093] Figure 5 illustrates the irradiance profile across the irradiation area (based on results from ray-tracing simulations performed on a simple microlens array). The microlenses (including those of the two groups relative to each other) have the same size and, in a reference case (Graph I), also the same focal length.

[0094] The three further graphs II-IV then illustrate how the irradiance distribution changes when the focal length of the first, inner microlenses 4a is changed (the groups are arranged in a comparable manner). With increasing focal length, the divergence of the partial beams 20a passing through the first microlenses 4a decreases. Accordingly, the area 21a of the irradiation surface 5 irradiated by the first microlenses 4a becomes smaller. A plateau forms in the center of the irradiation surface 5, the width of which decreases with increasing focal length. The radiation power directed through the first microlenses 4a is kept constant, which is why the irradiance increases with decreasing width. A change in the irradiance distribution that is essentially comparable could also be achieved, for example, by varying the size of the microlenses, i.e., by reducing the size of the first, inner microlenses 4a.

[0095] Regarding the small / large microlenses 4a, b according to section 3: The arrangement such that the large microlenses 4b surround the small ones 4a can offer advantages insofar as more laser diodes 2 can be provided and better arranged for irradiating the larger irradiation area 21b. However, if the arrangement were reversed, i.e., the large microlenses in the middle and the small ones on the outside, this would have no effect on the arrangement / position of the irradiation areas 21a, b. The small irradiation area 21a would still lie within the large irradiation area 21b.

Claims

[1] Irradiation device (1) with: a radiation unit (2) for the emission of radiation in the form of a beam of radiation in the temporal integral, a first microlens arrangement (4) downstream of the radiation unit (2) with a plurality of microconverging lenses (4a, b) arranged side by side in a common plane with respect to the direction of radiation propagation for dividing the beam into a partial beam (20a, b) for each microconverging lens (4a, b), and a converging lens (9) downstream of the microlens arrangement (4), which superimposes the partial beams (20a, b) in the temporal integral in an irradiation surface (5), wherein the microconcentrating lenses (4a, b) of the first microlens arrangement (4) are divided into at least a first group and a second group, each with a plurality of microconcentrating lenses (4a, b), wherein the microconverging lenses (4a, b) are identical in each group, but the microconverging lenses (4a) of the first group differ from the microconverging lenses (4b) of the second group in at least one aspect of their shape, size and focal length, such that a first area (21a) of the irradiation surface (5) irradiated by the microconverging lenses (4a) of the first group differs in at least one aspect of its shape and size from a second area (21b) of the irradiation surface (5) irradiated by the microconverging lenses (4b) of the second group; in which the microconcentrating lenses (4a) of the first group are irradiated with a first irradiance and the microconcentrating lenses (4b) of the second group are irradiated with a second irradiance, wherein the irradiation device (1) is configured to vary the ratio of first irradiance to second irradiance. [2] Irradiation device (1) according to claim 1, in which the microconverging lenses (4a, b) of at least one of the groups have the same orientation, i.e. can be transformed into one another by a displacement. [3] Irradiation device (1) according to claim 1 or 2, wherein the microconverging lenses (4a, b) of at least one of the groups have a rectangular shape. [4] Irradiation device (1) according to one of the preceding claims, wherein the microconcentrating lenses (4a) of the first group differ in size from the microconcentrating lenses (4b) of the second group, the small microconcentrating lenses (4a, b) being in a size ratio of at least 1:100 and at most 9:10 to the large microconcentrating lenses (4a, b). [5] Irradiation device (1) according to one of the preceding claims, wherein the microconcentrating lenses (4a) of the first group differ from the microconcentrating lenses (4b) of the second group only in their size. [6] Irradiation device (1) according to one of the preceding claims, wherein the microconverging lenses (4a, b) of at least one of the groups are parabolic, preferably the microconverging lenses (4a) of the first group and the microconverging lenses (4b) of the second group are parabolic and particularly preferably have the same radius of curvature. [7] Irradiation device (1) according to one of the preceding claims, in which in the first microlens arrangement (4) the microconcentrating lenses (4a) of the first group are arranged in a first segment and the microconcentrating lenses (4b) of the second group are arranged in a second segment, wherein the first segment is enclosed by the second segment. [8] Irradiation device (1) according to one of the preceding claims, in which in the first microlens arrangement (4) the microconverging lenses (4a) of the first group are movably mounted relative to the microconverging lenses (4b) of the second group. [9] Irradiation device (1) according to claim 8, in which the radiation of the first microlens arrangement (4) has an opening angle immediately in front of it and the irradiation device (1) is configured to change the opening angle and thus the irradiance ratio. [10] Irradiation device (1) according to one of the preceding claims with a second microlens arrangement (8) with a plurality of adjacent microconverging lenses (8a, b) which correspond with respect to their size, shape and relative arrangement to each other to the microconverging lenses (4a, b) of the first microlens arrangement (4), wherein the second microlens arrangement (8) is arranged downstream of the first microlens arrangement (4) and upstream of the converging lens (9) such that the microconverging lenses (4a, b) of the first microlens arrangement (4) interact in pairs with those of the second microlens arrangement (8). [11] Irradiation device (1) according to one of the preceding claims, in which a rear focal plane of the first microlens arrangement and the front focal plane of the converging lens (9) coincide. [12] Irradiation device (1) according to one of claims 1 to 10, in which the first microlens arrangement (4) is provided on the entry side of a base body (41), the exit side of which opposite the entry side is planar (42), wherein the microconverging lenses (4a, b) each have a focus (43) which lies outside the base body (41), preferably in front of the converging lens (9). [13] Method for operating an irradiation device (1) according to one of the preceding claims, in which the microconcentrating lenses (4a) of the first group are irradiated with a first irradiance and the microconcentrating lenses (4b) of the second group are irradiated with a second irradiance, wherein the ratio of first irradiance to second irradiance is varied. [14] Use of an irradiation device (1) according to any of the preceding claims for motor vehicle exterior lighting, effect or operating field lighting or as a light source for a projection device, endoscope or stage spotlight.

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