Patent ID: 6522392
Filing Date: 2003-02-18
Classification: G03F

Abstract:
A method of compensating rotationally non-symmetrical image defects in an optical system, the optical system comprising a microlithographic projection printing installation:a) having a light source; b) having an optical element, which ba) comprises at least one surface acted upon by radiation of the light source; and bb) the basic shape of which at least in the region of the at least one surface acted upon by radiation is substantially symmetrical relative to an axis of rotational symmetry, whereinc) the optical element (25) or its housing (6) is rotatably connected to a frame (7) by at least one bearing (8, 9, 10); d) an actuator (18) is provided, which sets at least one of the optical element (25) and its housing (6) in rotation about the axis of rotational symmetry; wherein e) the actuator (18) cooperates with a control device 923), which activates the actuator (18) at least temporarily during the period, when the optical element (25) is exposed to rumination, for rotation of the optical element (25); wherein the method has the following process steps:a) rotation of the optical element (25) through a specific angle of rotation; b) reverse rotation of the optical element (25) through a specific angle of reverse rotation.