Devices and methods for characterizing particles

Abstract

The present invention relates to a device (1) for characterizing particles, comprising a light source (2) for projecting a light beam (4) along a beam axis (5) and a beam shape measurement optical unit (3) arranged along the beam axis (5) and configured to adjust a position-dependent intensity distribution of the light beam (4) within a measurement volume (6) partially extending along the beam axis (5). When a particle (7) is located within the measurement volume (6), a detector (10) is configured to detect a measurement beam (8) reflected and / or scattered by the particle (7) and output an intensity signal to an analysis unit. The analysis unit is configured to determine particle characteristics within the measurement volume based on the intensity signal. The beam shape measurement optical unit (3) is configured to shape the intensity distribution on a projection plane (xy) extending transversely to the beam axis (5) such that the intensity of the light beam is minimum along an outer contour (15) of the oval (11) and maximum at at least one point (14) within the oval (11).

Description

Technical Field

[0001] The present invention relates to a device as recited in the preamble of claim 1 and a method as recited in the preamble of claim 12.

[0002] Devices and methods of the type mentioned at the beginning are known per se and are used in various applications for determining particle position, particle velocity, or particle properties such as particle size, for example. This information can be used, for example, to monitor or control industrial manufacturing and machining processes.

[0003] A device for determining particle properties is known, for example, from DE102019209213A1 and comprises a light source that projects a light beam along a beam axis. A beam shape measuring optical unit is arranged along the beam axis. The beam shape measuring optical unit is configured to condition the position-dependent intensity distribution of the light beam within a measurement volume that extends at least partially along the beam axis. Characterized particles located within the measurement volume reflect or scatter the light beam at least partially as a measurement beam. This measurement beam is detected by a detector, which outputs an intensity signal to an analysis unit. The analysis unit is used to determine particle properties within the measurement volume based on the intensity signal.

Background Art

[0004] In principle, it is desirable to be able to characterize particles within the measurement volume with high accuracy. An improvement in accuracy compared to previously known devices is possible, for example, by increasing the power of the light source used, but this is typically associated with high costs. Therefore, the present invention is based on the object of proposing a device and a method that relate to a good ratio between the achievable accuracy for characterizing particles and the resulting costs.

[0005] Summary of the Invention This objective is achieved by a device having the features described in claim 1, and a method having the features described in claim 12. Advantageous further developments are the subject matter of each dependent claim.

[0006] As is known, the device according to the present invention has a light source for projecting at least one light beam along the beam axis. A beam shape measuring optical unit is positioned along the beam axis and configured to adjust the position-dependent intensity distribution of the light beam within a measurement volume that partially extends along the beam axis. A detector is used to detect the measurement beam reflected and / or scattered by particles in the measurement volume and to output at least one intensity signal to an analysis unit. The analysis unit is configured to determine the particle characteristics within the measurement volume based on the intensity signal.

[0007] The device according to the present invention differs from previously known devices in that the beam shape measuring optical unit is configured to shape a position-dependent intensity distribution on a projection plane extending laterally with respect to the beam axis within the measurement volume such that the intensity of the light beam is minimum along the outer contour of the oval and maximum at at least one point within the oval.

[0008] This invention is based on the finding that adjusting the position-dependent intensity distribution of a light beam having a basic oval shape on the projection plane contributes to improved accuracy in determining particle properties in larger spatial regions. Compared to a radially symmetric intensity distribution where the intensity of the light beam is minimum, for example, along a circular contour, the intensity distribution extends over longer lengths along the vertical axis of the oval and over shorter lengths along the transverse axis of the oval. In addition, the light beam can be focused more along the longitudinal axis than along the transverse axis. Therefore, compared to previously known devices, the light beam can have a generally higher power per unit area on the projection plane for the same light source power. This means that the light beam can be reflected and / or scattered by particles in the measurement volume with correspondingly higher intensity. It is possible to characterize particles with high spatial resolution in large spatial regions, particularly along the vertical axis of the oval.

[0009] Advantageously, the intensity of the light beam is maximum at least at the center point of the oval's surface, and in particular, a Gaussian intensity distribution may exist. The intensity decreases continuously from the center point toward the outer contour of the oval. In particular, the oval has a longitudinal axis and a transverse axis, with the oval being constructed symmetrically with respect to these axes, and the dimension along the longitudinal axis is larger than the dimension along the transverse axis. Preferably, the oval is an ellipse, and in particular not a circle.

[0010] Particle characteristics may be, for example, particle dimensions, or preferably, particle position along the vertical axis of an oval on the projection plane. In particular, the device is configured such that the particle position along the vertical axis can be determined with a spatial resolution of 1 micrometer. Preferably, the detector has a spatial resolution of 5 micrometers to 0.1 micrometers, particularly preferably 3 micrometers to 1 micrometer, and most preferably 1 micrometer within the measurement volume.

[0011] The particles may be solids located in a gas, vacuum, or liquid. They may also be oil droplets in a water bath, or conversely, water droplets in an oil bath. They may also be droplets in a gas or vacuum, or droplets emerging from a nozzle, particularly a spray nozzle.

[0012] The present invention is not limited to any particular embodiment of the light source. In a simple embodiment, the light source includes at least one laser having a laser diode, a superluminescent diode, a halogen emitter, or an equivalent light beam source.

[0013] It is within the scope of the present invention that at least the light source and detector may be in a transmission or reflection configuration. In a transmission configuration, the light source and detector are located on opposite sides of the projection plane. Here, the light beam is scattered by a characteristic particle so that the measurement beam exists as a transmission beam. In a reflection configuration, the light source and detector are located on the same side of the projection plane. The light beam is reflected by a characteristic particle so that the measurement beam exists as a reflection beam. It is further within the scope of the present invention that at least two detectors are provided, with the first detector and light source located on opposite sides of the projection plane and the second detector and light source located on one side of the projection plane. In such embodiments, a combination of reflection and transmission configurations is provided between the light source and the detector.

[0014] The beam shape measuring optical unit may include a cylindrical lens whose lens surface is curved along one axis, allowing for adjustment of the intensity distribution of the light beam according to the present invention. The detector may include a collector lens that focuses the measurement beam and directs it toward at least one sensor element of the detector. In particular, the sensor element is a photodiode that emits an electrical signal to the analysis unit when the measurement beam is detected, the amplitude of which preferably depends on the intensity of the measurement beam.

[0015] Preferably, at least the light source and the beam shape measuring optical unit are positioned in a fixed position along the beam axis, particularly in a defined alignment relative to each other. At least in a reflective configuration, the detector is preferably positioned so that the measuring axis capable of detecting the measurement beam is at a certain angle with respect to the beam axis of the optical beam.

[0016] The analysis unit can be configured as an electrical computing unit capable of determining particle properties. A mathematical model describing the analytically or empirically determined relationship between the intensity of the measurement beam and the particle properties can be implemented on the analysis unit. By measuring the intensity of the measurement beam, the intensity signal output by the detector can be assigned to the particle properties determined using the mathematical model.

[0017] Additionally or alternatively, discrete table values ​​can be stored in the analysis unit, thereby allowing the measured intensity values ​​of the beam to be compared with the stored intensity values ​​and assigned to the relevant particle characteristics.

[0018] Additionally or alternatively, at least one characteristic curve showing the intensity transition based on the degree of particle properties can be stored in the analysis unit. Using the characteristic curve, the measured intensity of the measurement beam can be assigned to the particle properties to be determined. In particular, the characteristic curve describes the intensity transition of the measurement beam based on the particle position along an axis in the projection plane, especially the vertical axis of an oval.

[0019] In an advantageous further development, the beam shape measuring optical unit is configured to adjust the position-dependent polarization distribution on the projection plane, in addition to the position-dependent intensity distribution, such that a first polarization and a second polarization with different polarization directions exist along the vertical axis of the oval. The detector is configured to determine at least two intensities of the measurement beam having the first polarization and / or the second polarization, and to output the two polarization-dependent intensity signals to an analysis unit. The analysis unit is configured to determine particle properties based on the two polarization-dependent intensity signals.

[0020] The further development described above is based on the applicant's discovery that the intensity of the measurement beam can simultaneously depend on multiple particle properties, such as particle position and particle size. This makes it difficult to definitively determine only one of these particle properties, for example, because varying particle sizes between different particles characterized at the same particle position can result in different measurable intensities. Due to the design of a beam shape measuring optical unit that can adjust the position-dependent intensity distribution and position-dependent polarization distribution in the projection plane, yet another optical property of the light beam can be adjusted and considered. This makes it possible to take into account not only the intensity but also the polarization of the measurement beam in order to determine a unique particle property, in particular the particle position. Such embodiments of the intensity distribution and polarization distribution mean that the measurement beam reflected and / or scattered by the particles can have at least two intensity components of different polarizations.

[0021] For better understanding, please refer to the following example of determining the positions of three particles. If the first particle is located within the measurement volume and scatters or reflects a light beam having a first intensity and a first polarization, then the first intensity and first polarization can be assigned to the first particle's position. If the second particle is located within the measurement volume and scatters or reflects a light beam with a second intensity and a second polarization that is higher than the first intensity, then it can be concluded that the second particle is in the second position. If the third particle is located within the measurement volume and scatters or reflects a light beam having a second intensity and a first polarization, then it can be concluded that the third position of the third particle corresponds to the first position of the first particle, and the second intensity is due to a larger particle size.

[0022] In a simple embodiment, the beam shape measuring optical unit may include a so-called retardation plate that generates a desired position-dependent polarization distribution having first and second polarization directions. Such a retardation plate is an optical component that can change the polarization and phase of the passing light wave as needed. Preferably, the retardation plate is configured as a so-called spatial polarization converter, for example, known from EP2705393B1 and manufactured according to a method known from US20200408953A1. Alternatively, the position-dependent polarization distribution can be generated using a so-called spatial light modulator or a so-called vortex plate.

[0023] The detector may comprise, for example, two photodiodes, each having a polarizing filter to enable polarization-sensitive triggering. The first photodiode may be configured to output a first electrical signal based on the intensity of a measurement beam having a first polarization. The second photodiode may be configured to output a second electrical signal based on the intensity of a measurement beam having a second polarization.

[0024] In a simple embodiment, as already described, a mathematical model can be implemented in the analysis unit that assigns a number of intensity values ​​of different polarizations to a corresponding number of particle properties, particularly particle positions. In particular, the analysis unit may have a stored analysis routine in which at least two intensity values ​​of different polarizations are set relative to each other, and this ratio is assigned to particle positions using a mathematical model and / or a table and / or characteristic curve. Instead of the ratio described above, a metric corresponding to the ratio can also be determined.

[0025] In an advantageous further development, the beam shape measurement optical unit is configured to generate a position-dependent polarization distribution such that there is an angle of 180 degrees between the polarization direction of the first polarization and the polarization direction of the second polarization. Along the vertical axis of the oval, there is at least one third polarization in the region of the points within the oval where the intensity is preferably maximum. There is an angle of 90 degrees in each case between the polarization direction of the first polarization and the polarization direction of the third polarization, and / or between the polarization direction of the second polarization and the polarization direction of the third polarization.

[0026] The above-mentioned further development enables a further improvement in the accuracy when determining particle characteristics. In this regard, the beam shape measurement optical unit is configured to adjust the third polarization. Further, the detector is configured to detect the intensity of the measurement beam having the third polarization. The analysis unit is further configured to determine the particle characteristics based on three intensity signals in the first, second, and third polarizations.

[0027] In a further advantageous further development, the beam shape measurement optical unit is configured to generate a position-dependent polarization distribution such that there is a fourth polarization along the vertical axis of the oval and between the first polarization and the third polarization, and / or between the second polarization and the third polarization, and there is an angle of 45 degrees between the polarization direction of the fourth polarization and the polarization direction of the third polarization.

[0028] The above-mentioned further development enables a further improvement in the accuracy when determining particle characteristics. In this regard, the beam shape measurement optical unit is configured to adjust the fourth polarization. Further, the detector is configured to detect the intensity of the measurement beam having the fourth polarization. The analysis unit is further configured to determine the particle characteristics based on four intensity signals in the first, second, third, and fourth polarizations.

[0029] In an advantageous further development, the detector is configured to be able to determine the polarization-dependent intensity components of the measurement beam in at least two of the polarizations of 0 degrees, 45 degrees, 90 degrees, and 135 degrees.

[0030] The above further development form is advantageous because the above polarization directions can be easily adjusted using a common beam shape measurement optical unit. The detector can have a plurality of photodiodes with at least two polarization filters, and the polarization filters are arranged relative to each other such that light from the photodiodes is detected only in the polarization direction of the polarization filter.

[0031] Preferably, there is no phase difference or a phase difference of 180° between portions of the light beam having different polarization directions. This facilitates the adjustment of linear polarization. However, research by the applicant has also shown that it is also advantageous to adjust circular or elliptical polarization in order to clearly determine particle characteristics, particularly particle position. Therefore, in an advantageous further development form, the light source and / or the beam shape measurement optical unit is configured to generate at least two light beams having a phase difference, and the phase difference is 90 degrees for adjusting circular polarization in the projection plane in at least the region, or the phase difference is between 0 degrees and 90 degrees or between 90 degrees and 180 degrees for adjusting elliptical polarization in the projection plane in at least the region.

[0032] In yet another advantageous further development form, the light source and / or the beam shape measurement optical unit is configured to shape a position-dependent intensity distribution in the projection plane such that the intensity of the light beam along the two outer contours of the two ovals with their vertical axes arranged in a V-shape relative to each other is minimized, and the intensity distribution within the region of the vertical axes of the two ovals is maximized. The detector is configured to detect the intensities of the two measurement beams in a time-shift manner. The analysis unit is used to determine the particle position within the measurement volume based on the time interval between the measured intensities of the two measurement beams.

[0033] The further development described above is based on the applicant's discovery that an embodiment of the position-dependent intensity distribution of a light beam, in which the intensity is minimal along the outer contour of the oval, can be amplified on the projection plane to enable reliable determination of particle characteristics, particularly particle position. When a particle crosses the measurement volume on the projection plane and the vertical axes of the two ovals, the two measurement beams are reflected and / or scattered from each other in a time-shifted manner and detected by the detector in the corresponding time shifts. Given that the angle between the vertical axes, which are arranged in a V-shape relative to each other, is known and the particle velocity is known, the particle position can be determined by considering the time interval between the two intensity signals. This further development is particularly advantageous when the particle velocities of the multiple particles being characterized are uniform and known.

[0034] Alternatively, the device can be configured such that the intensity of the light beam is minimum along the three outer contours of three ovals whose vertical axes are arranged in an N-shape relative to each other, and the intensity distribution is maximum in the region of the vertical axes of the three ovals. The detector is configured to detect the intensities of the three measurement beams in a time-shifted manner. The analysis unit is used to determine the position of particles within the measurement volume based on at least two time intervals between the measured intensities of the three measurement beams.

[0035] One advantage of the further development described above is that the particle position within the measurement volume can be determined independently of the particle velocity. In particular, the particle position can be determined based on the ratio of two time intervals. The applicant's discovery is that determining the ratio of these two time intervals enables reliable determination of the particle position, even with a changing, unknown particle velocity.

[0036] In a further advantageous and advanced form, the light source and / or beam shape measuring optical unit is configured to project two light beams having different wavelengths along their respective beam axes, such that these light beams overlap in the projection plane and thereby have a position-dependent intensity distribution and a position-dependent wavelength distribution. A detector is configured to detect at least one wavelength-dependent intensity of the measurement beam. An analysis unit is configured to determine the position of particles in the measurement volume based on the wavelength-dependent intensity of the measurement beam.

[0037] In addition to the intensity of the measurement beam, further optical properties can be considered using a position-dependent wavelength distribution to clearly determine particle characteristics. In particular, a position-dependent wavelength distribution can be used in addition to, or as an alternative to, a position-dependent polarization distribution to enable the clear determination of the particle's position within the measurement volume. The position-dependent intensity distribution can be formed symmetrically with respect to the vertical and horizontal axes of an oval. The position-dependent wavelength distribution may differ, for example, along the vertical axis at two spaced-apart positions. Such embodiments of intensity and wavelength distributions mean that the light beam reflected by the particle in the form of a measurement beam can have at least two wavelength components, and by considering this, it becomes possible to clearly determine the particle's position in the projection plane.

[0038] The detector may have multiple photodiodes configured to be wavelength-sensitive such that detected measurement beams with different wavelength components result in different signal amplitudes for the corresponding photodiodes. Wavelength-dependent signals can be evaluated using mathematical models, tables, or characteristic curves to determine particle characteristics, particularly particle position.

[0039] In a more advantageous further development, the measurement volume has a length along the beam axis that corresponds to twice the Rayleigh length of the light beam.

[0040] The Rayleigh length, as is known, represents the distance along the beam axis between the focal plane and the point where its cross-sectional area is twice that of the focal plane. Therefore, the dimensions and / or position of the measured volume relative to the beam axis can be adjusted based on the characteristics of the optical beam, particularly its focal plane.

[0041] Preferably, the beam shape measuring optical unit and / or detector is configured to form a measuring volume having adjustable dimensions depending on the application. Preferably, the oval in the projection plane has a height of 10 to 1000 micrometers and / or a width of 100 micrometers to 5 centimeters.

[0042] One advantage of determining particle positions based on multiple polarization-dependent intensity values ​​is that a camera system is not required. Instead, particle positions can be determined based on discrete values, and both the detector and analysis unit can have a simple configuration. The applicant's research has shown that the analysis unit can be configured to determine the positions of multiple particles at frequencies above 10 MHz.

[0043] In an advantageous further development, the light source and / or beam-shape measuring optical unit and / or detector are positioned in fixed positions relative to each other to form a stationary measurement volume and detect moving particles within the measurement volume. Alternatively, the light source and / or beam-shape measuring optical unit and / or detector are positioned movably to displace the measurement volume by scanning movement and detect stationary particles within the measurement volume. Preferably, the light source and / or beam-shape measuring optical unit and / or detector are positioned immovably relative to each other during scanning movement.

[0044] Scanning motion can be implemented by kinematics known in itself, such as a multi-jointed robotic arm or an equivalent device. In such embodiments of the device, surfaces can be inspected in particular to determine whether they are contaminated with one or more particles.

[0045] As described above, this objective can also be achieved by the method described in claim 12.

[0046] In the method according to the present invention for characterizing particles, a light beam is projected along the beam axis, and the light beam has a position-dependent intensity distribution in a measurement volume that partially extends along the beam axis. The particles to be characterized reflect or scatter at least partially the light beam within the measurement volume as the measurement beam. The particle properties within the measurement volume are determined based on at least one intensity of the measurement beam.

[0047] The key requirement for this method is that the position-dependent intensity distribution on the projection plane extending laterally with respect to the beam axis within the measurement volume is minimized along the outer contour of the oval and maximized at at least one point within the oval, particularly at the center of the oval's surface.

[0048] Preferably, this method can be carried out by the device according to the present invention or an advantageous further development thereof. Accordingly, the same description already provided above with respect to the device according to the present invention and advantageous further development thereof applies with respect to the advantages that can be achieved herein.

[0049] In a more advantageous further development, the light beam is generated with a position-dependent polarization distribution, and the particle properties are determined based on the polarization-dependent intensity of the measured beam.

[0050] In another advantageous further development, overlapping light beams of different wavelengths are generated within the measurement volume, and the overlapping light beams have a position-dependent intensity distribution and a position-dependent wavelength distribution on the projection plane, and the characterized particles within the measurement volume are determined based on the wavelength-dependent intensity of the measurement beams.

[0051] In a more advantageous further development, the position-dependent intensity distribution on the projection plane is generated such that the intensity of the light beam is minimum along the outer contours of two ovals with their vertical axes arranged in a V-shape, and maximum in the region of the vertical axes of the two ovals. The characterized particle reflects or scatters the light beam within the measurement volume as at least partially two measurement beams. The intensities of the two measurement beams are detected in a time-shift manner. Particle properties, particularly particle position, are determined within the measurement volume based on the time interval between the two measured intensities of the measurement beams.

[0052] Alternatively, a position-dependent intensity distribution within the projection plane is generated such that the intensity of the light beam is minimum along the outer contours of three ovals arranged in an N-shape with their vertical axes, and maximum in the region of the vertical axes of the three ovals. The intensities of the three measurement beams are detected in a time-shifted manner. The particle characteristics within the measurement volume are determined based on two time intervals between the measured intensities of the measurement beams, and preferably independently of the particle velocity.

[0053] Further advantages of the present invention are described below with reference to exemplary embodiments and drawings. [Brief explanation of the drawing]

[0054] [Figure 1] A schematic diagram of the device according to the present invention for characterizing particles is shown. [Figure 2] A first exemplary embodiment of a position-dependent intensity distribution having a position-dependent polarization distribution is shown. [Figure 3] This figure shows multiple polarization-dependent intensity transitions used to determine particle position. [Figure 4] This figure shows a second exemplary embodiment of a position-dependent intensity distribution. [Figure 5] This figure shows a third exemplary embodiment of a position-dependent intensity distribution. [Figure 6] This figure shows a fourth exemplary embodiment of a position-dependent intensity distribution.

[0055] Figure 1 shows a device 1 capable of optically determining particle positions. For this purpose, the device 1 comprises a laser 2 and a beam shape measuring optical unit 3, the beam shape measuring optical unit 3 comprising a vortex plate and a cylindrical lens in a manner not shown herein.

[0056] Laser 2 is used to generate a light beam 4 that extends along the beam axis 5. The cross section of the light beam 4 along the beam axis 5 serves as the measurement volume 6 through which the moving particle 7 passes. As shown in Figure 1, the particle 7 is shown at two positions during linear motion.

[0057] As shown in detail in Figures 2 and 3, the beam shape measuring optical unit 3, which has a cylindrical lens and a vortex plate, is used to adjust the position-dependent intensity distribution and position-dependent polarization distribution of the optical beam 4 in a projection plane extending perpendicular to the beam axis 5.

[0058] Particles 7 located within the measurement volume 6 reflect the light beam 4 at least partially in the form of a measurement beam 8, which is focused by a focusing lens 9 and directed towards a detector 10. The measurement beam 8 has multiple polarization-dependent intensities that can be determined by the detector 10.

[0059] In the exemplary embodiments shown herein, an analysis unit incorporated into the detector 10 is used to determine the desired particle position within the measurement volume 6 based on at least one polarization-dependent intensity of the measurement beam 8.

[0060] As shown in Figure 2, the light beam on the projection plane substantially has the shape of an oval 11, or ellipse, with two axes of symmetry. Along the vertical axis H extending perpendicularly, the oval has a height dimension 12 that is greater than the width dimension 13 along the horizontal axis extending horizontally. The intensity of the light beam is distributed such that it is maximum at the surface center point 14 of the oval 11 and minimum along the outer contour 15. Within the oval 11, there exists a two-dimensional Gaussian intensity distribution in a plane perpendicular to the projection plane. In other words, the intensity extends continuously in the region between the surface center point 14 and the circumferential outer contour 15, and the intensity starts at the surface center point 14 and decreases radially toward the outer contour 15.

[0061] Such an intensity distribution means that the light beam can be reflected at different intensities along the vertical axis H of the oval. By measuring the intensity of the measurement beam, particle properties can be determined with high precision. When the particle property to be determined is the particle position, it is advantageous to consider that the intensity of the measurement signal may also change based on the particle size. Therefore, the embodiment of the intensity distribution shown in Figure 2 enables the beam shape measuring optical unit to generate a position-dependent polarization distribution shown in Figure 2 by arrows 16, 17, 18, 19, and 20. Here, the first polarization 16 and the second polarization 17 exist along the vertical axis H, and they are spaced apart from each other along the vertical axis H of the oval 11, with their polarization directions at an angle of 180 degrees to each other. The third polarization 18 exists in the region of the surface center point 14, and its polarization direction has a polarization angle of 90 degrees with respect to the polarization directions of the first and second polarizations. Between the first polarization 16 and the third polarization 18 is the fourth polarization 19, and its polarization direction is at an angle of 45 degrees with respect to the polarization direction of the third polarization 18. Between the second polarization 17 and the third polarization 18 lies a fifth polarization 20, which also has an angular difference of 45 degrees compared to the third polarization 18. Unlike the illustrated example, the position-dependent polarization distribution is continuous along the vertical axis H and includes discretely shown polarizations 16, 17, 18, 19, and 20.

[0062] When particle 7 is located in the region of the projection plane and the vertical axis H of the oval 11, the light beam is reflected such that the measured beam has multiple intensity components of different polarizations. By considering these polarization-dependent intensity components, it becomes possible to determine the precise position of the particle in the projection plane.

[0063] Figure 3 shows a diagram with position-dependent intensity transitions 21, 22, 23, and 24. Each of these intensity transitions describes the polarization-dependent intensity of the light beam along the vertical axis of the oval in its projection plane. Here, the first intensity transition 21 corresponds to the position-dependent intensity of the light beam with the first polarization 18 described in Figure 2. The second intensity transition 22 corresponds to the position-dependent intensity of the light beam with the second polarization 16 and the third polarization 17 according to Figure 2. The polarization directions of polarizations 16 and 17 are at an angle of 180 degrees so that the polarizing filter transmits light from both polarizations 16 and 17. The third intensity transition 23 corresponds to the position-dependent intensity of the light beam with the fourth polarization 19 described in Figure 2. The fourth intensity transition 24 corresponds to the position-dependent intensity of the light beam with the fifth polarization 20 described in Figure 2.

[0064] When a particle is located within the projection plane of the light beam corresponding to the image plane in Figure 2, the reflectance measurement beam has multiple polarization-dependent intensities corresponding to the intensity transitions 21, 22, 23, and 24 shown in Figure 3, depending on the y-position of the particle. For example, when the particle is located at a height of 0 μm along the y-axis, the measurement beam has a dominant intensity component corresponding to the first intensity transition 21 and a corresponding first polarization 18. At the same time, the measurement beam in this example has less prominent intensity components corresponding to intensity transitions 23 and 24, and corresponding fourth polarization 19 and fifth polarization 20. In other words, at the y-position of 0 μm, polarization 18 according to Figure 2 is dominant, which can be represented by a linear superposition of equal portions of polarizations 19 and 20 according to Figure 2.

[0065] By measuring the polarization-dependent intensities using detector 10, these can be assigned to distinct positions of particles along the y-axis, for example, using a mathematical model or table. Here, the asymmetric transitions of intensity transitions 23, 24, in particular, allow for a clear distinction between two particle positions along the y-axis.

[0066] In an exemplary embodiment of device 1 shown in Figure 1, light is split into two beams by a so-called 50:50 beam splitter, regardless of polarization. Two photodiodes configured to detect different polarization components are positioned behind this beam splitter along the optical path. In this regard, the first photodiode is configured to detect polarizations 18, 16, and 17 as shown in Figure 2. The second photodiode is configured to detect polarizations 19 and 20. Once the split measurement beams are detected, each photodiode outputs an electrical signal corresponding to the intensity of the corresponding measurement light component of one of the polarizations described above. The signals are evaluated in an analysis unit, for example, using the mathematical model described above.

[0067] Figure 4 shows an alternative embodiment of the intensity distribution in the projection plane that can be formed using a device substantially corresponding to device 1 described in Figure 1. In contrast to the embodiment shown in Figure 1, the light source is configured to form a position-dependent intensity distribution in the projection plane such that the intensity is minimum along the outer contours of two ovals 11, 11' arranged in a V-shape with vertical axes H, H', and the intensity is maximum in the region of vertical axes H, H', in this case at the surface center points 14, 14' of the two ovals 11 or 11'. The detector is configured to detect the intensities of the two measurement beams in a time-shifted manner. The analysis unit is configured to determine the particle position in the measurement volume based on the time interval between the measured intensities of the two measurement beams.

[0068] The intensity distribution shown in Figure 4 extends along the x-axis over a range of approximately 1 mm. In an alternative embodiment, the extension along the x-axis can be up to 3 mm. When a particle moving through the measurement volume parallel to the x-axis crosses the projection plane xy and the vertical axes H, H' of two adjacent ovals 11, 11', the two measurement beams are reflected from each other in a time-shifted manner and detected by the detector with the corresponding time shifts. If the angle between the V-shaped vertical axes H, H' is known and the particle velocity is known, the particle position can be determined by considering the measured intensity. The application of this further development is particularly advantageous when the particle velocities of the multiple particles being characterized are known and not different. In this regard, it is possible to directly estimate the particle position based on the measured time intervals.

[0069] Figure 5 shows an alternative embodiment of an intensity distribution in a projection plane that can be formed using a device substantially corresponding to device 1 described in Figure 1. In contrast to the device shown in Figure 1, the light source is configured to form a position-dependent intensity distribution in the projection plane such that the intensity is minimum along the outer contours of three ovals 11, 11', 11'' with vertical axes H, H', H'' arranged in an N-shape, and the intensity is maximum in the region of vertical axes H, H', H'', in this case at the surface center points 14, 14', 14'' of each of the three ovals 11, 11', 11''; the detector is configured to detect the intensity of three measurement beams in a time-shifted manner; and the analysis unit is configured to determine the particle position in the measurement volume based on two time intervals between two measured intensities of the measurement beams, and in particular independently of particle velocity. The intensity distribution shown in Figure 5 extends along the x-axis over a range of approximately 1 mm. In the alternative embodiment, the extension along the x-axis may be up to 3 mm.

[0070] One advantage of the intensity distribution shown in Figure 5 is that the particle positions within the measurement volume can be determined independently of the particle velocity.

[0071] Figure 6 shows a further embodiment of the device, in which the light source 2 is configured to project two light beams having different wavelengths λ1 and λ2 along their respective beam axes, these light beams overlap in the projection plane xy and thereby have a position-dependent intensity distribution and a position-dependent wavelength distribution, the detector is configured to detect at least one wavelength-dependent intensity of the measurement beam and output the wavelength-dependent intensity signal to an analysis unit, the analysis unit is configured to determine the position of particles in the measurement volume based on the wavelength-dependent intensity signal.

[0072] In addition to the intensity of the measurement beam, further optical properties can be considered using a position-dependent wavelength distribution to clearly determine particle characteristics. In particular, a position-dependent wavelength distribution can be used in addition to, or as an alternative to, a position-dependent polarization distribution to enable the clear determination of the particle's position within the measurement volume. The embodiments of intensity and wavelength distributions shown in Figure 6 mean that the light beam reflected or scattered by the particle in the form of a measurement beam can have at least two wavelength components, and by considering this, the position of the particle in the projection plane can be clearly determined.

[0073] The detector may have multiple photodiodes configured to be wavelength-sensitive such that detected reflected beams with different wavelength components result in different signal amplitudes for the corresponding photodiodes. Wavelength-dependent signals can be evaluated using mathematical models, tables, or characteristic curves to determine particle characteristics, particularly particle position.

Claims

1. A device (1) for characterizing particles, A light source (2), specifically a laser, is provided for projecting at least one light beam (4) along the beam axis (5). The beam shaping optical unit (3) is positioned along the beam axis (5) and configured to adjust the position-dependent intensity distribution of the optical beam (4) within a measurement volume (6) that partially extends along the beam axis (5), The system includes at least one detector (10) configured to detect at least one measurement beam (8) reflected and / or scattered by the particle (7) when the particle (7) is located within the measurement volume (6), and to output at least one intensity signal to an analysis unit, The analysis unit is a device (1) configured to determine the particle characteristics within the measurement volume based on the intensity signal, The beam shaping optical unit (3) is configured to shape the position-dependent intensity distribution in a projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume such that the intensity of the light beam is minimum along the outer contour (15) of the oval (11) and maximum at least at the center of the surface of the oval (11) at at least one point (14) within the oval (11). The beam shaping optical unit (3) is configured to adjust the position-dependent polarization distribution within the projection plane (x-y), such that at least a first polarization (16) and a second polarization (17) having different polarization directions exist along the vertical axis (H) of the oval (11), and The detector (10) is configured to determine at least two intensities of the measurement beam (8) having the first polarization (16) and / or the second polarization (17), and to output two polarization-dependent intensity signals to the analysis unit. Device (1), wherein the analysis unit is configured to determine the particle characteristics, specifically the particle position, based on at least two polarization-dependent intensity signals.

2. The beam shaping optical unit (3) is configured to generate the position-dependent polarization distribution such that there is an angle of 180 degrees between the polarization direction of the first polarization (16) and the polarization direction of the second polarization (17). The device (1) according to claim 1, wherein at least one third polarization (18) is present along the vertical axis (H) of the oval (11) in the region of the point of the oval (11) where the intensity is maximum, and in each case there is an angle of 90 degrees between the polarization direction of the first polarization (16) and the polarization direction of the third polarization, and / or between the polarization direction of the second polarization (17) and the polarization direction of the third polarization.

3. The device (1) according to claim 2, wherein the beam shaping optical unit (3) is configured to generate the position-dependent polarization distribution such that the fourth polarization (19, 20) is along the vertical axis (H) of the oval (11) and between the first polarization (16) and the third polarization (18), and / or between the second polarization (17) and the third polarization (18), and there exists a 45-degree angle between the polarization direction of the fourth polarization (19, 20) and the polarization direction of the third polarization (18).

4. The device (1) according to claim 3, wherein the detector is configured to determine the polarization-dependent intensity component of the measurement beam (8) at at least two of the polarizations of 0 degrees, 45 degrees, 90 degrees, and 135 degrees.

5. The light source and / or the beam shaping optical unit is configured to generate at least two light beams having a phase difference, The phase difference is 90 degrees in order to adjust the circular polarization in the projection plane (x-y) in at least the region. Alternatively, the device (1) according to claim 1, wherein the phase difference is 0 to 90 degrees or 90 to 180 degrees in order to adjust the elliptical polarization in the projection plane (x-y) in at least a region.

6. A device (1) for characterizing particles, A light source (2), specifically a laser, is provided for projecting at least one light beam (4) along the beam axis (5). The beam shaping optical unit (3) is positioned along the beam axis (5) and configured to adjust the position-dependent intensity distribution of the optical beam (4) within a measurement volume (6) that partially extends along the beam axis (5), The system includes at least one detector (10) configured to detect at least one measurement beam (8) reflected and / or scattered by the particle (7) when the particle (7) is located within the measurement volume (6), and to output at least one intensity signal to an analysis unit, The analysis unit is a device (1) configured to determine the particle characteristics within the measurement volume based on the intensity signal, The beam shaping optical unit (3) is configured to shape the position-dependent intensity distribution in a projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume such that the intensity of the light beam is minimum along the outer contour (15) of the oval (11) and maximum at least at the center of the surface of the oval (11) at at least one point (14) within the oval (11). The light source (2), specifically the laser (2), and / or the beam shaping optical unit (3) are configured to shape the position-dependent intensity distribution within the projection plane (x-y) such that the intensity is minimized along the two outer contours of two ovals (11, 11') whose vertical axes (H, H') are arranged in a V-shape, and the intensity is maximized within the region of the vertical axes (H; H') of the two ovals (11, 11'). The detector (10) is configured to detect the intensity of the two measurement beams (8) in a time-shifted manner, and The device (1) is configured such that the analysis unit determines the position of particles in the measurement volume (6) based on the time interval between the measured intensities of at least two measurement beams (8).

7. A device (1) for characterizing particles, A light source (2), specifically a laser, is provided for projecting at least one light beam (4) along the beam axis (5). The beam shaping optical unit (3) is positioned along the beam axis (5) and configured to adjust the position-dependent intensity distribution of the optical beam (4) within a measurement volume (6) that partially extends along the beam axis (5), The system includes at least one detector (10) configured to detect at least one measurement beam (8) reflected and / or scattered by the particle (7) when the particle (7) is located within the measurement volume (6), and to output at least one intensity signal to an analysis unit, The analysis unit is a device (1) configured to determine the particle characteristics within the measurement volume based on the intensity signal, The beam shaping optical unit (3) is configured to shape the position-dependent intensity distribution in a projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume such that the intensity of the light beam is minimum along the outer contour (15) of the oval (11) and maximum at least at the center of the surface of the oval (11) at at least one point (14) within the oval (11). The light source (2), specifically the laser (2), and / or the beam shaping optical unit (3), is configured to shape the position-dependent intensity distribution on the projection plane such that the intensity is minimized along the three outer contours of three ovals (11, 11', 11'') whose vertical axes (H, H', H'') are arranged in an N-shape, and the intensity is maximized in the region of the vertical axes (H, H', H'') of the three ovals (11, 11', 11''). The detector (10) is configured to detect the intensity of the three measurement beams (8) in a time-shifted manner. The device (1) is configured such that the analysis unit determines the position of particles within the measurement volume (6) based on two time intervals between the measured intensities of the three measurement beams (8) and independently of the particle velocity.

8. A device (1) for characterizing particles, A light source (2), specifically a laser, is provided for projecting at least one light beam (4) along the beam axis (5). The beam shaping optical unit (3) is positioned along the beam axis (5) and configured to adjust the position-dependent intensity distribution of the optical beam (4) within a measurement volume (6) that partially extends along the beam axis (5), The system includes at least one detector (10) configured to detect at least one measurement beam (8) reflected and / or scattered by the particle (7) when the particle (7) is located within the measurement volume (6), and to output at least one intensity signal to an analysis unit, The analysis unit is a device (1) configured to determine the particle characteristics within the measurement volume based on the intensity signal, The beam shaping optical unit (3) is configured to shape the position-dependent intensity distribution in a projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume such that the intensity of the light beam is minimum along the outer contour (15) of the oval (11) and maximum at least at the center of the surface of the oval (11) at at least one point (14) within the oval (11). The light source (2), specifically the laser (2), and / or the beam shaping optical unit (3), have different wavelengths (λ １ , λ ２ Two light beams (4) having the above characteristics are projected along their respective beam axes (5), and the two light beams (4) overlap on the projection plane (x-y), thereby having the position-dependent intensity distribution and position-dependent wavelength distribution. The detector (10) is configured to detect at least one wavelength-dependent intensity of the measurement beam (8) and to output the wavelength-dependent intensity signal to the analysis unit. Device (1), wherein the analysis unit is configured to determine the position of particles within the measurement volume based on the wavelength-dependent intensity signal.

9. The device (1) according to any one of claims 1 to 8, wherein the detector (10) has a spatial resolution of 5 micrometers to 0.1 micrometers within the measurement volume.

10. At least the light source (2), specifically the laser (2), and / or the beam shaping optical unit (3) are fixedly positioned to form the measurement volume (6) in a stationary manner. or The device (1) according to any one of claims 1 to 8, wherein the light source (2), specifically the laser (2), and / or the beam shaping optical unit (3), and / or the detector (10) are arranged to be movable in order to displace the measurement volume (6) by at least one scanning movement.

11. A method for characterizing particle (7), The light beam (4) is projected along the beam axis (5) The light beam (4) has a position-dependent intensity distribution within a measurement volume (6) that partially extends along the beam axis, and The characterized particle (7) reflects or scatters the light beam (4) in the measurement volume (6) at least partially as a measurement beam (8), and A method for determining the particle characteristics within the measurement volume (6) based on at least one intensity of the measurement beam (8), The position-dependent intensity distribution in the projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume has an intensity that is minimum along the outer contour (15) of the oval (11) and maximum at at least one point (14) within the oval (11). A method wherein the light beam (4) has a position-dependent polarization distribution, and the particle characteristics are determined based on the polarization-dependent intensity of the measurement beam (8).

12. A method for characterizing a particle (7), The light beam (4) is projected along the beam axis (5), The light beam (4) has a position-dependent intensity distribution within a measurement volume (6) that partially extends along the beam axis, and The characterized particle (7) reflects or scatters the light beam (4) in the measurement volume (6) at least partially as a measurement beam (8), and A method for determining the particle characteristics within the measurement volume (6) based on at least one intensity of the measurement beam (8), The position-dependent intensity distribution in the projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume has an intensity that is minimum along the outer contour (15) of the oval (11) and maximum at at least one point (14) within the oval (11). Two light beams (4) having different wavelengths are generated and overlap within the measurement volume, and the overlapping light beams have the position-dependent intensity distribution and position-dependent wavelength distribution within the projection plane (x-y). A method in which the particle characteristics within the measurement volume are determined based on the wavelength-dependent intensity of the measurement beam (8).

13. A method for characterizing a particle (7), The light beam (4) is projected along the beam axis (5), The light beam (4) has a position-dependent intensity distribution within a measurement volume (6) that partially extends along the beam axis, and The characterized particle (7) reflects or scatters the light beam (4) in the measurement volume (6) at least partially as a measurement beam (8), and A method for determining the particle characteristics within the measurement volume (6) based on at least one intensity of the measurement beam (8), The position-dependent intensity distribution in the projection plane (x-y) extending laterally with respect to the beam axis (5) within the measurement volume has an intensity that is minimum along the outer contour (15) of the oval (11) and maximum at at least one point (14) within the oval (11). The position-dependent intensity distribution on the projection plane (x-y) is generated such that the intensity of the light beam (4) along the outer contour of the three ovals (11) arranged in an N-shape with vertical axes (H, H', H'') is minimum, and is maximum in the region of the vertical axes (H, H', H'') of the three ovals (11). The characterized particle (7) reflects or scatters the light beam (4) in the measurement volume (6) as at least partially three measurement beams (8), and the intensities of the three measurement beams are detected in a time-shift manner, and A method in which the particle characteristics, specifically the particle position, within the measurement volume (6) is determined based on two time intervals between the measured intensities of the measurement beam (8), and independently of the particle velocity.

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