Determination of the asphericity degree of a transparent reference sphere with a vectorial shearing interferometer

We examine the viability of implementing the Vectorial Shearing Interferometer (VSI) in order to determine the sphericity of a glass standard patron. We use the patron sphere as an optical component to collimate the expanded wave front of a laser. The collimated wave front impinges on the VSI. The resulting fringe pattern carries the phase gradient information of the original wave front, in the sheared direction. We estimate qualitatively the asphericity of the element under test, comparing the phase gradients in different sections of the sphere. When the gradients of two or more directions are identical, we consider that the standard patron has uniform sphericity. Here, we report on the experimental setup to test the asphericity, the experimental results, and perform comparison with theoretical calculations.