• 专利附录
  • 专利说明
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    • 专利摘要:
    In one aspect, the invention relates to a light beam transport and control device for endo-microscopic lensless imaging comprising a packet of monomode optical fibers (40), each monomode optical fiber being adapted to receive an elementary light beam. at a proximal end and emitting a light beam at a distal end; a multimode optical fiber section (50) arranged at the distal end of the optical fiber packet and for receiving the light beams emitted by the monomode optical fibers of the optical fiber packet; an optical phase control device arranged on the proximal end side of the monomode optical fiber packet. The optical phase control device comprises at least a first spatial light modulator (30) adapted for the application of a phase shift on each of the elementary beams and control means (60) of the first spatial light modulator allowing the applying a phase shift on each of the elementary beams to form at the distal end of the multimode optical fiber (50) an illumination beam with a determined phase function.
    公开号:FR3049719A1
    申请号:FR1652937
    申请日:2016-04-04
    公开日:2017-10-06
    发明作者:Herve Rigneault；Esben Andresen；Siddarth Sivankutty
    申请人:Aix Marseille Universite；Centre National de la Recherche Scientifique CNRS；Ecole Centrale de Marseille；
    IPC主号:
    专利说明:

    En pratique, la détermination de la matrice Jp peut être partielle et se limiter par exemple à déterminer la matrice p" qui contrôle essentiellement la répartition d’intensité dans le plan de l’objet (l’amplitude jp jouant un rôle marginal). Il est également possible de déterminer la matrice Jp. de façon incomplète mais cela pourra entraîner une moins bonne précision sur la fonction de phase recherchée pour le faisceau d’illumination.
    Pour la détermination de la matrice Jp de l’ensemble formé du paquet de fibres optiques monomodes et du tronçon de fibre multimodes, il est possible d’utiliser des méthodes interférentielles basées sur des mesures d’interférence entre l’onde lumineuse en sortie de la fibre optique multimodes et une onde de référence. La figure d’interférence est analysée pour des déphasages successifs appliqués sur chacun des faisceaux élémentaires ou, de manière équivalente sur la référence, ce qui permet de déterminer la matrice Jp . Ce type de méthode est décrit par exemple dans l’article de Cizmar et al. où l’on cherche à déterminer la matrice de transmission d’une fibre optique multimodes (voir ‘Shaping the light transmission through a multimode optical fibre: complex transformation analysis and applications in biophotonics' Opt
    Express 19, 18871-18884 (2011)).
    La matrice de transmission étant déterminée, elle peut être enregistrée dans l’unité de contrôle 60 du modulateur spatial de lumière 30, si bien qu’une calibration préalable n’est pas nécessaire pour chaque mise en œuvre du procédé d’imagerie. Alternativement, il est possible avant de démarrer une nouvelle imagerie, de procéder à nouveau à une calibration.
    Les figures 4B et 4C illustrent une étape de calibration préalable du procédé de transport et de contrôle des faisceaux lumineux selon la présente description, basé sur une caractérisation du système formé par le paquet de fibres optiques monomodes et le tronçon de fibre multimodes, et adaptée spécifiquement à la formation d’un point de focalisation, qu’il soit ou non balayé.
    Dans cet exemple, on suppose que l’on cherche à former des points de focalisation en différents points du plan n0bj positionné à une distance z de la face de sortie 52 de la fibre optique multimodes, comme cela est représenté sur la FIG. 4A. Chaque point de focalisation correspond à un faisceau convergent B3k. En pratique, on cherchera par exemple à balayer un champ objet prédéterminé et donc à faire varier les déphasages appliqués au moyen du modulateur spatial de lumière 30 sur les faisceaux lumineux élémentaires Bu pour obtenir le balayage recherché du champ objet.
    Pour la mise en œuvre de la calibration, un détecteur matriciel, par exemple une caméra, est agencée dans le plan de l’objet n0bj ou dans un plan conjugué. A chaque pixel de la caméra correspond un « mode de sortie » référencé u. le nombre de modes de sortie u correspond ainsi dans cet exemple au nombre M de pixels de la caméra. On cherche à déterminer les phases Φί à appliquer aux faisceaux lumineux élémentaires Bu pour rendre maximale l’intensité de chaque mode de sortie u.
    Plus précisément, on peut définir une matrice de transmission complexe J£u reliant les N modes d’entrée i et les M modes de sortie u :
    le nombre N de modes d’entrée est limité par le nombre de fibres optiques monomodes dans le paquet de fibres 40 et le nombre M de modes de sortie est limité par le nombre de pixels de la caméra.
    Comme précédemment expliqué, la matrice de transmission J£u complexe, d’amplitude Jp. et de phase pu :
    En pratique, la détermination de la matrice J£u revient à mesurer seulement la matrice p“ qui contrôle essentiellement la répartition d’intensité dans le plan de l’objet.
    La détermination de la matrice p“ peut comprendre les étapes suivantes :
    Envoi de deux modes d’entrée, un mode de référence / = 0 et un mode d’entrée / auquel il est adjoint une phase Φ ;
    Enregistrement pour chaque mode de sortie u, c'est-à-dire pour chaque pixel de la caméra, de l’intensité résultante pour un nombre donné de laveurs équidistantes de <t>h par exemple 8, entre 0 et 2π, comme cela est montré sur la FIG. 4C ;
    Enregistrement pour chaque mode de sortie u de la phase Φ, qui rend maximale l’intensité (FIG. 4B) ; Réitération pour chaque mode d’entrée i.
    Bien entendu, les étapes de calibration du procédé de transport et de contrôle des faisceaux lumineux décrits précédemment peuvent s’appliquer également quand le paquet de fibres optiques monomodes 40 et le tronçon de fibre multimodes 50 sont agencés différemment.
    Notamment, si la face d’entrée 51 est dans le même plan, ou dans un plan conjugué avec la face de sortie 42 du paquet de fibres monomodes 40, le plan intermédiaire associé à la face d’entrée 51 de la fibre multimodes 50 peut être indexé dans l’espace réel (x, y).
    La FIG. 5 représente un exemple de montage expérimental mis en œuvre pour la validation d’un procédé de transport et de contrôle de faisceaux lumineux selon la présente description.
    Le montage expérimental comprend une source laser 10 émettant un faisceau lumineux envoyé sur un « façonneur de front d’onde » 503, par exemple une matrice de microlentilles ou un modulateur spatial de lumière à deux dimensions inscrivant un réseau de phases quadratiques simulant une matrices de microlentilles, et permettant de former un ensemble de faisceaux élémentaires focalisés sur les segments d’un miroir déformable segmenté 30. Un télescope 504, 506 permet d’ajuster la dimension du faisceau dans le plan du miroir déformable 30. Chaque segment du miroir déformable 30 est imagé sur une fibre monomode du paquet de fibres optiques monomodes 40 (imageur 508, 513, 515, 516). Un dispositif de contrôle 60 du miroir déformable 30 permet de contrôler la phase Φχ associée à chaque mode d’entrée i et correspondant à chacun des faisceaux élémentaires. Une lentille de focale f = 500 μηι (non visible sur la FIG. 5) est placée sur la face de sortie du paquet de fibres 40 de telle sorte que la face de sortie du paquet de fibres 40 et la face d’entrée de la fibre multimodes 50 se trouvent dans des plans de Fourier. La répartition de l’intensité dans le plan de l’objet 101 est observée au moyen d’une caméra CMOS 520 comprenant M = 4096 pixels et conjuguée avec le plan de l’objet 101 au moyen d’in objectif 517. L’ensemble formé d’une lame demi-onde 501 et d’un polariseur 502 permet d’ajuster l’état de polarisation afin qu’il coïncide avec celui pour lequel le façonneur de front d’onde 503 est actif dans le cas ou ce composant utilise des cristaux liquides ; d’autre part ce montage permet d’ajuster la puissance envoyée sur l’échantillon 101. Un polariseur 518 permet de sélectionner un seul état de polarisation pour lequel la matrice de transmission est mesurée et le point de focalisation dans le plan n0bj optimisé. Une lame séparatrice 22 permet de renvoyer vers un détecteur 20 la lumière rétrodiffusée ou émise (dans le cas de la fluorescence) par l’objet et transmise du côté distal au côté proximal par le tronçon de fibre multimodes et le premier guide de lumière. Par exemple, le détecteur 20 est un photomultiplicateur ou une photodiode à avalanche. Lorsqu’on balaye l’échantillon 101 à l’aide d’un faisceau focalisé, on collecte le signal rétrodiffusé ou émis par chaque point de l’échantillon à l’aide du détecteur 101 afin de former une image.
    Une calibration du procédé de transport et de contrôle des faisceaux lumineux mis en œuvre grâce au montage expérimental de la FIG. 5 a par ailleurs été réalisée afin de contrôler la positon d’un point de focalisation dans le champ de l’objet n0bj comme cela est illustré sur le schéma de la FIG. 6A. La calibration est réalisée selon le protocole de détermination de la matrice de transmission décrit précédemment.
    Dans l’exemple montré sur la FIG. 6A, le plan de l’objet se trouve à une distance z = 250 pm de la face de sortie du tronçon de fibre multimodes.
    On observe sur la FIG. 6B un point de focalisation dans le plan de l’objet obtenu grâce au dispositif montré sur la FIG. 5. Comme cela est visible, aucune réplique n’est apparente. La FIG. 6C représente un sous-ensemble de points de focalisation correspondant à différents modes de sortie u obtenus par application de phases Φ, sur les lumineux élémentaires Bu. Dans la pratique un seul point de focalisation n’est visible comme indiqué sur la Fig. 6B, la Fig. 6C montre plusieurs points pour apprécier le champ de vue.
    Ainsi, les déposants ont montré tant théoriquement qu’expérimentalement, qu’après une distance de propagation dans le cœur de la fibre multimodes très courte, typiquement 1 mm ou quelques millimètres en fonction de la nature de la fibre, les modes de propagation présentent des phases aléatoires. Cette nature aléatoire des phases associées à chaque mode de propagation de la fibre multimodes est à l’origine même de la disparition des répliques. Les déphasages relatifs entre les modes de la fibre multimodes résultants de la propagation, on comprend pourquoi une fibre multimodes à saut d’indice est plus efficace qu’une fibre multimodes à gradient d’indice pour brouiller les modes ; en effet dans une fibre à saut d’indice, les constantes de propagations associées à chacun des modes sont plus dispersées, donnant lieu à des déphasages différentiels plus importants.
    Bien que les phases accumulées par les différents modes, lors de la propagation dans la fibre multimodes, soient finalement aléatoires, elles sont cependant déterministes et sont inclus dans la détermination de la matrice de transmission englobant le premier guide de lumière et la fibre optique multimodes.
    Les déposants ont ainsi démontré la faisabilité d’un dispositif de transport et de contrôle de faisceaux lumineux pour l’endo-microscopie sans lentille, une fonction de balayage du champ de l’objet à une distance donnée z de la face de sortie 52 du tronçon de fibre optique multimodes 50 pouvant être obtenue par contrôle des déphasages appliqués au moyen du modulateur spatial de lumière 30.
    Le dispositif de transport et de contrôle de faisceaux lumineux selon la présente description permet également de choisir la distance z du plan de l’objet. Pour cela, une calibration telle que décrite précédemment peut être effectuée pour un ensemble de valeurs z de la distance entre le plan de l’objet et la face de sortie 52 du tronçon de fibre optique multimodes.
    La FIG. 7 montre ainsi des images de billes fluorescentes obtenues au moyen du montage expérimental de la FIG. 5 et détectées par le détecteur 20, pour des valeurs de z égales à z = 10 pm (a), z = 40 pm (b), z = 70 pm (c), z = 100 pm (d).
    Plus précisément, la source lumineuse utilisée pour obtenir ces images est un laser Titane : Saphir à 800 nm émettant des impulsions de 200 fs ; les images obtenues sont des images à deux photons, le détecteur 20 est une photodiode à avalanche.
    Ces résultats expérimentaux démontrent ainsi également l’application du procédé de transport et de contrôle de faisceaux lumineux en imagerie non linéaire, le dispositif étant adapté à la transmission d’impulsions courtes.
    Cependant, dans le cas de manipulations d’impulsions ultra-courtes, le dispositif de transport et de contrôle de faisceaux lumineux selon la présente description peut comprendre également un dispositif de contrôle de la vitesse de groupe des impulsions lumineuses dans le paquet de fibres optiques monomodes, comme cela est décrit dans la publication de E.R. Andresen et al. (« Measurement and compensation of residual group delay in a multi-core fiber for lensless endoscopy”, JOSAB, Vol. 32, No. 6, 1221 - 1228 (2015)).
    Il est ainsi possible grâce au procédé décrit de réaliser de l’imagerie endo- microscopique sans lentille. Outre le transport et le contrôle des faisceaux lumineux au moyen du procédé décrit précédemment, le procédé d’imagerie endo-microscopique pourra comprendre la détection de la lumière rétrodiffusée par l’objet et transmise à travers la fibre multimodes et le paquet de fibres optiques monomodes de leur extrémité distale à leur extrémité proximale.
    Bien que décrits à travers un certain nombre d’exemples de réalisation détaillés, le dispositif de transport et de contrôle d’impulsions lumineuses pour l’imagerie endo-microscopique dite « sans lentille » ainsi que les systèmes et procédés d’imagerie endo-microscopiques sans lentille comprennent différentes variantes, modifications et perfectionnements qui apparaîtront de façon évidente à l’homme de l’art, étant entendu que ces différentes variantes, modifications et perfectionnements font partie de la portée de l’invention, telle que définie par les revendications qui suivent.
    STATE OF THE ART
    Technical field of the invention
    The present invention relates to light beam transport and control devices and methods for endo-microscopic "lensless" imaging as well as endo-microscopic imaging systems and methods without a lens. It applies in particular to the endoscopic exploration of organs in a living being, human or animal.
    State of the art
    The developments in endo-microscopic imaging require the use of fiber optic devices with specificities compared to imaging systems in free space.
    Indeed, the construction of a miniature microscope that would include a light source, focusing optics and a camera at the distal end (ie located at the end of the fiber, on the sample side). a medical endoscope is not possible because of the bulk of all components. In this way, solutions are sought that make it possible to perform imaging at the end of an optical fiber while limiting the bulk at the distal end of the endoscope.
    There are several approaches for performing imaging at the end of optical fiber while limiting the bulk at the distal end of the endoscope.
    In particular, a technology known as "endoscopy without a lens", and described for example in Cizmar et al. Exploiting multimode waveguides for pure fiber-based imaging, Nat. Common. 3, 1027 (2012). This technique is based on the use of a multimode optical fiber, or MMF according to the abbreviation of the Anglo-Saxon term "Multi-Mode Fiber". The MMF optical fiber is illuminated with a coherent source. On the proximal side (that is, at the optical fiber input, on the opposite side of the sample) of the optical fiber MMF, a Spatial Light Modulator (SLM) allows play on the propagation modes of the fiber so that the coherent addition of these modes makes it possible to generate the desired intensity figure at the end of the MMF fiber. In one embodiment, it is desired, for example, to produce a focal point at the end of the MMF fiber and to scan the sample to obtain an image as would be done in a conventional confocal microscopy assembly.
    This technique, extremely powerful because of the deterministic nature of the transmission matrix of the fiber which connects a field entering the proximal portion of the fiber with a distal outgoing field (and vice versa), eliminates all optics the distal side of the multimode fiber and thereby reduce the bulk.
    However, the transmission matrix of the fiber is highly dependent on the curvature of the optical fiber MMF. Endo-microscopic imaging using an optical fiber MMF is therefore extremely sensitive to any movement of the fiber. Moreover, because of the multimode nature, a short pulse in the proximal portion is elongated distally, which limits the possibilities of application to nonlinear imaging that requires working with light pulses of high peak intensities.
    In parallel with technologies based on the use of multimode fibers, a "lensless" type of technology has also been developed, based on the use of a packet of single-mode optical fibers (see, for example, French et al., US Pat. 8585587). According to the technique described, a wavefront spatial modulator (SLM) arranged on the proximal side of the monomode optical fiber packet makes it possible to control the wavefront emitted by a light source at the distal end of the fiber packet. This technique is much less sensitive to movements, including twists of the fiber optic packet. Indeed, the modes of monomode optical fibers being located and confined to defined points on the transverse surface of the packet of optical fibers, a twist of the optical fiber packet results in a simple translation of the intensity figure. In addition, the monomode nature of the fibers eliminates intermodal dispersion; thus, the only contribution to the dispersion is the chromatic dispersion which is the same for all monomode optical fibers and which can therefore be compensated globally. As a result, the use of a packet of single-mode optical fibers makes it possible, compared to the multimode fibers, to propagate short pulses.
    Various publications have described lensless endo-microscopy variants based on the use of a packet of single-mode optical fibers and more specifically of a multi-core fiber or "MCF" according to the English expression "Multi- Core Fiber ". For example, it is shown how one can access, in the distal portion of the packet of optical fibers, a very fast scanning of the focusing point, by printing by means of a galvanometric device a variable angle of the input wavefront. of the SLM (see, for example, ER Andresen et al., Toward endoscopes with no distal optics: video-rate scanning microscopy through a fiber bundle, Opt Lett., Vol 38, No. 5, 609-611 (2013)). In ER Andresen et al ("Two-photon lensless endoscope", Opt.Express 21, No. 18,20713-20721 (2013)), the authors demonstrated the experimental feasibility of a bi-photonic nonlinear imaging system. (TPEF) endo-microscopy without lens. In ER Andresen et al. ("Measurement and compensation of a multi-core fiber for endoscopy", JOSA B, Vol 32, No. 6, 1221-1228 (2015)) describes a device for controlling speed delays. Group (or "GDC" for "Group Delay Control") for the transport and control of light pulses in an endo-microscopic lensless imaging system based on the use of a single-mode optical fiber packet.
    FIG. IA schematically illustrates a lensless endo-microscopic imaging system 100 using a single mode optical fiber packet. The imaging system 100 generally comprises a transmission source 10 for the emission of an incident light beam B 0, continuous or pulsed in the case of the application to nonlinear imaging. The system 100 further comprises a detection channel comprising an objective 21 and a detector 20. The detection path is separated from the emission path by a separating blade 22. The imaging system 100 also comprises a transport device and control of the light beams for illuminating a remote analysis object 101. The transport and control device comprises a packet of monomode optical fibers 40 whose input (or proximal) face 41 and output (or distal face) face 42 are shown in an enlarged view in FIG. 1A, and a spatial modulator. wavefront ("SLM") 30 arranged at the proximal end of the fiber bundle 40 and for controlling the wavefront of the beam emitted by the source 10. The spatial light modulator allows printing on the incoming wavefront, having a phase function Φο, a given phase shift Φι (ΐ) for each elementary beam Bi intended to enter an optical fiber Fi of the fiber packet 40. The phase function Φι (ΐ) may be such that that, for example, after propagation in the packet of optical fibers, the wave exits with a parabolic phase ¢ 2 (1). This parabolic phase allows the beam to focus distally on the analysis object 101 while there is no physical lens present; this is the origin of the terminology "endoscope without lens". Moreover, it is possible thanks to the spatial light modulator to compensate for phase shifts introduced by each of the optical fibers Fi.
    The packet of N monomode optical fibers may be formed of a set of individual single-mode optical fibers, each having a core and a sheath, typically one hundred to a few tens of thousands of fibers, collected in the form of a bundle of fibers; the packet of N monomode optical fibers may also be formed of a set of singlemode cores of a multi-core fiber, preferably at least one hundred single-mode cores, as illustrated in FIG. 1B. Thus, in the example of FIG. IB, a multi-core fiber 40 is shown which comprises a set of single-mode cores Fi, an outer sheath 43 and also in this example a multimode internal sheath 44 adapted to collect the light signal backscattered by the analysis object from the distal end to the proximal end.
    Most often, for questions of method of manufacturing the packet of optical fibers, either in the case of a package consisting of a set of individual single-mode fibers or a set of singlemode cores of a multi-fiber fiber. In the cores, monomode fibers are arranged periodically or quasi-periodically within the fiber packet.
    In the case of a periodic or quasi-periodic arrangement of the cores, the applicants have shown that a wave with a parabolic phase ¢ 2 (1) will result in a given image plane, not in a single image point but rather, as this is shown that FIG. IC, at a shining luminous central point (Pi) surrounded by light points (Ri) of lower intensity, called "replicas". This effect results directly from the periodicity or quasi-periodicity of the arrangement of the optical fibers in the fiber packet which behaves like a diffraction grating, the replicas resulting from the diffraction at higher orders of the wave propagating in the packet of optical fibers.
    The present invention provides devices and methods for transporting and controlling light beams for so-called "lensless" endo-microscopic imaging systems that make it possible to dispense with replicas in the image plane, whatever the arrangement of the fibers. optics within the fiber optic packet.
    SUMMARY OF THE INVENTION
    According to a first aspect, the present disclosure relates to a light beam transport and control device for endo-microscopic lensless imaging comprising: a first light guide comprising a packet of monomode optical fibers, each single mode optical fiber being intended for receiving an elementary light beam at a proximal end and emitting a light beam at a distal end, a second light guide comprising a multimode optical fiber section, arranged at the distal end of the first light guide, the fiber optic section multimode means for receiving the light beams emitted by the monomode optical fibers of the single mode optical fiber packet; an optical phase control device arranged on the side of the proximal end of the first light guide comprising: - at least one first spatial light modulator adapted for the application of a phase shift on each of the elementary beams; - Control means of the first spatial light modulator allowing the application of a phase shift on each of the elementary beams to form at the distal end of the multimode optical fiber section an illumination beam with a specific phase function.
    Applicants have shown that a light beam transport and control device thus described allows the transport of light beams over long distances, typically greater than 100 cm, without consequence due to a possible torsion of the optical fiber packet, and with suppression of replicas. This effect is achieved by the arrangement at the distal end of the single-mode optical fiber packet of a multimode optical fiber section.
    According to one or more exemplary embodiments, the multimode optical fiber section has a length of between 0.1 mm and 20 mm, advantageously between 0.1 and 10 mm. The section of multimode optical fiber is then short enough to be ultra rigid and long enough to allow scrambling of the higher diffiac orders at the output of the packet of monomode optical fibers.
    According to one or more exemplary embodiments, the multimode optical fiber is an index jump fiber, which allows a scrambling of the higher diffiace orders at the output of the monomode optical fiber packet over a very short length segment, for example between 0 , 1 mm and 5 mm.
    According to one or more exemplary embodiments, the multimode optical fiber is a gradient index fiber which requires a longer length to obtain scrambling modes, typically greater than 5 mm.
    According to one or more embodiments, the first light guide comprises a packet of N monomode optical fibers formed of a set of individual single-mode optical fibers, each comprising a core and a sheath, typically one hundred to a few tens of thousands of fibers. , collected in the form of a bundle of fibers.
    According to one or more exemplary embodiments, the first light guide comprises a packet of N monomode optical fibers formed of a set of single-mode cores, preferably at least one hundred. For example, the first light guide is a multi-core fiber and the packet of N single-mode optical fibers is formed by single-mode cores of the multi-core fiber.
    According to one or more exemplary embodiments, the first light guide is a double-sheath multi-core fiber; such a multi-core fiber has the advantage of transporting with great efficiency the backscattered light signal in a sheath of the multi-core double-sheath fiber, generally a multimode sheath.
    By monomode optical fiber is meant a fiber in which light can propagate only in a single mode of the electromagnetic field; by extension we also understand a fiber called 'effective monomode' which includes several modes but in which the coupling conditions excite only one mode (usually the fundamental mode) which confines the light during the entire propagation (no leakage to the other modes).
    Throughout the description, the term "monomode optical fiber" can be used to evoke both an individual single-mode optical fiber and a single-mode core of a multi-core fiber.
    According to one or more exemplary embodiments, the coupling between the monomode optical fibers of the single-mode optical fiber packet is less than -20 dB / m, which allows the transport and control of the optical beams over a large length of the fiber packet, while by offering the possibility to compensate for inter-core phase shift effects.
    According to one or more exemplary embodiments, the first spatial light modulator comprises a segmented or diaphragm deformable mirror for reflection operation.
    According to one or more exemplary embodiments, the first spatial light modulator comprises a liquid crystal matrix, for operation in reflection or in transmission.
    According to one or more embodiments, the light beam transport and control device further comprises an optical system adapted to transport the light beams emitted by the single-mode optical fibers from the optical fiber packet to the multimode optical fiber section.
    According to one or more exemplary embodiments, the optical system allows optical conjugation between an output face of the single-mode optical fiber packet and an input face of the multimode optical fiber section.
    According to one or more exemplary embodiments, an output face of the single-mode optical fiber packet and an input face of the multimode optical fiber section are substantially coincidental with two focal planes of said optical system.
    According to one or more exemplary embodiments, an output face of the single-mode optical fiber packet and an input face of the multimode optical fiber section are fused together and form a mechanical splice.
    According to one or more exemplary embodiments, the first light guide comprises a multi-core fiber drawn at a distal end to form a degressive diameter conical section in which the single-mode cores merge to form the multimode fiber section of the second light guide. . In this case, the conical section forms the transition between the single-mode fiber packet and the multimode fiber section.
    According to one or more exemplary embodiments, the light beam transport and control device is suitable for the transport and control of light beams comprising optical pulses and furthermore comprises a device for controlling the group speed delays of the light pulses in the packet of monomode optical fibers.
    According to a second aspect, the present description relates to an endo-microscopic imaging system comprising a light source; a device according to the first aspect for transporting and controlling the light beams emitted by said source to form an illumination beam of an object with a determined phase function; and a detection path for detecting the light reflected back from the object and transmitted through the second light guide and then through the first light guide, from the distal end to the proximal end thereof.
    According to a third aspect, the present disclosure relates to a method for transporting and controlling light beams for endo-microscopic lensless imaging comprising receiving elementary light beams at a proximal end of a packet of N monomode optical fibers. a first light guide, each single-mode optical fiber being intended to receive an elementary light beam and to emit a light beam at a distal end, the reception of the light beams emitted by all the single-mode optical fibers of the optical fiber packet by a multimode core of a section of a multimode optical fiber of a second light guide, arranged at the distal end of the first light guide; applying by means of at least one first spatial light modulator arranged on the side of the proximal end of the first light guide of a phase shift on each of the elementary beams, to form at the distal end of the fiber section optical multimode an illumination beam with a specific phase function.
    According to one or more exemplary embodiments, the method further comprises a prior calibration for determining the phase shift to be applied to each of the elementary beams as a function of the desired phase function for the illumination beam.
    According to one or more exemplary embodiments, the preliminary calibration step comprises the partial or total determination of a transmission matrix of the set formed by the packet of monomode optical fibers and the multimode fiber.
    According to one or more exemplary embodiments, the application of the phase shift on each of the elementary beams aims to register at the distal end of the multimode optical fiber section a specific phase function to form a converging illumination beam at a given distance from an output face of the multimode optical fiber section, making it possible to form a focusing point.
    According to one or more exemplary embodiments, the application of successive phase shifts on each of the elementary beams allows a scanning of the focusing point in a plane at said given distance from the output face of the multimode optical fiber section and / or at different distances the output face of the multimode optical fiber section.
    According to one or more exemplary embodiments, the elementary light beams comprise light pulses. The method may then comprise, according to an exemplary embodiment, the control of the group speed of the light pulses in the single-mode optical fiber packet.
    According to a fourth aspect, the present description relates to an endo-microscopic imaging process without a lens comprising: the emission of light beams; transport and control of the light beams by means of a method according to the third aspect for the illumination of an object by the illumination beam; detection of the light reflected by the object and transmitted through the second light guide and then through the first light guide, from their distal end to their proximal end.
    The light reflected by the object can be of different nature depending on the application; for example, the returned light is the backscattered light, or the light emitted, for example by a fluorescence mechanism.
    BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and characteristics of the invention will appear on reading the description, illustrated by the following figures: FIGS. IA to IC (already described), a block diagram of a so-called "no-lens" endoscope according to the prior art, based on the use of a single-mode fiber packet; an image of an example of multi-core fiber adapted for the implementation of an endoscope of the type described in FIG. 1A and an image illustrating the presence of replicas; FIG. 2, a block diagram illustrating an example of an endo-microscopic lensless imaging system according to the present disclosure; FIGS. 3A-3D, figures illustrating several examples of arrangement of the single-mode optical fiber packet and the multimode optical fiber in a transport and control device according to the present description; FIGS. 4A to 4C, diagrams illustrating steps of an exemplary method of transporting and controlling light beams according to the present disclosure; FIG. 5, a diagram illustrating an example of experimental setup for the validation of a method of transport and control of light beams according to the present description; FIGS. 6A to 6C, respectively a block diagram of an experimental validation made by means of the assembly of FIG. 5 and images obtained; FIG. 7, images obtained by means of the experimental setup of FIG. 5.
    DETAILED DESCRIPTION
    In the figures, the identical elements are indicated by the same references.
    FIG. 2 schematically illustrates an example of a "lensless" endo-microscopic imaging system 200 with a light beam transport and control device according to the present description, adapted for imaging an object referenced 101 in FIG. . 2.
    The endo-microscopic imaging system 200 comprises a light source (not shown in FIG 2) adapted for the emission of light beams B 0 1, the light beams possibly comprising light pulses in the case of an application to the light source. nonlinear imaging. Thus, the light source comprises, for example, a laser source and, if necessary, an optical system for magnifying and collimating the emitted light beams.
    The endo-microscopic imaging system 200 furthermore comprises a device for transporting and controlling the light beams emitted by said light source in order to illuminate the object 101 according to a chosen intensity figure, for example a focusing point. swept into the field, or other shapes, depending on the applications. The device for transporting and controlling the light beams generally comprises a first light guide 40 with a single-mode optical fiber packet, a second light guide 50 with a multimode optical fiber section, the second light guide 50 being arranged at a distal end of the first light guide, and an optical phase control device arranged on the side of a proximal end of the first light guide, comprising in particular a spatial light modulator 30.
    In the remainder of the description, the term "multimode optical fiber" can more simply be used to refer to the multimode optical fiber section. Furthermore, the second light guide may be formed by the multimode optical fiber section or comprise other elements, for example protection elements, known to those skilled in the art.
    The single-mode optical fiber packet may be formed of a set of individual single-mode optical fibers, typically from one hundred to a few tens of thousands of fibers, assembled as a bundle of fibers, or may comprise a set of singlemode cores. a multi-core fiber, preferably at least one hundred.
    Thus, the first light guide can be formed from the set of individual single-mode optical fibers or comprise other elements, for example protection elements, known to those skilled in the art. The first light guide may also comprise a single-jacketed or double-jacketed multi-core fiber, and may include any other element useful for producing the guide, such as protection elements, in a manner known to those skilled in the art. In the case of a multi-core double-sheath fiber, a sheath may be a multimode sheath adapted to the propagation of the light flux backscattered by the object.
    Advantageously, the coupling between the monomode optical fibers of the single-mode optical fiber packet is less than -20 dB / m, which allows the transport and the control of the optical beams over a large length of the fiber packet, while offering the possibility of compensating inter-heart phase shift effects.
    The length of the monomode fibers of the fiber bundle 40 is adapted to the application and more precisely to the length required for the endomicroscope. Typically, the length of the monomode fibers of the fiber bundle is between 50 cm and 3 m.
    On the contrary, the multimode optical fiber section is advantageously chosen as short as possible, and for example has a length of between 0.1 mm and 20 mm, advantageously between 0.1 mm and 10 mm. The multimode optical fiber section is then short enough to be sufficiently rigid and long enough to allow scrambling of the propagation mode phase at the output of the packet of monomode optical fibers.
    The multimode optical fiber may be, for example, a gradient index fiber or an index jump fiber; in the latter case, the scrambling of the phase of propagation modes at the output of the packet of monomode optical fibers can be obtained by means of a very short section of length, typically between 0.1 mm and 5 mm.
    The section of multimode optical fiber may also be intended to form a permanent implant in the case of applications for example endoscopic imaging of the deep brain. In the latter case, a longer multimode fiber section may be of interest and therefore the use of index gradient multimode fiber may be appropriate.
    The optical phase control device is arranged on the proximal end side of the single-mode optical fiber packet and comprises the spatial light modulator 30 adapted for the application of a phase shift on each of the Boi elementary light beams and a unit control 60 of the spatial light modulator allowing the application of a phase shift on each of the elementary beams for the registration at the distal end of the multimode optical fiber of a specific phase function. The spatial light modulator 30 may comprise, for example, a segmented or membrane deformable mirror, for reflection operation, or a liquid crystal matrix, for reflection or transmission operation.
    According to an exemplary embodiment, the imaging system 200 may also comprise means (not shown in FIG 2) for focusing the elementary light beams B 0 1 on elements 30 i of the spatial light modulator 30. The means for focusing the beams Boi elementary luminaires comprise for example a microlens array or a spatial light modulator, for example a liquid crystal matrix forming a two-dimensional tessellation of gratings having quadratic phases, thereby simulating a microlens array.
    The endo-microscopic imaging system 200 also includes a light detection path backscattered by the object 101 and transmitted through the multimode fiber and the monomode optical fiber packet from their distal end to their proximal end. In the example of FIG. 2, the detection path comprises a beam splitter plate 22, a detector 20 and optionally a lens (not shown in FIG 2) for focusing the backscattered light onto a detection surface of the detector 20, as well as a detector unit. processing (not shown) of the signals from the detector 20.
    FIGS. 3A to 3D illustrate several examples of arrangement of the packet of monomode optical fibers and the multimode optical fiber, making it possible to facilitate the transport of the light beams emitted by the single-mode optical fiber packet to the multimode core of the multimode optical fiber.
    In the example of FIG. 3A, the output face 42 (or distal face) of the monomode optical fiber packet 40 is kept in contact with an input face 51 (or proximal face) of the multimode optical fiber 50. This is for example a direct solder between the packet of monomode optical fibers 40 and the multimode optical fiber 50, or any optical bonding technique ensuring good light transmission between the monomode optical fibers and the multimode fiber.
    In the examples of FIGs. 3B and 3C, an optical system, respectively referenced 71 and 72 in each of the figures, is arranged between the single-mode optical fiber packet 40 and the multimode optical fiber for transporting the light beams emitted by the single-mode optical fibers of the optical fiber packet to the multimode core of the multimode optical fiber section 50.
    For example, as illustrated in FIG. 3B, the optical system 71 allows optical conjugation between the output face 42 of the single-mode optical fiber packet and the input face 51 of the multimode optical fiber section.
    In another example, as illustrated in FIG. 3C, the output face 42 of the single-mode optical fiber packet and the input face 51 of the multimode optical fiber section are substantially coincidental with two focal planes of the optical system 72.
    In these two cases, the adjustment of the optical system 71 or of the optical system 72 does not need to be perfect, the aim being to facilitate the transport of the light beams emitted by the single-mode optical fibers from the optical fiber packet to the multimode core of the section of multimode optical fiber.
    FIG. 3D shows a particular example in which the first light guide comprises a multi-core fiber 40 stretched (or "tapered" according to the English expression) at a distal end to form a conical section degressive diameter. In this conical section where single-mode cores fuse, the propagation becomes multimode as has been described for example in the article by TA Birks et al. ("The photonic lantern", Advances in Optics and Photonics 7, 107-167 (2015)); this gives the multimode fiber section 50 of the second light guide. In this case, the conical section forms the transition between the single-mode fiber packet 40 and the multimode fiber section 50. The assembly has a common sheath 53.
    FIG. 4A illustrates in more detail the steps of an example of a method for transporting and controlling light beams according to the present description, and FIGS. 4B and 4C steps of an example of prior calibration.
    In the example chosen to illustrate the method of transport and control of the light beams, an optical system 72, for example a lens, allows the transport of the light beams emitted by the single-mode optical fibers of the packet of optical fibers 40 to the section of light. multimode optical fiber 50, as illustrated for example in FIG. 3C. In this example, the output face 42 of the single-mode optical fiber packet and the input face 51 of the multimode optical fiber section are substantially coincidental with two focal planes or "Fourier planes" of the optical system 72.
    As illustrated in FIG. 4A, elementary light beams Bu whose phase can be controlled by means of the spatial light modulator 30 (not shown in FIG 4A) are sent on each of the monomode fibers Fi of the fiber packet 40. Each monomode fiber Fi then emits a light beam B2i resulting from the transmission of the light beam Bu through the monomode fiber Fi. The set of light beams B2 1 are located on the output face 42 of the monomode optical fiber packet 40 in the real space (x, y) to form a set N of discrete input modes i, each associated with a fiber Fi, and whose intensities are illustrated in the image L of FIG. 4A. Since the output face 42 of the single-mode optical fiber packet and the input face 51 of the multimode optical fiber section are in Fourier planes of the optical system 72, at each input mode i identified by its actual coordinates (xi, yi) corresponds to an intermediate mode j identified by an input direction (kxj, kyj) in the plane of the input face of the multimode fiber 50. The intensities of the N intermediate modes j are illustrated in the image I2 of FIG. 4A. The multimode fiber is characterized by a given number of eigenmodes, otherwise known as eigenmodes. In practice, N superimpositions (or linear combinations) of eigen modes are addressed, N corresponding to the number of monomode fibers indexed by i; each superposition consisting of a subset of the eigen modes of the multimode fiber.
    Is called output mode u the distribution of the electromagnetic field at the output of the multimode fiber 50. It is sought by means of the method according to the present description to form at the output of the multimode core of the multimode fiber section 50 the output mode u to form the illumination beam having the phase function and / or the associated desired intensity function.
    For example, as illustrated in FIG. 4A, the phase function is determined to form a convergent beam B3 to form a focus point in a plane at a distance z from the output face 52 of the multimode fiber section 50. The image I3 in FIG. 4A illustrates the intensities of output modes u corresponding to different focusing points that can be successively addressed during a scan. Other forms of illumination beams may be sought depending on the application. In the case of brain imaging for example, we can look for an illumination beam whose shape corresponds to that of the elements (neurons) that we want to image.
    The knowledge of the phase shifts to be applied to the elementary light beams Bu results from a prior characterization of the single-mode optical fiber packet and the multimode fiber section.
    For example, it is possible to experimentally determine a total or partial complex transmission matrix of the set formed by the single-mode optical fiber packet and the multimode fiber section. A complex transmission matrix of an optical system makes it possible to express generally the amplitude and the phase of the light field in a given plane at the output of the optical system as a function of the amplitude and the phase of the light field in an input plane. of the optical system. Thanks to the knowledge of the transmission matrix, it is possible to characterize the system formed of the entire packet of monomode optical fibers and the multimode fiber section in order to determine the phase shift to be applied to each of the elementary light beams Bu.
    Thus, it is possible to define a complex transmission matrix Jp of amplitude Jp and phase p ":
    In practice, the determination of the matrix Jp can be partial and be limited, for example, to determining the matrix p "which essentially controls the distribution of intensity in the plane of the object (the amplitude jp playing a marginal role). It is also possible to determine the matrix Jp. incompletely, but this may lead to a lower accuracy on the desired phase function for the illumination beam.
    For the determination of the matrix Jp of the set formed by the single-mode optical fiber packet and the multimode fiber section, it is possible to use interference methods based on interference measurements between the light wave at the output of the multimode optical fiber and a reference wave. The interference pattern is analyzed for successive phase shifts applied to each of the elementary beams or, equivalently on the reference, which makes it possible to determine the matrix Jp. This type of method is described for example in the article by Cizmar et al. where one seeks to determine the transmission matrix of a multimode optical fiber (see 'Shaping the light transmission through a multimode optical fiber: complex transformation analysis and applications in biophotonics' Opt
    Express 19, 18871-18884 (2011)).
    Since the transmission matrix is determined, it can be recorded in the control unit 60 of the spatial light modulator 30, so that prior calibration is not necessary for each implementation of the imaging method. Alternatively, it is possible before starting a new imaging, to perform a calibration again.
    FIGS. 4B and 4C illustrate a step of prior calibration of the light beam transport and control method according to the present description, based on a characterization of the system formed by the single-mode optical fiber packet and the multimode fiber section, and adapted specifically to the formation of a point of focus, whether or not it is scanned.
    In this example, it is assumed that it is sought to form focusing points at different points of the plane n0bj positioned at a distance z from the output face 52 of the multimode optical fiber, as shown in FIG. 4A. Each focal point corresponds to a convergent beam B3k. In practice, it will seek for example to scan a predetermined object field and thus to vary the phase shifts applied by means of the spatial light modulator 30 on the elementary light beams Bu to obtain the desired scanning of the object field.
    For the implementation of the calibration, a matrix detector, for example a camera, is arranged in the plane of the object n0bj or in a conjugate plane. Each pixel of the camera corresponds to an "output mode" referenced u. the number of output modes u thus corresponds in this example to the number M of pixels of the camera. It is sought to determine the phases Φί to be applied to the elementary light beams Bu to maximize the intensity of each output mode u.
    More precisely, it is possible to define a complex transmission matrix J u linking the N input modes i and the M output modes u:
    the number N of input modes is limited by the number of monomode optical fibers in the fiber packet 40 and the number M of output modes is limited by the number of pixels of the camera.
    As previously explained, the transmission matrix J u complex, amplitude Jp. and live pu:
    In practice, the determination of the matrix J u is to measure only the matrix p "which essentially controls the distribution of intensity in the plane of the object.
    The determination of the matrix p "may comprise the following steps:
    Sending two input modes, a reference mode / = 0 and an input mode / to which it is associated a phase Φ ;
    Recording for each output mode u, i.e. for each pixel of the camera, the resulting intensity for a given number of equidistant washers of <t> h for example 8, between 0 and 2π, as shown in FIG. 4C;
    Recording for each output mode u of phase Φ, which maximizes the intensity (FIG 4B); Reiteration for each input mode i.
    Of course, the calibration steps of the light beam transport and control method described above can also be applied when the single-mode optical fiber packet 40 and the multimode fiber section 50 are arranged differently.
    In particular, if the input face 51 is in the same plane, or in a plane conjugated with the output face 42 of the monomode fiber packet 40, the intermediate plane associated with the input face 51 of the multimode fiber 50 can be indexed in real space (x, y).
    FIG. 5 represents an example of experimental setup implemented for the validation of a method of transport and control of light beams according to the present description.
    The experimental setup comprises a laser source 10 emitting a light beam sent on a "wavefront shaper" 503, for example a matrix of microlenses or a two-dimensional spatial light modulator inscribing a network of quadratic phases simulating a matrix of microlenses, and for forming a set of elementary beams focused on the segments of a segmented deformable mirror 30. A telescope 504, 506 makes it possible to adjust the dimension of the beam in the plane of the deformable mirror 30. Each segment of the deformable mirror 30 is imaged on a single-mode fiber of the single-mode optical fiber packet 40 (imager 508, 513, 515, 516). A control device 60 of the deformable mirror 30 makes it possible to control the phase Φχ associated with each input mode i and corresponding to each of the elementary beams. A focal lens f = 500 μηι (not visible in FIG 5) is placed on the exit face of the fiber pack 40 so that the exit face of the fiber bundle 40 and the entry face of the Multimode fibers 50 are in Fourier planes. The intensity distribution in the plane of the object 101 is observed by means of a CMOS camera 520 comprising M = 4096 pixels and conjugated with the plane of the object 101 by means of in objective 517. The set formed of a half-wave plate 501 and a polarizer 502 makes it possible to adjust the state of polarization so that it coincides with that for which the wavefront shaper 503 is active in the case where this component uses liquid crystals; on the other hand, this arrangement makes it possible to adjust the power sent to the sample 101. A polarizer 518 makes it possible to select a single polarization state for which the transmission matrix is measured and the focusing point in the optimized plane n0bj. A splitter plate 22 allows to send back to a detector 20 the backscattered or emitted light (in the case of fluorescence) by the object and transmitted from the distal side to the proximal side by the multimode fiber section and the first light guide. For example, the detector 20 is a photomultiplier or an avalanche photodiode. When the sample 101 is scanned with a focused beam, the backscattered or emitted signal from each point of the sample is collected by the detector 101 to form an image.
    A calibration of the method of transport and control of the light beams implemented through the experimental setup of FIG. 5 has also been performed to control the positon of a focus point in the field of the object n0bj as shown in the diagram of FIG. 6A. The calibration is performed according to the protocol for determining the transmission matrix described above.
    In the example shown in FIG. 6A, the plane of the object is at a distance z = 250 μm from the output face of the multimode fiber section.
    It is observed in FIG. 6B a focal point in the plane of the object obtained by the device shown in FIG. 5. As can be seen, no replica is apparent. FIG. 6C represents a subset of focusing points corresponding to different output modes u obtained by applying phases Φ, on the elementary luminaires Bu. In practice only one focusing point is visible as shown in FIG. 6B, FIG. 6C shows several points to appreciate the field of view.
    Thus, the applicants have shown both theoretically and experimentally that after a propagation distance in the core of the very short multimode fiber, typically 1 mm or a few millimeters depending on the nature of the fiber, the propagation modes exhibit random phases. This random nature of the phases associated with each mode of propagation of the multimode fiber is at the very origin of the disappearance of the replicas. The relative phase shifts between the modes of the multimode fiber resulting from the propagation makes it clear why an index jump multimode fiber is more efficient than a multimode index gradient fiber for scrambling modes; indeed, in a fiber with index jump, the propagation constants associated with each of the modes are more dispersed, giving rise to larger differential phase shifts.
    Although the phases accumulated by the different modes during propagation in the multimode fiber are finally random, they are nevertheless deterministic and are included in the determination of the transmission matrix including the first light guide and the multimode optical fiber.
    Applicants have thus demonstrated the feasibility of a light beam transport and control device for endo-microscopy without a lens, a function of scanning the field of the object at a given distance z from the exit face 52 of the section of multimode optical fiber 50 obtainable by controlling phase shifts applied by means of the spatial light modulator 30.
    The device for transporting and controlling light beams according to the present description also makes it possible to choose the distance z from the plane of the object. For this, a calibration as described above can be performed for a set of values z of the distance between the plane of the object and the output face 52 of the multimode optical fiber section.
    FIG. 7 thus shows images of fluorescent beads obtained by means of the experimental setup of FIG. And detected by the detector 20, for z values of z = 10 μm (a), z = 40 μm (b), z = 70 μm (c), z = 100 μm (d).
    More precisely, the light source used to obtain these images is a Titanium: Sapphire laser at 800 nm emitting pulses of 200 fs; the images obtained are two-photon images, the detector 20 is an avalanche photodiode.
    These experimental results also demonstrate the application of the method of transport and control of light beams in non-linear imaging, the device being adapted to the transmission of short pulses.
    However, in the case of ultra-short pulse manipulation, the light beam transport and control device according to the present description may also include a device for controlling the light pulse group speed in the single-mode optical fiber packet. as described in the publication of ER Andresen et al. ("Measurement and compensation of a multi-core fiber for lensless endoscopy", JOSAB, Vol 32, No. 6, 1221-1228 (2015)).
    It is thus possible thanks to the method described to perform endoscopic imaging without a lens. In addition to the transport and control of the light beams using the method described above, the endo-microscopic imaging method may include the detection of light backscattered by the object and transmitted through the multimode fiber and the single mode optical fiber packet. from their distal end to their proximal end.
    Although described through a number of detailed exemplary embodiments, the device for transporting and controlling light pulses for so-called "no lens" endo-microscopic imaging as well as endo-microscopic imaging systems and methods. Without a lens there are various variations, modifications and improvements which will become obvious to those skilled in the art, it being understood that these various variants, modifications and improvements are within the scope of the invention as defined by the claims which follow.
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    A light beam transport and control device for endo-microscopic lensless imaging comprising: a first light guide (40) comprising a single mode optical fiber (Fi) packet, each monomode optical fiber (Fi) being intended receiving an elementary light beam (Bu) at a proximal end and emitting a light beam (B2i) at a distal end, a second light guide (50) comprising a multimode optical fiber section, arranged at the distal end of the first light guide, the multimode optical fiber section being intended to receive the light beams (B2i) emitted by all the single-mode optical fibers of the optical fiber packet; an optical phase control device arranged on the proximal end side of the first light guide (40) comprising: at least one first spatial light modulator (30) adapted for applying a phase shift to each of the beams elementary (Bu); programming means (60) of the first spatial light modulator for applying a phase shift to each of the elementary beams (Bu) to form at the distal end of the multimode optical fiber (50) an illumination beam with a defined phase function.
    [2" id="c-fr-0002]
    2. Device for transporting and controlling light pulses according to claim 1, wherein the multimode optical fiber section has a length of between 0.1 mm and 20 mm.
    [3" id="c-fr-0003]
    3. A device for transporting and controlling light pulses according to any one of the preceding claims, further comprising an optical system (71, 72) adapted to transport the light beams emitted by the monomode optical fibers of the packet of optical fibers to the section of multimode optical fiber.
    [4" id="c-fr-0004]
    The light pulse transport and control apparatus according to any one of the preceding claims, wherein the first light guide (40) comprises a double-core multi-core fiber.
    [5" id="c-fr-0005]
    5. Endo-microscopic imaging system comprising: - a light source (10) for the emission of light beams; - A device according to any one of the preceding claims for the transport and control of light beams emitted by said source for the formation of an illumination beam of an object with a specific phase function; and - a detection path (20, 21) for detecting the light reflected by the object and transmitted through the second light guide (50) and then through the first light guide (40), from their end distal at their proximal end.
    [6" id="c-fr-0006]
    A method of transporting and controlling light beams for endo-microscopic lensless imaging comprising: receiving elementary light beams (Bu) at a proximal end of a packet of N monomode optical fibers (Fi) of a first light guide (40), each monomode optical fiber (Fi) being intended to receive an elementary light beam (Bu) and to emit a light beam (B2O at a distal end, the reception of the light beams emitted by all single-mode optical fibers of the optical fiber packet by a multimode core of a section of a multimode optical fiber of a second light guide (50), arranged at the distal end of the first light guide (40); application by means of at least a first spatial light modulator arranged on the side of the proximal end of the first light guide of a phase shift on each of the elementary beams, in order to forming at the distal end of the multimode optical fiber section an illumination beam (B3) with a determined phase function.
    [7" id="c-fr-0007]
    7. The method of claim 6, further comprising a prior calibration for determining the phase shift to be applied to each of the elementary beams (Bu) according to the desired phase function for the illumination beam (B3).
    [8" id="c-fr-0008]
    8. A method according to any one of claims 6 to 7, wherein the application of the phase shift on each of the elementary beams aims to form at the distal end of the multimode optical fiber section (50) an illumination beam converging to a given distance (z) of an output face (52) of the multimode optical fiber section (50) for forming a focus point.
    [9" id="c-fr-0009]
    9. The method of claim 8, wherein the application of successive phase shifts on each of the elementary beams allows a scanning of said focusing point in a plane (Ilobj) at said given distance from the output face of the multimode optical fiber section and or at different distances from the output face of the multimode optical fiber section.
    [10" id="c-fr-0010]
    10. Endo-microscopic imaging process without a lens comprising: the emission of light beams; the transport and control of the light beams by means of a method as described according to any one of claims 6 to 9 for the illumination of an object by the illumination beam (B3); detection of the light reflected by the object and transmitted through the second light guide (50) and then through the first light guide (40), from their distal end to their proximal end.
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1652937A|FR3049719B1|2016-04-04|2016-04-04|DEVICES AND METHODS FOR TRANSPORTING AND CONTROLLING LUMINOUS BEAMS FOR ENDO-MICROSCOPIC IMAGING WITHOUT LENS|
    FR1652937|2016-04-04|FR1652937A| FR3049719B1|2016-04-04|2016-04-04|DEVICES AND METHODS FOR TRANSPORTING AND CONTROLLING LUMINOUS BEAMS FOR ENDO-MICROSCOPIC IMAGING WITHOUT LENS|
    US16/091,200| US20210018744A1|2016-04-04|2017-04-04|Devices and methods for conveying and controlling light beams for lensless endo-microscopic imagery|
    EP17719502.1A| EP3439529A1|2016-04-04|2017-04-04|Devices and methods for conveying and controlling light beams for lensless endo-microscopic imagery|
    PCT/EP2017/058017| WO2017174596A1|2016-04-04|2017-04-04|Devices and methods for conveying and controlling light beams for lensless endo-microscopic imagery|
    JP2019502158A| JP6912555B2|2016-04-04|2017-04-04|Equipment and methods for transmitting and controlling light beams for lensless endoscopic microscope imaging|
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