Measurement system and process monitoring methods

Abstract

The invention relates to a method for monitoring a process with a measuring cell (10) and a measuring system with a measuring cell, in particular a flow cell or the like, wherein the measuring cell is designed with a channel (11) for the flow of a liquid medium (12), wherein the measuring system comprises a lighting device (13), a camera device (14) and a processing device for processing image data from the camera device, wherein visible light with a first wavelength or a first wavelength range and light with a second fluorescence-exciting wavelength or a second wavelength range can be emitted by means of the lighting device, through which the liquid medium located in the channel can be guided and detected by means of the camera device, wherein image data of at least one diffraction image and image data of at least one fluorescence image of particles (22) in the liquid medium can be detected by means of the camera device.

Description

[0001] The invention relates to a method for monitoring a process with a measuring cell and a measuring system with a measuring cell, in particular a flow cell or the like, wherein the measuring cell is designed with a channel for the flow of a liquid medium, wherein the measuring system comprises an illumination device, a camera device and a processing device for processing image data of the camera device.

[0002] Such processes and measuring systems are well known and are regularly used to measure particle concentration or other properties of a liquid medium or liquid. A pump is used to pump the liquid medium through a measuring cell or flow cell within which a channel is formed, in order to be able to carry out continuous measurement of the liquid medium. Furthermore, it is known to arrange an illumination device, optionally with optical elements such as lenses, mirrors, beam splitters or the like, on the channel of the measuring cell and to project light or optical radiation through the channel onto a camera device. The camera device is also arranged on the channel opposite the illumination device and can be equipped with the above-mentioned optical elements or a lens.The image data acquired by the camera device is further processed and output as a measurement signal by a processing device. A measured value can be, for example, a concentration of an analyte, an absorption value, a radiation intensity, or the like. Such a measurement system is known, for example, from DE 1020 1003 8428 A1.

[0003] A disadvantage of the known measuring systems and methods is that the measuring cell can become contaminated after prolonged use in a process and has to be replaced. The measuring cell then has to be cleaned and sterilized. However, this carries the risk of unwanted contamination of the process by the measuring cell. Although it is also possible to dispose of the measuring cell and use a new one, measuring cells are comparatively expensive because they are made of high-quality, sterilizable materials and include the lighting device and the camera device. It is therefore also known to construct measuring cells from several separable assemblies in order to enable the replacement of a component of the measuring cell that comprises the channel of the measuring cell.Opposite windows are then formed on the channel and the lighting device and the camera device are provided with optics that are connected to the respective windows.

[0004] In particular, if particles or a particle concentration within a liquid medium flowing through the channel of the measuring cell are to be determined, these particles can be captured using the camera device. The processing device can then determine the particle concentration from the image data from the camera device.

[0005] The disadvantage here is that a comparatively high-quality camera lens is required to capture even very small particles and display them sharply in the camera's image plane. Furthermore, if the particles in the liquid medium differ slightly from one another, it is difficult to classify the different particles from the image data based on a distinguishing feature. This, in turn, requires special optics for the illumination device and the camera device, which is correspondingly expensive.

[0006] The present invention is therefore based on the object of proposing a measuring system and a method for monitoring a process that enables the simple and cost-effective detection of various particles in a liquid medium. This object is achieved by a measuring system having the features of claim 1 and a method having the features of claim 12.

[0007] In the measuring system according to the invention with a measuring cell, in particular a flow cell or the like, the measuring cell is designed with a channel for the flow of a liquid medium, wherein the measuring system comprises an illumination device, a camera device and a processing device for processing image data from the camera device, wherein visible light with a first wavelength or a first wavelength range and light with a second fluorescence-exciting wavelength or a second wavelength range can be emitted by means of the illumination device, can be guided through liquid medium located in the channel and can be detected by means of the camera device, wherein image data of at least one diffraction image and image data of at least one fluorescence image of particles in the liquid medium can be detected by means of the camera device.

[0008] The measuring system according to the invention therefore comprises the measuring cell which is formed with the channel. The liquid medium or a liquid can be passed through the channel. This then makes it possible to use the measuring cell or the measuring system for the continuous or successive monitoring of a process. Furthermore, the measuring system comprises the illumination device and the camera device which are arranged on the channel in such a way that the light from the illumination device can be projected through the channel and detected or recorded by the camera device. In particular, the illumination device is designed to emit visible light with the first wavelength or the first wavelength range and light with the second wavelength which excites fluorescence of particles or the second wavelength range. The first wavelength differs from the second wavelength orThe respective wavelength ranges are designed differently from one another. A wavelength range here is understood to be a wavelength range with a bandwidth of up to 10 nm, up to 30 nm, or up to 60 nm. The respective first and second wavelength ranges can be completely different or at least partially overlap. The camera device is designed to capture image data of the diffraction image and image data of the fluorescence image of the particles in the liquid medium. The diffraction image is generated with the light of the first wavelength or the first wavelength range, and the fluorescence image is generated with the light of the second wavelength or the second wavelength range. The processing device can then process this image data from the camera device and detect particles in the diffraction image and the fluorescence image, for example by means of image processing.This makes it possible to use the measurement system to simultaneously detect different types of particles, or to more reliably detect particles that differ significantly from one another. For example, particles ranging in size from 100 nm to 100 µm can be detected. The processing device can be implemented as a computer capable of executing software, such as image processing software. The processing device can then output a measurement result in the form of a measured value(s). A measured value can, for example, be a particle count.

[0009] The measuring system can comprise a single measuring cell, or the measuring system can comprise two measuring cells, wherein a first measuring cell can have a first illumination device of the illumination apparatus and a first camera device of the camera apparatus, wherein the light having the first wavelength can be emitted by the first illumination device and the image data of the diffraction image can be captured by the first camera device, and wherein a second measuring cell can have a second illumination device of the illumination apparatus and a second camera device of the camera apparatus, wherein the light having the second wavelength can be emitted by the second illumination device and the image data of the fluorescence image can be captured by the second camera device.If the measuring system comprises only one measuring cell, the illumination device can be designed such that light of the first wavelength and the second wavelength can be emitted via a single light source. However, the illumination device can then also be designed with the first illumination device and the second illumination device, which are then integrated together in the one measuring cell. The camera device can also be designed with only one image sensor, which is designed to record the light of the first wavelength and the second wavelength. Alternatively, the camera device can be designed with the first camera device and the second camera device, which then each have their own image sensors and can be integrated in the one measuring cell.If the measuring system comprises two or more measuring cells, these can also be spatially separated from one another and each form the channel for the liquid medium to flow through. The liquid medium can then flow through the first measuring cell and subsequently the second measuring cell, or vice versa. The liquid medium can also fill the channel statically, i.e. not flow through the channel, or only flow through the channel at certain times or fill it statically. The image data of the diffraction image can then be acquired with the first measuring cell and the image data of the fluorescence image with the second measuring cell. In principle, it is then also possible to arrange a number of n measuring cells in such a way that the liquid medium flows through them one after the other in a sequence.The respective lighting devices and camera devices of these measuring cells can be tuned to different wavelength ranges of light in order to cover the largest possible variance of particles to be detected.

[0010] The particles can be polymers, crystals, and / or cells. In principle, these types of particles can be detected in the diffraction image using image processing. These particles can also be detected in the fluorescence image using image processing if they are fluorescent. This is the case if the particles contain substances that can be excited to fluorescence by light of the second wavelength or wavelength range. Nicotinamide adenine dinucleotide (NADH) has been discovered to be a microenzyme found in cells and involved in metabolic reactions. NADH can absorb light of specific wavelengths and can also be selected using fluorescence. Since NADH is a metabolic product, it is also possible to distinguish dead cells from living cells. The fluorescence image can then also be used to detect living cells.

[0011] The camera device can be formed by an image sensor arranged at a window on the channel, wherein the image sensor can be arranged relatively transversely, preferably orthogonally, to the channel, wherein the camera device can be designed without a lens, wherein the illumination device can be arranged at a further window on the channel, directly opposite the window. The measuring cell can be designed with a housing in which the channel runs and in which the window and the further window are formed. The window and the further window can then be directly adjacent to the channel and can each be formed, for example, by a glass plate. The channel in which the liquid medium flows can then be formed between two glass plates, preferably arranged parallel to one another, in the housing of the measuring cell. Furthermore, the image sensor can then be positioned directly adjacent to the window.The use of lenses or other optically refracting media is then no longer necessary. This makes the camera device particularly cost-effective to manufacture. The light emitted by the illumination device can pass through the additional window and the channel onto the image sensor arranged behind the window. Although particles present in the liquid medium cannot then be sharply imaged in an image plane of the image sensor, the mere existence of the particles results in the diffraction pattern, which enables the detection of the particles. Likewise, the image sensor can detect fluorescence of the respective particles within the framework of the fluorescence image without creating a sharp image of the particles.

[0012] The image sensor can be a line chip or an area chip, whereby the image sensor can be an RGB chip or a grayscale chip. The line chip can have up to three sensor lines, for example, for detecting different colors (RGB). The area chip can have more than three sensor lines and can also be designed to detect colors (RGB) or light intensities. The use of an RGB chip enables particularly good differentiation between different wavelengths and thus between signals from the illumination device or the particles. With a grayscale chip, on the other hand, comparatively low light intensities can be easily detected with high resolution.

[0013] The lighting device can be configured with one or two light sources, wherein the light source can be a laser, a laser diode, or a light-emitting diode. The light source(s) can emit light of a single wavelength or a relatively narrow wavelength range. If the lighting device comprises two lighting devices, each lighting device can have a respective light source.

[0014] The illumination device can emit light in the red, green, blue (RGB) and / or ultraviolet (UV) wavelength ranges, preferably in a wavelength range from 220 to 440 nm, and the camera device can capture this light. Particularly preferably, the illumination device can emit light in a wavelength range from 330 to 400 nm. If windows for the illumination device and the camera device are formed on the channel, these windows can also be made of plastic, since the transmittance of plastic windows for light of these wavelengths is comparatively high. The use of quartz glass windows can then be dispensed with. The measuring cell can then be manufactured even more cost-effectively. Furthermore, it has been found that nicotinamide adenine dinucleotide (NADH) has a particularly high absorbance in a wavelength range around 340 nm.This wavelength range is therefore particularly suitable for detecting living cells.

[0015] The illumination device and / or the camera device can be configured with at least one bandpass filter, with a bandwidth of 20 to 40 nm. The bandpass filter is then configured for the light from the illumination device. A further bandpass filter can also be provided to achieve a sharper separation of the wavelength range. If the illumination device has a bandpass filter and the camera device also has a bandpass filter, the bandpass filter of the camera device can have a comparatively larger bandwidth. This makes it possible to capture the strongest possible signal or a large amount of light with the camera device in order to obtain usable image data.

[0016] The first wavelength or first wavelength range can be 435 nm, and the second wavelength or second wavelength range can be 365 nm. A wavelength range is understood here to be a relatively narrow range that includes the specified wavelength. The specified wavelength can be in the center of the wavelength range and / or the wavelength range can have an intensity maximum at the specified wavelength.

[0017] The illumination device can be configured with two optical fibers or fiber bundles, each for illuminating the liquid medium with light of the first wavelength or light of the second wavelength, wherein the fibers can preferably be drawn fibers, or the illumination device can be configured with two apertures, each for illuminating the liquid medium with light of the first wavelength or light of the second wavelength. The optical fibers can be glass fibers into which light from an illumination source of the illumination device can be coupled and output or emitted at one fiber end at the channel. If the fibers are drawn fibers (tapered fibers), a diameter of the respective fiber can be smaller than a wavelength of the light. The light is then guided into a cladding of the fiber, not in a core.In particular, it then becomes possible to generate white light with a high intensity, which can advantageously be captured with the camera device. Alternatively, the illumination device can be designed with apertures for the respective wavelengths. The aperture for projecting the light of the first wavelength or the first wavelength range can have a suitable size for generating diffraction patterns. An aperture can, for example, have a diameter of 200 µm. Furthermore, it can be provided that a diffuser is arranged between a light source and the respective aperture. Such apertures are particularly cost-effective to produce, although a distance must always be maintained between the apertures. With optical fibers, on the other hand, a first light source can be comparatively far apart from a second light source, and light can emerge from the optical fibers even without a significant distance between the fibers being close to one another.The fibers can then also lie directly next to each other with their respective ends.

[0018] A housing for the measuring cell can be formed by injection molding or 3D printing a coolant material, preferably polyetheretherketone (PEEK). The measuring cell can then be manufactured particularly cost-effectively in large quantities. The cost-effective production of the measuring cell would also make it possible to forgo sterilization of the measuring cell and its subsequent use, and to dispose of the measuring cell after its initial use and replace it with a new one. In principle, however, it is also possible to sterilize and reuse the measuring cell. The housing can therefore also be designed to be sterilizable.

[0019] In the method according to the invention for monitoring a process with a measuring cell, in particular a flow cell or the like, of a measuring system, a liquid medium flows through a channel formed in the measuring cell, wherein the measuring system comprises an illumination device, a camera device and a processing device with which image data from the camera device are processed, wherein visible light with a first wavelength or a first wavelength range and light with a second fluorescence-exciting wavelength or a second wavelength range are emitted by means of the illumination device, guided through liquid medium located in the channel and captured by means of the camera device, wherein image data of at least one diffraction image and image data of at least one fluorescence image of particles in the liquid medium are captured by means of the camera device.For the advantages of the method according to the invention, reference is made to the description of the advantages of the device according to the invention.

[0020] The illumination device can emit the light with the first wavelength or the first wavelength range and the light with the second wavelength or the second wavelength range, each continuously or in sequence. In particular, if the illumination device has two illumination devices, the light can be emitted independently of one another, since each of the illumination devices can then have its own light source. If the camera device can also simultaneously capture the light with the first wavelength and the light with the second wavelength or the respective wavelength ranges, continuous recording or measurement of particles present in the liquid medium can take place. Furthermore, the illumination device can also have a single light source with which the light with the first wavelength and the light with the second wavelength or the respective wavelength ranges can be emitted.Then, a successive alternation of light of the first wavelength and light of the second wavelength or wavelength ranges can take place after certain time intervals or at a certain frequency, whereby the camera device can then also capture the respective image data synchronously with this frequency.

[0021] The processing device can determine a spatially resolved diffraction image with the spatial positions of the particles by processing the image data of the diffraction image, wherein the processing device can determine a spatially resolved fluorescence image with the spatial positions of the particles by processing the image data of the fluorescence image. In particular, the processing device can calculate the spatial positions of the particles from the image data of the diffraction image using holographic reconstruction. The diffraction image has diffraction patterns generated by the particles present in the liquid medium. By means of image processing, the existence and position of the respective particles can be determined from the diffraction patterns. For this purpose, the processing device or image processing software can already contain data on a particle size and shape as well as specific diffraction patterns in order to more easily assign a diffraction pattern to a particle.This makes it possible to reconstruct the geometry and position of the particles from the diffraction patterns. It is important that the channel in the area of ​​the camera device is sufficiently narrow or flat so that the particles are located at a short distance relative to an image sensor of the camera device, which allows the generation of diffraction patterns. The distance between the respective windows or a cross-section or height of the channel should be dimensioned such that the height is at least two to three times the height of the particles to be measured. For example, 300 µm to 1 mm, preferably 100 µm to 0.5 mm, particularly preferably 30 µm to 50 µm. Furthermore, the processing device can be used to obtain a spatial position of the fluorescent particles from the image data of the fluorescence image.This can be achieved by selecting differences in brightness, particularly specific areas of comparatively greater brightness in the fluorescence image, and determining each of these as the location of a particle. The determination or calculation of the respective positions of the particles can also be performed using artificial intelligence. In image processing, artificial intelligence in particular makes it possible to obtain a particularly reliable determination of particles from the image data.

[0022] The processing device can superimpose the spatially resolved diffraction image and the spatially resolved fluorescence image based on the particles' corresponding spatial positions. If the camera device captures the diffraction image and the fluorescence image in a temporal sequence, the particles can move in the liquid medium, so that a particle in the diffraction image may appear at a different spatial position in the fluorescence image. Using image processing, the diffraction image and the fluorescence image can be aligned with each other with regard to the particles' spatial positions so that the spatial positions of particles appearing simultaneously in the diffraction image and the fluorescence image match. This can be achieved using image processing or pattern analysis.This makes it possible to determine particles that appear only in the diffraction image or only in the fluorescence image, which also allows different types of particles to be detected.

[0023] The processing device can process the image data successively or continuously, whereby the processing device can determine a number of particles in the diffraction image and / or the fluorescence image. With continuous processing of the image data, the image data is continuously acquired. This is particularly advantageous when the liquid medium flows through the measuring cell and real-time measurement is required. It is also possible to acquire image data successively if only one measurement is required after specific time intervals. In both cases, a number of the respective particles can be determined in the diffraction image and in the fluorescence image. In this case, the measuring system can also have two spatially separate measuring cells, since the spatial position of the particles does not have to be determined solely to determine the number of particles.A more precise differentiation of particles is possible if the number of particles is determined from a spatially resolved diffraction image and a spatially resolved fluorescence image, and the positions of the respective particles in the diffraction image and the fluorescence image are compared. This allows, for example, the number of cells in a liquid medium to be determined, with the diffraction image providing the total number of cells and the fluorescence image providing the number of living cells. Other particles can also be easily differentiated based on their properties.

[0024] The processing device can determine an intensity of a light source of the illumination device with the camera device over a measurement period, wherein the processing device can determine a change in intensity over the measurement period and correct the image data taking the change into account. During a longer measurement period, which can extend over a period of several weeks, a light source can experience a change in intensity. In particular, the intensity or luminance of the light source can decrease, which undesirably affects the reproducibility of a measurement result. Furthermore, the channel can also become dirty, so that less light reaches the camera device from the light source over the measurement period. The camera device can therefore continuously record the luminance of the light source during the measurement period.This can be achieved, for example, by illuminating an image sensor of the camera device directly by the light source in sections, bypassing the channel. In this area, which is comparatively small compared to the surface of the image sensor, the intensity of the light source can be continuously recorded, and the resulting image data can be compared with this reference using the processing device in terms of their intensity or luminance. Image processing can then be used to correct the image data, adapted to a change in intensity. This allows for even more accurate measurement results to be achieved over the long term.

[0025] The medium in the channel can be circulated into a media circuit of a sterile process. The process can be a biological or chemical process, for example, carried out in a reactor or a dedicated container. The media circuit can be connected to the container in such a way that the liquid medium is circulated into the media circuit via a pump or other suitable means, so that the liquid medium reaches the measuring cell connected to the media circuit. This enables continuous monitoring of the process with the measuring system.

[0026] Further advantageous embodiments of the method emerge from the descriptions of the features of the subclaims which refer back to device claim 1.

[0027] A preferred embodiment of the invention will be explained in more detail below with reference to the accompanying drawings.

[0028] They show: Fig. 1 a schematic representation of a measuring cell; Fig. 2 a diffraction pattern; Fig. 3 a fluorescence image; Fig. 4 an image of the diffraction pattern from Fig. 2 and the fluorescence image from Fig. 3 after image processing.

[0029] The Fig. 1 shows a schematic partial representation of a measuring cell 10 in a sectional view, wherein a channel 11 for the flow of a liquid medium 12 is formed in the measuring cell 10. The measuring cell 10 further comprises an illumination device 13 and a camera device 14. The illumination device 13 in this exemplary embodiment is formed from a light-emitting diode 15, a diffuser 16 and a diaphragm 17 with an aperture 18. The camera device 14 is formed by an image sensor 19. The channel 11 is delimited by windows 20 and 21. The image sensor 19 is arranged adjacent to the window 21. The light-emitting diode 15 can emit visible light with a first wavelength or a first wavelength range and light with a second fluorescence-exciting wavelength or a second wavelength range, which can be detected by the image sensor 19. The light-emitting diode 15 switches sequentially between the respective wavelengths orWavelength ranges. Particles 22 are present in the liquid medium 12, where the particles 22 here are living cells 23 and dead cells 24. By illuminating the particles 22 with the illumination device 13, an image is generated on the image sensor 19.

[0030] The Fig. 2 shows an example of a diffraction image 25 with a diffraction pattern 26, which is created by the existence of particles 22 in the liquid medium 12 in the measuring cell 10.

[0031] The Fig. Figure 3 shows a fluorescence image 27 created by the living cells 23 in the liquid medium 12 in the measuring cell 10. The living cells 23 are identified by the light with the fluorescence-exciting wavelength through punctiform areas 28 in the fluorescence image 27 of increased light intensity.

[0032] The Fig. Figure 4 shows the diffraction image 25 and the fluorescence image 26 after image processing and superimposition. The image processing was performed using a processing device (not shown), which, like the measuring cell 10, is part of a measuring system (also not shown). This image processing leads to the Fig. 4, from which the spatial position of living cells 23 is represented by the representation of a point 30 and the spatial position of dead cells 24 is represented by the representation of a point 31. By means of image processing, a number of living cells 23 and dead cells 24 in the liquid medium 12 is thus continuously or successively determined during a flow through the channel 11, preferably relative to a unit of time and / or a volume. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 1020 1003 8428 A1

[0002]

Claims

[1] Measuring system with a measuring cell (10), in particular a flow cell or the like, wherein the measuring cell is designed with a channel (11) for the flow of a liquid medium (12), wherein the measuring system comprises an illumination device (13), a camera device (14) and a processing device for processing image data of the camera device, characterized by that visible light with a first wavelength or a first wavelength range and light with a second fluorescence-causing wavelength or a second wavelength range can be emitted by means of the illumination device, can be guided through liquid medium located in the channel and can be detected by means of the camera device, wherein image data of at least one diffraction image (25) and image data of at least one fluorescence image (27) of particles (22) in the liquid medium can be detected by means of the camera device. [2] Measuring system according to claim 1, characterized bythat the measuring system comprises a measuring cell (10) alone, or that the measuring system comprises two measuring cells, wherein a first measuring cell (10) has a first illumination device of the illumination apparatus (13) and a first camera device of the camera apparatus (14), wherein the light having the first wavelength can be emitted by the first illumination device and the image data of the diffraction image (25) can be captured by the first camera device, and wherein a second measuring cell has a second illumination device of the illumination apparatus and a second camera device of the camera apparatus, wherein the light having the second wavelength can be emitted by the second illumination device and the image data of the fluorescence image (27) can be captured by the second camera device. [3] Measuring system according to claim 1 or 2, characterized by that the particles (22) are polymers, crystals and / or cells (23, 24). [4] Measuring system according to one of the preceding claims, characterized by that the camera device (14) is formed by an image sensor (13) arranged at a window (21) on the channel (11), wherein the image sensor is arranged relatively transversely, preferably orthogonally to the channel, wherein the camera device is designed without a lens, wherein the lighting device (13) is arranged at a further window (20) on the channel, directly opposite the window. [5] Measuring system according to claim 4, characterized by that the image sensor (19) is formed by a line chip or an area chip, wherein the image sensor is formed by an RGB chip or a grayscale chip. [6] Measuring system according to one of the preceding claims, characterized by that the lighting device (13) is designed with one light source or two light sources, wherein the light source is a laser, a laser diode or a light-emitting diode (15). [7] Measuring system according to one of the preceding claims, characterized by that the illumination device (13) emits light in the wavelength ranges red, green, blue (RGB) and / or ultraviolet (UV), preferably in a wavelength range of 220 to 440 nm, and the camera device (14) can detect this light. [8] Measuring system according to one of the preceding claims, characterized by that the illumination device (13) and / or the camera device (14) is formed with at least one bandpass filter, wherein a bandwidth is 20 to 40 nm. [9] Measuring system according to one of the preceding claims, characterized by that the first wavelength or the first wavelength range is 435 nm and the second wavelength or the second wavelength range is 365 nm. [10] Measuring system according to one of the preceding claims, characterized bythat the illumination device is designed with two optical fibers or fiber bundles, each for illuminating the liquid medium with the light having the first wavelength or the light having the second wavelength, wherein the fibers are preferably drawn fibers, or that the illumination device (13) is designed with two apertures (18), each for illuminating the liquid medium (11) with the light having the first wavelength or the light having the second wavelength. [11] Measuring system according to one of the preceding claims, characterized by that a housing of the measuring cell (10) is formed by injection molding or 3D printing of a plastic material, preferably polyetheretherketone (PEEK). [12] Method for monitoring a process with a measuring cell (10), in particular a flow cell or the like, of a measuring system, wherein a liquid medium (12) flows through a channel (11) formed in the measuring cell, wherein the measuring system comprises an illumination device (13), a camera device (14) and a processing device with which image data of the camera device are processed, characterized by that visible light with a first wavelength or a first wavelength range and light with a second fluorescence-causing wavelength or a second wavelength range are emitted by means of the illumination device, guided through liquid medium located in the channel and captured by means of the camera device, wherein image data of at least one diffraction image (25) and image data of at least one fluorescence image (27) of particles (22) in the liquid medium are captured by means of the camera device. [13] Method according to claim 12, characterized by that the lighting device (13) emits the light with the first wavelength or the first wavelength range and the light with the second wavelength or the second wavelength range, each continuously or in a sequence. [14] Method according to claim 12 or 13, characterized by that the processing device determines a spatially resolved diffraction image with spatial positions of the particles (22) by means of image processing of the image data of the diffraction image (25), wherein the processing device determines a spatially resolved fluorescence image with spatial positions of the particles by means of image processing of the image data of the fluorescence image (27). [15] Method according to one of claims 12 to 14, characterized by that the processing device superimposes the spatially resolved diffraction image (25) and the spatially resolved fluorescence image (27) according to matching spatial positions of the particles (22). [16] Method according to one of claims 12 to 15, characterized by that the processing device processes the image data successively or continuously, wherein the processing device determines a number of particles (22) in the diffraction image (25) and / or the fluorescence image (27). [17] Method according to one of claims 12 to 16, characterized by that the processing device determines an intensity of a light source of the illumination device (13) with the camera device (14) over a measuring time period, wherein the processing device determines a change in the intensity over the measuring time period and corrects the image data taking the change into account. [18] Method according to one of claims 12 to 17, characterized by that the medium in the channel (11) is circulated in a media circuit of a sterile process.

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