8 research outputs found

    Matrix approach of Full-Field OCT for volumetric imaging of an opaque human cornea

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    Optical microscopy offers the possibility to image biological tissue with a diffraction limited resolution (~¬Ķm). However, the heterogeneity of biological tissues can strongly affect light propagation at large depths by distorting the initial wavefront. Large and short range fluctuations of the refractive index can induce aberration and multiple scattering, respectively. Inspired by a recent work [1], we have developed a matrix approach to Full-Field Optical Coherence Tomography (FF-OCT) to push back the fundamental limit of aberrations and multiple scattering. Here, we report on the application of this approach to the imaging of the human cornea and the quantitative measurement of the corneal transparency. Please click Additional Files below to see the full abstract

    Multi-Spectral Reflection Matrix for Ultra-Fast 3D Label-Free Microscopy

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    Label-free microscopy exploits light scattering to obtain a three-dimensional image of biological tissues. However, light propagation is affected by aberrations and multiple scattering, which drastically degrade the image quality and limit the penetration depth. Multi-conjugate adaptive optics and time-gated matrix approaches have been developed to compensate for aberrations but the associated frame rate is extremely limited for 3D imaging. Here we develop a multi-spectral matrix approach to solve these fundamental problems. Based on an interferometric measurement of a polychromatic reflection matrix, the focusing process can be optimized in post-processing at any voxel by addressing independently each frequency component of the wave-field. A proof-of-concept experiment demonstrates the three-dimensional image of an opaque human cornea over a 0.1 mm^3-field-of-view at a 290 nm-resolution and a 1 Hz-frame rate. This work paves the way towards a fully-digital microscope allowing real-time, in-vivo, quantitative and deep inspection of tissues.Comment: 27 pages, 4 figure

    Approche matricielle de la tomographie à cohérence optique

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    Interferometric techniques of microscopy display sensitivity to aberrations affecting both resolution and depth of imaging. Formerly introduced in astronomy, different methods of adaptive optics have been applied to microscopy in order to compensate for these effects. Most of them rely on the measurement of the wave front and on a close-loop correction of the aberrations using wave-front control devices. These methods are nevertheless limited by the rates of measurement and correction and can only compensate for low-order aberrations.The purpose of this thesis is to present an innovative matrix approach relying on the analysis of a new operator, the distorsion matrix, allowing to locally quantify the scattering and aberration parameters, and to compensate for the aberrations over the whole field of view. Besides, we introduce a mathematical formalism in order to describe the effects of aberrations in full-field OCT and we extend the scope of the matrix approach to very large fields of view thanks to an experimental setup of reflection matrix measurement inspired by this technique of imaging.Les techniques de microscopie interf√©rom√©trique pr√©sentent une sensibilit√© aux aberrations qui limite leurs pouvoirs de r√©solution et de p√©n√©tration. Initialement d√©velopp√©es en astronomie, des m√©thodes d'optique adaptative ont √©t√© transpos√©es en microscopie afin de compenser les effets dues aux aberrations. Celles-ci reposent principalement sur la mesure du front d'onde et sur la correction en boucle ferm√©e des aberrations √† l'aide de dispositifs de contr√īle du front d'onde. Ces m√©thodes sont toutefois limit√©es par les cadences de mesure et de correction, et ne peuvent compenser que des aberrations d'ordres peu √©lev√©s.L'objectif de cette th√®se est de proposer une approche matricielle innovante reposant sur l'√©tude d'un nouvel op√©rateur, la matrice distorsion, permettant de quantifier localement les param√®tres li√©s aux aberrations et √† la diffusion, et de corriger les aberrations sur l'ensemble du champs de vision. En parall√®le, nous pr√©sentons un formalisme math√©matique permettant d'expliquer la manifestation des aberrations en OCT plein champ et √©tendons le champ d'application de la m√©thode matricielle √† de vastes champs de vision au moyen d'un dispositif exp√©rimental de mesure de la matrice de r√©flexion inspir√© de cette technique d'imagerie

    Matrix approach for optical coherence tomography

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    Les techniques de microscopie interf√©rom√©trique pr√©sentent une sensibilit√© aux aberrations qui limite leurs pouvoirs de r√©solution et de p√©n√©tration. Initialement d√©velopp√©es en astronomie, des m√©thodes d'optique adaptative ont √©t√© transpos√©es en microscopie afin de compenser les effets dues aux aberrations. Celles-ci reposent principalement sur la mesure du front d'onde et sur la correction en boucle ferm√©e des aberrations √† l'aide de dispositifs de contr√īle du front d'onde. Ces m√©thodes sont toutefois limit√©es par les cadences de mesure et de correction, et ne peuvent compenser que des aberrations d'ordres peu √©lev√©s.L'objectif de cette th√®se est de proposer une approche matricielle innovante reposant sur l'√©tude d'un nouvel op√©rateur, la matrice distorsion, permettant de quantifier localement les param√®tres li√©s aux aberrations et √† la diffusion, et de corriger les aberrations sur l'ensemble du champs de vision. En parall√®le, nous pr√©sentons un formalisme math√©matique permettant d'expliquer la manifestation des aberrations en OCT plein champ et √©tendons le champ d'application de la m√©thode matricielle √† de vastes champs de vision au moyen d'un dispositif exp√©rimental de mesure de la matrice de r√©flexion inspir√© de cette technique d'imagerie.Interferometric techniques of microscopy display sensitivity to aberrations affecting both resolution and depth of imaging. Formerly introduced in astronomy, different methods of adaptive optics have been applied to microscopy in order to compensate for these effects. Most of them rely on the measurement of the wave front and on a close-loop correction of the aberrations using wave-front control devices. These methods are nevertheless limited by the rates of measurement and correction and can only compensate for low-order aberrations.The purpose of this thesis is to present an innovative matrix approach relying on the analysis of a new operator, the distorsion matrix, allowing to locally quantify the scattering and aberration parameters, and to compensate for the aberrations over the whole field of view. Besides, we introduce a mathematical formalism in order to describe the effects of aberrations in full-field OCT and we extend the scope of the matrix approach to very large fields of view thanks to an experimental setup of reflection matrix measurement inspired by this technique of imaging

    Distortion matrix concept for deep imaging in optical coherence microscopy

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    33 pages, 8 figuresIn optical imaging, light propagation is affected by the inhomogeneities of the medium. Sample-induced aberrations and multiple scattering can strongly degrade the image resolution and contrast. Based on a dynamic correction of the incident and/or reflected wave-fronts, adaptive optics has been employed to compensate for those aberrations. However, it mainly applies to spatially-invariant aberrations or to thin aberrating layers. Here, we propose a global and non-invasive approach based on the distortion matrix concept. This matrix basically connects any focusing point of the image with the distorted part of its wave-front in reflection. A time-reversal and entropy analysis of the distortion matrix allows to correct for high-order aberrations and forward multiple scattering over multiple isoplanatic areas. Proof-of-concept experiments are performed through biological tissues and an opaque cornea. We demonstrate a Strehl ratio enhancement up to 2500 and recover a diffraction-limited resolution until a depth of ten scattering mean free paths

    Distortion matrix concept for deep optical imaging in scattering media

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    International audienceIn optical imaging, light propagation is affected by the inhomogeneities of the medium. Sample-induced aberrations and multiple scattering can strongly degrade the image resolution and contrast. On the basis of a dynamic correction of the incident and/or reflected wavefronts, adaptive optics has been used to compensate for those aberrations. However, it only applies to spatially invariant aberrations or to thin aberrating layers. Here, we propose a global and noninvasive approach based on the distortion matrix concept. This matrix basically connects any focusing point of the image with the distorted part of its wavefront in reflection. A singular value decomposition of the distortion matrix allows to correct for high-order aberrations and forward multiple scattering over multiple isoplanatic modes. Proof-of-concept experiments are performed through biological tissues including a turbid cornea. We demonstrate a Strehl ratio enhancement up to 2500 and recover a diffraction-limited resolution until a depth of 10 scattering mean free paths

    Distortion matrix concept for deep imaging in optical coherence microscopy

    No full text
    33 pages, 8 figuresIn optical imaging, light propagation is affected by the inhomogeneities of the medium. Sample-induced aberrations and multiple scattering can strongly degrade the image resolution and contrast. Based on a dynamic correction of the incident and/or reflected wave-fronts, adaptive optics has been employed to compensate for those aberrations. However, it mainly applies to spatially-invariant aberrations or to thin aberrating layers. Here, we propose a global and non-invasive approach based on the distortion matrix concept. This matrix basically connects any focusing point of the image with the distorted part of its wave-front in reflection. A time-reversal and entropy analysis of the distortion matrix allows to correct for high-order aberrations and forward multiple scattering over multiple isoplanatic areas. Proof-of-concept experiments are performed through biological tissues and an opaque cornea. We demonstrate a Strehl ratio enhancement up to 2500 and recover a diffraction-limited resolution until a depth of ten scattering mean free paths
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