Comparison between the scanning pentaprism and the Hartman method for wavefront analysis

Abstract

Techniques for wavefront measurement have many applications as optics systems for astronomy and as verification tests for optical surfaces. The development of large aperture optical systems drives the search for low cost and high-resolution wavefront detection sensors. The Hartman technique and its variations (i.e the Shack-Hartman sensor) are the current standards for the characterization of low-order optical aberrations, such as defocus and spherical. The scanning pentaprism method is presented as a simple and low-cost method for the verification of such aberrations. In this method, a transverse section of a wavefront is scanned and sampled into a series of sub-wavefronts with smaller apertures. The relative positions of the produced centroids are measured relative to a calibrated position. This allows for the determination of the optical path difference along the section and consequently the wavefront error. Both techniques were used as tools for collimating a telescope that is part of the on-ground support equipment of ESA PLATO mission. In this work, the results from both methodologies are compared.