Common-path speckle interferometer for phase objects studies

A very stable and robust schema for electronic speckle pattern interferometry configured to be sensible out-of-plane for studying phase objects is presented. It is based on a 4f imaging optical system, consisting of two windows in the object plane and a Ronchi ruling in the Fourier plane. One of the windows attends as a reference and the other acts as a probe arm. The speckle effect is created when a ground glass diffuser is placed in the object plane. Phase stepping is achieved out by Ronchi ruling translation, which is operated manually and validated with the Carré method. Analytic explanation and experimental results are shown.