Lighting system for illuminating a scene, detection system, method and lidar system

Abstract

Lighting system (100) for illuminating a scene (40), comprising: at least one light source (10), a first diffuser (110) with a first microlens array (112) arranged on a first surface (111) of the first diffuser (110), wherein the first microlens array (112) is configured to widen a beam of light (11) emittable by the light source (10) in a principal emission direction (250) of the light source (10) in a first direction (210) and / or to achieve a desired first intensity distribution in the first direction, a second diffuser (120), which is arranged in the beam path downstream of the first diffuser (110), with a second microlens array (122) arranged on a second surface (121) of the second diffuser (120), wherein the second microlens array (122) is configured to widen the emittable beam (11) in a second direction (220) and / or to achieve a desired second intensity distribution in the second direction, wherein the first direction (210) and second direction (220) are different from each other, and wherein the illumination system is free of further optical elements

Description

[0001] The invention relates to a lighting system, a detection system, a method, and a lidar system.

[0002] Lidar scanners are used for non-contact distance measurement. A laser pulse is emitted, and the travel time of the reflected signal is determined. To measure over a larger area, the laser beam must either be widened (flash lidar) or deflected (scanning lidar).

[0003] Deflecting the laser beam is mechanically much more complex, but requires less laser power. Therefore, the laser beam expansion must be achieved so that the resulting illumination of the scene optimally matches the desired measurement area. Because scanning lidar systems achieve laser beam deflection via a movable mirror, they can scan an adjustable measurement area.

[0004] Flash lidar scanners operate with a laser beam that is widened by optics. Besides its simpler mechanical design, flash lidar offers the advantage that the scene doesn't need to be scanned piecemeal, but can be illuminated with a single light pulse. This allows for particularly fast measurements. However, this short light pulse must also contain a correspondingly high power to adequately illuminate the entire scene. This may necessitate the selection of a laser category with stricter safety requirements, which can result in higher costs.

[0005] In both flash lidar and scanning lidar, the time of flight of the reflected light is measured after a beam of light is emitted. Detection systems using a SPAD array for time-of-flight detection are known, for example, from DE 10 2019 131 001 B3 and DE 10 2019 131 000 B3, respectively. A disadvantage of these lidar systems is their less effective illumination of the scene.

[0006] A radiation-emitting device is known from DE 10 2021 100 663 A1. A disadvantage is that three optical elements are required.

[0007] Optical elements such as collimators, filters, or diffusers can be used to expand the light beam. However, these sometimes offer only insufficient control over the expansion of the beam.

[0008] From EP3561553 a laser arrangement with reduced scattering loss is known in which a diffuser with a wave-like surface structure is used.

[0009] It is an object of the present invention to at least partially overcome the aforementioned disadvantages known from the prior art. In particular, it is an object of the present invention to provide a lighting system, a method, and a lidar system in which the illumination of the scene is precisely adjustable, energy consumption is reducible, and safety is guaranteed at all times, while reducing the mechanical design effort and costs.

[0010] The foregoing problem is solved by a lighting system with the features of claim 1, a method with the features of claim 16, and a lidar system with the features of claim 17. Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details described in connection with the lighting system according to the invention naturally also apply in connection with the method and / or the lidar system according to the invention, and vice versa, so that the disclosure relating to the individual aspects of the invention always makes, or can make, reciprocal references.

[0011] According to a first aspect of the invention, a lighting system for illuminating a scene is provided, comprising at least one light source, a first diffuser with a first microlens array arranged on a first surface of the first diffuser, wherein the first microlens array is configured to widen a beam emittable by a light source in a principal emission direction in a first direction and / or to achieve a desired first intensity distribution in the first direction, a second diffuser which is arranged in the beam path after the first diffuser, with a second microlens array arranged on a second surface of the second diffuser, wherein the second microlens array is configured toTo widen the emittable beam in a second direction and / or to achieve a desired second intensity distribution in that direction, where the first and second directions differ from each other. The desired first or second intensity distribution can be a predefined intensity distribution, for example, using an optical design tool such as a ray tracing program. Widening can be understood as increasing the divergence of the light beam. Both effects can be achieved simultaneously. For example, an asymmetric light distribution can be created while simultaneously widening the beam.

[0012] Illumination, as defined in the invention, refers to lighting, specifically a type of planar irradiation with electromagnetic radiation, particularly visible light. Further details relating to the light source are described below. The illumination, as described in the invention, is achieved by reflecting light back from the objects in the scene so that it can be detected by a sensor. In the following description, reflection is used to mean any physical mechanism that results in the emitted beam of light being at least partially reflected back.

[0013] A scene can be any location within the illuminated area. Typically, the lighting system is used to illuminate objects within the scene and thus determine their distance. However, it's also possible that no objects are present in the scene. Even the information that no objects are within the range of a lighting system can be insightful for a given application.

[0014] In the context of the invention, a diffuser (sometimes also referred to as a scattering disc) is understood to be a device suitable for scattering incident light so that the light passing through the diffuser is emitted over a wider solid angle than would be the case without the diffuser. In particular, this includes devices in which diffuse reflection is used to widen the incident beam, as well as those in which the refraction of light is used to widen the incident beam, and any combination thereof.

[0015] In one advantageous embodiment, a light source can be arranged at a specific distance from the first microlens array. In another equally advantageous embodiment, the light source can be arranged directly on the first microlens array, i.e., without an air gap. In the latter case, an optical cement or a gel with a suitable refractive index can be provided to bridge any gap between the light source and the first diffuser. This prevents reflection losses.

[0016] In the context of the invention, the terms "first" and "second diffuser" can be understood as referring to their spatial arrangement in a principal emission direction of the light source. Accordingly, in the principal emission direction of the light source, the first diffuser is arranged first, followed by the second diffuser. However, it is also conceivable that further diffusers are arranged, even between the first and second diffusers, or in front of or behind them. When diffusers are mentioned below, this may refer to the first, the second, or any further diffusers. Although in an advantageous embodiment exactly two diffusers may be provided, in a further embodiment more than two diffusers may be provided one after the other in the beam path.

[0017] The first and second surfaces of the first and second diffusers, respectively, refer to surfaces of the first and second diffusers through which the light beam passes. While each of the first and second diffusers has two surfaces through which the light beam passes, which of these at least two surfaces is equipped with a microarray is irrelevant to the basic function of the illumination system. Particularly advantageous arrangements of the microlens arrays and improvements to the surfaces will be discussed separately below.

[0018] In an advantageous embodiment, the light beam emitted by the light source can exhibit divergence. In another embodiment, the light beam emitted by the light source can be a collimated light beam. The main emission direction of the light source can be considered to be the center beam of the emitted light beam. In other words, the main emission direction defines the main beam direction of the light beam before it reaches the first diffuser.

[0019] Microlens arrays according to the invention comprise multiple lenses arranged in an at least one-dimensional array on a surface of the diffuser. One-dimensional microlens arrays are easier to manufacture compared to two-dimensional arrays, thus reducing the manufacturing costs of the illumination system. Two-dimensional arrays offer more possibilities for influencing the beam but are significantly more complex to manufacture. The term "micro" in the context of the invention is not to be understood as meaning that the lenses are only on the order of one micrometer. Rather, the lenses of the microlens arrays are small compared to ordinary lenses, which are typically several centimeters in size.

[0020] The light source within the meaning of the invention can, in principle, be any device designed to emit light. Further details regarding the light source are described below.

[0021] For the purposes of the invention, a beam of light is a bundle of electromagnetic waves which behaves in such a way that it can be described essentially by geometric optics, i.e., according to wave optics for vanishingly small wavelengths of light. This can mean that no or only negligible diffraction effects occur at the first and second diffusers and that the beam path is essentially determined by refraction.

[0022] In connection with the invention, various directions are mentioned. These are hypothetical directions of action or movement of an object. The main emission direction of the light source generally occurs essentially along one axis.

[0023] The term "spreading" the beam in a first or second direction refers to the beam widening along a second axis that is not the same as the main emission direction. For example, if the beam spreads along a z-axis in a right-handed coordinate system, the first direction could correspond to a y-axis and the second direction to an x-axis of the same system. In this case, the first and second directions differ by 90°. This allows for precise adjustment of the scene's lighting using just two diffusers. However, it is also possible for the first and second directions to be at different 90° angles to each other.

[0024] Overall, the lighting system offers the advantage that the microlens arrays, which can be easily and relatively inexpensively attached to the diffusers, allow for precisely adjustable illumination of the scene. This also prevents areas that should not be illuminated from being unnecessarily lit, thus saving energy and increasing the system's safety.

[0025] In a lighting system according to the invention, it can be provided that the first diffuser is plate-shaped and has a flat, optically smooth third surface opposite the first surface and / or that the second diffuser is plate-shaped and has a flat, optically smooth fourth surface opposite the second surface.

[0026] Optically smooth can be understood to mean that the surface is designed in such a way that no diffuse scattering occurs for the beam of rays emitted by the light source.

[0027] Furthermore, in an illumination system according to the invention, it is conceivable that the first microlens array is configured to widen the emittable beam symmetrically or asymmetrically around the main emission direction in the first direction, and / or that the second microlens array is configured to widen the emittable beam symmetrically or asymmetrically around the main emission direction in the second direction. For certain applications, at least one widening, and particularly advantageously exactly one of the widenings, can be asymmetrical.

[0028] In other words, the microwave arrays of the diffusers can each spread the light either symmetrically or asymmetrically. For the purposes of the invention, symmetrical and asymmetrical spreading refers to spreading in a (first or second) direction around the axis of the main emission direction. For example, if the beam propagates in the z-direction, then with symmetrical spreading in a y-direction orthogonal to the z-direction, the same amount of light or energy from the beam is emitted above and below the main emission direction (or the z-axis) in the y-direction. The same would be true for an x-direction along the second direction. With asymmetrical spreading, more light would be emitted above the main emission direction than below, or vice versa. Symmetrical spreading allows for particularly homogeneous illumination of a scene.

[0029] An asymmetrical beam pattern offers the advantage of excluding areas where no reflective objects are expected within the scene, or areas that should not be illuminated at all. This saves energy from the light source and increases safety.

[0030] It can be arranged that the first or second microlens array widens the beam asymmetrically, while the other microlens array widens the beam symmetrically. Particularly in connection with use in a motor vehicle, this offers the advantage, for example, that the sky can be left unlit, and only the roadway can be illuminated.

[0031] Furthermore, in a lighting system according to the invention, it is conceivable that the first diffuser is designed to generate an asymmetric light intensity distribution of the beam in the first direction and / or the second diffuser is designed to generate an asymmetric light intensity distribution of the beam in the second direction.

[0032] Furthermore, in an illumination system according to the invention, it can advantageously be provided that the first microlens array and / or the second microlens array comprise cylindrical lenses. This means that the microlens array comprises optical lenses which have a refractive power in one direction, while having no refractive power in another direction perpendicular to it. Cylindrical lenses, especially small cylindrical lenses, are significantly easier to manufacture than spherical lenses. This reduces the manufacturing costs of the illumination system.

[0033] Furthermore, in an illumination system according to the invention, it is conceivable that the first microlens array and / or the second microlens array have a cross-sectional surface profile that is at least wavy, sinusoidal, or repeatingly exponentially similar to a function. "Wavy" refers to a wave-like pattern, i.e., with multiple maxima and minima. "Sinusoidal" encompasses both the shape of a sine (or cosine; the phase is irrelevant in this context) and similar shapes that exhibit only a slightly altered optical form, which, however, cannot always be described concisely in mathematical terms. "Repeatingly exponentially similar" refers to a function that initially drops sharply from a maximum and then slowly approaches a minimum value, before jumping back to the maximum.This also includes the inverse function (slowly increasing, rapidly increasing, abruptly falling back to a minimum). Microlens arrays with the aforementioned cross-sections can be manufactured relatively easily, for example by planing, milling, or even injection molding. Furthermore, symmetrical expansion can be easily achieved with wave-shaped and sinusoidal cross-sections, and asymmetrical expansion with cross-sections resembling exponential functions.

[0034] Furthermore, in an illumination system according to the invention, it can advantageously be provided that the first microlens array and / or the second microlens array have a periodically repeating surface profile which, in each period, corresponds to a power series either with exclusively even exponents or with even and odd exponents. In both cases, an infinite power series can be present, or the sum can be a finite series up to a maximum n. max =N can be formed. In particular, it can be provided that the power series of the form f(x)=∑an*xn−a0 This corresponds to where, in the case of an even power series, n = 2k, and k is a natural number. Then only even exponents are permitted. Here, a can be, but does not have to be, n It can take exclusively positive values. It can also be a power series of the form f(x) = Σ-a. n * x n- a0 is provided, which in connection with the invention is called the inverted power series. The combination of the inverted and non-inverted profiles can result in a wave structure. In this case, the non-inverted power series with the same coefficients a can be used in the first half of a period and the inverted power series in the second half of the period. n such a wavy surface structure can be advantageous in terms of manufacturing technology and robustness.

[0035] Furthermore, it can be stipulated that n is a natural number, meaning it can be either even or odd. This corresponds to a power series with even and odd exponents. This allows for the creation of an asymmetric surface profile.

[0036] Furthermore, in an illumination system according to the invention, it can advantageously be provided that the first microlens array has a periodically repeating surface structure in the first direction, which is particularly translationally invariant in a third direction perpendicular to the first direction, and / or that the second microlens array has a periodically repeating surface structure in the second direction, which is particularly translationally invariant in a fourth direction perpendicular to the second direction. In other words, it can be provided that the surface structure repeats at least section by section. In particular, it can be provided that different periodically repeating surface structures are provided in the direction in which the beam is expanded, starting from the main emission direction at the center.In particular, the periodically repeating surface structures can be designed to be mirror-symmetrical around the central axis. This can further enhance the asymmetrical illumination.

[0037] Advantageously, the first, second, third, and fourth directions can lie in the plane of the diffuser's plate.

[0038] Furthermore, in an illumination system according to the invention, it is conceivable that the first microlens array is arranged at least on an input side of the first diffuser or on an output side of the first diffuser, and / or that the second microlens array is arranged at least on an input side of the second diffuser or on an output side of the second diffuser. As already mentioned, for the basic function of the illumination array, it is only important that two surfaces are equipped with microlens arrays. However, the arrangement on the different surfaces offers the advantage that it allows for advantageous adaptation depending on the application. For example, if the output side of the second diffuser is expected to be subject to particular mechanical stress, a microlens array can be omitted there and instead arranged on the input side of the second diffuser.

[0039] Furthermore, in a lighting system according to the invention, it can advantageously be provided that an input side of the first diffuser and / or an output side of the first diffuser is coated with at least one anti-reflective layer, one water-repellent layer, or one scratch-resistant layer, and / or that an input side of the second diffuser and / or an output side of the second diffuser is coated with at least one anti-reflective layer, one water-repellent layer, or one scratch-resistant layer. Anti-reflective layers can reduce reflection losses of the light beam. These can be particularly advantageously provided on the input side of the first and / or second diffuser. A water-repellent layer and a scratch-resistant layer offer the advantage that the corresponding diffuser surface is less easily soiled (or scratched).The surface can be wetted with water or scratched, thus reducing the optical quality of the expansion. It is particularly advantageous to coat the outlet side of the second diffuser with a water-repellent or scratch-resistant layer, as this surface is usually the one most likely to come into contact with water or be subjected to mechanical stress.

[0040] Furthermore, in an illumination system according to the invention, it is conceivable that a normal of the first and / or second microlens array is arranged parallel to the main emission direction. This enables particularly homogeneous illumination. This can mean that a normal of the microlens array is arranged parallel to the main emission direction of the light beam of the light source. In the case of a plate-shaped diffuser, this can be understood to mean that the plate normal is arranged in the direction of the main emission direction. Furthermore, the microlens arrays for this case can be designed and manufactured with relatively little effort according to the illumination task.

[0041] Furthermore, a detection system according to the invention can be provided that comprises an illumination system according to the invention and at least one sensor configured to detect a reflected beam of light generated by reflection of the emittable beam (11) off at least the scene (40). Additionally, a receiving optic can be provided, configured to focus the reflected beam of light onto the sensor. In other words, means for emitting the beam of light and for receiving the reflected light can be provided. This offers the additional advantage that these components can be precisely matched to the diffusers or microarrays, thus enabling even better adaptation to the scene to be illuminated. In particular, the detection system can be a lidar system, specifically a flash lidar system, i.e.,The sensor can be operated with individual laser pulses. It can be configured as a matrix sensor for time-of-flight (TOF) detection of the reflected light, specifically as a photomixing detector (PMD) or single-photon avalanche diode array (SPAD array).

[0042] Furthermore, in a lighting system according to the invention, it can advantageously be provided that the light source is configured as at least one light source array, in particular an LED array or a laser array, in particular a vertical-cavity surface-emitting laser (VCSEL), and that the light source array comprises several individual emitters and the light beam comprises several partial light beams, each partial light beam being emittable from one of the individual emitters. A light source array offers the advantage that one or a plurality of beams can be emitted, which may already have a spatial distribution. This allows for particularly effective beam expansion. An LED array offers the advantage of being particularly cost-effective to manufacture. A laser array, in turn, has the advantage of exhibiting particularly high optical quality with regard to coherence.Vertical-cavity surface-emitting lasers have the advantages of a laser and, for example, compared to edge-emitting lasers (which are also conceivable), have the advantage of being easy and inexpensive to manufacture.

[0043] Within the scope of the invention, it is further conceivable that a first array direction of the light source is arranged rotated relative to the first direction about a main emission direction, wherein the rotation is particularly between 1° and 10°, preferably between 1° and 5°. This allows for a particularly homogeneous illumination of the scene. In addition, speckle effects can be reduced.

[0044] Furthermore, in a lighting system according to the invention, it can advantageously be provided that a light source designed as a light source array has a period length (pitch), i.e., a distance between two adjacent array elements, which does not correspond to an integer multiple of a period of a periodically repeating surface structure of the first microlens array. This special arrangement also allows for particularly homogeneous illumination of the scene. The period length can be determined in the first direction. This can be a column spacing of the array. The row spacing of the array can be equal to or different from the column spacing.

[0045] According to a further aspect of the invention, a method for illuminating a scene, in particular by means of a lighting system according to one of the preceding claims, is provided, comprising: - Emitting a beam of light through a light source, - Widening of the beam by a first microlens array, which is arranged on a first surface of a first diffuser, in a first direction, - Widening of the beam by a second microlens array, which is arranged on a second surface of the second diffuser, in a second direction, where the first direction and the second direction differ from each other.

[0046] Thus, a method according to the invention offers the same advantages as those already described in detail with reference to a lighting system according to the invention.

[0047] According to a further aspect of the invention, a lidar system for determining distances in a scene is provided, suitable for carrying out a method according to the invention for illuminating a scene and / or comprising an illumination system according to the invention and a sensor, in particular designed as a matrix sensor, for time-of-flight detection of the light reflected from the objects of the illuminated scene onto the sensor. Furthermore, the lidar system can include a receiving optic for imaging the reflected beam of light onto the sensor.

[0048] Thus, a lidar system according to the invention offers the same advantages as those already described in detail with reference to a lighting system and / or a method according to the invention.

[0049] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination. The drawings schematically show: Fig. 1: a lighting system in conjunction with an optional lidar system in a top-down view, Fig. 2: the area of Fig. 1, in which the emitted beam of radiation is spread out by the two diffusers, Fig. 3: An enlarged view of possible surface structures of the diffusers, Fig. 4: the two diffusers arranged one behind the other in a geometric representation, Fig. 5: a further enlarged representation of possible surface structures of the diffusers, Fig. 6: possible intensity profiles of the expanded beam, and Fig. 7: the lighting system in different scenes, Fig. 8 a microlens array for asymmetric beam expansion.

[0050] In the following description of some embodiments of the invention, the same reference numerals are used for the same technical features even in different embodiments.

[0051] Fig. Figure 1 shows a highly simplified representation of the lighting system 100 according to the invention. The lighting system 100 serves to illuminate a scene 40 and comprises a first diffuser 110 with a first microlens array 112 arranged on a first surface 111 of the first diffuser 110. The first microlens array 112 is configured to widen a beam of light 11 emitted by a light source 10 in a first direction 210 (for the sake of simplicity, the widening is not shown in the Fig. 1, but in the Fig. (2 shown). Furthermore, the illumination system 100 comprises a second diffuser 120, which is arranged behind the first diffuser 110 in a main emission direction 250 of the light source 11, with a second microlens array 122 arranged on a second surface 121 of the second diffuser 120, wherein the second microlens array 122 is configured to spread the emittable beam 11 in a second direction 220. The first direction 210 and the second direction 220 differ from each other.

[0052] The light source 10 can further be provided as part of the lighting system 100, wherein the light source 10 is configured to emit the emittable beam 11 in the main emission direction 250. In an advantageous further development of this embodiment, a sensor 20, configured to detect a reflected beam 12 resulting from a reflection of the emittable beam 11 off at least the scene 40, and a receiving optic 30, configured to focus the reflected beam 12 onto the sensor 20, can also be provided.

[0053] In the Fig. Figure 2 shows an enlarged view of the area in which the beam of light 11 emitted by the light source 10 passes through the first and second diffusers 110, 120. It can also be seen that in the view of the Fig. 2 only the first diffuser 110 causes a widening in the first direction 210. The second diffuser 120 appears to, according to the Fig. 2 has no effect, however, its widening extends in front of and behind the image plane along the second direction 220, which in this example is perpendicular to the first direction 210 and the main emission direction 250.

[0054] The light source 10 can be configured as at least one light source array, in particular an LED array or a laser array, in particular a vertical-cavity surface-emitting laser, wherein in particular the light source array comprises several individual emitters and the light beam comprises several partial light beams, each partial light beam being emittable from one of the individual emitters.

[0055] Furthermore, it can be provided that an array direction of the light source 10 is arranged rotated relative to the first direction 210 by a main emission direction 250 (not shown here), wherein in particular the rotation is between 1° and 10°, preferably between 1° and 5°.

[0056] The light source 10 is arranged at a distance from the first microlens array 112. In a modification of the embodiment (not shown), the first diffuser can be arranged directly at the light source, i.e., without an air gap.

[0057] The light source can be configured as a light source array with a period (pitch) that does not correspond to an integer multiple of a period of a periodically repeating surface structure 131 of the first microlens array 112. This allows for particularly homogeneous illumination.

[0058] The diffusers 110 and 120, connected in series and each spreading the emitted beam 11 in different directions, create illumination adapted to the scene 40. The beams 12 reflected from the scene 40 can be received by a sensor 20. To optimally image the reflected beams 12 onto the sensor 20, a receiving optic 30 can be provided.

[0059] It can, as in the Fig. 2 shown, it is provided that the first diffuser 110 and / or the second diffuser 120 are arranged perpendicular to the main emission direction 250.

[0060] According to a further aspect of the invention, a method for illuminating a scene 40, in particular by means of an illumination system 100 according to the invention, can be provided. The method comprises emitting a beam of light 11 by a light source 10, expanding the beam of light 11 by a first microlens array 112, which is arranged on a first surface 111 of a first diffuser 110, in a first direction 210, and expanding the beam of light 11 by a second microlens array 122, which is arranged on a second surface 121 of the second diffuser 120, in a second direction 220, wherein the first direction 210 and the second direction 220 are different from each other.

[0061] According to a further aspect of the invention, a lidar system for determining distances in a scene 40 can be provided, at least comprising an inventive lighting system 100 or suitable for carrying out an inventive method for illuminating a scene. Lidar systems are used in particular in vehicles to measure the vehicle's surroundings. The data thus acquired can, for example, serve to orient the vehicle or be made available for subsequent investigations.

[0062] In Fig. Figure 7 shows, for example, an airplane and a car, which illuminate the surrounding scenery 40 with the help of a lighting system 100. The reflected radiation can then be received by the sensor 20 of a lidar system, so that the distance of the objects in the scene can be measured.

[0063] It can be provided that the first microlens array 112 is configured to widen the emittable beam 11 symmetrically or asymmetrically around the main emission direction 250 in the first direction 210, and / or that the second microlens array 122 is configured to widen the emittable beam 11 symmetrically or asymmetrically around the main emission direction 250 in the second direction 220. In other words, the microlens arrays 112 and 122 can each widen the emitted light beam 11 symmetrically or asymmetrically around the main emission direction 250.

[0064] It may be provided that the widening of the light beam 11 by the microlens arrays 112, 122 is adapted to a scene 40.

[0065] It can be particularly advantageous, for example, to provide that one of the microlens arrays 112, 122 produces a symmetrical and the other of the microlens arrays 112, 122 produces an asymmetrical expansion of the beam 11. This can be advantageous, for example, when illuminating scenes where a part of the scene does not reflect light, such as the sky. The asymmetrical expansion allows a portion of the scene 40 to be left out, thus saving energy at the light source 10.

[0066] In the Fig. Figure 6 shows an example of a symmetrically expanded emitted beam 11 in comparison (dashed line) to an asymmetrically expanded emitted beam 11. The in the Fig. The ordinate shown in 6 corresponds to an intensity of the beam, and the abscissa to the first and / or second direction 210, 220, in which the beam 11 can be expanded.

[0067] In the Fig. Figure 7 finally shows how the asymmetrical widening can be used to advantage. Because less light is emitted upwards, less radiant power is lost towards the sky, where there are no reflective objects. This allows for a corresponding saving of power at the light source 10.

[0068] The following section will discuss in more detail the shape of the microlens arrays 112, 122.

[0069] It may be provided that the first microlens array 112 and / or the second microlens array 122 have cylindrical lenses 130. As greatly simplified in the Fig. As shown in Figure 4, cylindrical lenses 130 on the diffuser essentially correspond to structures which run linearly in one direction on a surface 113, 114, 123, 124 of the diffusers 110, 120.

[0070] The first microlens array 112 can be arranged at least on an input side 113 of the first diffuser 110 or on an output side 114 of the first diffuser 110, and / or the second microlens array 122 can be arranged at least on an input side 123 of the second diffuser 110 or on an output side 124 of the second diffuser 120. In other words, the diffusers 110, 120 can have a microlens array 112, 122 on one of their surfaces 111, 121. It can be particularly advantageous, for example, if the output side 124 of the second diffuser 120, which faces the scene 40, does not have a microlens array 122, since this side comes into contact with the outside world and is therefore particularly susceptible to contamination and mechanical stress.

[0071] It may be provided that an input side 113 of the first diffuser 110 and / or an output side 114 of the first diffuser 110 are coated with at least an anti-reflective layer, a water-repellent layer, or a scratch-resistant layer, and / or that an input side 123 of the second diffuser 120 and / or an output side 124 of the second diffuser 120 are coated with at least an anti-reflective layer, a water-repellent layer, or a scratch-resistant layer. Here, too, it is particularly advantageous if, for example, the input sides 113, 123 are coated with an anti-reflective layer so that as little as possible of the emitted beam 11 is reflected back to the light source 10 and thus lost. Coating the output side 124 of the second diffuser 120, which faces the scene 40, with a water-repellent layer and / or a scratch-resistant layer is also particularly advantageous, as this may beis in contact with the outside world and is subject to increased mechanical stress.

[0072] In the Fig. Figure 3 shows some possible cross-sectional shapes of the microlens arrays 112, 122. The abscissas 210, 220 shown in the figure correspond to an extent of the microlens array 112, 122 perpendicular to the principal emission direction, and the ordinates 250 each correspond to an extent of the microlens array 112, 122 in the principal emission direction. The area above the function graph corresponds to a medium (usually air) surrounding the diffuser 110, 120, and the area below the function graph corresponds to the microlens array 112, 122. In all three representations of the function graph, the surface structure 131 of the microlens arrays 112, 122 can be seen, which repeats periodically in these examples.

[0073] It may be provided that the first microlens array 112 and / or the second microlens array 122 has at least a wave-like (all three variants), sinusoidal (bottom variant) or a repeating exponential-function-like surface profile in a cross-section (see Fig. 5) have.

[0074] Furthermore, the first microlens array 112 and / or the second microlens array 122 can have a surface profile corresponding to a power series with an even or odd exponent. Power series with an even exponent correspond to microlens arrays 112 and 122, which are those in Fig. 3 are similar. Power series with odd exponents lead approximately to microlens arrays 112, 122 with a shape as described in Fig. 5 are shown.

[0075] According to one embodiment, it can be provided that the power series of the form f(x)=∑an*xn−a0 corresponds to, with n = 1...6 coefficients, which represent the values a1=0 a2=0.69200605 a3=4.787606 a4=16.8596451 a5=−0.1015752 a6=0.69953097 This results in an asymmetric structure. Do the coefficients have the values a1=0 a2=1.83052045 a3=0 a4=4.62166261 a5=0 a6=59.4737154 A symmetrical structure can be achieved.

[0076] Furthermore, it can be provided that the first microlens array 112 has a periodically repeating surface structure 131 in the first direction 210, which is particularly translationally invariant in a third direction perpendicular to the first direction 210, and / or that the second microlens array 122 has a periodically repeating surface structure 131 in the second direction 220, which is particularly translationally invariant in a fourth direction perpendicular to the second direction. The [details of the] Fig. The structures shown in Figure 4 are generally not to scale. Rather, the periodically repeating surface structure 131 can be so small compared to the dimensions of the diffusers 110, 120 that they would no longer be representable at the scale of the drawing. Typical periods can range from 0.1 to 10 mm, for example.

[0077] Fig.Figure 8 shows a plate-shaped diffuser for asymmetric beam expansion. This is depicted here as a first diffuser 110. The first microlens array 112 can be arranged at least on an input side 113 of the first diffuser 110 (not shown) or on an output side 114 of the first diffuser 110, as shown. The first microlens array 112 can have a period 141 of a periodically repeating surface structure of microlenses 130. The period corresponds here to the width of a microlens, here in the first direction 210. In the perpendicular direction 220, the microlenses are translationally invariant. The asymmetric beam expansion is caused by the asymmetry of the cylindrical lenses 130. Analogously (not shown), a second diffuser can be configured, which is rotated by 90° relative to the first diffuser about the main emission direction 250.

[0078] The preceding explanation of the embodiments describes the present invention solely by way of examples. Naturally, individual features of the embodiments can be freely combined with one another, provided this is technically feasible, without departing from the scope of the present invention. Reference symbol list 10 light sources 11 emitted beam of radiation 12 reflected beams 20 Sensor 30 receiving optics 40 Scenery 100 lighting system 110 first diffuser 111 first surface 112 first microlens array 113 Inlet side of the first diffuser 114 Outlet side of the first diffuser 120 second diffuser 121 second surface 122 second microlens array 123 Inlet side of the second diffuser 124 Output side of the second diffuser 130 cylindrical lenses 131 Surface structure 141 Period of the microlens array 210 first direction 220 second direction 250 Main emission direction

Claims

[1] Lighting system (100) for illuminating a scene (40), comprising: at least one light source (10), a first diffuser (110) with a first microlens array (112) arranged on a first surface (111) of the first diffuser (110), wherein the first microlens array (112) is configured to widen a beam of light (11) emittable by the light source (10) in a principal emission direction (250) of the light source (10) in a first direction (210) and / or to achieve a desired first intensity distribution in the first direction, a second diffuser (120), which is arranged in the beam path downstream of the first diffuser (110), with a second microlens array (122) arranged on a second surface (121) of the second diffuser (120), wherein the second microlens array (122) is configured to widen the emittable beam (11) in a second direction (220) and / or to achieve a desired second intensity distribution in the second direction, wherein the first direction (210) and second direction (220) are different from each other, and wherein the illumination system is free of further optical elements [2] Lighting system (100) according to claim 1, characterized by, that the first diffuser (110) is plate-shaped and has a flat, optically smooth third surface opposite the first surface (111) and / or that the second diffuser (120) is plate-shaped and has a flat, optically smooth fourth surface opposite the second surface (121). [3] Lighting system (100) according to claim 1 or 2, characterized by , the first microlens array (112) is designed to widen the emittable beam (11) asymmetrically around the main emission direction (250) in the first direction (210) and / or the second microlens array (122) is designed to widen the emittable beam (11) asymmetrically around the main emission direction (250) in the second direction (220). [4] Lighting system (100) according to any one of the preceding claims, characterized by, that the first diffuser (110) is designed to generate an asymmetric light intensity distribution of the beam (11) in the first direction (210) and / or the second diffuser (120) is designed to generate an asymmetric light intensity distribution of the beam (11) in the second direction (220). [5] Lighting system (100) according to any one of the preceding claims, characterized by that the first microlens array (112) and / or the second microlens array (122) have cylindrical lenses (130). [6] Lighting system (100) according to any one of the preceding claims, characterized by , that the first microlens array (112) and / or the second microlens array (122) have at least a wave-like, sinusoidal or a repeating exponential-function-like surface profile in a cross-section. [7] Lighting system (100) according to any one of the preceding claims, characterized by, that the first microlens array (112) and / or the second microlens array (122) have a periodically repeating surface profile which in each period corresponds to a power series with exclusively even exponents or even and odd exponents. [8] Lighting system (100) according to any one of the preceding claims, characterized by , that the first microlens array (112) has a periodically repeating surface structure (131) in the first direction (210), which is particularly translation-invariant in a third direction perpendicular to the first direction (210) and / or the second microlens array (122) has a periodically repeating surface structure (131) in the second direction (220), which is particularly translation-invariant in a fourth direction perpendicular to the second direction. [9] Lighting system (100) according to any one of the preceding claims, characterized by , that the first microlens array (112) is arranged at least on an inlet side (113) of the first diffuser (110) or on an outlet side (114) of the first diffuser (110), and / or the second microlens array (122) is arranged at least on an inlet side (123) of the second diffuser (110) or on an outlet side (124) of the second diffuser (120). [10] Lighting system (100) according to any one of the preceding claims, characterized by , that an inlet side (113) of the first diffuser (110) and / or an outlet side (114) of the first diffuser (110) are coated with at least an anti-reflective layer, a water-repellent layer or a scratch-resistant layer, and / or that an inlet side (123) of the second diffuser (120) and / or an outlet side (124) of the second diffuser (120) are coated with at least an anti-reflective layer, a water-repellent layer or a scratch-resistant layer. [11] Lighting system (100) according to any one of the preceding claims, characterized by , that a normal of the first and / or second microlens array (112, 122) is arranged parallel to the main emission direction (250). [12] Lighting system (100) according to any one of the preceding claims, characterized by , that the light source (10) is configured as at least a light source array, in particular an LED array or a laser array, in particular a vertical-cavity surface-emitting laser, and the light source array comprises several individual emitters and the light beam comprises several partial light beams, each partial light beam being emittable from one of the individual emitters. [13] Lighting system (100) according to claim 12, characterized by , that an array direction of the light source (10) is arranged rotated relative to the first direction (210) about a main emission direction (250), wherein in particular the rotation is between 1° and 10°, preferably between 1° and 5°. [14] Lighting system (100) according to one of claims 12 to 13, characterized by , that the light source array has a period length (pitch) and the period length does not correspond to an integer multiple of a period of a periodically repeating surface structure (131) of the first microlens array (112). [15] Detection system comprising an illumination system (100) according to one of the preceding claims and at least one sensor (20) which is configured to detect a reflected beam of light (12) which is created by a reflection of the emittable beam of light (11) on at least the scene (40), in particular wherein a receiving optic (30) is also provided which is configured to focus the reflected beam of light (12) onto the sensor (20). [16] Method for illuminating a scene (40), in particular by means of a lighting system (100) according to one of the preceding claims, comprising: - Emitting a beam of rays (11) through a light source (10), - Widening of the beam (11) by a first microlens array (112) which is arranged on a first surface (111) of a first diffuser (110), in a first direction (210), - Widening of the beam (11) by a second microlens array (122) which is arranged on a second surface (121) of the second diffuser (120), in a second direction (220), where the first direction (210) and the second direction (220) differ from each other. [17] Lidar system for determining distances in a scene (40), suitable for carrying out a method for illuminating a scene according to claim 16 and / or comprising a lighting system (100) according to one of claims 1 to 14 and a sensor (20), in particular designed as a matrix sensor, for time-of-flight detection of the light reflected back to the sensor by the objects of the illuminated scene.

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