Device for measuring a particle characteristic of a particle, and method for measuring a particle characteristic of a particle

Abstract

The invention relates to a device (10) for measuring a particle characteristic of a particle (12) located in a measurement volume (14) of the device (10), comprising: a light source (16) for generating a first light beam (18) and a second light beam (20), which each pass through the measurement volume (14); a detector apparatus (69) which is designed to detect the first light beam (18) reflected and / or scattered off the particle (12) and the second light beam (20) reflected and / or scattered off the particle (12) and to output an intensity signal; and an evaluation unit (82) which is designed to determine the particle characteristic on the basis of the intensity signal. The first light beam (18) and the second light beam (20) propagate along respective beam axes (30, 32) in the measurement volume (14). The beam axis (30) of the first light beam (18) and the beam axis (32) of the second light beam (20) define a propagation angle (34) not equal to 0° therebetween.

Description

Applicant: Q. ANT GmbH Handwerkstraße 29 70565 Stuttgart Title: Device for measuring the particle characteristics of a particle and method for measuring the particle characteristics of a particle Description The invention relates to a device for measuring a particle characteristic of a particle and a method for measuring a particle characteristic of a particle. A device and a method for measuring a particle characteristic are generally known and are used in various applications to determine particle characteristics such as position, velocity, or size. This can be used, for example, for monitoring or controlling industrial manufacturing and processing processes. DE 10 2022 123 464 A1 discloses a device for characterizing a particle. The device has a light source by means of which a light beam is projected along a beam axis. Beam-shaping optics of the device are arranged along the beam axis to establish a location-dependent intensity distribution of the light beam within a measurement volume that extends section by section along the beam axis. The particle to be characterized, located in the measurement volume, reflects or scatters the light beam at least partially as a measurement beam. This measurement beam is detected by means of a detector, which then outputs an intensity signal to an evaluation unit. The evaluation unit characterizes the particle as a function of the intensity signal. This results in the characterization of the particle in one dimension. The invention is based on the objective of providing a device and a method that each enable a precise measurement of a particle characteristic. The invention solves this problem by providing a device with the features of claim 1 and a method with the features of claim 13. Advantageous further developments and / or embodiments of the invention are described in the dependent claims. A device according to the invention is suitable for measuring the particle characteristics of a particle located in a measuring volume of the device. The device comprises a light source, a detector unit, and an evaluation unit. The light source is configured to generate a first light beam and a second light beam, each of which passes through the measuring volume. The detector unit is configured to detect the first light beam reflected and / or scattered by the particle and the second light beam reflected and / or scattered by the particle, and to output one or more intensity signals, in particular based on the detected first light beam reflected and / or scattered by the particle and / or based on the detected second light beam reflected and / or scattered by the particle.The evaluation unit is designed to determine the particle characteristics as a function of the intensity signal(s). The first and second light beams propagate along separate beam axes within the measurement volume. The beam axes of the first and second light beams define a propagation angle between them that is not equal to 0°. Advantageously, a propagation angle other than 0° allows for precise measurement of the particle characteristics. Another aspect of the device may be that the propagation angle allows for the simultaneous measurement of several properties of the particle quickly, precisely and reliably. Another aspect of the device may be that no polarization-resolved measurement is required to determine the particle characteristics. The particle can be a solid suspended in a gas, a vacuum, or a liquid. It can also be an oil droplet in a water bath, or conversely, a water droplet in an oil bath. Likewise, it can be a liquid droplet suspended in a gas or vacuum, or, in particular, a liquid droplet emanating from a nozzle, especially a spray nozzle. It can also be a gas bubble suspended in a liquid. Additionally or alternatively, the device can be configured to measure, and in particular detect, particles on a surface, for example, in the form of contamination on a clean surface. The surface can be, for example, the surface of a mirror or the surface of a wafer. The wafer can be a thin disk made of a semiconductor material, such as silicon. The wafer can serve as a basis for the fabrication of integrated circuits. In other words, the device can detect particle contamination of a surface. To detect particles on the surface, the surface and the device can be moved relative to each other. For example, the device can be moved across the surface. Additionally or alternatively, the surface can be moved relative to the device using a translational drive. Alternatively, to detect particles on the surface, the device and the surface can be held in a fixed position while the first light beam and the second light beam are scanned across the surface of the device using a scanning device, for example in the form of a motorized mirror. Due to the high resolution and rapid particle detection capabilities of the device, it may be particularly suitable for capturing, and especially detecting, contamination on large surfaces in a relatively short time. The particle characteristic can be a position, a velocity, and / or a size of the particle. In particular, the device can be configured such that the particle position can be determined with a spatial resolution of 1 micrometer. Preferably, the detector device can have a spatial resolution of 5 micrometers to 0.1 micrometers, more preferably 3 micrometers to 1 micrometer, and most preferably 1 micrometer. The measuring volume can be referred to as the measuring range or detection range. If a particle is located within the measuring volume, the device can be configured to measure the particle characteristics. The measuring volume can extend section by section along the beam axis of the first light beam and the beam axis of the second light beam. In particular, the measuring volume can extend along a light distribution of the first and second light beams. The measuring volume can be defined by the first light ray and the second light ray, in particular the light distribution of the first light ray and the second light ray. The light source can include at least one laser. The light source can include at least one laser with a laser diode, a superluminescent diode, a halogen lamp, or a comparable optical beam source for generating the light beams. The light source can include beam-shaping optics for shaping the light rays. These optics can include an optical element for splitting a light beam into a first and a second beam. This optical element can be a wedge-shaped optical element, for example, in the form of a prism or a biprism. The wedge angle of this optical element determines the propagation angle. The first and / or the second light beam can each be configured as a laser beam. The first and / or the second light beam can each have a tophat intensity distribution. This can advantageously improve the signal-to-noise ratio. Furthermore, the first and / or the second light beam can each have a Gaussian intensity distribution. This can advantageously increase the measurement volume. The detector device can include a power detector, particularly in the form of a photodiode, for detecting the intensity of the first light beam reflected and / or scattered by the particle and for detecting the intensity of the second light beam reflected and / or scattered by the particle. The detector device can include a collector lens by which the first light beam reflected and / or scattered by the particle and the second light beam reflected and / or scattered by the particle are focused and directed onto the power detector. Upon detecting the first light beam reflected and / or scattered by the particle and / or upon detecting the second light beam reflected and / or scattered by the particle, the power detector can output the intensity signal in the form of an electrical signal.The intensity signal can be output based on the first light beam reflected and / or scattered and detected by the particle, and / or the second light beam reflected and / or scattered and detected by the particle. The amplitude of the intensity signal can be determined by the intensity of the first light beam detected and reflected and / or scattered by the particle, and / or by the intensity of the second light beam detected and reflected by the particle. and / or scattered second light beam. A portion of the intensity signal from the detector device can be representative of the intensity of the first light beam reflected and / or scattered by the particle and / or representative of the intensity of the second light beam reflected and / or scattered by the particle. Such a detector device can be particularly suitable when the two light beams intersect outside the measuring volume. Within the measuring volume, the two light beams can be sufficiently separated. A sufficient separation can be understood as a distance that is at least three or four times the diameter of one of the two light beams. Alternatively, the detector system can include a first detector module and a second detector module. The first detector module can include a power detector, particularly in the form of a photodiode, for detecting the intensity of the first light beam reflected and / or scattered by the particle. The first detector module can include a collector lens that focuses the first light beam reflected and / or scattered by the particle and directs it onto the power detector. Upon detecting the first light beam reflected and / or scattered by the particle, the power detector can output the intensity signal as an electrical signal. The amplitude of the intensity signal can depend on the intensity of the detected first light beam reflected and / or scattered by the particle. The magnitude of the intensity signal from the first detector module can be representative of the intensity of the first light beam reflected and / or scattered by the particle. The second detector module can include a power detector, particularly in the form of a photodiode, for detecting the intensity of the second light beam reflected and / or scattered by the particle. The second detector module can include a collector lens by which the second light beam reflected and / or scattered by the particle is focused and directed onto the power detector. Upon detecting the second light beam reflected and / or scattered by the particle, the power detector can output the intensity signal as an electrical signal. The amplitude of the intensity signal can depend on the intensity of the detected second light beam reflected and / or scattered by the particle. The intensity signal of the second detector module can be representative of the intensity of the second light beam reflected and / or scattered by the particle. The intensity signal of the first detector module and the intensity of the second detector module can together form the intensity signal of the detector device. The intensity signal of the detector device can contain information about the power of the first light beam reflected and / or scattered by the particle and / or information about the power of the second light beam reflected and / or scattered by the particle. The intensity signal of the detector device can depend on the detected power of the first light beam reflected and / or scattered by the particle and / or on the detected power of the second light beam reflected and / or scattered by the particle. The evaluation unit may include an electrical computing unit, in particular in the form of a computer and / or a microcontroller, by means of which the particle characteristics can be determined based on the intensity signal of the detector device. The evaluation unit can be designed to determine, based on the intensity signal, a duration between the detection of the first light ray reflected and / or scattered by the particle and the detection of the second light ray reflected and / or scattered by the particle, and to determine the particle characteristics based on the duration. A mathematical model, a table, or a characteristic curve can be implemented, and in particular stored, on the evaluation unit. The mathematical model, the table, or the characteristic curve can each establish an analytical or empirical relationship between the intensity signal of the detector device and the particle characteristics, in particular between the temporal evolution of the intensity signal of the detector device and the particle characteristics. The evaluation unit is designed to determine the particle characteristics by applying the mathematical model, the table, or the characteristic curve based on the intensity signal, in particular the temporal evolution of the intensity signal. The axis of the first light ray and the axis of the second light ray cannot be parallel to each other. The device can have an X-axis, a Y-axis, and a Z-axis, each orthogonal to the others. The axis of the first light beam and the axis of the second light beam can each be arranged in an XZ-plane spanned by the X-axis and Z-axis, respectively. The axis of the first light beam and the axis of the second light beam can each be arranged orthogonal to the Y-axis. The axis of the first light ray and the axis of the second light ray can each form an angle with respect to the Z-axis. The magnitude of the angle between the axis of the first light ray and the Z-axis, and the magnitude of the angle between the axis of the second light ray and the Z-axis, can be equal or different. In particular, the magnitude of the angle between the axis of the first light ray and the Z-axis, and the magnitude of the angle between the axis of the second light ray and the Z-axis, can be equal to half the propagation angle. Alternatively, the angle between the axis of a light ray and the Z-axis can be 0°. If the axis of the first light ray and the axis of the second light ray are arranged at right angles to each other, the angle between the axis of the first light ray and the Z-axis can be 45° and the angle between the axis of the second light ray and the Z-axis can be 45°. If the propagation angle is not equal to 90° or 0°, particularly if it is less than 90° or greater than 0°, the evaluation unit can be configured to perform a coordinate transformation between a non-perpendicular and a perpendicular coordinate system. The perpendicular coordinate system can be defined by the X-axis, Y-axis, and Z-axis of the device. For example, a particle can move parallel to the x-axis at a known and constant speed. During this movement, the particle can pass through the first and second light beams. The evaluation unit can detect the time interval between the intensity signal of the first light beam (reflected and / or scattered by the particle) and the intensity signal of the second light beam (reflected and / or scattered by the particle), which is generated as the light beams pass through. Based on the measured time interval and the known speed, the evaluation unit can calculate the distance between the first and second light beams. The evaluation unit can determine the particle's position on the Z-axis based on the dispersion angle and distance. This enables the device to measure the particle's characteristics. For example, a particle can move parallel to the X-axis at a constant speed and in a known position on the Z-axis. During this movement, the particle can pass through the first and second light beams. The evaluation unit can detect the time interval between the intensity signal of the first light beam (reflected and / or scattered by the particle) and the intensity signal of the second light beam (reflected and / or scattered by the particle), which is generated as the light beams pass through. Based on the known position on the Z-axis and the propagation angle, the evaluation unit can determine the distance between the first and second light beams. Based on this distance and the measured duration, the evaluation unit can determine the particle's velocity. Thus, the device is designed to measure a particle characteristic. Another aspect of the device is that polarization-resolved measurement is not required for measuring particle characteristics. The first light beam and / or the second light beam can be unpolarized. In a further development of the device, the light source is configured to generate a third light beam that passes through the measuring volume. The detector is configured to detect the third light beam reflected and / or scattered by the particle. The third light beam propagates within the measuring volume along a beam axis. The beam axis of the third light beam can be parallel, or in particular parallel and offset, to the beam axis of the first light beam. Advantageously, this allows the speed and position of the particle to be measured simultaneously. The description of the first or second light ray can apply accordingly to the third light ray, and in this respect reference can be made to the above statements. The intensity signal of the detector device can be output based on the third light beam reflected and / or scattered by the particle and detected. The amplitude of the intensity signal can depend on the intensity of the detected third light beam, which is reflected and / or scattered by the particle. A certain amount of the detector's intensity signal can be representative of the intensity of the third light beam reflected and / or scattered by the particle. In particular, the axis of the third light ray can be arranged in the XZ plane spanned by the X-axis and Z-axis. This allows the axis of the first light ray, the axis of the second light ray, and the axis of the third light ray to be arranged in the same plane. For example, a particle can move parallel to the X-axis at a constant speed. During this movement, the particle can pass through the first, second, and third light beams. The evaluation unit can measure the first duration between the intensity signal of the first light beam (reflected and / or scattered by the particle) and the intensity signal of the second light beam (reflected and / or scattered by the particle), and the second duration between the intensity signal of the second light beam (reflected and / or scattered by the particle) and the intensity signal of the third light beam (reflected and / or scattered by the particle). A quotient or ratio of the first duration to the second duration can represent one position of the particle on the Z-axis.In particular, the ratio of the first duration to the second duration can be equal to the ratio of the distance between the first and second light beams to the distance between the second and third light beams. Based on this ratio, the evaluation unit can determine the particle's position on the Z-axis. Based on the absolute values ​​of the first and second durations, the evaluation unit can determine the particle's velocity. Specifically, based on the distance between the first and third light beams and the sum of the first and second durations, the evaluation unit can determine the particle's velocity. It is also conceivable that the device could be designed to measure the particle characteristics using more than three light beams. In particular, the light source could be designed to generate more than three light beams. This would allow for the measurement of additional positions and / or velocities of the particle in the direction of the other axes. In a further development of the device, the ray axis of the first light ray and the ray axis of the second light ray intersect at a single point. Additionally or alternatively, the ray axis of the second light ray and the ray axis of the third light ray intersect at a single point. If the axes of the first and second light rays, as well as the axes of the second and third light rays, intersect, the axes of the three light rays can be arranged in a " "-shaped manner. The position of the intersection point between the ray axis of the first light ray and the ray axis of the second light ray, and the position of the intersection point between the ray axis of the second light ray and the ray axis of the third light ray, can differ from each other. In a further development of the device, the wavelengths of the light rays differ from each other. Advantageously, this allows for a better signal-to-noise ratio of the intensity signals. In particular, the different wavelengths enable the light beams to be arranged close together without the detection of one beam being affected by the others. This results in a more compact device design. For example, the wavelength of the first light beam and the wavelength of the second light beam can differ from each other. Additionally or alternatively, the wavelength of the second light beam and the wavelength of the third light beam can differ from each other. Additionally or alternatively, the wavelength of the first light beam and the wavelength of the third light beam can differ from each other. The detector system can have multiple power detectors. Each power detector can be assigned to a light beam. The number of power detectors can equal the number of light beams. The detector arrangement can include a plurality of wavelength filters, for example in the form of bandpass filters, preferably in the form of dichroic mirrors. Each wavelength filter can be arranged upstream of one of the power detectors. Each wavelength filter can be configured to filter the wavelength reflected by the particle and / or to direct the scattered light beam assigned to the power detector onto the power detector of the detector device and not to direct the remaining light beams reflected and / or scattered by the particle onto the power detector. For example, a wavelength filter can be placed in front of each power detector. The wavelength filter is transparent to one wavelength of the light beam assigned to the power detector. This allows the light beam reflected and / or scattered by the particle, which is assigned to the power detector, to reach the power detector. The wavelength filter is reflective to the wavelengths of the other light beams. This prevents the remaining light beams, reflected and / or scattered by the particle and not assigned to the power detector, from reaching the power detector. Another aspect may be that this allows each power detector to detect the power and / or intensity of its assigned light beam undisturbed by the other light beams. In a further development of the device, each light beam from the light source exhibits an intensity profile in a cross-section that is constant along an outer contour of an oval and is maximal at at least one point within the oval, in particular at the center of the oval's surface. The light source has beam-shaping optics configured to adjust a spatially dependent polarization distribution for each light beam in a cross-section such that the light beam exhibits at least a first polarization and a second polarization with different polarization directions along a vertical axis of the oval. The detector device is configured to detect the respective light beam reflected and / or scattered by the particle with polarization resolution and to output a polarization-resolved intensity signal.The evaluation unit is designed to determine the particle characteristics as a function of the polarization-resolved intensity signal of the detector device. Advantageously, this allows the particle's position to be measured simultaneously in two mutually orthogonal directions. In particular, this enables the particle's position to be measured with very high accuracy, almost in real time. The beam-shaping optics can include a grating for generating the spatially dependent polarization distribution. The wedge-shaped optical element can incorporate the grating. In particular, the biprism can incorporate the grating. Each oval can enclose a power content of the respective light beam that is 86.5% of the power of the light beam. The oval can have a vertical axis and a horizontal axis perpendicular to the vertical axis. The oval can be symmetrical about the vertical axis and / or the horizontal axis. The oval can have a larger dimension along the vertical axis than along the horizontal axis. Each light ray can exhibit a location-dependent intensity distribution. The intensity distribution of each light ray can have an oval cross-sectional shape. The intensity distribution can extend over a greater length along the vertical axis of the oval than along a horizontal axis of the oval that is orthogonal to the vertical axis. The vertical axis of each light ray can be aligned perpendicular to the XZ plane. Advantageously, the intensity of the light beam is maximal at least at one point on the oval's surface, where a Gaussian intensity distribution may be present. In this case, the intensity decreases continuously from the surface's center towards the oval's outer contour. Alternatively, each light ray can exhibit a tophat-shaped intensity distribution, at least along the vertical axis. The detector device can be configured to detect the first light beam reflected and / or scattered by the particle, the second light beam reflected and / or scattered by the particle and / or the third light beam reflected and / or scattered by the particle with polarization resolution and to output a polarization-resolved intensity signal. The detector device may include a polarizer. The power detector may consist of two photodiodes. The polarizer can split the light beam reflected and / or scattered by the particle into two partial beams that are orthogonally polarized to each other, and direct the partial beam with one polarization onto one photodiode and the The partial beam with the other polarization is directed to the other photodiode. This allows the detector to capture the light beam reflected and / or scattered by the particle with polarization resolution. The intensity signal can have a first partial signal for the partial beam with one polarization and a second partial signal for the partial beam with the other polarization. The evaluation unit can determine the particle characteristics based on the ratio of the first partial signal to the second partial signal. Additionally, the power detector can include two further photodiodes and one further polarizer. The further polarizer can be rotated by 45° relative to the primary polarizer. This further polarizer can split the light beam reflected and / or scattered by the particle into a third and a fourth partial beam, which are orthogonally polarized to each other. The third partial beam, with one polarization, is directed to one of the further photodiodes, and the fourth partial beam, with the other polarization, to the other. This allows the detector to capture the light beam reflected and / or scattered by the particle with more precise polarization resolution. The intensity signal can include a third partial signal for the third partial beam and a fourth partial signal for the fourth partial beam. This allows the polarization to be measured in horizontal, vertical, diagonal, and antidiagonal directions. The evaluation unit can determine the particle characteristics based on the ratios of the partial signals to each other. For example, a particle moving parallel to the X-axis can pass through at least the first and second light beams. Based on the polarization-resolved intensity signal, the evaluation unit can determine the particle's position on the Y-axis. Further details can be found in DE 10 2022 123 464 A1. The paragraphs

[0006] until

[0053] The provisions of DE 10 2022 123 464 A1 regarding the location-dependent polarization distribution of the light beam and the polarization-dependent measurement of the particle characteristics are hereby incorporated into the present description by reference. In a further development of the device, there is an angle of 90 degrees or 180 degrees between the polarization directions of the first and second polarizations. The polarization of each light beam can change continuously along the vertical axis. For example, the polarization can change from the first polarization to the second polarization through continuous rotation. Every light ray can exhibit a third polarization along its vertical axis between the first and second polarizations. This third polarization can differ from both the first and second polarizations. The third polarization can be a first polarization rotated by 90°. In other words, the third polarization is the same as the first polarization if the first polarization is rotated by 90°. In a further development of the device, the location-dependent polarization distribution exhibits a continuous change in the polarization direction along the vertical axis of the oval. In a further development of the device, the location-dependent polarization distribution exhibits a rotational order along the vertical axis of the oval, in particular from the first polarization to the second polarization. Rotational order can be understood as a measure that defines the spatial variation of the polarization direction along the vertical axis. The rotational order can quantify the frequency with which the polarization direction of a light beam completes a full 180° rotation from the first polarization to the second polarization along the vertical axis. With a polarization order of 0, the polarization direction cannot exhibit a spatially dependent polarization distribution. With a polarization order of 1, the polarization direction rotates 180° once along the vertical axis. With a polarization order greater than 1, the polarization direction rotates 180° multiple times along the vertical axis. The order of rotation can have a value greater than or equal to 2. The rotational orders of the light rays can be the same. In a further development of the device, the rotational order of the first light beam and the rotational assignment of the second light beam differ from each other. Additionally or alternatively, the rotational order of the second light beam and the rotational assignment of the third light beam differ from each other. Additionally or alternatively, the rotational order of the first light beam and the rotational assignment differ. of the third light beam from each other. Advantageously, this allows for a better signal-to-noise ratio of the intensity signals. In a further development of the device, the beam axis of the first light beam and the beam axis of the second light beam define a propagation plane. Each vertical axis of the oval of a light beam is aligned with the propagation plane at an oval angle. In a further development of the device, each oval angle is approximately 90°, in particular 90°. This makes it particularly easy to determine the position of the particle in the Y-direction based on the polarization measurement of the light beam reflected and / or scattered by the particle. In a further development of the device, each oval angle is approximately 0°, particularly 0°. This case can be significantly more advantageous for some applications than cases where the oval angle is approximately 90°. This allows the vertical axes to be arranged within the XZ plane. A method according to the invention is designed for measuring a particle characteristic of a particle located in a measuring volume.The method comprises the following steps: generating a first light beam and a second light beam, each passing through the measurement volume, wherein the first light beam and the second light beam each propagate along a beam axis within the measurement volume, and wherein the beam axis of the first light beam and the beam axis of the second light beam define a propagation angle between them that is not equal to 0°; detecting the first light beam reflected and / or scattered by the particle and outputting one or more intensity signals; detecting the second light beam reflected and / or scattered by the particle and outputting one or more intensity signals; and determining the particle characteristic based on the intensity signal of the first light beam reflected and / or scattered by the particle and the intensity signal of the second light beam reflected and / or scattered by the particle. The method can be configured to operate the previously described device. The previously given description of the device can apply to identical or functionally equivalent features of the method, and / or vice versa. Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All information contained in the figures, their description, and The features disclosed in the claims can be essential to the invention both individually and in any combination with one another. They show: Fig. 1 shows a schematic representation of a device for measuring the particle characteristics of a particle. Fig. 2 shows a schematic sectional view of a first light beam and a second light beam of the device of Fig. 1 along their beam axes. Fig. 3 shows a schematic sectional view of a cross-section of the first light ray of Fig. 2 with a location-dependent intensity distribution, wherein a rotational order of the first light ray is 1, Fig. 4 shows a diagram with a plurality of polarization-dependent intensity profiles for determining a particle position, Fig. 5 Sectional views for a further embodiment of a first light ray and a second light ray, wherein the rotational order of the first light ray is 6 and the rotational order of the second light ray is 5, and Fig. 6 shows a sectional view of light rays from another embodiment of a device. Fig. 1 shows a device 10 for measuring a particle characteristic of a particle 12 which is located in a measuring volume 14 of the device 10. The particle 12 is a solid suspended in a liquid. The liquid flows through the measuring volume 14 at a known or unknown flow velocity. In Fig. 1, the particle 12 is shown both shortly before entering the measuring volume 14 and within the measuring volume 14. In an alternative embodiment not shown, the particle can be a solid suspended in a liquid, a gas, or a vacuum. In another alternative embodiment not shown, the particle can be a gas bubble in a liquid, an oil droplet in an aqueous liquid, or vice versa. In yet another alternative embodiment not shown, the particle can be a liquid droplet suspended in a gas or a vacuum. The device 10 has a light source 16 which is designed to generate a first light beam 18 and a second light beam 20, each passing through the measuring volume 14. The light source 16 has a laser 22 in the form of a laser diode for generating a laser beam 24. The light source 16 has a beam shaping optic 26 for shaping the first light beam 18 and the second light beam 20. The beam shaping optic 26 has an optical element (not shown), for example in the form of a Glan-Taylor beam splitter or a biprism, for splitting the laser beam 24 into the first light beam 18 and the second light beam 20. The beam shaping optics 26 has a polarizing optic, for example a vortex plate, and a cylindrical lens for generating a spatially dependent polarization distribution over a cross-section of the first light beam 18. The polarizing optic can ideally be designed as a plate with birefringence varying along one direction. The beam shaping optics 26 has a further polarizing optic and a further cylindrical lens for generating a spatially dependent polarization distribution over a cross-section of the second light beam 20. The further polarizing optic can ideally be designed as a plate with birefringence varying along one direction. The device 10 has an X-axis, a Y-axis, and a Z-axis, each of which is orthogonal to the others. The first light beam 18 and the second light beam 20 propagate in an XZ-plane of the device 10, which is defined by the X-axis and Z-axis. The particle 12 moves in a direction of motion 28 that is parallel to the X-axis. Fig. 2 shows the path of the first light beam 18 and the path of the second light beam 20 within the measuring volume 14. The first light beam 18 propagates within the measuring volume 14 along a beam axis 30. The second light beam 20 propagates within the measuring volume 14 along a beam axis 32. The beam axes 30 and 32 of the two light beams 18 and 20 are each perpendicular to the Y-axis. The axes 30, 32 of the two light rays 18, 20 are not parallel to each other. The axis 30 of the first light ray 18 and the axis 32 of the second light ray 20 define a propagation angle 34 between them, which is not equal to 0°. The propagation angle 34 has a value in the range of 0° to 90°. In the illustrated embodiment, the propagation angle 34 is 20°. The ray axis 30 of the first light ray 18 and the ray axis 32 of the second light ray 20 each run at an angle with respect to the Z-axis. The magnitude of the angle between the ray axis 30 of the first light ray 18 and the Z-axis, and the magnitude of the angle between the ray axis 32 of the second light ray 20 and the Z-axis, are equal and each amount to half of the propagation angle 34. The beam axis 30 of the first light beam 18 and the beam axis 32 of the second light beam 20 intersect at a point of intersection 36. The point of intersection 36 can be located within the measuring volume 14. Fig. 3 shows a cross-section of the first light ray 18 orthogonal to its ray axis 30. A cross-section of the second light ray 20 has the same characteristics as the cross-section of the first light ray 18, therefore the cross-section of the first light ray 18 shown in Fig. 3 and the following description apply accordingly to the cross-section of the second light ray 20. The polarization optics and the cylindrical lens of the beam shaping optics 26 serve to adjust a location-dependent intensity distribution as well as a location-dependent polarization distribution of the first light beam 18. Fig. 3 shows that the first light ray 18 has the cross-sectional shape of an oval 38 with a vertical axis 40 and a horizontal axis 42 orthogonal to the vertical axis 40. The horizontal axis 42 runs parallel to the x-axis and the vertical axis 40 runs parallel to the y-axis. The vertical axis 40 and the horizontal axis 42 are each axes of symmetry of the oval 38. The oval 38 is formed as an ellipse. Along the vertical axis 40, the oval 38 has a height dimension 44 that is greater than a width dimension 46 along the horizontal axis 42. The intensity of the first light ray 18 is distributed such that it is maximal at the center point 48 of the oval 38 and constant along an outer contour 50. The oval 38 can enclose a power content of the first light ray 18 that is 86.5% The power of the first light beam 18 is [value missing]. Within the oval 38, a two-dimensional Gaussian intensity distribution exists in an XY plane spanned by the X-axis and Y-axis. In other words, the intensity is continuous in a region between the center of the surface 48 and the circumferential outer contour 50, decreasing radially from the center of the surface 48 towards the outer contour 50. Such an intensity distribution causes the first light beam 18 to be reflected by the particle 12 at different intensities along the vertical axis 40 of the oval 38. By measuring the intensity of the reflected first light beam 18, a particle characteristic can be determined with high accuracy. If the particle characteristic to be determined is a particle position, it is advantageous to consider that the intensity of the reflected first light beam 18 can vary depending on the particle size. Therefore, the embodiment of the intensity distribution shown in Fig. 3 provides that the beam shaping optics 26 generate a location-dependent polarization distribution, which is indicated in Fig. 3 by arrows 52, 54, 56, 58, and 60.Along the vertical axis 40, a first polarization 52 and a second polarization 54 exist, spaced apart from each other along the vertical axis 40 of the oval 38, with their polarization directions forming an angle of 180 degrees to each other. In the region of the surface center 48, a third polarization 56 exists, its polarization direction forming an angle of 90 degrees to the polarization directions of the first and second polarizations 52 and 54, respectively. Between the first polarization 52 and the third polarization 56, a fourth polarization 58 exists, its polarization direction forming an angle of 45 degrees to the polarization direction of the third polarization 56. Between the second polarization 54 and the third polarization 56, a fifth polarization 60 exists, which also forms an angle of 45 degrees to the third polarization 56.Contrary to the representation shown, the location-dependent polarization distribution along the vertical axis 40 is continuous and includes the discretely shown polarizations 52, 54, 56, 58 and 60. The rotational order of the polarization of the first light ray 18 is 1. The value 1 of the rotational order indicates that the polarization direction rotates once by 180° along the vertical axis 40. The first light beam 18 and the second light beam 20 have the same polarization properties. Therefore, Fig. 3 also applies accordingly to the second light beam. 20. In an alternative embodiment not shown, the two light rays 18, 20 can differ in their rotational order. Fig. 1 shows that particle 12, as it moves along the direction of motion 28, passes through the first light ray 18. When particle 12 passes through the first light ray 18, the first light ray 18 is reflected and / or scattered by the particle 12. The reflected first light ray 18 has a polarization that depends on the position of particle 12 along the Y-axis. Considering the polarization of the reflected first light ray 18 allows for the determination of a unique position of particle 12 along the Y-axis. Fig. 4 shows a diagram with location-dependent intensity profiles 62, 64, 66 and 68 of the first light ray 18 reflected and / or scattered by the particle 12. A corresponding diagram applies to the location-dependent intensity profiles of the second light ray 20 reflected and / or scattered by the particle 12. The intensity profiles 62, 64, 66, 68 each describe the polarization-dependent intensity of the first light ray 18 reflected and / or scattered by the particle 12 along the vertical axis 40 of the oval 38. The first intensity profile 62 describes the location-dependent intensity of the first light ray 18 reflected and / or scattered by the particle 12 with the first polarization 52 according to Fig. 3. The second intensity profile 64 corresponds to the location-dependent intensity of the first light ray 18 reflected and / or scattered by the particle 12 with the second polarization 54 and the third polarization 56 according to Fig. 3. The polarization directions of the first and second polarizations 52, 54 have an angle of 180 degrees, so that a polarization filter is transparent to light with the first and second polarizations 52, 54.The third intensity profile 66 corresponds to the location-dependent intensity of the first light ray 18 reflected and / or scattered by the particle 12 with the fourth polarization 58 according to Fig. 3. The fourth intensity profile 68 corresponds to the location-dependent intensity of the first light ray 18 reflected and / or scattered by the particle 12 with the fifth polarization 60 according to Fig. 3. If the first light ray 18 strikes the particle 12, the first light ray 18 reflected and / or scattered by the particle 12 exhibits a plurality of polarization-dependent intensities which, depending on the Y-position of the particle 12, correspond to the intensity profiles 62, 64, 66, 68 according to Fig. 4. If, for example, the particle 12 is located at a height of 0 pm along the Y-axis of Fig. 3, the light ray reflected by the particle 12 exhibits The reflected and / or scattered first light ray 18 exhibits a dominant intensity component corresponding to the first intensity profile 62 and the corresponding third polarization 56. Simultaneously, the first light ray 18 reflected and / or scattered by the particle 12 in this example exhibits less pronounced intensity components corresponding to the intensity profiles 66, 68 and the corresponding fourth polarization 58 or fifth polarization 60. In other words, at the Y-position of 0 pm, the third polarization 56 according to Fig. 3 predominates, which, however, can be represented by a linear superposition of equal parts of the fourth and fifth polarizations 58, 60 according to Fig. 3. The device 10 has a detector assembly 69, which includes a first detector module 70 and a second detector module 76. The first detector module 70 is designed to detect the first light beam 18 reflected and / or scattered by the particle 12 with polarization resolution and to output a polarization-resolved intensity signal. For this purpose, the first detector module 70 has a power detector 72 in the form of a photodiode for detecting an intensity of the first light beam 18 reflected and / or scattered by the particle 12. The first detector module 70 has an analysis optic 74. The analysis optic 74 has a collector optic by means of which the first light beam 18, reflected and / or scattered by the particle 12, is focused and directed onto the power detector 72. The collector optic can be configured as a lens or as a mirror. The analysis optics 74 has one polarizer and another polarizer. Using the polarizers, the first detector module 70 can detect the first light ray 18 reflected and / or scattered by the particle 12 with polarization resolution. In other words, the first detector module 70 can determine the intensity of an X-polarization that the first light ray 18 reflected and / or scattered by the particle 12 exhibits in a direction parallel to the X-axis, the intensity of a Y-polarization that the first light ray 18 reflected and / or scattered by the particle 12 exhibits in a direction parallel to the Y-axis, the intensity of an XY-polarization that the first light ray 18 reflected and / or scattered by the particle 12 exhibits in a direction diagonal to the X-axis and Y-axis, and the intensity of a YX-polarization that the first light ray 18 reflected and / or scattered by the particle 12 exhibits and / or scattered first light ray 18 in the direction antidiagonal to the X-axis and Y-axis, detect.The polarization-resolved intensity signal of the first detector module 70 has a first partial signal that is representative of the intensity of the first light ray 18 reflected and / or scattered by the particle 12 with polarization direction parallel to the X-axis, a second partial signal that is representative of the intensity of the first light ray 18 reflected and / or scattered by the particle 12 with polarization direction parallel to the Y-axis, a third partial signal that is representative of the intensity of the first light ray 18 reflected and / or scattered by the particle 12 with polarization direction diagonal to the X-axis and Y-axis, and a fourth partial signal that is representative of the intensity of the first light ray 18 reflected and / or scattered by the particle 12 with polarization direction antidiagonal to the X-axis and Y-axis. The power detector 72 detects the intensity of the first light beam 18 reflected and / or scattered by the particle 12 and outputs the polarization-resolved intensity signal in the form of an electrical signal. Fig. 1 shows that particle 12, as it moves along the direction of motion 28, passes through the second light beam 20. When particle 12 passes through the second light beam 20, the second light beam 20 is reflected and / or scattered by particle 12. The reflected second light beam 20 has a polarization that can depend on the position of particle 12 along the Y-axis. Considering the polarization of the reflected second light beam 20 allows for the determination of a unique position of particle 12 along the Y-axis. The second detector module 76 is designed to detect the second light beam 20 reflected and / or scattered by the particle 12 with polarization resolution and to output a polarization-resolved intensity signal. The second detector module 76 has a power detector 78 in the form of a photodiode for detecting an intensity of the second light beam 20 reflected and / or scattered by the particle 12. The second detector module 76 has an analysis optic 80. The analysis optic 80 has a collector optic by means of which the second light beam 20, reflected and / or scattered by the particle 12, is focused and directed onto the power detector 78. The collector optic can be configured as a lens or as a mirror. The analysis optics 80 has one polarizer and another polarizer. Using the polarizers, the second detector module 76 can detect the second light beam 20 reflected and / or scattered by the particle 12 with polarization resolution.In other words, the second detector module 76 can detect the intensity of an X-polarization that the second light beam 20 reflected and / or scattered by the particle 12 exhibits in a direction parallel to the X-axis, the intensity of a Y-polarization that the second light beam 20 reflected and / or scattered by the particle 12 exhibits in a direction parallel to the Y-axis, the intensity of an XY-polarization that the second light beam 20 reflected and / or scattered by the particle 12 exhibits in a direction diagonal to the X-axis and Y-axis, and the intensity of a YX-polarization that the second light beam 20 reflected and / or scattered by the particle 12 exhibits in an antidiagonal direction to the X-axis and Y-axis.The polarization-resolved intensity signal of the second detector module 76 has a first partial signal that is representative of the intensity of the second light beam 20 reflected and / or scattered by the particle 12 with polarization direction parallel to the X-axis, a second partial signal that is representative of the intensity of the second light beam 20 reflected and / or scattered by the particle 12 with polarization direction parallel to the Y-axis, a third partial signal that is representative of the intensity of the second light beam 20 reflected and / or scattered by the particle 12 with polarization direction diagonal to the X-axis and Y-axis, and a fourth partial signal that is representative of the intensity of the second light beam 20 reflected and / or scattered by the particle 12 with polarization direction antidiagonal to the X-axis and Y-axis. The power detector 78 detects the intensity of the second light beam 20 reflected and / or scattered by the particle 12 and outputs the polarization-resolved intensity signal in the form of an electrical signal. The device 10 has an evaluation unit 82. The evaluation unit 82 is an electronic computing unit in the form of a computer. A computer can be understood as a programmable, integrated circuit. The evaluation unit 82 is configured to determine the particle characteristics as a function of the intensity signal of the first detector module 70 and the intensity signal of the second detector module 76. The evaluation unit 82 assigns the polarization-resolved intensities of the first detector module 70 and the second detector module 76 to a unique position of the particle 12 along the Y-axis, for example, using a mathematical model or a table. The evaluation unit 82 is designed to detect a duration between the intensity signal of the first detector module 70 and the intensity signal of the second detector module 76 and to determine the particle characteristic based on the duration. If the velocity of particle 12, whose direction of motion is parallel to the X-axis, is known, then the evaluation unit 82 can determine a distance 84, parallel to the X-axis, between the first light beam 18 and the second light beam 20, based on the duration between the intensity signal of the first detector module 70 and the intensity signal of the second detector module 76. Fig. 2 shows that the distance 84 between the two light beams 18, 20 depends on a position in the Z-direction. The evaluation unit 82 assigns the determined distance 84 to a unique position of particle 12 along the Z-axis, for example, using a mathematical model or a table. If the position of particle 12 along the Z-axis is known and particle 12 moves at a constant speed parallel to the X-axis, then the evaluation unit 82 can determine the speed of particle 12 based on the position along the Z-axis and the time between the intensity signal of the first detector module 70 and the intensity signal of the second detector module 76. In an embodiment not shown, the wavelengths of the two light beams 18, 20 differ from each other. The two detector modules 70, 76 each have a wavelength filter. The wavelength filter of the first detector module 70 serves to separate the first light beam 18, reflected and / or scattered by the particle 12, from the second light beam 20, also reflected and / or scattered by the particle 12. The wavelength filter of the first detector module 70 prevents the second light beam 20, reflected and / or scattered by the particle 12, from reaching the power detector 72 of the first detector module 70. The wavelength filter of the second detector module 76 serves to separate the first light beam 18, reflected and / or scattered by the particle 12, from the second light beam 20, also reflected and / or scattered by the particle 12.The wavelength filter of the second detector module 76 prevents the first light beam 18 reflected and / or scattered by the particle 12 from hitting the power detector 78 of the second detector module 76. Figure 5 shows a further embodiment of the first light beam 18 and the second light beam 20 of Figures 1 to 4, wherein identical and functionally equivalent Elements with the same reference numerals are used, and in this respect reference can be made to the above explanations regarding the embodiment of Figs. 1 to 4, so that essentially only the existing differences are discussed. Fig. 5 a) shows an intensity distribution of the first polarization 52 of the first light beam 18 in a YZ plane spanned by the Y and Z axes. Fig. 5 b) shows an intensity distribution of the third polarization 56 of the first light beam 18 in the YZ plane spanned by the Y and Z axes. Fig. 5 c) shows an intensity distribution of the fourth polarization 58 of the first light beam 18 in the YZ plane spanned by the Y and Z axes. Fig. 5 d) shows an intensity distribution of the fifth polarization 60 of the first light beam 18 in the YZ plane spanned by the Y and Z axes. Figures 5 a) to d) show that the spatially dependent polarization distribution of the first light ray 18 has a rotational order along the vertical axis 40 of the oval 38. In the embodiment shown in Figures 5 a) to d), the rotational order of the first light ray 18 is 6. Fig. 5e) shows an intensity distribution of the first polarization of the second light beam 20 in the YZ plane spanned by the Y and Z axes. Fig. 5f) shows an intensity distribution of the third polarization of the second light beam 20 in the YZ plane spanned by the Y and Z axes. Fig. 5g) shows an intensity distribution of the fourth polarization of the second light beam 20 in the YZ plane spanned by the Y and Z axes. Fig. 5h) shows an intensity distribution of the fifth polarization of the second light beam 20 in the YZ plane spanned by the Y and Z axes. Figures 5 e) to h) show that the spatially dependent polarization distribution of the second light beam 20 has a rotational order along the vertical axis of the oval. In the embodiment shown in Figures 5 e) to h), the rotational order of the second light beam 20 is 5. Because the first light beam 18 has a rotational order of 6 and the second light beam 20 has a rotational order of 5, a high resolution can be achieved. It is conceivable that the beam axis 30 of the first light beam 18 and the beam axis 32 of the second light beam 20 are arranged in the same YZ plane. In this case, the oval angle of the first light beam 18 and the oval angle of the second light beam 20 can each be approximately 0°, in particular 0°. It is also conceivable that the beam axis 30 of the first light beam 18 and the beam axis 32 of the second light beam 20 are each arranged in a YZ plane, with the two YZ planes running parallel and offset from each other. This allows the two beam axes 30 and 32 to be skew to each other. The two beam axes 30 and 32 can be spaced apart. The two beam axes 30 and 32 cannot intersect. Therefore, by comparing the eight signal components (2x4) and performing a coordinate transformation, the transverse position can be measured two-dimensionally. It is also conceivable that the two light beams 18, 20 travel in the same XY plane. The wavelengths of the first light beam 18 and the second light beam 20 can be different. In this way, the signal components of the two light beams can be separated. In another embodiment, the two light beams 18, 20 can have the same rotational order m=1. For example, a horizontally polarized light signal from the first light beam would then mean that the particle is located in the center of the first light beam. A diagonally polarized light signal from the second light beam would then mean that the particle is located some distance from its center. As a result, the particle can only be located where the two light beams 18, 20, each with constant polarization (horizontal, diagonal), intersect. Fig. 6 shows light rays of a further embodiment of the device 10 of Figs. 1 to 4, wherein identical and functionally equivalent elements are given the same reference numerals and in this respect reference can be made to the above descriptions of the embodiment of Figs. 1 to 4, so that essentially only the existing differences are discussed. The light source 16 is configured to generate a third light beam 86 that passes through the measurement volume 14. The detector assembly 69 has a third detector module configured to detect the third light beam 86 reflected and / or scattered by the particle 12 and to output an intensity signal. The third detector module is constructed analogously to the first detector module 70 and the second detector module 76. The beam axis 30 of the first light beam 18 runs parallel to the Z-axis. The third light beam 86 propagates within the measuring volume 14 along a beam axis 88. The beam axis 88 of the third light beam 86 runs parallel to and offset from the beam axis 30. of the first light ray 18. The ray axis 32 of the second light ray 20 and the ray axis 88 of the third light ray 86 intersect at a point of intersection 92. The ray axes 30, 32, 88 of the light rays 18, 20, 86 are arranged in a " " shape. If particle 12 passes through the measuring volume 14 at a constant speed, it passes through the first light beam 18, the second light beam 20, and the third light beam 86. The evaluation unit 82 records a first duration between the polarization-resolved intensity signal of the first detector module 70 and the polarization-resolved intensity signal of the second detector module 76, and a second duration between the polarization-resolved intensity signal of the second detector module 76 and the polarization-resolved intensity signal of the third detector module. Based on these polarization-resolved intensity signals, the evaluation unit 82 determines the position of particle 12 along the z-axis. Specifically, based on the ratio of the first duration to the second duration, the evaluation unit 82 determines the position of particle 12 along the z-axis.Evaluation unit 82 determines the velocity of particle 12 based on the absolute values ​​of the first and second durations. Evaluation unit 82 determines the position of particle 12 in the direction of the x-axis based on the absolute values ​​of the polarization-resolved intensity signals.

Claims

Patent claims 1. Device (10) for measuring a particle characteristic of a particle (12) located in a measuring volume (14) of the device (10), comprising: a light source (16) for generating a first light beam (18) and a second light beam (20), each passing through the measuring volume (14), a detector device (69) configured to detect the first light beam (18) and the second light beam (20) reflected and / or scattered by the particle (12) and to output an intensity signal, and an evaluation unit (82) configured to determine the particle characteristic as a function of the intensity signal of the detector device (69), wherein the first light beam (18) and the second light beam (20) propagate in the measuring volume (14) along a beam axis (30, 32),wherein the ray axis (30) of the first light ray (18) and the ray axis (32) of the second light ray (20) define a propagation angle (34) between them which is not equal to 0°.

2. Device (10) according to claim 1, wherein the light source (16) is configured to generate a third light beam (86) passing through the measuring volume (14), wherein the detector device (69) is configured to detect the third light beam (86) reflected and / or scattered by the particle (12), wherein the third light beam (86) propagates in the measuring volume (14) along a beam axis (88).

3. Device (10) according to one of the preceding claims, wherein the beam axis (30) of the first light beam (18) and the beam axis (32) of the second light beam (20) intersect at a point of intersection (36), and / or wherein the beam axis (32) of the second light beam (20) and the beam axis (88) of the third light beam (86) intersect at a point of intersection (92).

4. Device (10) according to one of the preceding claims, wherein the wavelengths of the light rays (18, 20, 86) differ from each other.

5. Device (10) according to one of the preceding claims, wherein each light ray (18, 20, 86) of the light source (16) has an intensity profile in a cross-section which is constant along an outer contour (50) of an oval (38) and is maximal at at least one point within the oval (38), in particular at a surface center of the oval (38), wherein the light source (16) has a beam shaping optic (26) configured to adjust a location-dependent polarization distribution for each light ray (18, 20, 86) of the light source (16) in a cross-section such that the light ray (18, 20, 86) has at least one first polarization (52) and one second polarization (54) with different polarization directions along a vertical axis (40) of the oval (38), wherein the detector device (69) is configured to detect the respective reflected and / or scattered light reflected and / or scattered by the particle (12). Light beam (18, 20,86) to detect with polarization resolution and to output a polarization-resolved intensity signal, wherein the evaluation unit (82) is configured to determine the particle characteristics as a function of the polarization-resolved intensity signal of the detector device (70).

6. Device (10) according to claim 5, wherein there is an angle of 90 degrees or 180 degrees between the polarization directions of the first polarization (52) and the second polarization (54).

7. Device (10) according to claim 5 or 6, wherein the location-dependent polarization distribution has a continuous change in the polarization direction along the vertical axis (40) of the oval (38).

8. Device (10) according to any one of the preceding claims 5 to 7, wherein the location-dependent polarization distribution has a rotational order along the vertical axis (40) of the oval (38).

9. Device (10) according to claim 8, wherein the rotational order of the first light beam (18) and the rotational assignment of the second light beam (20) differ from each other, and / or wherein the rotation order of the second light ray (20) and the rotation assignment of the third light ray (86) differ from each other, and / or wherein the rotation order of the first light ray (18) and the rotation assignment of the third light ray (86) differ from each other.

10. Device (10) according to any one of the preceding claims 5 to 9, wherein the beam axis (30) of the first light beam (18) and the beam axis (32) of the second light beam (20) define a propagation plane, wherein each vertical axis (40) of the oval (38) of a light beam (18, 20, 86) is aligned with an oval angle to the propagation plane.

11. Device (10) according to claim 10, wherein each oval angle is approximately 90°, in particular 90°.

12. Device (10) according to claim 10, wherein each oval angle is approximately 0°, in particular 0°.

13. Method for measuring a particle characteristic of a particle (12) located in a measuring volume (14), the method comprising the steps: Generating a first light ray (18) and a second light ray (20), each passing through the measuring volume (14), wherein the first light ray (18) and the second light ray (20) propagate in the measuring volume (14) along a ray axis (30, 32), and wherein the ray axis (30) of the first light ray (18) and the ray axis (32) of the second light ray (20) define a propagation angle (34) between them which is not equal to 0°, Detecting the first light ray (18) reflected and / or scattered by the particle (12) and outputting an intensity signal, Detecting the second light beam (20) reflected and / or scattered by the particle (12) and outputting an intensity signal, and Determining the particle characteristics based on the intensity signal of the first light ray (18) reflected and / or scattered by the particle (12) and the intensity signal of the second light ray (20) reflected and / or scattered by the particle (12).

Images