Device and method for characterizing at least one particle

Abstract

The invention relates to a device (10) for characterizing at least one particle (12) having the features of claim 1 and to a method for characterizing at least one particle (12) having the features of the independent claim.

Description

The invention relates to a device for characterizing at least one particle having features of claim 1 and to a method for characterizing at least one particle having features of the subordinate claim.Devices and methods for characterizing particles can be used in various applications for determining, for example, a particle position, a particle velocity or a particle size. This can serve, for example, for monitoring or regulating industrial production and machining processes.A device for determining the particle characteristic is known, for example, from DE 10 2019 209 213 A1 and comprises a light source, by means of which a laser beam is generated along a beam axis. A beam shaping optics is arranged along the beam axis. The beam shaping optics is designed to set a location-dependent intensity distribution of the laser beam in a measurement volume which extends in sections along the beam axis. A particle to be characterized, which is located in the measurement volume, reflects or scatters the laser beam. The reflected or scattered light is detected by means of a detector, which outputs an intensity signal to an evaluation unit. The evaluation unit serves for determining the particle characteristic within the measurement volume as a function of the intensity signal.In principle, it is desirable to be able to characterize the particle within the measurement volume with a high accuracy.It is therefore an object of the present invention to provide an apparatus and a method which are associated with a good relationship between the achievable accuracy in the particle characterization and the costs to be expended.The above object is achieved by a device for characterizing at least one particle having the features of claim 1.The apparatus comprises a light device for generating a light beam. The light device can be designed in particular as a laser device for generating a laser beam. The light device can comprise an LED (light-emitting diode), SLED (superluminescent light-emitting diode, VCSEL (vertical-cavity surface-emitting laser) and / or a laser source.The apparatus comprises a beam shaping optics for aligning the light beam along a beam axis. The beam axis is oriented along a first direction. The beam shaping optical unit is configured to generate a light distribution of the light beam along a second direction and a third direction. The light distribution along the second direction and the third direction corresponds in particular to a cross section of the light beam after the shaping by means of the beam shaping optical unit. In this case, the first, the second and the third direction are each aligned orthogonally with respect to one another. The first direction may be a Z direction, the second direction may be an X direction, and / or the third direction may be a Y direction.The device comprises a measurement volume which extends at least in sections along the beam axis and / or the light distribution of the light beam. In particular, the measurement volume extends at least in sections along the cross section of the light beam. The measurement volume can lie in particular in a plane which is spanned by the second and the third direction and / or be arranged parallel to this plane.The apparatus comprises a detection device. The detection device is configured to detect a light reflected and / or scattered by the particle which is located in the measurement volume. The detection device is arranged along a measurement axis and configured to generate an intensity signal. The measurement axis is arranged inclined by a measurement angle to the beam axis. In this way, in particular no light is reflected or scattered when no particle is present in the measurement volume, so that then also no intensity is detected (or no intensity signal is generated).The detection device comprises a line sensor and an imaging device. The imaging device can be designed as focusing optics or imaging optics. The line sensor can be designed as a line sensor or as a line camera. The line sensor may be configured as a one-dimensional detector of 1 by 1024 pixels. The imaging device is configured to focus (or image) the reflected and / or scattered light onto the line sensor.The line sensor may be configured to capture images at a speed greater than or equal to 250000 images per second. The line sensor may have dimensions of 250 μm (microns) by 13 mm (millimeters). The extent of the light distribution of the light beam along the second direction can be in the range from 10 μm to 300 μm. The extent of the light distribution of the light beam along the third direction can be between 500 μm and 10 mm. The line sensor is preferably oriented such that a long axis of the light beam (i.e. the extent of the light beam in the third direction) and a long axis of the line sensor are aligned with one another. In particular, the long axis of the light beam and the long axis of the line sensor can run in the same plane.As the particle moves through the measurement volume, the light beam is reflected and / or scattered by the particle. The imaging device can consist of an arrangement of mirrors and / or lenses which collect the reflected and / or scattered light and direct or focus it onto the line sensor. In particular, an image of the measurement volume is generated by the imaging device at the location of the line sensor.Since the particle is usually small (for example. 5 μm to 100 μm), the image of the particle falls only on one or a few pixels of the line sensor. The position of the particle along the third direction can therefore be determined with an accuracy given by the pixel size p divided by the magnification M of the imaging device. Thus, the accuracy is proportional to p / M.This allows precise characterization of the particle. In particular, the position of the particle along the third direction (in the range of micrometers) can be determined exactly.According to a development of the apparatus, the beam shaping optical unit is configured to influence the intensity and / or the polarization of the light beam within the light distribution. The beam shaping optics can be configured in particular to influence the intensity along the second direction and / or along the third direction. In other words, the intensity and / or the polarization of the light beam within the light distribution, in particular along the second and / or along the third direction, can be adjusted (as desired) by means of the beam shaping optical unit.This allows the desired light distribution of the light beam and thus the best possible generation of the intensity signal to be implemented.According to a development of the device, the device, in particular the beam shaping optics, can comprise at least one converter for converting a light beam profile of the light beam. The converter can be configured to convert a Gaussian beam profile into a flat-top beam profile.As a result, the desired beam profile, in particular a flat-top beam profile, can be implemented with simple means.According to a development of the device, the device can be configured such that the intensity of the light distribution along the third direction has a flat-top beam profile. The device can be configured in particular such that the intensity of the light distribution along the third direction is the same (or constant). Additionally or alternatively, the device can be configured such that the intensity of the light distribution along the second direction has a Gaussian beam profile.As a result, the intensity signal can be generated with a constant quality, in particular independently of the position of the particle along the third direction.According to a further development of the device, the device can comprise an evaluation unit. The evaluation unit can be configured to determine an, in particular position-dependent, characteristic of the particle within the measurement volume as a function of the intensity signal generated by the detection device. The characteristic of the particle can be, in particular, a position of the particle along the third direction.The characteristic can likewise be a position of the particle along the second direction, particle size and / or particle velocity. It is likewise conceivable that, in the case of a plurality of particles, a number of the particles within the measurement volume is determined by evaluating the intensity signal generated. The evaluation unit can be designed, for example, as a computer.An evaluation of the intensity signal generated can thereby be implemented with simple means.According to a development of the device, the line sensor can be configured such that the line sensor can be displaced along the measurement axis. In other words, the line sensor may be located outside a focusing plane of the imaging device. The line sensor can be moved in particular out of the imaging plane of the imaging device.Thus, the image focused by the imaging device propagates over more than one or a few pixels on the line sensor. In other words, the image focused by means of the imaging device is stretched or distorted or blurred to more pixels by the displacement of the line sensor along the measurement axis.This enables the position to be detected with an accuracy better than the above-mentioned accuracy proportional to p / M. The accuracy of the position determination of the particle along the third direction can thus be further optimized.According to a further development of the device, the measurement angle can be smaller than 90°, in particular smaller than 45°, preferably smaller than 15°.As a result, the device can be set as optimally as possible or the intensity signal generated can be further optimized.According to a further development of the apparatus, the apparatus can comprise a trigger device. The trigger device can be configured such that the line sensor only triggers (or detects) when the particle moves into the measurement volume. The line sensor does not detect (does not trigger) in particular if no particle moves into the measurement volume (does not trigger the trigger device).As a result, the line sensor can be triggered upon the arrival of the particle. As a result, the accuracy of the characterization of the particle within the measurement volume, in particular of the position determination along the third direction, can be further optimized. In addition, the number of particles characterized in a specific time can be maximized by a mode triggered in this way. In the present case, triggering of the line sensor means in particular the detection or generation of an intensity signal.According to a further development of the apparatus, the trigger device can comprise a light barrier. The light barrier can be arranged in front of the measurement volume with respect to the second direction. The separating device can be configured such that the particle triggers the trigger device and / or the line sensor when passing through the light barrier. In this case, the triggering of the trigger device and / or of the line sensor can be implemented with a time delay.This allows triggering of the trigger device or the line sensor to be implemented using simple means. In particular, the time-delayed triggering can prevent the trigger device or the line sensor from triggering when the particle is still outside the measurement volume (has not yet moved into the measurement volume).The above object is achieved by a method for characterizing at least one particle having the features of the subordinate claim. The method comprises the steps of:generating and aligning a light beam along a beam axis. The beam axis is oriented along a first direction.generating a light distribution of the light beam along a second direction and a third direction. The first, second and third directions are each oriented orthogonally to one another.moving the particle in a second direction through a measurement volume, which extends at least in sections along the beam axis and / or the light distribution of the light beam.detecting light reflected and / or scattered by the particles located in the measurement volume along a measurement axis by means of a line sensor. The measurement axis is arranged inclined by a measurement angle to the beam axis.generating an intensity signal that is dependent on the detected light. The detected light is dependent in particular on the position of the particle in the light beam.This allows precise characterization of the particle. In particular, the position of the particle along the third direction (in the range of micrometers) can be determined exactly.According to a development of the method, the method can comprise the step:influencing the intensity and / or polarization of the light beam within the light distribution. In this case, the intensity and / or the polarization can be influenced (adjusted) in particular along the second direction and / or the third direction.This allows the desired light distribution of the light beam and thus the best possible generation of the intensity signal to be implemented.According to a development of the method, the method can comprise the step:adjusting the intensity of the light distribution in such a way that the intensity of the light distribution along the third direction has a flat-top beam profile and / or a Gaussian beam profile along the second direction.As a result, the intensity signal can be generated with a constant quality, in particular independently of the position of the particle along the third direction.According to a development of the method, the method can comprise the step:determining an, in particular position-dependent, characteristic of the particle within the measurement volume by evaluating the generated intensity signal. The characteristic can be, in particular, a position of the particle along the third direction. The characteristic can likewise be a position of the particle along the second direction, particle size and / or particle velocity. It is likewise conceivable that, in the case of a plurality of particles, a number of the particles within the measurement volume is determined by evaluating the intensity signal generated.As a result, a characteristic of the particle, in particular a position-dependent characteristic, can be determined with simple means.According to a development of the method, the method can comprise the step:aligning the measurement axis such that the measurement axis is arranged inclined by a measurement angle to the beam axis. Alternatively or additionally, displacing the line sensor along the measurement axis. The measurement angle can be smaller than 90°, in particular smaller than 45°, preferably smaller than 15°.As a result, the accuracy of the characterization of the particle, in particular of the position determination of the particle along the third direction, can be further optimized.According to a development of the method, the method can comprise the step:triggered triggering of the line sensor by means of a trigger device. In this case, the trigger device can be triggered by means of the particle. The triggering of the trigger device and / or of the line sensor can be implemented with a time delay.As a result, the accuracy of the characterization of the particle, in particular of the position determination of the particle along the third direction, can be further optimized.According to a development of the method, a device according to the above explanations can be used for carrying out the method.With regard to the advantages which can be achieved thereby, reference is made to the relevant explanations relating to the device. For a further embodiment of the method, the measures described in connection with the device and / or the measures explained below can be used.Further features, details and advantages of the invention are evident from the wording of the claims and from the following description of an exemplary embodiment on the basis of the drawings. The following are shown: FIG. 1 shows a schematic illustration of a device for characterizing at least one particle, and FIG. 2 shows a schematic illustration of a particle and a measurement volume of the apparatus according to FIG. 1.In the following description and in the figures, corresponding components and elements bear the same reference numerals.FIG. 1 shows a schematic representation of a device 10 for characterizing at least one particle 12.The apparatus 10 comprises a light device 14 for generating a light beam 16. The light device 14 can be designed to generate a laser beam.The apparatus 10 comprises a beam shaping optical unit 18 for aligning the light beam 16 along a beam axis 20.The beam shaping optical unit 18 is configured to generate a light distribution 24 of the light beam 16 along a second direction 26 and a third direction 28. The first, second and third directions 22, 26, 28 are each oriented orthogonally to one another. The first direction 22 is oriented to the right in FIG. 1. The third direction 28 is oriented upward in FIG. 1. The second direction 26 is oriented in FIG. 1 perpendicular to the plane of the drawing, pointing out of the plane of the drawing (toward the observer).The device 10 comprises a measurement volume 30, which extends at least in sections along the beam axis 20 and / or along the light distribution 24 of the light beam 16.The apparatus 10 comprises a detection device 32. the detection device 32 is configured to detect a light 34 reflected and / or scattered by the particle 12 (if it is located in the measurement volume 30). The detection device 32 is arranged along a measurement axis 36 and is configured to generate an intensity signal. The reflected and / or scattered light 34 propagates in particular along the measurement axis 36.The measurement axis 36 is arranged at an inclination to the beam axis 20 by a measurement angle 38. In the present case, the measurement angle 38 means the smaller of the angles enclosed between the measurement axis 36 and the beam axis 20. The detection device 32 comprises a line sensor 40 and an imaging device 42. The imaging device 42 is configured to focus the reflected and / or scattered light 34 onto the line sensor 40.The beam shaping optical unit 18 can be configured to influence an intensity and / or a polarization of the light beam 16 within the light distribution 24, in particular along the second direction 26 and / or the third direction 28.In the present case, the apparatus 10 has a converter 44 for converting a beam profile of the light beam 16. It is likewise conceivable for the apparatus 10 to comprise a plurality of converters 44. The converter 44 can be formed as part of the beam shaping optics 18. The converter 44 is designed in the present case to convert a Gaussian beam profile of the light beam 16 into a flat-top beam profile.In the present case, the device 10 is configured such that the intensity of the light distribution 24 has a flat-top beam profile along the third direction 28 and a Gaussian beam profile along the second direction 26. The intensity of the light distribution 24 along the third direction 28 is thus constant in the present case.The apparatus 10 comprises an evaluation unit 46 in the present case. the evaluation unit 46 is configured to determine an, in particular position-dependent, characteristic of the particle 12 within the measurement volume 30 as a function of the intensity signal generated by the detection device 32. In the present case, the characteristic is a position of the particle 12 along the third direction 28.The line sensor 40 can be designed such that the line sensor 40 can be displaced along the measurement axis 36. The line sensor 40 can be moved out of the imaging plane of the imaging device.The measurement angle 38 can be smaller than 90°, in particular smaller than 45°, preferably smaller than 15°.FIG. 2 shows a schematic illustration of the particle 12 and a measurement volume 30 of the apparatus 10 according to FIG. 1 The particle 12 illustrated moves along the second direction 26 through the measurement volume 30 (indicated to the right in FIG. 2 by means of an arrow). The second direction 26 is oriented to the right in FIG. 2. The third direction 28 is oriented upward in FIG. 2. The first direction is oriented in FIG. 2 perpendicular to the plane of the drawing, pointing into the plane of the drawing (away from the observer).The device 10 is configured in the present case such that the line sensor 40 only triggers when the particle 12 moves into the measurement volume 30. For this purpose, the apparatus 10 has a trigger device 48. The trigger device 48 comprises a light barrier 50 arranged in front of the measurement volume 30 with respect to the second direction 26. The trigger device 48 is configured in the present case such that the particle 12 triggers the trigger device 48 and / or the line sensor 40 in particular with a time delay when passing through the light barrier 50. In the case of a spatial distance between the light barrier 50 and the measurement volume 30, the speed of the particle 12 should be known in this case so that the triggering functions. The time-delayed triggering can ensure that the line sensor 40 does not already trigger when the particle 12 passes through the light barrier 50, i.e. is still possibly located outside the measurement volume 30 (or in front of the measurement volume 30 with respect to the second direction 26.A method for characterizing at least one particle 12 is explained below with reference to FIGS. 1 and 2. The method comprises the steps of:generating and aligning a light beam 16 along a beam axis 20.generating a light distribution 24 of the light beam 16 along a second direction 26 and along a third direction 28.Moving the particle 12 in a second direction 26 through a measurement volume 30, the measurement volume 30 extending at least in sections along the beam axis 20 and / or the light distribution 24 of the light beam 16.detecting light 34 which is reflected and / or scattered by the particle 12 located in the measurement volume 30 along a measurement axis 36 by means of a line sensor 40.generating an intensity signal that is dependent on the detected light 34.The method may comprise the step of:influencing (or setting) intensity and / or polarization of the light beam within the light distribution 24, in particular along the second direction 26 and / or the third direction 28.The method may comprise the step of:adjusting the intensity of the light distribution 24 in such a way that an intensity of the light distribution 24 along the third direction 28 has a flat-top beam profile and / or along the second direction 26 a Gaussian beam profile.The method may comprise the step of:determining an, in particular position-dependent, characteristic of the particle 12 within the measurement volume 30 by evaluating the generated intensity signal. In particular, the characteristic can be a position of the particle 12 along the third direction 28.The method may comprise the step of:aligning the measuring axis 36 in such a way that the measuring axis 36 is arranged inclined by a measuring angle 38 with respect to the beam axis 20. Alternatively or additionally, the line sensor 40 can be displaced along the measurement axis 36.The method may comprise the step of:Triggered triggering of the line sensor 40 by means of a trigger device 48, The trigger device 48 can be triggered by means of the particle 12. The triggering of the line sensor 40 and / or of the trigger device 48 can be implemented with a time delay.To carry out the method, an apparatus 10 as described above can be used. In particular, this can be the device 10 shown in FIGS. 1 and 2.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2019 213 A1

[0003]

Claims

Apparatus (10) for characterizing at least one particle (12), comprising: - a light device (14) for generating a light beam (16); - a beam shaping optical unit (18) for aligning the light beam (16) along a beam axis (20), wherein the beam axis (20) is oriented along a first direction (22), wherein the beam shaping optical unit (18) is configured to generate a light distribution (24) of the light beam (16) along a second direction (26) and a third direction (28), wherein the first, the second and the third direction (22, 26, 28) are each aligned orthogonally to one another, - a measurement volume (30) which extends at least in sections along the beam axis (20) and / or the light distribution (24) of the light beam (16), - a detection device (32) configured to detect one of the particles (12), which is located in the measurement volume (30) for detecting reflected and / or scattered light (34), wherein the detection device (32) is arranged along a measurement axis (36) and is configured to generate an intensity signal, wherein the measurement axis (36) is arranged at an inclination to the beam axis (20) by a measurement angle (38), wherein the detection device (32) comprises a line sensor (40) and an imaging device (42), wherein the imaging device (42) is configured to focus the reflected and / or scattered light (34) onto the line sensor (40).Device (10) according to Claim 1, characterized in that the beam shaping optical unit (18) is configured to influence an intensity and / or a polarization of the light beam (16) within the light distribution (24), in particular along the second direction (26) and / or the third direction (28).Device (10) according to claim 1 or 2, characterised in that the device (10), in particular the beam shaping optics (18), comprises at least one converter (44) for converting a beam profile of the light beam (16), in particular from a Gaussian to a flat-top beam profile.Device (10) according to one of the preceding claims, characterized in that the device (10) is configured in such a way that an intensity of the light distribution (24) along the third direction (28) has a flat-top beam profile and / or along the second direction (26) a Gaussian beam profile.Device (10) according to one of the preceding claims, characterized in that the device (10) comprises an evaluation unit (46) which is configured to determine a characteristic, in particular a position along the third direction (28), of the particle (12) within the measurement volume (30) as a function of the intensity signal generated by the detection device (32).Device (10) according to one of the preceding claims, characterized in that the line sensor (40) is configured in such a way that the line sensor (40) is designed to be displaceable along the measurement axis (36).Device (10) according to one of the preceding claims, characterized in that the measurement angle (38) is less than 90°, in particular less than 45°, preferably less than 15°.Apparatus (10) according to one of the preceding claims, characterized in that the apparatus (10) comprises a trigger device (48), wherein the trigger device (48) is configured such that the line sensor (40) only triggers when the particle (12) moves into the measurement volume (30).Apparatus (10) according to Claim 8, characterized in that the trigger device (48) comprises a light barrier (50) arranged in front of the measurement volume (30) with respect to the second direction (26) and is configured in such a way that the particle (12) triggers the trigger device (48) and / or the line sensor (40) in particular with a time delay when passing through the light barrier (50).Method for characterizing at least one particle (12), comprising the steps of: - generating and aligning a light beam (16) along a beam axis (20), wherein the beam axis (20) is oriented along a first direction (22), - generating a light distribution (24) of the light beam (16) along a second direction (26) and a third direction (28), wherein the first, the second and the third direction (22, 26, 28) are each aligned orthogonally to one another, - moving the particle (12) in a second direction (26) through a measurement volume (30) which extends at least in sections along the beam axis (20) and / or the light distribution (24) of the light beam (16); detecting light (34), which is reflected and / or scattered by the particle (12) located in the measurement volume (30), along a measurement axis (36) by means of a line sensor (40), wherein the measurement axis (36) is arranged at an inclination to the beam axis (20) by a measurement angle (38), generating an intensity signal which is dependent on the detected light (34).Method according to Claim 10, characterized in that the method comprises the step of: - influencing intensity and / or polarization of the light beam (16) within the light distribution (24), in particular along the second direction (26) and / or the third direction (28).Method according to Claim 11, characterized in that the method comprises the step of: - setting the intensity of the light distribution (24) in such a way that the intensity of the light distribution (24) has a flat-top beam profile along the third direction (28) and / or a Gaussian beam profile along the second direction (26).Method according to one of Claims 10 to 12, characterized in that the method comprises the step of: - determining a characteristic, in particular a position along the third direction (28), of the particle (12) within the measurement volume (30) by evaluating the intensity signal generated.Method according to one of Claims 10 to 13, characterized in that the method comprises the step of: - aligning the measurement axis (36) in such a way that the measurement axis (36) is arranged at an inclination by a measurement angle (38) with respect to the beam axis (20), and / or displacing the line sensor (40) along the measurement axis (36), in particular wherein the measurement angle (38) is less than 90°, in particular less than 45°, preferably less than 15°.Method according to one of Claims 10 to 14, characterized in that the method comprises the step of: - triggering the line sensor (40) by means of a trigger device (48), wherein the trigger device (48) is triggered by means of the particle (12), in particular wherein the triggering of the line sensor (40) and / or of the trigger device (48) is implemented with a time delay.Method according to one of Claims 10 to 15, characterized in that a device (10) according to one of Claims 1 to 10 is used to carry out the method.

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