Testing Grazing-Incidence Mirrors at Nearly Normal Incidence

An optical system that utilizes visible light at nearly perpendicular incidence has been invented for use in testing the surface figures of nominally axisymmetric (paraboloidal, ellipsoidal, or conical) mirrors designed to function at grazing incidence. Such mirrors can be used as the focusing optical elements of x-ray telescopes and x-ray cameras. As explained below, the present system offers advantages over prior systems used to test such mirrors.