FRD - Investigación - Ciencia y Tecnología

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Author: search.filters.author.Torga, Jorge RománSubject: search.filters.subject.Optical coherence tomography

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    Interferometric system based on swept source-optical coherence tomography scheme applied to the measurement of distances of industrial interest
    (2015-12-11) Morel, Eneas Nicolás; Russo, Nélida A.; Torga, Jorge Román; Duchowicz, Ricardo
    We used an interferometric technique based on typical optical coherence tomography (OCT) schemes for measuring distances of industrial interest. The system employed as a light source a tunable erbium-doped fiber laser of ∼20-pm bandwidth with a tuning range between 1520 and 1570 nm. It has a sufficiently long coherence length to enable long depth range imaging. A set of fiber Bragg gratings was used as a self-calibration method, which has the advantage of being a passive system that requires no additional electronic devices. The proposed configuration and the coherence length of the laser enlarge the range of máximum distances that can be measured with the common OCT configuration, maintaining a good axial resolution. A measuring range slightly >17 cm was d0.etermined. The system performance was evaluated by studying the repeatability and axial resolution of the results when the same optical path difference was measured. Additionally, the thickness of a semitransparent medium was also measured.
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    Extending low-coherence interferometry dynamic range using heterodyne detection
    (2020-08) Cusato, Leslie; Cerrotta, Santiago; Torga, Jorge Román; Morel, Eneas Nicolás
    Low-coherence interferometry (LCI) technique is generating considerable interest in industrial applications where there is a need for larger measurements with high resolution. Conventional Fourier domain systems reach a limiting depth of around 3 mm, mainly due to the spectrometers used as detectors. In this work, we present an optical detection system that performs the Fourier transform of the LCI signals, based on a spatial heterodyne spectrometer. This device avoids the fall-off effect of the spectrometer, allowing to reach measurable optical depths of almost 5 cm without losing resolution. We describe the theory underlying this detection system and present experimental results which are in great accordance.
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    Application of a long-rangesweptsource optical coherence tomography-based scheme for dimensional characterization of multilayer transparent objects
    (2017-08-18) Morel, Eneas Nicolás; Russo, Nélida A.; Torga, Jorge Román; Duchowicz, A.N.
    This work presents the use of a recently develop edinter ferometric system based on the swept source optical coherence tomography (SS-OCT) technique, which allows the characterization of transparent and semitransparent multilayer systems employing a tunablefiber-optic laser with a coherence length suitable for achieving long-deeprange imaging (<10  cm). The inclusion of fiber Bragggratings in the system allow sit to perform a self-calibration in each sweep of the light source. Measurements carried out on cuvettes, ampoules, small bottles, and glass containers used in the pharmaceutic al industry are presented. The thicknesses of the walls and the distance between them were determined. Transparent and semitransparent objects of a multilayer type of different thicknesses were also measured. The configuration presented allow sextension of the measurement range obtainable with the usual OCT systems, demonstrating the potentiality of the proposed scheme to carry out quality control in industrial applications.
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    Reduction of measurement errors in OCT scanning
    (Spie Digital Library, 2018-03-05) Sallese, Marcelo; Morel, Eneas Nicolás; Tabla, Pablo; Torga, Jorge Román
    Optical coherence tomography (OCT) is a non-destructive optical technique, which uses a light source with a wide band width that focuses on a point in the sample to determine the distance (strictly, the optical path difference, OPD) between this point and a reference surface. The point can be superficial or at an interior interface of the sample (transparent or semitransparent), allowing topographies and / or tomographies in different materials. The Michelson interferometer is the traditional experimental scheme for this technique, in which a beam of light is divided into two arms, one the reference and the other the sample. The overlap of reflected light in the sample and in the reference generates an interference signal that gives us information about the OPD between arms. In this work, we work on the experimental configuration in which the reference signal and the reflected signal in the sample travel on the same arm, improving the quality of the interference signal. Among the most important aspects of this improvement we can mention that the noise and errors produced by the relative reference–sample movement and by the dispersion of the refractive index are considerably reduced. It is thus possible to obtain 3D images of surfaces with a spatial resolution in the order of microns. Results obtained on the topography of metallic surfaces, glass and inks printed on paper are presented.
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    Feasibility and analysis of a system of two in tandem interferometers for optical coherence tomography
    (IEE Explore Digital Library, 2017-12-18) Cerrotta, Santiago; Morel, Eneas Nicolás; Alvira, Fernando; Torga, Jorge Román
    A signal obtained from a combined system of two interferometers of low coherence in the frequency domain is presented and analyzed. This system allows to expand the range of measurement offered by the conventional optical tomography system of a single interferometer with a spectrometer as a detector.