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

Abstract

Device (10) for measuring the particle characteristics of a particle (12) located in a measuring volume (14) of the device (10). The device (10) has a light source (16) for generating a light beam (18) that passes through the measuring volume (14) and whose polarization in a cross-sectional plane (30) can be described by a spatially dependent Stokes vector that has a spatially dependent S3 Stokes parameter. Furthermore, the device (10) has a detector unit (34) configured to measure an S3 Stokes parameter of the light beam (18) reflected and / or scattered by the particle (12) and to output a measurement signal as a function of the measured S3 Stokes parameter, and an evaluation unit (82) configured to determine the particle characteristics as a function of the measurement signal from the detector unit (34).

Description

[0001] 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.

[0002] 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.

[0003] 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.

[0004] The invention is based on the objective of providing a device and a method that each enable a fast and precise measurement of a particle characteristic.

[0005] The invention solves this problem by providing a device with the features of claim 1 and a method with the features of claim 11. Advantageous further developments and / or embodiments of the invention are described in the dependent claims.

[0006] A device according to the invention is designed for measuring the particle characteristics of a particle located in a measuring volume of the device. The device comprises a light source, a detector, and an evaluation unit. The light source is designed to generate a light beam that passes through the measuring volume and whose polarization within the measuring volume can be described in a cross-sectional plane using a spatially dependent Stokes vector that has a spatially dependent S3 Stokes parameter. The detector is designed to measure an S3 Stokes parameter of the light beam reflected and / or scattered by the particle and to output a measurement signal as a function of the measured S3 Stokes parameter. The evaluation unit is designed to determine the particle characteristics as a function of the measurement signal from the detector.

[0007] Typically, the S3-Stokes parameter can be measured relatively quickly and precisely using a light beam. Therefore, particle characteristics can be determined particularly quickly and precisely by measuring the S3-Stokes parameter. For example, the S3-Stokes parameter can be measured using photodiodes in the detector assembly, which typically have relatively fast response times. Consequently, particle characteristics can be determined more quickly using this device than using a device whose detector assembly includes a camera for particle detection.

[0008] Another advantage of the device is that the detector assembly for measuring the S3-Stokes parameter can be implemented with a relatively simple and compact design. In particular, the S3-Stokes parameter can be reliably measured with a relatively stable setup, making the measurement of the S3-Stokes parameter using this detector assembly especially stable and reliable.

[0009] Another aspect of the device is that the particle characteristics can be detected in the two-dimensional cross-sectional plane using the location-dependent S3-Stokes parameter, which is why the device can act as a two-dimensional camera for determining the particle characteristics.

[0010] The particle can have a diameter that is at least 5 times smaller, in particular 10 times smaller, preferably 20, 100, or 1000 times smaller, than the diameter of the light beam within the measuring volume. For smaller particle diameters, the power of the light beam can be higher.

[0011] 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. The particle can be a solid suspended in a gas or a liquid.

[0012] 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 disc 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.

[0013] Due to the high resolution and rapid particle detection capabilities of the device, it may be particularly suitable for detecting contamination on large surfaces in a relatively short time.

[0014] The particle characteristic can be a position, a velocity, an acceleration, and / or a size of the particle. In particular, the device can be designed such that the particle position can be determined with a spatial resolution of 5 micrometers to 0.1 micrometers, preferably from 3 micrometers to 1 micrometer, most preferably 1 micrometer.

[0015] 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 a beam axis of the light beam. In particular, the measuring volume can extend along a light distribution of the light beam. The measuring volume can be bounded by the light beam, especially by the light distribution of the light beam.

[0016] The light beam can propagate along a direction of propagation. The cross-sectional plane can be oriented orthogonally to the direction of propagation. The cross-sectional plane can intersect the measurement volume. Therefore, at least a portion of the cross-sectional plane can lie within the measurement volume.

[0017] The light source can include at least a laser with a laser diode, a superluminescent diode, a halogen lamp or a comparable optical beam source for generating the light beam.

[0018] The light beam can be a laser beam. It can have a tophat intensity distribution, which can advantageously improve the signal-to-noise ratio. Alternatively, the light beam can have a Gaussian intensity distribution. This type of intensity distribution is particularly easy to generate, and the measurement volume in the direction of light beam propagation can be larger.

[0019] The light beam can be polarized. The light beam can have a degree of polarization of at least 0.9, in particular 0.95, at every point in the cross-sectional plane. The degree of polarization can satisfy the following condition: DOP=S12+S22+S32S0, where DOP describes the degree of polarization, S0 the S0 Stokes parameter, S1 the S1 Stokes parameter, S2 the S2 Stokes parameter and S3 the S3 Stokes parameter.

[0020] The S0 Stokes parameter can specify the intensity. The S1 Stokes parameter can specify the difference in intensity between horizontally and vertically linearly polarized light. The S2 Stokes parameter can specify the difference in intensity between ±45° linearly polarized light. The S3 Stokes parameter can specify the difference in intensity between right- and left-circularly polarized light.

[0021] The S0 Stokes parameter, the S1 Stokes parameter, the S2 Stokes parameter and the S3 Stokes parameter can together form the Stokes vector.

[0022] The polarization can exhibit a location-dependent polarization state in the cross-sectional plane. In particular, the polarization can exhibit a polarization state that changes in the cross-sectional plane.

[0023] A spatially dependent Stokes vector can be understood as one in which at least one value of the Stokes vector, in particular a value of one of its parameters, is spatially dependent, specifically varying from place to place. In other words, the Stokes vector can have different values ​​at different points in the cross-sectional plane. The values ​​of the Stokes vector can depend on a position in the cross-sectional plane.

[0024] A location-dependent S3-Stokes parameter can be understood as one where the value of the S3-Stokes parameter is location-dependent, specifically, varies geographically. In other words, the S3-Stokes parameter can have different values ​​at different points in the cross-sectional plane. The value of the S3-Stokes parameter can depend on a position within the cross-sectional plane.

[0025] The amplitude of the measurement signal can depend on the detected S3-Stokes parameter. The magnitude of the detector's measurement signal can be representative of the S3-Stokes parameter of the light beam reflected and / or scattered by the particle.

[0026] 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 measurement signal.

[0027] Because the evaluation unit is designed to determine the particle characteristics as a function of the measurement signal from the detector device, the evaluation unit can determine the particle characteristics as a function of the S3 Stokes parameter.

[0028] The evaluation unit can be designed to record the temporal evolution of the measurement signal and to determine the particle characteristics based on the temporal evolution.

[0029] 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 measurement signal from the detector device and the particle characteristics, in particular between the temporal evolution of the measurement signal from 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 measurement signal, in particular the temporal evolution of the measurement signal.

[0030] Preferably, the spatially dependent S3-Stokes parameter in the cross-sectional plane can be known, and in particular predefined, to the evaluation unit. For example, the spatially dependent S3-Stokes parameter can be implemented, and in particular stored, in the model, the table, or as a characteristic curve in the evaluation unit. Based on the measurement signal, the evaluation unit can determine the measured S3-Stokes parameter and determine the particle characteristics by comparing the measured S3-Stokes parameter with the predefined spatially dependent S3-Stokes parameter. In particular, the comparison can determine a point in the cross-sectional plane where the particle is located.

[0031] The device can have an X-axis, a Y-axis, and a Z-axis, each orthogonal to the others. The X-axis can extend in an X-direction, the Y-axis in a Y-direction, and the Z-axis in a Z-direction. The light beam can propagate parallel to the Z-axis, particularly in the Z-direction. The cross-sectional plane can be a plane aligned parallel to the X- and Y-directions.

[0032] For example, a particle can move within the measurement volume in the cross-sectional plane. During this movement, the particle may pass through the light beam. While passing through the light beam, the particle may be irradiated by it. The particle may reflect and / or scatter a portion of the light beam. The portion of the light beam reflected and / or scattered by the particle can be understood as the portion of the light beam that is reflected and / or scattered by the particle. The detector can measure the S3-Stokes parameter of the light beam reflected and / or scattered by the particle. Based on the measured S3-Stokes parameter, the evaluation unit can determine the particle's position within the measurement volume. The particle's position within the measurement volume can be considered the particle's characteristic.

[0033] Additionally, the detector can measure another S3-Stokes parameter of the light beam reflected and / or scattered by the particle after a predetermined time. The evaluation unit can be configured to determine the particle's direction of motion within the measurement volume as a particle characteristic, based on the S3-Stokes parameter and the additional S3-Stokes parameter. The evaluation unit can also be configured to determine the particle's velocity within the measurement volume as a particle characteristic, based on the S3-Stokes parameter, the additional S3-Stokes parameter, and the time interval. The particle's direction of motion and / or its velocity within the measurement volume can constitute the particle characteristic.

[0034] Additionally or alternatively, the detector can measure a supplementary S3-Stokes parameter of the light beam reflected and / or scattered by the particle after a further time interval. The evaluation unit can be configured to determine, based on the S3-Stokes parameter, the additional S3-Stokes parameter, the supplementary S3-Stokes parameter, the time interval, and the further time interval, an acceleration, a trajectory, a change in velocity, and / or a change in the direction of motion of the particle within the measurement volume. The acceleration, trajectory, change in velocity, and / or change in the direction of motion of the particle within the measurement volume can constitute the particle characteristics.

[0035] Another aspect of the device is that, compared to existing camera-based devices for determining particle characteristics, it performs the determination of particle characteristics at a higher speed, with greater bandwidth, and in near real-time. In particular, the device can determine particle characteristics faster and more precisely than devices that use shadow image measurement techniques.

[0036] Another aspect of the device may be that the determination of the particle characteristics can be carried out faster than a determination of the particle characteristics with a device that has a high-speed camera.

[0037] In a further development of the device, the light source comprises a light-generating device, for example in the form of a resonator, and a polarization optics device. The light-generating device is designed to generate the light beam. The polarization optics device is designed to adjust the polarization of the light beam such that the position-dependent Stokes vector has the position-dependent S3 Stokes parameter. Advantageously, the polarization of the light beam can be adjusted particularly easily and robustly using the polarization optics device.

[0038] The light-generating device can produce a linearly polarized light beam. The polarization optics device can effect a local or spatial change in polarization within the cross-sectional plane.

[0039] If the light-generating device is designed as a resonator, the polarizing optics device can be arranged downstream of the resonator in the direction of light beam propagation or integrated into the resonator. If the polarizing optics device is integrated into the resonator, it can be configured to generate losses in the resonator such that the resonator generates the light beam with a polarization that can be described in the cross-sectional plane using the position-dependent Stokes vector.

[0040] In a further development of the device, the polarization optics assembly includes at least one phase-shifting element that causes a location-dependent change in the polarization of the light beam. Phase-shifting elements can enable a relatively simple and cost-effective location-dependent change in the polarization of the light beam.

[0041] The phase-shifting element can be plate-shaped. The light beam can transmit, in particular pass through, the phase-shifting element to change its polarization.

[0042] The phase-shifting element can exhibit a birefringence that varies in magnitude, particularly with location. This location-dependent birefringence allows the phase-shifting element to cause a location-dependent change in the polarization of the light beam. Location-dependent birefringence means that the strength or degree of birefringence is dependent on the location. In other words, the difference in refractive index between a fast axis and a slow axis can have a location-dependent value. A fast axis means that light polarized parallel to the fast axis passes through the phase-shifting element faster than light polarized orthogonal to the fast axis.A slow axis can be understood to mean that light polarized parallel to the slow axis passes through the phase-shifting element more slowly than light polarized orthogonally to the slow axis.

[0043] Alternatively or additionally, the birefringence of the phase-shifting element can exhibit a location-dependent orientation. This location-dependent birefringence can locally, and in particular locally, cause a phase shift between two mutually orthogonally aligned polarization components of the light beam. Specifically, the phase-shifting element can locally, and in particular locally, act as a retardation plate, especially a λ / 4 plate or a λ / 2 plate. The orientation of the location-dependent birefringence can be locally described by an optical axis. A phase shift between a polarization component aligned parallel to the optical axis and a polarization component aligned perpendicular to the optical axis can be λ / 4 or λ / 2, where λ is the wavelength of the light beam.

[0044] The orientation of the birefringence of the phase-shifting element can be location-dependent, and in particular, locally variable. Specifically, the orientation of the birefringence of the phase-shifting element can be locally continuously variable. For example, the phase-shifting element can extend in the X-direction and the Y-direction, with the orientation of the birefringence changing continuously in the X-direction and / or the Y-direction.

[0045] In a further development of the device, the light source is configured to generate the light beam in such a way that the position-dependent S3-Stokes parameter changes continuously along an X-direction and / or along a Y-direction orthogonal to the X-direction. Advantageously, by continuously changing the S3-Stokes parameter, jumps in the change of the S3-Stokes parameter can be avoided, thereby achieving high resolution.

[0046] The X-direction and the Y-direction can span, and in particular define, the cross-sectional plane.

[0047] In a further development of the device, the spatially dependent Stokes vector includes a spatially dependent S1 Stokes parameter and a spatially dependent S2 Stokes parameter. The detector is configured to measure an S1 Stokes parameter and an S2 Stokes parameter of the light beam reflected and / or scattered by the particle and to output the measurement signal as a function of the measured S1 Stokes parameter and the measured S2 Stokes parameter. Advantageously, this allows the particle characteristics to be determined more precisely. In particular, the resolution and precision can be improved due to the additional information provided by the S1 Stokes parameter and the S2 Stokes parameter.

[0048] Because the evaluation unit is designed to determine the particle characteristics as a function of the measurement signal from the detector device, the evaluation unit can determine the particle characteristics based on the S1 Stokes parameter and the S2 Stokes parameter.

[0049] In a further development of the device, the light source is configured to generate the light beam such that the position-dependent S1-Stokes parameter and the position-dependent S2-Stokes parameter of the light beam in the cross-sectional plane change continuously along the X-direction and / or along the Y-direction. Advantageously, by continuously changing the S1-Stokes parameter and the S2-Stokes parameter, abrupt changes in the S1-Stokes parameter and the S2-Stokes parameter can be avoided, thereby achieving high resolution.

[0050] In a further development of the device, the light source is configured to generate an additional light beam that passes through the measurement volume and whose polarization in a cross-sectional plane can be described by a spatially dependent Stokes vector, which has a spatially dependent S3 Stokes parameter. The detector unit is configured to measure an additional S3 Stokes parameter of the further light beam reflected and / or scattered by the particle and to output a further measurement signal as a function of the measured S3 Stokes parameter. The evaluation unit is configured to determine the particle characteristics as a function of the additional measurement signal from the detector unit. Advantageously, this allows the particle characteristics to be determined with increased precision.

[0051] For example, the particle characteristic can be determined using the light beam and confirmed with a second light beam. Alternatively, the particle characteristic can be determined by averaging a first particle characteristic determined using the light beam and a second particle characteristic determined using the second light beam. In particular, if the particle characteristic is a velocity, the velocity can be determined by averaging a first velocity determined using the light beam and a second velocity determined using the second light beam. Advantageously, this allows for a particularly precise determination of the particle characteristic.

[0052] In a further development of the device, the spatially dependent Stokes vector of the secondary light beam has a spatially dependent S1 Stokes parameter and a spatially dependent S2 Stokes parameter. The detector is configured to measure an S1 Stokes parameter and an S2 Stokes parameter of the secondary light beam reflected and / or scattered by the particle and to output the measurement signal as a function of the measured S1 Stokes parameter and the measured S2 Stokes parameter. Advantageously, this allows the particle characteristics to be determined more precisely. In particular, the resolution and precision can be improved due to the additional information provided by the S1 Stokes parameter and the S2 Stokes parameter of the secondary light beam.

[0053] Because the evaluation unit is designed to determine the particle characteristics as a function of the measurement signal from the detector device, the evaluation unit can determine the particle characteristics based on the S1-Stokes parameter and the S2-Stokes parameter of the further light beam.

[0054] The S1-Stokes parameter distribution of the light beam and the S1-Stokes parameter distribution of the second light beam can be the same or different. The S2-Stokes parameter distribution of the light beam and the S2-Stokes parameter distribution of the second light beam can also be the same or different.

[0055] In a further development of the device, the light beam and the subsequent light beam differ in their wavelength. Additionally or alternatively, the distribution of the spatially dependent S3-Stokes parameter values ​​of the light beam and the distribution of the spatially dependent S3-Stokes parameter values ​​of the subsequent light beam differ from each other. Advantageously, this allows the detector to measure the S3-Stokes parameter of the light beam reflected and / or scattered by the particle and the subsequent S3-Stokes parameter of the subsequent light beam independently of each other. In particular, the influence of the subsequent light beam on the measurement of the S3-Stokes parameter of the light beam reflected and / or scattered by the particle can be reduced or completely avoided.

[0056] The wavelength difference between the wavelength of the light beam and the wavelength of the other light beam can be in the range of 10 nm (nanometers) to 50 nm or in the range of 150 nm to 300 nm. In particular, the wavelength of the light beam can be 1550 nm and the wavelength of the other light beam 1310 nm.

[0057] The distribution of the S3-Stokes parameter values ​​and the distribution of the S3-Stokes parameter values ​​of the secondary light ray can differ, in particular, only in their signs and be equal in their magnitudes. This can result in a different direction of rotation of the polarization of the light ray and a different direction of rotation of the polarization of the secondary light ray. For example, the orientation and size of local polarization ellipses of the polarization of the light ray and the secondary light ray can be the same, and the directions of rotation of the polarization of the light ray and the secondary light ray can differ.

[0058] In a further development of the device, the position-dependent S3-Stokes parameter of the light beam, particularly along the X-direction and / or the Y-direction, exhibits a periodicity with a value greater than or equal to 1, preferably 2 or 3. Additionally or alternatively, the position-dependent S3-Stokes parameter of the further light beam, particularly along the X-direction and / or the Y-direction, exhibits a periodicity with a value greater than or equal to 1, preferably 2 or 3. Advantageously, this allows for an increase in the resolution of the device for determining the particle characteristics.

[0059] In particular, a very high periodicity value can be advantageous. This allows the polarization state to change more rapidly in the cross-sectional plane along the X and / or Y direction than with a lower periodicity value, thereby increasing the resolution of the device.

[0060] Periodicity can indicate how often a polarization state repeats itself in the X-direction and / or in the Y-direction.

[0061] For example, a value of the S3-Stokes parameter of the light beam in the cross-sectional plane along the X-direction and / or Y-direction can repeat with a periodicity of, for example, 3. This allows the light beam to exhibit the same polarization state three times at different locations in the cross-sectional plane along the X-direction and / or Y-direction.

[0062] For example, a value of the S3-Stokes parameter of the other light ray in the cross-sectional plane along the X-direction and / or Y-direction can repeat with a periodicity of, for example, 3. This allows the other light ray to exhibit the same polarization state three times at different locations in the cross-sectional plane along the X-direction and / or Y-direction.

[0063] The periodicity can have a value in the range of 1 to 25, preferably 1 to 5.

[0064] The value of the periodicity of the light beam can differ from the value of the periodicity of the other light beam.

[0065] The previously given description of the periodicity of the S3 Stokes parameter of the light beam can apply accordingly to the S1 Stokes parameter and / or the S2 Stokes parameter of the light beam. The previously given description of the periodicity of the S3 Stokes parameter of the subsequent light beam can apply accordingly to the S1 Stokes parameter and / or the S2 Stokes parameter of the subsequent light beam.

[0066] A method according to the invention serves to measure the particle characteristics of a particle located in a measurement volume. The method comprises: generating a light beam that passes through the measurement volume and whose polarization in a cross-sectional plane can be described by means of a spatially dependent Stokes vector that has a spatially dependent S3 Stokes parameter; measuring an S3 Stokes parameter of the light beam reflected and / or scattered by the particle; outputting a measurement signal as a function of the measured S3 Stokes parameter; and determining the particle characteristics as a function of the measurement signal.

[0067] The device described above can be configured to perform the method. In particular, the method can be configured to operate the device described above. The description of the device given above can apply to identical or functionally equivalent features of the method and / or vice versa.

[0068] The measurement of the S3-Stokes parameter and the determination of the particle characteristics can each be performed continuously and without interruption. This allows for the determination of changes in the particle characteristics. In one embodiment of the device, the Poincaré sphere is approximately mapped onto the cross-sectional area of ​​the measuring beam, with the mapping being one-to-one (bijective). The measuring beam is oriented such that the particles to be characterized cross this beam obliquely. Oblique here means an angle other than 90° and other than 0°, in particular greater than 20° and less than 70°, advantageously between 40° and 50°. Using the known approximate mapping of the Poincaré sphere, the position of the particle within the measuring volume and / or the direction of propagation of the particle and / or the velocity of the particle can be determined in an associated method.Furthermore, if the shape is known, the size of the particle can be deduced.

[0069] Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention, both individually and in any combination. The figures show: Fig. 1 a schematic representation of a device for measuring a particle characteristic of a particle, Fig. 2 a) a schematic representation of polarization ellipses over a cross-section of a light beam before passing through a phase shifter element of the device of Fig. 1, Fig. 2 b) a schematic representation of a birefringence distribution of the phase shifter element, Fig. 2 c) a schematic representation of polarization ellipses over a cross-section of the light beam of Fig. 2 a) after passing through the phase shifter element of Fig. 2 b), Fig. 3 a schematic representation of a detector device of the apparatus of Fig. 1, Fig. 4 schematic representations of a further embodiment of polarization ellipses and a birefringence distribution of a phase shifter element according to the figures Fig. 2 a) to 2 c), Fig. 5 schematic representations of a further embodiment of polarization ellipses and birefringence distributions of phase-shifting elements, Fig. 6 schematic representations of a further embodiment of polarization ellipses and birefringence distributions of phase-shifting elements, Fig. 7 schematic representations of a further embodiment of polarization ellipses and birefringence distributions of phase-shifting elements, and Fig. 8 a schematic representation of a further embodiment of a device for measuring a particle characteristic of a particle.

[0070] Fig. Figure 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.

[0071] Particle 12 is a solid suspended in a liquid. The liquid flows through the measuring volume 14 at a known flow velocity. Fig. Figure 1 shows particle 12 both shortly before entering the measurement volume 14 and within the measurement volume 14.

[0072] The device 10 has a light source 16 configured to generate a light beam 18 that passes through the measuring volume 14. Within the measuring volume 14, the light beam 18 has a diameter that is at least 15 times larger than the diameter of the particle 12.

[0073] The light source 16 is designed as a laser beam source. The light source 16 has a light-generating device in the form of a resonator 20, in particular a laser resonator, for generating the light beam 18. The light beam 18 is a laser beam. The resonator 20 is a laser diode. The light beam 18 is a linearly polarized light beam. The light beam 18 propagates in the Z direction.

[0074] Fig. 2 a) zeigt Polarisationsellipsen 22 des Lichtstrahls 18 über einen Querschnitt des Lichtstrahls 18. Der Querschnitt verläuft orthogonal zu der Ausbreitungsrichtung des Lichtstrahls 18 und parallel zu einer X-Richtung und einer zu der X-Richtung orthogonal ausgerichteten Y-Richtung. Die X-Richtung und die Y-Richtung sind orthogonal zu der Z-Richtung ausgerichtet.

[0075] Fig. 2 a) zeigt, dass die Polarisationsellipsen 22 ortsunabhängig ausgerichtet sind. Alle Polarisationsellipsen 22 verlaufen parallel zu der X-Richtung. Dadurch ist der Lichtstrahl 18 ein, insbesondere homogen, linear polarisierter Strahl.

[0076] The light source 16 has a polarizing optics device 24. The polarizing optics device 24 is configured to change the polarization of the light beam 18. For this purpose, the polarizing optics device 24 has a phase-shifting element 26. The phase-shifting element 26 is a plate with a position-dependent birefringence. The light beam 18 passes through the phase-shifting element 26 for the purpose of changing its polarization.

[0077] Fig. Figure 2 b) shows the birefringence pattern of the phase shifter element 26 in an XY plane that extends in the X and Y directions. Fig. Figure 2 b) shows an alignment of optical axes 28 of the phase-shifting element 26. At a point within the XY plane, a local polarization component of the polarization of the light beam 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 4 relative to a local polarization component of the polarization of the light beam 18, which is aligned orthogonally to the optical axis 28, where λ is the wavelength of the light beam 18.

[0078] The orientation of the optical axes 28 in the X-direction is constant, in particular unchanging. The orientation of the optical axes 28 in the Y-direction depends on a position in the Y-direction. An angle α between the optical axis 28 and the X-direction can satisfy the condition: α = 45° + 90° · y|B, where y describes a position along the Y-direction and B describes a factor. B can, for example, be equal to 5 units of length. Thus, the phase-shifting element 26 causes a local change in the S3-Stokes parameter of the polarization when the light beam 18 passes through the phase-shifting element 26.

[0079] The optical axes 28 show in the exemplary embodiment of the Fig. 2 b) the slow axes. In an alternative embodiment not shown, the optical axes can be rotated by 90°. In other words, the in Fig. 2 b) The optical axes 28 shown can indicate the fast axis.

[0080] In the illustrated embodiment of the Fig. 2 b) The phase shift is positive. However, it is also conceivable that the phase shift could be negative.

[0081] Fig. Figure 2 c) shows the polarization of the light beam 18 after passing through the polarization optics device 24. Fig. 2 c) shows the polarization of the light beam 18 in a cross-sectional plane 30 within the measuring volume 14. The cross-sectional plane 30 runs orthogonally to the Z-direction within the measuring volume 14.

[0082] Fig. Figure 2 c) shows that the polarization of the light beam 18 is locally changed by means of the polarization optics device 24. In particular, the polarization state of the light beam 18 is location-dependent. As a result, the polarization state of the light beam 18 changes in the cross-sectional plane 30.

[0083] The polarization of light beam 18 can be described using a position-dependent Stokes vector. The Stokes vector has an S0 Stokes parameter, an S1 Stokes parameter, an S2 Stokes parameter, and an S3 Stokes parameter. The S0 Stokes parameter gives the intensity, the S1 Stokes parameter gives the difference in intensity between horizontally and vertically linearly polarized light, the S2 Stokes parameter gives the difference in intensity between ±45° linearly polarized light, and the S3 Stokes parameter gives the difference in intensity between right- and left-circularly polarized light.

[0084] Fig. 2 c) shows that the position-dependent Stokes vector changes continuously in the Y direction. In particular, the S1 Stokes parameter, the S2 Stokes parameter, and the S3 Stokes parameter are position-dependent. The S1 Stokes parameter, the S2 Stokes parameter, and the S3 Stokes parameter do not change in the X direction.

[0085] Fig. Figure 1 shows that particle 12 moves in a direction 32 parallel to the Y-direction and passes through the measurement volume 14. During its passage through the measurement volume 14, particle 12 is illuminated by the light beam 18. The light beam 18 is reflected and / or scattered by particle 12.

[0086] The light beam 18 reflected and / or scattered by the particle 12 strikes a detector device 34. A possible exemplary embodiment of the detector device 34 is shown in Fig. Figure 3 shows the detector device 34 is designed to measure the S0 Stokes parameter, S1 Stokes parameter, S2 Stokes parameter and the S3 Stokes parameter of the light beam reflected and / or scattered by the particle and to output a measurement signal depending on the measured Stokes parameters.

[0087] The detector device 34 has a first beam splitter 36, which is configured to split the light beam 18 reflected and / or scattered by the particle into a first light beam 38 and a second light beam 40. The first beam splitter 36 can be configured to split the light beam 18 reflected and / or scattered by the particle such that the first light beam 38 has a power component of 1 / 3 of the power of the light beam 18 reflected and / or scattered by the particle, and the second light beam 40 has a power component of 2 / 3 of the power of the light beam 18 reflected and / or scattered by the particle.

[0088] The first light beam 38 strikes a first polarizer 42 of the detector assembly 34. The first polarizer 42 splits the first light beam 38 into a first partial beam 44 and a second partial beam 46, which are polarized perpendicular to each other. The power of the first partial beam 44 is detected by a first photodiode 48 of the detector assembly 34. The power of the second partial beam 46 is detected by a second photodiode 50 of the detector assembly 34.

[0089] The detector device 34 is designed to determine the S0 Stokes parameter by adding the power detected by the first photodiode 48 and the power detected by the second photodiode 50.

[0090] The detector device 34 is designed to determine the S1 Stokes parameter by a difference between the power detected by the second photodiode 50 and the power detected by the first photodiode 48.

[0091] The second light beam 40 strikes a second beam splitter 52 of the detector device 34, which is configured to split the second light beam 40 into a third light beam 54 and a fourth light beam 56. The second beam splitter 52 can be configured to split the second light beam 40 such that the third light beam 54 has a power component of 1 / 2 of the power of the second light beam 40 and the fourth light beam 56 has a power component of 1 / 2 of the power of the second light beam 40.

[0092] The third light beam 54 passes through a λ / 2 plate 58, whose optical axis is aligned at an angle of 22.5° to the plane of the light beams 62 and 64, before the third light beam 54 strikes a second polarizer 60 of the detector assembly 34. The second polarizer 60 splits the third light beam 54 into a third partial beam 62 and a fourth partial beam 64, which are polarized perpendicular to each other. The power of the third partial beam 62 is detected by means of a third photodiode 66 of the detector assembly 34.

[0093] The power of the fourth partial beam 64 is detected by means of a fourth photodiode 68 of the detector device 34.

[0094] The detector device 34 is designed to verify the S0 Stokes parameter by adding the power detected by the third photodiode 66 and the power detected by the fourth photodiode 68.

[0095] The detector device 34 is designed to determine the S2 Stokes parameter by a difference between the power detected by the fourth photodiode 68 and the power detected by the third photodiode 66.

[0096] The fourth light beam 56 passes through a λ / 4 plate 70, whose optical axis is aligned at an angle of 45° to the plane of beams 74 and 76, before the fourth light beam 56 strikes a third polarizer 72 of the detector assembly 34. The third polarizer 72 splits the fourth light beam 56 into a fifth partial beam 74 and a sixth partial beam 76, which are polarized perpendicular to each other. The power of the fifth partial beam 74 is detected by a fifth photodiode 78 of the detector assembly 34. The power of the sixth partial beam 76 is detected by a sixth photodiode 80 of the detector assembly 34.

[0097] The detector device 34 is designed to verify the S0 Stokes parameter by adding the power detected by the fifth photodiode 78 and the power detected by the sixth photodiode 80.

[0098] The detector device 34 is designed to determine the S3 Stokes parameter by a difference between the power detected by the sixth photodiode 80 and the power detected by the fifth photodiode 78.

[0099] The detector device 34 outputs a measurement signal depending on the determined S0-Stokes parameter, S1-Stokes parameter, S2-Stokes parameter and S3-Stokes parameter.

[0100] An evaluation unit 82 of the device 10 is configured to determine the particle characteristics as a function of the measurement signal from the detector device 34. The evaluation unit 82 is a computer of the device 10.

[0101] The evaluation unit 82 contains the spatially dependent Stokes vectors of the in Fig. 2 c) The polarization of the light beam 18 shown is specified. Therefore, the evaluation unit 82 can compare the Stokes vector measured by the detector device 34 with the specified spatially dependent Stokes vectors. If the measured Stokes vector matches one of the specified spatially dependent Stokes vectors, the evaluation unit 82 determines the position assigned to the specified spatially dependent Stokes vector as the position of the particle 12 in the cross-sectional plane 30.

[0102] In Fig. 2 c) shows particle 12 at two different positions as it passes through the measurement volume 14. A position of particle 12 in the X-direction, in particular an X-coordinate value, can be known and specified to the evaluation unit 82.

[0103] During its passage through the measurement volume 14, particle 12 moves, among other things, from a position with an X-coordinate value of 3 and a Y-coordinate value of 0.5 to a position with an X-coordinate value of 3 and a Y-coordinate value of 1.5. The position with an X-coordinate value of 3 and a Y-coordinate value of 1.5 of particle 12 is in Fig. 2 c) shown as dotted lines.

[0104] If particle 12 is located at the position with an X-coordinate value of 3 and a Y-coordinate value of 0.5, the light beam 18 reflected and / or scattered by particle 12 has the polarization that the light beam 18 exhibits at the position with an X-coordinate value of 3 and a Y-coordinate value of 0.5. Therefore, the evaluation unit 82 can determine the position of particle 12 at the Y-coordinate value of 0.5 by comparing the Stokes vector of the light beam 18 reflected and / or scattered by particle 12, measured by the detector device 34, with the specified location-dependent Stokes vectors.

[0105] If particle 12 is located at the position with an X-coordinate value of 3 and a Y-coordinate value of 1.5, the light beam 18 reflected and / or scattered by particle 12 has the polarization that the light beam 18 exhibits at the position with an X-coordinate value of 3 and a Y-coordinate value of 1.5. Therefore, the evaluation unit 82 can determine the position of particle 12 at the Y-coordinate value of 1.5 by comparing the Stokes vector of the light beam 18 reflected and / or scattered by particle 12, measured by the detector device 34, with the specified location-dependent Stokes vectors.

[0106] Additionally, the evaluation unit 82 can determine the time it takes for the particle 12 to move from one position within the measuring volume 14 to another position within the measuring volume 14. Based on the measured time and the distance between the two positions, the evaluation unit 82 can determine the velocity of the particle 12 within the measuring volume 14. The distances between different positions can be predefined for the evaluation unit.

[0107] In the illustrated embodiment of the Fig. 2 c) The distance between the position with an X-coordinate value of 3 and a Y-coordinate value of 0.5 and the position with an X-coordinate value of 3 and a Y-coordinate value of 1.5 is 1 mm (millimeter). The evaluation unit 82 determines the time for the movement of particle 12 between these two positions, for example, 0.01 s (second). The evaluation unit 82 determines the velocity of particle 12 within the measuring volume 14 by dividing the distance of 1 mm by the determined time of 0.01 s to obtain 100 mm / s.

[0108] Therefore, the evaluation unit 82 can detect a temporal development of the measurement signal and determine the particle characteristic, for example the velocity of particle 12, based on the temporal development.

[0109] Additionally, the evaluation unit 82 can be configured to continuously determine the position of the particle 12 within the measuring volume 14 and to determine an acceleration of the particle 12 from this.

[0110] In Fig. 4 is a further embodiment according to the Fig. 2 shown, where the same reference numerals are used for identical and functionally equivalent elements, and in this respect, reference is made to the above explanations regarding the exemplary embodiment of the Fig. 2 can be referenced, so that essentially only the existing differences will be addressed.

[0111] In contrast to the previously described device 10, the polarization optics device 24 has a further phase shifter element, not shown, which is arranged in the direction of propagation of the light beam 18 after the phase shifter element 26.

[0112] Fig. Figure 4 a) shows polarization ellipses 22 of the light beam 18 across a cross-section of the light beam 18 before it passes through the further phase-shifting element. Since the further phase-shifting element is arranged after the phase-shifting element 26, the polarization ellipses 22 of the Fig. 4 a) and the polarization ellipses 22 of the Fig. 2 c) same.

[0113] Fig. Figure 4 b) shows the birefringence pattern of the further phase-shifting element in an XY plane that extends in the X and Y directions. Fig. 4 b) is an alignment of optical axes 28 of the further phase shifter element accordingly Fig. 2 b) is shown. At a point within the XY plane, a local polarization component of the polarization of the light ray 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 2 relative to a local polarization component of the polarization of the light ray 18, which is aligned orthogonal to the optical axis 28, where λ is the wavelength of the light ray 18.

[0114] The orientation of the optical axes 28 is constant, in particular unchanging, in the Y direction. The orientation of the optical axes 28 in the X direction depends on a position along the X direction. An angle α between the optical axis 28 and the X direction can satisfy the condition: α = 90° · x / B, where x describes a position along the X direction and B is a factor. B can, for example, be equal to 5 units of length. Thus, the additional phase-shifting element causes a local rotation of the polarization when the light beam 18 passes through the phase-shifting element 26.

[0115] Fig. 4 c) shows the polarization of the light beam 18 after passing through the further phase shifter element in the cross-sectional plane 30 within the measuring volume 14. Fig. Equation 4c) shows that the S1 and S2 Stokes parameters are location-dependent and change continuously along the X and Y directions. Additionally, the S3 Stokes parameter is location-dependent and changes continuously along the Y direction. This allows the position of particle 12 to be determined in the X and Y directions.

[0116] In Fig. 4 c) shows particle 12 at two different positions as an example during its passage through the measurement volume 14. The position of particle 12 in the X-direction and in the Y-direction is unknown. The evaluation unit 82 is provided with the position-dependent Stokes vectors of the particles in Fig. 4 c) shown polarization of the light beam 18 specified.

[0117] During its passage through the measurement volume 14, the particle 12 moves, for example, from a position with an X-coordinate value of 3 and a Y-coordinate value of 0.5 to a position in Fig. 4 c) dotted position with the X-coordinate value of 1 and the Y-coordinate value of 4.

[0118] If particle 12 is located at the position with the X-coordinate value of 3 and the Y-coordinate value of 0.5, the evaluation unit 82 determines the position of particle 12 based on the measured Stokes vector of the light beam 18 reflected and / or scattered by particle 12 by comparison with the specified location-dependent Stokes vectors to the X-coordinate value of 3 and the Y-coordinate value of 0.5.

[0119] If particle 12 is located at the position with the X-coordinate value of 1 and the Y-coordinate value of 4, the evaluation unit 82 determines the position of particle 12 based on the measured Stokes vector of the light beam 18 reflected and / or scattered by particle 12 by comparison with the specified location-dependent Stokes vectors for the X-coordinate value of 1 and the Y-coordinate value of 4.

[0120] Since the evaluation unit 82 can determine the X-coordinate value and the Y-coordinate value, the device 10 can act like a 2D camera.

[0121] In addition, the evaluation unit 82 can determine a velocity and / or an acceleration of the particle 12 within the measurement volume and / or other previously mentioned particle characteristics based on a determined time duration and several different positions of the particle 12 within the measurement volume 14.

[0122] In Fig. 5 is a further embodiment according to the Fig. 2 and Fig. 4 shown, where the same reference numerals are used for identical and functionally equivalent elements, and in this respect, reference is made to the above explanations regarding the exemplary embodiment of the Fig. 2 and Fig. 4 can be referenced, so that essentially only the existing differences will be addressed.

[0123] In the exemplary embodiment of the Fig. 5 The polarization optics device 24 of the device 10 has a phase shifter element and another phase shifter element, which are traversed successively by the light beam 18.

[0124] Fig. 5 a) zeigt Polarisationsellipsen 22 des linear polarisierten Lichtstrahls 18 vor dem Durchlaufen des Phasenschieber-Elements. Alle Polarisationsellipsen 22 verlaufen parallel zu der X-Richtung.

[0125] Fig. Figure 5 b) shows the birefringence pattern of the phase shifter element in an XY plane that extends in the X and Y directions. Fig. 5 b) is an alignment of optical axes 28 of the phase shifter element accordingly Fig. 2 b) is shown. At a point within the XY plane, a local polarization component of the polarization of the light ray 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 4 relative to a local polarization component of the polarization of the light ray 18, which is aligned orthogonal to the optical axis 28, where λ is the wavelength of the light ray 18.

[0126] The orientation of the optical axes 28 is constant in the Y-direction, in particular, unchanging. The orientation of the optical axes 28 in the X-direction depends on a position along the X-direction. An angle α between the optical axis 28 and the X-direction can satisfy the condition: α = 45° + 90° - x / B, where x describes a position along the X-direction and B is a factor. B can, for example, be equal to 5 units of length. Thus, the phase-shifting element causes a local change in polarization when the light beam 18 passes through the phase-shifting element 26.

[0127] Fig. Figure 5 c) shows the polarization of the light beam 18 after passing through the phase shifter element and before passing through the further phase shifter element.

[0128] Fig. Figure 5 d) shows the birefringence pattern of the further phase-shifting element in an XY plane that extends in the X and Y directions. Fig. 5 d) is an alignment of optical axes 28 of the further phase shifter element accordingly Fig. 2 b) is shown. At a point within the XY plane, a local polarization component of the polarization of the light ray 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 2 relative to a local polarization component of the polarization of the light ray 18, which is aligned orthogonal to the optical axis 28, where λ is the wavelength of the light ray 18.

[0129] The orientation of the optical axes 28 in the Y-direction is constant, in particular, unchanging. The orientation of the optical axes 28 in the X-direction depends on a position along the X-direction. An angle α between the optical axis 28 and the X-direction can satisfy the condition: α = 270° · x / B, where x describes a position along the X-direction and B is a factor. B can, for example, be equal to 5 units of length. Thus, the further phase-shifting element causes a local rotation of the polarization when the light beam 18 passes through the phase-shifting element 26.

[0130] Fig. 5 e) shows the polarization of the light beam 18 after passing through the further phase shifter element in the cross-sectional plane 30 within the measuring volume 14. Fig. Equation 5 e) shows that the S1 and S2 Stokes parameters are location-dependent and change continuously along the X-direction. Additionally, the S3 Stokes parameter is location-dependent and changes continuously along the X-direction. Because the S1, S2, and S3 Stokes parameters change continuously along the X-direction, albeit with different periodicities, the position of particle 12 in the X-direction can be determined with particular precision. Specifically, the S1, S2, and S3 Stokes parameters exhibit different periodicities. This results in a higher, and especially better, resolution in the X-direction.

[0131] In Fig. 6 is a further embodiment according to the Fig. 2 and Fig. 4 shown, where the same reference numerals are used for identical and functionally equivalent elements, and in this respect, reference is made to the above explanations regarding the exemplary embodiment of the Fig. 2 and Fig. 4 can be referenced, so that essentially only the existing differences will be addressed.

[0132] In the exemplary embodiment of the Fig. 6 The polarization optics device 24 of the device 10 has a first phase shifter element, a second phase shifter element and a third phase shifter element, which are traversed successively by the light beam 18.

[0133] Fig. Figure 6 a) shows polarization ellipses 22 of the linearly polarized light beam 18 before passing through the first phase-shifting element. All polarization ellipses 22 run parallel to the X-direction.

[0134] Fig. Figure 6 b) shows a course of the birefringence of the first phase shifter element in an XY plane according to Fig. 2 b) At a point within the XY plane, a local polarization component of the polarization of the light ray 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 2 relative to a local polarization component of the polarization of the light ray 18, which is aligned orthogonal to the optical axis 28, where λ is the wavelength of the light ray 18.

[0135] The orientation of the optical axes 28 is constant in the X-direction, in particular, unchanging. The orientation of the optical axes 28 in the Y-direction depends on a position along the Y-direction. An angle α between the optical axis 28 and the X-direction can satisfy the condition: α = 45° · y / B, where y describes a position along the Y-direction and B describes a factor. B can, for example, be equal to 5 units of length. Thus, the phase-shifting element causes a local rotation of the polarization when the light beam 18 passes through the phase-shifting element 26.

[0136] Fig. Figure 6 c) shows the polarization of the light beam 18 after passing through the first phase shifter element and before passing through the second phase shifter element.

[0137] Fig. Figure 6 d) shows a course of the birefringence of the second phase shifter element in an XY plane according to Fig. 2 b) At a point within the XY plane, a local polarization component of the polarization of the light ray 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 4 relative to a local polarization component of the polarization of the light ray 18, which is aligned orthogonal to the optical axis 28, where λ is the wavelength of the light ray 18.

[0138] The orientation of the optical axes 28 in the X and Y directions is constant, in particular unchanging. The angle α between the optical axis 28 and the X direction is 45°. The second phase-shifting element can be configured as a λ / 4 plate.

[0139] Fig. Figure 6 e) shows the polarization of the light beam 18 after passing through the second phase shifter element and before passing through the third phase shifter element.

[0140] Fig. Figure 6 f) shows a course of the birefringence of the third phase shifter element in an XY plane according to Fig. 2 b) At a point within the XY plane, a local polarization component of the polarization of the light ray 18, which is aligned parallel to the optical axis 28, experiences a phase shift of λ / 2 relative to a local polarization component of the polarization of the light ray 18, which is aligned orthogonal to the optical axis 28, where λ is the wavelength of the light ray 18.

[0141] The orientation of the optical axes 28 is variable in the X and Y directions. An angle α between the optical axis 28 and the X direction can satisfy the condition: α = 90° · f(x, y), where f(x,y) describes a function depending on the position in the X and Y directions.

[0142] Fig. Figure 6 g) shows the polarization of the light beam 18 after passing through the third phase shifter element in the cross-sectional plane 30 within the measuring volume 14. Fig. Equation 6(g) shows that the S1 and S2 Stokes parameters are location-dependent and change continuously along the X-direction. Additionally, the S3 Stokes parameter is location-dependent and changes continuously along the Y-direction. This allows the position of particle 12 to be determined in both the X- and Y-directions.

[0143] In Fig. 7 is a further embodiment according to the Fig. 2 and Fig. 4 shown, where the same reference numerals are used for identical and functionally equivalent elements, and in this respect, reference is made to the above explanations regarding the exemplary embodiment of the Fig. 2 and Fig. 4 can be referenced, so that essentially only the existing differences will be addressed.

[0144] In the exemplary embodiment of the Fig. 7 The polarization optics device 24 of the device 10 has a first phase shifter element and a second phase shifter element, which are traversed successively by the light beam 18.

[0145] Fig. Figure 7 a) shows polarization ellipses 22 of the linearly polarized light beam 18 before passing through the first phase-shifting element. All polarization ellipses 22 run parallel to the X-direction.

[0146] Fig. Figure 7 b) shows a course of the birefringence of the first phase shifter element in an XY plane according to Fig. 2 b). The first phase shifter element of the Fig. 7 b) and the further phase-shifting element of the Fig. 4 b) are identically designed. In this respect, the description of the further phase-shifting element applies. Fig. 4 b) also for the first phase shifter element of the Fig. 7 b).

[0147] Fig. Figure 7 c) shows the polarization of the light beam 18 after passing through the first phase shifter element and before passing through the second phase shifter element.

[0148] Fig. Figure 7 d) shows a course of the birefringence of the second phase shifter element in an XY plane according to Fig. 2 b). The second phase shifter element of the Fig. 7 d) and the phase shifter element of the Fig. 2 b) are identically designed. In this respect, the description of the phase shifter element applies. Fig. 2 b) also for the second phase shifter element of the Fig. 7 d).

[0149] Fig. Figure 7 e) shows the polarization of the light beam 18 after passing through the second phase shifter element in the cross-sectional plane 30 within the measuring volume 14. Fig. Equation 7 e) shows that the S1 and S2 Stokes parameters are location-dependent and change continuously along the X and Y directions. Additionally, the S3 Stokes parameter is location-dependent and changes continuously along the X and Y directions. Therefore, the position of particle 12 in the X and Y directions can be determined with high precision based on the S1, S2, and S3 Stokes parameters.

[0150] As the examples of implementation of the Fig. As shown in Figures 2 and 4 to 7, the light beam 18 can exhibit location-dependent polarization states in the cross-sectional plane after passing through the polarization optics device 24. It is also conceivable that the polarization state in the cross-sectional plane can be described along the X-direction and / or the Y-direction by means of a trajectory on the Poincaré sphere.

[0151] For example, the polarization state along the X-direction and / or the Y-direction can be described by a straight trajectory on the Poincaré sphere extending from right-handed circularly polarized to left-handed circularly polarized or vice versa.

[0152] Alternatively, the polarization state along the X-direction and / or the Y-direction can be described by a helical trajectory on the Poincaré sphere, extending from right-handed circular polarization to left-handed circular polarization or vice versa. The helical trajectory can have one or more spiral turns.

[0153] It is also conceivable that the polarization state in the cross-sectional plane can be described by means of a mapping, in particular an approximate mapping, of at least part of the Poincaré sphere onto the cross-sectional plane. An approximate mapping can be understood to mean that, in reality, a not fully polarized state with DOP=1 is often achievable. In particular, by designating the mapping as "approximate," residual depolarization can be taken into account.

[0154] In Fig. Figure 8 is a further embodiment of the device 10 of the Fig. 1 shown, where the same reference numerals are used for identical and functionally equivalent elements, and in this respect, reference is made to the above explanations regarding the exemplary embodiment of the Fig. 1 can be referenced, so that essentially only the existing differences will be addressed.

[0155] The light source 16 is designed to generate a further light beam 84 that passes through the measurement volume 14 and whose polarization in a further cross-sectional plane 86 can be described by means of a position-dependent Stokes vector that has a position-dependent S3 Stokes parameter.

[0156] The light source 16 has a light-generating device in the form of a further resonator 88, in particular a laser resonator, for generating the further light beam 84. The further light beam 84 is a laser beam. The further resonator 88 is a laser diode. The further light beam 84 is a linearly polarized light beam.

[0157] The light source 16 has a further polarization optics device 90. The further polarization optics device 90 is configured to change the polarization of the further light beam 84. The further polarization optics device 90 can be configured in the same way as the polarization optics device 24.

[0158] Light beam 18 and the additional light beam 84 can define an angle 92 between them before striking a particle 12 passing through the measuring volume 14. Due to this angle 92, light beam 18 and the additional light beam 84 differ in their angle of incidence on the particle 12. This allows the particle characteristics to be determined in the X and Y directions with respect to light beam 18 and in the X and Y directions with respect to the additional light beam 84. By comparing the particle characteristics determined using light beam 18 with those determined using the additional light beam 84, a particle characteristic with respect to light beam 18 in the Z direction can be determined, thus enabling a three-dimensional determination of the particle characteristics. The evaluation unit 82 can be configured for the three-dimensional determination of the particle characteristics.

[0159] Light beam 18 and the other light beam 84 differ from each other in one wavelength.

[0160] The detector assembly 34 is formed by a first detector unit 94 and a second detector unit 96.

[0161] The first detector unit 94 has a detector module 98, the structure and function of which are shown in the illustration. Fig. 3 corresponds and insofar as it refers to the corresponding description for Fig. Reference is made to 3. The detector module 98 is set up for measuring the Stokes vector of the light beam 18 reflected and / or scattered by the particle 12.

[0162] Additionally, the first detector unit 94 has a wavelength filter 100, which is positioned in front of the detector module 98. The wavelength filter 100 is configured to transmit the wavelength of the light beam 18 with a transmittance of over 80%, preferably 90%, 95%, 98%, or 99%, and to reflect the wavelength of the further light beam 84 with a reflectance of over 80%, preferably 90%, 95%, 98%, or 99%. This prevents light from the further light beam 84, reflected and / or scattered by the particle 12, from entering the detector module 98 and thus affecting the measurement of the Stokes vector of the light beam 18 reflected and / or scattered by the particle 12.

[0163] The second detector unit 96 has a detector module 102, the structure and function of which are shown in the illustration. Fig. 3 corresponds and insofar as it refers to the corresponding description for Fig. Reference is made to section 3. The detector module 102 is designed to measure the Stokes vector of the further light beam 84 reflected and / or scattered by the particle 12.

[0164] Additionally, the second detector unit 96 has a wavelength filter 104, which is positioned in front of the detector module 102. The wavelength filter 104 is configured to transmit the wavelength of the additional light beam 84 with a transmittance of over 80%, preferably 90%, 95%, 98%, or 99%, and to reflect the wavelength of the light beam 18 with a reflectance of over 80%, preferably 90%, 95%, 98%, or 99%. This prevents light from the light beam 18 reflected and / or scattered by the particle 12 from entering the detector module 102 and thus influencing the measurement of the Stokes vector of the additional light beam 84 reflected and / or scattered by the particle 12.

[0165] The detector device 34 outputs the measurement signal as a function of the measured Stokes vectors of the light beam 18 reflected and / or scattered by the particle 12 and another measurement signal as a function of the measured Stokes vectors of the further light beam 84 reflected and / or scattered by the particle 12.

[0166] The evaluation unit 82 determines the particle characteristics as a function of the measurement signal and the further measurement signal of the detector device 34. The particle characteristics, in particular a position, a velocity and / or an acceleration, of the particle 12 within the measurement volume 14 can be determined in all three spatial dimensions.

[0167] In a further embodiment not shown, the light beam and the second light beam can additionally or alternatively differ from each other in the distribution of the values ​​of the position-dependent S1-Stokes parameter, the position-dependent S2-Stokes parameter, and / or the position-dependent S3-Stokes parameter. For example, at a given position within the measurement volume, the S3-Stokes parameter of the light beam can have a positive value and the S3-Stokes parameter of the second light beam can have a negative value, or vice versa.

[0168] In another embodiment not shown, the S3-Stokes parameter can have a periodicity greater than or equal to 2 in the X-direction and / or the Y-direction. This periodicity allows a polarization state to repeat in the X-direction and / or the Y-direction. The periodicity can specify how often the polarization state repeats in the X-direction and / or the Y-direction.

[0169] In another embodiment, not shown, the device can be configured according to the instructions in Fig.The device shown in Figure 8 is configured in which the light beam and the second light beam differ from each other in a periodicity with which the polarization state repeats itself in the X-direction and / or in the Y-direction. Advantageously, this can further improve the measurement accuracy. This can be achieved by ensuring that the periodicity of the light beam and the periodicity of the second light beam do not have a common divisor. Preferably, the periodicity of the light beam and / or the periodicity of the second light beam can be a prime number. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 123 464 A1

[0003]

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 light beam (18) that passes through the measurement volume (14) and whose polarization in a cross-sectional plane (30) can be described by means of a position-dependent Stokes vector that has a position-dependent S3 Stokes parameter, - a detector device (34) configured to measure an S3-Stokes parameter of the light beam (18) reflected and / or scattered by the particle (12) and to output a measurement signal depending on the measured S3-Stokes parameter, and - an evaluation unit (82) designed to determine the particle characteristics as a function of the measurement signal from the detector device (34). [2] Device (10) according to claim 1, - wherein the light source (16) comprises a light-generating device (20) and a polarization optics device (24), - wherein the light-generating device (20) is designed to generate the light beam (18), - wherein the polarization optics device (24) is configured to adjust the polarization of the light beam (18) such that the position-dependent Stokes vector has the position-dependent S3 Stokes parameter. [3] Device (10) according to claim 2, - wherein the polarization optics device (24) has a phase shifter element (26) which causes a location-dependent change in the polarization of the light beam (18). [4] Device (10) according to any one of the preceding claims, - wherein the light source (16) is designed to generate the light beam (18) such that the position-dependent S3-Stokes parameter changes continuously along an X-direction and / or along a Y-direction orthogonal to the X-direction. [5] Device (10) according to any one of the preceding claims, - wherein the position-dependent Stokes vector of the light ray (18) has a position-dependent S1 Stokes parameter and a position-dependent S2 Stokes parameter, - wherein the detector device (34) is configured to measure an S1 Stokes parameter and an S2 Stokes parameter of the light beam (18) reflected and / or scattered by the particle (12) and to output the measurement signal as a function of the measured S1 Stokes parameter and the measured S2 Stokes parameter. [6] Device (10) according to claim 5, - wherein the light source (16) is configured to generate the light ray (18) such that the position-dependent S1-Stokes parameter and the position-dependent S2-Stokes parameter of the light ray (18) in the cross-sectional plane (30) change continuously along the X-direction and / or along the Y-direction. [7] Device (10) according to any one of the preceding claims, - wherein the light source (16) is configured to generate a further light beam (84) which passes through the measurement volume (14) and whose polarization in a cross-sectional plane (86) can be described by means of a position-dependent Stokes vector which has a position-dependent S3 Stokes parameter, - wherein the detector device (34) is configured to measure a further S3-Stokes parameter of the further light beam (84) reflected and / or scattered by the particle (12) and to output a further measurement signal depending on the measured further S3-Stokes parameter, - wherein the evaluation unit (82) is designed to determine the particle characteristics as a function of the further measurement signal from the detector device (34). [8] Device (10) according to claim 7, - wherein the position-dependent Stokes vector of the further light ray (84) has a position-dependent S1 Stokes parameter and a position-dependent S2 Stokes parameter, - wherein the detector device (34) is configured to measure an S1 Stokes parameter and an S2 Stokes parameter of the further light beam (84) reflected and / or scattered by the particle (12) and to output the measurement signal as a function of the measured S1 Stokes parameter and the measured S2 Stokes parameter. [9] Device (10) according to claim 7 or 8, - wherein the light beam (18) and the further light beam (84) differ from each other in their wavelength, and / or - where a distribution of the values ​​of the position-dependent S3-Stokes parameter of the light ray (18) and a distribution of the values ​​of the position-dependent S3-Stokes parameter of the further light ray (84) differ from each other. [10] Device (10) according to any one of the preceding claims, - wherein the position-dependent S3-Stokes parameter of the light beam (18) has a periodicity with a value greater than or equal to 1, preferably 2, and / or - wherein the location-dependent S3-Stokes parameter of the further light beam (84) has a periodicity with a value greater than or equal to 1, preferably 2. [11] Method for measuring a particle characteristic of a particle (12) located in a measuring volume (14), comprising: - Generating a light beam (18) that passes through the measurement volume (14) and whose polarization in a cross-sectional plane can be described by means of a position-dependent Stokes vector that has a position-dependent S3 Stokes parameter, - Measuring an S3-Stokes parameter of the light beam (18) reflected and / or scattered by the particle (12), - Outputting a measurement signal depending on the measured S3-Stokes parameter, and - Determining the particle characteristics as a function of the measurement signal.

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