Device for protecting against soiling for an optical sensor, in particular a lidar sensor

Abstract

The invention relates to a protective device for an optical sensor, in particular a lidar sensor (10), comprising a receiving region in which an optical unit is arranged. The optical unit is arranged in the region behind a transparent light emission area (12), and the light emission area (12) is arranged and designed so as to transmit light, in particular laser light, in particular so as to transmit light of the optical unit in the direction of the surrounding area and / or so as to transmit light from the surrounding area in the direction of the optical unit. The aim of the invention is to allow a continuously reliable operation for such optical sensors, in particular when being used on a detection system of a vehicle. According to the invention, this is achieved in that the light emission area (12) is paired with a protective device (20) which is designed to protect at least one region of the light emission area (12) surface facing the surrounding area against soiling using a gas flow, the protective device (20) has a gas line with at least one nozzle assembly (26), the nozzle assembly (26) has at least one nozzle (25), and the nozzle assembly (26) is designed to generate a directed gas flow such that the gas flow generates a gas curtain (F1-F4) on the surrounding area side along the light emission area (12) and preferably in a spaced manner to the light emission area (12) at least in some regions.

Description

[0001] Contamination protection device for an optical sensor, particularly a lidar sensor

[0002] The invention relates to a protective device for an optical sensor, in particular a lidar sensor having a receiving area in which an optical unit is arranged, wherein the optical unit is arranged in the area behind a transparent light-emitting surface, and wherein the light-emitting surface is arranged and designed to transmit light, in particular laser light, in particular to transmit light of the optical unit in the direction of the environment and / or to transmit light from the environment in the direction of the optical unit.

[0003] Modern motor vehicles increasingly use optical sensors to monitor their surroundings. Cameras, lidar sensors, and other optical sensors are frequently used. These sensors are particularly important for autonomous vehicles. A fundamental prerequisite for the safe operation of the vehicle is the proper functioning of the sensors for spatial orientation. Contamination of the sensor surface, for example, caused by collisions with dirt particles, water, or insects, is therefore detrimental to the safe operation of the vehicle.

[0004] Currently, various concepts are being pursued for cleaning the transparent light-emitting surface of the sensor. The known concepts utilize multiple cleaning nozzles to clean the sensor surface by direct irradiation with gaseous and / or liquid media to remove particles from the transparent light-emitting surface. In addition to cleaning with cleaning nozzles, mechanical cleaning of the surface using various wiping concepts in combination with liquid wetting is also known.

[0005] Another well-known method is ultrasonic cleaning (approximately 35 Hz). This involves first applying a liquid to the sensor surface. A piezoelectric crystal then causes the sensor surface to vibrate, loosening the contaminants.

[0006] With existing concepts, the aim is to clean the sensor surface as thoroughly as possible, or rather, to prevent particles from adhering to it. Ensuring continuous and complete cleaning of the surface is technically complex. For example, the maximum amount of fluid that can be carried in the vehicle is limited. Therefore, continuous cleaning cannot be guaranteed, and the cleaning fluid must be replaced frequently.

[0007] With all mechanical cleaning concepts, a kind of blind spot occurs during cleaning. This means that the sensor's field of view is restricted.

[0008] Another disadvantage is the number of components involved in conventional designs. Typically, several cleaning nozzles are used per sensor, which must be connected to a compressed air or fluid system via hoses. Due to the number of components, it is often impossible to implement a compact design. Furthermore, costs and complexity increase with the number of components.

[0009] In known concepts with gaseous cleaning media (e.g. compressed air), in which the fluid flows directly onto the sensor surface via nozzles, an oil-free compressor concept must always be implemented to avoid contamination of the sensor surface with oil.

[0010] In known concepts using gaseous cleaning media, the sensor surface is cleaned via shear stresses. The object of the invention is to create a protective device for an optical sensor, in particular a lidar sensor, of the type mentioned above, which enables continuous, safe operation, particularly when used in a vehicle detection system.

[0011] This object is achieved in that the light-emitting surface is assigned a protective device which is designed to protect at least a region of the surface of the light-emitting surface facing the environment from contamination by means of a gas flow, in that the protective device has a gas guide with at least one nozzle arrangement, in that the nozzle arrangement has at least one nozzle, in that the nozzle arrangement is designed to generate a directed gas flow such that the gas flow on the environment side creates a gas curtain along the light-emitting surface and preferably at least partially spaced from the light-emitting surface. The distance between the nozzle outflow surface and the sensor surface is preferably at most twice the characteristic length of the sensor element, for example the diameter or the longest extension of the sensor element.

[0012] With the protective device according to the invention, the particles from the environment are deflected by the gas, in particular air, curtain before they can hit the light-emitting surface. This prevents or at least greatly reduces contamination of the light-emitting surface. The effort required to clean the sensor surface can therefore be prevented or at least greatly reduced. The gaseous fluid required to operate the protective device can be provided via a pressure system, in particular a compressed air system, for example a compressed air system already present in the vehicle. It is conceivable that the gaseous fluid is conveyed by means of a radial or scroll compressor and made available to the nozzle arrangement. In contrast to concepts using liquid cleaning agents, air as a gaseous fluid is available in unlimited quantities, which significantly simplifies maintenance work.The inventive solution enables continuous and permanently reliable operation of the optical sensor. Another advantage of this concept is that the gas curtain comes into little or no contact with the light-emitting surface. Thus, the choice of compressor concept for conveying the gas flow is not subject to any restrictions regarding the lubricant used in the compressor.

[0013] According to a preferred embodiment of the invention, the nozzle or at least some of the nozzles of the nozzle arrangement can have a geometry by means of which a main flow direction of the gas can be generated at the nozzle outlet, which runs parallel or at an angle measured perpendicular to the light-emitting surface. If the main flow direction runs outward at an angle to the light-emitting surface, a force component arises in the flow that points perpendicularly away from the light-emitting surface. A particle impacting with high kinetic energy due to the driving movement of a vehicle is thereby reliably intercepted and diverted.

[0014] Preferably, the main flow direction can be provided with the light-emitting surface at an angle measured perpendicular to the light-emitting surface in the range between 0° and 60°. For applications in trucks, the angle is preferably selected in the range between 0° and 20°. For motor vehicles, an angle between 5° and 30° is particularly suitable.

[0015] An optical sensor according to the invention can be designed such that the light-emitting surface is designed, at least in some areas, as a flat surface in front of which the gas curtain can be generated in the surrounding area, and / or that the light-emitting surface is designed, at least in some areas, as a surface curved in the direction of the environment, in particular a cylindrical or partially cylindrical surface, in front of which the gas curtain can be generated in the surrounding area.

[0016] If a cylindrical or partially cylindrical surface is implemented on the light-emitting surface, it can be provided, in particular, that the main flow direction runs at an inclination in the circumferential direction of the cylindrical or partially cylindrical light-emitting surface, with the inclination angle preferably being selected in the range between 0° and 30°. Such a design prevents the generated gas curtain from being excessively influenced by the airstream acting on the optical sensor.

[0017] To minimize the impact of the gas flow from the protective device on the light-emitting surface of the optical sensor, the gas outlet surface at the nozzle outlet of the nozzle arrangement can be arranged at a distance from the light-emitting surface. Preferably, the gas outlet surface is offset from the light-emitting surface in the direction of the light-emitting surface and / or offset transversely thereto. The distance between the nozzle outlet surface and the sensor surface is preferably a maximum of twice the characteristic length of the sensor element, for example, the diameter or the longest extension of the sensor element.

[0018] According to the invention, it can be provided that the nozzle arrangement is arranged in the region of one side of the light-emitting surface, wherein it is preferably provided that a nozzle arrangement is arranged on each opposite side of the light-emitting surface, and that the nozzle arrangement(s) is / are arranged and designed to generate a gas curtain directed towards the opposite side of the light-emitting surface. The use of a nozzle arrangement on only one side of the light-emitting surface is particularly suitable for smaller optical sensors. With large light-emitting surfaces, it is advantageous to generate a gas curtain on each of the opposite sides in order to achieve effective protection of the light-emitting surface.

[0019] For a compact design, it can be provided that the light emission surface is delimited by a carrier at least in the region of one side of the light emission surface, and that the carrier carries the nozzle arrangement, wherein it is preferably provided that the light emission surface is delimited on opposite sides by means of a carrier each, and that the two carriers each carry a nozzle arrangement.

[0020] A conceivable alternative to the invention can be such that the light-emitting surface is delimited on opposite sides by side edges, and that the nozzle arrangement of the protective device is provided in the area between these side edges. Such a design is particularly suitable if there is an area within the light-emitting surface that is not required for the light to pass through the sensor. In this case, it is particularly advantageous if the protective device arranged between the side edges has a nozzle arrangement on opposite sides, each facing a side edge of the light-emitting surface, for generating a gas curtain directed towards the associated side edge.

[0021] An optical sensor according to the invention can be designed such that the nozzle arrangement has at least one continuous or discontinuous annular nozzle, which is assigned to a light-emitting surface designed as an at least partially circumferential surface. This concept, in particular, allows for a design in which the entire field of view of the sensor, preferably over the entire 360° circumference of the field of view, is not impaired. It is also conceivable for the nozzle arrangement to have a plurality of individual nozzles.

[0022] A particularly effective protective device for the optical sensor is characterized in that the gas guide has two nozzle arrangements that are arranged one behind the other perpendicular to the light-emitting surface, and in that the main flow directions of the two nozzle arrangements run parallel to one another, or in that the main flow directions of the two nozzle arrangements run at an angle to one another, wherein it is preferably provided that the main flow directions run perpendicular to the light-emitting surface at an angle to one another. The angle can preferably be in the range between 0° and 15°. In this way, gas flows can be achieved that preferably each form its own gas curtain. These gas curtains are arranged one behind the other perpendicular to the light-emitting surface, which enables particularly effective protection.A particle from the environment that, for example, was not completely captured by the first gas curtain can then be safely diverted via the second gas curtain. If the two gas curtains are at an angle to each other, because the main flow directions are at an angle to each other, the individual properties of each gas curtain can be specifically influenced. Of course, it is also conceivable that the gas curtains mix with each other after traveling a certain distance following the nozzle exit. It is also conceivable that, depending on the driving situation, only one of the two gas curtains is operated by specifically controlling the nozzle arrangements.

[0023] The invention will be explained in more detail below with reference to exemplary embodiments shown in the drawings, in which:

[0024] Figure 1 shows a perspective view of an optical sensor,

[0025] Figure 2 shows the optical sensor according to Figure 1 in full section,

[0026] Figure 3 shows a second alternative of an optical sensor in perspective view,

[0027] Figure 4 shows a third alternative of an optical sensor in perspective view,

[0028] Figure 5 shows a fourth alternative of an optical sensor in full section,

[0029] Figure 6 shows a fifth alternative of an optical sensor in perspective view and,

[0030] Figure 7 shows a sixth alternative of an optical sensor in full section. Figure 1 shows an optical sensor, namely a lidar sensor 10, which houses an optical unit in a recording space. The recording space is surrounded by a light-emitting surface 12. The recording space is separated from the surroundings by means of the light-emitting surface 12. At opposite side edges 14 and 15 of the light-emitting surface 12, the recording space is delimited by supports 11 and 13. The light-emitting surface 12 can have a cylindrical outer surface, as shown in the drawings. However, the use of a flat or otherwise curved light-emitting surface 12 is also conceivable. The light-emitting surface 12 is formed, at least in some regions, from a transparent material. The light-emitting surface 12 is designed such that it can transmit light, in particular laser light, emitted by the optical unit in the recording space.Reflected laser light coming from the environment can be transmitted through the transparent light-emitting surface 12 into the recording space. The structure and function of such lidar sensors 10 are generally known from the prior art.

[0031] Such lidar sensors 10 can be used within the scope of the invention, particularly in motor vehicles, preferably in passenger cars. They serve to monitor the area surrounding the vehicle. In particular, such lidar sensors 10 are increasingly being used in autonomous driving to monitor the environment. Accordingly, these lidar sensors 10 can be exposed to the environmental conditions affecting the motor vehicle.

[0032] As Figures 1 and 2 show, a protective device 20 is assigned to the lidar sensor 10, preferably connected thereto, in order to obtain a uniformly handleable component.

[0033] The protective device 20 has a gas guide 21, which is accessible on the inlet side via an inlet opening 22. The protective device 20 can be connected to a gas supply, in particular to an air supply, via the inlet opening 22. For this purpose, a connecting port can be provided in the region of the inlet opening 22, to which a gas supply channel can be coupled. Preferably, the protective device 20 is associated with a compressed air system, wherein the compressed air system may include a compressor by means of which air is drawn in from the environment, compressed, and supplied to the inlet opening 22.

[0034] Adjacent to the inflow opening 22, the protective device 20 has a channel arrangement by means of which the gas supplied via the inflow opening 22 can be fed to at least one nozzle arrangement 26. The channel arrangement may include a distributor 23 by means of which the gas flow is divided in order to feed it to one or more nozzles of the at least one nozzle arrangement 26.

[0035] In the embodiment shown in Figures 1 and 2, the nozzle assembly 26 has a nozzle 24, which can be designed as an at least partially circumferential annular nozzle. The annular nozzle can be designed without interruption in the circumferential region. However, it is also conceivable for the annular nozzle to be composed of individual nozzle segments.

[0036] The nozzle 25 has a nozzle outlet 24. This nozzle outlet 24 is arranged, as shown in Figure 2, at a distance from the light-emitting surface 12 in the direction of its longitudinal extent. Additionally or alternatively, it can also be provided that the nozzle outlet 24 is arranged at a distance perpendicular to the light-emitting surface 12. Accordingly, in the present exemplary embodiment, the nozzle outlet 24 can be arranged radially outwardly offset from the light-emitting surface 12. In the present exemplary embodiment, the outlet surface of the nozzle outlet 24 is arranged slightly radially inwardly offset from the light-emitting surface 12. However, it is also conceivable for the inner nozzle edge of the nozzle outlet 24 to be flush with the surface of the light-emitting surface 12. These embodiments are also intended to be possible within the scope of the invention.

[0037] The protective device 20 can be designed such that, following the inflow opening 22, for example, following the distributor 23, it has one or more channel sections within which the free flow cross-section is smaller than the flow cross-section in the region of the inflow opening 22 and / or in the region of the distributor 23. In this way, an acceleration of the flow and thus an increase in the kinetic energy of the gas flow is achieved in the channel sections. Preferably, the flow cross-section in the at least one channel section tapers continuously, at least in some areas, to avoid flow losses.

[0038] The illustration in Figure 2 shows that at least one guide element 27 can be present in the gas duct of the protective device 20. By means of the at least one guide element 27, the gas flow of the gas supply can be directed toward the associated nozzle(s) 25.

[0039] In the embodiment illustrated in Figure 2, the gas flow exits the protective device 20 through the nozzle outlet(s) 24. A directed gas flow is generated by the gas flow, such that the gas flow on the ambient side creates a gas curtain F1 along the light-emitting surface 12. In the embodiment shown, the gas curtain F1 is arranged at least partially spaced from the light-emitting surface 12.

[0040] In the sense of the invention, this means that the main flow direction H of the gas stream runs at a distance from the light-emitting surface 12 in order to generate the gas curtain F1. In this case, parts of the gas flow, for example, vortices or the like, may touch the light-emitting surface 12. Because the main flow direction H runs at a distance from the light-emitting surface 12, the gas curtain F1 is nevertheless arranged at a distance from the light-emitting surface 12 in the sense of the invention.

[0041] As Figure 2 shows, the main flow direction H in the region of the nozzle outlet 24 runs such that the gas curtain F1 is generated in the direction from the first side edge 15 to the opposite side edge 14 of the lidar sensor 10. The main flow direction H can extend parallel to the light-emitting surface 12. Accordingly, the main flow direction H can extend parallel to the central longitudinal axis of the cylindrical light-emitting surface 12.

[0042] However, Figure 2 shows that it is also possible for the main flow direction H to enclose an angle a with the light-emitting surface 12, measured perpendicularly to the light-emitting surface 12. This angle can be selected in the range between 0° and 60°, preferably in the range between 0° and 30°, and particularly preferably between 0° and 15°.

[0043] It is conceivable that at least one guide element 27 is arranged, preferably in the tapered channel section. Functionally, the at least one guide element 27 can be designed to change the flow direction of the gas guided in the gas supply. Thus, the flow direction can be changed in such a way that the gas flowing out of the nozzle outlet 24 is influenced with respect to its main flow direction H.

[0044] Figure 3 shows a variant embodiment in which the main flow direction H in the region of the nozzle outlet(s) 24 extends at a distance from the light-emitting surface 12 in order to generate a gas curtain F1 in front of the light-emitting surface 12. The main flow direction H has a component that extends in the circumferential direction of the light-emitting surface 12. In particular, the main flow direction H can be inclined in the circumferential direction of the cylindrical or partially cylindrical light-emitting surface 12, with the angle of inclination β preferably being selected in the range between 0° and 30°. It is conceivable to achieve this main flow direction H inclined in the circumferential direction by arranging the at least one guide element 27 in the gas guide 21 at a corresponding angle in order to achieve the desired flow direction.

[0045] Additionally or alternatively, in the embodiment variant according to Figure 3, an inclination of the main flow direction H away from the light emission surface 12 can also be provided, as is also realized in the embodiment according to Figure 2.

[0046] Figure 2 further shows that the protective device 20 can have a base 28, which can be used to partially delimit the gas supply 21. Furthermore, the base 28 can form a connection area by means of which the protective device 20 can be firmly connected to the carrier 13 of the lidar sensor 10.

[0047] Except for the differences described above, embodiment 3 essentially corresponds to the embodiment according to Figures 1 and 2, so that reference can be made to the above explanations.

[0048] Figure 4 illustrates that the protective device 20, as shown, for example, in Figures 1-3, can also be arranged on the underside of the lidar sensor 10, for example, connected to the lower support F. In this case, a gas curtain F1 is generated, which is guided in front of the light-emitting surface 12 from the lower side edge 14 to the upper side edge 15 of the light-emitting surface.

[0049] Figure 5 shows an embodiment in which two protective devices 20 can be arranged on opposite sides of the light-emitting surface 12, for example, in the region of the side edges 14, 15. The protective devices 20 can be designed according to Figures 1-4.

[0050] The upper protective device 20 creates a gas curtain F1 in front of the light-emitting surface 12, which is directed from the upper side edge 15 to the lower side edge 14. The lower protective device 20 creates a gas curtain F2 in front of the light-emitting surface 12, which is directed from the lower side edge 14 to the upper side edge 15.

[0051] Figure 6 shows a protective device 20 having two nozzle assemblies 26, wherein the nozzle assemblies 26 are arranged one behind the other, perpendicular to the light-emitting surface 12, outwardly. As Figure 6 shows, each nozzle assembly 26 may have an at least partially circumferential nozzle 25 or a plurality of nozzles 25 arranged one behind the other. The first nozzle assembly 26 generates a gas curtain F1 as shown in Figures 1-5. The second nozzle assembly 26 generates a gas curtain F3 that is arranged radially outwardly from the inner gas curtain F1. The outer gas curtain F3 may be designed as shown in Figures 1-5. In particular, the main flow directions H of the two gas curtains F1 and F3 may differ from one another. Figure 6 illustrates that the vectors representing the main flow directions H enclose an angle y with one another.

[0052] Figure 7 shows a further alternative of the invention that can use a lidar sensor 10 according to Figures 1-6. As this drawing illustrates, the protective device 20 has nozzle arrangements 26 on opposite sides, each with one or more nozzles 25, to generate two gas curtains F1 and F4 that extend at least partially around the circumference.

[0053] The protective device 20 is arranged in an area in front of the light-emitting surface 12 of the lidar sensor 10. The arrangement of the protective device 20 is preferably selected such that it is arranged in an area in front of the light-emitting surface 12 that is not required for the transmission of light from the optical unit arranged in the receiving space.

[0054] The upper nozzle arrangement 26 generates a gas curtain F1 which extends from the nozzle arrangement 26 towards the upper side edge 15 of the light-emitting surface 12.

[0055] The lower nozzle arrangement 26 creates a gas curtain F4 that extends from the nozzle arrangement 26 toward the lower side edge 14 of the light-emitting surface 12. With the prescribed protective devices 20, a gas curtain F1-F4 can be created in front of the light-emitting surface 12, preventing particles from the environment from impinging on the light-emitting surface 12. These particles are intercepted and diverted by the gas curtain F1-F4. This ensures that the light-emitting surface 12 does not become contaminated. At the very least, contamination is greatly reduced.

Claims

Claims 1. An optical sensor, in particular a lidar sensor (10) having a receiving area in which an optical unit is arranged, wherein the optical unit is arranged in the area behind a transparent light-emitting surface (12), wherein the light-emitting surface (12) is arranged and designed to transmit light, in particular laser light, in particular to transmit light from the optical unit toward the environment and / or to transmit light from the environment toward the optical unit, characterized in that a protective device (20) is assigned to the light-emitting surface (12), which protective device is designed to protect at least a region of the surface of the light-emitting surface (12) facing the environment from contamination by means of a gas flow, that the protective device (20) has a gas guide with at least one nozzle arrangement (26), that the nozzle arrangement (26) has at least one nozzle (25),that the nozzle arrangement (26) is designed to generate a directed gas flow such that the gas flow on the ambient side generates a gas curtain (F1-F4) along the light-emitting surface (12) and preferably at least partially spaced from the light-emitting surface (12).

2. Optical sensor according to claim 1, characterized in that the nozzle (25) or at least some of the nozzles (25) of the nozzle arrangement (26) has / have a geometry by means of which a main flow direction (H) of the gas can be generated at the nozzle outlet (24), which main flow direction runs parallel or at an angle (a) measured perpendicular to the light emission surface (12).

3. Optical sensor according to claim 2, characterized in that the main flow direction (H) with the light emission surface (12) encloses an angle (a) measured perpendicular to the light emission surface (12) in the range between 0° and 60°, preferably in the range between 0° and 30°, particularly preferably between 0° and 15°.

4. Optical sensor according to one of claims 1 to 3, characterized in that the light emission surface (12) is designed, at least in regions, as a flat surface in front of which the gas curtain (F1-F4) can be generated in the surrounding area, and / or that the light emission surface (12) is designed, at least in regions, as a surface which is curved in the direction of the environment, in particular a cylindrical or partially cylindrical surface, in front of which the gas curtain (F1-F4) can be generated in the surrounding area.

5. Optical sensor according to claim 4, characterized in that the main flow direction (H) is inclined in the circumferential direction of the cylindrical or partially cylindrical light emission surface (12), wherein the angle of inclination (ß) is preferably selected in the range between 0° and 30°.

6. Optical sensor according to one of claims 1 to 5, characterized in that the gas outlet surface at the nozzle outlet (24) of the nozzle arrangement (26) is arranged at a distance from the light emission surface (12), wherein it is preferably provided that the gas outlet surface is arranged offset in the direction of the light emission surface (12) to the light emission surface (12) and / or offset transversely thereto, wherein the distance between the nozzle outflow surface and the sensor surface is preferably at most twice as large as the characteristic length of the sensor element, for example the diameter or the longest extension of the sensor element.

7. Optical sensor according to one of claims 1 to 6, characterized in that the nozzle arrangement (26) is arranged in the region of one side of the light emission surface (12), wherein it is preferably provided that a nozzle arrangement (26) is arranged on each opposite side of the light emission surface (12), and that the nozzle arrangement(s) (26) is / are arranged and designed to generate a gas curtain (F1-F4) directed towards the opposite side of the light emission surface (12).

8. Optical sensor according to one of claims 1 to 7, characterized in that the light emission surface (12) is delimited at least in the region of one side of the light emission surface (12) by means of a carrier (11, 13), and that the carrier (11, 13) carries the nozzle arrangement (26), wherein it is preferably provided that the light emission surface (12) is delimited at least on opposite sides by means of a respective carrier (11, 13), and that the two carriers (11, 13) each carry a nozzle arrangement (26).

9. Optical sensor according to one of claims 1 to 8, characterized in that the light emission surface (12) is limited on opposite sides by means of side edges (14, 15), and that the / a nozzle arrangement (26) of the protective device (20) is provided in the region between these side edges (14, 15).

10. Optical sensor according to claim 9, characterized in that the protective device (20) arranged between the side edges (14, 15) has a nozzle arrangement (26) on opposite sides, each facing a side edge (14, 15) of the light-emitting surface (12), for generating a gas curtain (F1, F4) directed towards the associated side edge (14, 15).

11. Optical sensor according to one of claims 1 to 10, characterized in that the nozzle arrangement (26) has at least one continuous or interrupted annular nozzle which is assigned to a light emission surface (12) designed as an at least partially circumferential surface, or in that the nozzle arrangement (26) has a plurality of individual nozzles.

12. Optical sensor according to one of claims 1 to 11, characterized in that the gas guide has two nozzle arrangements (26) which are arranged one behind the other perpendicular to the light emission surface (12), and that the main flow directions (H) of the two nozzle arrangements (26) run parallel to each other, or that the main flow directions (H) of the two nozzle arrangements (26) run at an angle (y) to each other, wherein preferably it is provided that the main flow directions (H) run perpendicular to the light emission surface (12) at an angle (Y) to one another.

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