Device and method for characterising at least one particle in a measurement volume

Abstract

The present invention relates to a device for characterising at least one particle in a measurement volume, comprising at least one light source for emitting at least one light beam along a beam path in the direction of the measurement volume, at least one first beam shaping optical unit arranged in the beam path, wherein the first beam shaping optical unit is designed to form, in the measurement volume, a first location-dependent intensity distribution of the light in a plane perpendicular to the beam path at a first focal position along the beam path of the light beam, and at least one detector, wherein the detector is designed to pick up at least a part of the measurement beam generated by reflection and / or scattering of the light off the particle in the measurement volume and to output at least one measured intensity signal to an evaluation unit, wherein the evaluation unit is designed to determine a property of the particle within the measurement volume depending on the intensity signal, wherein the first beam shaping optical unit is at least partly wavelength-dependent in order to form at least one second location-dependent intensity distribution of the light in a plane perpendicular to the beam path at a second focal position along the beam path of the light beam.

Description

[0001] DEVICE AND METHOD FOR CHARACTERIZING AT LEAST ONE PARTICLE IN A MEASURING VOLUME

[0002] The present invention relates to a device for characterizing at least one particle in a measurement volume, comprising at least one light source for emitting at least one light beam along a beam path in the direction of the measurement volume, at least one first beam-shaping optic arranged in the beam path in front of the measurement volume, wherein the first beam-shaping optic is designed to form a first location-dependent intensity distribution of the light in the measurement volume in a plane perpendicular to the beam path at a first focus position along the beam path of the light beam, and at least one detector, wherein the detector is designed to detect at least a portion of the measurement beam generated by reflection and / or scattering of the light at the particle in the measurement volume and to output at least one measured intensity signal to an evaluation unit, wherein the evaluation unit is designed toto determine a property of the particle within the measurement volume depending on the intensity signal.

[0003] Such devices are already well known and are used, for example, to measure the position of particles in a liquid (US 8 867 046 B2) or other environments (US 2021 / 381 948 A1), to determine the size of particles (CN 113 075 097 A), or to inspect wafers in semiconductor production (US 2018 / 364 177 A1). Typically, an optical property of an incoming light beam is used to measure, after reflection or scattering, this property of the particle transverse to the beam axis of the light beam. By manipulating several properties of the light beam in this plane perpendicular to the beam axis of the light beam, further properties, such as the position of the particle in the plane, can be determined.For example, it is known to create a location-dependent intensity distribution and / or a location-dependent polarization distribution in a plane perpendicular to the beam axis and to measure these properties in order to precisely determine the position of a particle. By additionally considering the temporal sequence of the signals, particle velocities can also be determined in this way. Publication WO 2022 / 243 006 A1 discloses a metrology system configured to emit light at a plurality of different wavelengths, each wavelength being associated with a specific position along an axis perpendicular to the beam axis.

[0004] While these known devices and methods already offer many advantages, such as non-contact and non-destructive measurements and provide very good results in two dimensions, it is not possible to precisely measure a particle position along the beam axis using the devices known from the state of the art.

[0005] Against this background, the task is to provide a device and a method for characterizing at least one particle in a measuring volume, which can also precisely measure a particle property along the beam axis.

[0006] To achieve the object, a device for characterizing at least one particle in a measurement volume is proposed, comprising: at least one light source for emitting at least one light beam along a beam path in the direction of the measurement volume, at least one first beam-shaping optic arranged in the beam path in front of the measurement volume, wherein the first beam-shaping optic is designed to form a first location-dependent intensity distribution of the light in the measurement volume in a plane perpendicular to the beam path at a first focus position along the beam path of the light beam, and at least one detector, wherein the detector is designed to detect at least a portion of the measurement beam generated by reflection and / or scattering of the light at the particle in the measurement volume and to output at least one measured intensity signal to an evaluation unit, wherein the evaluation unit is designed toto determine a property of the particle within the measurement volume as a function of the intensity signal, wherein the first beam-shaping optics are designed to be at least partially wavelength-dependent in order to form at least a second location-dependent intensity distribution of the light in a plane perpendicular to the beam path at a second focus position along the beam path of the light beam.

[0007] In the device according to the invention, a wavelength dependence of the first beam-shaping optics is exploited to generate location-dependent intensity distributions at two different focus positions along the beam path. The chromatic aberration of optics such as lenses is well known, but has so far been deliberately compensated for by achromatic optics. In the device according to the invention, this property, which is generally considered an optical error, is specifically exploited to determine a particle property, such as a particle position, even in a dimension parallel to the beam path of the light beam.

[0008] According to the invention, it is also possible for more than two focus positions, i.e., more than two location-dependent intensity distributions, to be provided depending on the at least one light source and / or first beam-shaping optics. According to the invention, all focus positions are spaced apart from one another along the beam path of the light beam, i.e., in particular, perpendicular to the plane in which the location-dependent intensity distribution is formed. For example, three, four, five, or more focus positions are provided.

[0009] The location-dependent intensity distribution is preferably provided inhomogeneously, for example oval or elliptical in shape, in particular with a maximum intensity at a central point, in particular the center of the surface, and an intensity that decreases towards the outside. The intensity along an outer contour of the oval or ellipse is particularly preferably minimal. Such an oval or elliptical intensity distribution preferably comprises two axes that are perpendicular to one another and run through the center, wherein the intensity along one of the axes, also referred to as the main axis, preferably extends further than along the transverse axis that is perpendicular thereto. Very particularly preferably, the oval or ellipse has an extension of 0.5 mm to 10 mm, in particular of 1 mm to 5 mm, along the main axis and / or an extension of 1 pm to 100 pm, in particular of 30 pm to 70 pm, along the transverse axis.An inhomogeneous intensity distribution can be used to determine a property of a particle, such as its position in the plane. Combined with the wavelength-dependent focal position of the intensity distribution, this allows an additional property, such as an additional dimension of the particle's position, to be captured.

[0010] The particle is, for example, a solid or a liquid particle, in particular a liquid droplet. The measurement volume is preferably a gas, such as air, a vacuum, or a liquid. It can therefore be a solid particle that is freely movable in a gas or liquid. Likewise, the particle can be arranged stationary or movable on a surface, for example a solid particle or a liquid particle on a wafer surface, in particular under an air atmosphere, an atmosphere with a predetermined gas composition, or under a vacuum. Examples of liquid particles can be a water particle in an oil bath or, conversely, an oil particle in a water bath. Another possibility would be a liquid particle in a gas environment, such as a liquid droplet emerging from a spray nozzle or a gas bubble in a liquid.

[0011] Preferably, a property of a particle is at least a position in at least one spatial direction, particularly preferably in at least two spatial directions, even more preferably in all three spatial directions, a speed and / or a particle size.

[0012] The evaluation unit can be designed as an electrical processing unit by means of which the property(ies) of the particles can be determined. A mathematical model that describes an analytically or empirically determined relationship between an intensity of the measuring beam and the particle property can be implemented on the evaluation unit. By measuring an intensity of the measuring beam, the intensity signal output by the detector can be assigned to the particle property to be determined using the mathematical model. Additionally or alternatively, discrete table values ​​can be stored on the evaluation unit by means of which a measured intensity value of the measuring beam can be compared with a stored intensity value and can be assigned to the corresponding particle property.Additionally or alternatively, at least one characteristic curve can be stored in the evaluation unit, indicating an intensity profile depending on the characteristics of a particle property. Using the characteristic curve, a measured intensity of the measuring beam can be assigned to the particle property to be determined. In particular, the characteristic curve describes a profile of the intensity of the measuring beam depending on a particle position along an axis in the plane of the location-dependent intensity profile.

[0013] According to an advantageous embodiment of the invention, the at least one light source is a broadband light source with a continuous spectrum or a line spectrum, or the device comprises a plurality of at least substantially monochromatic light sources, in particular lasers, with different wavelength ranges. Preferably, the first beam-shaping optics are configured to form the light beam in the measurement volume by wavelength-dependent superposition of the light sources. Those skilled in the art will understand that in all of the above-mentioned cases, the chromatic aberration of the first beam-shaping optics can be utilized to generate the location-dependent intensity distributions at the two focus positions.The distance between the two focus positions along the beam axis, i.e. the direction of the light beam's path, is determined by a variety of parameters, such as the spectral distance of the wavelengths of the light source(s), the material used for the optics (in the case of glasses, this is expressed, among other things, by the Abbe number), the thickness of the optics, etc. It is therefore possible to specifically adjust the measuring range or resolution along the light beam's path in a variety of ways.

[0014] According to a further advantageous embodiment of the invention, the first beam-shaping optics are designed to additionally form a first location-dependent polarization distribution of the light in a plane perpendicular to the beam path at the first focus position along the beam path of the light beam and a second location-dependent polarization distribution of the light in a plane perpendicular to the beam path at the second focus position along the beam path of the light beam in the measurement volume. The polarization distribution is thus superimposed on the intensity distribution in the same plane. If the measurement beam is detected in a correspondingly polarization-dependent manner, an additional property, such as an additional dimension of the position, can thus advantageously be detected.

[0015] Preferably, the at least one light source and / or the first beam-shaping optics are configured such that the light beam has a polarization, wherein the polarization varies along at least one direction, in particular in the steps of 0°, 45°, 90°, and 135°, and / or that the polarization is circular or elliptical polarization along one direction. Those skilled in the art will understand that certain light sources, for example lasers, can already emit polarized light. Alternatively or additionally, optical tools exist with the aid of which an incoming polarized or unpolarized light beam can be provided with a predetermined polarization.

[0016] According to an advantageous embodiment of the invention, the device comprises a second beam-shaping optical unit arranged in the beam path of the measuring beam, wherein the second beam-shaping optical unit is designed to shape the measuring beam for the at least one detector, in particular to focus and / or collimate it, and to split the measuring beam at least wavelength-dependently, in particular also polarization-dependently. A wavelength-dependent splitting of the measuring beam can occur before or after a polarization-dependent splitting of the measuring beam. Those skilled in the art will understand that a polarization-dependent splitting only needs to occur if the first beam-shaping optical unit has impressed a location-dependent polarization distribution on the light beam.

[0017] Preferably, the second beam-shaping optics are designed such that the measuring beam is split and a portion is fed to at least one wavelength-specific detector, with another portion preferably being fed to at least one polarization-specific detector. Thus, according to the invention, several alternatives for detecting the measuring beam are provided, particularly if, in addition to the at least two location-dependent intensity distributions, location-dependent polarization distributions are also provided. One possibility, for example, is that the measuring beam is first split according to its polarization components; with n polarization components, n polarization-specific detectors are then preferably used. The measuring beam can then be split according to its wavelengths, i.e., the spectral components.Here, m wavelength-specific detectors for m spectral components are particularly preferably provided. In this case, nxm detectors are therefore required. A particularly preferred embodiment provides that the measuring beam is first split (independent of wavelength and polarization) into several, in particular two, parts, and one part of the measuring beam is detected wavelength-dependently (in one or more wavelength-specific detectors) and the other part is detected polarization-dependently. A wavelength-specific detector can be a spectrometer, for example. A further alternative or additional embodiment provides that the second beam-shaping optics and / or the at least one detector comprise at least one wavelength-selective optical element, such as a dichrotic mirror, an optical grating, a prism, a bandpass filter, and / or an edge filter.This is particularly preferred when only a few different wavelengths or wavelength ranges, especially two wavelengths (or wavelength ranges), are used. In this case, one wavelength-selective optical element is sufficient to enable appropriate detection.

[0018] According to yet another advantageous embodiment of the invention, the first beam-shaping optics and / or the second beam-shaping optics comprise at least one, in particular dichroic, mirror, a lens, in particular a cylindrical and / or collector lens with a predetermined chromatic aberration, a prism, an optical grating, a retardation plate, a space-variant polarization converter, and / or a diffractive vortex phase plate. According to a particularly preferred embodiment, the first beam-shaping optics and / or the second beam-shaping optics comprise at least one multilayer mirror, wherein at least two layers of the mirror have different radii of curvature, wherein the first layer in the beam axis is at least partially reflective in a first wavelength range and at least partially transparent in a second wavelength range different from the first wavelength range.With such a mirror, different wavelength ranges of the light beam can be advantageously focused at different focus positions along the beam path due to the different radii of curvature. These optical aids enable particularly advantageous simple and precise beam shaping or wavelength-dependent focusing of the light beam at the various focus positions.

[0019] It is preferably provided that the first beam-shaping optics and / or the second beam-shaping optics comprise a lens combination, preferably a lens doublet and / or a lens triplet. A lens doublet is, for example, a lens consisting of two lenses combined in a specific way. In this way, by taking into account the shape, thickness, and material of the lenses, as well as the gap between the lenses, beam shaping can be specifically influenced and, in particular, chromatic aberration, for example, can be specifically influenced in the desired manner.

[0020] According to an advantageous embodiment of the invention, the at least one detector comprises at least one photodiode, at least one line-scan camera, and / or at least one 2D camera. Especially when using a line-scan camera (also referred to as a line camera), a further spatial dimension can be resolved in a particularly advantageous manner without having to accept a loss of speed, as is usually the case with 2D cameras.

[0021] According to a further advantageous embodiment of the invention, it is provided that the at least one light source, the light beam shaped by the first beam-shaping optics and / or the at least one detector are movable relative to the at least one particle. The person skilled in the art understands that, depending on the field of application, one of the above-mentioned variants is usually more advantageous. For example, for the detection of freely movable particles, such as solid or liquid particles in a gas or in a liquid, it is not necessary for the light source, the light beam or the detector to be movable, since the particle is movable. For example, to detect contamination (in the form of solid and / or liquid particles) on a surface, in particular a wafer surface, it can be useful to move the light beam over the surface.This can be achieved, for example, by a scanning movement of the light beam, with the movement of the light beam preferably being generated by corresponding movements of the first beam-shaping optics. Alternatively or additionally, a movement of the at least one light source and / or the at least one detector is also conceivable.

[0022] To achieve the object mentioned at the outset, a method for characterizing at least one particle using a device according to the invention is further proposed, wherein a first beam-shaping optics forms a first location-dependent intensity distribution in a plane perpendicular to the beam path at a first focus position along the beam path of the light beam from a light beam of at least one light source in a measurement volume along a beam path of the light beam, wherein the first beam-shaping optics is designed to be wavelength-dependent in such a way that it forms a second location-dependent intensity distribution in a plane perpendicular to the beam path at a second focus position along the beam path of the light beam from the light beam of at least one light source in the measurement volume along the beam path of the light beam,wherein at least a portion of the measuring beam generated by reflection and / or scattering of the light on the particle in the measuring volume is detected by at least one detector and at least one measured intensity signal is output to an evaluation unit, wherein the evaluation unit determines a property of the particle within the measuring volume as a function of the intensity signal.

[0023] The method according to the invention can achieve the same advantages and technical effects as have already been described in connection with the photonic system according to the invention.

[0024] According to an advantageous embodiment of the invention, the first beam-shaping optics are designed to additionally form a first location-dependent polarization distribution of the light in the measurement volume in a plane perpendicular to the beam path at the first focus position along the beam path of the light beam and a second location-dependent polarization distribution of the light in a plane perpendicular to the beam path at the second focus position along the beam path of the light beam. This advantageously makes it possible to resolve an additional property, in particular an additional dimension, through polarization-dependent detection of the measurement beam. According to an advantageous embodiment of the invention, a second beam-shaping optics splits the measurement beam, in particular depending on the wavelength and / or polarization.Preferably, the second beam-shaping optics shapes the measuring beam in the manner required by the at least one detector. Particularly preferably, the second beam-shaping optics focuses the measuring beam.

[0025] Alternatively or in addition to the advantageous embodiments explained above, the advantageous embodiments and features explained in connection with the device according to the invention can be used in the method.

[0026] Further details and advantages of the invention will be explained below with reference to the exemplary embodiments shown in the figures. Herein:

[0027] Fig. 1 is a schematic representation of a device according to the invention for characterizing at least one particle in a measuring volume according to a first exemplary embodiment;

[0028] Fig. 2 is a schematic representation of several exemplary embodiments of the device according to the invention;

[0029] Fig. 3 a)-c) schematic representations of the spectra of light sources according to exemplary embodiments of the device according to the invention;

[0030] Fig. 4 is a schematic representation of a first and a second location-dependent intensity distribution according to an exemplary embodiment of the device according to the invention or the method according to the invention;

[0031] Fig. 5 is a schematic representation of a location-dependent intensity distribution and a location-dependent polarization distribution according to an exemplary embodiment of the device according to the invention or the method according to the invention.

[0032] A Cartesian coordinate system with three perpendicular axes x, y, and z is used for explanation purposes below. For purely exemplary purposes, the z-axis is defined as the axis of the light beam 4 in the region of or shortly before the measurement volume 5, i.e., as the axis of the beam path of the light beam 4. Those skilled in the art will understand that the light beam 4 does not have to lie on this axis along its entire path. In particular, a first beam-shaping optic 3 can shape the light beam 4 in any desired manner until its beam path coincides with the z-axis.

[0033] The schematic representation in Fig. 1 shows a schematic representation of a device 1 according to the invention for characterizing at least one particle 10 in a measurement volume 5 according to a first exemplary embodiment. The device 1 comprises a light source 2, which generates a light beam 4 directed toward a measurement volume 5 in which a particle 10 to be characterized is present.

[0034] The light beam 4 is shaped by a first beam-shaping optics 3, which comprises one or more optical elements, such as dichroic mirrors, cylindrical lenses, etc., such that a first location-dependent intensity distribution h(x,y) is formed in the measurement volume 5 at a first focus position zi in a plane perpendicular to the beam path of the light beam 4 (in the region of the measurement volume 5). When the particle moves into this location-dependent intensity distribution h(x,y), the light beam 4 is reflected and / or scattered by the particle. In this way, a measurement beam 6 is generated.

[0035] In the embodiment shown here, the reflected measuring beam 6 is detected; therefore, it is a reflection arrangement. The reflected measuring beam 6 is preferably shaped by a second beam-shaping optic 7, for example, focused to suit a detector 8, so that the detector 8 can determine an intensity signal. This signal is then forwarded to an evaluation unit 9, in particular an electronic one, of a type well known in the art and therefore not explained in detail below and not shown again in the following figures. However, it is also conceivable that no second beam-shaping optic 7 is required.

[0036] By means of a corresponding evaluation in a manner which is already known in principle, a property of the particle 10 can thus be determined, for example a position of the particle 10 in the xy plane, or a position along the y or x axis at a specific time at which the particle 10 traverses a specific position on the x or y axis.

[0037] According to the invention, the first beam-shaping optics 3 is now designed such that a second location-dependent intensity distribution l2(x,y) is additionally formed at a second focus position Z2 along the beam path of the light beam 4. This is made possible by the fact that the first beam-shaping optics 3 is deliberately designed to be wavelength-dependent. A simple variant would be to exploit the chromatic aberration of optical elements, such as lenses, of the first beam-shaping optics 3. As a result, the light beam 4 is focused at different positions along the beam axis, here the z-axis, depending on the wavelength. The location-dependent intensity distributions h(x,y) and l2(x,y) generated by the first beam-shaping optics 3 are formed at these focus positions z1, Z2.

[0038] By appropriately designing the detector 8 to match the wavelength, for example, a spectrometer, a further property of the particle 10, in particular a further dimension of the particle position, can now be determined. This advantageously enables, in particular, a depth measurement, i.e., a resolution of the z-dimension.

[0039] The person skilled in the art understands that the invention is not limited to two focus positions zi and Z2 and the associated first and second location-dependent intensity distributions h(x,y), l2(x,y).

[0040] By means of the device 1, for example, the position of a particle 10 in the measuring volume 5 can thus be measured advantageously in at least two dimensions.

[0041] Fig. 2 shows a schematic representation of several exemplary embodiments of the device 1 according to the invention. Additional, optional configurations are shown in dashed lines, which can be combined both individually and together with the illustrated embodiment, but in principle also with the embodiment shown in Fig. 1. The embodiment underlying Fig. 2 is a transmission arrangement. This means that, instead of a reflected measuring beam 6, a scattered measuring beam 6 (in the direction of the light beam 4) is detected. The detector 8 is therefore located behind the measuring volume 5 in the z-direction.

[0042] Additionally shown here is an optional embodiment according to which, in addition to the light source 2, a further light source 2' is included, the light beam of which can be superimposed on that of the light source 2 by the first beam-shaping optics 3, here for example by a further first beam-shaping optics 3' or at least one additional optical element 3' of the first beam-shaping optics 3. This makes it possible, for example, to use two light sources 2, 2' with spectra in different wavelength ranges, which are first superimposed by the first beam-shaping optics 3, 3' and then form the first and second intensity distributions h(x,y), l2(x,y) depending on the wavelength. This embodiment is particularly advantageous because the light beams of the two light sources 2, 2' are independently superimposed by a first beam-shaping optics 3 and a further first beam-shaping optics 3', orvarious optical elements of the first beam-shaping optics 3 can be shaped in a desired manner. Since the light beams of the at least two light sources 2, 2' can initially be shaped separately, the wavelength-dependent focus positions can also be adjusted in a simple and precise manner. In this way, it is particularly advantageous to specifically influence the beam shaping and / or the focus positions by appropriately adjusting the optical elements, in particular even without exploiting chromatic aberration.

[0043] In addition, the second beam-shaping optics 7, which can also comprise further optical elements 7' or further second beam-shaping optics 7', is shown here as an optional embodiment. It is conceivable that with a corresponding design of the detector 8, a second beam-shaping optics 7 can be dispensed with, although the presence of the second beam-shaping optics 7 is preferred. Furthermore, a further detector 8' is shown here as an additional or alternative optional embodiment. Particularly preferably, an equal number of detectors 8, 8' can be used depending on the number of wavelength ranges used, which are also referred to as spectral components (of the measuring beam 6), wherein each detector 8, 8' is specifically designed for a certain wavelength or a certain wavelength range.In this case, the second beam-forming optics 7 can, for example, be designed such that it divides or splits the measuring beam 6 depending on the wavelength and feeds the individual parts of the measuring beam 6 to the respective detectors 8, 8'.

[0044] A further embodiment of the present invention also provides that the light source 2 or the light sources 2, 2' and / or the first beam-shaping optics 3, 3' are designed such that a first or second location-dependent polarization distribution Pi(x,y), P2(x,y) is additionally formed at the focus positions zi, Z2. The light sources 2, 2' can already be correspondingly polarized, which can be the case, for example, if the light sources 2, 2' are lasers, or the beam-shaping optics 3, 3' can impart a corresponding polarization to the light beam 4. In this case, a further dimension can be resolved by corresponding, polarization-dependent detection of the measuring beam 6 by the detectors 8, 8'.In this case, it is conceivable that the second beam-forming optics 7, 7' first splits the measuring beam 6 depending on the polarization (or wavelength) and then depending on the wavelength (or polarization) and feeds it to a corresponding number of detectors 8, 8'.

[0045] Depending on the desired measurement resolution, more than two light sources 2, 2', more than two focus positions zi, Z2 and / or more than two detectors 8, 8' can be used.

[0046] Fig. 3 shows schematic representations of the spectra of light sources 2, 2', 2" according to exemplary embodiments of the device 1 according to the invention. The (normalized) intensity is shown on the ordinate and the wavelength on the abscissa. The spectra therefore show the intensity with which a certain type of light source 2 emits in different wavelength ranges. The spectra are not intended to represent specific light sources 2, but rather different types of light sources 2. The spectra shown are therefore to be understood purely symbolically.

[0047] Fig. 3 a) shows a broadband light source 2 with a continuous spectrum. Certain wavelength ranges may be more strongly represented in the spectrum, visible as weak, local maxima. Overall, however, the light source 2 emits continuously over a wide wavelength range. According to the invention, the various wavelength subranges can be focused in different areas along the beam path (here, for example, in the z-direction). In particular, a specific spectral width of the spectrum in a specific wavelength range corresponds to a specific length of the focus area along the beam path.

[0048] Although Fig. 3 b) also shows a broadband light source 2, here the light source 2 has clearly distinguishable wavelength ranges. A light beam 4 from such a light source 2, which is passed through a conventional converging lens made of glass, is focused at different positions along the beam path axis according to the different wavelengths, depending on the chromatic aberration of the converging lens, which is specified by the Abbe number. Finally, Fig. 3 c) schematically shows a superposition of various monochromatic light sources 2, 2', 2". Each of these light sources 2, 2', 2" emits light essentially only in a narrowly defined wavelength range. Such a light source 2, 2', 2" is, for example, a laser.The wavelength ranges of the light sources 2, 2', 2" can partially overlap, but the main radiation occurs at significantly different wavelengths. In this case, the first beam-shaping optics 3 are preferably designed such that the light from the (here three) light sources 2, 2', 2" is superimposed to form the light beam 4. Furthermore, the first beam-shaping optics 3 are not designed to compensate for chromatic aberration, but are specifically used to create several location-dependent intensity distributions l. m (x,y) at different focus positions z m to generate.

[0049] The illustration in Fig. 4 shows a schematic representation of a first and a second location-dependent intensity distribution h(x,y), l2(x,y) according to an exemplary

[0050] Embodiment of the device 1 according to the invention or of the method according to the invention. The associated device 1 can be designed, for example, as shown in Fig. 1 or as shown in Fig. 2. Shown here are the two location-dependent intensity distributions h(x,y), l2(x,y), as they are formed in planes perpendicular to the beam axis of the light beam 4. Here, the beam axis has again been selected to coincide with the z-axis, so that the intensity distributions h(x,y), l2(x,y) are generated in the xy-plane, each indicated as a rectangle.

[0051] The location-dependent intensity distributions h(x,y), l2(x,y) are indicated here by way of example in an oval shape. The intensity distributions h(x,y), l2(x,y) are clearly visible at two different focus positions zi, Z2 spaced from one another along the z-axis. By interacting a particle 10 with the light beam 4, for example in the region of the intensity distribution h(x,y), a measuring beam 6 is generated which has corresponding position information in its intensity signal, which can be determined by appropriate detection and evaluation. If the particle 10 also has a movement component in the z-direction or moves in an xy-plane spanned at a different z-position than the first focus position zi, corresponding position information can also be impressed on the measuring beam 6 through the interaction with the light beam in the region of the intensity distribution l2(x,y).The two intensity distributions h(x,y) and l2(x,y) differ in the wavelengths of the light. With a corresponding wavelength-specific detection, a distinction can be made between the respective focal positions zi and Z2. Furthermore, the invention also makes it possible to determine the position of particle 10 between the first focal position zi and the second focal position Z2 based on the relative intensity of both signals.

[0052] Finally, Fig. 5 shows a schematic representation of a location-dependent intensity distribution l m (x,y) and a location-dependent polarization distribution P m (x,y) according to an exemplary embodiment of the device 1 according to the invention or the method according to the invention.

[0053] The illustration is merely exemplary and can be used in the manner explained below both at the first focus position zi and the second focus position Z2 (or further focus positions z m ) apply.

[0054] The number m of focus positions depends on the number of different wavelength ranges and / or on the first beam shaping optics 3.

[0055] Here, the first beam-forming optics 3 has given the light beam 4 at the position shown a location-dependent polarization distribution P in addition to the location-dependent intensity distribution lm(x,y) m (x,y) imprinted.

[0056] The location-dependent intensity distribution l m(x,y) is indicated here as essentially elliptical. The ellipse comprises a height h along the vertical axis H (which is chosen here to be parallel to the y-axis) and a width b along the lateral axis B (which is chosen here to be parallel to the x-axis). The height h can be, for example, approximately 3 mm, while the width b can be approximately 50 pm.

[0057] The different polarizations are indicated here as arrows by way of example and vary along the vertical axis H. Preferably, the device 1 is designed to generate a linear polarization that varies along the vertical axis H, particularly preferably in the values ​​0°, 45°, 90°, and 135°. Alternatively, a location-dependent circular polarization can also be used.

[0058] Because in the xy-plane there is now both a location-dependent intensity distribution l m (x,y) as well as a location-dependent polarization distribution P m(x,y) are present (in the case of the embodiment of Fig. 4, for example, a first location-dependent polarization distribution Pi(x,y) and a second location-dependent polarization distribution P2(x,y)), additional information can be resolved. Through intensity-dependent, wavelength-specific, and polarization-specific detection, the position of a particle 10 in the measurement volume 5 can thus be determined in all three spatial directions. If a time-dependent measurement is performed, a movement or speed measurement is also possible.

[0059] In principle, various variants are conceivable for detection. Preferably, the measuring beam 6 is first split into two parts by a corresponding second beam-shaping optics 7, with one part being fed to a wavelength-dependent detector 8 and the other part to a polarization-dependent detector 8'. Alternatively, one part of the measuring beam 6 is fed to a plurality of wavelength-specific detectors 8, and the other part of the measuring beam 6 is fed to a plurality of polarization-specific detectors 8'.

[0060] Another embodiment provides for the measurement beam 6 to be first split based on polarization and then based on wavelength. Conversely, it is also conceivable for the measurement beam 6 to be first split based on wavelength and then based on wavelength. In this case, with n polarization components and m wavelength components (or spectral components), n x m detectors 8 are required.

[0061] The wavelength-dependent as well as polarization-dependent intensity detection of the measuring beam 6 enables a precise and comprehensive characterization of the particles 10 in the measuring volume 5.

[0062] In addition to a position measurement of a particle 10, a size measurement of the particles 10 is also possible with the device 1 according to the invention and the method according to the invention.

[0063] Reference symbol:

[0064] 1 device

[0065] 2, 2', 2" light source(s)

[0066] 3, 3' first beam shaping optics

[0067] 4 light beam

[0068] 5 measuring volumes

[0069] 6 measuring beam

[0070] 7, 7' second beam shaping optics

[0071] 8, 8' detector(s)

[0072] 9 Evaluation unit

[0073] 10 particles h(x,y) first spatially dependent intensity distribution l2(x,y) second spatially dependent intensity distribution zi first focus position

[0074] Z2 second focus position

[0075] H vertical axis h height

[0076] B broad axis b width

[0077] Pi(x,y) first location-dependent polarization distribution

[0078] P2(x,y) second location-dependent polarization distribution

Claims

Patent claims 1. A device (1) for characterizing at least one particle (10) in a measurement volume (5), comprising: at least one light source (2) for emitting at least one light beam (4) along a beam path in the direction of the measurement volume (5), at least one first beam-shaping optic (3, 3') arranged in the beam path in front of the measurement volume, wherein the first beam-shaping optic (3, 3') is designed to form a first location-dependent intensity distribution (h(x,y)) of the light in the measurement volume (5) in a plane perpendicular to the beam path at a first focus position (zi) along the beam path of the light beam (4), and at least one detector (8), wherein the detector (8) is designed to detect at least a portion of the measurement beam (6) generated by reflection and / or scattering of the light by the particle (10) in the measurement volume (5) and to output at least one measured intensity signal to an evaluation unit (9),wherein the evaluation unit (9) is designed to determine a property of the particle (10) within the measuring volume (5) as a function of the intensity signal, characterized in that the first beam-shaping optics (3, 3') are designed to be at least partially wavelength-dependent in order to form at least a second location-dependent intensity distribution (l2(x,y)) of the light in a plane perpendicular to the beam path at a second focus position (Z2) along the beam path of the light beam (4).

2. Device (1) according to claim 1, characterized in that the at least one light source (2) is a broadband light source (2) with a continuous spectrum or a line spectrum, or that the device (1) comprises a plurality of at least substantially monochromatic light sources (2, 2'), in particular lasers, with different wavelength ranges, wherein preferably the first beam-shaping optics (3) is designed to form the light beam (4) in the measuring volume (5) by wavelength-dependent superposition of the light sources (2, 2').

3. Device (1) according to one of the preceding claims, characterized in that the first beam-shaping optics (3) are designed to additionally produce in the measuring volume (5) a first location-dependent polarization distribution (Pi(x,y)) of the light in a plane perpendicular to the beam path at the first focus position (zi) along the beam path of the light beam (4) and to form a second location-dependent polarization distribution (2(x,y)) of the light in a plane perpendicular to the beam path at the second focus position (Z2) along the beam path of the light beam (4).

4. Device (1) according to one of the preceding claims, characterized in that the at least one light source (2) and / or the first beam-shaping optics (3) are designed such that the light beam (4) has a polarization, wherein the polarization varies along at least one direction, in particular in the steps 0°, 45°, 90° and 135°, and / or that the polarization is a circular or elliptical polarization along one direction.

5. Device (1) according to one of the preceding claims, characterized in that the device (1) comprises a second beam-shaping optic (7) arranged in the beam path of the measuring beam (6), wherein the second beam-shaping optic (7) is designed to shape the measuring beam (6) for the at least one detector (8), in particular to focus and / or collimate it, and to split the measuring beam (6) at least depending on the wavelength, in particular also depending on the polarization.

6. Device (1) according to claim 5, characterized in that the second beam-forming optics (7) are designed such that the measuring beam (6) is split and a part is fed to at least one wavelength-specific detector (8), wherein preferably another part is fed to at least one polarization-specific detector (8').

7. Device (1) according to one of the preceding claims, characterized in that the first beam-shaping optics (3) and / or the second beam-shaping optics (7) comprise at least one dichroic mirror, a lens, in particular a cylindrical and / or collector lens with a predetermined chromatic aberration, a prism, an optical grating, a retardation plate, a space-variant polarization converter and / or a diffractive vortex phase plate.

8. Device (1) according to one of the preceding claims, characterized in that the first beam-shaping optics (3) and / or the second beam-shaping optics (7) a lens combination, preferably a lens doublet and / or a lens triplet.

9. Device (1) according to one of the preceding claims, characterized in that the at least one detector (8) comprises at least one photodiode, at least one line camera and / or at least one 2D camera.

10. Device (1) according to one of the preceding claims, characterized in that the at least one light source (2), the light beam (4) formed by the first beam-forming optics (3) and / or the at least one detector (8) is provided so as to be movable relative to the at least one particle (10).

11. A method for characterizing at least one particle (10) with a device (1) according to one of the preceding claims, wherein a first beam-shaping optics (3) forms a first location-dependent intensity distribution (h(x,y)) from a light beam (4) of at least one light source (2) along a beam path of the light beam (4) in a measurement volume (5) in a plane perpendicular to the beam path at a first focus position (zi) along the beam path of the light beam (4), wherein the first beam-shaping optics (3) are designed to be wavelength-dependent in such a way that they form a second location-dependent intensity distribution (l2(x,y)) from the light beam (4) of the at least one light source (2) along the beam path of the light beam (4) in the measurement volume (5) in a plane perpendicular to the beam path at a second focus position (Z2) along the beam path of the light beam (4),wherein at least a portion of the measuring beam (6) generated by reflection and / or scattering of the light on the particle (10) in the measuring volume (5) is detected by at least one detector (8) and at least one measured intensity signal is output to an evaluation unit (9), wherein the evaluation unit (9) determines a property of the particle (10) within the measuring volume (5) as a function of the intensity signal.

12. The method according to claim 11, wherein the first beam-shaping optics (3) are designed to additionally produce in the measuring volume (5) a first location-dependent polarization distribution (Pi(x,y)) of the light in a plane perpendicular to the beam path at the first focus position (zi) along the beam path of the light beam (4) and a second location-dependent polarization distribution (P2(x,y)) of the light in a plane perpendicular to the beam path at the second focus position (Z2) along the beam path of the light beam (4).

13. Method according to one of claims 11 or 12, wherein a second beam-shaping optics (7) splits the measuring beam (6), in particular depending on wavelength and / or polarization.

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