Imaging device, laser machine tool comprising an imaging device, and method for determining process variables

Abstract

The invention relates to an imaging device (12) for imaging a process zone (14) of a laser machine tool (10), said 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); a first aperture (34) spaced radially from the system axis (32); and a second aperture (36). Light beams (40, 44) emitted from the process zone (14) at different imaging angles (38, 42) are delimited by the apertures (34, 36). The optical imaging system (30) is designed to image the first light beams (40) spatially separately from the second light beams (44). The invention also relates to: a laser machine tool (10) comprising such an imaging device (12); and a method for determining process variables using such an imaging device (12).

Description

[0001] Imaging device, laser processing machine with a

[0002] Imaging device and method for determining process variables

[0003] Background of the invention

[0004] The invention relates to an imaging device with an optical imaging system for imaging a process zone of a laser processing machine on an image sensor. The invention further relates to a laser processing machine with an imaging device and a method for determining process variables.

[0005] Such devices and methods are known in various embodiments from the prior art and are used to monitor the laser processing process. Typically, the imaging devices represent a three-dimensional representation of the process zone as a two-dimensional image on an image sensor. From the analysis of the image of the process zone, with sufficiently accurate imaging, important functional and control variables for common laser cutting machines can be derived. These variables can, for example, support feed control or miscut detection during laser processing.

[0006] WO 2016 062636 A1 describes a device for measuring the depth of a weld seam during welding or joining a workpiece using radiation. The device can be tilted relative to a processing beam depending on the feed rate in order to take a feed rate-dependent inclination of the weld seam into account for measurement purposes. However, displaying the weld seam from only one angle, even if it is adjustable, can only convey insufficient information about the process zone. For example, information can be lost due to a reduced imaging area.

[0007] WO 2016 181359 A1 describes a laser processing device with at least one group of detector arrays. The detector array is arranged in a ring around an optical axis of the laser cutting device. The detector array is designed to detect the process zone at a variety of static angles. The described detector array places considerable design demands on the implementation of the described principle and requires a complex evaluation routine to evaluate the detected information.

[0008] DE 10 2013 218421 A1 describes a device for monitoring a laser cutting process on a workpiece with an image capture device, wherein an observation beam is formed at an angle inclined to the laser beam. The device can also have multiple observation directions with the same angle.

[0009] The aforementioned device does indeed have the ability to image the process zone from different directions, for example, by rotating the device. However, the device only images the process zone at a single, predetermined angle. This can result in inaccurate imaging of the process zone. For example, crucial information may not be imageable by the device at only a predetermined angle. The "geometric visibility" of the process zone typically depends on the nozzle diameter of the laser processing machine, the material thickness of the workpiece to be processed, the distance between the nozzle and the workpiece, and the emission properties of the laser processing process. Object of the invention

[0010] It is an object of the invention to provide a device and an associated method for imaging a process zone of a laser processing device, which enable a reliable determination of process variables from the image.

[0011] Description of the invention

[0012] This object is achieved according to the invention by an imaging device having the features of patent claim 1. The object is also achieved by a laser processing machine having the features of patent claim 18 and a method having the features of patent claim 19. The subclaims represent preferred embodiments of the invention.

[0013] According to the invention, an imaging device is provided. The imaging device is suitable for imaging a process zone of a laser processing machine. Typically, the imaging of the process zone occurs optically by imaging light emitted from the process zone.

[0014] The imaging device comprises an image sensor. The image sensor is typically designed for two-dimensional imaging of light radiation, preferably in the spectral range from ultraviolet light (UV) to short-wave infrared light (SWIR), particularly preferably from 350 nm to 1800 nm. The image sensor is preferably semiconductor-based.

[0015] The imaging device further comprises an optical imaging system arranged between the process zone and the image sensor. The optical imaging system is preferably designed to guide and direct the light radiation emitted by the process zone to the image sensor. Further preferably, the optical imaging system is designed to deflect a processing beam of the laser processing device onto a workpiece to be processed. The optical imaging system has a system axis running between the image sensor and the process zone. The system axis can be understood as an idealized axis—for the sake of simplified explanation of the invention. The idealized axis can replace an optical path commonly used in practice, which can consist of partial paths each formed at an incline to one another.The person skilled in the art is able to transfer the invention starting from the system axis to an optical path in order, for example, to constructively enable an offset between the process zone and the image sensor.

[0016] The optical imaging system also has a first aperture radially spaced from the system axis. The first aperture is preferably formed perpendicular to the system axis. The first aperture limits first light rays emitted from the process zone at a first imaging angle. In other words, the first aperture only allows light radiation emitted from the process zone at a specific angle to pass through.

[0017] The optical imaging system further comprises a second aperture. The second aperture is preferably configured perpendicular to the system axis. The second aperture can be spaced apart from the first aperture, particularly radially relative to the system axis. The second aperture limits second light beams emitted from the process zone at a second imaging angle.

[0018] The optical imaging system further comprises a first imaging lens arranged between the apertures and the image sensor. In other words, the first imaging lens is arranged in front of the first imaging lens in a beam path of the optical imaging system. As a result, the optical imaging system is designed to integrate additional optical components between the apertures and the first imaging lens. Additional optical components can 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 methods, such as stereometry / stereoscopy, ratio pyrometry, goniometry, or spectral analysis.

[0019] The first imaging lens is typically designed as a converging lens. The first imaging lens is configured to image at least the first and second light beams onto the image sensor.

[0020] According to the invention, the first imaging angle is different from the second imaging angle. In other words, the first light beams limited by the first aperture have a different imaging angle than the second light beams limited by the second aperture. An imaging angle is understood to be an angle enclosed between the respective light beam and the system axis. In other words, multiple light beams can have the same angular magnitude but be emitted from the process zone in different directions. The imaging angle can be zero degrees.

[0021] The optical imaging system is further configured to spatially separate the first light beams from the second light beams. The first light beams and the second light beams are typically imaged on the image sensor.

[0022] In other words, the underlying problem is solved in that the imaging device is designed to simultaneously image the process zone under at least two different imaging angles, while the remaining light radiation emitted by the process zone is blocked out, 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, the simultaneous imaging of the two light beams occurs spatially separated on the image sensor, thus enabling 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 a geometric comparison. In other words, the process zone can be analyzed three-dimensionally.A three-dimensional analysis can reliably determine process parameters such as the length of the laser processing machine's processing front, a spatially resolved temperature measurement, and / or temperature distribution within the process zone. This can be used, for example, to detect the formation of plasma or metal vapor and improve the quality of laser processing by avoiding faulty cuts.

[0023] In a preferred embodiment of the imaging device, the optical imaging system comprises a directional lens arranged between the process zone and the apertures. The directional lens can align light rays emitted from the process zone onto the apertures parallel to the system axis. In other words, the imaging device can form a collimator. This allows the light rays to be limited particularly precisely by the apertures.

[0024] An embodiment of the imaging device is also preferred in which the optical imaging device has a third aperture. The third aperture can limit third light beams emitted from the process zone at a third imaging angle. An additional aperture can further improve the three-dimensional observation of the process zone.

[0025] In a preferred embodiment of the imaging device, the third imaging angle is different from the first and / or second imaging angle. This allows for an even more precise determination of the process variables.

[0026] A particularly preferred development of the imaging device is one in which the optical imaging system is designed to image the third light beams spatially separately from the first and / or second light beams on the image sensor. Preferably, all light beams are spatially separated from one another on the image sensor. This allows the images to be evaluated with a clear assignment to the respective imaging angles. In a preferred embodiment of the imaging device, the optical imaging system has a process zone aperture. The process zone aperture can in particular be designed as a processing nozzle of the laser processing machine. This makes it possible to limit the total number of light beams emitted from the process zone in the direction of the imaging device, thereby increasing the imaging accuracy of the light beams.

[0027] In a preferred embodiment of the imaging device, the diaphragms are formed on a common diaphragm disk. The common diaphragm disk is preferably arranged perpendicular or orthogonal to the system axis. A common diaphragm disk enables particularly precise spacing of the diaphragms from one another, particularly during movement of the diaphragms. The diaphragm disk can preferably be formed as a coated glass substrate. Particularly preferably, the diaphragm disk transmits light radiation in the region of the diaphragms and attenuates, absorbs, or reflects the light radiation outside the diaphragms.

[0028] In a preferred embodiment of the imaging device, the aperture disk is designed to be rotatable about the system axis. The aperture disk is preferably designed to be rotatable depending on the processing direction of the laser processing machine. This allows the images of the light beams to be maintained relative to a processing zone configuration dependent on the processing direction. For example, a so-called piercing image of the process zone can be further imaged piercingly when the laser processing direction changes by, for example, 90 degrees, if the aperture disk is also rotated by 90 degrees.

[0029] In a preferred development of the imaging device, the optical imaging system has a first optical rotary decoupling device downstream of the first diaphragm. The first optical rotary decoupling device is typically designed to be independent of a rotation of the diaphragm disk for the positionally accurate imaging of the first light beams on the image sensor. In other words, the first light beams can be imaged on the same imaging area of ​​the image sensor regardless of the processing direction of the laser processing machine. This makes it particularly easy to assign the imaging angle to the image. Furthermore, the dimensions of the image sensor can be kept particularly compact.

[0030] A particularly preferred embodiment of the imaging device is one in which the system axis intersects the image sensor at an image intersection point. In this case, the first imaging lens is preferably designed to centrally image the first light rays onto the image intersection point. By imaging the first light rays at the image intersection point, a stationary image of the first light rays can be achieved.

[0031] In a particularly preferred development of the imaging device, in which the system axis runs centrally through the second diaphragm, the imaging device has at least one optical wedge arranged upstream of the first imaging lens and downstream of the second diaphragm. In other words, in this case the second diaphragm limits the second light beams which run coaxially with the system axis and are optically independent of any rotation of the second diaphragm. The optical wedge is preferably designed to deflect the second light beams onto the first imaging lens at an angle to the system axis. By deflecting the second light beams, a position of the image on the image sensor can be determined. The second light beams are preferably imaged onto an imaging region on the image sensor which is decentered or spaced from the image intersection point.This allows for position-accurate and rotation-independent imaging of the second light beams without rotational decoupling.

[0032] Alternatively, in a further development of the imaging device with a system axis running centrally through the second aperture, it can be provided that the optical imaging system has a first secondary optical system with a second imaging lens. The first secondary optical system, or the second imaging lens, is preferably designed for positionally accurate imaging of the second light beams on the image sensor. A second imaging lens can prevent optical superposition of the light beams in the first imaging lens, thus increasing imaging accuracy. By forming a secondary optical system, an optical path with different spectral transmission properties that is separate from the optical path of the first light beams can be provided. This allows the process zone to be imaged with different spectral properties, which can further improve the analysis of the process zone.

[0033] A particularly preferred embodiment of the imaging device is one in which the first secondary optical system has a first deflecting mirror arranged downstream of the apertures, wherein the first deflecting mirror is designed to deflect second light beams. Preferably, the first deflecting mirror is designed to deflect specific wavelengths of the second light beams.

[0034] In particular, unwanted wavelengths can be filtered out. This allows the imaging of the second light beams to be particularly precise.

[0035] In a preferred development of the imaging device in conjunction with a third aperture, the optical imaging system can be provided with a second secondary optical system downstream of the third aperture. The second secondary optical system is preferably designed to accurately image the third light beams, particularly on the image sensor, independently of any rotation of the aperture disk.

[0036] A particularly preferred development of the imaging device is one in which the second secondary optical system has a second deflecting mirror arranged downstream of the apertures. The second deflecting mirror is preferably designed to deflect specific wavelengths of the third light beams. This allows the third light beams to be imaged in a predetermined spectral range. In a preferred embodiment of the imaging device, the optical imaging system is designed to image the light beams on a single image sensor.

[0037] The underlying problem is also solved by a laser processing machine with an imaging device as described above and below.

[0038] The laser processing machine typically has a laser processing unit for generating a laser beam. Furthermore, the laser processing machine typically has a machine control system. The machine control system can be configured to control or regulate the laser processing unit and / or the imaging device.

[0039] The machine control system preferably has an evaluation unit. The evaluation unit is particularly preferably configured to evaluate the images on the image sensor.

[0040] Furthermore, the underlying problem is solved by a method for determining process variables of the process zone using the imaging device described above and below. The method comprises the following method steps.

[0041] In one method step, at least one first image and at least one second image of the process zone are created. The images are typically generated by the first and second light beams on the image sensor.

[0042] Preferably, a third image can be generated by the third light rays.

[0043] In a further method step, at least the first imaging angle and the second imaging angle are provided. The imaging angles can be provided, for example, by the machine control system and / or by an operator of the imaging device.

[0044] In a subsequent method step, at least the first image is compared with the second image. Preferably, the geometric contents of the images are compared with each other.

[0045] Based on the comparison, at least one process variable is determined or calculated.

[0046] Further features and advantages of the invention will become apparent from the description, the claims, and the drawings. According to the invention, the above-mentioned and further-described features can be used individually or in combination in any convenient way. The embodiments shown and described are not intended to be exhaustive, but rather are exemplary in nature for describing the invention. They show:

[0047] Fig. 1 shows a laser processing machine with a first embodiment of an imaging device according to the invention in a schematic representation, wherein the imaging device has an image sensor and an optical imaging system;

[0048] Fig. 2 shows a second embodiment of the imaging device in a schematic representation;

[0049] Fig. 3 shows a third embodiment of the imaging device in a schematic representation;

[0050] Fig. 4 shows the image sensor from Fig. 3 in a schematic representation;

[0051] Fig. 5 shows the aperture plate from Fig. 3 in a schematic view; Fig. 6 shows a method according to the invention in a schematic representation.

[0052] Fig. 1 shows a laser processing machine 10 with an imaging device 12 for imaging a process zone 14 of the laser processing machine 10. In the case shown, the process zone 14 is designed as a processing area or irradiation area of ​​a laser beam, not shown in detail, of the laser processing machine 12.

[0053] During a machining process, the laser beam exits through a machining nozzle 16 of the laser machining machine 10 toward a workpiece 18 to be machined. For improved machining, the workpiece 18 can rest on a preferably web-like workpiece support 20, as shown in the case. By irradiating the workpiece 18, it can be melted and / or at least partially vaporized in the effective range of the laser beam. If the laser machining machine 10 is moved in a machining direction 22, the workpiece 18 to be machined can be cut, for example, along a cutting edge 24. In the transition region between the workpiece 18 and the cutting edge 24, a machining front 26 forms on the workpiece 18 depending on the irradiation duration by the laser beam. Important information about the machining process can be derived from the formation of the machining front 26.The design of the processing front 26 is therefore crucial for controlling or regulating the laser processing machine 10 and must be monitored, for example, to ensure a high processing speed and / or processing quality.

[0054] According to the embodiment shown, the imaging device 12 is arranged on the laser processing machine 10, preferably integrated into the laser processing machine 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 formed along a system axis 32 that runs between the image sensor 28 and the process zone 14. The system axis 32 is preferably formed as the optical axis of the optical imaging system 30. In other words, the optical imaging system 30 can be formed at least predominantly rotationally symmetrical to the system axis 32. The system axis 32 is further preferably formed orthogonal to the workpiece 18 to be machined. The optical imaging system 30, in particular the entire imaging device 12, can be arranged orthogonal to the workpiece 18 to be machined.

[0055] The optical imaging system 30 has a first aperture 34 spaced radially from the system axis 32. The optical imaging system 30 also has a second aperture 36. The second aperture 36 is arranged at a distance from the first aperture 34, in particular radially. According to the embodiment shown, the second aperture 36 can be arranged centrally to the system axis 32.

[0056] The first aperture 34 limits first light rays 40 emitted from the process zone 14 at a first imaging angle 38. The second aperture 36 limits second light rays 44 emitted from the process zone 14 at a second imaging angle 42. The imaging angles 38, 42 can be determined as the inclination of the respective light rays 40, 44 relative to the system axis 32. According to the illustrated embodiment, the second light rays 44 are emitted parallel to the system axis 32, which is why the second imaging angle 42 here is zero degrees in absolute value. The first imaging angle 38 is designed to be different in absolute value from the second imaging angle 42. The first imaging angle preferably has a magnitude between three degrees and four degrees.

[0057] The first light beams 40 and the second light beams 44 are imaged spatially separately on the image sensor 28 by the optical imaging system 30. This enables a perspective view of the process zone 14. For the sake of a more compact representation, the beam paths of the first light beams 40 and the second light beams 44 are shown interrupted by two horizontal lines 46.

[0058] According to the embodiment shown, the optical imaging system 30 can have a process zone aperture 48—here formed on the processing nozzle 16. The process zone aperture 48 limits the light beams emitted by the process zone 14, for example, the first and second light beams 40, 44. This can reduce scattered radiation and improve the imaging of the first and second light beams 40, 44.

[0059] The optical imaging system 30 can include a directional lens 50. The directional lens 50 can be arranged between the process zone 14, in particular between the process zone aperture 48, and the first and / or second aperture 34, 36. The directional lens 50 preferably aligns the first and / or second light beams 40, 44 emitted by the process zone 14 parallel to the system axis 32. This allows the imaging device 12 to be kept compact in its dimensions radially relative to the system axis 32.

[0060] The optical imaging system 30 has a first imaging lens 52. The first imaging lens 52 is arranged between the apertures 34, 36 and the image sensor 28. The first imaging lens 52 is typically configured to image the first light rays 40 and / or the second light rays 44 on the image sensor 28. As shown in Fig. 1, the imaging lens 52 images the first light rays 40 in a first imaging region 54 and the second light rays 44 in a second imaging region 56 on the image sensor 28. The first imaging region 54 is spatially separated from the second imaging region 56.

[0061] According to the embodiment, a single image sensor 28 is provided. Alternatively or additionally, the imaging device 12 can have multiple image sensors 28 for imaging the light beams 40, 44. The image sensor 28 and the imaging regions 54, 56 with the first and second light beams 40, 44 imaged on the image sensor 28 are shown in a detailed view as a top view for better explanation.

[0062] According to Fig. 1, the first light beams 40 are inclined in the processing direction 22, thereby producing a "piercing image" of the process zone 14. In other words, a "piercing image" enables an inclined 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, which depends on the first imaging angle 38, can be determined.

[0063] The second light beams 44 are not inclined relative to the system axis 32, resulting in a "central image" of the process zone 14. In other words, a "central image" enables 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, which depends on the second imaging angle 42.

[0064] In a geometric comparison of the determined lengths 58, 60 of the processing front 26, further geometric variables of the process zone 14, for example an instantaneous penetration depth of the laser beam, can then be determined.

[0065] The optical imaging system 30 can include a diaphragm disk 62. For better explanation, the diaphragm disk 62 is shown in a further detailed view as a top view. The first diaphragm 34 and the second diaphragm 36 can be formed on the (common) diaphragm disk 62. This promotes precise positioning of the first diaphragm 34 relative to the second diaphragm 36, which has a beneficial effect on the imaging accuracy of the process zone 14.

[0066] The aperture disk 62 can be designed to be rotatable about the system axis 32, as indicated by the arrow 64. This allows the imaging device 12 to be adapted to a changed processing direction 22 of the laser processing machine 10. For example, if the processing direction 22 shown in Fig. 1 is reversed, the optical imaging system 30 images the process zone 14 opposite to the processing direction 22. This can be prevented by rotating the aperture disk 62 by 180 degrees.

[0067] The optical imaging system 30 can, as shown, have a first rotational decoupling 66. The first rotational decoupling 66 is arranged downstream of the first diaphragm 34. According to the embodiment shown, the first rotational decoupling 66 is designed as a converging lens, here in the form of the imaging lens 52, which is rotationally symmetrical 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 rays 40 delimited by the first diaphragm 34 in the imaging region 54 of the image sensor 28. The imaging region 54 is arranged centrally with respect to an imaging intersection point 68 of the system axis 32 with the image sensor 28, so that the imaging of the first light rays 40 can be carried out with precise positioning, independent of any displacement or rotation of the first diaphragm 34 about the system axis 32 relative to the system axis 32.In other words, the first light rays 40 can be imaged in the stationary imaging area 54 regardless of a rotation of the first aperture 34. The position of the image on the image sensor 28 therefore does not change.

[0068] According to the embodiment shown in Fig. 1, the optical imaging system 30 has an optical wedge 70 for spatially spaced-apart imaging of the second light rays 44 on the image sensor 28. The optical wedge 70 is configured to direct the second light rays 44 onto the imaging lens 52 at an incline relative to the system axis 32. Inclined illumination of the imaging lens 52 results in the second light rays 44 being imaged on the image sensor 28 at a radial distance from the imaging intersection point 70. Due to the central arrangement of the second diaphragm 36 on the system axis 32, positionally accurate imaging of the second light rays 44 can occur in the imaging region 56 of the image sensor 28, regardless of any rotation of the second diaphragm 36 about the system axis 32. Rotational decoupling can be omitted in this embodiment.

[0069] Fig. 2 shows a schematic representation of a second embodiment of an imaging device 12. An optical imaging system 30 has a first rotational decoupling element 66, which, by means of a first imaging lens 52, enables rotation-independent and positionally accurate imaging of first light rays 40 in the imaging area 54 on an image sensor 28.

[0070] In addition, the optical imaging system 30 has a first secondary optical system 72. The secondary optical system 72 is designed to image the second light beams 44 onto the image sensor 28 at a spatially separate location from the first light beams 40. According to the embodiment shown, the first secondary optical system 72 has a first deflecting mirror 74, a second deflecting mirror 76, a second imaging lens 78, and an imaging prism 80.

[0071] The first deflecting mirror 74 is arranged between the apertures 34, 36 and the first imaging lens 52 and is configured to deflect second light beams 44. As shown, the second light beams 44 can be directed by the first deflecting mirror 74 past the first imaging lens 52 to a second deflecting mirror 76.

[0072] The second deflecting mirror 76 can be configured to align the second light beams 44. Preferably, the second deflecting mirror 76 aligns the second light beams 44 parallel to the system axis 32. In other words, the deflecting mirrors 74, 76 cause a parallel shift of the second light beams 44 or a radial spacing of the second light beams 44 from the system axis 32. The second light beams 44 can then be imaged onto the image sensor 28 by means of the second imaging lens 78, thereby improving the image quality.

[0073] In order to keep the dimensions of the image sensor 28 small, it can be provided, as shown, that the radial spacing caused by the deflecting mirrors 74, 76 is partially or completely compensated by the imaging prism 80.

[0074] Fig. 3 shows a third embodiment of an imaging device 12 in a schematic representation.

[0075] An optical imaging system 30 has a first aperture 34, a second aperture 36, and a third aperture 82 radially spaced from the system axis 32. The apertures 34, 36, 82 can be formed on a common aperture disk 62.

[0076] First light rays 40, limited by the first aperture 34, are imaged onto an image sensor 28 by means of an imaging lens 52 in a first imaging region 54. Second light rays 44 are imaged onto the image sensor 28 in a second imaging region 56, analogous to Fig. 2, by means of a first secondary optical system 72 or a second imaging lens 78.

[0077] The third aperture 82 can be arranged at a distance from the first aperture 34 and / or the second aperture 36, in particular radially. The third aperture 36 is typically designed to limit third light beams 84 that are emitted from the process zone 14 at a third imaging angle 86. The third imaging angle 86 can be inclined counter to the processing direction 22. The optical imaging system 30 is designed to image the third light beams 84 on the image sensor 28, in particular in a third imaging region 88. As shown, the optical imaging system 30 can have a second auxiliary optical system 90 that is configured to image the third light beams 84 on the image sensor 28. The second auxiliary optical system 90 can have a third deflecting mirror 92, a fourth deflecting mirror 94, a third imaging lens 96, and a second imaging prism 98.

[0078] The second secondary optical system 90 can be configured analogously to the first secondary optical system 72 for radially spacing the third light beams 84. For this purpose, the first light beams 84 can first be deflected from a direction parallel to the system axis 32, followed by a subsequent parallel alignment of the deflected third light beams 84 with respect to the system axis 32. The third light beams 84 can thus be imaged in a positionally accurate manner via the third imaging lens 96 and the imaging prism 98 in the, in particular, stationary, third imaging region 88.

[0079] According to the embodiment shown in Fig. 3, the second secondary optical system 90 is also designed as a second rotational decoupling device 100. This enables the positionally accurate imaging of the third light beams 84 even when the third diaphragm 82 or the diaphragm disk 62 is rotated.

[0080] The third deflecting mirror 92 of the second secondary optical system 90 can be configured to be rotationally symmetrical to the system axis 32 in a plane orthogonal to the system axis 32. The third deflecting mirror 92 can be configured to be annular in the plane orthogonal to the system axis 32, wherein the inner diameter is smaller than a smallest distance of the third aperture 82 from the system axis 32 and wherein the outer diameter is greater than a greatest distance of the third aperture 82 from the system axis 32. Preferably, the deflecting mirror 92 is configured as a circumferential circular ring in the plane orthogonal to the system axis 32. In other words, the deflecting mirror 92 has dimensions in the plane projected to the system axis 32 that correspond at least to the circumferential projection surface of the third aperture 82. This makes it possible to achieve the greatest possible independence from the rotation of the third aperture 82.A circular ring-like design of the third deflecting mirror 92 enables the optically unhindered passage of the first light beams 40 and the second light beams 44 if the apertures 34, 36, 82 each have circumferential projection surfaces that are radially spaced from one another - in other words, if the circumferential projection surfaces of the apertures 34, 36, 82 do not overlap.

[0081] Alternatively, as shown in Fig. 3, the deflecting mirror 92 can be configured to deflect light beams within a predetermined wavelength range, with light beams outside the predetermined wavelength range being transmitted. For this purpose, at least one optical bandpass filter 102 can be arranged upstream of the deflecting mirror 92. Preferably, the apertures 34, 36, 82 each have an optical bandpass filter 102 that predetermines the wavelength range of the respective light beams 40, 44, 84. This allows light beams 40, 44, 84 that have overlapping circumferential projection surfaces to be optically separated.

[0082] Likewise, further information can be acquired based on polarization properties. For this purpose, at least one of the apertures 34, 36, 82 can be provided with a polarization filter, for example, for filtering s- and p-polarized light beams, as an alternative or in addition to the optical bandpass filter 102. Using a polarization filter, correspondingly "polarized" images can be displayed and / or used for measurement purposes.

[0083] Fig. 4 shows the image sensor 28 from Fig. 3 in a schematic view. Imaging regions 54, 56, 88 are spatially spaced from one another and arranged in a fixed position on the image sensor 28. In other words, the positions of the imaging regions 54, 56, 88 on the image sensor 28 do not change when the machining direction 22 (see Fig. 1) or the rotational position of the aperture disk 62 (see Figs. 1-3, 5) is changed.

[0084] The first imaging area 54 shows a “piercing image” of the process zone

[0085] 14 (see Fig. 1 ), whereby, for example, the first length 58 of the processing front 26, which is dependent on the first imaging angle 38 (see Fig. 1 ), can be determined. Furthermore, the second imaging region 56 shows a "central image" of the process zone 14, whereby, for example, a second length 60 of the processing front 26, which is dependent on the second imaging angle 42 (see Fig. 1 ), can be determined. In addition, the third imaging region 88 shows a "slow representation" of the process zone 14 (see Fig. 3) counter to the processing direction 22 (see Fig. 3), caused by the third imaging angle 86, whereby, for example, a third length 104 of the processing front 26 can be determined.

[0086] The additional information about the third image can further improve the determination of geometric dimensions of process zone 14.

[0087] Fig. 5 shows the aperture disk 62 from Fig. 3 in a schematic view.

[0088] The aperture disk 62 is designed to be rotatable about the system axis 32, as indicated by arrow 64. The apertures 34, 36, 82 are spatially separated from one another on the aperture disk 62. The second aperture 36 is designed to be centered on the system axis 32 on the aperture disk 62.

[0089] 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.

[0090] A track 106 of the first aperture 34, indicated by a dashed circular ring, overlaps with the third aperture 82. This can lead to optical overlaps between the first and third light beams 40, 84, which makes the images on the image sensor 28 (Figures 1-4) unclear. To avoid optical overlap, the apertures 34, 36, 82, here in particular the first and third apertures 34, 82, can have an optical bandpass filter 102. Fig. 6 schematically shows a method 108 for determining, in particular geometric, process variables of a process zone 14 (see Fig. 1) by means of an imaging device 12 (see Fig. 1).

[0091] The method 108 comprises the following method steps (see also Fig. 1 below).

[0092] In a method step 110, a first image and a second image of the process zone 14 are created. The first and second images are typically created by imaging first and second light beams 40, 44 in a first and second imaging region 54, 56 of an image sensor 28.

[0093] In a further method step 112, the first imaging angle 38 and a second imaging angle 42 are provided.

[0094] A subsequent method step 114 provides for the geometric comparison of the first image with the second image, wherein at least one process variable is determined or calculated by the geometric comparison.

[0095] Taking all the figures of the drawing together, the invention relates to an imaging device (12) for imaging a process zone (14) of a laser processing machine (10), comprising 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) has a system axis (32) extending between the image sensor (28) and the process zone (14), a first diaphragm (34) radially spaced from the system axis (32), and a second diaphragm (36). Light beams (40, 44) emitted by the process zone (14) at different imaging angles (38, 42) are delimited by the diaphragms (34, 36). The optical imaging system (30) is designed to spatially separate the first light beams (40) from the second light beams (44).The invention further relates to a laser processing machine (10) with an imaging device (12) and a method for determining process variables. List of reference symbols.

[0096] Laser processing machine imaging device process zone

[0097] Processing nozzle workpiece

[0098] Workpiece support Machining direction Cutting edge

[0099] Processing front

[0100] Image sensor optical imaging system system axis first aperture second aperture first imaging angle first light rays second imaging angle second light rays horizontal lines

[0101] Process zone aperture

[0102] Directional lens first imaging lens first imaging area second imaging area first length second length

[0103] aperture disc

[0104] Arrow first rotational decoupling image intersection optical wedge first optical subsystem first deflection mirror second deflection mirror second imaging lens imaging prism third aperture third light rays third imaging angle third imaging area second optical subsystem third deflection mirror fourth deflection mirror third imaging lens second imaging prism second rotational decoupling optical bandpass filter third length

[0105] track

[0106] Proceedings

[0107] Process step

[0108] Process step

[0109] Process step

Claims

Imaging device (12) for imaging a process zone (14) of a laser processing machine (10), comprising an image sensor (28) and an optical imaging system (30) arranged between the process zone (14) and the image sensor (28); wherein the optical imaging system (30) comprises: - 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 limiting first light beams (40) emitted by the process zone (14) at a first imaging angle (38); - a second aperture (36) which limits second light beams (44) emitted from the process zone (14) at a second imaging angle (42); - a first imaging lens (52) arranged between the apertures (34, 36, 82) and the image sensor (28), which is designed to image light rays (40, 44, 84) on the image sensor (28); wherein the first imaging angle (38) is different from the second imaging angle (42); and wherein the optical imaging system (30) is designed to spatially separate the first light rays (40) from the second light rays (44). The imaging device (12) according to claim 1, wherein the optical imaging system (30) further comprises a directional lens (50) arranged between the process zone (14) and the apertures (34, 36, 82), which aligns light rays (40, 44, 84) emitted by the process zone (14) onto the apertures (34, 36, 82) parallel to the system axis (32). Imaging device (12) according to claim 1 or 2, wherein the optical imaging system (30) has a third aperture (82) which is Process zone (14) limits third light beams (84) emitted at a third imaging angle (86). Imaging device (12) according to claim 3, wherein the third imaging angle (86) is different from the first and / or the second imaging angle (38, 42). Imaging device (12) according to claim 3 or 4, wherein the optical imaging system (30) is designed for spatially separate imaging of the third light beams (84) from the first and / or the second light beams (40, 44) on the image sensor (28). Imaging device (12) according to one of the preceding claims, wherein the optical imaging system (30) has a process zone aperture (48), in particular a processing nozzle (16) of the laser processing machine (10), for limiting the light beams (40, 44, 84) emitted from the process zone (14). Imaging device (12) according to one of the preceding claims, wherein the diaphragms (34, 36, 82) are formed on a common diaphragm disk (62).The imaging device (12) according to claim 7, wherein the aperture disk (62) is rotatable about the system axis (32). The imaging device (12) according to claim 8, wherein the optical imaging system (30) has a first optical rotary decoupling device (66) downstream of the first aperture (34); wherein the first optical rotary decoupling device (66) is independent of a rotation of the aperture disk (62). for positionally accurate imaging of the first light rays (40) on the image sensor (28). Imaging device (12) according to claim 9, wherein the system axis (32) intersects the image sensor (28) at an imaging intersection point (68); and wherein the first imaging lens (52) is designed to centrally image the first light rays (40) onto the imaging intersection point (68). Imaging device (12) according to one of claims 8 to 10, wherein the system axis (32) runs centrally through the second diaphragm (36); comprising an optical wedge (70) arranged upstream of the first imaging lens (52), which is designed to deflect the second light rays (44) onto the first imaging lens (52) at an angle relative to the system axis (32).Imaging device (12) according to one of claims 8 to 10, wherein the system axis (32) runs centrally through the second aperture (36); wherein the optical imaging system (30) has a first secondary optical system (72) with a second imaging lens (78); and wherein the second imaging lens (78) is designed to image the second light beams (44) with accurate position. Imaging device according to claim 12, wherein the first secondary optical system (72) has a first deflecting mirror (74) arranged downstream of the apertures (34, 36, 82), the first deflecting mirror (74) being designed to deflect specific wavelengths of the second light beams (44). Imaging device (12) according to one of claims 8 to 13 in conjunction with one of claims 2 to 4, wherein the optical imaging system (30). a second secondary optical system (90) downstream of the third diaphragm (82) having a third imaging lens (96); and wherein the third imaging lens (96) is designed for positionally accurate imaging of the third light beams (84). Imaging device (12) according to claim 14, wherein the second secondary optical system (90) is designed as a second optical rotational decoupling device (100); wherein the second optical rotational decoupling device (100) is designed for positionally accurate imaging of the third light beams (84) independent of a rotation of the diaphragm disk (62). Imaging device (12) according to claim 15, wherein the second optical rotational decoupling device (100) has a third deflecting mirror (92) downstream of the diaphragms (34, 36, 82), wherein the third deflecting mirror (92) is designed for deflecting specific wavelengths of the third light beams (84).Imaging device (12) according to one of the preceding claims, comprising a single image sensor (28); wherein the optical imaging system (30) is designed to image the light beams (40, 44, 84) on the single image sensor (28). Laser processing machine (10) with an imaging device (12) according to one of the preceding claims. Method (108) for determining, in particular geometric, process variables of a process zone (14) by means of an imaging device (12) according to one of claims 1 to 17, comprising the steps: - Creating (110) a first image and a second image of the Process zone (14); - providing (112) the first imaging angle (38) and the second imaging angle (42); - Geometrically comparing the first image with the second image; wherein at least one process variable is determined by the geometric comparison.

Images