Event-based camera, laser beam processing device and application of event-based camera

Abstract

The invention relates to an event-based camera (10) for generating sensor data, in particular for a laser beam processing device, comprising a camera chip (12) and an objective lens (14) for imaging an object (20) located in a detection range (24) of the event-based camera (10) onto the camera chip (12), the event-based camera (10) comprising an illumination device (22), and wherein the lighting device (22) is designed to illuminate the camera chip (12) with light. The invention further relates to a laser beam machining device comprising an event-based camera (10) for monitoring a laser beam machining process and to the use of the event-based camera (10) for monitoring a laser beam machining process, in particular for monitoring a laser beam welding process.

Description

Technical Field

[0001] The invention relates to an event-based camera, a laser beam processing device and an application of the event-based camera. Background Art

[0002] A device for monitoring a laser machining process is known from DE 10 2019 209 376 A1, which is designed to detect spatter generated during the laser machining process by evaluating sensor data, wherein an event-based camera generates the sensor data to be evaluated during the laser machining process. Summary of the invention

[0003] Advantages of the present invention

[0004] An event-based camera according to the invention for generating sensor data, in particular for a laser beam processing device, comprises a camera chip and an objective lens for imaging an object in a detection range of the event-based camera onto the camera chip, wherein the event-based camera comprises an illumination device, and wherein the illumination device is configured to illuminate the camera chip with light. Compared to the prior art, the event-based camera according to the invention has the advantage that the recognizability of events, in particular the recognizability of splashes and splatters during laser beam processing, is improved, because the sensitivity range of the event-based camera is shifted by the illumination of the camera chip.

[0005] The invention is based on the following surprising recognition: Event-based camera recordings detail contrast changes according to Weber contrasts:

[0006]

[0007] Here IL is the base brightness before the change and IU is the brightness after the change. If a preset contrast value K is exceeded Weber , then the event-based camera triggers an event (the so-called Event). If the basic brightness of the object to be observed is too low, IL tends to 0 and thus K Weber tends to ∞. As a result, the event-based camera triggers an event (Event) even at low basic brightness when a small brightness change occurs. As a result, the event-based camera is very sensitive, so that when observing spatter during laser beam welding, objects that should not be observed, such as the processed workpiece itself, are output as sensor data. The invention described below solves this problem by shifting the sensitivity range of the event-based camera in that the basic brightness IL is increased by illuminating the camera chip. As a result, the recognizability of spatter and / or splatter during laser welding is improved in a particularly advantageous manner.

[0008] An event-based camera, also known as a neuron camera or a dynamic visual sensor, is a sensor that reacts to local brightness changes. In an event-based camera, each pixel works independently and asynchronously and generates sensor data when a brightness change occurs. The working principle of an event-based camera is similar to the working principle of a human retina. For example, an event-based camera is constructed to replace the practice of unnecessarily sending a complete image at a constant frame rate and only send local changes in cells and / or pixels of an event-based camera, where the changes are derived from, for example, movement when splashes occur. Therefore, an event-based camera is also called a dynamic visual sensor (DVS) or an event-based sensor or an event-based sensor or an event sensor or an event based sensor or a change sensor. In particular, an event-based camera is constructed to send changes in pixels and / or cells at the moment of change. This achieves a temporal resolution in the microsecond range in a particularly preferred manner. An event-based camera includes a cell matrix having cells. In particular, the cells of the cell matrix can be understood as pixels. An event-based camera is constructed to determine the intensity changes in the cells of the cell matrix as intensity data. In particular, event-based cameras are designed to detect intensity changes in a predetermined time interval t1 at which intensity changes occur. Preferably, the time interval t1 results from the moment at which the intensity change is detected by the event-based camera. Event-based cameras therefore represent a change-sensitive form of the following cameras, the operating principle of which is adapted from the biology of the human eye. Event-based cameras do not capture images in equidistant time steps like conventional image sensors, such as CMOS image cameras, but rather measure the temporal intensity differences at the individual pixel positions and immediately transmit only these temporal intensity differences with microsecond accuracy and millisecond delay. If the intensity of a pixel does not change or changes only slightly, no event is triggered and no data is transmitted for this pixel.

[0009] In summary, event-based cameras have high dynamics of >120 dB with a high temporal resolution of approximately 1 μs. In addition, event-based cameras have a low latency of <100 μs. Due to the low data rate, the requirements for bandwidth, memory and computer power for transmission, storage and post-processing are low. In addition, event-based cameras are distinguished by a compact design.

[0010] It is advantageous if the lighting device is designed to illuminate the camera chip uniformly with light, since this ensures that the entire camera chip has the same sensitivity at each pixel, so that the same event is recorded in a similar manner at each pixel position.

[0011] In addition, it is particularly advantageous to arrange the lighting device in the interior of the objective lens. This has the advantage of a compact design of the event-based camera. In addition, the lighting device is protected from environmental influences, such as splashes from the laser processing process.

[0012] Furthermore, it is advantageous if the lighting device is designed to diffusely emit light into the objective lens and / or if the event-based camera comprises a diffuser. This contributes to a uniform illumination of the camera chip and thus to a uniform sensitivity of the event-based camera. It is advantageous if the diffuser is arranged upstream of the lighting device in order to diffuse the light emitted by the light source, in particular if the diffuser is arranged upstream of a lighting device that is designed as a point light source and / or upstream of a lighting device that is designed as a ring light source.

[0013] The ring light source contributes to a small design of the event-based camera. In addition, the ring light source has the advantage that the homogeneity of the illumination is further improved.

[0014] Furthermore, an embodiment is advantageous in which the objective comprises a beam splitter and the beam splitter is arranged on the optical axis of the event-based camera, wherein the illumination device is arranged outside the objective in such a way that the illumination device illuminates the camera chip with light via the beam splitter. This embodiment has the advantage that there is design freedom when designing the illumination device, so that the illumination device can be optimized for the illumination of the camera chip. In this case, it is advantageous if a diffuser is arranged between the illumination device and the beam splitter in order to improve the homogeneity of the illumination of the camera chip.

[0015] Furthermore, an embodiment is particularly advantageous in which the lighting device is arranged outside the objective of the event-based camera in the detection range of the event-based camera in such a way that the light emitted by the lighting device substantially only illuminates the camera chip, since such an embodiment does not require changes to the objective or other structures of the event-based camera. Rather, the lighting device can be easily mounted on the objective. This is an advantageous retrofit solution. It is advantageous for the event-based camera to include a shielding device, wherein the shielding device is arranged between the lighting device and the imaged object in such a way that the object is not affected by the light emitted by the lighting device.

[0016] Furthermore, it is advantageous if the event-based camera comprises an optical filter, wherein the optical filter is arranged in the beam path of the event-based camera, in particular in the objective lens, and / or wherein the transmission wavelength of the optical filter is substantially equal to the emission wavelength of the light emitted by the illumination device. The optical filter further increases the sensitivity of the event-based camera, since, for example, ambient light is filtered out.

[0017] The invention further comprises a laser beam processing device comprising the described event-based camera for monitoring the laser processing process. Preferably, the laser beam processing device comprises an evaluation device, wherein the evaluation device is configured to detect spatters and / or splatters generated during the laser beam processing process by means of sensor data generated by the event-based camera.

[0018] The invention also includes the use of an event-based camera as described for monitoring a laser beam machining process, in particular for monitoring a laser beam welding process. As an alternative or in addition, the invention also includes the use of an event-based camera with a line laser. It is particularly advantageous to use the described camera when the image is mostly very dark, for example due to an optical filter, and when bright objects are also being observed.

[0019] The use of event-based cameras for observing spatter and splatter contributes to the quality assurance of laser beam machining processes and laser beam welding processes, since rejects can thereby be reduced to a minimum and the occurrence of defective parts can be prevented.

[0020] The described advantages of the event-based camera apply accordingly in other respects and in particular to the described laser beam processing device and the use of an event-based camera in a laser beam processing process.

[0021] Further advantages emerge from the following description of exemplary embodiments with reference to the drawings and from the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Exemplary embodiments of the invention are illustrated in the drawings with reference to a number of figures and are explained in more detail in the following description.

[0023] in:

[0024] Figure 1 An event-based camera of a first embodiment is shown;

[0025] Figure 2 An event-based camera of a second embodiment is shown;

[0026] Figure 3 An event-based camera of a third embodiment is shown;

[0027] Figure 4 A fourth embodiment of an event-based camera is shown;

[0028] Figure 5 A fifth embodiment of an event-based camera is shown; and

[0029] Figure 6 A laser beam processing apparatus is shown. DETAILED DESCRIPTION

[0030] An event-based camera for generating sensor data is described below. The event-based camera comprises a camera chip and an objective lens for imaging an object in a detection range of the event-based camera onto the camera chip, wherein the event-based camera comprises an illumination device, and wherein the illumination device is configured to illuminate the camera chip with light. Furthermore, a laser beam processing device comprising an event-based camera for monitoring a laser beam processing process and a use of the event-based camera for monitoring a laser beam processing process, in particular for monitoring a laser beam welding process, are described.

[0031] The construction of an illumination device for an event-based camera is described below. In this case, the illumination device illuminates the camera chip and does not illuminate objects in the detection range of the event-based camera. Preferably, the illumination device is integrated in the objective. Four preferred embodiments of an illumination device for illuminating the camera chip, its arrangement and integration in an event-based camera are described below. The event-based camera optionally includes an optical filter upstream of the objective.

[0032] Figure 1 The structure of an event-based camera 10 of a first exemplary embodiment is shown. The event-based camera 10 comprises a camera chip 12 and an objective 14 with one or more lenses 16. The event-based camera 10 is configured to detect an object 20 in a detection range 24 of the event-based camera 10 by imaging the object 20 onto the camera chip 12 via the objective 14. The camera chip 12 of the event-based camera 10 comprises pixels, wherein the pixels are configured to generate sensor data independently and / or temporally asynchronously with other pixels of the camera chip 12 if a brightness change detected by the or the corresponding pixel is greater than a predetermined threshold value. The pixels are arranged in particular in a matrix. In the present exemplary embodiment, the event-based camera 10 comprises an optical filter 18, which is arranged in the objective 14 on an optical axis 28 after the last lens 16 of the objective 14. Furthermore, the event-based camera 10 comprises in a first exemplary embodiment an illumination device 22 with a point light source, which is arranged in the objective 14 and emits light in a scattered and non-directional manner into the objective 14 in such a way that the camera chip 12 is illuminated, in particular substantially uniformly, in particular with a uniform illumination intensity. In the first exemplary embodiment, the illumination device 22 is arranged between two lenses 16 in the objective 14, preferably on the inner side of an objective wall of the objective 14.

[0033] Figure 2The structure of an event-based camera 10 of a second exemplary embodiment is shown. The event-based camera 10 comprises a camera chip 12 and an objective 14 with one or more lenses 16. The event-based camera 10 is configured to detect an object 20 in a detection range 24 of the event-based camera 10 by imaging the object 20 onto the camera chip 12 via the objective 14. The camera chip 12 of the event-based camera 10 comprises pixels, wherein the pixels are configured to generate sensor data independently and / or temporally asynchronously with other pixels of the camera chip 12 if a brightness change detected by the or the corresponding pixel is greater than a predetermined threshold value. The pixels are arranged in particular in a matrix. In the present exemplary embodiment, the event-based camera 10 comprises an optical filter 18, which is arranged in the objective 14 on the optical axis 28 after the last lens 16 of the objective 14. Furthermore, the event-based camera 10 in a second embodiment comprises two lighting devices 22 arranged in the objective lens 14, which are designed as ring light sources and emit light onto the camera chip 12 in such a directed manner that the camera chip 12 is illuminated, in particular the camera chip 12 is illuminated substantially uniformly, in particular with a uniform illumination intensity. In this second embodiment, a first of the two ring light sources of the lighting device 22 is arranged in the region of the first lens 16 between the camera chip 12 and the first lens 16 with a radiation direction toward the camera chip 12. The second ring light source of the lighting device 22 is then arranged in front of the second lens 16 with a radiation direction toward the camera 12. The ring light sources are designed in such a way that the individual point-shaped light sources are arranged equidistantly on the ring. In a variant of the second embodiment, the event-based camera 10 comprises only one lighting device 22 with a single ring light source.

[0034] Figure 3The structure of an event-based camera 10 of a third embodiment is shown. The event-based camera 10 comprises a camera chip 12 and an objective 14 with one or more lenses 16. The event-based camera 10 is configured to detect an object 20 in a detection range 24 of the event-based camera 10 by imaging the object 20 onto the camera chip 12 via the objective 14. The camera chip 12 of the event-based camera 10 comprises pixels, wherein the pixels are configured to generate sensor data independently and / or temporally asynchronously with other pixels of the camera chip 12 if a brightness change detected by the or the corresponding pixel is greater than a predetermined threshold value. The pixels are arranged in particular in a matrix. In the present embodiment, the event-based camera 10 comprises an optical filter 18, which is arranged in the objective 14 on an optical axis 28 after the last lens 16 of the objective 14. Furthermore, the event-based camera 10 comprises a beam splitter 30 in the third embodiment. The beam splitter 30 is arranged between two lenses 16 on the optical axis 28. In addition, the event-based camera 10 of the third embodiment is an illumination device 22 arranged outside the objective lens 14. The beam splitter 30 is configured to conduct light from the object 20 in the detection range 24 of the event-based camera 10 to the camera chip 12 essentially unchanged on the one hand and to deflect the light from the illumination device 22 on the other hand so that the light of the illumination device 22 illuminates the camera chip 12. In the third embodiment, the beam splitter 30 is configured as a percentage-divided beam splitter. In a variant, the beam splitter 30 is configured as a wavelength-dividing beam splitter. In addition, a diffuser 32 is arranged between the illumination device 22 and the beam splitter 30. The diffuser 32 is preferably configured as a diffuser glass for scattering the light emitted by the illumination device 22. The illumination device 22 having the diffuser 32 and the beam splitter 30 is configured to illuminate the camera chip 12 essentially uniformly, especially with a uniform illumination intensity.

[0035] Figure 4The structure of an event-based camera 10 of a fourth exemplary embodiment is shown. The event-based camera 10 comprises a camera chip 12 and an objective 14 with one or more lenses 16. The event-based camera 10 is configured to detect an object 20 in a detection range 24 of the event-based camera 10 by imaging the object 20 onto the camera chip 12 via the objective 14. The camera chip 12 of the event-based camera 10 comprises pixels, wherein the pixels are configured to generate sensor data independently and / or temporally asynchronously with other pixels of the camera chip 12 if a brightness change detected by the or the corresponding pixel is greater than a predetermined threshold value. The pixels are arranged in particular in a matrix. In the present exemplary embodiment, the event-based camera 10 comprises an optical filter 18, which is arranged in the objective 14 on an optical axis 28 after the last lens 16 of the objective 14. Furthermore, the event-based camera 10 comprises an illumination device 22 arranged outside the objective 14 in the fourth exemplary embodiment. The lighting device 22 is arranged in the detection range 24 of the event-based camera 10 in such a way that the light emitted by the lighting device 22 substantially only illuminates the camera chip 12. For this purpose, the event-based camera 10 comprises a shielding device 34, wherein the shielding device 34 is arranged between the lighting device 22 and the imaged object 20 in such a way that the object 20 is not affected by the light emitted by the lighting device 22. Preferably, the lighting device 22 is designed as a ring light source. Furthermore, it is preferred that the ring light source is designed in such a way that the individual point-shaped light sources are arranged equidistantly on the ring. Furthermore, the shielding device 34 is designed as a ring in such a way that the light emitted by the ring light source substantially only illuminates the camera chip 12 and substantially does not illuminate the object 20 in the detection range 24 of the event-based camera 10, so that the main part of the light is radiated in the direction of the camera chip 12. The lighting device 22 with the ring light source and the shielding device 34 is designed to illuminate the camera chip 12 substantially uniformly, in particular with a uniform lighting intensity.

[0036] Figure 5The structure of an event-based camera 10 of a fifth embodiment is shown. The event-based camera 10 comprises a camera chip 12 and an objective 14 with at least two lenses 16. The event-based camera 10 is configured to detect an object 20 in a detection range 24 of the event-based camera 10 by imaging the object 20 onto the camera chip 12 via the objective 14. The camera chip 12 of the event-based camera 10 comprises pixels, wherein the pixels are configured to generate sensor data independently and / or temporally asynchronously with other pixels of the camera chip 12 if a brightness change detected by the or the corresponding pixel is greater than a predetermined threshold value. The pixels are arranged in particular in a matrix. In the present embodiment, the event-based camera 10 comprises an optical filter 18, which is arranged in the objective 14 between at least two lenses 16 of the objective 14 on an optical axis 28. Furthermore, the event-based camera 10 comprises a beam splitter 30 in the fifth embodiment. The beam splitter 30 is arranged between the two lenses 16 on the optical axis 28. In addition, the event-based camera 10 of the fifth embodiment includes an illumination device 22 arranged outside the objective lens 14. The beam splitter 30 is configured to conduct light from an object 20 in the detection range 24 of the event-based camera 10 to the camera chip 12 essentially unchanged on the one hand and to deflect the light from the illumination device 22 on the other hand so that the light of the illumination device 22 illuminates the camera chip 12. In the fifth embodiment, the beam splitter 30 is configured as a beam splitter divided by percentage. In a variant, the beam splitter 30 is configured as a beam splitter that divides wavelengths. In addition, a diffuser 32 is arranged between the illumination device 22 and the beam splitter 30. The diffuser 32 is preferably configured as a diffuser glass for scattering the light emitted by the illumination device 22. The illumination device 22 with the diffuser 32 and the beam splitter 30 is configured to illuminate the camera chip 12 essentially uniformly, especially with a uniform illumination intensity. In a variant of the fifth embodiment, the illumination device 22 directly illuminates the beam splitter 30 in the absence of the diffuser 32. In particular, the objective lens 14 has a lens 16 in front of the camera chip 12 and a last lens 16 in front of the object 20, wherein the optical filter 18 is arranged between the lens 16 in front of the camera chip 12 and the beam splitter 30 and / or the beam splitter 30 is arranged between the optical filter 18 and the last lens 16. Preferably, the optical filter 18 has a transmission wavelength of 840 nm with a half-value width of 40 nm, so that the camera chip 12 has an observation wavelength of 840 nm. In particular, the lighting device 22 has an LED and / or the lighting device 22 radiates light at a radiation wavelength of 840 nm.

[0037] In a variant, reference is made to Figures 1 to 5The lighting device described in the embodiment is combined in an event-based camera, so that, for example, the event-based camera not only has Figure 3 The lighting device also has a Figure 4 lighting device.

[0038] In another variant, the optical filter is arranged on the camera chip on the optical axis and / or between the camera chip and the first lens and / or between the lenses. The illumination wavelength depends on the position of the optical filter, in particular on whether the optical filter is arranged on the optical axis before or after the illumination device. If the illumination device is arranged before the optical filter, that is, between the camera chip and the optical filter, any illumination wavelength can be selected. If the illumination device is arranged after the optical filter, that is, between the optical filter and the object, a wavelength corresponding to the filter wavelength is selected as the illumination wavelength.

[0039] In the embodiments described above, the illumination intensity caused by the illumination device on the camera chip is selected so that the illumination intensity is so small as to be less than the luminous intensity of the object to be detected, so that the object to be detected continues to be visible, and / or the illumination intensity is arranged so that interfering events, such as fumes and / or steam torches during welding and / or noise of the environment and / or event-based camera, are not detected as events.

[0040] Figure 6 The laser beam processing device 40 is shown. The laser beam processing device 40 includes a reference Figures 1 to 4 The described event-based camera 10. The laser beam processing device 40 is set up for monitoring a laser beam processing process, in particular a laser beam welding process, by means of the event-based camera 10. In this case, the laser beam processing device 40 includes an evaluation device 42, wherein the evaluation device 42 is set up for detecting events generated during the laser beam processing process by means of sensor data 41 generated by the event-based camera 10 and identifying these detected events 44 as spatters and / or spatters. In addition, the laser beam processing device 40 includes a laser control device 46 and a laser 48 for processing a workpiece. The laser beam processing device 40 is set up for adjusting parameters of the laser 48 by means of the laser control device 46 as a function of the detected events 44, in particular the identified spatters and / or spatters.

Claims

1. An event-based camera (10) for generating sensor data (41), in particular for a laser beam processing device (40), comprising a camera chip (12) and an objective lens (14) for imaging an object (20) located in a detection range (24) of the event-based camera (10) onto the camera chip (12), It is characterized in that The event-based camera (10) comprises an illumination device (22), wherein the illumination device (22) is designed to illuminate the camera chip (12) with light.

2. The event-based camera (10) according to claim 1, It is characterized in that The lighting device (22) is configured to uniformly illuminate the camera chip (12) with light.

3. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The lighting device (22) is arranged inside the objective lens (14).

4. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The lighting device (22) is designed to emit light in a diffuse manner into the objective (14) and / or the event-based camera (10) comprises a diffuser (32).

5. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The lighting device (22) is designed as a point light source and / or as a ring light source.

6. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The objective (14) comprises a beam splitter (30) and the beam splitter (30) is arranged on an optical axis (28) of the event-based camera (10), wherein the illumination device (22) is arranged outside the objective (14) so ​​that the illumination device (22) illuminates the camera chip (12) with light via the beam splitter (30).

7. The event-based camera (10) according to claim 6, It is characterized in that The diffuser (32) is arranged between the illumination device (22) and the beam splitter (30).

8. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The lighting device (22) is arranged outside the objective (14) of the event-based camera (10) in a detection range (24) of the event-based camera (10) so that light emitted by the lighting device (22) substantially only illuminates the camera chip (12).

9. The event-based camera (10) according to claim 8, It is characterized in that A shielding device (34) is arranged between the lighting device (22) and an object (20) to be imaged, so that the object (20) is not affected by the light emitted by the lighting device (22).

10. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The event-based camera (10) comprises an optical filter (18), wherein the optical filter (18) is arranged in a light path (26) of the event-based camera (10), in particular in the objective lens (14), and / or wherein a transmission wavelength of the optical filter (18) is substantially equal to a radiation wavelength of light radiated by the illumination device (22).

11. An event-based camera (10) according to any one of the preceding claims, It is characterized in that The camera chip (12) comprises a plurality of pixels, wherein a pixel generates sensor data (41) independently of other pixels and / or at a different time in time if a brightness change is greater than a predetermined threshold value.

12. The event-based camera (10) according to claim 11, It is characterized in that The pixels of the camera chip (12) are arranged in a matrix.

13. A laser beam machining device (40) comprising an event-based camera (10) according to any one of the preceding claims for monitoring a laser machining process.

14. The laser beam processing device (40) according to claim 13, It is characterized in that The laser beam processing device (40) comprises an evaluation device (42), wherein the evaluation device (42) is configured to detect spatters and / or splatters generated during laser beam processing by means of sensor data (41) generated by an event-based camera (10).

15. Use of an event-based camera (10) according to any one of claims 1 to 12 for monitoring a laser beam machining process, in particular for monitoring a laser beam welding process.

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