Optical Concentration / Collection Systems

Abstract

The present invention relates to an optical collection / collection system, comprising: - a first light shaping part (10) including an exit surface (10) adapted to provide a circularized primary light beam; - a second optical concentrator / collector (20) including a conical upper central reflective surface (21) and a conical lower central reflective surface (24); a third optical return section (30) including a reflective surface (31), the reflective surface (31) being disposed along the main optical axis (Δ) between the exit surface (12) and the upper central reflective surface (21), and having a lateral dimension smaller than a lateral dimension of the annularized primary light beam provided by the first optical section (10); Includes:

Description

[Technical Field]

[0001] The field of the invention is that of optical light gathering / collection systems, which can be used in particular in connection with confocal microscopy and spectroscopy, for example of the fluorescence or Raman type. [Background technology]

[0002] In the field of confocal microscopy and spectroscopy, an optical system can include an optical emitter adapted to emit a so-called primary or excitation beam, an optical system adapted to focus the primary beam on the sample to be analyzed, on the one hand, and to collect so-called secondary beams resulting from the excitation of the sample by the primary beam, on the other hand, and an optical detection system intended to receive and detect the secondary beam. In this case, the optical system is arranged between the optical emitter and the optical detector, on the one hand, and between the optical emitter and the sample to be analyzed, on the other hand. Ideally, the entire optical system should be able to operate at the diffraction limit, where the size of the primary and secondary beam spots is reduced along with their wavelengths at the sample. However, the two primary and secondary beams may be at different frequencies, and the optical system is optimized for these two frequencies. In this case, this can be achieved by separating the optical paths using dichroic filters.

[0003] These optical collection / gathering functions are ensured by the objectives of some confocal microscopes or spectrometers. They can belong to the class of refractive optical systems, i.e. optical systems formed exclusively by refractive (i.e. refractive) optical elements, or to the class of catadioptric optical systems, i.e. optical systems formed by a combination of refractive and reflective optical elements.

[0004] To address achromatism, they can include multiple lenses selected and arranged to correct chromatic and spherical aberrations as much as possible. However, to maximize collection and detection of light rays of interest, it is generally desirable to have a compact optical system with a suitable working distance (the distance between the optical system's output and focal plane), but this multiple lenses results in a large size for a given numerical aperture. In addition, each of these lenses absorbs or slightly reflects the light passing through it, thereby reducing transmission efficiency.

[0005] Furthermore, there are optical systems of the reflective type, i.e. formed only by reflective optical elements that are essentially achromatic. However, depending on the solution chosen, there may be more or less significant dark areas along the optical axis of the optical system, which may reduce the performance of the optical system, such as the collection ratio of secondary rays (the ratio between the number of collected photons of the secondary rays and the number of emitted photons of the secondary rays). This reduction in performance and detection isotropy may make the system unsuitable for some applications due to this loss of information in the center of the field of view.

[0006] Document WO 2010 / 141092 A2 describes a reflective axicon optical system adapted to focus light rays. This optical system is formed by several concentric conical reflective surfaces. However, while the optical system can be used to focus primary light rays and collect secondary light rays, this optical system, designed for non-confocal optical microscopy, does not allow for the optical paths of these light rays to be distinguished. In this case, the optical system must use partially reflecting dichroic filters and, if possible, spectral filters to deliver only the photons of the secondary light rays to the optical detection system. However, the use of these filters results in a decrease in the detection performance of the optical system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2010 / 141092A2 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to at least partially remedy the drawbacks of the prior art, and more particularly to propose an optical focusing / collection system based on a reflective axicon optical system with improved performance, in particular having a relatively small size, a large associated numerical aperture, as well as a working distance that can be adapted according to the intended application, and which does not require the use of partially reflecting dichroic filters to separate the optical paths of the primary and secondary rays. [Means for solving the problem]

[0009] The object of the present invention is therefore an optical focusing / collection system intended to focus the so-called primary light beam emitted by an optical emitter onto a sample to be analyzed and to collect the so-called secondary light beams emitted by the sample in response to the primary light beam and to deliver them towards an optical detection system, this optical system comprising several optical parts each centred along the same main optical axis.

[0010] Thus, the optical system includes a first light shaping portion adapted to receive the primary light beam on an entrance surface and to provide the primary light beam ringed around the main optical axis by an exit surface.

[0011] The optical system also includes a second optical collection / collection section, the second optical collection / collection section comprising: - a so-called upper central reflective surface that is conical and formed by a central area surrounded by a peripheral area, the so-called upper central reflective surface being adapted to reflect by the peripheral area the annularized primary light rays coming from the exit surface of the first optical part and to reflect by the central area the incident secondary light rays coming from the so-called lower central reflective surface; - a lower central reflecting surface that is conical in shape and adapted to reflect and focus incident primary light rays originating from the upper central reflecting surface onto the sample and to collect and reflect secondary light rays emitted by the sample; - at least two truncated conical peripheral reflective surfaces optically connecting the upper and lower central reflective surfaces; Includes:

[0012] Finally, the optical system includes a third optical return portion including a reflective surface, the reflective surface being: - disposed along the main optical axis between the exit surface of the first optical section and the upper central reflective surface of the second optical section, and having a lateral dimension smaller than a lateral dimension of the annularized primary light beam provided by the exit surface; - adapted to reflect the secondary light rays originating from the central area of ​​the upper central reflecting surface towards the light detection system.

[0013] Some preferred and non-limiting aspects of the present optical system are as follows:

[0014] The first, second and third optical sections may be overlapped with one another axially, i.e., along the main optical axis.

[0015] The first optical portion may be reflective, with the entrance and exit surfaces being reflective.

[0016] The second optical section may be conical and reflective, with an upper central reflective surface and a lower central reflective surface superimposed on one another and coaxial along the main optical axis.

[0017] The second optical department is - an upper peripheral reflective surface in the shape of a hollow truncated cone radially surrounding the upper central reflective surface, the upper peripheral reflective surface being adapted to reflect primary light rays originating from the upper central reflective surface and secondary light rays originating from the so-called lower peripheral reflective surface; a lower peripheral reflective surface in the shape of a hollow truncated cone radially surrounding the lower central reflective surface, the lower peripheral reflective surface adapted to reflect primary light rays emanating from the upper peripheral reflective surface and secondary light rays emanating from the lower central reflective surface; may include:

[0018] The primary light rays can be collected by the lower central reflecting surface according to a central tilt angle relative to the main optical axis that is at least equal to 25°.

[0019] The second optic may have a numerical aperture of 0.5 or greater.

[0020] The second optical section may have a so-called working distance along the main optical axis, which is defined as the distance between the apex of the cone formed by the lower central reflective surface and the focal point, and which depends on the maximum inner diameter of the second optical focusing / collecting section on the one hand and on the outer shapes of the upper and lower peripheral reflective surfaces and the upper and lower central reflective surfaces on the other hand. The maximum inner diameter of the second optical section is defined here as the maximum distance connecting two opposite radial ends of the truncated cone-shaped peripheral reflective surface along an axis perpendicular to the main optical axis.

[0021] The present invention also relates to an analytical system comprising an optical system according to any one of the above features, a light emitter adapted to emit a primary light beam, and a light detection system adapted to detect a secondary light beam.

[0022] The light emitter can emit a collimated primary light beam, the collimated primary light beam incident on the entrance surface along a primary optical axis.

[0023] Other aspects, aims, advantages and features of the present invention will appear better on reading the following detailed description of preferred embodiments of the invention, given by way of non-limiting example, and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0024] [Figure 1]1 is a schematic cross-sectional view of an optical system coupled to a light emitter and a light detection system according to one embodiment. [Figure 2A] 2A and 2B show examples of converging cones of primary light rays emitted by a light emitter and delivered by the optical system shown in FIG. 1. [Figure 2B] 2 shows an example of a light collection cone of secondary rays emitted by a sample to be analyzed and collected by the optical system shown in FIG. 1 in response to a primary ray; [Figure 2C] 2 shows an example of a light collection cone of a measurement light beam, i.e., a portion of a secondary light beam collected by the optical system shown in FIG. 1 and detected by the light detection system. [Figure 3A] 2 is a schematic partial cross-sectional view of an optical system according to an embodiment similar to that shown in FIG. 1; [Figure 3B] 2 is a schematic partial perspective view of an optical system according to an embodiment similar to that illustrated in FIG. 1; [Figure 4] 1 is a schematic partial cross-sectional view of an optical collection / focusing portion of an optical system according to one variant; [Figure 5] 1 is a schematic partial cross-sectional view of an optical system according to a variant in which the reflection by the reflective surface of the optical collector / collector is a glass-type reflection (by total internal reflection); DETAILED DESCRIPTION OF THE INVENTION

[0025] In the figures and in the following description, the same reference symbols represent the same or similar elements. In addition, various elements are not drawn to scale to improve clarity of the figures. Furthermore, different embodiments and variations are not mutually exclusive and can be combined together. Unless otherwise stated, the terms "approximately," "about," and "in the range of" mean within a 10% margin, preferably within a 5% margin. Furthermore, the term "included between" and its equivalents means that the boundary is included unless otherwise stated.

[0026] FIG. 1 is a schematic partial cross-sectional view of an optical collection / focusing system 1 along a main optical axis Δ, according to one embodiment.

[0027] Here and in the following discussion, we consider the Cartesian 3D direct reference frame (e r , e θ , e z ) is defined, where the vector e z is centered on the main optical axis Δ of the optical system 1 and is directed from the sample 4 to be analyzed to the optical system 1, and the vector e r is axis e z is perpendicular to the vector e θ is the plane (e r , e z ) in the following description, the terms "lower" and "upper" refer to the vector +e z It should be understood that this relates to the increase in position when moving along the

[0028] The optical system 1 is adapted to focus the so-called primary light beam emitted by the light emitter 2 onto the sample 4 to be analyzed, and to collect the so-called secondary light beam emitted by the sample 4 in response to excitation of the sample 4 by the primary light beam and to deliver it in the direction of the light detection system 3. The part of the response light beam received by the light detection system 3 is called the measurement light beam. The optical system 1 is therefore arranged between the light emitter 2 and the light detection system 3 on the one hand and between the light emitter 2 and the sample 4 on the other hand. The optical system 1 can find application in particular in the fields of confocal microscopy and spectroscopy, for example of the Raman or fluorescence type.

[0029] In general, the optical system 1 comprises several optical parts superimposed on one another and centered along the main optical axis Δ of the optical system 1, among others: a first so-called light shaping part 10, adapted to emit a primary light beam by a light emitter 2 in an annular manner around a main optical axis Δ, a second so-called optical focusing / collection section 20 adapted to focus the annulated primary light beam received from the first optical section 10 onto the sample 4 and to collect light beams emitted by the sample 4 in response to excitation of the sample 4 by the annulated primary light beam, a third so-called optical return section 30 adapted to return the secondary light beam received from the second optical section 20 in the direction of the optical detection system 3; The third optical section 30 includes a reflective surface 31 located between the first optical section 10 and the second optical section 20 along the main optical axis Δ and inside the space radially bounded by the annularized primary light beams provided by the first optical section 10.

[0030] The light emitter 2 is adapted to emit a primary light beam in the direction of the first optical part 10 of the optical system 1. The light emitter 2 comprises a light source that emits the primary light beam. This light source may be, inter alia, a laser diode or a light emitting diode.

[0031] The primary light beams may be monochromatic or polychromatic. The central wavelength and spectral range of the primary light beams depend on the intended use of the optical system 1. For illustrative purposes, they may be in the visible range, ultraviolet range, or infrared range. Preferably, the primary light beams are monochromatic to limit chromatic aberrations associated with some possible refractive elements of the optical system.

[0032] Preferably, the primary light beam is solid and collimated. In other words, it has an angular intensity distribution that is continuous (e.g. of the Gaussian type) and therefore distinguishes it from an annular (and therefore hollow) light beam. In addition, when it is preferably collimated, its constituent rays are parallel to one another. The light emitter 2 can include a collimator (not shown) arranged at the output of the light source when the light source emits diverging light beams, as is the case for example with light-emitting diodes.

[0033] The optical detection system 3 is adapted to receive and detect the measurement beam, i.e., a portion of the secondary beam collected by the optical system. The optical detection system 3 can provide an electrical signal to the processing unit, the intensity of which represents the optical power of the detected secondary beam. The optical detection system 3 may consist of an avalanche photodiode, a CCD sensor, or any other equivalent photodetector.

[0034] As previously mentioned, the optical system 1 comprises at least three optical sections 10, 20, 30, each of which is centered and superimposed on one another along a main optical axis Δ, which passes through a focal point located on the sample 4 to be analyzed.

[0035] The first optical section 10 is adapted to shape the primary light beam emitted by the light emitter 2 into an annular shape around a main optical axis Δ and deliver it to the second optical section 20. The first optical section 10 is therefore a so-called shaping section.

[0036] Advantageously, the light shaping unit 10 here is reflective (i.e. formed only by reflective optical elements) when the primary light beam is polychromatic, in particular so as to limit the presence of chromatic aberrations, but also when the primary light beam is monochromatic. This optimizes the compactness of the optical system. In addition, the possibility of parasitic light beams being emitted by the diopter material, for example due to fluorescence, which can then be excited by the monochromatic primary light beam, is avoided. However, instead, the optical system can be refractive (formed only by refractive optical elements) or catadioptric (formed by refractive and reflective optical elements), in particular when the primary light beam is monochromatic.

[0037] In this example, light shaping portion 10 includes a conical central reflective surface 11 radially surrounded by a frusto-conical peripheral reflective surface 12. Reflective surface 11 is the entrance surface of light shaping portion 10, and reflective surface 12 is its exit surface. These different reflective surfaces are coaxial and centered on the main optical axis Δ.

[0038] The reflecting surface 11 is so-called conical, and is central insofar as the apex of the cone is located on the main optical axis Δ. In addition, the reflecting surface 11 corresponds to the outer surface of the cone (pointing towards the outside of the cone). Here, the reflecting surface 11 has a rectilinear contour, but may be convex or concave. The shape of the base of the cone is here circular (axisymmetric cone), but may also be elliptical or polygonal.

[0039] The reflecting surface 12 is the periphery of a so-called truncated cone. In other words, the reflecting surface 12 corresponds to the inner surface of the truncated cone (pointed towards the inside of the cone), so that the primary light rays can reach the reflecting surface 11. The reflecting surface 12 radially surrounds the reflecting surface 11, and the reflecting surfaces 11 and 12 are coaxial and centered on the main optical axis Δ. Preferably, the reflecting surface 12 has a linear or concave contour so as to limit the aperture angle of the reflected primary light rays. The shape of the base of the cone is here identical to that of the reflecting surface 11.

[0040] The reflecting surface 11 is directed towards the light emitter 2 and also towards the reflecting surface 12. The reflecting surface 12 is directed towards the reflecting surface 11 and also towards the reflecting surface 21 of the second optical section 20.

[0041] Thus, the reflecting surface 11 receives the solid and by now collimated primary light beam and reflects it towards the reflecting surface 12. The primary light beam then becomes annular and thus evenly dispersed around the main optical axis Δ. The primary light beam is reflected by the reflecting surface 12 to the reflecting surface 21 of the second optical section 20.

[0042] The second optical section 20 is adapted to focus the by now annular primary light beam onto the sample 4 and to collect the by now excited secondary light beam emitted by the sample 4 and deliver it to the light detection system 3. The second optical section 20 is therefore a so-called collector / collector.

[0043] The optical collection / collection section 20 is reflective. Therefore, it contains only reflective optical elements. The fact that the optical collection / collection section 20 is combined with the first optical section 10 and the third optical section 30 makes it possible to separate the optical paths of the primary and measurement beams while adapting the working distance and increasing the numerical aperture if necessary depending on the intended application.

[0044] The optical concentrator / collector 20 includes a conical central upper reflective surface 21 superimposed on a conical central lower reflective surface 24 along its major optical axis Δ. These reflective surfaces 21, 24 are optically coupled to one another by at least two truncated conical peripheral reflective surfaces 22, 23. In this example, the optical concentrator / collector 20 includes two truncated conical peripheral reflective surfaces, namely, upper reflective surface 22 and lower reflective surface 23, which are distinct from one another and positioned relative to one another such that each of the primary and secondary light rays is reflected at least once on upper reflective surface 22 and at least once on lower reflective surface 23. These distinct reflective surfaces are coaxial and centered on the major optical axis Δ.

[0045] The central reflecting surface 21 is adapted to reflect the by now annular primary light rays originating from the reflecting surface 12 towards the peripheral reflecting surface 22. The central reflecting surface 21 preferably corresponds to the outer surface of a cone having a convex profile. Preferably, the shape of the base of this untruncated cone is identical to that of the reflecting surface 12. The central reflecting surface 21 is positioned below and overlaps the reflecting surfaces 11 and 12. The primary light rays are then reflected by a peripheral area 21.1 located near the base of the cone. This peripheral area 21.1 is separate from the central area 21.2 of the reflecting surface 21, which is adapted to reflect the secondary light rays towards the reflecting surface 31 of the third light returning section 30. The central reflecting surface 21 is therefore also adapted to reflect the secondary light rays originating from the peripheral reflecting surface 22 towards the reflecting surface 31. The measurement light rays are then reflected by the central area 21.2 located near the apex. The central region 21.2 has a surface area of ​​at least 50%, preferably 57%, of the total surface area of ​​the central reflective surface 21. Surface area is defined herein as the area of ​​the plane (e r , eθ ) is defined as the surface projected onto

[0046] The peripheral reflective surface 22 is adapted to reflect primary light rays towards the peripheral reflective surface 23 and to reflect secondary light rays towards the central reflective surface 21. The peripheral reflective surface 22 radially surrounds the central reflective surface 21. The peripheral reflective surface 22 here has an outer shape which is preferably a concave truncated cone shape, its inner surface (facing towards the inside of this truncated cone).

[0047] The peripheral reflective surface 23 is adapted to reflect primary light rays toward the central reflective surface 24 and secondary light rays toward the peripheral reflective surface 22. The peripheral reflective surface 23 radially surrounds the central reflective surface 24 and is positioned below and overlapping the peripheral reflective surface 22. Preferably, the peripheral reflective surface 23 has a rectilinear outer profile in the shape of a truncated cone. The peripheral reflective surface 23 consists of an inner surface (facing the inside of the truncated cone).

[0048] 4 schematically illustrates an optical concentrating / collecting unit 20 according to a variation of the optical unit 20 illustrated in FIG. 1 (here associated with a metal-type reflector), where surfaces 21 and 22 have rectilinear profiles, surface 23 has a convex parabolic shape (with focal point F2), and surface 24 has a concave elliptical profile (with focal points F1 and F2). Note that this example is compatible with metal-type reflectors as well as glass-type reflectors (discussed in more detail below). In any case, each of reflective surfaces 22 and 23 has a profile adapted to ensure optical coupling between reflective surfaces 21 and 24. The profiles of these different reflective surfaces 21-24 may be concave, convex, rectilinear, parabolic, elliptical, etc.

[0049] The central reflecting surface 24 is adapted to reflect and focus the annularized primary light beams originating from the peripheral reflecting surface 23 onto the sample 4. The surface therefore has a concave profile. This untruncated cone has its apex directed towards the sample 4, and the reflecting surface 24 is its outer surface (directed towards the outside of the cone). The primary light beams are reflected by a peripheral area 24.1 arranged near the base of the cone. The central reflecting surface 24 is therefore also adapted to reflect the secondary light beams emitted by the excited sample 4 by this time towards the peripheral reflecting surface 23. The part of the secondary light beams collected by this time (measurement beams) that will be received by the light detection system 3 is reflected by a central area 24.2 arranged near the apex.

[0050] The third optical section 30 is adapted to deliver a measurement light beam to the light detection system 3. The third optical section 30 is thus called an optical return section.

[0051] The third optical section 30 is centered on the main optical axis Δ and includes a reflecting surface 31 arranged along the main optical axis Δ between the reflecting surface 12 and the central reflecting surface 21. In addition, the reflecting surface 31 is arranged in the space radially bounded by the annularized primary light beams provided by the reflecting surface 12. The reflecting surface 31 here directs the measurement light beams in the radial direction e r along the reflecting surface 31 and 32 in the direction of the second, now reflective, returning surface 32, which focuses the measurement beam onto the optical detection system 3. Alternatively, this reflecting surface 32 may not be present, or several reflecting surfaces 32 may be provided in the path of the measurement beam. In addition, optical filters and other optical elements may be arranged between surfaces 31 and 32, if necessary.

[0052] In operation, the light emitter 2 emits a primary light beam, here monochromatic, solid and collimated, along the main optical axis Δ towards the optical system 1. The optical system 1 shapes the primary light beam and focuses it onto the sample 4 to be analyzed.

[0053] First, the primary light beam is received by a light shaping element 10, which causes the primary light beam to become annular. To do this, the primary light beam is radially reflected by a conical reflective surface 11 towards a truncated conical reflective surface 12, which then reflects the primary light beam towards an optical focusing / collection element 20. The primary light beam is then annularized.

[0054] The primary ray, which has now become annular, propagates along the main optical axis Δ without being disturbed by the presence of the reflecting surface 31 of the light returning section 30. In fact, the latter is a plane (e r , e θ ) has the dimensions shown.

[0055] The primary light beam is then received by the optical focuser / collector 20, which focuses the primary light beam at a focal point located on the sample 4. To be focused, the primary light beam is radially reflected at its peripheral area 21.1 by a conical reflective surface 21 towards a truncated conical reflective surface 22, which reflects it towards a truncated conical reflective surface 23, which then reflects it towards a conical reflective surface 24, which focuses the primary light beam onto the sample 4 to be analyzed.

[0056] Figure 2A illustrates an example of a converging cone of primary rays on an analyzed sample 4. Figure 2A here consists of the angular intensity distribution If of the primary rays around the main optical axis Δ.

[0057] The primary ray is inclined at an angle φ with respect to the principal optical axis Δ. f The aperture angle Δφ f so that the primary ray is contained within a cone, where the minimum angle φ f -Δφ f / 2 and maximum angle φ f +Δφ f The angle φ is separated by 2 / f and is annular about the principal optical axis Δ. In this example the primary rays are annular on a circular base, but the same theory applies to rings with polygonal bases.

[0058] The combination of the light shaping section 10 and the optical collection / collection section 20 provides a significant minimum tilt angle φ, for example at least equal to 25°, or at least equal to 40°. f -Δφ f In this example, it becomes possible to obtain a minimum tilt angle φ f -Δφ f / 2 is approximately equal to 45°, and the opening angle Δφ f is equal to approximately 5°.

[0059] This particularly inclined focusing makes it possible to focus the working distance according to the intended application, which is defined here as the distance along the main optical axis Δ between the vertex of the reflecting surface 24 and the sample 4 to be analyzed. For example, the working distance may thus be between about 0.5 mm and about 5 mm for a maximum inner diameter of the optical part 20 of about 4 cm. As previously mentioned, this maximum inner diameter D is defined here as the maximum distance connecting two opposite points on the radial ends of the respective reflecting surfaces 22 and 23 along an axis perpendicular to the main optical axis Δ (see FIG. 3A). Thus, for a given value of the maximum inner diameter D of the optical part 20, it is possible to have a small working distance (and therefore a very large numerical aperture) for applications requiring very compactness, or a larger working distance (and therefore a numerical aperture that may remain large) for applications requiring, for example, the insertion of a working substance between the optical system 1 and the sample 4. The value of the working distance depends on the value of the maximum inner diameter D and the outer shapes of the reflecting surfaces 21, 22, 23 and 24.

[0060] Thus, the performance of the optical system and the uniformity of the illumination of the sample are improved by averaging the illumination according to the large aperture angle of the optical system 1, for example in the range of 0.7. In addition, the size of the optical system 1 is particularly reduced. Also, the use of dichroic filters is not necessary.

[0061] Returning to Figure 1, the sample 4 to be analyzed is by this time excited by the primary light beam, but instead emits a secondary light beam in the direction of the optical system 1. By way of illustration, the secondary light beam may consist of a fluorescence type radiation, in which case the central wavelength of the secondary light beam may be greater than that of the primary light beam, or may consist of a Raman type radiation, in which case the central wavelength of the secondary light beam is close to that of the primary light beam.

[0062] First, the secondary light rays are collected by optical concentration / collection portion 20, which reflects them towards light return portion 30. Thus, the secondary light rays are radially reflected by conical reflective surface 24 towards truncated conical reflective surface 23 (thus making the secondary light rays annular), then reflected by reflective surface 23 towards truncated conical reflective surface 22, then reflected by reflective surface 22 towards conical reflective surface 21, which finally reflects the secondary light rays towards light return portion 30.

[0063] In this way, the secondary light rays can be collected by the entire surface area of ​​the reflective surface 24. Therefore, the optical system does not have an inherent dark region in the light collection cone, i.e., a zero intensity area (hollow light collection cone), at the main optical axis due to the operating principle of the optical system, which improves the performance of the optical system 1.

[0064] In this regard, Figure 2B illustrates an example of a cone for collecting secondary rays by the reflecting surface 24. Figure 2B now comprises the angular intensity distribution Ic of the secondary rays around the main optical axis Δ.

[0065] Thus, the light collection cone is solid, i.e., the secondary rays are incident at 0° and φ c,max , and the optical system has no dark areas in the light collection cone. In this example, the angle φ c,max is φ f -Δφ f / 2 and φ f +Δφ f / 2, but can be greater than these values. The collection efficiency is therefore particularly large. The collection efficiency can be defined as the ratio between the number of photons emitted and collected by the sample 4 and the number of secondary photons emitted by the sample. The collection efficiency is the ratio between the cumulative intensity of the secondary rays collected in the light collection cone and the half space (e r ,e θ ,+e z ) and the cumulative intensity of the secondary rays collected in the

[0066] Returning to Figure 1, the secondary light beam, which has now become annular, is reflected by the reflecting surface 21 in the direction of the reflecting surface 31 of the light returning section 30. Preferably, the secondary light beam has become solid again by this time.

[0067] The secondary light beam received by the reflecting surface 31 is the portion of the measurement beam, i.e. the secondary light beam received by the optical detection system 3. The secondary light beam is reflected by the central area 21.2 of the reflecting surface 21 and propagates in a space radially bounded by the annular primary light beam propagating between the reflecting surfaces 12 and 21.

[0068] In this way, a small portion of the collected secondary rays (reflected by the peripheral area 21.1) is reflected towards the light shaping part 10. However, this peripheral area 21.1 has a smaller surface area than that of the central area 21.2, which results in a particularly high detection rate, which can improve the performance of the optical system.

[0069] The measurement beam is then reflected by the reflecting surface 32 and focused onto the focal plane of the light detection system 3 .

[0070] FIG. 2C illustrates an example of a cone for light collection by the reflecting surface 24 associated with the measurement beam. FIG. 2C here consists of the angular intensity distribution Im of the measurement beam around the main optical axis Δ. In particular, FIG. 2C consists of the portion of the secondary beam collected by the central area 24.2. The light collection cone of the secondary beam corresponds to the first order of magnitude to the sum of the collection cone illustrated in FIG. 2A and the light collection cone of the measurement beam illustrated in FIG. 2C. The aperture angle Δφf As long as is small, the light collection cone of the measurement ray and therefore the detection rate are particularly large.

[0071] The optical system 1 thus makes it possible to focus the primary light beam emitted by the light emitter 2 onto the sample to be analyzed, then to collect the secondary light beams emitted by the by now excited sample 4, and finally to deliver the secondary light beams to the optical detection system 3. In this example, the optical system 1 is entirely reflective, which makes it possible, inter alia, to eliminate chromatic and spherical aberrations and to make a particularly compact optical system.

[0072] Furthermore, due to the superposition of the three optical sections 10, 20, 30 centered on the main optical axis Δ, and in particular the fact that optical section 10 annularizes the primary light beam for subsequent delivery to optical collection / focusing section 20, optical system 1 has a working distance that can be adapted for a given value of the maximum inner diameter D of optical section 20 and a large numerical aperture, for example in the range of 0.7, preferably 0.5 or greater. In addition, due to the fact that reflective surface 31 of optical section 30 is located between optical sections 10 and 30 and is disposed inside the space radially bounded by the by-now annular primary light beam, this optical system allows for the separation of the optical paths associated with the primary light beam and the measurement light beam. This optical system therefore makes it possible to avoid the use of dichroic mirrors or filters, thereby improving the performance of optical system 1. The collection efficiency as well as the detection efficiency are optimized. Moreover, relying on such a spatial separation method makes it possible to limit the parasitic fluorescence phenomena of the reflective surface caused by the primary beam that may be captured by the optical detection system, thus particularly increasing the signal-to-noise ratio.

[0073] 3A and 3B are schematic partial cross-sectional (FIG. 3A) and partial perspective (FIG. 3B) views of an optical system 1 similar to that shown in FIG. 1. In this embodiment, the reflection of the emitted and collected light rays is a metallic-type reflection. More specifically, these light rays propagate here in a fluid medium or in a vacuum within the optical collection / focusing section 20 and are reflected by reflective surfaces 21-24 made on the basis of metals (Ag, Al, Au, etc.).

[0074] The optical system 1 comprises several rigid blocks assembled together around a mechanical axis corresponding to the main optical axis Δ.

[0075] The optical system 1 is here -e r The optical axis Δ of the optical fiber 10 includes a cover 41 containing a radial conduit 42 intended to allow propagation of primary light rays along the direction, the radial conduit 42 having a reflective surface 43 centered on the main optical axis Δ and adapted to reflect incident primary light rays in the direction of the reflective surface 11.

[0076] The optical system 1 includes a first internal structure 44 that is disposed below and in contact with the cover 41 and that includes a through-hole 45 in which a solid, axisymmetric cone is disposed. The axisymmetric cone has an upper surface on which the reflective surface 11 is defined and a lower surface on which the reflective surface 31 is defined. The boundary of the through-hole is configured to define a frustoconical reflective surface 12 (not shown here). The free space between the complete axisymmetric cone and the boundary of the through-hole 45 allows the propagation of the primary light rays, which are now circular.

[0077] The optical system 1 comprises a second internal structure 46, which is arranged below and in contact with the first internal structure 44, and which comprises a through-hole 47 that allows the propagation of the annularized primary light beam up to the reflecting surface 21. The second internal structure 46 comprises a radial duct 48 that allows the propagation of the measurement light beam and its subsequent reflection by the reflecting surface 31 (via the reflecting surface 32) towards the light detection system. The through-hole 47 has a larger lateral dimension at the bottom of the second internal structure 46. The inner surface of the through-hole 47 then defines the reflecting surface 22.

[0078] Optical system 1 includes a third internal structure 49 disposed below and in contact with second internal structure 46. Third internal structure 49 includes a central block, the upper surface of which defines conical reflective surface 21, and the lower surface of which defines conical reflective surface 24.

[0079] The optical system 1 includes a fourth structure 50 disposed below and in contact with the third internal structure 49. The fourth structure 50 includes a through hole 51 into which extends partially a central block including a conical reflective surface 24. An internal boundary defines the reflective surface 23.

[0080] Finally, the holding structure 52 is assembled to the fourth structure 50 and contacts the first structure 44, the second structure 46, and the third structure 49 to ensure their holding. The optical system 1 is thus particularly compact and can have dimensions of 5 x 5 x 5 cm or less. This optimized optical system according to the invention can have particularly low optical losses due to the mechanical structure, for example less than 7%.

[0081] Having now described specific embodiments, various variations and modifications will be apparent to those skilled in the art.

[0082] Thus, optical fibers can ensure optical coupling between the light emitter 2 and the reflecting surface 11 and between the reflecting surface 31 or 32 and the light detection system 3 .

[0083] Furthermore, a spectral filter may be disposed between the reflective surface 31 or 32 and the light detection system 3 so as to deliver only the spectral band intended to be detected.

[0084] Finally, in general, the reflection of light rays emitted and / or collected by the reflective surfaces of the optical system 1 may be metal-type reflection (as in the examples of Figures 3A and 3B) and / or glass-type reflection (i.e., total internal reflection).

[0085] In this regard, Fig. 5 illustrates an optical system 1 according to another embodiment, in which the reflection of the light rays emitted and collected by the reflective surfaces 21-24 of the optical concentrator / collector 20 is a glass-type reflection, i.e., by total internal reflection. The light rays propagate through the optical part 20 in a solid material 20.1 (e.g., optical polymer, diamond, etc.) that is transparent to the wavelength of the light rays. The curvature of the mirror is such that the angle of reflection always satisfies the well-known condition for total internal reflection, which here includes the refractive indices of the transparent material 20.1 and the environment G. In this regard, in this example, the transparent material 20.1 may consist of an optical polymer (e.g., of the Zeonex® type) with a refractive index equal to 1.5, surrounded by air G with a refractive index equal to 1.

[0086] In this example, emitted light rays propagate through light shaping section 10 in a fluid medium or vacuum and are reflected by metallic reflective surfaces 11 and 12. The light rays then enter optical section 20 by orthogonally intersecting (here flat) upstream face 25 and propagate through the transparent material. The light rays are reflected by reflective surfaces 21-24 by total internal reflection. The light rays exit optical section 20 by orthogonally intersecting (here curved) downstream face 26, which here has a spherical shape with its center coincident with the focal point of optical system 1. The collected light rays follow a similar retrograde path to reflective surface 31.

[0087] In particular, the optical system 1 according to this variant has the advantage that the reflective surfaces 21-24 have a very high reflectivity, higher than that of metal surfaces, which improves the performance of the optical system 1. In addition, the optical part 20 is made in one piece from the same material, which simplifies the manufacture and the relative arrangement of the different elements, especially compared to when the optical part 20 is formed from several separate elements. In addition, the surfaces 21 and 24 no longer require a mechanical holding system to be arranged in the path of the light beam. [Explanation of symbols]

[0088] 1 Optical focusing / collection system, optical system 2 light emitter 3. Optical detection system 4. Sample 10. Optical shaping section, first optical section 11 Central reflective surface, metal reflective surface, incident surface 12. Peripheral reflective surface, metallic reflective surface, exit surface 20 Optical focusing / collection section, second optical section 20.1 Solid materials, transparent materials 21 Reflective surface, central reflective surface, upper central reflective surface 21.1 Surrounding Areas 21.2 Central area 22 Peripheral reflective surface, upper reflective surface 23 Peripheral reflective surface, lower reflective surface 24 Lower central reflective surface, lower central reflective surface 25 Upstream side 26 Downstream side 30 Optical Restoration Department, Third Optical Department 31 Reflective surface 32 Second return surface 41 Cover 42 Radial Conduit 43 Reflective surface 44 First Internal Structure 45 Through opening 46 Second internal structure 47 Through hole 48 Radial Duct 49 Third Internal Structure 50 Fourth Structure 51 through holes 52 Retention structure

Claims

1. 1. An optical collection / focusing system (1) intended to focus a primary light beam emitted by an optical emitter (2) onto a sample (4) to be analyzed and to collect secondary light beams emitted by said sample (4) in response to said primary light beam and deliver them to an optical detection system (3), said optical collection / focusing system (1) comprising several optical sections (10, 20, 30) each centered along the same main optical axis (Δ), said several optical sections (10, 20, 30) comprising: a first light shaping unit (10) that receives the primary light beams on an entrance surface (11) and provides the primary light beams from an exit surface (12) that are annularized around the main optical axis (Δ); a second optical collection / focusing section (20), an upper central reflective surface (21) having a conical shape and formed by a central area (21.2) surrounded by a peripheral area (21.1), the upper central reflective surface (21) being configured to reflect the annularized primary light rays coming from the exit surface (12) of the first optical section (10) by the peripheral area (21.1) and to reflect incident secondary light rays coming from a lower central reflective surface (24) by the central area (21.2); a lower central reflective surface (24) that is conical in shape and configured to reflect and focus incident primary light rays originating from the upper central reflective surface (21) onto the sample (4) and to collect and reflect the secondary light rays emitted by the sample (4); at least two frustoconical peripheral reflective surfaces (22, 23) optically connecting the upper central reflective surface (21) and the lower central reflective surface (24); a second optical collection / focusing section (20) including: A third light returning portion (30) including a reflective surface (31), wherein the reflective surface (31) is a second optical section (20) having a transverse dimension smaller than that of the annular primary light beam provided by the exit surface (12), the second optical section (20) being disposed along the main optical axis (Δ) between the exit surface (12) of the first optical section (10) and the upper central reflecting surface (21); configured to reflect the secondary light rays originating from the central area (21.2) of the upper central reflecting surface (21) towards the light detection system (3), A third optical recovery section (30); An optical collection / focusing system (1) comprising:

2. 2. The optical collection / focusing system (1) according to claim 1, wherein the first, second and third optical sections (10, 20, 30) are axially superimposed on one another along the main optical axis (Δ).

3. 3. The optical collection / focusing system (1) according to claim 1 or 2, wherein the first optical section (10) is a reflective optical system, and the entrance surface (11) and the exit surface (12) are reflective surfaces.

4. 4. The optical focusing / collection system (1) according to claim 1, wherein the second optical section (20) is a conical and reflective optical system, and the upper central reflective surface (21) and the lower central reflective surface (24) are superimposed on each other and coaxial along the main optical axis (Δ).

5. The at least two truncated conical peripheral reflecting surfaces (22, 23) of the second optical section (20) are an upper peripheral reflective surface (22) in the shape of a hollow truncated cone radially surrounding the upper central reflective surface (21), the upper peripheral reflective surface (22) reflecting the primary light rays originating from the upper central reflective surface (21) and reflecting the secondary light rays originating from a lower peripheral reflective surface (23); a lower peripheral reflective surface (23) in the shape of a hollow truncated cone radially surrounding the lower central reflective surface (24), the lower peripheral reflective surface (23) reflecting the primary light rays originating from the upper peripheral reflective surface (22) and reflecting the secondary light rays originating from the lower central reflective surface (24); 5. An optical collection / focusing system (1) according to any one of claims 1 to 4, comprising:

6. 6. The optical focusing / collection system (1) according to any one of claims 1 to 5, wherein the primary light rays are focused by the lower central reflective surface (24) according to a central tilt angle with respect to the main optical axis (Δ) equal to at least 25°.

7. 7. The optical collection / focusing system (1) according to any one of the preceding claims, wherein the second optical section (20) has a numerical aperture of 0.5 or greater.

8. 8. The optical focusing / collection system (1) according to claim 1, wherein the second optical section (20) has a so-called working distance along the main optical axis (Δ) between the apex of the cone formed by the lower central reflective surface (24) and the focal point, the working distance depending on the maximum inner diameter (D) of the optical section (20) on the one hand and on the outer shapes of the at least two truncated conical peripheral reflective surfaces (22, 23) and the upper central reflective surface (21) and the lower central reflective surface (24) on the other hand, the maximum inner diameter (D) being defined as the maximum distance between two opposite points on the radial ends of the at least two truncated conical peripheral reflective surfaces (22, 23) along an axis perpendicular to the main optical axis (Δ).

9. 9. An analysis system comprising an optical collection / focusing system (1) according to any one of claims 1 to 8, an optical emitter (2) for emitting the primary light beam, and an optical detection system (3) for detecting the secondary light beam.

10. 10. The analytical system of claim 9, wherein the light emitter (2) emits a collimated primary light beam, the collimated primary light beam being incident on the entrance surface (11) along the main optical axis (Δ).

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