ACTUATION MECHANISM, OPTICAL APPARATUS, LITHOGRAPHY APPARATUS AND METHOD OF MANUFACTURING DEVICES.

摘要

An actuator to displace, for example a mirror, provides movement with at least two degrees of freedom by varying the currents in two electromagnets (370). A moving part includes a permanent magnet (362) with a magnetic face constrained to move over a working area lying substantially in a first plane perpendicular to a direction of magnetization of the magnet. The electromagnets have pole faces lying substantially in a second plane closely parallel to the first plane, each pole face substantially filling a quadrant of the area traversed by the face of the moving magnet. A ferromagnetic shield (820) is provided around the moving part and has at least one interruption (822) to reduce the influence of adjacent actuators or stray fields whilst also minimizing attraction between the permanent magnet (362) and the shield (820).