A one-dimensional two-stage focusing system using two deformable mirrors was constructed. To realize the precise
elliptical shapes, the mirror deformations were finely adjusted using the pencil-beam scan, which is a method of
wavefront measurement. X-rays of 10 keV energy were one-dimensionally focused to a full width at half maximum of
90 nm, which agrees well with the diffraction limit.
To construct an adaptive X-ray focusing optical system, we developed an ultraprecise deformable mirror that consists of a substrate, piezoelectric actuators, and 18 electrodes. A one-dimensional focusing test was performed at SPring-8 at 15 keV. The mirror deformation was roughly adjusted by applying voltages determined by a deformation test with a Fizeau interferometer. The shape was then finely corrected based on the shape determined by the pencil-beam method and the phase retrieval method. A focused beam with a full width at half maximum of 120 nm was obtained.