Implementación de un microscopio perfilométrico por interferometría óptica.

Abstract

Interferometric microscopy is a well-known technique in the study of topographies of objects. In this work the design and construction of a profilometric microscope by polychromatic light interferometry and by quasi-monochromatic light interferometry, which allows the topographic survey of objects with nanometric resolution, is presented. The system consists of a 10X Mirau interferometric lens, a CMOS-type digital camera, a piezoelectric translation system with a resolution of 0.1nm and a white LED lighting system and for the adaptation of the device to quasi-monochromatic light, a 647nm band pass filter is used. For polychromatic light, by means of an axial scan of the object, a set of images is acquired with a system of distorted interferometric strips which give information about the roughness of the object. The principle of the system is based on the location of the coherence peak in each position Im(i, j) of the set of m acquired images, where the z (m) position of the coherence peak changes according to the topography of the object. To calculate the coherence peak, several algorithms are implemented, such as the calculation of the minimum interferogram minimum {Im (i, j)}, the calculation of the maximum of the envelope and the location of the interferogram center by analyzing the phase by Fourier transform. When the band pass filter is adapted, the source can be considered a quasi-monochromatic source, for this case the techniques of Phased Shifting to 3 and 4 images are implemented, which considerably reduces the number of images to acquire, therefore the cost computational It presents a series of three-dimensional reconstructions of several objects at nanometric resolution, obtained automatically with the help of a graphical interface developed in Matlab, which allows the control of the devices, digital processing of the images and the calculation of the topography of the object .