Patent ID: 7145634

Claim:
A lithographic apparatus comprising: (a) an illumination system configured to condition a radiation beam, the illumination system including a radiation beam uniformity adjuster configured to adjust the uniformity of the radiation beam, said radiation beam uniformity adjuster including i) a segment that is at least partly arranged in said radiation beam to block an amount of radiation of said radiation beam, said segment being mounted on a frame by a torsion bar; ii) an actuator configured to rotate said segment about an axis substantially parallel to a longitudinal axis of said torsion bar to change the amount of radiation of said radiation beam that passes by said segment, iii) a first magnetic member mounted on said torsion bar, said first magnetic member being configured to co-operate with a second magnetic member mounted on said frame to generate a position dependent torque about said longitudinal axis that is configured to at least partly compensate a torque exerted on said segment by said torsion bar, (b) a support structure configured to support a patterning device, the patterning device configured to pattern the radiation beam according to a desired pattern; (c) a substrate table configured to hold a substrate, and (d) a projection system configured to project the patterned radiation beam onto a target portion of said substrate.