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Environmental enteric dysfunction (EED) is a disease of the small intestine affecting children and adults in low and middle income countries. Arising as a consequence of repeated infections, gut inflammation results in impaired intestinal absorptive and barrier function, leading to poor nutrient uptake and ultimately to stunting and other developmental limitations. Progress towards new biomarkers and interventions for EED is hampered by the practical and ethical difficulties of cross-validation with the gold standard of biopsy and histology. Optical biopsy techniques - which can provide minimally invasive or noninvasive alternatives to biopsy - could offer other routes to validation and could potentially be used as point-of-care tests among the general population. This Consensus Statement identifies and reviews the most promising candidate optical biopsy technologies for applications in EED, critically assesses them against criteria identified for successful deployment in developing world settings, and proposes further lines of enquiry. Importantly, many of the techniques discussed could also be adapted to monitor the impaired intestinal barrier in other settings such as IBD, autoimmune enteropathies, coeliac disease, graft-versus-host disease, small intestinal transplantation or critical care.

The DIAPRECA project is aimed at exploiting conjointly or consecutively optical microscopy exploration techniques such as reflectance and Raman in a perspective of a better early and in vivo discrimination between healthy, precancerous and cancerous tissues. DIAPRECA brings together the laboratories LTSI-INSERM U 642, ProCadec-CNRS 6164, IGDR-CNRS 6061 of the university of Rennes 1, the service of gastroenterology university hospital of Brest and the company Mauna Kea Technologies. This project covered both aspects of dedicated instrument and software design and ex vivo and in vivo experiments.

We describe a fluorescence lifetime imaging endomicroscope employing a fibre bundle probe and time correlated single photon counting. Preliminary images of stained pollen grains, eGFP-labelled cells exhibiting Förster resonant energy transfer and tissue autofluorescence are presented.

With the increasing maturity of optical biopsy techniques, routine clinical use has become more widespread. This wider adoption of the technique demands effective tracking and retargeting of the biopsy sites, as no visible markers are left following examination. This study presents a high-speed framework for intra-procedural retargeting of probe-based optical biopsies in gastrointestinal endoscopy. A probe tip localisation method using active shape models and geometric heuristics, which eliminates the traditional dependency on shaft visibility, is proposed for automated initialisation. Partial occlusion and tissue deformation are addressed by exploiting the benefits of indirect and direct tracking through a novel combination of geometric association and online learning. Robustness to rapid endoscope motion and improvements in computational efficiency are achieved by restricting processing to the automatically detected video content area and through a feature-based rejection of non-informative frames. Performance evaluation in phantom and in-vivo environments demonstrates accurate biopsy site initialisation, robust retargeting and significant improvements over the state-of-the-art in processing time and memory usage.

International audience; Probe-based Confocal Laser Endomicroscopy (pCLE) provides physicians with real-time access to histological information during standard endoscopy procedures, through high-resolution cellular imaging of internal tissues. Earlier work on mosaicing has enhanced the potential of this imaging modality by meeting the need to get a complete representation of the imaged region. However, with approaches, the dynamic information, which may be of clinical interest, is lost. In this study, we propose a new mosaic construction algorithm for pCLE sequences based on a min-cut optimization and gradient-domain composition. Its main advantage is that the motion of some structures within the tissue such as blood cells in capillaries, is taken into account. This allows physicians to get both a sharper static representation and a dynamic representation of the imaged tissue. Results on 16 sequences acquired in vivo on six different organs demonstrate the clinical relevance of our approach.

An on-line estimation of turbulence parameters (r0, L0 and wind speed) and adaptive optics (AO) performance is presented. The method is based on the reconstruction of open-loop data from deformable mirror voltages and residual wavefront sensor slopes obtained in closed loop. This dedicated tool implemented in the real time computer of the NAOS (Nasmyth adaptive optics system) system (first AO of the very large telescope) allows us without any loop opening to automatically monitor and display (every 15 s) both the atmospheric conditions and the system performance. We have validated the algorithm and tested its robustness on simulated and experimental data (both in the laboratory and on sky). Using data obtained over more than one year (from January 2002 to June 2003), a statistical study on NAOS performance and turbulence characteristics is proposed.

NAOS is the first adaptive optics (AO) system of the Very Large Telescope and will provide CONICA with diffraction-limited images. CONICA is a near infrared camera that offers a variety of imaging and spectroscopic observing modes. A technique will be described to benefit of the AO system to correct not only for atmospheric turbulence but also for the internal optical aberrations of the high-resolution camera and the beam splitters of NAOS. The aberrant optical components in the light path of CONICA as well as the beam splitters are outside of the AO loop and therefore no self-acting correction is possible. Independently of the AO wavefront sensor, a separate measurement of these aberrations using a method called phase diversity allows one to predict for a certain instrument configuration the corresponding aberrations. They are quantified by sets of Zernike coefficients that are rendered to the adaptive optics. This technique turns out to be very flexible and results in a further improvement of the optical overall performance. The application of phase diversity to the instrument is investigated in a preceding paper (Blanc et al. 2003). In the present paper we present in detail the instrumental implementation of phase diversity, the obtained calibration results, and the achieved gain in optical performance.

Three‐dimensional spectroscopy has the advantage of providing (quasi‐) simultaneously both spatial and spectral information. Coupled to adaptive optics, it conjugates spectroscopic power with high angular resolution. GriF offers these capabilities in the near‐infrared. As a new observing mode of KIR, the camera behind PUEO, the Canada‐France‐Hawaii Telescope adaptive optics bonnette, it provides images at the diffraction limit of the telescope in the K band. Spectroscopy at a resolution of 2000 is provided by a Fabry‐Perot interferometer coupled with a grism, cooled to limit the background. This setup offers a large multiplex gain by observing simultaneously up to five monochromatic images. This article first describes the instrument and the calibration procedures. Next, we demonstrate GriF performances from its first observations, obtained on the Orion molecular cloud OMC‐1.

A new 1-5 μm high-resolution camera dedicated to the ESO adaptive optics system ADONIS has been developed as a collaborative project of Observatoire de Paris-Meudon and Observatoire de Grenoble, under ESO contract. Since this camera has been designed to correctly sample the diffraction, two focal plate scales are available: 36 mas pixel–1 for the 1-2.5 μm range and 100 mas pixel–1 for the 3-5 μm range, yielding fields of view of and , respectively. Several broadband and narrowband filters are available as well as two circular variable filters, allowing low spectral resolution (R ~ 60-120) imagery between 1.2 and 4.8 μm. This camera is equipped with a 128 × 128 HgCdTe/CCD array detector built by the CEA-LETI-LIR (Grenoble, France). Among its main characteristics, this detector offers a remarkably high storage capacity (more than 106 electrons) with a total system readout noise of ≈1000 electrons rms, making it particularly well suited for long integration time imagery in the 3-5 μm range of the near-infrared domain. The measured dark current is 2000 electrons s–1 pixel–1 at the regular operating temperature of 77 K, allowing long exposure times at short wavelengths (λ 3 μm), the performances are background-noise limited. We have estimated the ADONIS + COMIC imaging performances using a method specially dedicated to high angular resolution cameras.

Since its inception in the field of in vivo imaging, endomicroscopy through optical fiber bundles, or probe-based Confocal Laser Endomicroscopy (pCLE), has extensively proven the benefit of in situ and real-time examination of living tissues at the microscopic scale. By continuously increasing image quality, reducing invasiveness and improving system ergonomics, Mauna Kea Technologies has turned pCLE not only into an irreplaceable research instrument for small animal imaging, but also into an accurate clinical decision making tool with applications as diverse as gastrointestinal endoscopy, pulmonology and urology. The current implementation of pCLE relies on a single fluorescence spectral band making different sources of in vivo information challenging to distinguish. Extending the pCLE approach to multi-color endomicroscopy therefore appears as a natural plan. Coupling simultaneous multi-laser excitation with minimally invasive, microscopic resolution, thin and flexible optics, allows the fusion of complementary and valuable biological information, thus paving the way to a combination of morphological and functional imaging. This paper will detail the architecture of a new system, Cellvizio Dual Band, capable of video rate in vivo and in situ multi-spectral fluorescence imaging with a microscopic resolution. In its standard configuration, the system simultaneously operates at 488 and 660 nm, where it automatically performs the necessary spectral, photometric and geometric calibrations to provide unambiguously co-registered images in real-time. The main hardware and software features, including calibration procedures and sub-micron registration algorithms, will be presented as well as a panorama of its current applications, illustrated with recent results in the field of pre-clinical imaging.

International audience; This work deals with label free multiphoton imaging of the human lung tissue extra-cellular matrix (ECM) through optical fibers. Two devices were developed, the first one using distal scanning associated to a double clad large mode area (LMA) air-silica microstructured fiber, the second one using proximal scanning of a miniature multicore image guide (30000 cores inside a 0.8 mm diameter). In both cases, the main issue has been efficient linear and nonlinear distortion pre-compensation of excitation pulses. By inserting before the delivery fiber a compact (10 cm × 10 cm footprint) grisms-based stretcher (a grating in close contact with a prism) made of readily available commercial components, we achieved as short as 35-femtosecond-duration pulses that were temporally compressed at the direct exit of a 2-meter-long fiber. Interestingly, this femtosecond pulse fiber delivery device is also wavelength tunable over more than 100 nm inside the Ti: Sapphire emission band. With the help of distal scan system, those unique features allowed us to record elastin (through two-photon fluorescence) and collagen (through second harmonic generation) fibered network images. These images were obtained ex-vivo with only 15 mW @ 80 MHz of IR radiation delivered to the alveoli or bronchus tissues. 3D imaging with 400-μm-penetration depth inside the tissue was possible working with a 2-meter-long LMA fiber. With the help of proximal scanning, the miniature image guide allowed us to perform endoscopic real time microimaging of the ECM ex vivo. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

International audience; Retinal pathologies, like ARMD or glaucoma, need to be early detected, requiring imaging instruments with resolution at a cellular scale. However, in vivo retinal cells studies and early diagnoses are severely limited by the lack of resolution on eye-fundus images from classical ophthalmologic instruments. We built a 2D retina imager using Adaptive Optics to improve lateral resolution. This imager is currently used in clinical environment. We are currently developing a time domain full-field optical coherence tomograph. The first step was to conceive the images reconstruction algorithms and validation was realized on non-biological samples. Ex vivo retina are currently being imaged. The final step will consist in coupling both setups to acquire high resolution retina cross-sections.

International audience; High resolution wide-field imaging of the human retina calls for a 3D deconvolution. In this communication, we report on a regularized 3D deconvolution method, developed in a Bayesian framework in view of retinal imaging, which is fully unsupervised, i.e., in which all the usual tuning parameters, a.k.a. "hyper-parameters", are estimated from the data. The hyper-parameters are the noise level and all the parameters of a suitably chosen model for the object's power spectral density (PSD). They are estimated by a maximum likelihood (ML) method prior to the deconvolution itself. This 3D deconvolution method takes into account the 3D nature of the imaging process, can take into account the non-homogeneous noise variance due to the mixture of photon and detector noises, and can enforce a positivity constraint on the recovered object. The performance of the ML hyper-parameter estimation and of the deconvolution are illustrated both on simulated 3D retinal images and on non-biological 3D experimental data.

International audience; We describe here two parts of our future 3D fundus camera coupling Adaptive Optics and full-field Optical Coherence Tomography. The first part is an Adaptive Optics flood imager installed at the Quinze-Vingts Hospital, regularly used on healthy and pathological eyes. A posteriori image reconstruction is performed, increasing the final image quality and field of view. The instrument lateral resolution is better than 2 microns. The second part is a full-field Optical Coherence Tomograph, which has demonstrated capability of performing a simple kind of "4 phases" image reconstruction of non biological samples and ex situ retinas. Final aim is to couple both parts in order to achieve 3D high resolution mapping of in vivo retinas.

Confocal endomicroscopy provides tools for in vivo imaging of human cell architecture endoscopically. These technologies are a tough challenge since multiple trade-offs have to be overcome: resolution versus field of view, dynamic versus stability, contrast versus low laser power or low contrast agent doses. Many difficult clinical applications, such as lung, bile duct, urethral imaging and NOTES applications, need to optimize miniaturization, resolution, frame rate and contrast agent dose simultaneously. We propose one solution based on real-time video image processing to efficiently address these trade-offs. Dynamic imaging provides a flow of images that we process in real time. Images are aligned using efficientalgorithms specifically adapted to confocal devices. From the displacement that we find across the images, instantaneous velocities are computed and used to compensate for motion distortions. All images are stitched together onto the same reference space and displayed in real-time to reconstruct an image of the entire surface explored during the clinical procedure. This representation brings both stability and an increased field of view. Moreover, because a given area can be imaged by several frames, the contrast can be improved using temporal adaptive averaging. Such processing enhances the visualization of the video sequence, overcoming most classical trade-offs. The stability and increased field of view help the clinician better focus his attention on his practice which improves the patient benefit. Our tools are currently evaluated in a multicenter clinical trial to assess the improvement of the clinical practice.

A flexible multicore fiber bundle is fed by temporally and spectrally shaped femtosecond pulses allowing for the pre-compensation of both chromatic dispersion and non-linear effects encountered in the bundle. We demonstrate that the pulse duration at the fiber bundle output can be significantly reduced in comparison with linear pre-compensation only. The scheme for femtosecond pulse fiber delivery is applied to the optimization of two-photon fluorescence (TPF) imaging. Experiments and calculations show a five-fold improvement of the TPF signal produced at the end of the fiber bundle in comparison with linear pre-compensation. This is applied to the recording, in real time (12 image/s), of TPF laser-scanning images of human colon cells stained with a fluorescent marker. Further optimizations are discussed.

3D deconvolution is an established technique in microscopy that may be useful for low-cost high-resolution imaging of the retina. We report on a myopic 3D deconvolution method developed in a Bayesian framework. This method uses a 3D imaging model, a noise model that accounts for both photon and detector noises, a regularization term that is appropriate for objects that are a mix of sharp edges and smooth areas, a positivity constraint, and a smart parameterization of the point-spread function (PSF) by the pupil phase. It estimates the object and the PSF jointly. The PSF parameterization through the pupil phase constrains the inversion by dramatically reducing the number of unknowns. The joint deconvolution is further constrained by an additional longitudinal support constraint derived from a 3D interpretation of the phase-diversity technique. This method is validated by simulated retinal images.

Confocal fluorescence high resolution imaging during standard endoscopic procedures has been presented as a very promising tool to enhance patient care and physician practice by providing supplementary diagnostic information in real-time. The purpose of this paper is to show not only potential, but convincing results of endoscopic microscopy using a catheter-based approach. Mauna Kea Technologies' core technology, Cellvizio, delivers dynamic imaging at 12 frames/second using confocal miniprobes inserted through the operating channel of regular endoscopes. Cellvizio is composed of 3 parts including (a) a Laser Scanning Unit, (b) Confocal Miniprobe TM with the following characteristics: 5-15 mm axial resolution, 2-5 mm lateral resolution, 15-100 mm depth of penetration, field of view of 600x500 mm and (c) a software package with onthe- fly processing capabilities. With several tens of patients examined during routine GI endoscopy procedures, the most relevant clinical parameters could be assessed in a doubled-blinded fashion between the endoscopist and a pathologist and results showing very high accuracy in the differentiation of neoplasia from normal and hyperplastic tissue were obtained. In the field of pulmonology, the micro-autofluorescence properties of tissues could be assessed and structures never before accessed in vivo were observed. Cellvizio® may be useful to study bronchial remodeling in asthma and chronic obstructive pulmonary diseases. Using appropriate topical fluorescent dye, the Confocal Miniprobes may also make it possible to perform optical biopsy of precancerous and superficial bronchial cancers. Cellvizio® is as a new tool towards "targeted biopsies", leading to earlier, more reliable and cost effective diagnostic procedures. Other applications, specifically in molecular imaging are also made possible by the miniaturization of the probe (combination with biopsy needle for solid organs use or lymph node detection) and by the compatibility of the system with other imaging modalities (auto-fluorescence and narrow-band imaging endoscopy, MRI, PET, etc).

In a retinal imaging instrument, the ocular aberrations are time-varying, leading to images degradation. Adaptive Optics improves resolution. We describe here several modifications made on our system and their impact in terms of image quality.

The high angular resolution provided by adaptive optics allows detailed study of the environment of bright objects such as stars or AGNs, provided that dazzling by the direct and scattered light from the central source does not become the main limitation. Masking the bright source with a coronagraph is the way to alleviate this problem. Rabbia and Gay (this conference) propose a possible solution. We recently described another concept of faint object coronagraph using a phase mask with 4 quadrants, which presents an excellent rejection factor, and that can be rather easily made achromatic. We propose to install such a device within the NAOS/CONICA instrument. We first examine the properties of this device in terms of rejection gain versus the different factors (residual AO phase error, central obscuration, chromatism). We estimate the performances under different conditions of adaptive optics correction with NAOS/CONICA and of phase errors due to chromatism within the K band. Results of realistic simulations at K show that a gain of 10–12 magnitude is reachable. We finally describe some technical aspects of the mask manufacturing and achromatisation using two dispersive materials, as well as the implementation of the 4QC within CONICA.

Adaptive Optics assisted eye fundus imaging now provides high resolution images of the very contents of the retinal tissue. Impressive images of the mosaic of the photoreceptors have obtained by several groups and the best reported images even show the circulatory activity in capillars. Nevertheless, the natural eye movements, such as drifts or micro-saccades, generally prevent from an accurate registration of the field of view. Moreover, images obtained through scanning techniques also suffer from field distorsion. These two effects make it difficult to unambiguously extract blood cell density and velocity information. We report how Adaptive Optics assisted flood imaging of the retina, associated with an original a posteriori image registration and data analysis now permits evaluating and mapping the flow activity in the retinal micro-vessels. Examples where capillars as thin as a few micrometers are revealed only by their circulatory activity will be given. Larger field of view along the retinal vascular network will also be produced. Thanks to this high resolution functional mapping, we'll demonstrate how blood cells direct observation can be enhanced and how quantitative parameters such as velocity or density can be derived. Velocity maps of the macular vascular network at the eye's diffraction limit will finally be produced.

This paper presents a novel fibered confocal reflectance microscopy system (FCRM) specifically designed for the medical observation of biological tissues in vivo and in situ, in real time, at the cellular level: the R-600. Reflectance imaging is based on the refraction index difference between biological components while confocal imaging allow to perform the optical sectioning slice in-depth inside the tissues. The R-600 is based on a proximal scanning system, coupled with a 7 mm diameter probe made of tens of thousands of flexible optical fibers allowing in situ imaging, associated with a dedicated software performing real-time control and image processing. The R-600 provides 12 frames per second at an optical imaging depth of 30 microns, with a high lateral resolution, 1 micron, an axial resolution of 2 microns in a field of view 160 microns in diameter. Thanks to the miniaturization of the optical probe, unprecedented accessibility is made possible in organs such as the cervix or the otolaryngological sphere, in a completely non-invasive fashion. The aim of FCRM is to perform optical biopsy. As a first step towards this goal, we present here results obtained in vivo and in real-time on a human mouth , assessing the ability of the R-600 to perform rapid morphologic examination. Subcellular structures such as nuclei and membranes can be clearly distinguished on the images. Further miniaturization opens perspectives for an integrated endoscope-compatible system with broad medical applications.

The purpose of this paper is to demonstrate potential for high resolution fluorescence imaging during standard endoscopic procedures using a catheter-based confocal endoscope, compatible with standard video-endoscopes. The instrument, an F400 prototype from Mauna Kea Technologies (Paris, France), may function in various imaging modalities: auto-fluorescence or exogenous fluorescence using topical applications of fluorophores. The system is composed of a Laser Scanning Unit, a range of fibered objectives and a dedicated software, which makes it possible to obtain images at a rate of 12 frames per second. These images have a lateral resolution of 2.5 microns, an axial resolution of 15 microns, a field of view up to 600 microns x 500 microns and can be obtained at depths up to 100 microns. The miniaturized fibered probes offer unique access capabilities, specifically through the operating channel of an endoscope. So far, these studies have demonstrated the safety and efficacy of the F400 in allowing confocal laser imaging of the internal microstructure of tissues in the anatomical tract accessed by the endoscope, thanks to the miniaturization of the system. The device can be considered as a new tool towards "optical biopsies" and in vivo histology, leading to more physiologically relevant data and cost effective medicine.

Since the advent of Adaptive Optics in ophthalmic instrumentation, several attempts for improving the performances of the existing observing techniques, either in imaging or tomography, have been made. For long, Adaptive Optics have proven its ability to restore high lateral resolution with the SLO or flood imaging, or more recently to enhance the interferometric contrast and hence, the sensitivity, of OCT. Nevertheless, the direct acquisition of en face tomographic images equivalent to horizontal optical sections of the retinal tissue is still the objective of intensive developments. We report here a new instrumental approach where a time domain full field OCT setup has been coupled with a double pass adaptive optics system, providing 300 x 300 x 4 μm instantaneous optical sections of biological tissues. We will describe how the interferometric contrast is derived without any modulation of the optical path, thus giving access to targets as critical, because unstable, as the retinal tissue during in vivo ophthalmic examinations. The advantages of this new design, which benefits from the implementation of very recent deformable mirrors, featuring simultaneously a higher actuators density and a much larger stroke, will be discussed, and the ability of the system to accommodate for variable pupil sizes, thanks to wavefront sensing techniques optimized for ophthalmology, are commented. The performances of the system, in terms of X,Y,Z resolution, sensitivity, registration capability and / or image stabilisation are discussed and illustrated with results obtained in the laboratory and in clinical environment.

We report on a deconvolution method developed in a Bayesian framework for adaptive-optics corrected images of the human retina. The method takes into account the three-dimensional nature of the imaging process; it incorporates a positivity constraint and a regularization metric in order to avoid uncontrolled noise amplification. This regularization metric is designed to simultaneously smooth noise out and preserve edges, while staying convex in order to keep the solution unique. We demonstrate the effectiveness of the method, and in particular of the edge-preserving regularization, on realistic simulated data.

The advancement in adaptive optics in recent years has increased the interest in the dynamic aberrations of the eye, including those introduced by the first optical surface provided by the tear film. A curvature sensing system to measure the dynamic topography of the tear film is described. This optical system was used to measure the aberrations of the tear film on 14 eyes. The evolution of this surface is monitored through videos of the tear film topography. The effect on optical quality is studied from the time-evolution of the RMS wavefront error showing non-negligible aberration variations attributed to the tear film layer; the effect of tear film break-up on the ocular optical quality is also discussed. Furthermore, the aberration maps are decomposed into their constituent Zernike components showing stronger contributions from 4th order terms, and also from those components with vertical symmetry which can be attributed to the effect of the eye lids on the tear film. Finally, the power spectra of the RMS wavefront error evolution show that the strongest contributions of the tear film aberrations are to be found at low frequencies, typically below 2Hz.

A flexible image guide is excited by femtoseconde pulses. Precompensation of dispersion and nonlinear effects encountered in the waveguide allows the recording of two photon fluorescence endoscopic images of colon cells.

International audience; A system to measure the topography of the first optical surface of the human eye noninvasively by using a curvature sensor is described. The static corneal topography and the dynamic topography of the tear film can both be measured, and the topographies obtained are presented. The system makes possible the study of the dynamic aberrations introduced by the tear film to determine their contribution to the overall ocular aberrations in healthy eyes, eyes with corneal pathologies, and eyes wearing contact lenses.

This article describes an original method to measure the velocity of blood cells in microvessels from a single image. The method exploits a motion artifact produced by laser scanning microscope (LSM). Although velocity can be estimated from a single image, we show how a temporal sequence can then be exploited to increase the robustness and accuracy of the estimation. Preliminary experiments show good quantitative results in synthetic images of microvessels, and good qualitative results with real images of microvessels acquired in vivo and in situ at a temporal frequency of 2 Hz . A quantitative validation of real measurements is under progress with a specific experimental set-up described in the article.

International audience; We present the first high-contrast images obtained at the ESO Very Large Telescope using a four-quadrant phase mask coronagraph. The two-night commissioning was carried out in 2004 January on NACO, the near-IR camera with adaptive optics at UT4. We evaluated the behavior of the coronagraph on a variety of astrophysical targets: binary stars, circumstellar disks, and active galactic nuclei. The performance of the coronagraph is in agreement with our expectations based on numerical simulations. The phase mask provides a stellar peak attenuation of a factor of about 10 on average (for long exposure), and its performance is limited only by the phase residuals (mainly low-order aberrations) that are left uncorrected by the adaptive optics system.

International audience; In vivo imaging of the retina on humans by means of adaptive optics can lead to a significant gain in resolution. We demonstrate the realization and use of a system made of a Shack-Hartmann wavefront sensor carefully matched to a 13-actuator bimorph deformable mirror sensor, operating at a closed loop frequency of 70 Hz at lambda=835 nm. Even with this simple but optimized system with 12 degrees of freedom, correcting only aberrations of moderate orders, we routinely and systematically obtain retinal images containing spatial information up to half the diffraction limit frequency of a dilated (7 mm) iris at a lambda=550 nm wavelength (1.6 mum diffraction spot size). Signal-to-noise ratio on the images is limited by eye safety constraints, but is sufficient to reach the high-frequency information on single, short-exposure (7 ms) images, which clearly show individual cones and capillary details. Correction is highly depending on proper centering of the eye, achieved with an active target. Focusing through the retina is possible with a reduced depth of focus. Variability of moderate order aberrations among dilated subjects has been observed. Using an image fitting algorithm, individual images are used to build a wider field corrected image of the retina (~3°), possibly useful for diagnosis and microcirculation analysis.

CONICA has been developed by a German consortium under an ESO contract, to serve together with the VLT adaptive optics system NAOS as a high resolution multimode NIR camera and spectrograph. We report on final laboratory performance tests carried out during the integration period with the adaptive optics. Apart from an outline of the capabilities of this multimode instrument such as high resolution imaging, spectroscopy, Fabry-Perot and a sophisticated internal flexure compensation, we will turn our attention to a detailed examination of the detector characteristics to fully exploit the potential of the ALADDIN array.

MIRI is the mid infrared instrument planned for the NGST. Working in the 5-28 μm band, it includes 3 units: a spectrograph, an imager and a calibration facility. We describe here the optical design of the MIRI imager channel as it is at teh end of the phase A study. The MIRI imager provides 3 observing modes: an imaging mode with a field of view of 1.3 arcmin x 1.7 arcmin and a Pixel Field of View of 0.1 arcsec/pixel, a coronagraphic mode and a low resolution spectroscopic mode for point sources, between 5 μm and 10 μm, with a spectral resolution R = λ/Δλ around 100.

NAOS is the first adaptive optics system installed at the VLT 8m telescopes. It was designed, manufactured and tested by a french Consortium under an ESO contract, to provide compensated images to the high angular resolution IR spectro-imaging camera (CONICA) in the 1 to 5 μ m spectral range. It is equipped with a 185 actuator deformable mirror, a tip/tilt mirror and two wavefront sensors, one in the visible and one in the near IR spectral range. It has been installed in November at the Nasmyth focus B of the VLT UT4. During the first light run in December 2001, NAOS has delivered a Strehl ratio of 50 under average seeing conditions for bright guide stars. The diffraction limit of the telescope has been achieved at 2.2 μ m . The closed loop operation has been very robust under bad seeing conditions. It was also possible to obtain a substantial correction with m V=17.6 and m K=13.1 reference stars. The on-sky acceptance tests of NAOS-CONICA were completed in May 2002 and the instrument will be made available to the European astronomical community in October by ESO. This paper describes the system and present the on-sky performance in terms of Strehl ratio, seeing conditions and guide star magnitude.

Only a very few examples of near-infrared wavefront sensors can be found in the litterature. However, none of these sensors provide routine observation yet. Our sensor is the only one to be operated routinely on a large AO system. Entirely cryogenized, this sensor is built around a so-called HAWAII array from Rockwell (HgCdTe, 1024×1024). It is working in the huge spectral band ranging from 0.8 to 2.55 microns, and may use -when required- all the flux from this very whole band. It allows to switch between several optical configurations in order to match all atmospheric and observing conditions, while its original mechanical design allows to keep, even at cryogenic temperatures, a mechanical stability lower than 4 microns in any position. It also has some particular read-out schemes, allowing to obtain frame rates as high as 1200 Hz while keeping a read-out noise performance of 10 electrons rms/pixel. The analysis of the design parameters (pixel size, field of view) is exposed in this article. Some results, obtained during the comissioning runs at ESO, will also be presented.

CONICA is the first AO equipped multimode near infrared camera which saw first light at the VLT in the end of 2001. A technique will be described to benefit of the AO system NAOS to correct not only for atmospheric turbulence but also for the internal optical aberrations of the high resolution camera. The aberrant optical components in the light path of CONICA are outside of the AO loop and therefore no self-acting correction is possible. Independently of the AO wave front sensor, a separate measurement of these minor aberrations using a method called phase diversity allows to predict for the variety of camera configurations the corresponding aberrations. They are quantified by sets of Zernike coefficients which are rendered to the adaptive optics. This technique turns out to be very flexible and results into a further improvement of the optical overall performance.

The Adaptive Optics NIR Instrument NAOS-CONICA has been commissioned at the VLT (UT4) between November 2001 and March 2002. After summarizing the observational capabilities of this multimode instrument in combination with the powerful AO-system, we will present first on sky results of the instrumental performance for several non-direct imaging modes: High spatial resolution slit-spectroscopy in the optical and thermal NIR region has been tested. For compact sources below 2 arcsec extension, Wollaston prism polarimetry is used. For larger objects the linear polarization pattern can be analyzed by wire grids down to the diffraction limit. Coronographic masks are applied to optimize imaging and polarimetric capabilities. The cryogenic Fabry-Perot Interferometer in combination with an 8m-telescope AO-system is shown to be a powerful tool for imaging spectroscopy (3D-scans).

Observing at high angular resolution from the ground is not made possible with Adaptive Optics alone, and besides the turbulence residuals, atmospheric refraction, thermal background or instrument's mechanical flexures may also severely limit the gain of optical quality that AO techniques are supposed to provide. We describe here how NAOS, the newly installed AO system on the VLT, has been designed to accommodate for these unavoidable effects. In particular, beam chopping, flexures compensation and AO tracking on reference objects with a significant relative motion will be addressed. It will thus be shown how long term astronomical observations at the diffraction limit can be carried out with an AO system under regular ground level conditions, thanks to the implementation of original technical solutions.

During the last 30 years, the Space Research Department (DESPA) of Paris Observatory has developed infrared instrumentation for space and ground-based telescopes. First, we present the PbS linear detector of the ISM IR imaging spectrometer of the Phobos mission. Then the CID InSb focal plane of ISOCAM-SW is described. The studies of this CID InSb focal plane allowed us to develop an IR camera for the first astronomical observations using adaptive optics. We also describe the linear array built for the OMEGA imaging spectrometer of the Mars 96 mission. The last chapter is dedicated to the IR spectrometer of the Huygens probe. To conclude, the needs and challenges in the area of mid-band infrared astronomy are discussed.

NAOS is the adaptive optics system to be installed at one of the Nasmyth focus of the VLT. It was designed and manufactured by a French Consortium to provide compensated images to the high angular resolution IR spectro-imaging camera (CONICA) in the 1 to 5 micrometer spectral range. For bright sources, NAOS will achieve a Strehl ratio of 70% under average seeing conditions. It is equipped with a 185 actuator deformable mirror, a tip/tilt mirror and two wavefront sensors, one in the visible and one in the near IR. All the components of NAOS have been delivered and the integration phase is in progress since the beginning of 2000. After extensive tests and performance verifications in France, the system will be shipped to Chile by the end of 2000. The first light at the VLT is foreseen in the beginning of 2001.

When combined with Adaptive Optics, integral field spectroscopy, i.e. observation of a sky field simultaneously in a number of spectral passbands, is the most efficient way to perform spectro-imaging at high angular resolution. GriF will provide the CFHT community with such a capability in the near infrared K-band. This extension will be completed by means of two simple optical devices to be installed in the KIR cryostat (the infrared camera of PUEO): a cooled grism in the filter-wheel and a cold aperture on an entrance focal plane wheel. They will be completed by a room-temperature Fabry- Perot (FP) interferometer in front of KIR. The FP selects narrow bandpass images while the grism spatially separates them, giving a 3-D spectroscopic capacity within a compact and light design. At each exposure, several (up to 9) monochromatic images of a rectangular field of about 36 arcseconds X 4 arc-seconds will be simultaneously acquired, allowing a precise subtraction of continuum and background. The cooled grism will guarantee a low background environment, thus a good sensitivity at K. The medium spectral resolution (about 2600) will fit to a number of programs and will represent a considerable improvement on imaging with narrow- band filters. Thus, combining high angular resolution with the spectroscopic diagnosis, GriF will allow the study of a large class of compact objects or structures, especially in the extragalactic domain where its sensitivity should be unique.

This paper gives a general overview of the application of focal plane masks to adaptive optical wavefront sensing systems, and shows how they are related to several wavefront sensor used in optical shop testing. The results of several numerical simulation of a wavefront sensor based on a phase contrast type focal plane mask are then presented. In the last section, we outline a proposal for a wavefront sensor based on a dark ground type focal plane mask. This method can be used in conjunction with fiber based optical interferometers to yield an adaptive optics system which does not need to take corrected light from the observation path for use in the analysis of the aberrations. Only aberrated light is taken from the observation path and sent to the wavefront sensor, thus creating a very economical wavefront sensor.

The design of adaptive optics system requires astrophysically driven requirements and specifications. We present here the study performed to help specifying and designing the ESO Nasmyth Adaptive Optics System of the VLT.

NAOS is the adaptive optics system to be installed at one of the Nasmyth foci of the very large telescope (VLT). It will provide compensated image to the high angular resolution IR spectro-imaging camera which covers the 1-5 micrometers spectral bands. our French consortium is the sub-contractor of ESO for the design, manufacturing, integration and test of NAOS. For bright sources, the specification is to reach 70 percent Strehl ratio under average seeing conditions. Two wavefront sensors, one in the visible spectral range and one in the near IR spectral range, will equip the adaptive optics system. We foresee to obtained the first light at the VLT unit telescope 1 in mid-2000.

A 1-5 micrometers astronomical infrared imaging camera, COMIC, is currently being developed for the ADONIS adaptive optics system, as a collaborative project of Observatoire de Paris and Observatoire de Grenoble under ESO (European Space Observatory) contract. This camera is based on a 128 by 128 HgCdTe/CCD array built by the CEA-LETI-LIR (Grenoble, France). Among its main characteristics, this detector offers a very high storage capacity of 3 106 e- with a total system read-out noise of about 600 e- which makes it particularly optimized for the 3-5 mum. COMIC will be installed in the fall of 1995 at the output focus of the ADONIS AO system on the ESO 3.6-m telescope at La Silla (Chile).© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

ADONIS (ADaptive OPtics Near Infrared System) is an upgrade of the COME-ON+ adaptive optics prototype. It will allow the astronomical community to use adaptive optics as a common user instrument. This paper describes the main features of the new system, including a mechanical and optical interface for specific visitor equipment and imaging capabilities. We present here the 128 X 128 infrared imaging camera, covering the 1 - 5 micrometers spectral range.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

ADONIS is an adaptive optics user friendly instrument for the ESO 3.6-m telescope. The modal control technique is presented as a tool for optimizing the control of ADONIS. The perturbed wavefront is spread over a base of modes treated by the system in terms of their behavior with respect to the observing conditions (turbulence characteristics, anisoplanatic angle and star magnitude). This optimization and the multiple parameters influencing the system performance are difficult to handle by the astronomer. Moreover, the wide range of situations the astronomical AO system has to deal with requires a flexible configuration which has to be optimized for each case. The ADONIS instrument also has to be easy to use by an astronomer without who doesn't have a deep knowledge of the AO techniques. Finally, it must make an efficient use of the telescope time. Hence, a new human interface and an intelligent control system are designed.

International audience; The dynamic aberrations introduced by the human tear film are studied by measuring the topography of the tear film surface on 14 subjects using a curvature sensing setup. The RMS wavefront error variation of the data obtained is presented showing the non-negligible contribution of the tear film to overall eye aberrations. The tear film wavefronts are decomposed in their constituent Zernike terms, showing stronger contributions from 4th order terms and terms with vertical symmetry, and the temporal behaviour of these aberrations is analysed.

The Infrared Space Observatory (ISO) camera (ISOCAM) is designed to map selected regions of the sky in the spectral region from 2.5 to 17 μm at various spatial and spectral resolutions and at high sensitivity (at >4 μm

An infrared camera for use in ground based astronomical observations in the 1-5 microns region of the spectrum under low photon flux , has been developped in Meudon Observatory . This camera uses a 32 x 32 pixels InSb Charge Injection Device built by SAT (*) . We hereafter present a description of the camera , its performances and some results , recently obtained at OPMT and ESO with 2 and 2.2 m telescopes .© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.