FRD - Investigación - Ciencia y Tecnología

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Author: search.filters.author.Cerrotta, SantiagoSubject: search.filters.subject.Facultad Regional Delta

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Now showing 1 - 7 of 7
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    Fabry Perot detector for low coherence interferometry
    (2023-06) Cerrotta, Santiago; Torga, Jorge Román; Morel, Eneas Nicolás
    Se proponen dos diseños teóricos de detectores de intensidad para distintas longitudes de onda basados en cavidades Fabry Perot para ser aplicados en la técnica de interferometría de baja coherencia en el dominio de las frecuencias (FD-LCI). Un detector axial unidimensional que consta de una cavidad variable con un fotodiodo y otro detector radial con cavidad fija y con un array lineal o cámara. Se demostró su factibilidad teórica realizando simulaciones de haces gaussianos propagándose a través de cavidades con diferentes características. Se optimizaron los parámetros para que los detectores estén centrados en 850 nm, con rangos de 60 nm y resolución por debajo del nanómetro para haces de 500 µm de cintura, condiciones típicas de las fuentes y detectores usadas en FD-LCI. Además, el diseño contempla la posibilidad de usarlos simultáneamente.
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    Long-range frequency domain low-coherence interferometry detector for industrial applications
    (2023-01) Cerrotta, Santiago; Torga, Jorge Román; Morel, Eneas Nicolás
    A low-cost long-range frequency domain low-coherence interferometry (LCI) detector is presented: time Fourier domain LCI (TFD-LCI). Combining ideas of time domain and frequency domain techniques, the TFD-LCI detects the analog Fourier transform of the optical interference signal with no limitation for the maximum optical path, measuring the thickness of several centimeters with micrometer resolution. A complete characterization of the technique is presented with a mathematical demonstration, simulations, and experimental results. An evaluation of repeatability and accuracy is also included. Measurements of small and large monolayer and multilayer thicknesses were done. Characterization of the internal and external thicknesses of industrial products such as transparent packages and glass windshield is presented, showing the potentiality of TFD-LCI for industrial applications.
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    Estimación de frecuencias de señales interferométricas con redes neuronales
    (2023-09) Cerrotta, Santiago; Morel, Eneas Nicolás
    Una vez adquirida la señal óptica de la técnica de interferencia de baja coherencia mediante un espectrómetro es necesario realizar un post procesado para encontrar la frecuencia de oscilación característica de la señal. Esta señal me brinda información morfológica (espesor, topografía, etc) de la muestra en estudio. En este trabajo se diseñan, entrenan e implementan Redes Neuronales Artificiales que permiten reemplazar herramientas convencionales en el procesamiento de señales oscilantes y en particular el cálculo de la Transformada de Fourier. Se analiza la precisión y los tiempos característicos de estas redes demostrando que son una opción viable para estimar frecuencias de señales oscilatorias.
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    Scanning optical coherence tomography applied to the characterization of surfaces and coatings
    (El Sevier, 2014) Cerrotta, Santiago; Morel, Eneas Nicolás; Torga, Jorge Román
    This paper shows the technique of optical coherence tomography in the frequency domain (OCT-FD) to obtain surface topography and tomography of surface coatings. The setup is based on a superluminescent diode centered on 849 nm with an spectral wide of 50 nm as the light source, a single-mode fibre Michelson interferometer and a spectrometer as the detector system. This scheme allows having compact and robust equipments that was designed to be used in an industrial environment. With this system it can be obtain a tridimensional image acquired point by point with a maximum range of 20 mm width and length and 2 mm depth. Images obtained from the topography of metal samples and tomography of polymer based coatings is presented. Also it is shown that is possible to obtain, from these images, parameters of interest of the sample, such as roughness, flatness and characteristic distances. As an example to show the potential of the method the dimensions of a metal surface modified after laser ablation were measured from a topography image obtained with this technique. A second example presented was the image obtained of a roughness pattern made on a metal surface. Finally it was presented a tomography image of a modified polyurethane coating deposited on a metal surface. Thickness and refractive index of the coating were obtained after the image analysis.
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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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    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.
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    Large Axial Range Frequency-Domain Optical Low Coherence Interferometry
    (2019-01-15) Cerrotta, Santiago; Morel, Eneas Nicolás; Alvira, Fernando; Torga, Jorge Román
    In this paper, we propose a new experimental setup to extend the measurement range of frequency-domain low coherence interferometry (FD-LCI) from 3 mm to 2 cm. The FD-LCI can be extended to the technique of frequency domain optical coherence tomography (FD-OCT) by performing additional lateral scanning. This new and simple arrangement just attaches an extra interferometer before the spectrometer in a typical FD-LCI setup. With this configuration, it is possible to overcome the limitation of the dynamic range of the conventional technique. This allows us to measure the optical path difference of the sample of interest, which is outside the detection range of the spectrometer, using an extra interferometer as a tuner system. In addition, this tuning allows significant minimization of the effects produced by the fall-off. The accuracy of the new system is obtained by adding the FD-LCI and the tuning micrometric translator accuracies. In our experimental setup, this value is 20 μm.