Examinando por Materia "Liquid crystals"

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    Applications of spatial light modulators in speckle interferometry
    (SPIE-INT SOC OPTICAL ENGINEERING, 2012-01-01) Bodendorfer, T.; Restrepo, R.; Belenguer, T.; Koch, A.W.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    High resolution spatial light modulators (SLM) have been used in many different ways during the last years. Regarding speckle interferometry, different applications can be realized by integrating SLMs in interferometric setup. In this work the influence of a liquid crystal based phase-only SLM on the measurement quality concerning deformation and shape measurement using two wavelengths is discussed. © 2012 Copyright SPIE.
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    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 Aplicada
    Using 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.