X-ray fluorescence analysis method and apparatus
A portable X-ray fluorescence device combines confocal and two-dimensional spectrometry for in situ, non-invasive, three-dimensional analysis of objects, addressing the challenge of depth localization in paintings and reducing radiation exposure.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- PARIS SCI & LETTRES
- Filing Date
- 2024-11-26
- Publication Date
- 2026-05-29
AI Technical Summary
Existing non-destructive X-ray fluorescence techniques struggle with accurately locating chemical elements in depth within objects, particularly paintings, often requiring destructive sampling and prolonged analysis times due to separate lateral and depth measurements, which can lose positional accuracy and expose objects to excessive radiation.
A portable X-ray fluorescence analysis device performs combined laterally and depth-resolved analyses using confocal X-ray fluorescence spectrometry and two-dimensional fluorescence spectrometry, allowing in situ analysis without moving the object, preserving positional accuracy and minimizing radiation exposure.
Enables detailed, non-invasive, and time-efficient chemical composition analysis of objects, particularly paintings, by creating three-dimensional elemental maps with high spatial resolution, preserving positional accuracy and reducing radiation exposure.
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Abstract
Description
Title of the invention: Method and device for X-ray fluorescence analysis. Technical field
[0001] The present invention relates to a method for analyzing an object to be analyzed by X-ray fluorescence. The invention also relates to an X-ray fluorescence analysis device used in such a method.
[0002] The field of the invention is, without limitation, that of the analysis of heritage objects and in particular painted works. State of the art
[0003] Non-destructive microanalysis of ancient cultural heritage objects is essential for identifying the nature of the materials composing them, studying their provenance, manufacturing techniques or investigating alteration phenomena in museums and heritage sites.
[0004] Non-destructive X-ray-based analysis and imaging techniques exist. X-ray fluorescence spectrometry analyses are highly sensitive and can detect chemical elements in very low concentrations. These analyses are generally performed using two-dimensional scanning, allowing for laterally resolved imaging.
[0005] However, it is often difficult to know, for example, in which paint layer the detected chemical element is located. It is important to be able to locate the chemical elements in depth and to specify their correlations in order to interpret chemical maps, as well as to identify the artistic technique, retouching, overpainting, or other factors.
[0006] For this purpose, it is often necessary to take micro-samples to locate the paint layers. In general, sampling is prohibited or very restricted on museum paintings.
[0007] Information on the stratigraphy of the pictorial layers can also be obtained in a non-invasive manner from independent measurements by confocal X-ray micro-fluorescence, for which a micro-volume of measurement is moved into the layers of interest.
[0008] However, these systems are generally stationary systems. The objects to be analyzed, and in particular paintings of art, must therefore be moved and transported to laboratories or near facilities such as synchrotrons.
[0009] Also, by performing lateral and depth analyses separately, the exact positions of the analyses may be lost, and the superimposition of the results of Measurement is not always possible due to the heterogeneity of the objects studied. Furthermore, the objects are exposed to ionizing radiation repeatedly, and the analysis time is consequently prolonged. Description of the invention
[0010] One object of the present invention is to overcome at least one of these drawbacks.
[0011] An object of the invention is to provide a method and an analytical device for carrying out laterally and depth-resolved X-ray fluorescence spectrometry analyses in a correlated or combined manner.
[0012] Another object of the present invention is to provide a method and an analytical device for performing laterally and deep-resolved X-ray fluorescence spectrometry analyses in a non-invasive manner.
[0013] It is a further object of the present invention to provide a method and an analytical device for carrying out laterally and depth-resolved X-ray fluorescence spectrometry analyses in situ, without moving or manipulating the object to be analyzed.
[0014] At least one of these goals is achieved with a fluorescence analysis method X-ray of an object to be analyzed, implemented in situ using a portable X-ray fluorescence analysis device, the process comprising the following steps: - focusing of an X-ray beam, called a measurement beam, by focusing means onto or into the object to be analyzed, the X-rays being adapted to excite X-ray emission from the object to be analyzed, - Two-dimensional scanning of the measurement beam on the object to be analyzed at a plurality of measurement points on the object to be analyzed, - two-dimensional detection, by means of two-dimensional X-ray fluorescence spectrometry, of the X-rays emitted by the object along a first detection axis, called the two-dimensional detection axis, at the plurality of measurement points, - identification of at least one measurement point of interest among the plurality of measurement points, and - Confocal detection, by means of confocal X-ray fluorescence spectrometry, of X-rays emitted by the object at at least one measurement point of interest within a measurement volume and along a second detection axis, called the confocal detection axis, the focusing means being configured to generate the measurement volume,
[0015] the measurement volume being offset outwards relative to a periphery of the device, and the device being adapted to be transported.
[0016] The method according to the invention makes it possible to analyze an object using X-ray fluorescence and combining elemental imaging and depth analysis. The object may be a painting, for example, a historical painting in a museum or in a cave, particularly a prehistoric one, or another work of art. The method according to the invention notably allows for good resolution for analyzing the paint layers in depth, and this at one or more areas of interest determined beforehand by means of the two-dimensional detection step.
[0017] The method combines confocal X-ray fluorescence spectrometry and two-dimensional fluorescence spectrometry, these techniques being implemented separately in the prior art. By performing them jointly, using a portable X-ray fluorescence analysis device, the position of the depth analyses relative to the two-dimensional analysis is preserved, even for highly heterogeneous objects.
[0018] The measurements or analyses are carried out in situ using a portable analysis device, not requiring the object, such as a painted work, to be moved to a laboratory or other facility, which could damage it.
[0019] The method according to the invention thus allows for a complete analysis of an object by X-ray fluorescence. In particular, the measurements make it possible to determine, qualitatively and semi-quantitatively, the chemical composition layer by layer of painted works. For these works, a better understanding of complex stratigraphies can be obtained by combining the two measurement techniques.
[0020] It should be noted that the term "measurement point" indicates a location or place where the measurement is carried out, the measurement point being able to have a more or less extensive dimension depending on the degree of focus of the measurement beam.
[0021] According to one embodiment, the two-dimensional detection step is carried out for a set of measurement points covering substantially the entire surface of the object to be analyzed, the method further comprising a step of establishing a two-dimensional map from detected signals.
[0022] This could be, for example, a chemical mapping of a painted work or any other structure exhibiting a dispersion of chemical elements.
[0023] According to one embodiment, the method according to the invention may further comprise the following steps, for each measurement point of interest: - displacement of the confocal measurement volume in the direction of the depth of the object to be analyzed, and - Reiteration of the confocal detection step at several depths of the object to be analyzed.
[0024] For a plurality of measurement points of interest, the measurement beam is thus scanned three-dimensionally on and in the object to be analyzed.
[0025] Advantageously, the steps of moving the confocal measurement volume and of repeating the confocal detection step can be carried out for a plurality of juxtaposed measurement points of interest.
[0026] Confocal measurements at different depths and for juxtaposed measurement points of interest, i.e., close together, allow the establishment of a three-dimensional map from detected signals, at least on a small surface.
[0027] This could be, for example, a 3D chemical map of a painted work or any other structure exhibiting a dispersion of chemical elements.
[0028] According to another aspect of the same invention, a device for analyzing an object to be analyzed by X-ray fluorescence is proposed, the device comprising: - X-ray generation means configured to produce an X-ray beam, called a measurement beam, the X-rays being adapted to excite X-ray emission from the object to be analyzed, - Focusing means configured to focus the X-ray beam onto or into the object to be analyzed and to generate a confocal measurement volume, - Two-dimensional X-ray fluorescence spectrometry means, comprising a first X-ray detector, called a two-dimensional detector, configured to detect the X-rays emitted by the object along a first detection axis, called a two-dimensional detection axis, at a plurality of measurement points, - means for confocal X-ray fluorescence spectrometry, comprising a second X-ray detector, called a confocal detector, the confocal detector being configured to detect X-rays emitted by the object in the confocal measurement volume and along a second detection axis, called a confocal detection axis,
[0029] the measurement volume being offset outwards relative to a periphery of the device, and the device being adapted for transport.
[0030] The device according to the present invention combines confocal X-ray fluorescence spectrometry and two-dimensional X-ray fluorescence spectrometry. It enables three-dimensional elemental analysis and imaging of objects, particularly heritage objects and, more specifically, painted works. The device according to the invention allows these measurement techniques to be performed successively, in order to achieve a more complete and detailed selection of the area studied. The device also saves time and minimizes the exposure of the works to radiation during the analyses.
[0031] Advantageously, the X-ray generation means, the X-ray detectors and the focusing means are arranged together to form a portable measuring head.
[0032] Thanks to the fact that the measurement volume is offset outwards relative to a periphery of the device, the device can be brought closer to the object to be analyzed without risk of damaging it.
[0033] Preferably, the means for generating X-rays may include an X-ray tube.
[0034] X-ray tubes have the advantage of a wide energy range and stable performance over long measurement periods, while also allowing for intensity control. They are easy to use and versatile.
[0035] According to one embodiment, the device according to the invention may further include means for moving the confocal measurement volume in the direction of the depth of the object to be analyzed.
[0036] Means of displacement along the depth direction can also be implemented to correct the position of the measuring head during two-dimensional measurements or scans, when it gets too close to or too far from the surface of the object during the analysis.
[0037] According to some embodiments, the X-ray detectors may each comprise one of the following: • a proportional gas meter, • a scintillation detector, • a solid-state detector.
[0038] Preferably, the confocal detector and the two-dimensional detector are of the same type.
[0039] In this case, the detectors can easily be interchanged. Detector control and signal processing are also simplified. Furthermore, one detector can be used to replace the other in case of failure.
[0040] Even more preferably, the confocal detector and the two-dimensional detector are both silicon drift detectors (SDD).
[0041] According to embodiments, the measurement beam can be incident on the surface of the object at an angle between 30° and 150°.
[0042] Preferably, the measuring beam is incident on the surface of the object at an angle of 45° or 90°.
[0043] The confocal detection axis can be oriented with respect to the surface of the object at an angle between 30° and 150°.
[0044] The angle between the measurement beam and the confocal detection axis can be between 30° and 90°.
[0045] The two-dimensional detection axis can be oriented with respect to the surface of the object at an angle between 1° and 179°.
[0046] According to embodiments, the energy of the X-ray beam incident on the object to be analyzed, i.e., the measurement beam, is between 1 and 40 keV, and preferably between 1 and 20 keV.
[0047] The analytical method and apparatus according to the invention are particularly well-suited for use in heritage science. They can also be applied in other fields outside of cultural heritage, such as the study of materials of pharmaceutical interest, in the recycling industry (e.g., rare or precious metals), the automotive industry, and the semiconductor industry. Through the combination of confocal X-ray fluorescence spectrometry and two-dimensional X-ray fluorescence spectrometry, the chemical distribution of the various constituents in different materials or structures can be characterized completely and entirely non-invasively. Description of the figures and methods of implementation
[0048] Other advantages and features will become apparent upon examination of the detailed description of non-limiting examples and the accompanying drawings, in which: - [Fig.1] [Fig.1] schematically represents a measuring head of an X-ray fluorescence analysis device according to an embodiment of the invention; - [Fig.2] [Fig.2] shows an example of a measurement beam arrangement and a detection axis implemented in a device and an analysis method according to the present invention.
[0049] It is understood that the embodiments described below are in no way exhaustive. In particular, all the variants and embodiments described may be combined with each other provided there are no technical obstacles to such combination.
[0050] In the figures, elements common to several figures may retain the same reference.
[0051] Figure 1 shows an example of an embodiment of a measuring head of a device for the X-ray fluorescence analysis of an object. The device can be implemented in an X-ray fluorescence analysis process.
[0052] The measuring head of the analysis device 1, shown in [Fig.1], includes an X-ray tube 2 and a first and second X-ray detector 3, 4.
[0053] The X-ray tube 2 is configured to deliver an X-ray beam. The X-ray beam, called the measurement beam, is used to excite an X-ray emission in the object to be analyzed, by exciting the electrons inside a small sampling area in the object.
[0054] The two X-ray detectors 3, 4 are configured to detect X-rays emitted by the object.
[0055] The first detector 3, called a two-dimensional detector, is a detector used for detection in two-dimensional mode, that is to say, for detection along two axes in a plane perpendicular to the measurement beam.
[0056] The first detector 3 is oriented to detect the X-rays emitted by the object along a first detection axis, called the two-dimensional detection axis.
[0057] The second detector 4, called the confocal detector, is a detector used for confocal detection. The confocal detector 3 is configured to detect the X-rays emitted by the object to be analyzed in a measurement volume, as described below.
[0058] The second detector 4 is oriented to detect the X-rays emitted by the object along a second detection axis, called the confocal detection axis.
[0059] According to one embodiment, the two detectors 3, 4 are of the same type.
[0060] These are preferably silicon drift detectors (SDD).
[0061] The detectors can also be proportional gas meters, scintillation detectors or solid state detectors.
[0062] Proportional or gas proportional meters use a chamber filled with gas, typically high-purity argon, xenon, neon, and krypton, with a central anode wire surrounded by a cathode. Incoming X-rays ionize the gas molecules, resulting in the generation of electron-ion pairs, primarily through the photoelectric effect. The amplitude of the ionization signal is proportional to the energy of the incident X-rays.
[0063] Scintillation detectors exhibit a much higher detection efficiency for high-energy photons than proportional counters. They use a scintillating material that emits light when exposed to incident X-rays. Coupled to photomultiplier tubes, photodiodes, or charge-coupled devices (CCDs), the emitted light is detected, converting the optical signal into an electrical signal.
[0064] Solid-state detectors, more specifically semiconductor detectors, are the most widely used detectors in X-ray spectroscopy, particularly when energy resolution is paramount. They include, in addition to silicon drift detectors (SDDs), lithium-silicon (Si(Li)) drift detectors, high-purity germanium (HPGe) detectors, and silicon positive-intrinsic-negative (Si-PIN) detectors. They convert incident X-rays into electrical signals by generating electron-hole pairs in the detector's semiconductor material. The number of electron-hole pairs generated is proportional to the energy of the incident X-rays. Semiconductor detectors, particularly SDDs, have excellent energy resolution, fast response time and are compact in size.
[0065] The device 1 also includes focusing means for focusing the X-ray beam onto or into the object to be analyzed and for focusing the X-rays emitted by the object onto at least one of the detectors.
[0066] In the embodiment shown in [Fig. 1], the X-ray tube 2 and the confocal detector 4 are each equipped with a focusing polycapillary optic 5, 6. The polycapillary optic 5 of the X-ray tube 2 focuses the measurement beam onto or into the object to be analyzed. The polycapillary optic 6 of the confocal detector 4 focuses the X-rays emitted by the object into a measurement volume onto the sensitive surface of the detector.
[0067] The two poly-capillary optics 5, 6 therefore have a common action of creating the confocal measurement volume.
[0068] The incident X-ray beam penetrates, for example, a few tens to hundreds of micrometers into the object to be analyzed. The field of view of the emitted radiation seen by the confocal detector is then limited by its focusing optics.
[0069] Polycapillary optics use arrays of small hollow glass tubes (capillaries) that collect, guide, and focus X-rays through numerous total internal reflections. These capillaries are generally aligned parallel to each other, and the X-rays incident on the inlet surface undergo multiple internal reflections, emerging from the outlet surface in a collimated or focused beam.
[0070] Alternatively, the focusing means may also include one or more focusing lenses, slits or pinholes.
[0071] X-ray lenses may include collimators, Fresnel zonal plates or compound refractive lenses.
[0072] The measurement volume, or micro-volume, allows the analysis of the deep layers of a multilayered object by performing depth-resolved scans. As an example, the dimensions of the micro-volume can vary from 1 pm3 (for high-energy X-rays and with polycapillary optics) to 60 x 60 x 60 pm3 (for low-energy X-rays).
[0073] Fig. 2 schematically shows the orientation of the measurement beam and two detection axes relative to a plane of the object to be analyzed, according to one embodiment of the invention.
[0074] The measuring beam 10 is incident on the surface 11 of the object at an angle of 45°.
[0075] The measuring beam 10 can also be incident on the surface 11 of the object at another angle between 30° and 150°.
[0076] As shown in [Fig.2], a first detection axis 13, called the two-dimensional detection axis, is oriented with respect to the surface 11 of the object at an angle of 45°. A second detection axis 12, called the confocal detection axis, is oriented with respect to the surface 11 of the object at an angle of 45°.
[0077] In the example, the angle between the measuring beam 11 and the detection axis 12 is 90°.
[0078] According to embodiments, the confocal detection axis can be oriented with respect to the surface 11 of the object at an angle between 30° and 150°.
[0079] According to embodiments, the two-dimensional detection axis can be oriented with respect to the surface 11 of the object at an angle between 1° and 179°.
[0080] The angle between the measuring beam 10 and the confocal detection axis can be between 30° and 90°.
[0081] In the case of confocal detection, in order to minimize the measurement volume, a 90° geometry between the axis of the measurement beam and the confocal detection axis is sought, as illustrated in [Fig. 2]. Therefore, when the measurement beam is incident, for example, at 30°, 45°, or 60° to the surface of the object, the detection axis is oriented at 60°, 45°, or 30° accordingly. Most often, the 45° angle is chosen.
[0082] A non-perpendicular angle of incidence with respect to the surface of the object results in a slightly larger excitation area than for a perpendicular angle of incidence. However, the resulting measurement volume is smaller.
[0083] All the components described (detectors, X-ray tube, focusing optics) are mounted together to form a measuring head.
[0084] The components of the measuring head can, for example, be arranged in a housing or mounted on a support. The entire measuring head can be mounted on a stand, such as a tripod, to be positioned in front of an object to be analyzed.
[0085] To perform two-dimensional measurements on the surface of the object to be analyzed, the measurement beam must be moved over the object, along the two axes x, y in the plane of the object.
[0086] To make these measurements in 2D, the device, and in particular the measuring head, is moved in front of the object to be analyzed.
[0087] To perform three-dimensional measurements on the surface of the object to be analyzed and in its depth, not only must the measurement beam be moved over the object along the two axes x and y in the plane of the object, but the measurement volume must also be moved along the z-axis, which is substantially perpendicular to the surface of the object. The measurement volume can thus penetrate a few pm or hundreds of pm below the surface of the object.
[0088] To move the measurement volume along the z-axis, the measurement head is moved closer to or further from the object along the z-axis, substantially perpendicular to the surface of the object.
[0089] Typically, the energy of the X-ray beam incident on the object to be analyzed, i.e., the measurement beam, is between 1 and 40 keV. Preferably, the energy is between 1 and 20 keV.
[0090] The energy range of the device is notably limited by the nature and / or material of the focusing means used.
[0091] For example, due to factors such as internal reflections and the critical acceptance angle in capillaries, polycapillary optics filter out energies above a certain value. However, a polycapillary optic allows for the analysis of energies below this value and enables good distribution of the light intensity over the detector surface.
[0092] The device according to the invention also includes means for moving the confocal measurement volume in the direction of the depth of the object to be analyzed.
[0093] The means of movement may include, for example, a combination of translation platforms or plates allowing the measuring head to be moved along the three directions x, y, z of space.
[0094] These platforms are preferably equipped with linear motors. Linear motors provide smooth and very precise platform movements.
[0095] The translation platforms can also be equipped with piezoelectric actuators.
[0096] Advantageously, the device according to the invention is adapted for transport. In particular, the measuring head is portable. It can thus be positioned directly in front of the object to be analyzed, especially painted works that cannot be moved.
[0097] Also, in the device according to the invention, the confocal measurement volume is offset outwards relative to a periphery of the device. This means that the measurement volume can be brought as close as possible to the object to be analyzed, without any risk of other elements of the measurement head coming into contact with the surface of the object. Furthermore, it is possible to move the measurement volume within the depth of the object to be analyzed without damaging it, thus enabling non-invasive measurements.
[0098] The device according to the invention, for example as described with reference to Figures 1 and 2, can be implemented in an X-ray fluorescence analysis process of an object to be analyzed.
[0099] The analysis method according to the invention includes a step of focusing an X-ray beam, referred to as the measurement beam, onto or into the object to be analyzed. The X-rays may, for example, be from an X-ray tube and are adapted to excite X-ray emission by fluorescence from the object to be analyzed.
[0100] The measurement beam is scanned, in the plane of the object, over the object to be analyzed at a plurality of measurement points,
[0101] At each measurement point, a detection step is performed to detect an X-ray fluorescence signal using a first X-ray detector. A signal is detected at a plurality of measurement points. The signals are detected along a measurement axis referred to as two-dimensional detection.
[0102] This detection step is called two-dimensional detection.
[0103] According to one embodiment, the two-dimensional detection step can be carried out for a set of measurement points covering substantially the entire surface of the object to be analyzed.
[0104] Thus, an X-ray fluorescence spectrum is obtained for each measurement point on the object's surface. The relative intensity of the fluorescence peaks corresponding to chemical elements in the spectra varies according to their position on the surface. By plotting the surface area under the characteristic peaks of the elements as a function of their position on the object's surface, two-dimensional chemical profiles of the object are obtained. It is then possible to establish a two-dimensional elemental map from the signals detected at each measurement point.
[0105] The method according to the invention includes a step of identifying at least one measurement point of interest among the plurality of measurement points, based on the signals detected in the preceding step. By way of example, a measurement point of interest may be identified as a point where the X-ray fluorescence spectrum exhibits an X-ray fluorescence line corresponding to a chemical element characteristic of a pigment of interest, or a point exhibiting compositional differences compared to a neighboring point.
[0106] Once the measurement point(s) of interest have been identified, a confocal detection step is performed to detect an X-ray fluorescence signal at each of the measurement points of interest, using a second X-ray detector in confocal mode. Confocal detection is carried out within a measurement volume and along a confocal detection axis. As described previously, the measurement volume is created by the focusing means, and in particular by the focusing optics of the confocal detector and the X-ray tube.
[0107] According to one embodiment, the method according to the invention may further comprise, for at least one of the identified measurement points of interest, the displacement of the confocal measurement volume in the direction of the depth of the object to be analyzed, and the reiteration of the confocal detection step at multiple depths of the object to be analyzed.
[0108] By way of example, after selecting a location on the artwork to be analyzed during the two-dimensional detection step, a depth-resolved scan can be performed by moving the artwork away from the measuring head along the z-axis. The movement can be made in steps of 10 pm, for example. It is also possible to perform steps of 1 pm or 5 pm, for example. The resolution of the steps depends on the size of the focused measuring beam spot, and therefore on the focusing optics, as well as the stability of the device. Naturally, the smaller the measurement step, the longer the analysis time.
[0109] Thus, the measurement micro-volume scans the element distributions throughout the artwork. An X-ray fluorescence spectrum is obtained for each depth position. The relative intensity of the element fluorescence lines, or peaks, in the spectra varies with depth. By plotting the area of the characteristic peaks of the elements as a function of depth position, the depth scan profiles are obtained.
[0110] The spatial resolution obtained is on the order of a micrometer.
[0111] When the steps of shifting the confocal measurement volume and repeating the confocal detection step are performed for a plurality of juxtaposed or adjacent measurement points of interest, a three-dimensional map from the detected signals can be established. This map is created for a small area of the object to be analyzed, due to the large number of signals to be detected and processed.
[0112] Of course, the analysis device according to the invention can be implemented to perform only confocal measurements or only two-dimensional measurements. In particular, confocal measurements can be carried out without having previously performed two-dimensional measurements.
[0113] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.
Claims
Demands
1. A method for analyzing an object to be analyzed by X-ray fluorescence, implemented in situ using a portable X-ray fluorescence analysis device, the method comprising the following steps: - focusing an X-ray beam, referred to as the measurement beam (10), by focusing means (5, 6), onto or into the object to be analyzed, the X-rays being adapted to excite X-ray emission by the object to be analyzed, - two-dimensional scanning of the measurement beam (10) over the object to be analyzed at a plurality of measurement points on the object to be analyzed, - two-dimensional detection, by means (3) of two-dimensional X-ray fluorescence spectrometry, of the X-rays emitted by the object along a first detection axis (13), referred to as the two-dimensional detection axis, at the plurality of measurement points, - identification of at least one measurement point of interest among the plurality of measurement points, and - confocal detection,by means (4) of confocal X-ray fluorescence spectrometry, X-rays emitted by the object at at least one measurement point of interest in a measurement volume and along a second detection axis (12), called the confocal detection axis, the focusing means (5, 6) being configured to generate the measurement volume, the measurement volume being offset outwards from a periphery of the device, and the device being adapted for transport.
2. A method according to claim 1, characterized in that the two-dimensional detection step is carried out for a set of measurement points covering substantially the entire surface (11) of the object to be analyzed, the method further comprising a step of establishing a two-dimensional chemical map from detected signals.
3. Method according to claim 1 or 2, characterized in that it further comprises the following steps, for each measurement point of interest: - displacement of the confocal measurement volume in the direction of the depth of the object to be analyzed, and - repetition of the confocal detection step at several depths of the object to be analyzed.
4. A method according to the preceding claim, wherein the steps of shifting the confocal measurement volume and of repeating the confocal detection step are performed for a plurality of juxtaposed measurement points of interest.
5. X-ray fluorescence analysis device for an object to be analyzed, comprising: - means (2) for generating X-rays configured to produce an X-ray beam, referred to as the measurement beam (10), the X-rays being adapted to excite X-ray emission by the object to be analyzed, - focusing means (5, 6) configured to focus the X-ray beam onto or into the object to be analyzed and to generate a confocal measurement volume, - means for two-dimensional X-ray fluorescence spectrometry, comprising a first X-ray detector (3), referred to as the two-dimensional detector, configured to detect the X-rays emitted by the object along a first detection axis (13), referred to as the two-dimensional detection axis, at a plurality of measurement points, - means for confocal X-ray fluorescence spectrometry, comprising a second X-ray detector (4), referred to as the confocal detector,the confocal detector (4) being configured to detect the X-rays emitted by the object in a measurement volume and along a second detection axis (12), called the confocal detection axis, the measurement volume being offset outwards relative to a periphery of the device, and the device being adapted for transport.
6. Device according to the preceding claim, further comprising means for moving the confocal measurement volume in the direction of the depth of the object to be analyzed.
7. Device according to claim 5 or 6, characterized in that the X-ray detectors (3, 4) each comprise one of: • a gas proportional counter, • a scintillation detector, • a solid state detector.
8. Device according to any one of claims 5 to 7, characterized in that the X-ray detectors (3, 4) each comprise a silicon drift detector, SDD.
9. Device according to any one of claims 5 to 8, characterized in that the X-ray generation means comprise an X-ray tube (2).
10. Device according to any one of claims 5 to 9, characterized in that the measuring beam (10) is incident on the surface (11) of the object at an angle between 30° and 150°, preferably the measuring beam (10) being incident on the surface (11) of the object at an angle of 45° or 90°.
11. Device according to any one of claims 5 to 10, characterized in that the confocal detection axis (12) is oriented with respect to the surface (11) of the object at an angle between 30° and 150°.
12. Device according to any one of claims 5 to 11, characterized in that the angle between the measuring beam (10) and the confocal detection axis (12) is between 30° and 90°.
13. Device according to any one of claims 5 to 12, characterized in that the two-dimensional detection axis (13) is oriented with respect to the surface (11) of the object at an angle between 1° and 179°.
14. Device according to any one of claims 5 to 13, characterized in that the energy of the X-ray beam incident on the object to be analyzed is between 1 and 40 keV, preferably between 1 and 20 keV.