MICROSCOPE-SONDE RAMAN MINIATURE

Abstract

TITLE: MINIATURE RAMAN PROBE MICROSCOPE The miniature Raman probe microscope (10) comprises, a) mounted on a housing (11): - a monochromatic light input collimator (13), - a monochromatic light output collimator (14), the optical axis (44) of which crosses the monochromatic light input axis, - an optical tube (16) of an electronic camera (17), - a visible light input collimator (12), the optical axis (42) of which crosses the optical axis of the optical tube, - an objective (15); and b) inside the housing:- a dichroic mirror (19) at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the monochromatic light output collimator,- a partially reflecting mirror (18) at the intersection of the optical axis of the optical tube and the optical axis of the visible light input collimator, and- an optical system (20, 21) at the entrance of the objective. Figure for abstract: Figure 1

Description

Title of the invention: MINIATURE RAMAN PROBE MICROSCOPE Technical field of the invention

[0001] The present invention relates to a miniature Raman probe microscope. It applies, in particular, to Raman spectroscopy. State of the art

[0002] The Raman microscope is a laser-based microscopic device used to perform Raman spectroscopy. Raman spectroscopy (or Raman spectrometry) and Raman microspectroscopy are non-destructive methods for observing and characterizing the molecular composition and external structure of a material, which exploits the physical phenomenon whereby a medium slightly modifies the frequency of the light circulating in it. This frequency shift, called the "Raman effect", corresponds to an exchange of energy between the light beam and the medium, and provides information on the substrate itself. Raman spectroscopy involves sending monochromatic light onto the sample and analyzing the scattered light. The information obtained by measuring and analyzing this shift makes it possible to trace certain properties of the medium, through spectroscopy.

[0003] Coherent Raman scattering does not use an observation of spontaneously scattered light during molecular collisions, but the coherent amplification of a second ray of different frequency and temporally incoherent from the exciting ray.

[0004] This technique is complementary to infrared spectroscopy. Both allow the study of the vibrational modes of a molecule, but the selection rules for the two spectroscopies may be different depending on the molecular symmetry. For molecules with a center of symmetry, no vibrational mode is observable at the same time in both spectroscopies. Some modes are active in Raman only and others in infrared only. For example, carbon dioxide, a symmetrical linear molecule, has a single vibrational band observed in Raman at 1388 crm1 which corresponds to the symmetric (or in-phase) stretching of the two bonds, and two vibrational bands in infrared at 2349 cm 1 and 667 crm1 which correspond respectively to the antisymmetric (or out-of-phase) stretching and the deformation of the bond angle.

[0005] Non-destructive spectroscopy allows the molecular composition and external structure of a material to be characterized. A beam of monochromatic light is sent onto the sample to be studied and the scattered light is analyzed after being collected by another lens and sent into a monochromator allowing measure its intensity using a detector (single-channel photomultiplier or CPM type, multi-channel CCD type).

[0006] When the electric field of a laser excitation interacts with the medium under study, there is an energy transfer from the field to the molecule and a dipole moment P is induced, depending on the polarizability, the vibration amplitude of the field and the frequency of the laser. If we consider small nuclear displacements, it is possible to develop the polarizability in Taylor series around the equilibrium position and we can thus redefine the dipole moment with a first term which represents the Rayleigh scattering (the dipole oscillates at the same frequency as the laser) while a second and a third terms represent the anti-Stokes and Stokes Raman scattering when there is respectively absorption and emission of a phonon.

[0007] Several diffusion geometries are possible. The diffused light is generally collected either at 180° or at 90°. The polarization of the incident and diffused beams can also be varied.

[0008] Raman microspectroscopy or micro-Raman is a microscopy measurement technique: by focusing the laser beam on a small part of the medium, the properties of this medium can be probed over a volume of a few pm3, for example used to analyze the formation and evolution of microcracks in the nuclear field.

[0009] However, the Raman microscopes known to date are large, so that they cannot be incorporated inside complex experimental devices or in hazardous environments, such as for example in a biological glove box. Presentation of the invention

[0010] In the microscope which is the subject of the invention, two different instruments are combined:

[0011] a high-quality, high-performance optical microscope comprising a digital camera and

[0012] a Raman probe capable of collecting light scattered by the Raman effect while blocking the exciting and very intense light from a laser source.

[0013] The operator has the option of using the device in Raman mode (collection of the Raman signal) or in optical microscope mode to be able to select the precise part to be analyzed using the video display on a digital screen. It is thus possible to select and analyze parts of samples whose dimensions are of the order of a few tens of microns. Brief description of the figures

[0014] Other advantages, aims and particular characteristics of the invention will emerge from the following non-limiting description of at least one particular embodiment of the device and the substation which are the subject of the present invention, with reference to the drawings. annexed, in which:

[0015] [Fig. 1] schematically represents a first particular embodiment of a Raman probe microscope which is the subject of the invention, comprising three collimators, a beam splitter cube, a dichroic mirror and a movable mirror,

[0016] [Fig.2] represents the optical path when the probe microscope illustrated in [Fig.l] is in the eyepiece viewing configuration,

[0017] [Fig.3] represents the optical path when the probe microscope illustrated in [Fig.l] is in “Raman” configuration,

[0018] [Fig.4] represents the optical path in a second embodiment of a Raman probe microscope object of the invention incorporating three collimators, two beam splitter cubes and a dichroic mirror,

[0019] [Fig.5] represents the optical path in a third embodiment of a Raman probe microscope which is the subject of the invention incorporating three collimators, a double beam-splitting rectangular parallelepiped and a dichroic mirror,

[0020] [Fig.6] represents the optical path in a fourth embodiment of a Raman probe microscope object of the invention incorporating two collimators, a beam splitter cube, a dichroic mirror and a mirror,

[0021] [Fig.7] represents a fifth embodiment of a Raman probe microscope which is the subject of the invention,

[0022] [Fig.8] represents a sixth embodiment of a Raman probe microscope which is the subject of the invention,

[0023] [Fig.9] represents a seventh embodiment of a Raman probe microscope which is the subject of the invention,

[0024] [Fig. 10] represents an eighth embodiment of a Raman probe microscope which is the subject of the invention,

[0025] [Fig. 11] shows, in section, a mirror moving mechanism of the first, fifth, sixth and seventh embodiments, and

[0026] [Fig. 12] represents, in section and schematically, a part of a ninth embodiment of the Raman probe microscope which is the subject of the invention. Description of the embodiments

[0027] The present description is given without limitation, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous manner.

[0028] It should be noted from now on that the figures are not to scale.

[0029] As understood from reading this description, various concepts inventive methods may be implemented by one or more methods or devices described below, several examples of which are provided herein. The actions or steps performed in carrying out the method or device may be ordered in any suitable manner. Accordingly, it is possible to construct embodiments in which the actions or steps are performed in a different order than that illustrated, which may include performing certain acts simultaneously, even if they are shown as sequential acts in the illustrated embodiments.

[0030] The expression "and / or", as used herein and in the claims, is to be understood to mean "either or both" of the elements so conjoined, i.e., elements which are present conjunctively in some cases and disjunctively in other cases. Multiple elements listed with "and / or" are to be interpreted in the same way, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present, other than the elements specifically identified by the "and / or" clause, whether or not they are related to these specifically identified elements.Thus, by way of non-limiting example, a reference to "A and / or B", when used in conjunction with open language such as "comprising" may refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0031] As used herein in the description and claims, "or" is to be understood inclusively.

[0032] As used in this specification and in the claims, the expression "at least one", with reference to a list of one or more elements, is to be understood to mean at least one element selected from one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than the specifically identified elements in the list of elements to which the expression "at least one" refers, whether or not related to those specifically identified elements.Thus, by way of non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or, equivalently, "at least one of A and / or B") may refer, in one embodiment, to at least one, optionally including more than one, A, without B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, without A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, . possibly comprising more than one, B (and possibly comprising other elements); etc.

[0033] In the claims, as well as in the description below, all transitional expressions such as "comprising", "including", "carrying", "having", "containing", "involving", "holding", "composed of", and the like, are to be understood as being open, i.e., as meaning including but not limited to. Only the transitional expressions "consisting of" and "consisting essentially of" are to be understood as closed or semi-closed transitional expressions, respectively.

[0034] The first particular embodiment of a Raman probe microscope 10 which is the subject of the invention, illustrated in figures 1 to 3, comprises, mounted on a light-tight housing 11, three collimators 12, 13 and 14 respectively carrying mechanical adapters 22, 23 and 24, of optical fibers, an objective 15 and an optical tube 16 connected moreover to an electronic camera 17.

[0035] The collimators 12 and 13 have parallel optical axes 42 and 43. The objective 15 has an optical axis 45. In the first embodiment, the collimator 24 and the objective 15 have the same optical axis 44 and 45, in the same plane as the optical axes 42 and 43 and perpendicular to these optical axes 42 and 43. The camera 17 and the optical tube 16 have an optical axis 46 in the same plane as the optical axes 42 and 43 and perpendicular to these optical axes 42 and 43.

[0036] Inside the housing 11, there are, at the intersection of the optical axes 42 and 46, a beam splitter cube 18, at the intersection of the optical axes 43 and 44, the semi-reflecting surface of a dichroic mirror 19 and a mirror 20 movable between a first position (on the left in [Fig.l]) where its reflecting surface is at the intersection of the optical axes 42 and 44 and a second intermediate position between the first position and the beam splitter cube 18, in which it does not reflect the light leaving the objective 15. The arrow 21 represents the amplitude of the movement that can be carried out by the movable mirror 20. All the reflecting surfaces are arranged in a plane perpendicular to the plane comprising the optical axes 42, 43, 44, 45 and 46 and at 45° to these optical axes.

[0037] The collimators 12, 13 and 14 comprise converging lenses, respectively 26, 27 and 29, for example plano-convex lenses, centered on their optical axes 42, 43 and 44.

[0038] The collimator 13 comprises, on its optical axis 43, a bandpass filter 35, which only lets the wavelength of the laser pass and “cleans” the laser light. Indeed, if the laser is not “clean” (single mode), there are parasitic wavelengths close to the wavelength of the laser which add noise to the signal.

[0039] The collimator 14 comprises a high-pass filter 36, which only allows the wavelengths higher than that of the laser. The intense light of the laser is thus filtered and the optical fiber 44 collects only the light scattered by the Raman effect.

[0040] The dimensions of the housing 11 are, for example, L = 90 mm and H1 = 75 mm, the collimators 12, 13 and 14 protrude from the housing by a distance of H3 = 35 mm and the optical tube 16 protrudes from the housing 11 by a height H2 = 65 mm.

[0041] Concerning the mechanism setting the movable mirror 20 in motion, this mirror 20 is placed on a carriage which slides on four fixed rods made of stainless metal parallel to the optical axis 42. A rod fixed to the carriage, outside the rectangular parallelepiped defined by the fixed rods, allows it to be moved manually from one position to another.

[0042] In the configuration illustrated in [Fig. 2], the movable mirror 20 is in its position on the intersection of the optical axes 42 and 44. The mechanical adapter 22 connects an optical fiber 32 to the collimator 12. The optical fiber 32 carries light in the sensitivity spectrum of the camera 17, for example white light. The useful path of the light coming from the optical fiber 32 passes through the beam splitter cube 18, is reflected on the movable mirror 20, passes through the objective 15 and reaches the sample 25. The light emitted or reflected by the sample 25 passes through the objective 15, is reflected on the movable mirror 20 is reflected on the internal semi-reflecting surface of the beam splitter cube 18, passes through the optical tube 16 and reaches the electronic camera 17. In this configuration, the probe microscope 10 serves as a microscope.

[0043] In the configuration illustrated in [Fig. 3], the movable mirror 20 is in its position spaced from the optical axis 44. The mechanical adapter 23 connects an optical fiber 33 to the collimator 13. The optical fiber carries a laser beam. The mechanical adapter 24 connects an optical fiber 34 to the collimator 14. The optical fiber is, at its other end, connected to a spectrometer (not shown). The useful path of the light coming from the optical fiber 33 is reflected on the dichroic mirror 19, passes through the objective 15 and reaches the sample 25. The light emitted or reflected by the sample 25 passes through the objective 15, passes through the dichroic mirror 19 and the collimator 14 to enter the optical fiber 34.

[0044] The dichroic mirror 19 is chosen so as to correspond to the length of the Raman excitation laser carried by the optical fiber 33. For example, for an excitation laser emitting at the wavelength of 532 nm (green laser), the dichroic mirror 19 reflects the light from the laser (532 nm) and allows any higher wavelength to pass (in general, a few nanometers more, in this case. For example, a very high quality filter allows wavelengths greater than 538 nm to pass). Thus, the light from the laser is eliminated from the light coming from the sample 25 and only the light scattered by the Raman effect by the sample 25 is collected.

[0045] According to a second example, the dichroic mirror reflects the light from the laser emitting at the wavelength of 785 nm (red laser) and allows any wavelength higher wavelength (e.g. wavelength greater than 795 nm).

[0046] Note that monochromatic light may or may not have a wavelength in the visible range.

[0047] In this configuration of [Fig. 3], the probe microscope 10 serves as a Raman probe.

[0048] In summary, the miniature Raman probe microscope 10 comprises, mounted on a light-tight housing 11: - a monochromatic light input collimator 13, carrying a mechanical adapter 23 of a monochromatic light input optical fiber 33, this collimator 13 being configured to focus the light coming from said monochromatic light input optical fiber 33 along an optical axis 43, - a monochromatic light output collimator 14, carrying a mechanical adapter 23 of monochromatic light output optical fiber 34, this collimator 14 being configured to focus the light along an optical axis 44 onto said monochromatic light output optical fiber 34, the monochromatic light input optical axis 43 and the monochromatic light output optical axis 44 intersecting inside the housing, - an optical tube 16 having an optical axis 46 configured to support an electronic camera 17 sensitive in the visible spectrum, - a visible light input collimator 12, carrying a mechanical adapter 22 of a visible light input optical fiber 32, this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis 42, the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12 intersecting inside the housing, and - a 15 lens having a 45 optical axis.

[0049] The Raman probe microscope 10 also comprises, inside the housing 11: - a dichroic mirror 19 at the intersection of the optical axis 43 of the monochromatic light input collimator 13 and the optical axis 44 of the monochromatic light output collimator 14, - a partially reflecting mirror 18 at the intersection of the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12, and - an optical system 20, 21 at the entrance of the objective 15 to make the objective 15 receive monochromatic light coming from the dichroic mirror 19 or visible light coming from the partially reflecting mirror 18.

[0050] In this first embodiment, the optical system at the entrance of the objective 15 comprises a fully reflecting mirror 20 movable between a position on the optical path of the monochromatic light and a position outside the optical path of the monochromatic light.

[0051] Note that monochromatic light can have a wavelength in the visible domain, as in the examples given above.

[0052] In its second embodiment illustrated in [Fig.4], the Raman probe microscope 30 which is the subject of the invention comprises the same elements as in the Raman probe microscope 10, except that the mobile mirror 20 is replaced by a beam splitter cube 28 whose semi-reflecting surface is at the intersection of the optical axes 42 and 44.

[0053] The adapters 22, 23 and 24 connect the collimators 12, 13 and 14 to optical fibers 32, 33 and 34. When light enters the collimator 12 from the optical fiber 32, its useful part follows the optical path described with respect to [Fig. 2]. When light enters the collimator 13 from the optical fiber 33, its useful part follows the path described with respect to [Fig. 3].

[0054] Thus, the two light sources can be used simultaneously, for the adjustments of the area of the sample 25 to be observed: the white light from the collimator 12 illuminates and makes the sample 25 visible to the camera 17. The light from the collimator 12 makes it possible to see the part of the sample which will actually be irradiated by the laser, therefore, the part which will be analyzed by Raman. Once the observation area (in English "spot") is correctly positioned, the white light is switched off so that there is no interference with the Raman analysis.

[0055] Again, the miniature Raman probe microscope 30 comprises, mounted on a light-tight housing 11: - a monochromatic light input collimator 13, carrying a mechanical adapter 23 of a monochromatic light input optical fiber 33, this collimator 13 being configured to focus the light coming from said monochromatic light input optical fiber 33 along an optical axis 43, - a monochromatic light output collimator 14, carrying a mechanical adapter 23 of monochromatic light output optical fiber 34, this collimator 14 being configured to focus the light along an optical axis 44 onto said monochromatic light output optical fiber 34, the monochromatic light input optical axis 43 and the monochromatic light output optical axis 44 intersecting inside the housing, - an optical tube 16 having an optical axis 46 configured to support an electronic camera 17 sensitive in the visible spectrum, - a visible light input collimator 12, carrying a mechanical adapter 22 of a visible light input optical fiber 32, this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis 42, the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12 intersecting inside the housing, and - a 15 lens having a 45 optical axis.

[0056] The Raman probe microscope 20 also comprises, inside the housing 11: - a dichroic mirror 19 at the intersection of the optical axis 43 of the monochromatic light input collimator 13 and the optical axis 44 of the monochromatic light output collimator 14, - a partially reflecting mirror 18 at the intersection of the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12, and - an optical system 20, 21 at the entrance of the objective 15 to make the objective 15 receive monochromatic light coming from the dichroic mirror 19 or visible light coming from the partially reflecting mirror 18.

[0057] In this second embodiment, the optical system at the entrance of the objective 15 comprises a semi-reflecting mirror 28. In the example shown, this semi-reflecting mirror takes the form of a cube with light-splitting prisms.

[0058] In its third embodiment illustrated in [Fig.5], the Raman probe microscope 40 which is the subject of the invention comprises the same elements as in the Raman probe microscope 30, except that the beam splitter cubes 18 and 28 are replaced by a double beam splitter rectangular parallelepiped 38.

[0059] The advantage of using a double beam-splitting rectangular parallelepiped 38 instead of two beam-splitting cubes 18 and 28 is that, between the two surfaces of the obliques, there is no reflection phenomenon, or induced interference between the reflected beams which go back and forth between the two surfaces perpendicular to the optical axis 42 of the cubes 18 and 28.

[0060] The beam reflected inside the first 45° reflective surface of the double beam-splitting rectangular parallelepiped 38 (equivalent to the first cube 28) continues its optical path to the second 45° reflective surface (equivalent to the cube 18), without reflection or risk of interference.

[0061] Furthermore, with the double beam-splitting rectangular parallelepiped 38, the problem of aligning the cubes 18 and 28 does not arise.

[0062] The optical paths are identical to those described with respect to [Fig.4].

[0063] Again, the miniature Raman probe microscope 40 comprises, mounted on a light-tight housing 11: - a monochromatic light input collimator 13, carrying a mechanical adapter 23 of a monochromatic light input optical fiber 33, this collimator 13 being configured to focus the light coming from said monochromatic light input optical fiber 33 along an optical axis 43, - a monochromatic light output collimator 14, carrying a mechanical adapter 23 of monochromatic light output optical fiber 34, this collimator 14 being configured to focus the light along an optical axis 44 onto said monochromatic light output optical fiber 34, the optical axis 43 monochromatic light input and monochromatic light output optical axis 44 intersecting inside the housing, - an optical tube 16 having an optical axis 46 configured to support an electronic camera 17 sensitive in the visible spectrum, - a visible light input collimator 12, carrying a mechanical adapter 22 of a visible light input optical fiber 32, this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis 42, the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12 intersecting inside the housing, and - an objective 15 having an optical axis 45.

[0064] The Raman probe microscope 40 also comprises, inside the housing 11: - a dichroic mirror 19 at the intersection of the optical axis 43 of the monochromatic light input collimator 13 and the optical axis 44 of the monochromatic light output collimator 14, - a partially reflecting mirror 18 at the intersection of the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12, and - an optical system 20, 21 at the entrance of the objective 15 to make the objective 15 receive monochromatic light coming from the dichroic mirror 19 or visible light coming from the partially reflecting mirror 18.

[0065] In this third embodiment, the optical system at the entrance of the objective 15 comprises two semi-reflecting mirrors. In this embodiment, these two reflecting mirrors take the form of a double cube 38 with light-splitting prisms, merged in the rectangular parallelepiped 38 which is a double beam splitter.

[0066] In its fourth embodiment illustrated in [Fig.6], the Raman probe microscope 50 which is the subject of the invention comprises the same elements as in the Raman probe microscope 30, except that there is no collimator 12 and that the beam splitter cube 18 is replaced by a mirror 39. The light from the optical fiber 33 passes through the collimator 13, is reflected on the dichroic mirror 19, passes through the beam splitter cube 28 and the objective 15 to reach the sample 25. The light emitted or reflected by the sample 25 passes through the objective 15 before being separated into two parts by the beam splitter cube 28. A first part of this light passes through this cube 18 then the dichroic mirror 19, before reaching the collimator 14 then the optical fiber 34.A second part of this light is reflected on the semi-reflecting surface of the beam splitter cube 28 then on the mirror 39 and reaches the camera 17 via the optical tube 16.

[0067] [Fig.6] represents the optical path in a fourth embodiment of a Raman probe microscope which is the subject of the invention incorporating two collimators, a cube beam splitter, a dichroic mirror and a mirror. In this embodiment, there is no collimator 12 and the beam splitter cube 18 of the first embodiment is replaced by a mirror 39. The light scattered by the sample 25, resulting from the excitation of the laser, can thus be seen by the camera 17.

[0068] Again, the miniature Raman probe microscope 50 comprises, mounted on a light-tight housing 11: - a monochromatic light input collimator 13, carrying a mechanical adapter 23 of a monochromatic light input optical fiber 33, this collimator 13 being configured to focus the light coming from said monochromatic light input optical fiber 33 along an optical axis 43, - a monochromatic light output collimator 14, carrying a mechanical adapter 23 of monochromatic light output optical fiber 34, this collimator 14 being configured to focus the light along an optical axis 44 onto said monochromatic light output optical fiber 34, the monochromatic light input optical axis 43 and the monochromatic light output optical axis 44 intersecting inside the housing, - an optical tube 16 having an optical axis 46 configured to support an electronic camera 17 sensitive in the visible spectrum, - a visible light input collimator 12, carrying a mechanical adapter 22 of a visible light input optical fiber 32, this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis 42, the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12 intersecting inside the housing, and - a 15 lens having a 45 optical axis.

[0069] The Raman 50 probe microscope also includes, inside the housing 11: - a dichroic mirror 19 at the intersection of the optical axis 43 of the monochromatic light input collimator 13 and the optical axis 44 of the monochromatic light output collimator 14, - a partially reflecting mirror 18 at the intersection of the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12, and - an optical system 20, 21 at the entrance of the objective 15 to make the objective 15 receive monochromatic light coming from the dichroic mirror 19 or visible light coming from the partially reflecting mirror 18.

[0070] In this fourth embodiment, the visible light input collimator 12 and the monochromatic light input collimator 13 are combined, the monochromatic light being in the visible range.

[0071] Sets of mirrors, mobile, semi-reflecting or dichroic, easily configured for the person skilled in the art of optics, allow the col limators 12, 13 and 14, the optical tube 16 and the objective 15, according to the 120 possible combinations. Figures 8 and 9 give examples of such exchanges of positions. In addition, their positions on the different faces of the housing perpendicular to the plane comprising the optical axes 42, 43, 44, 45 and 46 can be modified. [Fig.7] gives an example of such a modification, applied in this case to the objective 15.

[0072] In the fifth embodiment of a Raman probe microscope 60 which is the subject of the invention illustrated in [Fig.7], the objective 15 and the optical axis 45 linked to it are on the axis 42 of the collimator 12. The mirror 62 is movable between a first position (at the bottom in [Fig.7]) where its reflecting surface is at the intersection of the optical axes 42 and 44 and a second intermediate position between the first position and the dichroic mirror 19, in which it does not reflect the light coming out of the objective 15.

[0073] The arrow 61 represents the amplitude of the movement that can be carried out by the movable mirror 62. All the reflecting surfaces are arranged in a plane perpendicular to the plane comprising the optical axes 42, 43, 44, 45 and 46 and at 45° to these optical axes.

[0074] Apart from the direction of movement of the movable mirror, the operation of the Raman probe microscope 60 is identical to that of the Raman probe microscope 10.

[0075] In the sixth embodiment of a Raman probe microscope 70 which is the subject of the invention illustrated in [Fig.8], with respect to the Raman probe microscope 10, the positions of the collimators 13 and 14 are interchanged. The operation of the Raman probe microscope 70 is identical to that of the Raman probe microscope 10.

[0076] In the seventh embodiment of a Raman probe microscope 80 which is the subject of the invention illustrated in [Fig.9], with respect to the Raman probe microscope 10, the positions of the collimator 12 and the optical tube 16 are interchanged. The operation of the Raman probe microscope 80 is identical to that of the Raman probe microscope 10.

[0077] In the eighth embodiment of a Raman probe microscope 90 which is the subject of the invention illustrated in [Fig. 10], with respect to the Raman probe microscope 10, the movable mirror 20 is replaced by a dichroic mirror 91. The dichroic mirror 91 separates the light having a wavelength around the wavelength of the monochromatic light transmitted by the monochromatic light input collimator 13, on the one hand, and the visible light of other wavelengths, on the other hand. In the configuration illustrated in [Fig. 10], the light having wavelengths around the monochromatic light, for example between the wavelength of the monochromatic light and 100 nm above this wavelength, is not reflected by the mirror 91 while the light of the other visible wavelengths is reflected.For example, for an excitation laser emitting at the wavelength of 532 nm (green laser), the dichroic mirror 91 allows any wavelength from 530 to 630 nm to pass.

[0078] Of course, in other embodiments, the part of the light spectrum reflected and the non-reflected part of the light spectrum are reversed, for example when collimators 12 (and semi-reflecting mirror 18) and 13 are interchanged. For example, dichroic mirror 91 reflects light in the range 785 nm (red laser) to 885 nm and allows other wavelengths of the visible spectrum to pass through.

[0079] The Raman microscope which is the subject of the invention is compact to such an extent that it can be incorporated into complex experiments or into dangerous environments such as, for example, in a biological glove box.

[0080] Again, the miniature Raman probe microscope 90 comprises, mounted on a light-tight housing 11: - a monochromatic light input collimator 13, carrying a mechanical adapter 23 of a monochromatic light input optical fiber 33, this collimator 13 being configured to focus the light coming from said monochromatic light input optical fiber 33 along an optical axis 43, - a monochromatic light output collimator 14, carrying a mechanical adapter 23 of monochromatic light output optical fiber 34, this collimator 14 being configured to focus the light along an optical axis 44 onto said monochromatic light output optical fiber 34, the monochromatic light input optical axis 43 and the monochromatic light output optical axis 44 intersecting inside the housing, - an optical tube 16 having an optical axis 46 configured to support an electronic camera 17 sensitive in the visible spectrum, - a visible light input collimator 12, carrying a mechanical adapter 22 of a visible light input optical fiber 32, this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis 42, the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12 intersecting inside the housing, and - a 15 lens having a 45 optical axis.

[0081] The Raman 90 probe microscope also includes, inside the housing 11: - a dichroic mirror 19 at the intersection of the optical axis 43 of the monochromatic light input collimator 13 and the optical axis 44 of the monochromatic light output collimator 14, - a partially reflecting mirror 18 at the intersection of the optical axis 46 of the optical tube 16 and the optical axis 42 of the visible light input collimator 12, and - an optical system 91 at the entrance of the objective 15 to make the objective 15 reach monochromatic light coming from the dichroic mirror 19 or visible light coming from the partially reflecting mirror 18.

[0082] In this eighth embodiment, the optical system at the entrance of the objective 15 comprises a dichroic mirror 91 separating the light having a wavelength around the wavelength of the light transmitted by the monochromatic light input collimator 13, on the one hand, and visible light of other wavelengths, on the other hand.

[0083] [Fig. 11] shows, in section, a mirror moving mechanism of the first, fifth, sixth and seventh embodiments,

[0084] This section is located in a plane parallel to the plane comprising the optical axes 42, 43, 44, 45 and 46 but offset outside the optical paths. However, to aid understanding of [Fig. 11], these axes 42 to 46 have been represented in broken lines.

[0085] The mechanism for moving the mirror 20, over the amplitude represented by the arrow 21, comprises a support 51 for the mirror 20 slidably mounted on four cylindrical slides 52. A pull 54 is, at one end, secured to the support 51 and, at the other of its ends, to a handle (here of spherical shape) outside the housing 11. An opening 55 in the housing 11 allows the passage and sliding of the pull 54. By actuating this pull 54, the reflecting surface of the mirror 20 is positioned on the intersection of the axes 42 and 45 or, on the contrary, the mirror 20 and the support 51 are moved away from the axis 45. The objective 15, the attachment 56 of which is seen in [Fig. 11], thus receives either the visible light coming from the collimator 12, or the monochromatic light coming from the collimator 13. For example, the fastener 56 is a threaded opening in the housing 11.

[0086] In the ninth embodiment illustrated in [Fig. 12], the Raman probe microscope 100 which is the subject of the invention comprises a fixed mirror 71 which is transparent along the optical axis 45. For this purpose, either the mirror 71 has an opening 72, or it is treated, for example chemically or by laser, to remove its reflective materials on a limited area of its reflective face. Outside of this non-reflecting area, the mirror 71 is fully reflective for all the wavelengths of light used in the Raman probe microscope 100.

[0087] In [Fig. 12], the cone 73 of light coming from the objective 15 is shown, of which only the attachment 56 is shown in [Fig.12], and reaching the entrance lens of the optical tube 16. This cone 73 is bent at each reflection of this light on a mirror. As can be understood from the view of this cone 73, the camera 17 mounted on the optical tube 16 receives all the light coming from the objective 15, with the exception of the light along the optical axis 45. This ninth embodiment ensures greater sensitivity, both, of the microscope and of the Raman probe, compared to the Raman probe microscopes 30, 40, 50 and 90 of the second, third, fourth and eighth embodiments, in which the double crossing of the semi-reflecting mirrors, 28, 38 and 91 divides the sensitivity of each of the combined instruments by four.

[0088] Of course, the technical characteristics of the different embodiments can be combined to form other embodiments of the microscope. miniature Raman probe object of the invention.

[0089] Furthermore, the dichroic mirror 19 can be removable without opening the housing 11, for example by means of a drawer system (not shown) carrying this dichroic mirror, this drawer being movable on slides (not shown) mounted inside the housing 11. The drawer can thus be replaced with the dichroic mirror 19 for other observations using the Raman effect.

[0090] Other characteristics of embodiments and variants of the Raman probe microscope which is the subject of the invention are given below.

[0091] In this device, there is the combination of two different instruments: a high-quality and high-performance optical microscope with a digital camera (instead of a standard eyepiece) and a Raman probe that can collect the light scattered by the Raman effect while blocking the exciting and very intense light of the laser. The operator has the option of using the device in Raman mode (collection of the Raman signal) or in optical microscope mode to be able to select the precise part to be analyzed using the video display on a digital screen. This allows the analysis of samples as small as a few tens of micrometers.

[0092] From an optical point of view, there is the superposition of two optical paths: one specific to the microscope, the other (excitation and diffusion) specific to the Raman phenomenon.

[0093] According to a variant of the first embodiment, the beam splitter cube is replaced by a beam splitter plate (in English “Plate beam Splitter”), or semi-reflecting mirror.

[0094] An advantage of the second, third, fourth and eighth embodiments 30, 40, 50 and 90 is that the white light and the laser can illuminate the sample 25 at the same time. Therefore, it is possible to simultaneously have the Raman signal of the targeted part of the sample and its visualization with the camera 17. Thus, a much more interactive adjustment is possible. Once the adjustments have been optimized, the white light source (optical fiber 32) is switched off and the measurements without stray light are carried out. Summary of the invention

[0095] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0096] To this end, according to a first aspect, the present invention aims at a miniature Raman probe microscope which comprises:

[0097] a) mounted on a light-tight housing: - a monochromatic light input collimator, carrying a mechanical adapter of a monochromatic light input optical fiber, this collimator being configured to focus the light coming from said input optical fiber monochromatic light along an optical axis, - a monochromatic light output collimator, carrying a monochromatic light output optical fiber mechanical adapter, this collimator being configured to focus light along an optical axis onto said monochromatic light output optical fiber, the monochromatic light input optical axis and the monochromatic light output optical axis intersecting

[0098] b) inside the housing, - an optical tube having an optical axis configured to support an electronic camera sensitive in the visible spectrum, - a visible light input collimator, carrying a mechanical adapter of a visible light input optical fiber, this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis, the optical axis of the optical tube and the optical axis of the visible light input collimator intersecting inside the housing, - a lens having an optical axis;

[0099] and, inside the case: - a dichroic mirror at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the monochromatic light output collimator, - a partially reflecting mirror at the intersection of the optical axis of the optical tube and the optical axis of the visible light input collimator, and - an optical system at the entrance of the objective to make monochromatic light coming from the dichroic mirror or visible light coming from the partially reflecting mirror reach the objective.

[0100] Thanks to these provisions, the miniature Raman probe microscope which is the subject of the invention integrates and combines two different instruments: - a high-quality, high-performance optical microscope with a digital camera and - a Raman probe capable of collecting light scattered by the Raman effect while blocking the exciting and very intense light from a laser source,

[0101] such that an operator can use the probe microscope in Raman mode or in optical microscope mode to select a specific part to be analyzed in Raman mode, using the display of the video signal from the camera on a digital screen.

[0102] In embodiments, the optical system at the entrance of the objective comprises a fully reflective mirror movable between a position on the optical path of the monochromatic light and a position outside the optical path of the monochromatic light or between a position on the optical path of the monochromatic light visible and a position outside the optical path of visible light.

[0103] Thanks to these arrangements, depending on the positions of the fully reflecting mirror, all the light coming from one of the light input collimators and all the light coming from the objective are either transmitted or reflected. The sensitivity of the Raman probe microscope is therefore maximum both in microscope mode and in Raman probe mode.

[0104] In embodiments, the optical system at the entrance of the lens comprises a semi-reflecting mirror.

[0105] Thanks to these provisions, problems of alignment of moving parts are avoided.

[0106] In embodiments, the optical system at the entrance of the objective comprises two semi-reflecting mirrors.

[0107] In embodiments, the optical system at the entrance of the objective comprises a double cube with light-splitting prisms.

[0108] In embodiments, the optical system at the entrance of the objective comprises a dichroic mirror separating light having a wavelength around the wavelength of the light transmitted by the monochromatic light input collimator, on the one hand, and visible light of other wavelengths, on the other hand.

[0109] With each of these arrangements, no moving parts are required for the optical tube and light output collimator to be on optical paths of light exiting the objective lens within the housing.

[0110] In embodiments, the visible light input collimator and the monochromatic light input collimator are the same, the monochromatic light being in the visible range.

[0111] In embodiments, the monochromatic light has a wavelength in the visible range.

[0112] In embodiments, the dichroic mirror at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the monochromatic light output collimator is removable without opening the housing.

[0113] In embodiments, the dichroic mirror at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the monochromatic light output collimator is carried by a movable drawer on slides mounted inside the housing.

[0114] Thanks to each of these arrangements, the Raman excitation wavelength can be modified with the change of the dichroic mirror, without opening the housing.

Claims

Claims

1. Miniature Raman probe microscope (10, 30, 40, 50, 60, 70, 80), characterized in that it comprises, mounted on a light-tight housing (11): - a monochromatic light input collimator (13), carrying a mechanical adapter (23) of a monochromatic light input optical fiber (33), this collimator being configured to focus the light coming from said monochromatic light input optical fiber along an optical axis (43), - a monochromatic light output collimator (14), carrying a mechanical adapter (23) of a monochromatic light output optical fiber (34), this collimator being configured to focus the light along an optical axis (44) onto said monochromatic light output optical fiber, the monochromatic light input optical axis and the monochromatic light output optical axis intersecting inside the housing, - an optical tube (16) having an optical axis (46) configured to support an electronic camera (17) sensitive in the visible spectrum, - a visible light input collimator (12), carrying a mechanical adapter (22) of a visible light input optical fiber (32), this collimator being configured to focus the light coming from said visible light input optical fiber along an optical axis (42), the optical axis of the optical tube and the optical axis of the visible light input collimator intersecting inside the housing, - an objective (15) having an optical axis (45); and, inside the case: - a dichroic mirror at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the monochromatic light output collimator, - a partially reflecting mirror at the intersection of the optical axis of the optical tube and the optical axis of the visible light input collimator, and - an optical system at the entrance of the objective to make monochromatic light coming from the dichroic mirror or visible light coming from the partially reflecting mirror reach the objective.

2. Miniature Raman probe microscope (10, 60, 70, 80) according to re- indication 1, wherein the optical system at the entrance of the objective (15) comprises a mirror (20, 62) integrally reflecting movable between a position on the optical path of the monochromatic light and a position outside the optical path of the monochromatic light or between a position on the optical path of the visible light and a position outside the optical path of the visible light.

3. A miniature Raman probe microscope (30, 40) according to claim 1, wherein the optical system at the entrance of the objective (15) comprises a semi-reflecting mirror (28, 38).

4. A miniature Raman probe microscope (30, 40) according to claim 3, wherein the optical system at the entrance to the objective (15) comprises two semi-reflecting mirrors (18, 28, 38).

5. A miniature Raman probe microscope (40) according to claim 4, wherein the optical system at the entrance to the objective (15) comprises a double cube with light-splitting prisms (38).

6. A miniature Raman probe microscope (90) according to claim 3, wherein the optical system at the entrance of the objective (15) comprises a dichroic mirror (91) separating light having a wavelength around the wavelength of the light transmitted by the monochromatic light input collimator (13), on the one hand, and visible light of other wavelengths, on the other hand.

7. A miniature Raman probe microscope (50) according to claim 1, wherein the visible light input collimator (12) and the monochromatic light input collimator (13) are the same, the monochromatic light being in the visible range.

8. A miniature Raman probe microscope (10, 30, 40, 50, 60, 70, 80, 90) according to one of claims 1 to 6, wherein the monochromatic light has a wavelength in the visible range.

9. Miniature Raman probe microscope (10, 30, 40, 50, 70, 80, 90) according to one of claims 1 to 8, wherein the dichroic mirror (19) at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the monochromatic light output collimator, is removable without opening the housing (11).

10. A miniature Raman probe microscope (10, 30, 40, 50, 60, 70, 80, 90) according to claim 9, wherein the dichroic mirror (19) at the intersection of the optical axis of the monochromatic light input collimator and the optical axis of the mo- nochromatic, is carried by a movable drawer on slides mounted inside the housing (11).

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