Imaging device, laser machining tool with imaging device, and method for determining a process variable - Patents.com

Abstract

The present invention relates to an imaging device (12) for imaging a process zone (14) of a laser machining tool (10), the imaging device comprising an image sensor (28) and an optical imaging system (30) positioned between the process zone (14) and the image sensor (28). The optical imaging system (30) has a system axis (32) extending between the image sensor (28) and the process zone (14), a first aperture (34) radially spaced from the system axis (32), and a second aperture (36). Light rays (40, 44) emitted from the process zone (14) at different imaging angles (38, 42) are subtended by the apertures (34, 36). The optical imaging system (30) is designed to image the first light beam (40) spatially separated from the second light beam (44). The present invention also relates to a laser machining tool (10) equipped with such an imaging device (12), and to a method for determining a process variable using such an imaging device (12).

Description

[Technical Field]

[0001] The present invention relates to an imaging device having an optical imaging system for imaging a process zone of a laser machining tool onto an image sensor. The invention also relates to a laser machining tool having an imaging device and a method for determining a process variable.

[0002] Such devices and methods are known in various embodiments from the prior art and serve to monitor laser machining processes. Typically, an imaging device displays a three-dimensional image of the process zone as a two-dimensional image on an image sensor. From the analysis of the image of the process zone, important functional and control variables for common laser cutting machines can be derived if the image is sufficiently accurate, which can support, for example, feed control or cutting error detection during laser machining.

[0003] WO 2016 / 062636 A1 describes a device for measuring the depth of a weld seam when welding or joining workpieces by radiation. The device can be tilted relative to the processing beam as a function of the feed rate, so that the inclination of the weld seam depending on the feed rate can be taken into account. However, although variable, the representation of the weld seam from only one angle may convey insufficient information about the process zone. For example, information may be lost due to a reduced imaging area.

[0004] WO2016 / 181359A1 describes a laser processing device having at least one group of detector arrangements. The detector arrangements are arranged in a ring around the optical axis of the laser cutting device. The detector arrangements are designed to detect the process zone at various static angles. The described detector arrangements impose structural requirements that must be taken into account when implementing the described principles and require complex evaluation routines to evaluate the detected information.

[0005] DE 10 2013 / 218421 A1 describes a device for monitoring a laser cutting process on a workpiece with an image capture device, where the observation beam is formed at an observation angle oblique to the laser beam, and the device can also have multiple observation directions with the same observation angle.

[0006] The above-mentioned devices have the possibility to image the process zone from different directions, for example, by rotating the device. However, the devices only image the process zone at a single, predetermined angle. This may result in the process zone being imaged inaccurately. For example, important information cannot be imaged by the device at only one predetermined angle. The "geometric visibility" of the process zone typically depends on the nozzle diameter of the laser machining tool, the material thickness of the workpiece being machined, the distance between the nozzle and the workpiece, and the radiation characteristics of the laser machining process. [Background technology]

[0007] It is an object of the present invention to provide a device and associated method for imaging the process zone of a laser processing device that allows for reliable determination of process variables from the image.

[0008] Summary of the Invention This object is achieved according to the invention by an imaging device having the features of claim 1. The object is also achieved by a laser machining tool having the features of claim 18 and by a method having the features of claim 19. The subclaims represent preferred embodiments of the invention.

[0009] An imaging device is provided in accordance with the present invention. The imaging device is suitable for imaging a process zone of a laser machining tool. Typically, the process zone is optically imaged by imaging light emitted from the process zone.

[0010] The imaging device comprises an image sensor, typically designed for two-dimensional imaging of optical radiation, preferably in the ultraviolet (UV) to near infrared (SWIR) spectral range, particularly preferably between 350 nm and 1800 nm. Preferably, the image sensor is semiconductor-based.

[0011] The imaging device also includes an optical imaging system disposed between the process zone and the image sensor. The optical imaging system is preferably designed to guide and direct optical radiation emitted from the process zone to the image sensor. More preferably, the optical imaging system is designed to deflect the processing beam of the laser processing device toward the workpiece being processed.

[0012] The optical imaging system has a system axis extending between the image sensor and the process zone. To simplify the description of the invention, the system axis can be understood as an ideal axis. The ideal axis can be replaced by a practically commonly used optical path, which may consist of sections inclined relative to one another. Those skilled in the art can transfer the invention starting from the system axis to the optical path, for example, to structurally allow for an offset between the process zone and the image sensor.

[0013] The optical imaging system also has a first aperture radially spaced from the system axis. The first aperture is preferably designed perpendicular to the system axis. The first aperture defines a first light ray emitted from the process zone at a first imaging angle. In other words, the first aperture only allows the optical radiation emitted from the process zone to pass through at a certain angle.

[0014] The optical imaging system also includes a second aperture. Preferably, the second aperture is designed to be perpendicular to the system axis. The second aperture may be radially spaced apart from the first aperture, particularly relative to the system axis. The second aperture defines a second light beam emitted from the process zone at a second imaging angle.

[0015] The optical imaging system also includes a first imaging lens disposed between the aperture and the image sensor. In other words, the first imaging lens is disposed before the first imaging lens in the ray path of the optical imaging system. As a result, the optical imaging system is designed to integrate additional optical components between the aperture and the first imaging lens. The additional optical components may be integrated into the optical imaging system, for example, in the form of optical filters. This allows the optical imaging system to be used to perform optical measurement techniques, such as stereometry / stereopsis, ratiometric pyrometry, angle measurement, or spectral analysis.

[0016] The first imaging lens is typically designed as a converging lens, and is designed to image at least the first and second light rays onto the image sensor.

[0017] According to the present invention, the first imaging angle is different from the second imaging angle. In other words, the first light ray subtended by the first aperture has a different imaging angle from the second light ray subtended by the second aperture. The imaging angle is the angle enclosed between each light ray and the system axis. In other words, several light rays may have the same angle value but radiate in different directions from the process zone. The imaging angle may be zero degrees.

[0018] The optical imaging system is further designed to image the first light beam spatially separated from the second light beam, and the first light beam and the second light beam are typically imaged onto an image sensor.

[0019] In other words, the basic objective is achieved by designing an imaging device to simultaneously or jointly image the process zone at at least two different imaging angles, while the remaining optical radiation emitted by the process zone is hidden, reflected, or absorbed. Furthermore, the process zone is imaged from at least two directed imaging angles, thereby increasing the area of ​​the process zone that can be imaged by the imaging device. Furthermore, simultaneous imaging of the two light beams is performed spatially separated on the image sensor, thus allowing the images to be assigned to the imaging angles. With knowledge of the imaging angles, the images of the process zone can be used for geometric comparison. In other words, the process zone can be analyzed in three dimensions. From the three-dimensional analysis, process variables such as the length of the processing front of the laser machining tool, spatially resolved temperature measurements, and / or temperature distribution within the process zone can be reliably determined. This makes it possible to increase the quality of laser processing by, for example, detecting the formation of plasma or metal vapor and avoiding cutting errors.

[0020] In a preferred embodiment of the imaging device, the optical imaging system has a directional lens arranged between the process zone and the aperture. The directional lens can align the light beam emitted from the process zone parallel to the system axis onto the aperture. In other words, the imaging device can form a collimator, which allows the light beam to be particularly precisely defined by the aperture.

[0021] Another preferred embodiment of the imaging device is one in which the optical imaging device has a third aperture, which can subtend a third light ray emitted from the process zone at a third imaging angle. The additional aperture can further improve the three-dimensional view of the process zone.

[0022] In a preferred further development of the imaging device, the third imaging angle is different from the first and / or second imaging angle, which allows for a further and more accurate determination of the process variable.

[0023] A further development of the imaging device is particularly preferred in that the optical imaging system is designed to image the third light beam spatially separated from the first and / or second light beam onto the image sensor. Preferably, all light beams are imaged spatially separated from one another onto the image sensor. This allows the image to be evaluated with a clear allocation for each imaging angle.

[0024] In a preferred embodiment of the imaging device, the optical imaging system has a process zone opening, which can be specifically designed as a processing nozzle of a laser machining tool, which makes it possible to limit the total number of light rays emitted from the process zone in the direction of the imaging device, thereby increasing the imaging accuracy of the light rays.

[0025] In a preferred embodiment of the imaging device, the apertures are formed on a common aperture disk. The common aperture disk is preferably arranged perpendicular or orthogonal to the system axis. The common aperture disk allows particularly accurate spacing of the apertures from each other, especially when the apertures are moved. Preferably, the aperture disk can be designed as a coated glass substrate. Particularly preferably, the aperture disk transmits light radiation within the area of ​​the aperture and attenuates, absorbs or reflects light radiation outside the aperture.

[0026] In a preferred further development of the imaging device, the aperture disc is designed to be rotatable about the system axis. Preferably, the aperture disc is designed to be rotatable according to the machining direction of the laser machining tool. This allows the image of the light beam to be maintained in relation to the formation of the process zone according to the machining direction. For example, a clear image of the process zone can be clearer if the direction of laser machining is changed by 90 degrees, for example, if the aperture disc is also rotated by 90 degrees.

[0027] In a preferred further development of the imaging device, the optical imaging system has a first optical rotational decoupling downstream of the first aperture. The first optical rotational decoupling is typically designed to positionally correctly image the first light beam on the image sensor independently of the rotation of the aperture disk. In other words, the first light beam can be imaged on the same imaging area of ​​the image sensor regardless of the machining direction of the laser machining tool. This makes it particularly easy to assign an imaging angle to the image. Furthermore, the dimensions of the image sensor can be kept particularly compact.

[0028] A further development of the imaging device is particularly preferred, in which the system axis intersects the image sensor at an imaging node. Preferably, the first imaging lens in this case is designed for imaging the first light beam centered on the imaging node. By imaging the first light beam at the imaging node, static imaging of the first light beam can be achieved.

[0029] In a particularly preferred further development of the imaging device, in which the system axis runs through the center of the second aperture, the imaging device has at least one optical wedge arranged upstream of the first imaging lens and downstream of the second aperture. In other words, in this case, the second aperture defines a second light beam extending coaxially with the system axis, optically independent of any rotation of the second aperture. The optical wedge is preferably designed to deflect the second light beam onto the first imaging lens at an angle relative to the system axis. By deflecting the second light beam, the position of the image on the image sensor can be determined. Preferably, the second light beam is imaged toward an imaging area on the image sensor that is outward or away from the imaging intersection. This allows for correct positioning of the second light beam and rotation-independent imaging without rotational decoupling.

[0030] Alternatively, in a further development of the imaging device having a system axis extending through the center of the second aperture, an optical imaging system can be provided having a first optical subsystem with a second imaging lens. The first optical subsystem or the second imaging lens is preferably designed to positionally correctly image the second light beam onto the image sensor. The second imaging lens can be used to avoid optical overlap of the light beams within the first imaging lens and therefore increase imaging accuracy. By forming the optical subsystem, an optical path with different spectral transmission characteristics can be provided, the optical path being separate from the optical path of the first light beam. This allows the process zone to be imaged with other spectral characteristics, further improving analysis of the process zone.

[0031] A further development of the imaging device is particularly preferred in that the first optical subsystem comprises a first deflection mirror downstream of the aperture, the first deflection mirror being designed to deflect the second light beam. Preferably, the first deflection mirror is designed to deflect a specific wavelength of the second light beam. In particular, unwanted wavelengths can be filtered out. This allows for particularly accurate imaging of the second light beam.

[0032] In a preferred further development of the imaging device in conjunction with the third aperture, the optical imaging system may be provided with a second optical subsystem downstream of the third aperture, which second optical subsystem is preferably designed in particular for positionally correct imaging of the third light beam onto the image sensor, independently of rotation of the aperture disc.

[0033] A further development of the imaging device is particularly preferred in that the second optical subsystem comprises a second deflection mirror downstream of the aperture, which is preferably designed to deflect a specific wavelength of the third light beam, thereby enabling the third light beam to be imaged within a predetermined spectral range.

[0034] In a preferred embodiment of the imaging device, the optical imaging system is designed to image a beam of light onto a single image sensor.

[0035] The basic object is also achieved by a laser machining tool having an imaging device as described above and below.

[0036] The laser machining tool typically includes a laser processing unit for forming the laser beam. In addition, the laser machining tool typically includes a machining control system. The machining control system may be configured to control or adjust the laser processing unit and / or the imaging device.

[0037] Preferably, the machining control system comprises an evaluation unit, which is particularly preferably configured for evaluating the image on the image sensor.

[0038] Furthermore, the basic object is achieved by a method for determining a process variable of a process zone by means of an imaging device as described above and below, the method comprising the following method steps:

[0039] In one method step, at least a first image and at least a second image of the process zone are created. The images are typically created on an image sensor by the first and second light beams. Preferably, a third image can be generated by a third light beam.

[0040] In a further method step, at least a first imaging angle and a second imaging angle are provided. The imaging angles may be provided, for example, by a machining control and / or by an operator of the imaging device.

[0041] In a subsequent method step, at least the first image is compared with the second image. Preferably, the geometric content of the images is compared with one another.

[0042] Based on the comparison, at least one process variable is determined or calculated.

[0043] Further features and advantages of the invention can be found in the description, the claims and the drawings. According to the invention, the above-mentioned and further described features can be used in each case individually or together in any desired suitable combination. The illustrated and described embodiments should not be understood as an exhaustive list, but rather as exemplary features for explaining the invention. [Brief explanation of the drawings]

[0044] [Figure 1] 1 shows a schematic representation of a laser machining tool with a first embodiment of an imaging device according to the invention, the imaging device comprising an image sensor and an optical imaging system. [Figure 2] 2 shows a schematic representation of a second embodiment of an imaging device; [Figure 3] 3 shows in a schematic representation a third embodiment of an imaging device; [Figure 4] 4 shows in a schematic representation the image sensor from FIG. 3; [Figure 5] 4 shows the aperture disk from FIG. 3 in a schematic view. [Figure 6] 1 shows a schematic representation of a method according to the present invention.

[0045] 1 shows a laser machining tool 10 having an imaging device 12 for imaging a process zone 14 of the laser machining tool 10. In the case shown, the process zone 14 is designed as the processing area or emission area of ​​a laser beam (not shown in more detail) of the laser machining tool 12.

[0046] The laser beam passes through the processing nozzle 16 of the laser machining tool 10 during the machining process in the direction of the workpiece 18 to be processed. For better processing, the workpiece 18 can be placed on a workpiece support 20, preferably in the form of a web, as in the illustrated case. By irradiating the workpiece 18, the workpiece can be melted and / or at least partially vaporized in the effective range of the laser beam. When the laser machining tool 10 moves in the processing direction 22, the workpiece 18 to be processed can be cut, for example, along a cutting edge 24. In the transition area between the workpiece 18 and the cutting edge 24, a processing front 26 is formed on the workpiece 18 due to the duration of irradiation by the laser beam. Important information regarding the machining process can be derived from the formation of the processing front 26. The design of the processing front 26 is therefore important for controlling or regulating the laser machining tool 10 and must be monitored, for example, to ensure high processing speeds and / or processing quality.

[0047] According to the embodiment shown, the imaging device 12 is arranged on the laser machining tool 10, preferably integrated into the laser machining tool 10. The imaging device 12 comprises an image sensor 28 and an optical imaging system 30 arranged between the process zone 14 and the image sensor 28. The optical imaging system 30 is arranged along a system axis 32 and extends between the image sensor 28 and the process zone 14. Preferably, the system axis 32 is designed as the optical axis of the optical imaging system 30. In other words, the optical imaging system 30 may be designed to be at least primarily rotationally symmetric with respect to the system axis 32. The system axis 32 is also preferably designed to be orthogonal to the workpiece 18 being machined. The optical imaging system 30, and in particular the entire imaging device 12, may be arranged to be orthogonal to the workpiece 18 being machined.

[0048] The optical imaging system 30 has a first opening 34 that is radially spaced from the system axis 32. In addition, the optical imaging system 30 has a second opening 36. The second opening 36 is disposed at a distance, particularly radially, from the first opening 34. According to the embodiment shown, the second opening 36 may be disposed centrally with respect to the system axis 32.

[0049] The first aperture 34 subtends a first light ray 40 emitted from the process zone 14 at a first imaging angle 38. The second aperture 36 subtends a second light ray 44 emitted from the process zone 14 at a second imaging angle 42. The imaging angles 38, 42 may be determined as the inclination of the respective light rays 40, 44 with respect to the system axis 32. According to the embodiment shown, the second light ray 44 is emitted parallel to the system axis 32, which is why the second imaging angle 42 here is zero degrees. The first imaging angle 38 is different in size from the second imaging angle 42. Preferably, the first imaging angle is between 3 and 4 degrees.

[0050] The first light ray 40 and the second light ray 44 are imaged spatially separated onto the image sensor 28 by the optical imaging system 30, thereby allowing for a perspective view of the process zone 14. The ray paths of the first light ray 40 and the second light ray 44 are shown interrupted by two horizontal lines 46 for a more compact representation.

[0051] According to the embodiment shown, the optical imaging system 30 may have a process zone opening 48, here formed on the processing nozzle 16. The process zone opening 48 defines the light rays emanating from the process zone 14, such as the first and second light rays 40, 44. This can reduce stray radiation and improve imaging of the first and second light rays 40, 44.

[0052] The optical imaging system 30 may include a directional lens 50. The directional lens 50 may be disposed in the process zone 14, particularly between the process zone opening 48 and the first and / or second openings 34, 36. Preferably, the directional lens 50 aligns the first and / or second light beams 40, 44 emitted from the process zone 14 parallel to the system axis 32. As a result, the imaging device 12 may be kept compact in its radial dimension relative to the system axis 32.

[0053] The optical imaging system 30 includes a first imaging lens 52. The first imaging lens 52 is disposed between the apertures 34, 36 and the image sensor 28. The first imaging lens 52 is typically designed to image the first light beam 40 and / or the second light beam 44 onto the image sensor 28. As shown in FIG. 1 , the imaging lens 52 forms the first light beam 40 in a first imaging area 54 and the second light beam 44 in a second imaging area 56 on the image sensor 28. The first imaging area 54 is spatially separated from the second imaging area 56.

[0054] According to an embodiment, a single image sensor 28 is provided. Alternatively or additionally, the imaging device 12 may have multiple image sensors 28 for imaging the light rays 40, 44. The image sensor 28 and the imaging areas 54, 56 with the first and second light rays 40, 44 imaged onto the image sensor 28 are shown in detail as a top view for better illustration.

[0055] 1, the first light beam 40 is inclined in the processing direction 22, thereby generating a "sharp image" of the process zone 14. In other words, the "sharp image" allows an oblique view of the process zone 14 and the processing front 26 in the processing direction 22. From this, for example, a first length 58 of the processing front 26 according to the first imaging angle 38 can be determined.

[0056] The second light ray 44 is not tilted relative to the system axis 32, which results in a "center image" of the process zone 14. In other words, the "center image" allows for a central view of the process zone 14 and the processing front 26, independent of the processing direction 22. From this, for example, a second length 60 of the processing front 26 can be determined by the second imaging angle 42.

[0057] In a geometrical comparison of the determined lengths 58, 60 of the processing front 26, further geometrical variables of the process zone 14 can then be determined, such as for example the current penetration depth of the laser beam.

[0058] The optical imaging system 30 may have an aperture disk 62. For better illustration, the aperture disk 62 is shown in more detail as a top view. The first apertures 34 and the second apertures 36 may be formed on the (common) aperture disk 62. This facilitates accurate positioning of the first apertures 34 relative to the second apertures 36, which has a beneficial effect on the imaging accuracy of the process zone 14.

[0059] The aperture disc 62 may be designed to be rotatable about the system axis 32, as indicated by arrow 64. This allows the imaging device 12 to be adapted to changed processing directions 22 of the laser machining tool 10. For example, if the processing direction 22 shown in FIG. 1 is reversed, the optical imaging system 30 will image the process zone 14 opposite to the processing direction 22. This can be prevented by rotating the aperture disc 62 180 degrees.

[0060] The optical imaging system 30 may, as shown, have a first rotational decoupling 66 located downstream of the first aperture 34. According to the embodiment shown, the first rotational decoupling 66, here in the form of an imaging lens 52, is designed as a converging lens that is rotationally symmetric about the system axis 32. The system axis 32 corresponds to the optical axis of the imaging lens 52. The first rotational decoupling 66 images the first light ray 40, which is subtended by the first aperture 34, into the imaging area 54 of the image sensor 28. The imaging area 54 is centered on an imaging intersection 68 of the system axis 32 with the image sensor 28, so that the first light ray 40 can be correctly positioned with respect to the system axis 32, regardless of any displacement or rotation of the first aperture 34 about the system axis 32. In other words, the first light ray 40 can be imaged in the fixed imaging area 54, regardless of the rotation of the first aperture 34. The position of the image on the image sensor 28 therefore does not change.

[0061] 1 , the optical imaging system 30 for spatially distant imaging of the second light rays 44 onto the image sensor 28 includes an optical wedge 70. The optical wedge 70 is designed to direct the second light rays 44 onto the imaging lens 52 at an angle relative to the system axis 32. The oblique illumination of the imaging lens 52 causes the second light rays 44 to be imaged onto the image sensor 28 at a radial distance from the imaging node 70. The centered placement of the second aperture 36 on the system axis 32 allows positionally accurate imaging of the second light rays 44 in the imaging area 56 of the image sensor 28, regardless of rotation of the second aperture 36 about the system axis 32. In this embodiment, rotational decoupling may be omitted.

[0062] 2 shows, in a schematic representation, a second embodiment of the imaging device 12. The optical imaging system 30 has a first rotational decoupling 66 that enables rotation-independent and positionally accurate imaging of the first light beam 40 by the first imaging lens 52 within the imaging area 54 of the image sensor 28.

[0063] Additionally, the optical imaging system 30 includes a first optical subsystem 72 that is designed to image the second light beam 44 onto the image sensor 28, spatially separated from the first light beam 40. According to the embodiment shown, the first optical subsystem 72 includes a first deflecting mirror 74, a second deflecting mirror 76, a second imaging lens 78, and an imaging prism 80.

[0064] The first deflecting mirror 74 is disposed between the openings 34, 36 and the first imaging lens 52 and is configured to deflect the second light beam 44. As shown, the second light beam 44 may be directed by the first deflecting mirror 74 past the first imaging lens 52 and onto the second deflecting mirror 76.

[0065] The second deflection mirror 76 may be designed to align the second light beam 44. Preferably, the second deflection mirror 76 aligns the second light beam 44 parallel to the system axis 32. In other words, the deflection mirrors 74, 76 cause a parallel displacement of the second light beam 44 from the system axis 32 or a radial separation of the second light beam 44.

[0066] The second light beam 44 may then be imaged onto the image sensor 28 by the second imaging lens 78, which may improve image quality.

[0067] To keep the size of the image sensor 28 small, it may be provided that the radial separation caused by the deflecting mirrors 74, 76 is partially or completely compensated for by an imaging prism 80, as shown.

[0068] FIG. 3 shows a schematic representation of a third embodiment of the imaging device 12 .

[0069] The optical imaging system 30 has a first aperture 34 radially spaced from a system axis 32, a second aperture 36, and a third aperture 82. The apertures 34, 36, 82 may be designed on a common aperture disk 62.

[0070] First light ray 40 subtended by first aperture 34 is imaged by imaging lens 52 at first imaging area 54 on image sensor 28. Similar to Figure 2, second light ray 44 is imaged by first optical subsystem 72 or second imaging lens 78 at second imaging area 56 onto image sensor 28.

[0071] The third opening 82 may be positioned at a distance, particularly a radial distance, from the first opening 34 and / or from the second opening 36. The third opening 36 is typically designed to define a third light beam 84 that radiates from the process zone 14 at a third imaging angle 86. The third imaging angle 86 may be tilted opposite to the processing direction 22. The optical imaging system 30 is designed to image the third light beam 84 onto the image sensor 28, particularly at a third imaging area 88.

[0072] The optical imaging system 30 may include a second optical subsystem 90 configured to image the third light beam 84 onto the image sensor 28, as shown. The second optical subsystem 90 may include a third deflecting mirror 92, a fourth deflecting mirror 94, a third imaging lens 96, and a second imaging prism 98.

[0073] The second optical subsystem 90 may be configured similarly to the first optical subsystem 72 to radially space the third light rays 84. To this end, a deflection of the first light rays 84 from a direction parallel to the system axis 32 may be provided, with the deflected third light rays 84 subsequently updated to a parallel alignment with the system axis 32. An image of the third light rays 84 may therefore be generated in a positionally correct manner via a third imaging lens 96 and an imaging prism 98, particularly at a stationary third imaging area 88.

[0074] 3, the second optical subsystem 90 is also designed as a second rotational decoupling 100. This allows for positionally correct imaging of the third light beam 84 even when the third aperture 82 or aperture disk 62 rotates.

[0075] The third deflection mirror 92 of the second optical subsystem 90 may be designed to be rotationally symmetric with respect to the system axis 32 in a plane perpendicular to the system axis 32. The third deflection mirror 92 may be circular in the plane perpendicular to the system axis 32, with an inner diameter smaller than the minimum distance of the third opening 82 from the system axis 32 and an outer diameter larger than the maximum distance of the third opening 82 from the system axis 32. Preferably, the deflection mirror 92 is designed as a circumferential ring in the plane perpendicular to the system axis 32. In other words, the deflection mirror 92 has a dimension in the plane projected toward the system axis 32 that corresponds at least to the circumferential projection surface of the third opening 82. This is a maximum regardless of the rotation of the third opening 82. The annular design of the third deflection mirror 92 allows the first light ray 40 and the second light ray 44 to pass through without optical obstruction when the openings 34, 36, 82 each have a circumferential projected surface that is radially spaced apart, in other words, when the circumferential projected surfaces of the openings 34, 36, 82 do not overlap.

[0076] Alternatively, as shown in Fig. 3, the deflecting mirror 92 may be designed to deflect light rays in a predetermined wavelength range, while light rays outside the predetermined wavelength range are transmitted. For this purpose, at least one optical bandpass filter 102 may be connected before the deflecting mirror 92. Preferably, each of the openings 34, 36, 82 has an optical bandpass filter 102 that predefines the wavelength range of the respective light rays 40, 44, 84. This allows light rays 40, 44, 84 with overlapping circumferential projection surfaces to be optically separated.

[0077] Also, based on the polarization properties, further information can be recorded. At least one of the apertures 34, 36, 82 can be provided with a polarizing filter, for example for filtering s-polarized and p-polarized light, as an alternative or in addition to the optical bandpass filter 102. By means of the polarizing filter, a corresponding "polarized" image can be displayed and / or used for measurement purposes.

[0078] Figure 4 shows in a schematic view the image sensor 28 from Figure 3. The imaging areas 54, 56, 88 are spatially separated from one another and are arranged at fixed positions on the image sensor 28. In other words, the positions of the imaging areas 54, 56, 88 on the image sensor 28 do not change when the processing direction 22 (see Figure 1) or the rotational position of the aperture disc 62 (see Figures 1 to 3, 5) changes.

[0079] The first imaging area 54 shows a "sharp image" of the process zone 14 (see FIG. 1), by which, for example, a first length 58 of the processing front 26 can be determined, according to the first imaging angle 38 (see FIG. 1). Furthermore, the second imaging area 56 shows a "centered image" of the process zone 14, by which, for example, a second length 60 of the processing front 26 can be determined, according to the second imaging angle 42 (see FIG. 1). In addition, the third imaging area 88 shows a "blurred representation" of the process zone 14 (see FIG. 3) opposite to the processing direction 22 (see FIG. 3), caused by the third imaging angle 86, by which, for example, a third length 104 of the processing front 26 can be determined.

[0080] The additional information regarding the third image can further refine the determination of the geometric dimensions of the process zone 14 .

[0081] FIG. 5 shows in a schematic view the aperture disk 62 from FIG.

[0082] The aperture disc 62 is designed to be rotatable about the system axis 32, as indicated by arrow 64. The apertures 34, 36, 82 are formed in the aperture disc 62 spatially separated from one another. The second aperture 36 is formed in the aperture disc 62 centrally relative to the system axis 32.

[0083] The first aperture 34 and the third aperture 82 are offset by 180 degrees on the aperture disk 62 and have different radial distances from the system axis 32 .

[0084] The trajectory 106, indicated by the dotted circle, of the first aperture 34 overlaps with the third aperture 82. This can lead to optical overlap of the first and third light rays 40, 84, which can blur the image on the image sensor 28 (FIGS. 1-4). To avoid optical overlap, the apertures 34, 36, 82, here particularly the first and third apertures 34, 82, can be provided with optical bandpass filters 102.

[0085] FIG. 6 illustrates schematically a method 108 for determining process variables, particularly geometrical variables, of a process zone 14 (see FIG. 1) by means of an imaging device 12 (see FIG. 1).

[0086] The method 108 comprises the following method steps (see also FIG. 1 below):

[0087] In one method step 110, first and second images are created of the process zone 14. The first and second images are typically created by imaging the first and second light beams 40, 44 at first and second imaging areas 54, 56 of the image sensor 28.

[0088] In a further method step 112, a first imaging angle 38 and a second imaging angle 42 are provided.

[0089] A subsequent method step 114 provides a geometric comparison of the first image with the second image, and at least one process variable is determined or calculated by the geometric comparison.

[0090] When all figures in the drawings are taken together, the present invention relates to an imaging device (12) for imaging a process zone (14) of a laser machining tool (10), the imaging device comprising an image sensor (28) and an optical imaging system (30) located between the process zone (14) and the image sensor (28). The optical imaging system (30) has a system axis (32) extending between the image sensor (28) and the process zone (14) and a first aperture (34) radially spaced from the system axis (32) and a second aperture (36). Light rays (40, 44) emitted from the process zone (14) at different imaging angles (38, 42) are subtended by the apertures (34, 36). The optical imaging system (30) is designed to image the first light beam (40) spatially separated from the second light beam (44). The present invention also relates to a laser machining tool (10) having an imaging device (12) and a method for determining a process variable. [Explanation of symbols]

[0091] 10 Laser Machining Tools 12 Imaging devices 14 Process Zone 16 Processing nozzle 18 workpieces 20 Workpiece support 22 Machining direction 24 Cutting edge 26 Processing Front 28 Image Sensor 30 Optical Imaging System 32 System Axis 34 First Opening 36 Second Opening 38 First imaging angle 40 First Ray 42 Second imaging angle 44 Second Ray 46 Horizontal line 48 Process Zone Opening 50 directional lens 52 First imaging lens 54 First imaging area 56 Second imaging area 58 First Length 60 Second Length 62 Opening disc 64 Arrow 66 First Rotational Decoupling 68 Imaging Intersections 70 Optical Wedge 72 First Optical Subsystem 74 First deflection mirror 76 Second deflection mirror 78 Second imaging lens 80 Imaging Prism 82 Third Opening 84 The Third Ray 86 Third Imaging Angle 88 Third Imaging Area 90 Second Optical Subsystem 92 Third deflection mirror 94 Fourth deflection mirror 96 Third imaging lens 98 Second imaging prism 100 Second Rotational Decoupling 102 Optical bandpass filter 104 Third Length 106 orbit 108 Method 110 Method steps 112 Method steps 114 Method steps

Claims

1. 1. An imaging device (12) for imaging a process zone (14) of a laser machining tool (10), the imaging device comprising: an image sensor (28) and an optical imaging system (30) located between the process zone (14) and the image sensor (28), the optical imaging system (30) comprising: a system axis (32) extending between said image sensor (28) and said process zone (14); a first aperture (34) radially spaced from the system axis (32), the first aperture (34) defining a first light ray (40) emitted from the process zone (14) at a first imaging angle (38); a second aperture (36) that defines a second light beam (44) emitted from said process zone (14) at a second imaging angle (42); a first imaging lens (52) arranged between said opening (34, 36, 82) and said image sensor (28), said first imaging lens (52) being designed to image a light beam (40, 44, 84) onto said image sensor (28); 1. An imaging device (12), wherein the first imaging angle (38) is different from the second imaging angle (42), and the optical imaging system (30) is designed to image the first light beam (40) spatially separated from the second light beam (44).

2. 2. The imaging device (12) of claim 1, wherein the optical imaging system (30) further comprises a directional lens (50) disposed between the process zone (14) and the opening (34, 36, 82), and the directional lens (50) directs the light rays (40, 44, 84) emitted by the process zone (14) parallel to the system axis (32) onto the opening (34, 36, 82).

3. 3. The imaging device (12) of claim 1 or 2, wherein the optical imaging system (30) has a third opening (82), and the third opening (82) defines a third light ray (84) emitted from the process zone (14) at a third imaging angle (86).

4. The imaging device (12) of claim 3, wherein the third imaging angle (86) is different from the first and / or second imaging angle (38, 42).

5. 5. The imaging device (12) of claim 3 or 4, wherein the optical imaging system (30) is designed to image the third light beam (84) onto the image sensor (28) spatially separated from the first and / or second light beam (40, 44).

6. 6. The imaging device (12) according to claim 1, wherein the optical imaging system (30) has a process zone opening (48), in particular a processing nozzle (16) of the laser machining tool (10), for defining the extent of the light beam (40, 44, 84) emitted by the process zone (14).

7. The imaging device (12) according to any one of claims 1 to 6, wherein the apertures (34, 36, 82) are designed on a common aperture disk (62).

8. 8. The imaging device (12) according to claim 7, wherein the aperture disc (62) is designed to be rotatable about the system axis (32).

9. 9. The imaging device (12) of claim 8, wherein the optical imaging system (30) has a first optical rotational decoupling (66) downstream of the first aperture (34), the first optical rotational decoupling (66) being designed independently of a rotation of the aperture disk (62) to positionally correctly image the first light beam (40) onto the image sensor (28).

10. 10. The imaging device (12) of claim 9, wherein the system axis (32) intersects the image sensor (28) at an imaging intersection (68), and the first imaging lens (52) is designed for imaging centered on the first light ray (40) on the imaging intersection (68).

11. 11. The imaging device (12) of claim 8, wherein the system axis (32) extends through the center of the second opening (36) and comprises an optical wedge (70) positioned in front of the first imaging lens (52), the optical wedge (70) designed to deflect the second light ray (44) onto the first imaging lens (52) at an angle relative to the system axis (32).

12. 11. The imaging device (12) of claim 8, wherein the system axis (32) extends through the center of the second opening (36), and the optical imaging system (30) comprises a first optical subsystem (72) having a second imaging lens (78), the second imaging lens (78) being designed to positionally correctly image the second light ray (44).

13. 13. The imaging device (12) of claim 12, wherein the first optical subsystem (72) has a first deflection mirror (74) downstream of the opening (34, 36, 82), the first deflection mirror (74) designed to deflect a specific wavelength of the second light beam (44).

14. The imaging device (12) of any one of claims 8 to 13, in conjunction with any one of claims 2 to 4, wherein the optical imaging system (30) has a second optical subsystem (90) downstream of the third opening (82) and a third imaging lens (96), the third imaging lens (96) being designed to positionally correctly image the third light ray (84).

15. 15. The imaging device (12) of claim 14, wherein the second optical subsystem (90) is designed as a second optical rotational decoupling (100), and the second optical rotational decoupling (100) is designed to positionally correctly image the third light beam (84) regardless of a rotation of the aperture disk (62).

16. 16. The imaging device (12) of claim 15, wherein the second optical rotation decoupling (100) comprises a third deflection mirror (92) downstream of the opening (34, 36, 82), the third deflection mirror (92) being designed to deflect a specific wavelength of the third light beam (84).

17. 17. The imaging device (12) of claim 1, having a single image sensor (28), wherein the optical imaging system (30) is designed to image the light beam (40, 44, 84) onto the single image sensor (28).

18. A laser machining tool (10) comprising an imaging device (12) according to any one of the preceding claims.

19. A method (108) for determining a process variable, in particular a geometrical variable, of a process zone (14) by means of an imaging device (12) according to any one of claims 1 to 17, comprising: - creating (110) a first image and a second image of said process zone (14); - providing (112) said first imaging angle (38) and said second imaging angle (42); - geometrically comparing said first image with said second image, The method (108) wherein at least one process variable is determined by geometric comparison.

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