Measuring device for optical scanning by means of water jet-guided light source radiation

Abstract

The invention relates to a measuring device for the optical analysis of a sample (100), comprising: a light source (HO); a liquid chamber (104) filled with a liquid and having an outlet nozzle (103), wherein the outlet nozzle (103) is configured to release a liquid jet (102) onto the sample (100); at least one optical element (105), which is configured to couple the light from the light source (110) into the liquid jet (102) such that the light propagates substantially towards the sample (100); and an optical measurement and control unit (500), which is configured to detect returning light emanating from the sample (100). The measuring device further comprises a spectrograph, which decomposes the coupled-out returning light into its spectrum and conducts it to the optical measurement and control unit (500), and a hydrophone (107), which is designed to detect sound waves propagating in the liquid chamber (104) and in the liquid jet (102), wherein the optical measurement and control unit (500) is configured to detect a dripping of the liquid jet (102), on the basis of the microphone signals received from the hydrophone (107).

Description

[0001] Measuring device for optical scanning using water jet guided light source irradiation

[0002] The invention relates to a measuring device for the optical analysis of a sample, comprising a light source, preferably a laser light source, a liquid chamber filled with a liquid and having an outlet nozzle, wherein the outlet nozzle is configured to emit a liquid jet onto the sample, at least one optical element configured to couple the light from the light source into the liquid jet such that the light propagates substantially in a direction towards the sample, and an optical measuring and control unit configured to detect a return light emanating from the sample, which light propagates substantially from the sample through the liquid jet, wherein the at least one optical element is configured to decouple the return light from the liquid jet.

[0003] For the non-destructive analysis of the mineralogical composition of rock samples, state-of-the-art optical methods such as fluorescence, Raman, and infrared spectroscopy are used. Raman spectroscopy is a method for investigating the molecular composition of matter. It is based on the Raman effect, a scattering process in which a photon is scattered by a molecule, gaining or losing energy in the process. This energy change is specific to the vibrational modes of the molecule. A portion of the scattered light therefore experiences a frequency shift due to interaction with the molecules in the sample. If the inelastically scattered light is divided into its wavelength components using a spectrograph, the chemical composition (wavenumbers in the fingerprint region 500 cm²) can be determined. 1 up to 1500 cm' 1) or crystalline structure (wavenumbers in the ultra-low frequency region below 200 cm' 1 ) of the solid sample surface. These lines appearing in a Raman spectrum are also called Stokes lines. In contrast to infrared spectroscopy, which is strongly influenced by water and / or moisture in the various states of matter, Raman spectroscopy of water below 3000 cm' 1 practically unaffected: for example, a Raman peak at 1635 cm' 1 in fact hardly recognizable, the spectral peak at 3410 cm' 1 is clearly recognizable, but distinctly outside the fingerprint region.

[0004] Fluorescence spectroscopy is an analytical measurement method for investigating the properties of fluorescent substances based on the emission of light after these substances have been excited with light of a specific wavelength. It allows the determination of the concentration, molecular structure, and dynamics of the sample by measuring the intensity and wavelength of the emitted fluorescent light.

[0005] Infrared spectroscopy is an analytical measurement technique that uses the interaction of infrared radiation with matter to identify and quantify the chemical composition of a sample. This method is based on the observation that molecules absorb infrared radiation at specific wavelengths that are characteristic of their chemical structure. The absorption of infrared radiation leads to the excitation of molecular vibrations, including extensional, bending, and torsional vibrations. The resulting infrared spectra provide detailed information about the molecular composition and structure of the sample.

[0006] For fluorescence or Raman spectroscopy to analyze the mineralogical composition of rock samples, current technology uses portable devices or desktop measuring stations designed to analyze this scattered light. These devices scan and measure small rock samples or longer drill cores at a narrowly defined distance using a microscopy lens.

[0007] In various industrial processes, such as the pharmaceutical, food, and chemical industries, fiber-optic Raman spectroscopic measuring probes are used for continuous process control. These probes guide the excitation radiation to the sample or into the process flow via several optical fibers and measure the scattered light from the sample via a further number of fiber optics at intervals determined by the end optics.

[0008] The water jet guided light radiation is known as light fountain (also called "Daniel Colladon's Light Fountain") and is considered a forerunner of optical fibers such as those used in telecommunications or such fiber optic based measuring probes.

[0009] The underlying principle of total internal reflection (TIR) ​​is used in encapsulated water jet guided light guides from Lumatec® in dental technology or endoscopy to transmit light radiation with high light intensity.

[0010] A device for optical material processing is known in the prior art, for example, from WO 1995032834 A1. By guiding the laser radiation through a liquid jet in a configuration based on the TIR principle, with a nearly constant, high radiation intensity, the working length is significantly increased. Compared to conventional beam focusing, the use of the liquid beam guide eliminates the need for precise control of the working distance between the focusing unit and the workpiece surface to be processed, and no protective glass to protect against contamination is required.

[0011] However, these state-of-the-art processes and devices are geared toward laser material processing. They all operate with fluid pressures well above 10 bar (referred to as a "pressurized fluid jet"), as only minimal material ablation occurs below this pressure.

[0012] The only known fluid for liquid jets at high pressures is water. The addition of abrasives, as in waterjet cutting, is avoided because it would lead to significant nozzle wear. Instead of water and silicone oils, other liquids and (true or colloidal) solutions of substances are used in WO 1995032834 A1.

[0013] In EP 3466597 A1 and EP 3486027 A1, in the described devices for material processing by means of liquid jet-guided laser radiation, the Raman scattered light generated in the liquid jet (in the case of water, a 532 nm laser generates a Raman-Stokes shift into the red) is used to regulate the quality of the liquid jet or the processing of the workpiece.

[0014] Furthermore, Persichetti et al. describe the use of the TIR principle to spectroscopically analyze liquids (using Raman or fluorescence spectroscopy). In this case, the liquid jet itself is the analyte, namely water with organic contaminants, which is being measured (see Persichetti, "High Sensitivity UV Fluorescence Spectroscopy Based On An Optofluidic Jet Waveguide," Optics Express, 2013). The setup features a light source orthogonal to the liquid jet. The light scattered by the analyte is reflected within the water jet based on the TIR principle and guided to an optical waveguide that leads to a spectrometer. This method is intended to replace cuvettes or flow cells and enable better sensitivity without the influence of the containers.

[0015] The disadvantage of conventional Raman spectroscopic scanning optics for rock surveying is that the focus of the laser beam or the measuring point must be adjusted by the scanning optics within a fixed or very fine adjustment range (on the order of micrometers). This generally makes continuous inline measurement difficult with an acceptable throughput of solid, three-dimensional bulk materials conveyed on a conveyor belt.

[0016] Also known in the prior art is WO 2023004504 A1, which shows a system for the spectroscopic analysis of organic tissue that can be used in vivo and ex vivo. The system comprises a light source, a fluid source, and a computing unit. A water jet is generated via a nozzle, which bridges a distance between the system and the sample to be examined and serves as a light guide for the light from the light source. In one embodiment, laser light is fed into a water jet via optical elements and propagates downwards through the water jet towards the sample. As soon as the laser light reaches the sample, the light interacts with the sample via elastic scattering, Raman scattering, fluorescence, etc. This interaction results in scattered light, which propagates upwards through the water jet towards the system via total internal reflection and can be analyzed by the computing unit.

[0017] It is the object of the present invention to provide a measuring device which overcomes at least some of the disadvantages of the prior art.

[0018] This object is achieved by a measuring device according to claim 1. Preferred embodiments are specified in the dependent claims, the description and the drawings.

[0019] The measuring device according to the invention for the optical analysis of a sample comprises a light source, preferably a laser light source, a liquid chamber filled with a liquid and having an outlet nozzle, wherein the outlet nozzle is configured to deliver a liquid jet onto the sample, at least one optical element configured to couple the light from the light source into the liquid jet such that the light propagates substantially in a direction toward the sample, an optical measuring and control unit configured to detect a backlight emanating from the sample, which light propagates substantially from the sample through the liquid jet, wherein the at least one optical element is configured to decouple the backlight from the liquid jet, wherein the measuring device comprises a spectrograph,which decomposes the coupled backlight into its spectrum and directs it to the optical measuring and control unit, wherein the liquid chamber comprises a hydrophone configured to detect sound waves propagating in the liquid chamber and in the liquid jet and to convert them into electrical microphone signals, wherein the hydrophone directs the microphone signals to the optical measuring and control unit, which is configured to detect droplet disintegration of the liquid jet based on the microphone signals received from the hydrophone. The liquid jet directs the light from the light source to the sample based on the principle of total internal reflection. An advantage of the inventive design of the measuring device is that the focus of the laser radiation or the measuring point does not have to be set in a fixed or very fine adjustment range (on the order of micrometers) by the scanning optics. This enables, for example,at least partially, continuous inline measurement at an acceptable throughput of solid three-dimensional bulk materials, which are passed by on a conveyor belt.

[0020] Droplet breakup hinders the light transmission in the liquid jet based on total internal reflection, so it is desirable to detect the breakup and, if necessary, control or prevent it through appropriate control measures. For example, the pressure within the liquid chamber can be adjusted, thereby influencing the laminar flow of the liquid jet. It is also possible to apply an electric field so that the liquid jet becomes electrostatically charged when exiting an electrically insulated nozzle, such as a glass nozzle. This leads, for example, to a deflection of the liquid jet. Even if droplet breakup is not prevented or reduced, detecting the breakup carries the risk of a corresponding measurement being stored as unreliable.

[0021] In a preferred embodiment, the measuring device further comprises a beam splitter and a side-view area detector, wherein the beam splitter branches off the decoupled rear light partially, preferably less than 20%, particularly preferably less than 10%, and feeds it to the side-view area detector. The branched-off part of the rear light is detected by the side-view area detector. The side-view area detector transmits the information about the detected branched-off part of the rear light to the optical measuring and control unit, which is configured to detect a droplet breakup of the liquid jet based on the information received from the side-view area detector. Droplet breakup hinders the light conduction in the liquid jet based on total internal reflection, so it is desirable to detect the droplet breakup and, if necessary, to control or prevent it by appropriate control measures.For example, the pressure within the liquid chamber can be adjusted, thereby influencing the laminar flow of the liquid jet. It is also possible to apply an electric field so that the liquid jet becomes electrostatically charged as it exits an electrically insulated nozzle, such as a glass nozzle. This can, for example, lead to a deflection of the liquid jet. Even if droplet breakup is not prevented or reduced, detecting droplet breakup carries the risk of a corresponding measurement being recorded as unreliable.

[0022] In a preferred embodiment, the measuring device comprises a liquid control unit with a liquid collector and a pump, wherein the pump is configured to pump a liquid from the liquid jet collected in the liquid collector into the liquid chamber. This allows the liquid from the liquid jet to be collected in the liquid collector and fed back into the liquid chamber.

[0023] In a preferred embodiment, the liquid control unit comprises a filter unit located downstream of the liquid collector and upstream of the liquid chamber. This prevents any sample particles from being present in the liquid (re-fed into the liquid chamber) that are detrimental to total internal reflection of light.

[0024] In a preferred embodiment, the outlet nozzle is designed as a glass tube, preferably a glass tube made of borosilicate or quartz glass. Constructing the outlet nozzle as a glass tube represents a particularly simple and uncomplicated design.

[0025] In a preferred embodiment, the outlet nozzle has a length oriented in the direction of flow of the liquid and an inner diameter oriented orthogonally thereto, wherein the length of the outlet nozzle is twice, preferably three times, particularly preferably five times the inner diameter of the outlet nozzle. This particularly promotes the laminar flow of the liquid jet.

[0026] In a preferred embodiment, the outlet nozzle has an enlarged inner diameter on its side facing the liquid chamber. The enlarged inner diameter can be funnel-shaped, for example, but is not limited to this shape. The enlarged inner diameter serves both to minimize flow turbulence in the liquid and to improve the sound wave alignment with the hydrophone.

[0027] In a preferred embodiment, the measuring device further comprises a casing that at least partially encloses the outlet nozzle and protects it from lateral forces. For example, the casing can prevent the glass tube 203 from being damaged by a particularly large sample 100.

[0028] In a preferred embodiment, the liquid is Raman- and / or fluorescence-neutral, preferably filtered and demineralized water and / or distilled water. The neutrality of water as a light medium makes the device particularly suitable for Raman spectroscopic measurements.

[0029] In a preferred embodiment, the fluid in the fluid chamber has a pressure of less than 50 bar, preferably less than 30 bar, and particularly preferably less than 10 bar. The low fluid pressure enables a particularly simple and uncomplicated design with low water consumption. A further advantage is that no special protective measures need to be taken to ensure the safety of users when accessing the measuring field.

[0030] In the prior art, significantly higher pressures are used for material processing, approximately 50 to 1000 bar. This reduces unwanted optical phenomena that occur due to the heating of the liquid jet by the focused light. However, the goal of the invention is to irradiate a sample with light to induce photonic interaction with the sample. The required light output is lower, the unwanted optical phenomena in the water occur to a lesser extent, and thus the liquid does not need to impinge on the sample at high pressure.

[0031] In a preferred embodiment, the diameter of the liquid jet is between 0.1 and 50 mm, preferably between 0.3 and 30 mm, particularly preferably between 0.5 and 10 mm. The larger the diameter of the liquid jet, the better a high light intensity is directed onto a larger part of the sample surface. Three-dimensional surface structures can also be better illuminated. Furthermore, with larger diameters the optical aperture, i.e. the amount of light that can be captured by the measuring device, is increased and thus a better measurement signal is achieved. In general, according to the "Rayleigh Plateau Criterion", it is assumed that a laminar liquid jet is stable as long as its length is approximately 7 to 10 times its diameter. A larger diameter would therefore favor a greater length of the laminar liquid jet.However, the fluid consumption also increases with the diameter. For example, according to the Hagen-Poiseuille law, the volume flow of a fluid through a circular cylindrical tube is proportional to the fourth power of the radius. Therefore, when choosing the diameter, a balance must be struck between a (largest possible) scanning area on the sample and a (minimum possible) fluid consumption.

[0032] In a preferred embodiment, the focus of the light source can be freely selected independently of the sample to be measured. This is advantageous because the focus of the laser beam or the measuring point does not have to be set by the scanning optics within a fixed or very fine adjustment range (on the order of micrometers). This enables, for example, at least partially continuous inline measurement with an acceptable throughput of solid, three-dimensional bulk materials, such as those conveyed on a conveyor belt.

[0033] In a preferred embodiment, the measuring device further comprises a data processing and control unit that communicates with the optical measuring and control unit and / or with the liquid control unit and transmits the measured data to a human-machine interface. This allows the result of the spectrographic analysis of a sample to be displayed to a user.

[0034] In a preferred embodiment, the invention provides a system comprising a measuring device and a conveying device, preferably a conveyor belt, a vibrating conveyor, a screw conveyor, or a chute. The conveying device is configured to transport a sample into a measuring area of ​​the measuring device, within which the sample is captured by the liquid jet, and subsequently transport the sample out of the measuring area. This enables continuous inline measurement of various samples.

[0035] In a preferred embodiment, the opening direction of the outlet nozzle of the measuring device forms an angle of between 0° and 90° with the surface normal of the conveying device. This embodiment allows a sample to be captured by the liquid jet from different angles. If, for example, the samples exhibit excessive size variability, the distance between the outlet nozzle and the sample may be too great for a particularly small sample, resulting in droplets disintegrating. In this case, all samples could be captured from the side by the liquid jet, which must overcome a substantially constant distance between the outlet nozzle and the sample. Advantageous and non-limiting embodiments of the invention recited in the claims are explained in more detail below with reference to the drawings.

[0036] Fig. 1 shows a generic device from the prior art.

[0037] Fig. 2 shows a schematic representation of the measuring device according to the invention.

[0038] Fig. 3 shows the optical scanning unit.

[0039] Fig. 4 shows the fluid control unit.

[0040] Fig. 5 shows an outlet nozzle with a light-coupling liquid chamber.

[0041] Fig. 6 shows droplet disintegration in case of a liquid jet that is too long.

[0042] Fig. 7 shows the detection of droplet disintegration using a hydrophone and a side-view area detector.

[0043] Fig. 8 shows alternative embodiments of the opto-fluidic sensing unit.

[0044] Fig. 1 shows a device for optical scanning based on a prior art Raman spectrograph 1. The light from the laser light source 2 is transmitted to several probe heads 4, 5, 6, and 7 via an excitation fiber optic 3. The backscattered light is transmitted to the input optics of the Raman spectrograph 1 via a backscatter fiber optic 8. For example, a Raman microscope is connected to the probe head 4, a contactless optic to the probe head 5, and various immersion optics to the probe heads 6 and 7.

[0045] Fig. 2 shows a schematic structure of the measuring device according to the invention. The measuring device comprises an optofluidic sensing unit 200, a fluid control unit 300, and a data processing unit 400. The data processing unit 400 further comprises a data processing and control unit 700 and a human-machine interface (HMI) 800. In the embodiment shown, both the optofluidic sensing unit 200 and the fluid control unit 300 communicate with the data processing unit 400. Furthermore, the optofluidic sensing unit 200 communicates with the fluid control unit 300 (see the description of Fig. 4).

[0046] Fig. 3 shows the optofluidic scanning unit 200 from Fig. 2 of an embodiment of the measuring device according to the invention, as well as a sample 100 to be examined. The sample 100 can, for example, be a rock sample made of bulk material. The sample 100 is conveyed to the optofluidic scanning unit 200 via a transport device 101 and scanned in a liquid jet 102 using a water jet-guided light beam. The transport device 101 can be designed, for example, as a conveyor belt, vibrating conveyor, screw conveyor, or chute. In a preferred embodiment, the transport device 101 is formed from a wire mesh or rollers to enable the liquid from the liquid jet 102 to flow away.

[0047] In the simplest case, the opto-fluidic scanning unit 200 comprises a light source 110, preferably a laser light source, a liquid chamber 104 filled with a liquid and having an outlet nozzle 103, a spectrograph, and an optical measuring and control unit 500.

[0048] In a preferred embodiment, the liquid is Raman- and / or fluorescence-neutral, preferably filtered and demineralized water and / or distilled water. The liquid has a pressure in the liquid chamber 104 of less than 50 bar, preferably less than 30 bar, particularly preferably less than 10 bar. The liquid jet 102 emerging from the liquid chamber 104 has a diameter of between 0.1 and 50 mm, preferably between 0.3 and 30 mm, particularly preferably between 0.5 and 10 mm.

[0049] The outlet nozzle is configured to discharge the liquid in the liquid chamber 104 to the outside in the form of a liquid jet 102. Preferably, the liquid jet 102 flows out essentially through laminar flow. The liquid chamber 104 is further configured to couple the light from the light source 110 into the liquid jet 102 through at least one optical element 105.

[0050] In the embodiment shown, the outlet nozzle 103 is designed as a glass tube 203, preferably as a glass tube made of borosilicate or quartz glass, wherein the length of the outlet nozzle 103 is at least twice, preferably three times, and particularly preferably five times, the inner diameter of the outlet nozzle 103. This is particularly beneficial for a laminar flow of the liquid jet 102. The glass tube 203 also has an enlarged inner diameter on its side facing the liquid chamber 104. The enlargement of the inner diameter can, for example, be funnel-shaped, but is not limited to this shape. The enlarged inner diameter serves, on the one hand, to minimize flow turbulence in the liquid and, on the other hand, to improve the sound wave alignment to the hydrophone 107.

[0051] The glass tube 203 is further surrounded by a casing 202. The casing 202 at least partially encloses the glass tube 203 and protects it from lateral forces. For example, the casing can prevent the glass tube 203 from being damaged by a particularly large sample 100.

[0052] Based on the principle of total internal reflection (TIR), the light is guided within the liquid jet 102. When the liquid jet 102 hits the sample 100, the light from the light source 110 is also directed onto the sample 100. The interaction between the light incident on the sample 100 and the sample 100 results in secondary radiation, which propagates away from the sample in the form of backlight. A portion of the backlight is guided back in the liquid jet 102 toward the optical fluidic scanning unit 200, again based on the principle of total internal reflection. The backlight includes Raman-scattered light, fluorescence radiation, and / or light excluding those wavelengths that were absorbed by the sample 100 due to light absorption. The backlight is guided in the opto-fluidic scanning unit 200 to the spectrograph, which decomposes the backlight into its spectrum and guides it to the optical measuring and control unit 500.In a preferred embodiment, the optical measuring and control unit 500 receives the information about the spectrally resolved rear light and forwards this information to a data processing unit 400.

[0053] The coupling optics 105 may further comprise an entrance lens 106. Alternatively, the coupling optics 105 may also consist of a single lens. The coupling optics 105 is arranged between the optical part of the optical scanning unit 200 and the fluidic part of the liquid chamber 104.

[0054] In the embodiment shown, the liquid chamber 104 further comprises a hydrophone 107. The hydrophone 107 is designed to detect sound waves propagating in the liquid jet 102 and in the liquid chamber 104. This makes it possible to obtain information about the quality of the water jet. In a preferred embodiment, the hydrophone 107 can be used to detect droplets in the water jet. For this purpose, the hydrophone 107 transmits the information about the detected sound waves to the optical measuring and control unit 500, which is configured to detect droplets in the liquid jet 102 based on the information received from the hydrophone 107 (see Fig. 7). In the embodiment shown, the signal from the hydrophone 107 is processed by an audio signal interface unit 122 and transmitted to the optical measuring and control unit 500.In the embodiment shown, the optofluidic scanning unit further comprises beam-shaping optics 109 and a 45° dichroic beam splitter 108. The beam-shaping optics 109 direct the light from the light source 110 to the 45° dichroic beam splitter 108, which subsequently fulfills two tasks. On the one hand, the 45° dichroic beam splitter 108 directs the light from the light source 110 to the coupling optics 105, which directs the light into the liquid jet 102. On the other hand, the 45° dichroic beam splitter 108 allows the return light to be directed to the spectrograph.

[0055] A further beam splitter 111 splits the rear light into the rear light, which is preferably predominantly directed to the spectrograph, and a preferably small, branched portion of the rear light, which is detected via a side-view optics 112 at a side-view area detector 113. The branched portion of the rear light preferably comprises less than 20%, particularly preferably less than 10%, of the rear light entering the beam splitter 111. The side-view area detector 113 transmits the information about the detected branched portion of the rear light to the optical measuring and control unit 500, which is further configured to detect droplets of the liquid jet (112) based on the information received from the side-view area detector 113 (see Fig. 7).

[0056] After the beam splitter 111, the return light is directed to the spectrograph. In the embodiment shown, the spectrograph comprises a mirror 114, an optical filter 115, a focusing lens 116, a slit 117, a collimator lens 118, a dispersive optic 119, a focusing lens 120, and an area detector 121. Alternative designs for the spectral analysis of light are well known to those skilled in the art.

[0057] The optical filter 115 can be designed as a high-pass filter (suitable for Raman stroke spectra) or as a low-pass filter (suitable for Raman anti-stroke spectra). Furthermore, the dispersion optics 119 can be designed as diffractive (based on light diffraction) or refractive (based on light refraction).

[0058] Fig. 4 shows a preferred embodiment of a liquid control unit 300 that enables a fluidic circuit in the measuring device. A fluidic circuit according to the following description is preferred, but not absolutely necessary. For example, liquid could alternatively be supplied via an external feed. The fluidic circuit begins with a liquid collector 301, in which liquid from the liquid jet 102 collects after it has hit the sample 100. The liquid is cleaned in a filter unit 302 and pumped into a water tank 304 by a pump 303. From there, the liquid is introduced into the light-coupling liquid chamber 104 at a slight (preferably less than 10 bar) overpressure via a metering pump 305 and a check valve 306. The liquid level in the water tank 304 and the metered quantities of the metering pump 305 are controlled by a fluid control unit 600.The liquid in the liquid chamber 104 is discharged to the outside via the outlet nozzle 103 in the form of a liquid jet 102 and strikes the sample 100, whereby the cycle can begin again.

[0059] Fig. 5 shows an enlarged view of the liquid chamber 104 and the sample 100. In the embodiment shown, the liquid chamber has an inlet 201, a coupling optic 105, a hydrophone 107, and an outlet nozzle 103. The outlet nozzle is designed as a glass tube 203, which is protected from lateral forces by a casing 202. The inlet 201 receives liquid from the metering pump 305 (see Fig. 4) and directs the liquid into the liquid chamber 104. For a more detailed description of the components shown and their operation, please refer to the description of Fig. 3.

[0060] Fig. 6 shows an embodiment of the measuring device in which the sample 100 is arranged too far away from the outlet nozzle 103. This results in the liquid jet 102 breaking up at the end of the liquid jet 102 facing away from the outlet nozzle 103. The laminar flow of the liquid jet 102 can be maintained over a certain length. In the embodiment shown, breaking up occurs at lengths of the liquid jet 102 of approximately 5 cm or more. This hinders the light transmission in the liquid jet 102 based on total internal reflection. In order to detect and / or control breaking up of the liquid jet 102, i.e., to take appropriate control measures, two measuring methods are provided in a preferred embodiment. On the one hand, a hydrophone 107 can be provided in the liquid chamber, which can detect breaking up of the liquid jet 102 via sound waves propagating in the liquid.Alternatively or additionally, a beam splitter 111 and a side-view area detector 113 can be provided in the optofluidic scanning unit 200. The side-view area detector 113 detects the measurement spot at the end of the liquid jet 102 and can make statements about the validity of the measurement based on its shape, blur, and uniformity. Fig. 7 shows the two measurement methods described above for detecting droplet breakup of the liquid jet 102. If no breakup occurs, the hydrophone 107 measures the first spectrogram 107a shown at the bottom left. With essentially laminar flow, the hydrophone 107 therefore receives few or hardly any sound waves propagating in the liquid. In this case, the side-view area detector 113 measures a round, sharp, uniform first image 113a of the cross-section of the liquid jet 102.

[0061] However, if droplet breakup occurs, the hydrophone 107 measures the second spectrogram 107b shown at the bottom right. Here, the hydrophone 107 detects a multitude of sound waves propagating within the liquid, which indicates droplet breakup. Likewise, the side-view area detector 113 measures a blurred, irregular second image 113b of the cross-section of the liquid jet 102, where the drops and / or air bubbles 210 formed by the droplet breakup are visible.

[0062] Fig. 8 shows a further preferred embodiment of the measuring device according to the invention, wherein the opening direction of the outlet nozzle 103 can enclose an angle of substantially between 0° and 90° with the surface normal of the conveying device 101. The deflection or the breakup length of the liquid jet 102 can be varied via the pressure of the liquid before entering the outlet nozzle 103. For a more detailed description of the components shown and their operation, reference is made to the description of Fig. 3.

Claims

Patent claims 1. A measuring device for the optical analysis of a sample (100), comprising a light source (110), preferably a laser light source, a liquid chamber (104) filled with a liquid and having an outlet nozzle (103), wherein the outlet nozzle (103) is configured to emit a liquid jet (102) onto the sample (100), at least one optical element (105) configured to couple the light from the light source (110) into the liquid jet (102) so that the light propagates substantially in a direction toward the sample (100), an optical measuring and control unit (500) configured to detect a backlight emanating from the sample (100) and propagating substantially from the sample (100) through the liquid jet (102), wherein the at least one optical element (105) is configured to decouple the backlight from the liquid jet (102), wherein the measuring device comprises a spectrograph,which decomposes the coupled-out rear light into its spectrum and directs it to the optical measuring and control unit (500), characterized in that the liquid chamber (104) comprises a hydrophone (107) which is designed to detect sound waves propagating in the liquid chamber (104) and in the liquid jet (102) and to convert them into electrical microphone signals, wherein the hydrophone (107) directs the microphone signals to the optical measuring and control unit (500), which is configured to detect a droplet disintegration of the liquid jet (102) based on the microphone signals received from the hydrophone (107).

2. Measuring device according to claim 1, wherein the measuring device further comprises a beam splitter (111) and a side-view area detector (113), wherein the beam splitter (111) branches off the coupled-out rear light partially, preferably less than 20%, particularly preferably less than 10%, and feeds it to the side-view area detector (113), wherein the branched-off part of the rear light is detected by the side-view area detector (113), wherein the side-view area detector (113) passes the information about the detected branched-off part of the rear light to the optical measuring and control unit (500), which is configured to detect a dropletization of the liquid jet (112) based on the information received from the side-view area detector (113).

3. Measuring device according to claim 1 or 2, wherein the measuring device comprises a liquid control unit (300) with a liquid collector (301) and a pump (303), wherein the pump (303) is configured to pump a liquid of the liquid jet (102) collected in the liquid collector (301) into the liquid chamber (104).

4. Measuring device according to claim 3, wherein the liquid control unit (300) comprises a filter unit (302) arranged downstream of the liquid collector (301) and upstream of the liquid chamber (104).

5. Measuring device according to one of claims 1 to 4, wherein the outlet nozzle (103) is designed as a glass tube (203), preferably as a glass tube made of borosilicate or quartz glass.

6. Measuring device according to one of claims 1 to 5, wherein the outlet nozzle (103) has a length oriented in the flow direction of the liquid and an inner diameter oriented orthogonally thereto, wherein the length of the outlet nozzle (103) is twice, preferably three times, particularly preferably five times as large as the inner diameter of the outlet nozzle (103).

7. Measuring device according to one of claims 1 to 6, wherein the outlet nozzle (103) has an enlarged inner diameter on its side facing the liquid chamber (104).

8. Measuring device according to one of claims 1 to 7, wherein the measuring device further comprises a casing (202) which at least partially encloses the outlet nozzle and protects it from lateral forces.

9. Measuring device according to one of claims 1 to 8, wherein the liquid is Raman and / or fluorescence neutral, preferably filtered and demineralized water and / or distilled water.

10. Measuring device according to one of claims 1 to 9, wherein the liquid in the liquid chamber (104) has a pressure of less than 50 bar, preferably less than 30 bar, particularly preferably less than 10 bar.

11. Measuring device according to one of claims 1 to 10, wherein the diameter of the liquid jet (102) is between 0.1 and 50 mm, preferably between 0.3 and 30 mm, particularly preferably between 0.5 and 10 mm.

12. Measuring device according to one of claims 1 to 11, wherein the focus of the light of the light source (110) can be freely selected independently of the sample (100) to be measured.

13. Measuring device according to one of claims 1 to 12, wherein the measuring device has a data processing and control unit (700) which communicates with the optical measuring and control unit (500) and / or with the liquid control unit (300) and transmits the measured measurement data to a human-machine interface (800).

14. System comprising a measuring device according to one of claims 1 to 13 and a conveying device (101), preferably a conveyor belt, a vibrating conveyor, a screw conveyor or a chute, wherein the conveying device (101) is configured to bring a sample (100) into a measuring area of ​​the measuring device, within which the sample (100) is detected by the liquid jet (102), and to then transport the sample (100) out of the measuring area.

15. System according to claim 14, wherein the opening direction of the outlet nozzle (103) of the measuring device encloses an angle between 0° and 90° with the surface normal of the conveying device (101).

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