A device for improving resolution capability of an x-ray optical apparatus for an x-ray incident from a direction of incidence includes a mirror element including a mirror edge formed as a cylindrical shell section around an edge axis. The mirror element is spaced apart, in a radial direction, from a focal axis that is parallel to the direction of incidence. The edge axis is oriented at a first non-zero angle relative to the focal axis when viewed along a radial axis. The edge axis is oriented at a second non-zero angle relative to the focal axis.