WO2015189283A1

WO2015189283A1 - Mobile spectroscopic analysis device, in particular for geological analyses

Info

Publication number: WO2015189283A1
Application number: PCT/EP2015/062961
Authority: WO
Inventors: Muriel SACCOCCIO; Hubert Diez; Gilles Dromart; Sylvestre MAURICE
Original assignee: Centre National D'etudes Spatiales; Tharsys Energy; Universite Paul Sabatier-Toulouse Iii; Centre National De La Recherche Scientifique
Priority date: 2014-06-10
Filing date: 2015-06-10
Publication date: 2015-12-17
Also published as: FR3022028B1; FR3022028A1

Abstract

A LIBS analysis device comprises a laser radiation source and a measuring head with optical illumination means suitable for directing at least two separate laser beams towards a target to be analysed, so as to form at least two analysis points on the target spatially separated according to a predefined pattern; and optical collection means for collecting the light emitted by interaction of the incident laser radiation with the target, said optical collection means having a field of vision in which said at least two measurement points are located. One or more spectrometer(s) is (are) used, to analyse the light transmitted by the optical collection means and generate LIBS spectral data. Optical fibre transmission cables transmit the laser radiation from the source to the measuring head, and the radiation collected by the optical collection means to the spectrometer(s).

Description

Mobile spectroscopic analysis device, in particular for geological analyzes

Introduction

The present invention generally relates to a device for analyzing the material by laser induced plasma spectroscopy ("Laser-Induced Breakdown Spectroscopy" in the English language, abbreviated to LIBS), and more particularly to such a device in a version mobile or transportable.

State of the art

Geology, mineral, gas or oil exploration, and other scientific or operational applications for exploration, on Earth or on other planets in our solar system, require specialized analyzes, particularly chemical ones, of sites judged interesting. These analyzes must be able to be conducted over distances of up to several kilometers over a number of very specific areas. The materials to be analyzed may vary (solid, liquid or gaseous) depending on the areas explored. It is a question of analyzing precisely the composition of the soil in the different zones of each site.

Remote observation by satellite (of the Earth and other planets) or by air (for the Earth), by various techniques, is more and more widespread, and more and more instructive because of the progress made in the field of instrumentation. But nothing beats the analysis in situ or, failing that, the deported analysis of collected samples, to really identify and quantify precisely the materials present, and thus evaluate the real interest of one or more site (s) .

The old geologist's step-by-step approach with his hammer still exists on Earth. It is supplemented, more and more often, by core samples followed by extensive analyzes of the carrots in the laboratory, using non-mobile instruments. But the process between exploration, selection, collection and analysis of samples is therefore very long and expensive.

In recent years, sophisticated instruments exist in portable version, allowing the geologist to go to analyze, in the field, some samples of his choice. These are for example LIBS spectrometers that probe the soil and deduce the elemental chemical composition of it on each point of sounding / measurement. This technique is becoming more and more widespread in field geology because, of all the techniques allowing a chemical analysis, it is practically the only one that allows in situ analyzes, directly in the field. It is indeed a technique of rapid analysis, without contact, and without sample preparation.

The LIBS analysis technique has many advantages over other techniques used in the laboratory: it is a quantitative, multi-elemental, sensitive, information-rich quantitative analysis technique (large and resolved spectra). It is versatile (all types of materials), direct (without sampling or sample preparation), non-destructive (ablated mass of the order of the g) and clean (without emission of gas). It is fast and flexible: analyzes in seconds, at surface and in depth (~ 1 mm without drilling, more if associated with a drill), in contact or at a distance, directly in the field, on site, or in the laboratory. Transportable LIBS instruments allow geologists to explore sites accessible by car and then on foot. The geologist should select the area and targets to be analyzed, then approach the unit for each sample or take samples for analysis. This is long and tedious, and necessarily limits the amount of samples selected and analyzed, and the size or number of areas analyzed. The geologist inevitably misses potentially interesting samples. And there are still many areas difficult or impossible to access, but very interesting.

While this is not necessarily critical in scientific applications, it is in the context of industrial applications (such as mining, gas or oil exploration) interested in the profitability of exploration operations. To date, outside the Earth, we have tried to do geology on the Moon (with a geological astronaut), then on Mars with geological "rovers". The last Mars rover of NASA (Curiosity) is equipped with an imposing laboratory of mobile geology. It contains a LIBS spectrometer (called "ChemCam"), placed at the top of a rotating mast, to allow the analysis of the surroundings of the rover over a distance ranging from 1 meter to nearly 10 meters. This is a major asset for the mission, because this instrument allows to pre-evaluate the soil and the Martian rocks of a site, to decide if the rover will move or not in contact with these targets for more in-depth analyzes. . Chemcam also participates in the rover's scientific mission of analyzing the sites explored in order to determine their suitability. The chemical analysis of the Martian soil makes it possible to evaluate if, in the past, the conditions necessary for the development of life could be met in the explored site.

Object of the invention

The objective of the present invention is to provide an improved LIBS analysis device, facilitating the chemical analysis of targets / samples, particularly in the context of in situ analyzes of exploration sites. General description of the invention

The subject of the invention is a LIBS analysis device which comprises:

- a source of laser radiation

- a measuring head with:

optical illumination (or irradiation) means capable of directing at least two separate laser beams towards the target to be analyzed (the term "target" designates any object to be analyzed, for example a cliff, a soil or any sample) , so as to form at least two spatially separated analysis points on the target, according to a predefined pattern and

optical means for collecting the light emitted by interaction of the incident laser radiation with the target, said optical collection means having a field of vision in which said at least two measurement points are located;

at least one spectroscopic detector (or spectrometer) for analyzing the light transmitted by the optical collection means and generating LIBS spectral data;

a first optical fiber transmission cable for transmitting the laser radiation from the laser radiation source to the optical illumination means;

a second optical fiber transmission cable for transmitting the radiation collected by the optical collection means to said spectrometer. The design of the device according to the present invention is optimized for a compact and mobile embodiment, facilitating the use of terrain. The optical illumination and collection means are integrated in a measuring head, connected to the laser source and the spectrometer by optical fiber (s) cables. This makes it possible to decouple the measuring head from the bulky and sensitive organs of the device. It will therefore be easy to move and position the measuring head, which is a comparatively light member, at a distance from the laser / spectrometer group. If the measuring head is damaged, it can be replaced, and the laser / spectrometer group is not affected. Similarly laser source parts and spectroscopic analysis may be replaceable modules for maintenance for example.

The optical illumination means are designed to work with at least two separate laser beams sent on the target to be analyzed, so as to form at least two spatially separated analysis points in a predefined pattern. The use of two or more laser beams makes it possible to probe several points on the target in a single measurement, that is to say for a single positioning of the measuring head with respect to the target, and this that the shooting with different Laser beams are done simultaneously (in parallel) or sequentially. This ability to probe a measurement zone at several points (and in a single measurement step) is particularly interesting in the case of heterogeneous samples, since this makes it possible to detect a heterogeneity of the material by the different LIBS responses obtained, which makes is not revealed by a measurement at a single point. Thus, the device according to the invention makes it possible to increase the spatial analysis resolution and the extent of the analyzed zone, while reducing the time required to cover this area. This is an important asset for operational and / or expensive exploration missions. It should be noted here that the firing sequence is generally operated by a control unit, from which the operator determines all the parameters of use of the apparatus, in particular: the mode of use of the laser source ( in particular the number or the rate of shots), the mode of acquisition and treatment of the spectra, as well as the mode of acquisition of the images or videos, and the sequencing of all this, etc.

In order not to mix all the spectra of the different points during the collection, this can be done by spatial separation (each measurement point has its own collection path). An alternative is to achieve a temporal separation, which can be done for example in the following way: one draws on the channel A, one collects the spectra of the different shots (one by one or by averaging according to the rate of recording of the spectra) then we do the same on track B.

This ability to conduct a survey according to a predefined matrix of points is of particular interest in the case of wearable devices, as this allows the rapid survey of a relatively large area with a high spatial resolution, since the distances between measurement points are fixed by the configuration of the device.

Indeed, the pattern of the measurement points is predefined by the design of the optical illumination means. The points of analysis can be distributed in various ways on the target to be analyzed, online or in grid or any other desirable arrangement. In practice, the distance between two points of measurement adjacent to the pattern is greater than or equal to half the diameter of an incident laser beam. Preferably, the distance between two measuring points adjacent to the pattern may be of the order of 1 to a few mm or more; it can be for example chosen between 2 and 30 mm depending on the spatial resolution targeted on the target. Depending on the number of analysis points and their spacing, we can cover a variable area of analysis around a few cm ² .

In the case of simultaneous shots, the laser source is sized taking into account the subsequent subdivision of the radiation (number of simultaneous measurement points that one wishes to obtain on the target). This is to ensure that the power of each of the laser beams formed by the optical illumination means is sufficient to vaporize the material, generate a plasma at each of the analysis points on the sample, and obtain a signal-to-noise ratio. sufficient for the chemical species to be detected, in accordance with the needs of the LIBS technique. Each of the different laser beams preferably follows a clean optical path to the target, the beams emerging from the optical laser illumination means contained in the measuring head. This is called an "illumination path" that generates a laser beam to form a measuring point. In this context, it is possible to provide at the level of the measuring head a beam splitter, a planar optical system, or based on discrete optical components or optical fibers, for example, making it possible to constitute several illumination channels. Several laser beams (parallel or otherwise) emerging from the measuring head are thus produced, and following each of the respective paths and distinct from the measuring head to the target, to form measuring points spaced for example from 2 to 30 mm. .

The number of laser shots per measuring point, and their cadence, can be adapted to the needs of the analysis (plasma intensity and signal-to-noise ratio obtained, detectivity of the chemical elements to be analyzed, concentration of the target in elements that one seeks to detect, alteration of the surface (dust, pollution ...), etc.). We can take advantage of the shock wave created on the target by the laser beam, to eliminate all or part of the dust deposited on the target, or to analyze it independently of the target and distinguish their own chemical composition. One can thus, according to the number of laser shots accumulated on a point, to distinguish the chemical composition of the surface of the target from that which one can find a little below this one. Indeed, depending on the properties of the target, the depth of penetration of the laser beam, after a few hundred or thousands of shots, can reach or even exceed 1 mm.

As indicated above, the illumination channels may, depending on the variants, be illuminated sequentially or simultaneously. The sequential case is the simplest to achieve. Example: we draw on the track A, we collect the spectra of the different shots (one by one, or by averaging them according to the rate of the shots and the need), then we do the same on the track B. An alternative to activate successively each measurement channel consists in playing on the direction of the source laser radiation, modified with the aid of an associated deflection means, for example a moving mirror, at the input of a beam splitter, in order to bring it successively towards each path of illumination of the target. As indicated, the collection can then be done by discriminating the spectra of each measurement point for example by their recording dates and the sequential (the order) triggering shots between the different points. For the case of a simultaneous firing on the different channels, the optical collection means are configured to allow spatial discrimination of the collected light. In the context of the present invention, the concept of simultaneous fire is used antagonistically to "sequential". The firing is simultaneous when the laser firing is carried out at the same time, or at least partially concomitantly, on at least two illumination paths. Thus, "simultaneous" is to be interpreted in a broad way, also synonymous with "in parallel", and does not require that the shots be initiated exactly at the same time or of the same duration. The simplest is nevertheless to have a single laser source generating the different measurement beams simultaneously. For simultaneous shooting at multiple points, a single collection channel with a field of visibility covering the set of measurement points. According to one embodiment, this collection path comprises a group of contiguous optical fibers, each fiber receiving light from a sub-region of the analysis zone comprising a single point of analysis. Alternatively, it is possible to envisage collection channels that are entirely spatially separated, configured to associate a (single) collection channel (and preferably spectral analysis) independent to a measurement point (and therefore to a laser beam). This ensures better isolation of the signals from each other, but weighs the collection and spectral analysis devices compared to previous solutions, making the system less compact and more complex.

The device according to the invention can be designed as a fixed analysis instrument. But the present device will preferably be realized as a portable or mobile analysis device, controlled by an operator or autonomous, the LIBS technique being ideal for field analysis, since it allows in situ analysis, fast, without contact, and without sample preparation.

The concrete form that the device will take for mobile use depends on the field of application and the type of use, which can be varied, on Earth, in the air or on another planet. For a field analysis, the device may comprise a gun that integrates at least the optical components of illumination of the target and collection of radiation from it. Such a pistol is easily manageable by a user on all types of terrain. Alternatively, the present device could for example be made as a portable laboratory measuring device, with sample holder for samples, samples or cores (possibly associated with a conveyor for them) or in the manner of an embedded device allowing remote measurements from the land or aerial exploration vehicle, on which it is embedded, as is for example the case for "ChemCam" aboard Curiosity on Mars. The laser source can be adapted from the Chemcam laser concept to be compact, robust to shocks and vibrations, and able to operate on a wide temperature range (eg -40 / + 40 ° C) without thermal regulation, and with limited power consumption. These are major assets for portable or embedded applications requiring compactness, lightness, robustness and low consumption.

The present device can implement all appropriate methods to carry out a LIBS analysis, in particular for spectral analysis, calibration, measurement data processing and elementary identification, in order to achieve qualitative chemical analysis. and / or quantitative targets. The present device is not reserved for geological analyzes: it can find application in all kinds of fields (as described above), for the chemical analysis of solid, liquid or gaseous samples.

The LIBS analysis does not require target or sample preparation, but it may nevertheless be necessary, depending on the case, to prepare the surface of the target or of the sample, by cleaning or abrasion (to go further than the effect of the laser shock wave), or to withdraw from the material, for example by drilling, to carry out the deeper analysis in the target or the sample relative to the depth accessible by accumulation of laser shots .

Advantageously, certain constructive arrangements will be made to improve the robustness of the device, especially for use in the field, portable or mobile, and in particular the robustness of the laser source and the measuring head which must be stable under the various conditions use. For example, the measuring head is advantageously designed without moving parts. It can define an optical guide path for the laser beams by means of assembling different fixed optical elements. The optical guiding means may comprise a laser beam waveguide to be conveyed to generate a respective measurement point, in particular based on fixed optical elements, preferably designed from one or more elements chosen from: fibers optical fiber couplers, mirrors, lenses, dichroic blades, separator cubes, and planar guides.

For example, the separation of the laser radiation in two or more beams can be provided in the measuring head by means of an optical fiber coupler or integrated optics.

The power supply of the analysis device can be done by wired connection to an electrical distribution network, but for portable versions is preferably by a battery that can be recharged by any appropriate means: electrical network, heat engine, solar panels ... The present device advantageously incorporates an imaging module, in particular a high resolution color imaging module that makes it possible to take photographs of the analysis zone, before and after the laser impact, or even videos of the sequence of 'analysis. The combination image / chemical analysis is very useful for the geologist, for example. It allows him to know the context of the analysis: to recognize the type of rock or soil analyzed, to identify the possible presence of inclusions, to see if there is dust on the analyzed area (and, on Earth, plants).

The analysis device LIBS can be completed by complementary analysis means, for example a Raman spectrometer which can benefit from the same means of illumination and collection, or from a specific illumination path, the irradiation of the the sample being made at the desired wavelengths with the laser source (for example with doubling of its nominal frequency for the Raman pathway to gain compactness), or another laser source.

The present LIBS analysis device can be embarked on a land or air exploration vehicle, for example, to travel or to travel on an exploration site. This vehicle can be a mobile robot on the ground and / or in the air and controlled remotely, or moving in a pre-programmed or autonomous way. By way of example, mention may be made of a land vehicle controlled remotely (car or exploration rover), a drone, a gas balloon, etc. The vehicle preferably comprises means for moving on the ground, or in the air, and stabilizing in front of, against, or above the area of analysis, to provide stability of the line of sight for laser shooting, spectral collection and image taking. This stability is necessary the time of the analysis (a few seconds to a few tens of seconds for the LIBS illumination part, a few tens of seconds to a few minutes maximum for a complete sequence including the spectral analyzes and the taking of images). Associating the present analysis device LIBS with a mobile robot able to move on the ground (equipped with wheels, tracks or other) or in the air, is interesting for example when an operator can not be present or sufficiently close to the site: dangerous or inaccessible areas, space exploration, etc.

However, the remote remote control of such robots remains complex and requires the utmost precaution not to damage the robot and its equipment (and to ensure control of the movement of the robot). In the case of the Curiosity rover, which has been exploring Mars since August 6, 2012, its piloting is ensured by a large team of humans, ensuring together the choice of the route taken by the rover and sites analyzed, the safety of the rover and the instruments, and to fulfill the scientific objectives of the mission. But the necessarily limited state of knowledge of the terrain requires the greatest caution in the movement, so that some areas remain inaccessible, particularly because of the relief. The geological analysis process can in no way be broad and exhaustive, and potentially interesting targets can be ignored on the way. Compared to a robot on the ground, a drone has the advantage of being able to fly over the obstacles of the ground, which makes it possible to bring the device of analysis in places inaccessible for a rover. A drone may also take measurements on inclined or vertical walls that are not or not accessible by other means. In the present text, the term "drone" means any remote-controlled aircraft flowing without any person on board, and generally capable of loading a load. For certain proximity applications, the flight can be done in direct view by a ground operator (the remote pilot), via the command and control system on the ground. For explorations out of sight, the drone evolves preferably in an "automatic" way, that is to say that its evolution in flight was programmed by whatever means before the beginning of the flight, and / or is put in day during the flight, and that all or part of the flight is carried out without direct intervention of the operator, except exception or mode of emergency control. To perform flight measurements, the drone has a hover capability, that is, it can be controlled to maintain a position substantially immobile flight from the ground.

The combination of the drone and the LIBS analysis device allows sufficient coverage at the scale of geologically interesting sites, whether on our planet or on another, and meets the following criteria: - fast access;

- significant mobility;

- ability to access areas that are not or not accessible to humans, or that are dangerous for them;

- ability to cover multiple areas or large areas, in a single field analysis campaign, to account for land variability;

- flexibility to cover all types of terrain (soil, air, rough terrain, etc.).

According to another aspect, the invention therefore proposes a drone embedding the present analysis device LIBS, which makes it possible to increase the capacity of in-situ analyzes and the quantity of targets and / or samples selected and analyzed, the drone being able to carry out reconnaissance missions, exploration and in-situ geological analyzes on grounds larger than those covered by a human geologist or a classic rover, or even more rugged or difficult to access.

Preferably, to carry out a measurement campaign, the drone / analyzer unit LIBS is equipped with means to enable it:

- Perform (automatically or semi-automatically) a large-scale visual identification to analyze a site and determine areas of interest, for example using a wide-field camera;

- Then realize (automatically or semi-automatically) a more focused location, to analyze areas of the site and targets of interest, for example using a smaller field camera but higher resolution; - then perform (automatically or semi-automatically) soil composition analyzes or selected targets;

- and possibly to collect some interesting samples to bring them back to the base or in the laboratory, for further analyzes, by other techniques.

For some measurement campaigns, we can provide a mounting of the present LIBS analysis device on the drone, so as to allow its decoupling, to deposit the LIBS analysis device on a measurement site. In such a case, the LIBS analysis device can be mounted on a mobile mini-robot (rover type), transported by the drone.

The drone allows air travel on Earth, Mars or other. After landing, the mobile mini-robot equipped with the present analysis device separates from the drone for exploration on the ground, and returns to the drone at the end of the campaign. The robot is preferably autonomous, and as part of a multi-phase exploration, can enter the drone (to recharge, communicate information or data collected) between each phase, or simply chain the different phases and return to the drone after the last phase.

In the context of a robotic planetary exploration (like the Mars exploration for example), with a large rover (Curiosity type), we can envisage the association of a main rover equipped with instruments of geological analysis sharp, and a drone equipped with reconnaissance cameras and a mini LIBS instrument installed on board or detachable via a mini-lander or rover (annex). This combination would allow for wider exploration around the main rover, increasing the area covered by the mission, and the ability to select the most interesting areas before involving the main rover / laboratory. This would significantly increase the effectiveness and the lifetime of the mission. The main exploration rover is used to: - transport the drone to the exploration site via another vehicle for very long distances (transnational, transcontinental, trans- oceanic, or for the exploration of another planet),

- store and recharge the drone during the non-use phases

- transmit the data collected by the drone to the earth, transmit to the drone data, commands or programs sent by the Earth

- and make more in-depth analyzes of the site or samples possibly reported by the drone.

In this case, the drone is an assistant, lighter and much more mobile, exploration rover, but containing fewer instruments (only recognition and exploration imagers, LIBS or Raman spectrometer, and possibly a clamp for the collection of samples, for further analysis by the rover). This can be possibly combined with the previous case, a drone carrying a mini-robot. Miniature devices, used in mobile telephony and for terrestrial imaging mini-drones, can be used for the equipment needed for the drone (food, motorization, localization, navigation and imagery in particular ...).

In addition to the examples of terrestrial or spatial geology, the combination of the present LIBS analysis device with a mobile robot (for example, rolling or aerial) may find application in a variety of circumstances, for example:

- restoration of historical monuments: exploration of the site by an autonomous robot (eg quadri-rotor) equipped with the present analyzer avoids scaffolding, and a human to carry the device or the LIBS pistol by hand to make analyzes . This allows a complete, regular and accurate coverage of the entire surface of the monument (cartography + analysis) in a shorter time.

- industrial sites or transport or hazardous storage areas: automatic leak analysis or evacuation of liquids or gases, waste, etc. Examples: automatic inspection of sites containing gas pipelines, or hazardous material storage areas, analysis of hydrocarbon exploitation sites ... river analysis, atmospheric or marine pollution, etc. analysis of sites conducive to oil or mining exploration.

Description of the Figures

Other features and characteristics of the invention will become apparent from the detailed description of at least one advantageous embodiment presented below, by way of illustration, with reference to the accompanying drawings. These show: FIG. 1: a block diagram of the LIBS analysis device according to the invention; Fig.2: a schematic diagram of the pattern of measurement points; Fig.3: a diagram of a variant of the measuring head;

Fig. 4: a schematic diagram of the internal construction of the measuring head of Fig.3; Fig. 5: a diagram of another variant of the present analysis device;

Fig. 6: a diagram illustrating the device of Fig.5 in a portable version backpack;

Fig. 7: a diagram of the present analysis device LIBS mounted in a drone;

Fig. 8: a top view of the present analysis device LIBS mounted on a quadri-rotor;

Fig. 9: a front view of Fig.8;

Fig. 10: a diagram of an alternative measurement process of the present LIBS analysis device associated with a drone;

Fig.1 1: a) schematic diagram of a measuring head according to another embodiment, and b) pattern of the corresponding measurement points on the target. Detailed description of at least one embodiment

1. General principle of the present analysis device

Fig. 1 illustrates a block diagram of a variant of the present analysis device 10, which comprises: a laser radiation source 12; a measuring head, generally designated 14, comprising:

optical illumination (or irradiation) means capable of directing the laser radiation onto an object 15 to be analyzed according to the LIBS technique; and optical collecting means for receiving / sensing the radiation

(the plasma light) emitted by the target after laser firing.

The reference sign 18 designates a spectroscopic analysis system of the captured optical signals. A first optical fiber transmission cable 20 is provided for transmitting the laser radiation from the source 12 to the measuring head 14. A second optical fiber transmission cable 22 is provided to transmit the light collected by the optical collection means to said spectroscopic analysis system 18.

It will be appreciated that the optical illumination means are designed to direct, and preferably focus, at least two separate laser beams 24 towards the target, so as to form at least two spatially separated analysis points 26, positioned (distributed ) in a predefined pattern. The at least two analysis points 26 are positioned in the field of view of the collection means (that is to say in the area that falls in the opening angle of the collection means). In Figs. 1 and 2 the field of vision is represented by the indicated dashed circle 28. FIG. 2 shows, for example, a pattern with 2 measuring points on the surface of the target 16, obtained by the two laser beams 24. But also provide 3 separate laser beams, and the third corresponding measuring point would be eg. the indicated point 26 'in Fig.2. The characteristics (including wavelength and energy density) of the laser beams 24 are adapted to heat the material, vaporize a small amount of material and create a plasma at each of the points of analysis 22. The spectroscopic analysis of the light of this plasma allowing the identification of the chemical elements constituting the material of the target, according to the technique LIBS.

The light emitted by the plasma produced by the laser pulses on the surface of the target, at each analysis point 26, is thus picked up by the optical collection means and transmitted to the spectroscopic analysis system 18 ( generally comprising at least one spectrometer associated with a detector). The spectrum obtained (LIBS spectrum) describes the chemical species that made up the small piece of sublimated target. The LIBS spectrum, or part of it, can be compared to reference values in a database to identify these species. The laser source may be any source adapted to provide one or more laser beams, whose power density for each measurement point makes it possible to vaporize and ionize a portion of material on the surface of the target (typically a density of 1 GigaWatt is required / cm ² at a wavelength of 1064 nm, with short pulses of 5 to 8 ns). An example of a suitable laser is a diode-pumped solid-state laser, such as an Nd: YAG laser emitting at 1064 nm.

Another type of laser source possible is a Nd: KGW solid-state laser source such as manufactured by Thalès Laser (France) in collaboration with CNES, for the ChemCam instrument installed on the Curiosity rover for the Martian Mars Science Laboratory ( MSL). It is a stable laser source over a wide temperature range (-30 / + 30 ° C), which does not require active cooling, and capable of producing an energy of the order of 30 to 40 mJ at 1067 nm, with pulses of 5 to 8 ns, and a rate ranging from 1 to 10 Hz.

The Chemcam laser is resistant to vibrations, shocks, daily and seasonal thermal cycling, and radiation from the MSL mission. For more details on ChemCam, its laser, the optical means of illumination and collection, and associated electronics, one can refer to the article published in the periodical Space Science Reviews, no. 170, 2012: The ChemCam Instrument suite on the Mars Science Laboratory (MSL) Rover: Science Objectives and Mast Unit by Maurice, S., Wiens, R., Saccoccio, M. The LIBS analysis technique, which he The choice of laser, spectral analysis of plasma light, spectral data processing, and calibration is widely known and will therefore not be described further here. Those skilled in the art are able to select the appropriate components and methods to implement it in the context of the present invention. In general, the device includes a control unit, indicated

17 in FIG. 1, which makes it possible to implement the measurement LIBS and also controls the operation of the device 10. As will have been understood, the present measurement principle involves a plurality of shots on different measurement points. At the level of the control unit, this multi-shot method is implemented by the device in an automated way (whether sequential or parallel), whereas the user gives only one instruction to carry out a procedure. measurement (and not as many measurement instructions as laser beams).

Preferably, the laser source 12 and the spectrometer 18 are combined in a same box, housing or support, with the control unit 17, which will be referred to hereinafter laser / spectrometer group 19, or L / S group 19.

2. Variations of realization of the measuring head

The measuring head 14 is illustrated in perspective in FIG. 3, in a variant comprising a parallelepipedal casing. On the front face 30, there is symbolized:

the emission zones of the laser beams 24, from which the laser beams emerge, which are indicated by the circles 32.

the collection means which are embodied by the circle 34. The head 14 here comprises two indicated imaging sensors 36 and a sensor. distance sensor 38 (range finder). One of the imaging sensors can be a high resolution (or HD) color sensor and the other a large field imaging sensor.

The laser radiation is transmitted by the first cable 20 from the source 18 to the measuring head 14. The laser radiation is guided, oriented and / or distributed in the measuring head 34, so as to emerge from it several beams laser according to respective predefined directions, to provide spatially separated analysis points on the sample, according to the predefined pattern. Thus, the measuring head comprises internal optical elements for directing the laser radiation on different channels, each channel allowing the formation of a next laser beam at the output of the measuring head, a clean optical path for irradiating the sample at the desired measurement point, depending on the pattern. The laser beams may have directions parallel to each other, or not. Preferably, the first transmission cable 20 comprises an optical fiber for each of the laser beams 24 emitted by the head 14. It is advantageous to work with a single laser source, in series with a beam splitter, from which the independent beams are sent. in the respective fibers. This solution is preferred for reasons of compactness, weight and simplicity.

Alternatively, one could have a laser beam laser source to emit at the measuring head 14.

Alternatively, we could use a single optical fiber that sends the radiation to the measuring head, and divide the radiation in the measuring head. The mounting of the source is then very simple, but it is necessary to integrate more optical elements in the measuring head.

In the variants shown, the first cable 20 thus comprises two optical fibers each carrying the laser radiation to form the respective beam 24. The cable 20 arrives for example at the rear 38 of the head 34 and the fibers are connected to the illumination means.

The illumination means may be designed in any suitable manner it is required to guide the laser radiation from the optical fiber to the front face of the head, and to emerge the laser beams 24 in the desired directions. Illumination means without moving parts will preferably be used.

An exemplary embodiment of the measuring head 14 is schematically illustrated in FIG. The first cable 20 comprising two optical fibers 20a, 20b arrives at the rear of the measuring head 14; the ends of the optical fibers 20a, 20b are connected to the rear of the optical structure appropriately. Rather than an arrival with two fibers 20a, 20b, one could use a single fiber arriving at the input of the head 14 on a coupler (used as a divider) of optical fiber beams, or integrated optics. A set of internal optical fibers 23 (or other optical elements) is arranged so as to define an optical path leading the laser radiation from each fiber 20a, 20b, inside the head 14, and to emerge by the face 30 a laser beam 24 in a predetermined direction with the spacing chosen between beams 24. The laser radiation provided by the optical fibers 23 therefore leave through the front face 30 of the measuring head 14, in predetermined directions, forming the beams 24, in order to strike the sample 15 at the two measuring points 26 in an area coinciding with the field of view 28 of the collection means 34. In FIG. 4, the ends of the internal fibers 23 are represented by rectangles 23i which include the fixing means of these fibers at the rear of the front face and, if necessary, optical focusing elements.

The collection means 34 are preferably simplified to the maximum by bringing the end of the second optical fiber cable 22 closer to the front face 30 of the measuring head 14.

The cable 22 may comprise one or more optical fibers. A single optical fiber is sufficient for purely spectral discrimination of the collected light; in this solution the signals in response are averaged but allow the identification of the different spectral lines, and thus the elemental analysis of the sample.

One can alternatively use a multifibre cable, which also allows spatial discrimination of collected radiation (one fiber per measuring point).

Single-mode or multi-mode fibers may be employed.

It is highly desirable that the plasma light to be captured be focused on the collection means 34. For example, lenses may be added to the end of the fiber (s), for example a lens doublet. Alternatively, lentil fibers may be employed, if the working distance is appropriate, and in the desired arrangement. As is known, a lenticular fiber is a fiber whose end is spherical, thus forming a lens allowing beam focusing (instead of letting it naturally diverge). It can also be inversely used for illumination, provided that its working distance is not an inconvenience for laser illumination and / or imaging.

In FIG. 4, the reference sign 40 symbolizes the doublet of lenses which makes it possible to focus the plasma light on the core zone of the fiber end 42.

Depending on the variant, we can combine the LIBS technique with Raman. For example, provision may be made for the transmission of an additional laser beam from the head (eg frequency-doubled LIBS laser beam) for a Raman interrogation of the target. This additional laser beam is separated from the others, and strikes the target at a point of analysis spatially separated from the others, provided in the pattern of the analysis points.

The collection of radiation from the Raman interrogation is done by the collection means 34, but the spectral analysis is normally performed in a dedicated spectrometer.

Referring to Figs.1 -3, when working with two laser beams LIBS, Raman interrogation can be done by the ^3rd laser beam 24 which strikes the sample at 26 '. The laser radiation to the Raman can be from the same source 12, for example by taking the ^2nd harmonic at 532 nm in the case of a source at 1064 nm. The 532 nm radiation can be extracted at the source by a suitable optical assembly, comprising by for example a beam splitter and a mirror at 532 nm.

The Raman technique is well known, as well as its combination with the LIBS technique. Those skilled in the art are able to condition the laser radiation appropriately, as well as to analyze the measured radiation.

Another alternative embodiment of the measuring head is shown in Fig. 1.1 (a). This measuring head 60 comprises 4 irradiation channels (3 for the LIBS analysis, denoted 62, and one for the Raman, denoted 62 ') and a central collection channel 64. The 4 irradiation channels 62, 62' are arranged in a square. The 3 laser paths 62 are formed in a manner similar to the variant of FIG. 4. The laser radiation arrives by optical fiber and is distributed over 3 internal optical paths formed by optical fibers which constitute the laser illumination channels for the interrogation. LIBS. The laser radiation required for Raman analysis (whose wavelength is different - eg 532 nm) is preferably directly fed from the laser source. The illumination channels 62, 62 'are preferably positioned for laser beams in parallel directions, then forming on the object to be analyzed a matrix pattern of 4 measuring points whose spacing is the same as that of the beams emerging from the measuring head. Fig. 1 1 b) thus shows the 4 measurement points obtained on the sample: 3 measurement points for the LIBS interrogation, indicated 66, and a point corresponding to the Raman interrogation, indicated 66 '. All measurement points are located in the field of view 68 of the collection means.

The collection can be done in a simple way with a single optical fiber in the central position, and by firing sequentially on the different channels, which makes it possible to discriminate the measuring points simply on time basis, provided that the collection is focused on the measurement points.

However, in the present variant, the central collection path is designed to allow the spatial discrimination of the light collected during simultaneous shots on all the channels 62, 62 '. To do this, the collection route The central unit 64 comprises an assembly of 4 optical fibers 64 ₁ ... 64 ₄ which thus enables the segmentation of the field of view 68 into four regions 68 ₁ ... 68 ₄ each covering a respective measuring point.

3. Exemplary embodiment of the present device in a standalone and portable version

One embodiment of the present autonomous and portable analysis device 200 is illustrated in FIG. 5. The measuring head 14 is designed as described in section 2 above, in relation to FIG. 4, and is therefore coupled to FIG. a laser source 212, installed in an L / S group 219, by means of a first optical fiber cable 220. The measuring head 14 is able to generate two (or more) laser beams 24 separated spatially and focused on the sample 15 to be analyzed, so as to form several points of analysis.

The laser source 212 is adapted to the optical system so that its power is sufficient to heat the material at the point of incidence of each of the laser beams 24, vaporize the material and create a plasma to allow elemental analysis by the LIBS technique. .

As explained above, the light of the plasmas created at the measurement points is collected by the collection means 34 and transferred to the L / S group 219 via the second cable 222, for the purpose of spectral analysis by means of LIBS 218 spectrometer. The LIBS 218 spectrometer can be based on any suitable technology, in particular a prism or a diffraction grating. The LIBS spectrometer realizes the spectral dispersion of the harvested plasma radiation, the acquisition thereof being carried out by means of a vector or matrix photon detector 250, for example a CCD or iCCD detector (intensified Charge Couple Device). The L / S group can contain several spectrometers in order to analyze several wavelength ranges and thus access a wider range of chemical elements.

Reference numeral 252 denotes a Raman spectrometer also receiving radiation from the sample following interrogation thereof with laser radiation at an appropriate wavelength (as explained 2), or with another light source. The Raman 252 spectrometer can be based on any appropriate technology. The Raman spectrometer performs the spectral dispersion of the harvested plasma radiation, the acquisition thereof being carried out by means of a vector or matrix photon detector 254, for example a CCD or iCCD detector.

The imaging sensors 36 equipping the measuring head 14 allow the acquisition of images of the current analysis area of the target before and / or after the laser impact or the video capture of the analysis sequence. A cable 258 connects the imaging sensors 36 to the L / S group, for example to an image processor 260.

The rangefinder 38 of the measuring head 14 makes it possible to determine the distance to the target, and can also be used in an automatic control loop when the head is mounted movably, or else in the automatic focusing control system. imagers or measuring equipment (LIBS or Raman). In particular, the distance measured by the rangefinder can be used as a trigger for the measurement, when the measuring head is at the right distance.

A computer control unit 226 comprising a microprocessor is provided for managing the device 200, in particular implementing the measurement in accordance with the LIBS technique, essentially operating the laser shots, collecting the radiation following the laser interrogation, acquiring the spectra and images. The analysis of the spectra can be done in the device, or these can be stored (DATA 261) and / or transmitted for analysis in another more powerful computer system. The reference sign 262 indicates a communication module for remote communication with the device 200, with the separate interface 254 ', and the data exchange.

A user interface 254, 254 'communicates (wired or wireless) with the control unit 226 to enable a user to control the analyzer 200. A cooling module 256 is provided, particularly for cooling the laser source 212, to ensure its optimal operation and its stability (need depending on the chosen laser source).

A power supply module 258 provides the energy necessary for the operation of the device 200. It preferably comprises a battery that can be recharged by connection to the network or to a generator. In space exploration or other missions where the supply of electrical energy is limited, the generator may include solar panels.

According to the variants and especially according to the desired applications, provision can be made in the device 200:

a rangefinder 264; a GPS sensor 266 used by the control unit for searching, locating and targeting.

A video camera 268 provides dynamic color images in real time of the area to be analyzed, or more generally areas of interest. Such a camera 268 can also be used to categorize the targets observed according to their morphology, color, shape or heterogeneity, for example. The video camera 268 may use ambient light or artificial light, such as laser light, to illuminate the target area. One can consider embedding a wide field camera for site reconnaissance and a high resolution camera and smaller field for target identification and analysis area.

4. Examples of applications - portable unit

As explained above, the present device has been designed for on-site / field use. The device can be mounted on board a vehicle (land, air, ...) driven by a user (car, trolley, etc.) or controlled remotely (radio-controlled vehicle, drone ...).

The L / S group 19 is generally safely installed in the vehicle, while the measuring head 14 can be eg. positioned on a fixed arm or mobile (robotized), thanks to the facility provided by the optical fiber ensuring communication between the laser / spectrometer group and the measuring head, and the compactness and lightness of the latter.

We can also consider simply portable versions, since the laser / spectrometer group is small, and the measuring head can be integrated in a kind of gun that is hand-held by the user. The laser unit can be installed in a common box, provided for example with handles. It can also be installed in a suitcase or bag.

FIG. 6 illustrates an exemplary embodiment, in which the laser / spectrometer group 19 (of FIG. 1) is installed in a backpack 300, and the measurement head 14 is integrated in a gun 302. A cable 304 includes optical fibers carrying laser radiation and collected light, and other cables needed for imaging and telemetry where appropriate.

Another advantage of the gun format is to be able to define a measurement distance. In the illustrated example, the measuring head is in fact installed in the gun-shaped housing 306, and the front face 14i of the measuring head 14 is turned towards the opening 308 of the housing. By design, it is possible to fix the distance D between the front face of the measurement head and the front edge 310 of the gun (it is therefore a front edge of depth D). In this context, to facilitate the measurement, the focal distance of the illumination and / or collection means can be substantially coincided with this distance D. Thus, by plating the front edge 310 of the gun 302 against the object to be analyzed, we focus directly on the focal length, optimizing the laser energy applied to the analyzed object as well as collecting the light from the generated plasmas.

5. Examples of application with drones

With reference to FIG. 7, the LIBS analysis device 200 described above (section 3) is combined with a drone (remotely controlled or moving aerodyne in a pre-programmed or "intelligent" manner), to take measurements along a rocky cliff, a facade of historical monument or in an industrial site or exploration or oil exploitation. The analysis device 200 is thus embarked by the drone 400, which makes it possible to rapidly position the analysis device 200 along the cliff 402, at any desired location. For each measurement, the drone 400 is operated in stationary mode.

The multi-rotor drones are also used because they have the combined advantage of a great simplicity of design, a great ease of use and application, and above all are at costs that remain affordable, using technologies miniature and modern especially used in mobile telephony.

The measurement zones can be decided by an operator in a visual mode. Alternatively, all the measurement zones can be decided in advance, and the drone then follows a flight plan, in automatic mode, the latter moving towards each of the predefined measurement zones. In an even more sophisticated version, the drone can move in an "intelligent", that is to say, self-adaptive, using its various embedded sensors and predefined flight laws.

To optimize the measurement campaign, we can proceed to a prior reconnaissance by the drone, which will acquire images of different parts of the cliff, and make a human selection and / or image processing, different areas of analysis to cover then by LIBS analysis with the drone.

In the variant of Figure 7, the drone is of the helicopter type. The group L / S 219 is installed centrally in the drone 400, for the needs of balance. The measuring head 14 is offset by means of an arm 404 which is fixed under the body / fairing 406 of the drone 400 and extends horizontally, beyond the perimeter of the fairing of the drone and the blades. This allows the drone 400 to approach the measuring head 14 very close to the wall. We can consider putting two measuring heads in symmetrical positions on both sides of the drone to balance it, double the number of measurement points and / or constitute a redundant measurement path in case of malfunction of the first.

In addition to the usual means of navigation aboard the drone, we will use eg. a range finder for positioning the drone 400 at a predefined distance from the wall 402 to make the measurements. This especially in a case without autofocus, or limited refocusing race.

In practice, the drone is preferably operated so that, at the time of measurement, the measuring head 14 is closer to the wall, for example between 1 and 20 cm, or even in contact therewith. This depends on the focusing capabilities of the measuring head.

8 illustrates a variant in which the drone is a quadri-rotor 500. It conventionally comprises four lift rotors 502 carried by arms 504 extending from a central body 503, the arms thus forming a cross. In order to prevent the apparatus from rotating on itself on its yaw axis, two rotors 502 rotate in one direction, and the other two in the other direction, the rotors rotating in the same direction being placed at the opposite ends. of a branch of the cross. A fairing 506 is fixed to the central body 503 and surrounds the rotors 502 (propeller + motor).

To take off a multi-rotor, just apply a voltage identical to each engine (they all turn at the same speed). The increase in speed allows takeoff and positioning at altitude.

As is known, the movements (yaw, roll, pitch) are then obtained by varying the speeds. Thus the number of control parameters is dependent on the number of motors. These control aspects of multi-rotor drones are widely known to those skilled in the art and do not require further development here.

For the LIBS measurements, the laser / spectrometer group 219 is installed in the central body 503, or fixed beneath it. The measuring head 14, which is small and of low weight, can however be fixed on an outside of the fairing 506. If necessary, a counterweight can be positioned opposite, or a second measuring head to balance the drone, while offering either a doubling of the measuring points, ie a redundancy at the measuring head.

The examples of UAVs presented above are not limiting. Various types of drones can be used, and will be selected according to the desired load capacity and autonomy. Multi-rotor drones capable of carrying a payload between 6 and 10 kg, and having a range of between 10 and 20 minutes are already used for various applications, such as laying high-voltage lines, coastal rescue ... Such drones are quite suitable for use in the context of the present invention. In addition, the drone can be equipped with a clamp at the end of a robotic arm, for the collection of samples to be analyzed more finely on a basis brought to the site or laboratory.

In some applications such as monument restoration, LIBS measurements are used to analyze coatings. Drones can then be used to take measurements on facades, vaults of cathedrals, or internal walls of buildings, without the use of scaffolding. Again, the measuring head can be placed on the fairing or at the end of an arm or pole.

In this kind of application, to overcome the problem of autonomy, we can quite consider a drone (electric) powered by wire.

6. Example of a measurement sequence

In general, the present device is operated by a control unit, such as the control unit 226 which, in particular, manages the measurement / acquisition sequence, that is to say the triggering of the firing, the collection. of plasma radiation - LIBS, and the acquisition of images.

A preferred variant of a measurement process is illustrated in Fig. 10, in the context of use with a drone.

Step 600 refers to the approach phase, during which the drone approaches the area to be analyzed. The positioning in this analysis zone can be done on sight, or by video camera information, or on the basis of a positioning system.

As long as the analysis zone is not reached, the process loops back to step 600 during the movement of the drone.

Imaging (step 602) before laser firing is optional, but it can be useful for comparing the target, before / after laser firing, setting the context of the analysis, and locating it precisely.

Once the position reached (step 604, "YES"), the command gives its ok to proceed to a shooting phase. Advantageously, the firing phase includes a thin positioning phase, which aims to ensure the focusing of the measuring head 14. For a fixed optical system of the measuring head, the position of the drone is adjusted to position the zone to be analyzed in the focal plane of the optical system, so as to optimize the collection of the plasma radiation that will be created by the laser interrogation. This can be done by distance measurement or telemetry. Once the focal length is reached (symbolized by a Focus flag = OK in step 606), the firing is fired (step 608).

In the case of an autofocus block, it is not necessarily necessary to measure the distance, but the transition to the firing step 608 may be authorized by a flag FOCUS = OK given by the autofocus block.

The collection system connected to the spectrometer (s) comes into play to collect and acquire spectra of the plasma radiation created by the laser shot. The control unit also triggers the acquisition of a post-shot image (step 612), preferably by means of the indicated imaging sensors 36. A slight offset will generally be provided between the laser firing and the acquisition, for take into account the delay between excitation and emission of the target.

It is clear that the firing includes the emission (in parallel or sequential) of the at least two laser beams for the interrogation LIBS, and / or if necessary the laser firing for the interrogation Raman. If a Raman firing is done, the acquisition phase then includes the acquisition of the Raman spectrum. As indicated above, depending on whether the shot is sequential or in parallel, one separates the acquisition of measurement points, either temporally (emission and collection shifted to different points) or spatially (a separate collection path for each measurement point).

It will also be noted that for each measuring point, the laser shots and the acquisition of the plasma light are in practice repeated a certain number of times, e.g. a few tens or hundreds of times (gunshots generating a spectrum per shot). The collected light is sent to the spectrometers and processing means for analysis. Depending on the operating modes, each laser shot provides a spectrum, or several shots can result in an integrated or averaged spectral acquisition. We can also increase the number of laser shots up to several thousand, to penetrate deeper into the target and perform a spectral analysis depending on the depth. This can make it possible to identify variable properties / compositions between the surface and the inside of the target. This type of use requires increased stability of the illumination / collection lines of sight.

In accordance with step 614, the shooting data, e.g. time, date, coordinates, spectra, images, are then transmitted to the ground or the base, for analysis and analysis.

Claims

claims

LIBS analysis device comprising

a source of laser radiation (12; 212)

- a measuring head (14; 60) with:

- optical illumination means capable of directing at least two separate laser beams (24) towards a target to be analyzed (15), so as to form at least two measuring points (26; 66) spatially separated on the target, according to a predefined pattern and

optical means for collecting the light emitted by interaction of the incident laser radiation with the target, said optical collection means having a field of view (28; 68) in which are located said at least two measuring points (26: 66 );

at least one spectrometer (218) for analyzing the light transmitted by the optical collection means and generating LIBS spectral data;

a first optical fiber transmission cable (20; 220) for transmitting laser radiation from the laser radiation source to the measurement head;

a second optical fiber transmission cable (22; 222) for transmitting the radiation collected by the optical collection means to said spectrometer.

The LIBS analysis device according to claim 1, wherein the optical collection means comprises a collection path (34) whose field of view encompasses the different measurement points created by the laser beams.

LIBS analysis device according to claim 1 or 2, wherein the optical collection means are made by a portion of optical fiber 42 fixed in the measuring head to which is preferably associated a focusing optics (40) for focusing the collected light onto the input face of the optical fiber portion.

The LIBS analysis device according to claim 1, wherein the optical collection means comprise at least two collection channels (64) whose fields of view (68) are suitable for covering the set of measurement points. (66), in particular the collection means comprise a collection path having a respective field of view per measuring point, the collection paths preferably being grouped centrally.

The LIBS analysis device according to any one of the preceding claims, comprising a control unit (17) configured to manage the LIBS analysis by operating jointly or sequentially the laser shots with said at least two laser beams.

The LIBS analysis device according to any one of the preceding claims, wherein the measuring head (14) comprises at least one imaging module (36).

7. LIBS analysis device according to any one of the preceding claims, wherein the measuring head (14) comprises at least one distance measuring means (38) between the measuring head and the target in order to adjust the distance. work and optimize focus. 8. LIBS analysis device according to any preceding claim, wherein the optical illumination means comprise optical guiding means configured to guide the laser radiation from the first transmission cable, and form and emerge from the measuring head said laser beams (24) separated, so as to form on the target said analysis points (26, 66) according to said predefined pattern.

9. LIBS analysis device according to claim 8, the optical guiding means comprise a laser beam waveguide (23) to be routed to generate a respective measuring point.

The LIBS analysis device according to claim 9, wherein the waveguides are based on fixed optical elements, preferably designed to firing of one or more elements selected from: optical fibers, fiber optic couplers, mirrors, lenses, dichroic blades, separator cubes, and planar guides.

1 1. The LIBS analysis device according to claim 8, 9 or 10, wherein the optical illumination means comprises focusing means for focusing the laser beams on the target.

12. Mobile LIBS analysis system characterized in that it comprises a mobile robot and a LIBS analysis device according to any one of the preceding claims embedded on this mobile robot. 13. Mobile LIBS analysis system according to any one of the preceding claims, wherein the mobile robot is remotely controlled by an operator by means of a control and control unit; and / or configured to move in a pre-programmed and / or self-adaptive manner.

The mobile LIBS analysis system of claim 13, wherein the mobile robot is a drone (400, 500) having a hover capability.

The mobile LIBS analysis system according to claim 12, 13 or 14, wherein the measuring head (14) is installed at the end of a laterally extending measuring arm (404), the laser source and the spectrometer (s) being positioned centrally in the mobile robot, respectively the drone. 16. Mobile LIBS analysis system according to any one of claims 12 to 15, wherein the mobile robot, respectively the drone, comprises a sampling gripper.

17. Mobile LIBS analysis system according to any one of claims 12 to 16, wherein - the mobile robot is able to move on the ground; and

- The mobile robot is associated with a conveyor UAV, configured to transport the mobile robot and allowing its decoupling when on the ground.

18. LIBS analysis system according to any one of claims 12 to 16, wherein the mobile robot is associated with a host device, in particular a main robot, for transporting, storing and / or reloading the mobile robot, and for transferring data to the base.