Cuantificación del índice de refracción de micro-objetos utilizando corrimientos de fase digital en Microscopía Holográfica Digital en Línea
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Duarte Espinosa, Marcela
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En el desarrollo de esta tesis se implementó una técnica de corrimiento de fase en una configuración experimental de Microscopía Holográfica Digital en Línea (DIHM, por sus siglas en inglés Digital In Line Holographic Microscopy) de camino común, esto a través del uso de una pantalla de cristal líquido ubicada en un Interferómetro de Difracción Puntual (PDI, por sus siglas en inglés Point Difraction interferometer) y se comprobó su eficacia a través del calculo del índice de refracción de micro-objetos traslúcidos. En esta configuración la pantalla de cristal líquido actúa como un retardador de onda y posee un agujero eléctrico en su centro de donde emerge una onda esférica. A través de la aplicación de una diferencia de potencial, se inducen cambios de fase controlados sobre toda el área de la pantalla, menos en la región del agujero; con esto se tiene un sistema de corrimiento de fase digital. El objeto traslúcido a estudiar es iluminado por una fuente de luz coherente y el campo transmitido por él se hace incidir sobre la pantalla, éste campo se comportará como onda objeto y la onda esférica que emerge por el agujero se comportará como onda de referencia, conformando con esto una arquitectura de Microscopía Holográfica Digital en línea con la posibilidad de realizar corrimientos de fase digital sobre la onda objeto, lo cual permite cuantificar la diferencia de fase entre la onda objeto y la onda de referencia, mediante un algoritmo de corrimiento de fase similar al utilizado por Yamaguchi. Previo a la cuantificación de la fase, se realizó una calibración local de la pantalla mediante un método polarimétrico, basado en las propiedades físicas de los cristales líquidos y matrices de Mueller, el cual permitió obtener una curva de variación de fase en función de la diferencia de potencial aplicado, así como verificar la homogeneidad de la variación de fase producida a la onda objeto.
Abstract: In the development of this thesis, a phase shifting technique was implemented in an experimental configuration of Digital In line Holographic Microscopy (DIHM) of common path, it was made using a liquid crystal waveplate located in a Point Diffraction Interferometer (PDI) and its effectiveness was verified through the calculation of the refraction index of translucid micro-objects. In this configuration liquid crystal waveplate act like a rotated retarder and has a electric hole in its center where emerges a spherical wave. Through the application of a potential difference, controlled phase changes are induced over the entire screen area except in the hole region; this is a digital phase shifting system. The traslucid object, which will be studied, is illuminated by a coherent light source and the field transmitted by this object hits over the screen, which will behave as object beam. The spherical wave that emerges from the small hole will be behaved as a reference beam, forming an architecture of digital in line holography microscopy with the possibility to create digital phase shifting over the object beam, which allow to quantify the phase difference between the waves (object and reference), through the similary phase shifting used by Yamaguchi. Previously to phase quantification, it was performed a local calibration over the a liquid crystal waveplate the using of a polarimetric method, based on the physical properties of liquid crystals and Muller matrix, which allowed us to obtain a curve of phase variation in terms of potential difference applied, besides to check the homogeneity of the phase variation produced to the object beam.
Abstract: In the development of this thesis, a phase shifting technique was implemented in an experimental configuration of Digital In line Holographic Microscopy (DIHM) of common path, it was made using a liquid crystal waveplate located in a Point Diffraction Interferometer (PDI) and its effectiveness was verified through the calculation of the refraction index of translucid micro-objects. In this configuration liquid crystal waveplate act like a rotated retarder and has a electric hole in its center where emerges a spherical wave. Through the application of a potential difference, controlled phase changes are induced over the entire screen area except in the hole region; this is a digital phase shifting system. The traslucid object, which will be studied, is illuminated by a coherent light source and the field transmitted by this object hits over the screen, which will behave as object beam. The spherical wave that emerges from the small hole will be behaved as a reference beam, forming an architecture of digital in line holography microscopy with the possibility to create digital phase shifting over the object beam, which allow to quantify the phase difference between the waves (object and reference), through the similary phase shifting used by Yamaguchi. Previously to phase quantification, it was performed a local calibration over the a liquid crystal waveplate the using of a polarimetric method, based on the physical properties of liquid crystals and Muller matrix, which allowed us to obtain a curve of phase variation in terms of potential difference applied, besides to check the homogeneity of the phase variation produced to the object beam.