Diseño de un interferómetro panorámico de moteado y su aplicación en la medición de desplazamientos

Abstract

RESUMEN: Las técnicas ESPI, Interferometría de patrones de moteado electrónico Holografía digital son técnicas de metrología óptica que basan su funcionamiento en una característica propia de la iluminación coherente, el moteado. Este fenómeno, inicialmente considerado un problema es ahora utilizado como una poderosa herramienta para detectar deformaciones y desplazamientos micrométricos. El moteado depende fuertemente de la rugosidad superficial del objeto que se está midiendo, por lo que objetos con rugosidad baja resultan complicados de medir. ABSTRACT: ESPI techniques, Electronic Speckle Pattern Interferometry or Digital Holography, are optical metrology techniques based their operation on a characteristic of light coherent, the speckle. This phenomenon,initially considered a problem is now used a powerful tool to detect deformations and displacements micrometers. Speckle strongly depends on object's superficial rugosity that is measurement, as a consequence, objects with low roughness are dificult to measure. As any optical technique, ESPI is neither invasive and nor destructive. ESPI techniques were originated in speckle techniques which used photographic film, the development of CCD cameras and of course, computers (which is why they are called Electronic Speckle Pattern) allowed the rapid evolution of the first. In this work we propose an optical setup which is capable of generating panoramic ESPI images. In our system, panoramic images refer to those which present information on a field of view of 360 o. Around the capture device. This kind of ESPI technique can be used to test objects having a cylindrical shape or several objects in a single specklegram. Avoiding the need of taking several images and then composing a panoramic view. The panoramic interferometer is based on a panoramic visión system with convex mirror, particularly a paraboloidal mirror. A second and symmetric paraboloidal mirror is used to complete the ESPI technique.The system can be seen as composed of two modules, illumination and capture, each one needs a paraboloid mirror.To show its capabilities the panoramic interferometer presented is used to detect micro displacements in a cylindrical test object. The technique show sinsensibility in one direction which must be explained through the no yet developed physical model. Several images for the two other displacement directions are shown. Correlation fringes obtained are an indication of the feasibility of the proposal, which can be positively applied to the inspection of cylindrical objects using a single panoramic image.