Sensor arrangement for optical element in laser material processing head

Abstract

The present disclosure provides a sensor arrangement for reflecting scattered light from a laser beam, the sensor arrangement comprising: a first optical element; a cone of the housing, which is arranged behind the first optical element in the direction of the beam path of the laser beam, the cone of the housing comprising a conical stepped reflector, the shape of which corresponds to the shape of the cone of the housing, the cone of the housing being arranged behind the first optical element in the direction of the beam path of the laser beam, and the conical stepped reflector is formed by a plurality of ring elements, each ring element having a reflector surface on an inner side facing a beam path of the laser beam; and elements for receiving light reflected by the respective reflector surfaces of the plurality of annular elements, the elements being arranged on a side of the optical element opposite the cone of the housing. The invention further provides a laser material machining head and laser material machining equipment.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to German patent application DE102024123325.7, filed on August 15, 2024. The entire application of the above application is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to a sensor arrangement structure for monitoring optical elements in a laser material processing head and a method of using said sensor arrangement structure. Background Technology

[0004] Develop and manufacture lasers, laser processing heads and systems, their components and accessories, and laser measuring instruments. Laser processing heads and systems are designed for material processing, including welding, soldering, and cutting.

[0005] Laser processing heads and systems contain a large number of optical components. For beam shaping, laser processing systems use lenses, for example, to collimate or focus the laser beam. Optical components are typically arranged in groups along the optical axis and assembled in what is called a cylinder. Generally, the entire group of optical components can be replaced as needed, rather than replacing a large number of individual components.

[0006] During welding and cutting of workpieces, emissions may be generated and deposited near the processing area, thus limiting the function of laser optics due to deposits on optical surfaces. These deposits not only limit the performance of the optical system but can also damage or even destroy laser optics.

[0007] Therefore, it is necessary to monitor the deposition of dirt or emissions on the surface of optical components (such as protective glass or lenses).

[0008] Because the signal ratio between the desired beam path and the scattered radiation due to contamination or deposits after radiation via the optical element is significantly greater in the optical propagation direction than in the reverse direction, it is advantageous to place the sensor behind the optical element. To follow this advantageous arrangement, for example, a sensor used to monitor the process protective glass of cutting optics must be placed within a pressure or flow chamber of the cutting gas. On the one hand, the workload required to place the sensor there in a pressure-sealed manner and electrically connect it to the outside is very large; on the other hand, this arrangement interferes with the rotational symmetry of the cutting gas flow. Therefore, arranging the sensor in this way is disadvantageous.

[0009] A known solution from the prior art is to measure the scattered light signal on the cylindrical cladding surface of an optical element. The drawback of this solution is that the signal is highly dependent on the condition of the cladding surface, and the ratio of clean signal to contaminated signal transverse to the direction of light propagation is very low.

[0010] Furthermore, in the prior art, there are known arrangements in which the optical sensor is arranged in the opposite direction to the light propagation direction, and even when arranged in the light propagation direction, only a low signal-to-weight ratio can be achieved.

[0011] Another known arrangement structure is in which the sensor is arranged in the direction of light propagation to achieve a high signal-to-weight ratio, but it must also be arranged in the opposite direction of light propagation in space.

[0012] Furthermore, an arrangement is known in which the signal from the emitting diode is reflected off an optical surface. A drawback of this arrangement is that both elements must be positioned in the direction of light propagation, and interference is only caused by severe contamination.

[0013] The surface temperature of optical components can also be measured using a pyrometer. However, these optical components operate at wavelengths of 2–14 μm, which are almost impermeable to quartz glass, thus limiting their applications in the case of transmitted radiation. Summary of the Invention

[0014] Therefore, the purpose of this disclosure is to provide a sensor arrangement structure that avoids the drawbacks of existing technology solutions.

[0015] This disclosure provides a sensor arrangement structure for reflecting scattered light from a laser beam, the sensor arrangement structure comprising:

[0016] First optical element;

[0017] The housing has a cone-shaped portion arranged behind the first optical element in the direction of the laser beam path. The cone-shaped portion includes a conical stepped reflector, the shape of which corresponds to the shape of the housing's cone. The conical stepped reflector is formed by a plurality of annular elements, each annular element having a reflector surface on its inner side facing the laser beam path.

[0018] An element for receiving light reflected by the respective reflector surfaces of a plurality of annular elements, the elements being arranged on the side of the optical element opposite to the cone of the housing.

[0019] In one embodiment of the sensor arrangement, the element used to receive light reflected through the reflector surface is a light sensor.

[0020] This disclosure also proposes that the element for receiving light reflected through the reflector surface is a deflecting mirror for reflecting light onto a light sensor, in one embodiment of which is a photodiode.

[0021] In one embodiment of the sensor arrangement structure according to this disclosure, each of the respective reflector surfaces of the plurality of annular elements has a different tilt relative to the first optical element.

[0022] This disclosure also proposes that, in a sensor arrangement structure according to this disclosure, the respective reflector surfaces of the plurality of annular elements are configured such that they are aligned with elements for receiving light reflected by the respective reflector surfaces of the plurality of annular elements.

[0023] In one embodiment of the sensor arrangement, the optical sensor is connected to a receiving and evaluation device.

[0024] In the sensor arrangement structure described above, the conical stepped reflector is arranged within the cone of the housing.

[0025] In one aspect of the sensor arrangement structure, the conical stepped reflector is part of the cone of the housing.

[0026] Another object of this disclosure is to provide a laser material processing head, the laser material processing head comprising:

[0027] An opening for coupling a laser beam;

[0028] The sensor arrangement structure is as described above.

[0029] In one embodiment, the cone of the housing is a cutting gas cone through which the cutting gas flows.

[0030] Another object of this disclosure relates to a laser material processing apparatus, which includes a laser material processing head as described above and a device for moving the laser material processing head.

[0031] Another object of this disclosure relates to a method for monitoring contamination or dirt on optical components, the method comprising the following steps:

[0032] Guide the laser beam through the first optical element;

[0033] The scattered radiation of the first optical element is reflected by a conical stepped reflector arranged in the cone of the housing. The cone of the housing is arranged behind the first optical element in the direction of the laser beam path. The shape of the conical stepped reflector corresponds to the shape of the cone of the housing. The conical stepped reflector is formed by a plurality of annular elements, each annular element having a reflector surface on the inner side facing the laser beam path.

[0034] The reflected scattered radiation is received by means of elements for receiving light reflected from the respective reflector surfaces of a plurality of annular elements, the elements being arranged on the side of the optical element opposite to the cone of the housing.

[0035] In one embodiment of the method according to this disclosure, the element for receiving light reflected from the reflector surface is a light sensor.

[0036] The method can also be designed such that the element for receiving light reflected from the surface of the reflector is a deflector for reflecting light onto a light sensor.

[0037] Furthermore, the method according to this disclosure includes a photodiode as a light sensor.

[0038] In one embodiment, it is also proposed that the light received by the optical sensor be converted into an electrical signal, which is then processed by a receiving and evaluation device.

[0039] Other aspects, features, and advantages of this disclosure will become apparent from the following detailed description, which illustrates only preferred embodiments and implementations. This disclosure may also be implemented in other and different embodiments, and various details thereof may be modified in various obvious ways without departing from the teachings and scope of this disclosure. Therefore, the drawings and descriptions should be considered exemplary rather than limiting. Additional features and advantages of this disclosure are set forth in part in the description which follows, and will also be apparent in part from the description, or may be inferred from embodiments of this disclosure. Attached Figure Description

[0040] The present disclosure will now be described in more detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that these are merely possible and exemplary embodiments, and the present disclosure is not limited to the embodiments shown, wherein:

[0041] Figure 1 A shows a laser material processing head with a sensor arrangement structure for directly measuring reflected scattered light.

[0042] Figure 1 B shows a laser material processing head with a mirror for deflecting reflected scattered light onto a photosensor.

[0043] Figure 2 A conical stepped reflector is shown in detail in an embodiment having a protective glass as an optical element, the protective glass being in a protective glass drawer.

[0044] Figure 3 The cutting gas inlet at the beginning of the cutting gas cone is shown.

[0045] Figure 4The distribution of scattered light is shown starting from the protective glass, which serves as an optical element.

[0046] Figure 5 The signal-to-noise ratio distribution starting from the protective glass is shown.

[0047] Figure 6 The polar plot shows the signal ratio of dirty protective glass to clean protective glass.

[0048] Figure 7 The arrangement and tilt of the reflective inner surface of the reflector above the light sensor are shown. Detailed Implementation

[0049] The technical problem described herein is solved by the features of the independent claims. The dependent claims cover further specific embodiments of this disclosure.

[0050] For the purposes of this disclosure, optical elements can be understood as lenses, protective glass, mirrors, and beam shaping elements. The term "fixed" in relation to optical elements includes the centering and positioning of the optical element in the beam path.

[0051] This disclosure provides one or more reflectors arranged in a cylindrical or conical shape in the direction of light propagation, such that these reflectors reflect scattered light passing forward through an optical element back through the optical element. This scattered light can then be detected by an optical sensor arranged in the opposite direction of light propagation in front of the pressure chamber. The sensor may be, for example, a photodiode.

[0052] The reflective structure according to this disclosure can be embedded in a substrate of a gas guiding cone, typically made of aluminum. Therefore, the reflective structure according to this disclosure reflects light scattered forward by contaminated optical elements back to the sensor. Light from the cutting process is reflected laterally to the beam axis, making it difficult to reach the sensor. The inner contour of the reflective structure follows the conical cutting gas source, thus not interfering with the cutting gas flow. The structure can extend across one, several, or the entire conical region of the cutting gas tip.

[0053] Figure 1 A shows a laser material processing head having a sensor arrangement structure according to this disclosure. A laser beam 4 is coupled into the housing 1 of the laser material processing head on the left side of the illustrated embodiment. A collimating lens 2 is arranged in front of a focusing lens 3. The focused laser beam 4 passes through an optical element 6, which in the illustrated embodiment is a protective glass in a drawer 5, and also separates the interior of the cutting gas cone 9 from the rest of the interior of the housing 1. The cutting gas outlet 10 is also the laser processing point where the laser beam 4 is focused.

[0054] A conical stepped reflector 8 is arranged within a gas-cutting cone 9. The reflector 8 follows the conical shape of the gas-cutting cone, and is composed of a large number of annular elements. These annular elements have reflectors pointing inward in the direction of the optical element, resulting in a stepped shape with steps at different angles in the cross-section of the reflector. Because the gas-cutting cone is conical and its diameter gradually tapers, the individual annular elements of the reflector must form different angles relative to the surface of the optical element.

[0055] The light sensor 7 is positioned in the beam direction of the laser beam 4, in front of the optical element 6 (the protective glass in Figure 1), specifically on the side of the optical element 6 opposite to the reflector 8. The light sensor is arranged at an angle relative to the surface of the optical element 6 in the direction of the annular element of the reflector 8. Alternatively, a deflector 14 can be correspondingly arranged to deflect the light reflected from the annular element of the reflector 8 to the light sensor 7 (see Figure 1). Figure 1 B).

[0056] Figure 2 An embodiment of a conical stepped reflector is shown in detail behind an optical element 6, which serves as a protective glass and is arranged in a drawer 5. Behind the optical element 6 is a gas-cutting cone 9. A conical stepped reflector 8 is arranged behind the optical element 6.

[0057] Figure 3 The cutting gas inlet 11 at the beginning of the cutting gas cone 9 is shown. Also visible are the optical elements 6, reflector 8, light sensor 7, focusing lens 3, and housing 1 within drawer 5.

[0058] Figure 4 The scattered light distribution 12 is shown, starting from the optical element 6 arranged in drawer 5. The scattered light 12 is distributed on both sides of the optical element 6. The annular element of the conical stepped reflector 8 is arranged in the direction of propagation of the scattered light 12. The annular element of the conical stepped reflector 8 has an inner surface 81 (see...). Figure 7 This causes the scattered light beam to illuminate the corresponding inner surface at a 90° angle. The varying inclinations between the inner surfaces 81 are used to focus and reflect the scattered light onto the photosensor 7 (see [reference]). Figure 7 ).

[0059] Figure 5 The signal-to-noise ratio 13 distribution starting from optical element 6, which is arranged in drawer 5, is shown. It is easy to see that the arrangement and extension of the annular elements of the conical stepped reflector 8 are based on the signal-to-noise ratio distribution starting from optical element 6.

[0060] Figure 6A polar plot of the signal ratio 13 between the dirty protective glass 6 and the clean protective glass 6 is shown. The beam propagation direction in the image is from left to right along the optical axis 15. A signal ratio of 1:1 means that the scattered light signals from the clean and dirty optical elements are the same, therefore signal separation is not possible. The highest signal ratio of 1:5 (clean:dirty) is achieved in the beam propagation direction at 30° from the optical axis. No values ​​are displayed below 20° because the laser beam diverges here and cannot be measured.

[0061] Figure 7 The arrangement and tilt of the reflective inner surface 81 of the reflector above the light sensor 7 relative to the optical axis 15 are shown. The inner surface 81 reflects scattered radiation from a contaminated optical element (not shown) onto the sensor 7. In the broadest sense, alignment may be better. The reflector surface is arranged such that a laser beam scattered by particles from the center of the protective glass is reflected by the reflector surface and then directed toward the sensor. However, the refraction of light through the protective glass must also be considered.

[0062] The technical advantage of this disclosure is that dirt or contamination of an optical element can be determined without arranging a light sensor or other sensor in the direction of the light beam path behind the corresponding optical element. The shape and arrangement of the conical stepped reflector allow for the determination of contamination in the optical element.

[0063] The advantage of the device according to this disclosure is that it is sufficient to arrange the reflector behind the optical element, so that the function of the laser material processing head is not affected from the perspective of interfering with the flow of cutting gas or affecting the laser beam.

[0064] Other aspects, features, and advantages of this disclosure will become apparent from the foregoing detailed description, which illustrates only preferred embodiments and implementations. This disclosure may also be implemented in other and different embodiments, and various details thereof may be modified in various obvious ways without departing from the teachings and scope of this disclosure. Therefore, the drawings and descriptions should be considered exemplary rather than limiting. Additional features and advantages of this disclosure are set forth in part in the foregoing description and will be apparent in part from the description, or may be inferred from embodiments of this disclosure.

[0065] List of reference numerals in the attached diagram:

[0066] 1. Shell

[0067] 2. Collimating lens

[0068] 3. Focusing lens

[0069] 4. Laser beam

[0070] 5 drawers

[0071] 6 Optical Components

[0072] 7. Light sensor

[0073] 8. Conical reflector

[0074] 81 Inner Surface

[0075] 9. Cutting the gas cone

[0076] 10 Cutting Gas Outlet - Laser Processing Point

[0077] 11 Cut the gas inlet

[0078] 12 Stray light distribution starting from the protective glass

[0079] 13 Signal-to-noise ratio distribution starting from the protective glass

[0080] 14 Deflecting Mirror

[0081] 15 optical axes

Claims

1. A sensor arrangement structure for reflecting scattered light from a laser beam, the sensor arrangement structure comprising: First optical element; The housing has a cone-shaped structure arranged behind the first optical element in the direction of the laser beam path. The cone-shaped structure includes a conical stepped reflector, the shape of which corresponds to the shape of the housing cone. The conical stepped reflector is formed by a plurality of annular elements, each annular element having a reflector surface on its inner side facing the laser beam path. and An element for receiving light reflected by the respective reflector surfaces of a plurality of annular elements, the elements being arranged on the side of the first optical element opposite to the cone of the housing.

2. The sensor arrangement structure according to claim 1, wherein, The element used to receive light reflected from the surface of a reflector is a light sensor.

3. The sensor arrangement structure according to claim 1, wherein, The element used to receive light reflected from the reflector surface is a deflector mirror used to reflect the light onto the light sensor.

4. The sensor arrangement structure according to claim 2 or 3, wherein, The optical sensor is a photodiode.

5. The sensor arrangement structure according to any one of claims 1 to 4, wherein, Each of the respective reflector surfaces of the plurality of annular elements has a different tilt relative to the first optical element.

6. The sensor arrangement structure according to any one of claims 1 to 5, wherein, The respective reflector surfaces of the plurality of ring elements are formed such that they are aligned with elements for receiving light reflected through the respective reflector surfaces of the plurality of ring elements.

7. The sensor arrangement structure according to any one of claims 2 to 6, wherein, The optical sensor is connected to the receiving and evaluation device.

8. The sensor arrangement structure according to any one of claims 1 to 7, wherein, The conical stepped reflector is arranged within the cone of the housing.

9. The sensor arrangement structure according to any one of claims 1 to 7, wherein, The conical stepped reflector is part of the cone of the housing.

10. A laser material processing head, the laser material processing head comprising: An opening for coupling a laser beam; and The sensor arrangement structure according to any one of claims 1 to 7.

11. The laser material processing head according to claim 10, wherein, The cone of the housing is a cutting gas cone through which the cutting gas flows.

12. A laser material processing apparatus, the laser material processing apparatus comprising a laser material processing head according to claim 8 or 9, and a device for moving the laser material processing head.

13. A method for monitoring contamination or dirt on optical components, the method comprising the following steps: Guide the laser beam through the first optical element; The scattered radiation of the first optical element is reflected by a conical stepped reflector arranged in the cone of the housing. The cone of the housing is arranged behind the first optical element in the direction of the laser beam path. The shape of the conical stepped reflector corresponds to the shape of the cone of the housing. The conical stepped reflector is formed by a plurality of annular elements, each annular element having a reflector surface on the inner side facing the laser beam path. The reflected scattered radiation is received by an element for receiving light reflected from the respective reflector surfaces of a plurality of annular elements, the element being arranged on the side of the first optical element opposite to the cone of the housing.

14. The method of claim 10, wherein, The element used to receive light reflected from the surface of the reflector is a light sensor.

15. The method according to claim 10, wherein, The element used to receive light reflected from the surface of the reflector is a deflector used to reflect the light onto a light sensor.

16. The method according to claim 11 or 12, wherein, The optical sensor is a photodiode.

17. The method according to any one of claims 11 to 13, wherein, The light received by the optical sensor is converted into an electrical signal, which is then processed by a receiving and evaluation device.

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