Rough diffraction gratingsapplications to linear optical encoders

Résumé

ABSTRACT In this Thesis work we present theoretical, numerical and experimental analyses of the behavior of non-perfect diffraction gratings. We have performed an analysis of diffraction gratings engraved on a steel tape. This kind of gratings can be found in industrial devices such as optical encoders for long range measurements (> 3 m). The main objectives of this Thesis work are to find a theoretical formalism which describes the behavior of this kind of gratings in near and far field approac hes. We also propose a new kind of diffraction grating based on periodical variations in the micro-topographic properties of the surface. Besides, we analyze other kind of imperfections in gratings like rough edges, which can be produced during the f abrication process. Another important result is the cancellation of Talbot effect using masks formed by two gratings. This Thesis work has been motivated by a long collaboration with private industry related with fabrication of high accuracy metrolog y systems.