FR2998966A1 - PROBE FOR OPTICAL MEASUREMENTS IN TURBID ENVIRONMENT, AND OPTICAL MEASURING SYSTEM IMPLEMENTING THIS PROBE. - Google Patents

Abstract

The present invention relates to an optical measuring probe device for performing spectrometric and / or photometric measurements in a fluid, comprising a body (2), at least a first and a second limb (4, 5) extending at the end said body (2) in its extension and delimiting a measurement cavity, a plurality of optical fibers (23) inserted in said body (2), and optical coupling means (11, 12, 22) capable of transmitting light between at least a portion of said optical fibers (23) and the measuring cavity. The invention also relates to a measurement system implementing the probe.

Description

The present invention relates to a probe for performing optical measurements, in particular for scattering, for Raman spectroscopy and for fluorescence measurements, in the case of optical measurements. fluids of a more or less complex nature (monophasic or multiphasic fluids such as comprising particles in suspension, foams or emulsions, etc.). It also relates to a system and measurement methods using such a probe. The field of the invention is more particularly, but not exclusively, that of optical fluid characterization techniques. STATE OF THE PRIOR ART Spectroscopy (UV, Visible, Infrared, Medium Infrared and Raman), fluorescence and more generally optical measurements of diffusion (for example particle size distribution) and of absorbance are commonly used techniques for the analysis of solid and liquid products. These techniques make it possible in particular to characterize complex fluids, such as liquid / liquid, liquid / solid, liquid / gas or solid / gas mixtures. They find applications in various fields, such as the control of crystallization processes, dilutions, colloidal mixtures, or in biotechnology, for monitoring cell growth, etc.

We usually distinguish: - Chemical type characterization techniques, which aim in particular to identify or assay compounds or molecules. In general, these are techniques based on spectroscopic, fluorescence, Raman type analyzes, etc. - physical type characterization techniques, which are intended to characterize physical properties of the medium such as turbidity, or the particle size (laser particle size). The characterization or optical measurement systems which implement these techniques generally comprise one or more light sources, detection means (spectrometers, cameras, etc.) and probes for taking the measurement in one or more light sources. the environment to be analyzed. These probes have the function of illuminating or irradiating the medium to be analyzed, and of collecting light from this medium in terms (orientation, distance, ...) that depend on the application. They must also be able to fit into production or laboratory equipment, especially when used for on-line monitoring or control. Various types of probe are thus known, with geometries and optical configurations adapted to particular measurement environments and specific desired quantities. For example: - if the product or the fluid to be analyzed is very turbid, the measurements are generally carried out in backscatter. The illumination of the medium and the collection of light are performed on the same side, and the measurement is therefore made at an angle of 180 degrees with respect to the illumination direction; if the product or the fluid to be analyzed is clear, the measurements are generally made in transmission through a thickness of product, with a measurement point facing the illumination source. The measurement is therefore performed at an angle of zero degrees with respect to the illumination source and with an optical path adapted to the absorption level of the product (typically 2 or 5 mm); if the turbidity of the product or of the fluid to be analyzed changes significantly during the process, the two preceding techniques do not make it possible to fully follow the evolution of the product over time. For this purpose we use transflexion probes: a mirror is placed in front of the light source and the measurement is close to the light source at 180 degrees. If the fluid is clear, the measurement is done through reflection on the mirror. If the fluid is not clear, the measurement is done directly backscattering. This technique nevertheless has the disadvantage of not making it possible to distinguish whether the information comes from the liquid or the solid; to characterize the turbidity of complex fluids, the measurement is generally carried out with a receiver placed at a 90-degree angle with respect to the illumination source; For characterizing distributions or measuring particle sizes, probe configurations are encountered with several receivers placed at different angles to the illumination source (0, 5, 90, 160, 180, ...). degrees) depending on the desired sensitivity to small or large particles; probes with several receivers placed at different angles or distances from the illumination source can be used to perform spatially resolved spectroscopy measurements. By using the theory of multiple diffusion, for example, one can then determine the physical properties from the calculation of a diffusion coefficient, thus separating the chemical effect. The configurations of probes with several detectors distributed at different angles are generally large, which makes their implementation difficult in production environments on small diameter pipes or in reactors or fermenters. In addition, reactors or fermentors generally have ports for inserting instrumentation that have a standardized diameter of 1 inch (25.4 mm) or 1/2 inch (12.7 mm). The use of larger diameter probes therefore requires expensive adaptations.

US Pat. No. 7,319,522 to Havard et al. which describes a system for performing spectroscopic and turbidity measurements. This document describes two probe configurations: a first configuration with a light source and detectors placed at the end of the probe to perform backscattering measurements (180 degrees) under high turbidity conditions; and a second configuration with a lateral notch-shaped measurement area on the probe body, and detectors placed at 90 degrees and zero degrees of the light source, respectively. This probe has several drawbacks: it does not make it possible to carry out measurements without modification of the probe in a very wide range of turbidity values; - The transmission measurement area is not at the end of the probe, which has drawbacks in terms of size. In addition, this configuration is conducive to fouling; Finally, this type of geometry limits the possibilities of measuring configuration, since it is difficult to multiply the measuring points with a measuring zone in the form of a lateral notch on the body of the soda. In general, the known probes are limited to particular measurement configurations, and therefore require the use of several probes to perform various measurements. An object of the present invention is to provide a measurement probe of small size, which solves disadvantages of the prior art. Another object of the present invention is to provide a measurement probe suitable for taking measurements over a wide range of turbidity conditions. Another object of the present invention is to provide a measurement probe which allows a wide variety of measurement configurations, and which can be reconfigurable. SUMMARY OF THE INVENTION These objectives are achieved with an optical measuring probe device for performing spectrometric and / or photometric measurements in a fluid, comprising a body adapted to be immersed in said fluid, characterized in that it comprises furthermore: - at least a first and a second limb extending at the end of said body in its extension and delimiting a measurement cavity, - a plurality of optical fibers inserted in said body and able to be connected to optical means for illumination and / or detection, optical coupling means capable of transmitting light between at least a portion of said optical fibers and the measurement cavity, comprising (i) first optical coupling means opening into the cavity of measuring at the first branch, (ii) second optical coupling means opening into the measurement cavity at the second branch, and (iii) third optical coupling means opening into the measurement cavity at the bottom of said cavity. The optical fibers may be multimode fibers or monomode fibers, depending on the applications. They can all be identical, or different depending on the signals they must convey. They may be composed of separate fibers and / or, at least partially, of fibers grouped in the form of fiber bundles or "bundles" in English. The probe according to the invention may furthermore comprise optical connection means for connecting the optical fibers to the optical illumination and / or detection means. Thus, the same probe can easily be connected to different light sources and / or different detectors, according to different configurations. This flexibility of use is made possible by the use of optical fibers to move the active components (sources and detectors) outside the probe.

The probe according to the invention may further comprise fin-shaped branches making it possible to control a flow of liquid flowing in the measurement cavity, so as to make it substantially laminar and to compress it in order to reduce the parasitic effect of the gas bubbles. The measurement cavity is positioned at the end of the body, between the two branches. With this configuration, the probe of the invention is particularly well suited to perform measurements in a stream. The disturbances of the flow in the measurement zone due to the presence of the body are minimized, by comparison in particular with probes of the prior art with a measurement zone which has the shape of a lateral notch.

This configuration also makes it possible to optimize the shape of the branches to control the flow in the measurement zone, and to make sure that the fluid that is measured is as representative as possible of all the fluid circulating around the probe. Finally, probe configuration makes it possible to carry out measurements with stops of fluid agitation, for example to evaluate settling or phase separation times. Indeed, considering that the probes are generally arranged vertically, with conventional probes that have a measuring zone in the form of a lateral notch on the body of the probe, a deposit phenomenon appears on the window located down the reactor. On the contrary, with the probe according to the invention, the particles can flow freely towards the bottom of the reactor without being deposited on the probe. In addition, measurements can be made at different depths, for example by moving the probe, in order to calculate a diffusion / absorption gradient without risk of fouling of this probe. According to embodiments, the body of the probe according to the invention may have a diameter of less than 26 mm, or even less than 16 mm. Thus, it can be shaped so that it can be inserted into a fermentor or bioreactor port of diameter 1 inch (2.54 cm), or even in a diameter port 1/2 inch (1.27 cm) . The probe according to the invention can thus be of small diameter and easily integrable in a measurement environment, thanks in particular to the use of the optical fibers to transport the signals and to the disposition at the end of the measuring cavity. The probe according to the invention may comprise a body of circular section or of any other section that fits in a reduced diameter if necessary. This body can be of any length. It can be for example very short, for example of the order of a centimeter, to allow measurements in a small space such as a pipe. It can also be lengthened, for example with a length greater than ten centimeters, to allow a sufficiently distant measurement of a wall to avoid disturbances due to agitation against this wall, or to allow measurements at different depths. by moving the probe. According to embodiments, the probe according to the invention may have a measurement length in the measuring cavity which is suitable for carrying out measurements in media with turbidity greater than 1000 NTU. According to embodiments, the probe according to the invention may have a measuring length in the measurement cavity which is suitable for carrying out measurements in media with a turbidity greater than 10000 NTU. The measurement length corresponds to the length of the path of the light in the fluid, in the cavity or more precisely between the interfaces of the first and second optical coupling means with the fluid. It is recalled that the UTN (Nephelometric Turbidity Unit - NTU) is a standardized unit of measurement of turbidity obtained by a nephelometric technique, that is to say by an optical technique. consisting of measuring the light scattered at 90 degrees of angle with respect to the incident light. For example, a turbid water has a turbidity of about 50 NTU or more, and the milk has a turbidity of the order of 10,000 NTU. Knowing that the intensity of light decreases exponentially with the propagation distance in a turbid medium, in order to be able to measure in high turbidity media, it is necessary to limit the distances between the light source and the detectors. . However, in order to be able to use small measurement distances, it is necessary to be able to limit the size of the light sources and the detectors, for reasons of mechanical size and to limit the solid angles of capture. This is made possible in the invention by the use of optical fibers which make it possible to overcome, at the level of the probe, the geometric and congestion constraints related to sources and detectors. According to embodiments, the probe according to the invention can be used in very wide turbidity ranges, from less than 200 NTU to more than 10,000 NTU. This is possible for example with a measurement cavity whose length is of the order of 2 to 5 mm. In the case of very low concentration of particles, the phenomena is limited to simple diffusion. The probe can then be used to perform laser particle size measurements (Fraunhofer theory and particle size above 100 μm). Fibers for measuring at many different angles. According to embodiments, the probe according to the invention may have a measurement length in the measuring cavity which is variable along the first and second branches. This variable measuring length makes it possible to simultaneously generate optical paths of different length in the fluid. It can be obtained with first and second branches that are not parallel in the measuring cavity. In some embodiments, the first and / or second optical coupling means may include a right angle reflector and a window of at least partially transparent material. The windows of the first and / or second optical coupling means may be of variable thickness and / or be inserted into the first and second branches so that their respective faces in contact with the fluid are not parallel. . This makes it possible to obtain measurement lengths which vary according to the position relative to their surface. According to embodiments, the first, second and / or third optical coupling means may further include: at least one lens or a microlens of collimation or focusing; at least one filter, for example of the band-pass or notch type, placed in front of at least a portion of the optical fibers in order to block parasitic wavelengths (Raman laser or UV excitation). This or these filter (s) may in particular be included for performing Raman or UV spectroscopy measurements. This configuration allows maximum compactness. The optical fibers can follow the shape of the body to the immediate vicinity of the measuring cavity and it is not necessary to impose small radii of curvature on them. In addition, the transparent windows can be of a calibrated thickness to precisely adjust the length of the measurement zone in the fluid, regardless of the length of the measuring cavity between the two branches. The probe may further include means for easily changing these windows. According to embodiments, the body of the probe according to the invention may comprise separable parts including: a first part including the optical fibers, and a second part comprising the first and second branches and the measuring cavity, and including optical coupling means. In this way, measuring cavities with different geometrical or optical characteristics can easily be mounted on the same probe, or, alternatively, a bundle of optical fibers controlling a measurement cavity can be replaced. In addition, the probe may comprise fixing means (to the bioreactor or the pipe for example) integral with the first part. In this case, the body can simply separate into two parts. The probe may also comprise fixing means (to the bioreactor or the pipe for example) integral with the second part. In this case, the first part with the optical fibers can be inserted into the second part which serves as a sleeve. This makes it possible to change the rear part of a probe by leaving the part with the measuring cavity integral with the enclosure or the pipe on which it is fixed, for example to carry out other types of measurement while minimizing the risks of contamination since the seal is not broken. According to embodiments, the probe according to the invention may further comprise a first central optical fiber having an end coupled with the first optical coupling means, and a second central optical fiber having an end coupled with the second optical coupling means. , which first and second central optical fibers defining an optical measurement axis in the cavity. These first and second central optical fibers may for example be used to perform measurements in transmission along the optical axis.

The probe according to the invention may further comprise: at least one lateral optical fiber having an end coupled with the first optical coupling means and placed near the end of the first central optical fiber, and / or at least one a side optical fiber having an end coupled with the second optical coupling means and placed near the end of the second central optical fiber. Such a lateral optical fiber may for example be used to perform backscattering measurements at 180 degrees. The probe according to the invention may further comprise: at least two lateral optical fibers having an end coupled with the first optical coupling means, said ends being placed substantially equidistant from the end of the first central optical fiber, and / or - at least two lateral optical fibers having an end coupled with the first optical coupling means, which ends are placed substantially equidistant from the end of the second central optical fiber. Such pairs of lateral optical fibers may in particular be used to carry out homogeneity measurements in transmission or backscattering. Indeed, differences in measurements at the same angles and at the same distances relative to an illumination fiber are representative of inhomogeneities present in the fluid. According to embodiments, the probe according to the invention may further comprise: a plurality of optical fibers having an end coupled with the third optical coupling means, said ends being arranged along at least one line extending between the first and the second branches; a plurality of optical fibers having an end coupled with the third optical coupling means, which ends are arranged along two lines extending between the first and second branches. The third optical coupling means may further comprise at least one cylindrical lens. The two lines can be confused or side by side. They can be substantially parallel. With respect to illumination from a first or second central optical fiber, these optical fibers coupled with the third optical coupling means may be used to make measurements with varying angles depending on their position. They can also be used to make particle imaging in the moving fluid. In this case, some of them, possibly arranged along a line, can be coupled to a light source to illuminate the fluid. The probe can then be used to measure turbidity, spectral measurements and imaging of the medium, for example by coupling it to two or more sources of illumination. These optical fibers with one end coupled with the third optical coupling means may be grouped in the form of a sheet to maximize the number of measuring points. In another aspect, there is provided an optical measuring system comprising a probe according to the invention, and optical illumination and / or detection means external to the probe and connected to the optical fibers of said probe. The optical measurement system according to the invention may furthermore comprise optical switching means capable of connecting optical illumination means and / or optical detection means to different optical fibers. According to embodiments, the optical measuring system according to the invention may furthermore comprise at least one light source connected to a first central optical fiber, and detection means of one of the following types: spectrometer, spectrometer Raman, hyperspectral camera (for example of the "push broom" or filter type) connected to at least one of the following fibers: second central optical fiber, optical fiber (s) side (s), fiber (s) optical (s) coupled (s) with the third optical coupling means 10. According to embodiments, the optical measurement system according to the invention may furthermore comprise a light source connected to at least one optical fiber having an end coupled with the third optical coupling means, and a detector of one of the following types: matrix detector, line detector, multichannel spectrometer connected to a plurality of optical fibers having an end coupled with said third optical coupling means. Thus, the present invention provides a probe for measuring in a small space a fluid sample from different angles with the possibility of implementing different optical techniques: UV spectroscopy, visible, near infrared, Raman or fluorescence, imaging. This probe makes it possible: - a greater robustness of measurement. For example, the measurements may be made optionally by at least three channels (in transmission, at 90 degrees and / or in backscatter). Some of these channels (at 90 degrees and backscattering in particular) are less sensitive to parasitic primary radiation, in particular for fluorescence measurements or in Raman spectroscopy; 30 - great flexibility. If the turbidity of the sample is low, the measurement in transmission gives the most information. If its turbidity is high, it is the 90-degree or backscatter measurements that give the most information. The detectors can be connected to one of these channels; -12- - an opportunity to characterize the physics and chemistry of the sample. Measurement methods (Raman, fluorescence and spectroscopy) can be combined and implemented simultaneously or sequentially using multiple optical fibers.

The probe is particularly suitable for measurement in reactors containing liquid or pipes. The shape of the probe also allows a better control of the flow in front of the measuring points, and a limitation of the fouling. It thus makes it possible to make decantation and / or demixing measures under good conditions.

DESCRIPTION OF THE FIGURES AND EMBODIMENTS Other advantages and particularities of the invention will appear on reading the detailed description of implementations and non-limiting embodiments, and the following appended drawings: FIG. 1 illustrates an overview of the probe according to the invention; 2 (a) and FIG. 2 (b) illustrate perspective views of the end of the probe with the measuring cavity, respectively from the side and from the front, FIG. 3 illustrates a sectional view of the end of the probe with the measuring cavity and the optical fibers shown; FIG. 4 illustrates a front view of the measurement cavity with the optical fibers shown, according to a first embodiment; FIG. 5 illustrates a front view of the measurement cavity with the optical fibers shown, according to a second embodiment, - FIG. 6 illustrates a front view of the measuring cavity with the optical fibers shown, according to a third embodiment. FIG. 7 illustrates a block diagram of a system implementing a probe according to the invention. It should be noted that FIGS. 1 to Fig. 6 do not show separate embodiments but illustrate features that can be combined in different ways in particular embodiments of the invention. With reference to Figs. 1, Fig. 2 (a) and FIG. 2 (b), a probe 1 according to the invention comprises a body 2, which is terminated at one end by two branches 3, 4 between which is a measurement cavity 10. These two branches 3, 4 are called, for reasons for clarity of the statement -13- first branch 3 and second branch 4, it being understood that these denominations can in no way be limiting. The branches 3, 4 and the body 2 may be for example metal, glass, sapphire, or a polymeric material (plastic) ...

The body 2 is terminated at its other end by a connection interface 5 which makes it possible to fix the probe, and which comprises the connection means, in particular the optical means. The probe presented is designed in particular to be able to carry out measurements in a bioreactor, a fermentor or any other enclosure containing a fluid. The body 2 is of elongated shape to allow measurement taken away from the walls, and sufficiently thin to be easily inserted into the enclosure. As explained above, the branches 3, 4 have a shape adapted to optimize the flow of the fluid in the measuring cavity 10.

With reference to FIG. 3, the probe 1 comprises optical fibers 23 which make it possible to interface the measurement cavity 10 with illumination and measurement means external to the probe 1. These optical fibers 23 are terminated by connectors at the interface The optical fibers 23 may be broken down into first optical fibers 30, second optical fibers 40 and third optical fibers 50 according to their arrangement with respect to the measurement cavity 10. The optical fibers 23 are multimode optical fibers, which let the light pass over most of the UV spectrum, visible and near infrared. The probe 1 also comprises optical coupling means which make it possible to interface the optical fibers 23 with the measurement cavity 10. These optical coupling means comprise first and second optical coupling means which open into the measuring cavity 11. at the level of respectively the first branch 3 and the second branch 4. The first and second optical coupling means comprise reflectors 22 which make it possible to return the beams of the first optical fibers 30 and the second optical fibers 40 at right angles in the cavity 11, along an optical measuring axis 21 which connects the two branches 3, 4. The first and second optical coupling means also comprise transparent windows 11, made of sapphire or possibly quartz glass, which lets the optical beams pass while ensuring the watertightness. The thickness of these windows 11 also determines the measurement length which corresponds to the path length of the optical beams in the fluid along the measurement optical axis 21. This thickness can be adjusted for this purpose. The optical coupling means also comprise third optical coupling means which open into the measuring cavity 11 at the bottom of this cavity. They comprise a window 12 of sapphire glass or possibly quartz which pass through the optical beams of the third fibers 50 while sealing. The optical axes of beams originating from (or picked up by) these third optical fibers 50 are perpendicular or close to the direction perpendicular to the optical measurement axis 21. The probe 1 further comprises a holding element integral with the body 2, which makes it possible to maintain the end of the various optical fibers 23 at the desired position, relative to the optical coupling means. The number of optical fibers 23 shown in the figures is in no way limiting and should only be considered as an example. We will describe configuration examples based on the nonlimiting assumption where one of the first optical fibers 30 is used as the central optical illumination fiber 31 (i.e., it is connected to a source from light). The first optical fibers 30 comprise at least this central optical illumination fiber 31. The first optical fibers 30 may also comprise at least one lateral optical fiber 32 placed near the central optical fiber 31, for collecting the backscattering light. It should be noted that depending on the measurement configurations, the central optical fiber 31 may also be used to collect backscattered light. The first optical fibers 30 may also comprise a plurality of lateral optical fibers 32 placed at equal distance, two-two, from the central optical fiber 31. This configuration makes it possible to make backscatter homogeneity measurements, by comparing the signals received by Lateral optical fibers 32 located equidistantly on either side of the central optical fiber 31. In fact, the variations between the signals issuing from these fibers 32 can essentially be attributed to local inhomogeneities ( presence of particles, ...) of the fluid in the measurement zone. Alternatively, this configuration can make it possible to improve the backscattering detection with respect to the inhomogeneities of the fluid, on average the signals coming from the lateral optical fibers 32 located equidistantly on either side of the central optical fiber 31. The second fibers optics 40 comprise at least one central optical fiber 41 for collecting the light in transmission.

They may also include one or more lateral optical fiber (s) 42 placed near the central optical fiber 41, to make diffusion measurements, or diffusion profiles, at small angles. Indeed, the measurement angle (with respect to the illumination axis that corresponds to the optical axis 21) of a lateral optical fiber 42 depends on the distance between the central optical fiber 41 and this lateral optical fiber 42 This configuration makes it possible to measure transmission homogeneity, by comparing the signals received by lateral optical fibers 42 located at equal distances on either side of the central optical fiber 41. Indeed, the variations between the signals from these fibers 42 may be mainly attributed to local inhomogeneities (presence of particles, ...) of the fluid in the measurement zone. Alternatively, this configuration can make it possible to improve the detection in transmission or at small angles with respect to the inhomogeneities of the fluid, on average the signals coming from the lateral optical fibers 42 located equidistantly on either side of the central optical fiber 41 The third optical fibers 50 comprise at least one optical fiber 51 for collecting light perpendicular to the optical measurement axis 21. They may further comprise a plurality of optical fibers 52 distributed along a line parallel to the axis This configuration can in particular be used to make measurements of wide-angle scattering profiles, insofar as each of these optical fibers 50 collects light from a diffusion center in the fluid at a different angle ( with respect to the illumination axis corresponding to the optics 21). The third optical fibers 50 can also be used to image the fluid that flows in the measurement cavity. They can be implemented in the form of a sheet, which makes it possible to obtain a large number of measurement points. Each fiber 50 constitutes a pixel, and an image of the particles of the fluid can be formed, for example with a linear detector, by using the scrolling fluid (which scroll is guided by the shape of the first and second branches 3, 4) for create the second dimension of the image. Of course, this mode of imaging can be implemented on the same probe and with the same fibers 50 as those used to make diffusion measurements or diffusion profile. By way of non-limiting example, in the embodiment shown, the body of the probe has a diameter of 25 mm and a length of 100 mm; The measuring cavity 10 has a useful length of 4 mm; the probe is adapted to perform measurements in fluids with a turbidity up to 12 000 NTU; the optical fibers comprise 9 silica optical fibers with a low OH ion content, a bandwidth of 350-2500 nm and a diameter of 220 μm, and 6 fibers with a diameter of 300 μm for detection, and 7 optical fibers for illumination. These optical fibers 23 are terminated by SMA type connectors at the connection interface 5. According to alternative embodiments, the body 2 of the probe may comprise two separable parts: according to an example presented in FIG. Fig. 1, the branches 3, 4 and the measuring cavity 10 may be on a removable element 6 screwed or fixed by any other means on a rear portion 7 of the body 2. In this case, the removable element 6 may include the optical means coupling, while the rear portion 7 of the body 2 may include the optical fibers 23, the ends 30 are held integral with the body 2 by a holding member. It is thus possible to change the measuring cavity 10, for example for maintenance reasons or to use different measurement cavities with different configurations or lengths of travel in the fluid; according to another example presented in FIG. 6, the body 2 may comprise an outer portion 71 which comprises the measuring cavity 10 and the coupling optical means. This outer portion 71 is designed such that it can be fixed on an enclosure for example. The body 2 then also includes an inner portion 70 which comprises the optical fibers 23. This inner portion 70 can be inserted into the outer portion 71 as in a sleeve and removed without risk of leakage or contamination of the enclosure. It is thus possible to replace the optical fibers 23, for example to use different fiber configurations 23 or to perform different types of measurement at different wavelengths without disassembling the probe.

Of course, the two possibilities can be combined, to produce a probe whose body 2 comprises an outer portion 71 with an end 6 (including the measuring cavity and the optical coupling means) removable, and an inner sleeve 70 removable with the optical fiber.

According to variant embodiments, the optical coupling means may comprise lenses or microlenses 24 which make it possible to optimize the coupling with the optical fibers 23. They may also comprise filters, for example of the pass-band or cut-off type. band ("notch") for application in Raman spectroscopy or fluorescence). According to alternative embodiments, the probe 1 may comprise a reference path for allowing a measurement of the intensity of the illumination outside the measuring cavity 10. In this case, the probe may comprise a coupler inserted on a optical fiber 23 provided for illumination, such as the first central optical fiber 31. This coupler takes a fraction of the light it returns by means of an optical fiber to the instrumentation coupled to the probe 1. Thus, the measurement is made closer to the measuring cavity 10 and takes into account losses in the probe, for example at the optical connectors.

According to alternative embodiments, with reference to FIG. 5, the third optical fibers 50 may further comprise a second line or a second layer of optical fibers 53 substantially parallel to the optical measurement axis 21. For imaging applications, a first fiber line 52 may be used to the measure, and the second line can be used for illumination. The third optical coupling means may further comprise a cylindrical lens 60 for improving imaging performance, in configurations with a single line of optical fibers 52 or with two lines of optical fibers 52, 53.

According to alternative embodiments, with reference to FIG. 6, the windows 11 may be of variable thickness depending on the position along a diameter or transverse dimension. They can be placed in the first and second branches 3, 4 so that their faces in contact with the fluid are not parallel. This configuration of the probe 1 makes it possible to carry out transmission measurements, possibly simultaneously, with different measurement lengths in the fluid depending on the optical fibers used. This can, for example, make it possible to use the probe over a larger range of turbidity values, or to make transmission measurements for different thicknesses of fluid.

In this embodiment, it is possible to implement, for example, the following measurement configurations: - illumination by a first central optical fiber 31, and transmission measurements at the same small angles by two second lateral optical fibers 42, with each once a path 62 in the fluid corresponding to a different measuring length; - illumination by two first lateral optical fibers 32, and transmission measurements respectively by the two second lateral optical fibers 42 facing the first lateral optical fiber 32 of illumination, with each time a path 61 in the fluid corresponding to a length measuring 20 different. Of course, the probe 1 in the embodiment of FIG. 6 may comprise third optical fibers 50 and third optical coupling means according to the embodiments shown in FIGS. 4 and FIG. According to alternative embodiments, a probe 1 may comprise first and second coupling means with at least two windows 11, arranged side by side on the first and second branches 4, 5, and arranged in such a way that to form: - a first set of windows 11 with their parallel interfaces with the fluid, as illustrated in FIG. 4, and a second set of windows 11 with their non-parallel fluid interfaces, as shown in FIG. 5. The two side-by-side windows can also be made in the same transparent element 11.

According to variant embodiments, the windows 11, 12 of the coupling means can be made in the form of a single window, for example a semicircular window. According to embodiments, the body 2, the distal portion 6 of the body 2 with the branches 3, 4 and the measurement cavity 10, or the branches 3, 4 can be made of a transparent material, such as quartz or glass. sapphire crystal. The windows 11 can then be part of this transparent element body 2. In this case, the optical coupling means are at least partially included in the body 2 and / or the first and second branches 4, 5.

According to alternative embodiments, the probe 1 may comprise optical fibers 23 of different diameters according to their positions, for example to optimize the signal-to-noise ratio of the assembly. Measuring Systems Referring to FIG. 7, we will now describe modes of implementation of the probe 1 and measurement systems implementing this probe 1. In general, a measurement system which implements the probe 1 further comprises one or more sources 71, and detection means 74. Optionally, it may comprise optical switching means 72, manual or computer-controlled, which make it possible to connect different illumination sources 71, and / or different means of illumination. detection 74, with different optical fibers 23.

For a large number of applications, the probe 1 is configured so as to provide an illumination point by the first central optical fiber 31 and at least three measurement points: in backscatter (at 180 degrees), by a first central optical fiber 31 and / or at least one first lateral optical fiber 32. If the first central optical fiber 31 is used in backscattering, the system further comprises a coupler or circulator for separating the illumination and the backscatter signal; - at 90 degrees, by at least a third fiber 51, - in transmission (at zero degrees), by the second central optical fiber 41. Of course, measurements of homogeneity and / or diffusion at small angles can also be implemented as described above. For applications in UV, visible or near infrared spectroscopy, the illumination source 73 coupled to the central optical fiber 31 may be, for example, a halogen lamp, a tunable monochromatic light, or a white laser (white light supercontinum). For this type of measurement, the detection means 74 comprise a spectrophotometer. This spectrometer may comprise a single measurement channel, and be coupled sequentially by optical switches 72 to the optical fibers 23 which collect the signals. A multichannel spectrophotometer or a hyperspectral camera can also be used to process at least a portion of the measurements simultaneously. If the fluid has a turbidity of the order of 0 NTU (no turbidity), the transmission measurement makes it possible to obtain the spectrum of this fluid.

If the fluid becomes turbid, the three positions provide useful information. The transmission measurement provides spectral information more correlated to the liquid chemistry while the 90-degree and backscatter measurements provide information on the elements in suspension in the liquid (solid particles, cells, oil drops, etc.). ). Turbidity, mean particle size and / or density can also be obtained in this way with a spectrophotometer 73. Finally, diffusion theory (single or multiple) can be used depending on the level of diffusion: technique of the two integrating spheres, Kubelka Munk equations, Fraunhofer diffraction, Mie theory.

The same configuration types of probe 1 can be used for fluorescence measurements. The excitation being done by the first central optical fiber 31, the measurements give access respectively to the frontal fluorescence of the sample (fiber 32), the fluorescence to 900 (fiber 51), and the fluorescence in transmission (optical fiber 41). . It should be noted that the measurement at 900 (fiber 51) makes it possible to avoid the effect of the excitation radiation on the measurement. In addition, the possibility of performing frontal fluorescence measurements in transmission or at 900 makes it possible to optimize the sensitivity to particles or to the liquid in suspension. The same configuration types of probe 1 can be used to do Raman / Cars spectroscopy. The laser excitation being done by the first central optical fiber 31, the measurements give access respectively to the backscattering Raman spectrum (fiber 32), the Raman spectrum at 90 ° (fiber 51), and the Raman spectrum in transmission (optical fiber 41). ). It should be noted that the measurement at 900 (fiber 51) makes it possible to avoid the effect of the excitation radiation on the measurement. In addition, the measurement of Raman spectrum at different angles may allow a better separation of the Raman effect with respect to the fluorescence effect. As explained above, the probe 1 may also comprise about ten measurement points (typically between 10 and 20 or even 30) distributed between the first, the second and the third optical fibers 30, 40, 50. This type of configuration allows to obtain measurements at a multitude of different angles. The most efficient way of carrying out the measurement is then to make a simultaneous acquisition of the signals by connecting, for example, the measurement fibers 30, 40, 50 to a parallel spectrometer 74. Such a spectrometer may for example comprise a matrix detector whose columns correspond to the different measurement channels or optical fibers 23, and on which the corresponding spectra are recorded along the lines. As previously, the illumination can be of different types depending on whether one wishes to make UV, visible, near-infrared, fluorescence or Raman spectroscopy. Probe configurations with a plurality of measurement points allow for better evaluation of the effect of scattering. Indeed, the diffusion profile can be measured much more accurately at different angles. It may even be possible to carry out granulometric measurements in situ. They also give the possibility of making measurements of homogeneity of the liquid, to see if a mixture of solutions is homogeneous for example. For that, it suffices to compare the spectra of the measurements made at the same angles. For example, a measure of homogeneity can be obtained by comparing the measurements of the first or second secondary optical fibers 32, 42 located on one side of the central fiber 31 or 41 with those of the first or second secondary optical fibers. 32, 42 located on the other side. The detection of inhomogeneity can be done by comparing the spectra between them by division or by principal component analysis (detection of inhomogeneities by detection of outliers, or "outliers" in English). It should be noted that the homogeneity can also be obtained by illuminating the fluid with a third fiber 50 and comparing the signals obtained by the first 10 and the second optical fibers 30, 40; As explained above, the probe 1 can also be used to perform online imaging. Indeed, if the number of third optical fibers 50 is sufficiently large (for example of the order of 15 to 20) and the acquisition speed is fast enough, the system can produce an image by combining the simultaneous measurements. The illumination may be derived from a first central fiber 31, some of the third fibers 51, 52, or a second line of third lighting fibers 53. The illumination may also be at a wavelength of excitation to perform fluorescence imaging.

A linear detector 74 may in particular be used. The shape of the probe facilitates a laminar flow, the passage of the liquid will allow a uniform scan pledge of a good quality image. A parallel spectrometer 74 may also be used to produce hyperspectral images, or a plurality of images at different wavelengths. The measurement possibilities make it possible to implement different types of processing depending on the information sought. In the case of multipoint measurements at different angles, the signal can be processed in particular: - to obtain turbidity measurements, by making ratios between the 90 degree and transmission measurements, or between 90 degree and 100 degree measurements; other angles; or by applying the theory of laser particle size, by analyzing the shape of the diffraction pattern from measurements at small angles and large angles. Another method based on the statistical processing of the data can also be implemented in order to separate the components of the measurement signals representative of the physical characteristics of particles suspended in the fluid, chemical measurements. This method is described in the 3.-M document. Roger, F. Chauchard, V. Bellon-Maurel, "EPO-PLS external parameter orthogonalization of PLS application to temperature independent content of sugar content of intact fruits", Chemometrics and Intelligent Laboratory Systems 66 (2003) 191-204. Indeed, the 900 and backscatter signal is highly correlated to the particle signal, but it also contains the chemical information of the fluid. In order to suppress this parasitic information, the following approach is implemented: In a first step, a principal component analysis is calculated on the transmission spectra. These spectra contain in majority the information of the liquid. The main components are then used to define a projection operator. The spectra obtained in backscattering and at 90 degrees are then processed in the following way: The part containing the chemical information of the fluid is calculated by multiplying the spectrum by the projection operator; - The particle information part is calculated by subtracting the raw spectrum by the spectrum multiplied by the projection operator. Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

Claims (17)

REVENDICATIONS1. An optical measuring probe device (1) for performing spectrometric and / or photometric measurements in a fluid, comprising a body (2) adapted to be immersed in said fluid, characterized in that it further comprises: - at least one first and second legs (4, 5) extending at the end of said body (2) in its extension and delimiting a measuring cavity (10), - a plurality of optical fibers (23) inserted into said body ( 2) and capable of being connected to optical illumination means (73) and / or detection means (74), optical coupling means (11, 12, 22, 60) capable of transmitting light between at least a portion of said optical fibers (23) and the measurement cavity (10), comprising (i) first optical coupling means (11, 22) opening into the measurement cavity (10) at the first branch (3). ), (ii) second optical coupling means (11, 22) opening into the measurement cavity (10) at the water of the second branch 20 (4), and (iii) third optical coupling means (12, 60) opening into the measuring cavity (10) at the bottom of said cavity. 2. The probe of claim 1 which further comprises fin-shaped legs (3, 4) for controlling a flow of liquid flowing in the measuring cavity (10) so as to render it substantially laminar and compress it to reduce the parasitic effect of gas bubbles. 3. The probe of one of claims 1 or 2, wherein the body (2) has a diameter less than 26 mm. 30 4. The probe of one of the preceding claims, wherein the measuring length (20) in the measuring cavity (10) is suitable for carrying out measurements in media with turbidity greater than 1000 NTU. 35-25- The probe of one of the preceding claims, wherein the measuring length (20) in the measurement cavity (10) is variable along the first and second branches (4, 5). The probe of one of the preceding claims, wherein the first and / or second optical coupling means include a right angle reflector (22) and a window (11) of at least partially transparent material. 7. The probe according to one of the preceding claims, in which the body (5) comprises separable parts of which: a first part (7, 70) including the optical fibers (23), and a second part (6, 71) comprising the first and second legs (4, 5) and the measurement cavity (10), and including the optical coupling means (11, 12, 22, 60). The probe of one of the preceding claims, which further comprises a first central optical fiber (31) having an end coupled with the first optical coupling means (22, 11), and a second central optical fiber (41). ) having an end coupled with the second optical coupling means (22, 11), which first and second central optical fibers (31, 41) defining an optical measurement axis (21) in the cavity (10). 25 The probe of claim 8, which further comprises: - at least one lateral optical fiber (32) having an end coupled with the first optical coupling means (22, 11) and placed near the end of the first central optical fiber (31), and / or - at least one lateral optical fiber (42) having one end coupled with the second optical coupling means (22, 11) and placed near the end of the second fiber central optic (41). The probe of one of claims 8 or 9, which further comprises: at least two lateral optical fibers (32) having an end coupled with the first optical coupling means (22, 11), which ends are placed substantially equidistant from the end of the first central optical fiber (31), and / or - at least two lateral optical fibers (42) having an end coupled with the first optical coupling means ( 22, 11), which ends are placed substantially equidistant from the end of the second central optical fiber (41). The probe of one of the preceding claims, which further comprises a plurality of optical fibers (50) having an end coupled with the third optical coupling means (12, 60), which ends are disposed in at least one line extending between the first and second branches (3, 4). The probe of claim 11, which comprises a plurality of optical fibers (50) having an end coupled with the third optical coupling means (12, 60), which ends are disposed along two lines extending between the first and second the second branches (3, 4). 13. The probe of one of claims 11 or 12, wherein the third optical coupling means further comprise at least one cylindrical lens (60). 14. Optical measurement system comprising a probe (1) according to one of the preceding claims, and optical illumination means (73) and / or detection (74) external to the probe and connected to the optical fibers (23). of said probe. The optical measuring system according to claim 14, which further comprises optical switching means (72) capable of connecting optical illumination means (73) and / or optical detection means (74) to different fibers. optical (23) .- 27- The optical measuring system of one of claims 14 or 15, which further comprises at least one light source (73) connected to a first central optical fiber (31), and detection means (74) of one of the following types: spectrometer, Raman spectrometer, hyperspectral camera, connected to at least one of the following fibers: second central optical fiber (41), optical fiber (s) side (s) (32, 42 ), optical fiber (s) (50) coupled with the third optical coupling means (12, 60). The optical measuring system of one of claims 14 or 15, which further comprises a light source (73) connected to at least one optical fiber (50) having an end coupled with the third optical coupling means ( 12, 60), and a detector (74) of one of the following types: matrix detector, line detector, multichannel spectrometer, connected to a plurality of optical fibers (50) having an end coupled with said third optical coupling means ( 12, 60).