Abstract: An X-ray lithography optical system has an elongated concave scanning mirror spaced a first predetermined distance from a source of X-rays. The mirror has a reflecting surface of part toroidal configuration having a first radius of curvature coincident with that of a torus of which the mirror is part and spaced opposite first and second ends having a second radius of curvature, different from the first radius of curvature, coincident with that of the circle which generates the torus. A photoresist is spaced a second predetermined distance from the mirror and positioned to receive X-rays reflected by the mirror. The second predetermined distance is greater than the first predetermined distance. A mask in proximity with the photoresist permits a predetermined pattern of X-rays to impinge on the photoresist and blocks all other X-rays.