Examinando por Materia "Interferometry"
Mostrando 1 - 16 de 16
Resultados por página
Opciones de ordenación
Ítem Analysis of vibrations in a plate using interferometric methods(SPIE, 2004-10-21) Ángel-Toro, Luciano; Prieto, Daniel Velasquez; Rueda Muñóz, Edgar Alberto; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaIn this work some frequencies and modes of vibration of a thin plate were determined using interferometric methods like: real-time holographic interferometry, time-average holographic interferometry, digital speckle pattern interferometry DSPI. And the results obtained are compared with those obtained with the program of finite elements COSMOS.Ítem Design of a control system for interferometric fringe stabilization system with remote access(SPIE-INT SOC OPTICAL ENGINEERING, 2013-01-01) Espitia-Gomez, Javier; Angel-Toro, Luciano; Velasquez, Daniel; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaStability in a fringe pattern is a necessary condition in interferometric processes, such as holography, and not always is enough the use of passive stabilization systems, like holographic tables, in particular, when perturbations are caused by thermal or acoustic variations. For these cases, active systems are required. In this work it is presented the implementation of a control system for interferometric fringes stabilization. The interferometric arrangement characteristics are also discussed, which permits to act independently over each of the interferometer's arms by means of two piezoelectric actuators that change the length of the optical path of light that goes through, in order to perturb the system and simultaneously compensate this perturbation in real time. It is also shown that the proposed system allows evaluating the control system's performance subjected to diverse perturbations, and it is shown how remote access was given to the implemented platform. © 2013 SPIE.Ítem Design of a control system for interferometric fringe stabilization system with remote access(SPIE, 2013-11-18) Espitia-Gómez, Javier; Ángel Toro, Luciano; Velásquez Prieto, Daniel; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaStability in a fringe pattern is a necessary condition in interferometric processes, such as holography, and not always is enough the use of passive stabilization systems, like holographic tables, in particular, when perturbations are caused by thermal or acoustic variations. For these cases, active systems are required. In this work it is presented the implementation of a control system for interferometric fringes stabilization. The interferometric arrangement characteristics are also discussed, which permits to act independently over each of the interferometer's arms by means of two piezoelectric actuators that change the length of the optical path of light that goes through, in order to perturb the system and simultaneously compensate this perturbation in real time. It is also shown that the proposed system allows evaluating the control system's performance subjected to diverse perturbations, and it is shown how remote access was given to the implemented platform. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.Ítem Double exposure specklegrams obtained by using scaled aperture pupils(SPIE-INT SOC OPTICAL ENGINEERING, 2001-01-01) Angel, L; Tebaldi, M; Trivi, M; Bolognini, N; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaIn speckle photography the pupil aperture is usually not modified between exposures. In our work, the change of the pupil aperture scale between exposures is analysed on the basis of double-exposed image speckle, before and after a diffuser inplane displacement is done. The apertures have the same shape but its scale is modified between exposures. Note that the relative position of the aperture is maintained. In particular, we analyse a simple case that uses a circular aperture whose diameter is modified for recording each image. The intensities in the image plane and the fringe visibility are evaluated, in terms of the geometric characteristics of the pupils. © 2001 SPIE · 0277-786X/01/$15.00.Ítem Electronic speckle pattern interferometry technique for the measurement of complex mechanical structures for aero-spatial applications(SPIE-INT SOC OPTICAL ENGINEERING, 2010-01-01) Restrepo, R.; Uribe-Patarroyo, N.; Garranzo, D.; Pintado, J.M.; Frovel, M.; Belenguer, T.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaUsing the electronic speckle pattern interferometry (ESPI) technique in the in-plane arrangement, the coefficient of thermal expansion (CTE) of a composite material that will be used in a passive focusing mechanism of an aerospace mission was measured. This measurement with ESPI was compared with another interferometric method (Differential Interferometer), whose principal characteristic is its high accuracy, but the measurement is only local. As a final step, the results have been used to provide feedback with the finite element analysis (FEA). Before the composite material measurements, a quality assessment of the technique was carried out measuring the CTE of Aluminum 6061-T6. Both techniques were compared with the datasheet delivered by the supplier. A review of the basic concepts was done, especially with regards to ESPI, and the considerations to predict the quality in the fringes formation were explained. Also, a review of the basic concepts for the mechanical calculation in composite materials was done. The CTE of the composite material found was 4.69X10-6 ± 3X10-6K-1. The most important advantage between ESPI and differential interferometry is that ESPI provides more information due to its intrinsic extended area, surface deformation reconstruction, in comparison with the strictly local measurement of differential interferometry. © 2010 Copyright SPIE - The International Society for Optical Engineering.Ítem Evaluación de la coherencia de la luz en la implementación de un sistema de microscopía óptica(Universidad EAFIT, 2017) Cadavid Muñoz, Juan José; Restrepo Gómez, RenéÍtem Evaluation of a liquid crystal based polarization modulator for a space mission thermal environment(Elsevier B.V., 2017-10-15) Silva-López M.; Bastide L.; Restrepo R.; García Parejo P.; Álvarez-Herrero A.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaThe Multi Element Telescope for Imaging and Spectroscopy (METIS) is one of the remote sensing instruments to be onboard the future NASA/ESA Solar Orbiter mission. The science nominal mission orbit will take the spacecraft from 0.28 to 0.95 astronomical units from the Sun, setting challenging and variable thermal conditions to its payload. METIS is an inverted-occultation coronagraph that will image the solar corona in the visible and UV wavelength range. In the visible light path a Polarization Modulation Package (PMP) performs a polarimetric analysis of the incoming solar light. This PMP is based on liquid crystal variable retarders (LCVR) and works under a temporal modulation scheme. The LCVRs behavior has a dependence on temperature and, as a consequence, it is critical to guarantee the PMP performance in the mission thermal environment. Key system specifications are the optical quality and the optical retardance homogeneity. Moreover, the thermally induced elastic deformations of the mechanical mounts and the LCVRs shall not produce any performance degradation. A suitable thermal control is hence required to maintain the system within its allowed limits at any time. The PMP shall also be able to reach specific set-points with the power budget allocated. Consequently, and in order to verify the PMP thermal design, we have experimentally reproduced the expected thermal flight environment. Specifically, a thermal vacuum cycle test campaign is run at the different mission operational conditions. The purpose is both to check the stability of the thermal conditions and to study the optical quality evolution/degradation. Within this test transmitted wavefront measurements and functional verification tests have been carried out. To do that we adapted an optical interrogation scheme, based on a phase shifting interferometric technique, that allows for inspection of the PMP optical aperture. Finally, measurements obtained at nonoperational temperature conditions are also shown. These results demonstrate that the device meets the specifications required to perform its operational role in the space mission environment. (C) 2017 The. Authors. Published by Elsevier B.V.Ítem Formación y restauración de imagen en tomografía óptica de coherencia mediante posprocesamiento(Universidad EAFIT, 2017) Cuartas Vélez, Carlos Alfredo; Restrepo Gómez, René; Uribe Patarroyo, NéstorÍtem High dynamic range imaging method for interferometry(ELSEVIER SCIENCE BV, 2011-01-01) Vargas, J.; Restrepo, R.; Quiroga, J.A.; Belenguer, T.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaWe demonstrate a method to easily and quickly extend the dynamic range imaging capabilities of the camera in a typical interferometric approach. The camera dynamic range is usually low and limited to 256 gray levels. Also, it is well known that one may have over or under-exposed regions in the interferogram (due to non-uniform illumination) which makes these image regions not reliable. In our proposed method it is not necessary to obtain or use the non-linear camera response curve in order to extend the camera dynamic range. We obtain a sequence of differently exposed interferograms, typically five or six; after that, we compute the corresponding normalized fringe patterns and modulation maps using a typical normalization method. These normalized patterns are combined through a temporal weighted average using as weights the corresponding modulation maps. We show a set of experimental results that prove the effectiveness of the proposed method. © 2011 Elsevier B.V. All rights reserved.Ítem Improvement of the signal-to-noise ratio in interferometry using multi-frame high-dynamic-range and normalization algorithms(ELSEVIER SCIENCE BV, 2012-01-01) Restrepo, R.; Uribe-Patarroyo, N.; Belenguer, T.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaUsing both high dynamic range (HDR) and normalization methodologies, we show a method to improve the fringe pattern contrast in interferometric measurements normally used for phase recovering. In a simulated interferogram that mimics the main effects that can be found in an interferometric process (stray-light, photon noise, electronic noise, scattering phenomena, etc.) it was possible to improve the contrast of the fringes and to decrease the root mean square error by more than 35%. The method proposed is applied to experimental interferograms to measure wavefront error and retardance changes on liquid crystal (LC) devices. It is done by using a Mach-Zehnder set-up in which we used different polarization areas. The proposed method increases the quality of the phase recovered and decreases the root mean square error by 50%. © 2011 Elsevier B.V. All rights reserved.Ítem Multiple-aperture speckle method applied to local displacement measurements(Elsevier B.V, 2007) Ángel-Toro, Luciano; Tebaldi, Myrian; Bologninic, Néstor; Ángel-Toro, Luciano; Tebaldi, Myrian; Bologninic, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Luciano Angel Toro (langel@eafit.edu.co); Óptica AplicadaThe goal of this work is to analyze the measurement capability of the modified speckle photography technique that uses different multiple aperture pupils in a multiple exposure scheme. In particular, the rotation case is considered. A point-wise analysis procedure is utilized to obtain the fringes required to access to the local displacement measurements. The proposed arrangement allows simultaneous displaying in the Fourier plane several fringes system each one associated with different rotations. We experimentally verified that the local displacement measurements can be determined with a high precision and accuracy.Ítem Multiple-aperture speckle method applied to local displacement measurements(ELSEVIER SCIENCE BV, 2007-06-01) Angel, Luciano; Tebaldi, Myrian; Bolognini, Nestor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaThe goal of this work is to analyze the measurement capability of the modified speckle photography technique that uses different multiple aperture pupils in a multiple exposure scheme. In particular, the rotation case is considered. A point-wise analysis procedure is utilized to obtain the fringes required to access to the local displacement measurements. The proposed arrangement allows simultaneous displaying in the Fourier plane several fringes system each one associated with different rotations. We experimentally verified that the local displacement measurements can be determined with a high precision and accuracy. © 2007 Elsevier B.V. All rights reserved.Ítem Phase stepping in Lau interferometry(Elsevier, 1999-06-15) Ángel-Toro, Luciano; Tebaldi, Myrian; Henao, Rodrigo; Ángel-Toro, Luciano; Tebaldi, Myrian; Henao, Rodrigo; Universidad EAFIT. Departamento de Ciencias Básicas; langel@eafit.edu.co; Óptica AplicadaThe implementation of phase shifting interferometry to analyze the Lau interferometric fringe patterns is proposed. The fundamentals of this application are theoretically discussed and the basis of the phase map interpretation is outlined. The three steps algorithm is used to depict the phase maps of lens-like test objects and an application for measuring focal lengths of lenses is reported. Experimental results are presented. q1999 Elsevier Science B.V. All rights reserved.Ítem Plataforma de simulación de aberraciones ópticas vía implementación de las características de un SLM y reconstrucción de fase usando algoritmos basados en los sensores de Hartmann-Shack(Universidad EAFIT, 2013) Ramírez Cano, Natalia; Restrepo Gómez, René; Ángel Toro, LucianoDada la importancia que hoy día presenta dentro del ámbito de la óptica, la implementación y conocimiento de dispositivos capaces tanto de generar aberraciones ópticas bien caracterizadas como de censarlas, se presenta a lo largo de este trabajo el desarrollo de una interfaz gráfica en MATLAB, que permita simular el funcionamiento tanto de un sensor de frente de onda de Hartamnn-Shack (HS), así como la simulación de dispositivos capaces de modificar frentes de onda como los SLM, adicionando algoritmos de propagación y cálculo de centroides -- Para ello, se implementarán en primer lugar máscaras de fase que generen frentes de onda aberrados a partir de la modulación en fase de moduladores espaciales de luz o SLM, tanto a través de funciones lente de primer orden en representación de las aberraciones constantes, como de fase cuadrática en representación de las aberraciones de bajo orden y adicionalmente como combinaciones lineales de polinomios de Zernike -- Todo lo anterior se simulará teniendo en cuenta las características técnicas de los SLM, como lo son el número de pixeles en x y en y, el tamaño de estos y la curva de calibración de los moduladores espaciales, tanto para una relación lineal como para una relación no lineal -- Posteriormente se simularán las dos propagaciones sufridas por los haces de luz desde el SLM hasta el CCD (dispositivo de carga acoplada), pasando a través de la matriz de multilentes del HS (MLA), a partir de la implementación de algoritmos de propagación de un solo paso, que nos permitirán observar sobre el plano del CDD el mapa de spots necesario para el censado de las superficies -- Continuaremos con la construcción de algoritmos para determinar los centroides de dicho mapa y sus respectivas coordenadas, seguiremos con la implementación de algoritmos de reconstrucción modal empleados por sensores de frente de onda de Hartmann-Shack, y finalmente compararemos el grado de error existente entre las superficies generadas y las superficies censadas a través del cálculo de su error cuadrático medioÍtem Speckle interferometric technique to assess soap films(Elsevier B.V., 2003-10-17) Ángel Toro, Luciano; Bolognini, Néstor Alberto; Tebaldi, Myrian Cristina; Trivi, Marcelo Ricardo; Universidad EAFIT. Departamento de Ciencias Básicas; langel@eafit.edu.co; Óptica AplicadaAn speckle interferometric technique to monitor the thinning process of vertical soap film before the film rupture is presented -- The interferometric arrangement consists in a double aperture pupil optical system which images an input diffuser -- In a first step, a reference specklegram is stored in the computer buffer memory -- Afterwards, the soap film is located in front of one pupil aperture, an uniform displacement of the diffuser is produced and a new speckle pattern is stored -- The soap film status is characterized in terms of the changes that this dynamic phase object introduces in the correlation fringes obtained by applying a FFT algorithm to the resulting summed specklegram. This procedure is done in real time as far as the soap film evolves in the successive status -- It is experimentally demonstrated that the soap film during drawing acts as a variable wedge -- The correlation fringes behavior becomes an important tool to establish the wedge shaped soap film angle and the thickness variations 2003 Elsevier B.V. All rights reservedÍtem Speckle photography with different pupils in a multiple-exposure scheme(Optical Society of America, 2000-01-01) Ángel Toro, Luciano; Bolognini, Néstor Alberto; Tebaldi, Myrian Cristina; Trivi, Marcelo Ricardo; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaThe use of different multiple-aperture pupils for recording each image in speckle photography is proposed -- The introduction of suitable spatial frequency carriers, by internally modulating imaged speckles, allows one to selectively isolate or combine the spectral content of different images into spatially separated regions in the Fourier plane -- Theoretical and experimental results extend the speckle photography technique to the depiction of several specklegrams of multiple uniform in-plane displacements -- In this case, because different pupils are considered for recording, the cross-correlation functions for the amplitudes and intensities in the image plane are calculated on the basis of the statistical properties of the object -- Also, the ensemble-average intensity in the Fourier plane is analytically derived, and fringe visibility is investigated. © 2000 Optical Society of America [S0740-3232(00)01701-4]OCIS codes: 120.0120, 120.3180, 120.3940, 120.6160