WO1998015867A1

WO1998015867A1 - Spectral analysis apparatus capable of functioning in several spectral regions of different wavelengths

Info

Publication number: WO1998015867A1
Application number: PCT/FR1997/001743
Authority: WO
Inventors: Edouard Da Silva; Michel Delhaye; Jacques Barbillat; Bernard Roussel
Original assignee: Dilor
Priority date: 1996-10-04
Filing date: 1997-10-02
Publication date: 1998-04-16
Also published as: FR2754341B1; FR2754341A1

Abstract

The excitation means comprise means for generating a plurality of monochromatic excitation beams (FEX1, FEX2) of different wavelengths, and transporting means for converging said plurality of excitation beams (FEX1, FEX2) on the same spatial region of the sample (ECH). The analysing arm comprises means for collecting the radiation (RD12) resulting from the illumination of said spatial region of the sample (ECH) by said plurality of excitation beams (FEX1, FEX2), and transferring said radiation (RD1, RD2, RD12) on to the spectral analysis means (ANA), means for detecting (DEC) and processing the spectra generated by said spatial region of the sample thus excited at different wavelengths.

Description

Spectral analysis apparatus capable of operating in several spectral ranges of different wavelengths

The present invention relates to a spectral analysis apparatus capable of operating in several spectral domains of different wavelengths in particular for characterizing the spatial distribution of at least one chemical species present in a sample.

It finds a general application in molecular spectrometry, in particular but not limited to Ra an spectrometry.

Numerous spectral analysis apparatuses are already known which operate either in a single spectral domain or in several spectral domains.

When the analysis requires measurements in several spectral domains, these measurements are not carried out, until now, on the same spatial domain of the sample, or they are but with different devices, or even at using switches or settings which complicate the implementation of the analysis.

The present invention overcomes these drawbacks.

Its aim is to offer researchers and / or analysts a spectral analysis device able to excite the same spatial domain of a sample, by several excitation beams of different wavelengths, in order to obtain at least several molecular spectra at different wavelengths generated by said same domain of the sample.

It relates to an apparatus for spectral analysis of a sample of the type comprising: - an excitation branch, comprising excitation means, to excite a sample;

- an analysis branch, comprising spectral analysis means, for spectrally analyzing the light scattered and / or reflected by the sample;

- detection means mounted at the outlet of the analysis branch; and

processing means for processing the signals detected by the detection means in order to deduce therefrom information on the spatial distribution of at least one chemical species present in said sample.

According to a general definition of the invention, the excitation means comprise generator means capable of generating a plurality of monochromatic excitation beams of different wavelengths, and transport means specific to said excitation beams on the same spatial domain of the sample;

the analysis branch comprises collection and transfer means suitable for collecting the radiation which results from the illumination of said spatial domain the sample by said plurality of excitation beams, and for transferring these radiation to the analysis means spectral;

the detection and processing means are suitable for detecting and processing the spectra generated by said spatial domain of the sample thus excited at different wavelengths.

The convergence of the plurality of monochromatic excitation beams on the same spatial domain of the sample is sequential or simultaneous.

Likewise, spectral detection at different wavelengths is sequential or simultaneous. Such an apparatus is thus able to record several molecular spectra generated by the same spatial domain (or spatial zone) of the sample at different wavelengths, which facilitates the implementation of the analysis and especially the processing of the information. by increasing the amount of data useful for the molecular characterization of the sample by processing methods such as chemometry.

It thus offers researchers and / or analysts the possibility of observing, simultaneously or sequentially, in combination or in correlation, spectra of different types (resonance, off resonance, absorption, fluorescence, or far from any fluorescence) in spectral domains. distinct, for example in the spectral range of the ultraviolet-visible and in the spectral range of the near infrared.

It also allows, for example, the discrimination of a fluorescence band by appropriate computer processing of the spectral data obtained simultaneously or sequentially at different wavelengths.

In practice, the means of transport are suitable for transporting the plurality of monochromatic excitation beams on a common optical axis.

According to a very important characteristic of the device according to the invention, the means of transport as well as the means of collection and transfer are achromatic in a very wide spectral range, going in particular from the visible to the infrared.

This achromaticity makes it possible to offer an analysis in several spectral domains ranging from the ultraviolet to the infrared, whereas usually the domains of correction of the chromatic aberrations of the lens systems are limited to a sparse spectral range. In practice, the means of transport as well as the means of collection and transfer are preferably at least partially arranged and combined on the common optical axis.

According to another aspect of the invention, the means of transport comprise first achromatic deflection means, arranged on the common optical axis and adapted to move, along a first line of a chosen length, and at a chosen frequency, the plurality of monochromatic excitation beams, on the sample to be analyzed, and said first deflection means are also capable of receiving and bringing back, on the common optical axis, the radiations resulting from said illumination by compensating in return for the first deflection, said resulting radiation comprising the spectra generated by the line of spatial domains of the sample thus scanned and illuminated at different wavelengths.

Very advantageously, the first deflection means are confocal, each first line analyzed of the sample being formed of points having rigorously confocal properties.

To obtain spectral confocal images of the sample thus scanned by the first deflection means, the collection and transfer means comprise second confocal achromatic deflection means, arranged on the common optical axis, and capable of spatially distributing on the entry slit of the spectral analysis means, along a second line of chosen length and at the same frequency as that of the first deflection means, said resulting radiation coming from the first deflection means, the first and second deflections being synchronous one with respect to the other to preserve the spatial information of said resulting radiations.

Very advantageously, the lengths of the first and second scanning lines are chosen relative to each other so as to achieve a chosen magnification of the spectral images of the sample on the detection means.

To obtain confocal spectral images of the sample, the collection and transfer means in practice comprise a diaphragm mounted on the common optical axis between the first and second deflection means and the diameter of which is adjustable on command to control the lateral dimension of the sample analyzed as well as the depth of field.

For particular applications such as in situ measurements, the device comprises at least one optical fiber capable of conveying the confocal information originating from the adjustable diaphragm to the input of the second deflection means.

According to another aspect of the invention, the apparatus further comprises confocal imaging means capable of at least partially detecting the energy of the radiations which result from the illumination of the sample thus scanned so as to have, if necessary simultaneously, at least one confocal image and several confocal spectral images relating to the same spatial domain of the sample thus scanned. As a variant, the confocal imaging means are capable of delivering several confocal images of the same spatial domain of the sample obtained at different wavelengths.

Such an apparatus thus makes it possible to have, if necessary, simultaneously, a confocal image and several spectral confocal images of the same spatial domain of the sample, with a view to comparing them, superimposing them or processing them. This information of various kinds thus made available makes the work of the users easier and better by offering them even more information useful for analyzing the sample.

It also allows you to compare, superimpose or process confocal images obtained on another device with the confocal and confocal spectral images obtained with the device object of the invention in the same place of the sample.

In practice, the confocal imaging means comprise an adjustable aperture diaphragm and at least one detector connected to the processing means.

According to another characteristic of the invention, the apparatus further comprises servo means capable of at least partially detecting the energy of the radiations which result from the illumination of the sample in order to servo the distance from the objective to the sample.

In practice, the servo means comprise an optical filter separating the radiation useful for the spectral characterization of the sample, an adjustable aperture diaphragm, and a signal detector connected to a servo unit suitable for servoing the distance from the objective to the sample using the confocal signal thus detected.

Preferably, the apparatus comprises a sample holder plate adjustable in Z in response to the servo means and / or an optical focusing element adjustable in Z in response to the servo means.

According to yet another important characteristic of the invention, the collection and transfer means comprise filtering means capable of separating the radiation useful for the spectral characterization of the sample for each excitation beam.

In practice, the filtering means comprise several filtering elements, mounted in series on the common axis, and each associated with the filtering of an excitation beam around a selected excitation wavelength, in one direction. optics of the common axis, on the one hand, and radiation backscattered around said selected excitation wavelength, in the other direction of the common axis, on the other hand, the bandwidths of the filter elements being compatible with each other.

Preferably, each filter element, mounted in series on the common axis, is a narrow band, with a steep attenuation slope and centered on the associated excitation wavelength and capable of injecting in a first direction ranging from generating means towards the sample, an excitation beam comprising radiation useful for illumination and for stopping the radiation useless for illumination situated outside the narrow band, as well as for transmitting simultaneously in a second direction opposite to the first , used back-scattered radiation useful for spectral analysis and located outside the narrow band and to reject back-scattered radiation useless for spectral analysis reflected or scattered around the associated excitation wavelength .

According to another aspect of the invention, the spectral analysis means comprise a plurality of dispersers, able to be coupled respectively to a plurality of ultichannel detection means each sensitive to at least one spectral domain.

Alternatively, the spectral analysis means comprise a single stigmatic, achromatic disperser capable of operating simultaneously or sequentially in a plurality of different orders to cover a plurality of distinct spatial domains.

Other characteristics and advantages of the invention will become apparent in the light of the detailed description below and of the drawings which may contribute to the definition of the invention, where appropriate, and in which:

- Figures 1 and 2 show schematically globally the means of the device according to the invention; - Figure 3 schematically illustrates in detail the constituent elements of the means of transport, as well as means of collection and transfer of the device 1 according to the invention;

- Figure 4 schematically shows in detail the first deflector means according to the invention;

- Figure 5 schematically shows in detail the input optics and the sample holder of the apparatus according to the invention;

- Figure 6 schematically shows in detail the confocal imaging means, as well as the means for controlling the development of the apparatus according to the invention;

- Figure 7 schematically shows in detail the second deflector means according to the invention;

- Figure 8 shows schematically a variant of the invention comprising an optical fiber connection of the adjustable diaphragm up to the inlet of the second deflector means according to the invention;

- Figure 9 schematically illustrates in detail the spectral analysis means comprising a first dispersive spectrometer capable of operating at a first wavelength and associated with a signal detector according to the invention;

- Figure 10 schematically illustrates in detail the spectral analysis means comprising a second dispersive spectrometer capable of operating at a second wavelength and associated with a signal detector according to the invention; and

- Figure 11 illustrates a variant of the apparatus in which the second deflection means are separated into two separate deflector elements according to the invention. To facilitate understanding of the description, the spectral analysis apparatus according to the invention comprises only two monochromatic excitation beams FEX1 and FEX2 of different wavelengths. Obviously, the invention also applies to n excitation beams, with n integer greater than or equal to 2.

In practice (FIG. 1), the excitation beams FEX1 and FEX2 are generated by one or two laser sources SL which are for example of the type with fixed wavelengths (solid laser, gas laser) or of the type with lengths d tunable wave (dye laser, diode laser). These excitation beams can be routed from their respective sources to their respective inputs 10 and 12 by single-mode or multimode optical fibers (not shown).

In an example presenting numerous interests in RAMAN spectrometry, the wavelength of the laser beam FEX1 is 532 n (visible) and that of the laser beam FEX2 is 1064 nm (near infrared). Obviously, the invention applies to monochromatic excitation beams having other wavelength values than 532 or 1064 nm. In this particular case, we can use the same spectrometer working at two different orders.

The monochromatic excitation beam FEX1 of a wavelength belonging for example to the visible-ultraviolet range is represented by arrows with thin solid lines. The FEX2 monochromatic excitation beam with a wavelength belonging for example to the near infrared range is represented by arrows with thin dashed lines.

The RD12 radiation resulting from the simultaneous illumination of the sample by the excitation beams FEX1 and FEX2 are represented by thick arrows with solid lines on the one hand and dashed lines on the other hand. The RDI radiations resulting from the illumination of the sample by the excitation beam FEX1 in the visible are represented by thick arrows with solid lines. Radiation RD2 resulting from the illumination of the sample by the excitation beam FEX2 in the near infrared are represented by thick arrows with dashed lines.

In FIG. 3, the excitation beam FEX1 is transported from the input 10, along the axis AX1 and the direction of propagation of the light, to a filter FT1, by optical elements comprising a mirror Ml, a spatial filter DF1 adjustable aperture (spatial filtering hole), two lenses L1 and L2 framing the filter DF1, and mirrors M2 and M3.

The filter FT1 is inclined relative to the normal to the common axis AXC, which will be described in more detail below, at an angle of a value of a few degrees. It is a narrow band, with a steep attenuation slope and centered on the wavelength 532 nm. It makes it possible to inject along the common axis AXC, towards the sample (that is to say here towards the input / output 14), an excitation beam FEX1 comprising radiation useful for illumination and d '' stop unnecessary radiation at illumination outside the narrow band. The FT1 filter is, for example, a reflection disperser (network not shown here) or a reflection and transmission disperser (holographic filter shown here in FIG. 3).

The FT1 filter also allows achromatic transmission along the common axis AXC, to the spectral analysis means ANA (FIGS. 9 and 10), backscattered radiation useful for spectral analysis and located outside the narrow band and the rejection of backscattered radiation unnecessary for spectral analysis reflected or scattered around 532 nm.

The excitation beam FEX2 is transported along the axis AX2 and the direction of propagation of the light from the input 12 to a filter FT2 by optical elements comprising a mirror M4, an adjustable spatial filter with opening DF2 (hole of spatial filtering), two lenses L3 and L4 framing the filter DF2, and a mirror M5. The FT2 filter is similar to the FT1 filter. It is inclined relative to the normal to the common axis AXC at an angle worth a few degrees. It is a narrow band, with a steep attenuation slope and centered on the wavelength 1064 nm. It makes it possible to inject along the common axis AXC, towards the sample (that is to say towards the input / output 14), an excitation beam FEX2 comprising radiation useful for illumination and to stop the unnecessary radiation at illumination located outside the narrow band. The FT2 filter is for example a reflector and transmission disperser (holographic filter).

The FT2 filter also allows achromatic transmission along the common axis AXC, to the spectral analysis means ANA (that is to say to the output 100), backscattered radiation useful for spectral analysis and located outside the narrow band and the rejection of backscattered radiation unnecessary for spectral analysis reflected or scattered around 1064 nm.

The filters FT1 and FT2 are here mounted in series on the common axis AXC. They are each associated with the filtering of an excitation beam around a selected excitation wavelength, in an optical direction of the common optical axis, on the one hand, and with the filtering of backscattered radiation. around said selected excitation wavelength, in the other direction of the common optical axis, on the other hand.

It should be noted that the passbands of the filters FT1 and FT2 are compatible with each other, that is to say that the filter FT1 which lets the beam FEX1 pass according to the passband of the filter FT1 also lets the beam FEX2 pass through FT2 filter bandwidth. The same is true for the radiation resulting from the illumination of the sample by the beams FEXl and FEX2. In other words, the filter FT1 takes account of the filtering provided by the filter FT2 and vice versa. In the case where one of the filters FT1 and FT2 has too much attenuation for the other radiation, a sequential system can be advantageously used.

A mirror M6 is interposed between the filters FT1 and FT2. It is used here to modify the direction of the common optical axis AXC. Obviously, not all of the mirrors are absolutely necessary here for transporting the excitation beams. They are there to improve the compactness of the device according to the invention. Obviously other light paths and other configurations of mirrors are possible. On the other hand, what is important here is the achromaticity conferred by these mirrors (spherical or aspherical) because it offers the possibility of analyzing sequentially or simultaneously in several spectral domains ranging from visible to infrared whereas usually the chromatic aberration correction domains of lens systems are limited to a small spectral range. It should be noted that the achromacity of the mirrors can be replaced by an achromacity of the optical elements obtained by appropriate software.

With reference to FIGS. 1 to 4, the beams FEXl and FΞX2 are then transported from the input / output 16 to an achromatic assembly comprising a deflector DL1, arranged on the common axis AXC and which can sweep along a line of chosen length LN1 , at a chosen frequency, the monochromatic excitation beams FEX1 and FEX2, on a line of spatial domains LS proportional to the line LN1 of the sample to be analyzed (with LS = K (LN1) and K coefficient of proportionality). The line LS (FIG. 2) consists of a row of confocal spatial domains mO, ml, m2, m3, belonging to the sample.

The beams FEX1 and FEX2 are transported from the input / output 16 to the input / output 18 here by a mirror M7, the deflector DL1, a mirror M8, and a mirror M9. The deflection generated by the deflector DL1 makes it possible here to obtain a line-by-line scan (in X) of the sample. This scanning in X is advantageously coupled to a sample holder 30 with micrometric displacement in Y. The scanning XY image can also be carried out optically for example by rotation on a perpendicular axis of the deflector assembly DLL

The deflector DL1 is able to bring back on the common optical axis AXC, the radiation RD12 resulting from the illumination of the sample thus scanned by compensating in return for the deflection.

With reference to FIG. 5, the apparatus comprises a sample holder 30 of the micrometric table XY type, capable of carrying the sample to be analyzed ECH. Most often, the sample is analyzed under a microscope objective 22 adjustable in Z. A TV camera can also receive the radiation RD12 via a separating plate 33 arranged on the common optical axis.

The table 30 is movable in micrometric movement X and Y. Control means 35 are suitable for also controlling the movement in Z of the objective 22 as will be described in more detail below or the movement in Z of the table micrometric.

Reference is again made to FIGS. 1 to 4. The radiations RD12 which result from the illumination of the sample by the excitation beams FEX1 and FEX2 are collected by the optical elements M9, M8, DL1, M7 to be filtered by the FT1 and FT2 filters. After filtering, these RD12 radiations are then transferred to spectral analysis means ANA by mirrors M10 and Mil, an adjustable aperture diaphragm DAl (confocal hole), and the output 100.

The diameter of the confocal hole DAl is adjustable on command to adjust the lateral dimension of the sample analyzed, as well as the depth of the field. This confocal hole DAl is placed between the first deflector means DL1 and the second deflector means DL2 which will be described in more detail below (FIG. 7), to confocal control all the spatial domains of the sample thus scanned by the first deflector means.

The apparatus is therefore advantageously confocal, that is to say that the spatial filters DF1 and DF2 are optically conjugated with the confocal hole DA1 whose opening is adjusted to obtain a chosen axial and lateral resolution. The confocal collection of RD12 spectra therefore makes it possible to produce optical sections of selected depth, which, with appropriate software, can be manipulated as three-dimensional representations of the sample.

It should be noted that the Z control of the position of the objective 22 or of the micrometric table is important for this application.

At the exit from the confocal hole DA1, it is possible to measure the energy of the radiations RD12 of a line LS of spatial domains of the sample, in order for example to determine inhomogeneities in the sample.

With reference to FIGS. 1 to 6, the common optical axis AXC here passes through the sample, the filters FT1 and FT2, the deflector DL1 and the confocal hole DAl.

With reference to FIG. 7, the radiations RD12 originating from the output 100 are routed to the output 102 through mirrors M12 and M13, a deflector DL2 and the input slot FE of the spectral analysis means. The role of the DL2 deflector here is to allow the spatial information contained in the RD12 radiation to be used by distributing this radiation along the entry slit of the spectral analysis means. The DL2 deflector assembly is achromatic. It distributes along a line LN2 on the entry slit FE of the spectral analysis means ANA, the radiations RD12 brought back on the common axis AXC by the deflector DLL This distribution or distribution takes place at the same frequency as that of the first means of deflection. In practice, the length of the second LN2 deflection is a constant.

The deflections DL1 and DL2 are advantageously synchronous with respect to each other to preserve the spatial information of the RD12 radiations. The lengths of the lines LN1 and LN2 are also chosen and controlled by electronic control (not shown) with respect to each other so as to achieve, where appropriate, a chosen magnification of the confocal spectral images on the detection means to two dimensions as will be described in more detail below (Figures 9 and 10).

With reference to FIG. 8, for certain applications such as in situ measurements or others, confocal control makes it possible to separate the device into two parts connected to each other by an optical fiber FO while retaining the characteristics and advantages of the device. The first part includes the module described with reference to Figure 3, while the second part includes the second deflector means described with reference to Figure 7. At the input of the optical fiber FO, a focusing device FOC focuses the radiation RD12 from the confocal hole DAl in the optical fiber FO. At the exit of the optical fiber, a collimation device COL is provided for collimating the radiation RD12 coming from the optical fiber FO on the mirror M12 via, if necessary, another confocal hole DA2 placed at the exit of the fiber and optically conjugated with the DAl confocal hole placed at the entrance of the fiber.

It should be noted that the optical fiber FO, transporting the confocal information coming from the confocal hole DAl, makes it possible to separate the device into two confocal branches, one of which, relating to the illumination, can be placed in a place chosen, and the other of which, relating to the analysis, can be placed in another place subject for example to environmental conditions different from those of the place where the illumination takes place. The transport of confocal information also makes the device easily modular, with the possibility of using in the illumination branch and in the analysis branch different interchangeable modules.

The information relating to the synchronization SYN of the deflectors DL1 and DL2 can be if necessary conveyed by the optical fiber FO or by any other means of information transport.

It should be noted that when the two deflector assemblies DL1 and DL2 are stopped, a conventional confocal point system is obtained. A confocal spectral image can then be obtained by micrometric displacement of the sample.

Referring to Figure 6, DCC confocal imaging means are provided in a location of the light path where the radiation useful for the spectral characterization of the sample is accessible. For example, these confocal imaging means are arranged between the input / output 14 and the input / output 16 described with reference to FIGS. 3 and 4.

A separating plate 19 disposed on the common optical axis AXC takes along the axis 17 a portion of the radiation energy RD12. A lens 21 focuses the sampled beam PRD12 through a diaphragm DF3 with adjustable and adjustable opening. A detector 39 of photodiode type sensitive for example to a given wavelength receives the radiations coming from the diaphragm DF3. The detector 39 is connected to the processing means to construct at least one confocal image of the sample analyzed at a given wavelength. The detector can be divided into two sub-detectors, each sensitive to a given wavelength, which makes it possible to obtain several confocal images at different wavelengths. Advantageously, means for controlling the focusing of the apparatus use in part the removal of energy from RD12 radiation to control the focusing of the apparatus.

In practice, a separating plate 41 is placed on the light path between the lens 21 and the diaphragm DF3 to take a portion of the radiation energy RD12. A filter 43 separates the radiation useful for spectral characterization.

A detector 47 receives this radiation filtered through a diaphragm DF4 with adjustable opening. The detector 47 is connected to the servo means 37 described with reference to FIG. 5. The information coming from the detector 47 makes it possible to control the position of the objective of the microscope relative to the sample.

The lateral position of the hole DF4 is calibrated and can be adjustable in the direction of the axis AX3 as a function of the chosen penetration (in depth) of the sample placed under the objective 22 of the microscope.

With reference to FIG. 9, the spectral analysis means ANA comprise a first dispersive spectrometer RI coupled to a multichannel detector DEC1.

A dichroic type BS separating plate receives the RD12 radiations coming from the FE entry slit and separates them into two radiation beams RDI and RD2 according to their wavelengths. Here, the RDI radiations are those belonging to the visible domain, and the RD2 radiations are those belonging to the infrared domain. Obviously, the separation of radiation can be carried out in another distribution and by other means.

The RDI radiations are routed to the multichannel detector DEC1 sensitive here in the example chosen at the wavelengths belonging to the visible range. The spectrum m'1 displayed on the detector DECl (FIG. 2) corresponds to the spectrum of the spatial domain of the sample ml generated by the excitation beam FEX1.

For example, the DECl detector is a two-dimensional CCD detector comprising a 1024 × 296 pixel mosaic, cooled by the Peltier effect or with liquid nitrogen. For example, the number PI (figure 2) of pixels per column makes it possible to determine the spatial resolution of the detector and the number pi of pixels per line makes it possible to determine the spectral resolution of the detector. The magnification factor of the spectral images is a function of the length LN1 when LN2 is constant. It is also equal to the ratio between the number P of pixels per column and the length LS.

The light path of the RDI radiation between the separating plate BS and the input 110 of the DECl detector is effected by optical elements mounted in series and comprising mirrors M20 and M21, a collimator CI, a dispersive network RI and a collimator C2.

The optical elements M20, M21, Cl, Ri, and C2 are arranged optically so that the spectrometry is astigmatic, achromatic, and in a flat field in the chosen region.

With reference to FIG. 10, the radiation RD2 is routed to the multichannel detector DEC2 sensitive here to the wavelengths belonging to the infrared domain.

For example, the DEC2 detector is a multi-channel germanium detector, cooled with liquid nitrogen, or a multi-channel detector based on gallium arsenide, cooled by the Peltier effect or with liquid nitrogen.

The spectrum m "l displayed on the detector DEC2 (FIG. 2) corresponds to the spectrum of the confocal spatial domain ml of the sample generated by the excitation beam FEX2. The light path of the radiation RD2 between the separating plate BS and the input 120 of the detector DEC2 is effected by optical elements mounted in series and comprising a collimator C3, a mirror M30, a dispersive network R2 and a collimator C4.

The optical elements C3, M30, R2, and C4 are arranged optically so that the spectrometry is astigmatic, achromatic, and in flat field in the chosen region.

It should be noted that it is not necessary for the spectral analysis means to comprise two separate dispersive networks in order to implement the invention. Indeed, the invention can also be implemented with a single dispersive network having several different orders, which makes it possible to cover several spectral domains, with for example each order of the network associated with a spectral domain.

The invention can also use a single network associated with several multichannel detectors placed at different angles depending on the wavelengths chosen.

It can also use other dispersive systems.

Likewise, it is not necessary for the detection means to comprise two separate detectors in order to implement the invention. Indeed, the invention can also be implemented with a single detector on the condition that it validly covers an appropriate spectral range.

Furthermore, the radiation resulting from external measurement heads (in situ) can be routed to the spectral analysis means, using optical fibers optimized according to the wavelength, ie an optical fiber for RDI radiation in the visible, and another optical fiber for RD2 radiation in the infrared. The interposition of RDI and RD2 radiation thus obtained from optical fibers can be carried out using retractable mirrors.

As a variant (FIG. 11), it is possible to implement the invention with second deflector means separated into two separate deflector elements DL21 and DL22. Under these conditions, the RD12 radiations coming from the DA1 confocal hole are directly separated into RDI radiations and RD2 radiations by a dichroic blade LD. The RDI radiation is distributed spatially by a first deflector element DL21 on the input FE1 of a first disperser SP1 while the radiation RD2 is spatially distributed by a second deflector element DL22 on the input FE2 of a second disperser SP2. This variant makes it possible to use two dispersers SP1 and SP2 of different characteristics and / or multi-channel detectors of different dimensions. The dispersers SP1 and SP2 can be spectrometers, adjustable or fixed interference systems, controlled crystals or any device allowing spectral information to be separated spectrally. SYN synchronization signals are used here to synchronize the deflections of the deflector elements DL21 and DL22 with the deflection DLL

Claims

1. Apparatus for spectral analysis of a sample of the type comprising:

- an excitation branch, comprising excitation means for exciting a sample;

- an analysis branch, comprising spectral analysis means (ANA) for spectrally analyzing the light scattered and / or reflected by the sample;

- detection means (DEC) mounted at the output of the analysis branch; and

- processing means for processing the signals detected by the detection means (DEC) in order to obtain information on the spatial distribution of at least one chemical species present in the sample;

characterized in that the excitation means comprise generating means capable of generating a plurality of monochromatic excitation beams (FEXl, FEX2) of different wavelengths belonging to a very wide spectral range going from the ultraviolet to infrared, and means of transport capable of converging said plurality of monochromatic excitation beams (FEX1, FEX2) on the same spatial domain of the sample (ECH);

in that the analysis branch comprises means of collection and transfer suitable for collecting the radiation (RD12) which result from the illumination of said spatial domain of the sample (ECH) by said plurality of monochromatic excitation beams ( FEX1, FEX2), and to transfer said radiation (RDI, RD2, RD12) to the spectral analysis means (ANA);

in that the means of transport as well as the means of collection and transfer are achromatic in a very wide spectral range, from ultraviolet to infrared; and

in that the detection (DEC) and processing means are suitable for detecting and processing the spectra generated by said spatial domain of the sample thus excited at different wavelengths.

2. Apparatus according to claim 1, characterized in that the transport means are capable of making the plurality of monochromatic excitation beams converge sequentially on the same spatial domain of the sample.

3. Apparatus according to claim 1, characterized in that the transport means are capable of making the plurality of monochromatic excitation beams converge simultaneously on the same spatial domain of the sample.

4. Apparatus according to claim 1, characterized in that the spectral detection at different wavelengths is simultaneous or sequential.

5. Apparatus according to claim 2 or claim 3, characterized in that the transport means are adapted to transport the plurality of monochromatic excitation beams on a common optical axis (AXC).

6. Apparatus according to claim 5, characterized in that the means of transport and the means of collection and transfer are at least partially arranged and coincident on the commum optical axis (AXC).

7. Apparatus according to claim 1 and claim 5, characterized in that the transport means comprise first achromatic deflection means (DLl) arranged on the common optical axis and suitable for moving, along a first line of chosen length, and at a chosen frequency, the plurality of monochromatic excitation beams (FEX1, FEX2), on the sample to be analyzed (ECH), and in that said first deflection means (DLl) are adapted to receive and bring back onto the common optical axis (AXC) the radiation (RD12) resulting from said illumination by compensating in return for the first deflection, said resulting radiation (RD12) comprising the spectra generated by the line of spatial domains of the sample thus scanned and illuminated at different wavelengths.

8. Apparatus according to claim 7, characterized in that the first deflector means (DLl) are confocal, each first analyzed line of the sample being formed of points having confocal properties.

9. Apparatus according to claims 6 and 7, characterized in that the collection and transfer means comprise second deflection means (DL2) achromatic, confocal, arranged on the common optical axis (AXC), and suitable for spatially distributing , along a second line of chosen length, and at the same frequency as that of the first deflector means (DLl), on the input slit (FE) of the spectral analysis means (ANA), the radiation (RD12) coming from the first deflection means (DLl), the first and second deflections being synchronous to preserve the spatial information of the radiations (RD12) coming from the first deflection means.

10. Apparatus according to claims 7 to 9, characterized in that the length of the first and second scanning lines are chosen relative to each other so as to achieve a chosen magnification of the spectral images of the sample on the detection means (DECl, DEC2).

11. Apparatus according to claims 8 and 9, characterized in that the collection and transfer means comprise a diaphragm (DAl) mounted on the common optical axis (AXC) between the first and second deflection means and whose diameter is adjustable on command to adjust the lateral dimension of the analyzed sample as well as the depth of field in order to make the spectra or images confocal spectral of the spatial domain or domains of the sample thus analyzed.

12. Apparatus according to claim 11, characterized in that it comprises at least one optical fiber capable of conveying the confocal information coming from the adjustable diaphragm

(DAl) until the entry of the second deflection means (DL2).

13. Apparatus according to claim 9, characterized in that the second deflection means (DL2) are separated into two separate deflector elements (DL21 and DL22), the radiation (RD12) from the adjustable diaphragm (DAl) being directly separated into first radiations (RDI) and second radiations (RD2) distinct according to their wavelength, the first deflector element (DL21) being adapted to spatially distribute the first radiations (RDI) on the input (FE1) of a first disperser (SPl), while the second deflector element (DL22) being adapted to spatially distribute the second radiation (RD2) on the input (FE2) of a second disperser (SP2).

14. Apparatus according to claims 7 to 11, characterized in that it further comprises confocal imaging means (DCC) capable of at least partially detecting the energy of the radiations (RD12) which result from the illumination of the sample thus scanned (ECH) to have at least one confocal image and several confocal spectral images relating to the same spatial domain of the sample thus scanned.

15. Apparatus according to claim 14, characterized in that the confocal imaging means are capable of delivering several confocal images of the same spatial domain of the sample obtained at different wavelengths.

16. Apparatus according to claim 14 or claim 15, characterized in that the confocal imaging means (DCC) comprise an adjustable aperture diaphragm (DF3) and at least one detector (39) connected to the processing means. 17. Apparatus according to claim 1, characterized in that it further comprises control means suitable for at least partially detecting the energy of the radiations which result from the illumination of the sample (ECH) in order to control the distance from lens to sample.

18. Apparatus according to claim 17, characterized in that the control means comprise an optical filter (43) separating the radiation useful for the spectral characterization of the sample, an adjustable aperture diaphragm (DF4), and a detector signal (47) connected to a servo unit (37) adapted to servo the distance from the objective to the sample using the confocal signal thus detected.

19. Apparatus according to claim 18, characterized in that it comprises a sample-holder plate (30) adjustable in Z in response to the servo means and / or an optical focusing element (22) adjustable in Z in response to means of enslavement.

20. Apparatus according to claim 1, characterized in that the collection and transfer means comprise filtering means (FT1, FT2) suitable for separating the radiation useful for the spectral characterization of the sample for each excitation beam ( FEXl, FEX2).

21. Apparatus according to claim 20, characterized in that the filtering means comprise several filtering elements (FTl, FT2), mounted in series on the common axis (AXC), and each associated with the filtering of a beam of monochromatic excitation (FEXl or FEX2) around a selected excitation wavelength, in an optical direction of the common axis (AXC), on the one hand, and backscattered radiations around said length of selected excitation wave, in the other direction of the common axis (AXC), on the other hand, the passbands of the filter elements (FT1 and FT2) being compatible with each other.

Claims

22. Apparatus according to claim 21, characterized in that each filter element (FT1, FT2), mounted in series on the common axis, is a narrow band, with a steep attenuation slope and centered on the wavelength associated excitation and capable of injecting in a first direction from the generator means towards the sample, a monochromatic excitation beam comprising radiation useful for illumination and in stopping the radiation useless for illumination located outside the band narrow, as well as to transmit simultaneously in a second direction opposite to the first, the backscattered radiations useful for the spectral analysis and located outside the narrow band and to reject the backscattered radiations useless for the spectral analysis reflected or scattered around the associated excitation wavelength.

23. Apparatus according to any one of the preceding claims, characterized in that the spectral analysis means (ANA) comprise a plurality of dispersers (RI, R2), each capable of being coupled respectively to a plurality of multichannel detection means ( DECl, DEC2) each sensitive to at least one spectral domain.

24. Apparatus according to one of claims 1 to 23, characterized in that the spectral analysis means (ANA) comprise a single stigmatic, achromatic disperser and working in a plurality of different orders to cover a plurality of domains distinct spectral.