Interferometric grazing incidence test of rough steep convex spherics: experimental data analysis

Grazing incidence interferometry has been applied to plane, cylindrical, acylindrical, and general rod-like surfaces using diffractive beam splitters. Here, in a first step towards measuring aspherics, we demonstrate that also rough convex steep rotationally symmetric spherics can be measured along one meridian in a single step using diffractive beam splitters and phase shifting techniques. The measurement of rough surfaces is possible, i.e., without the need to polish the surfaces, due to the large effective wavelength (lambda(eff) approximate to 10 mu m) of the test. We include, besides the short recapitulation of the measurement principle and experimental setup, a presentation of the measured data of one small meridian region for the special case of spherical objects under test. The subsequent data analysis combined with suitable simulations focuses on elimination of the misalignment aberrations from the results caused by specimen displacements in the setup. (C) 2020 Optical Society of America

Automated summary

By utilizing diffractive beam splitters and phase shifting techniques, rough convex steep rotationally symmetric spherics can be measured along one meridian in a single step without the need for polishing the surfaces, thanks to the large effective wavelength of the test.