Positioning unit and apparatus for adjustment of an optical element

A positioning unit for an optical element in a microlithographic projection exposure installation having

• a first connecting area A for connection to the optical element (8), and
• a second connecting area B for connection to an object in the vicinity of the optical element,
• at least two levers (27, 32),
• which are connected via their respective lever bearings (45a, 45b) to the second connecting area B, and
• whose respective load arm (27b, 32b) is connected by means of a hinged joint (46a, 46b) and via an intermediate element C, which acts on this hinged joint, to the first connecting area A, having
• adjustment devices or actuators (28, 29, 34, 35) arranged on the respective force arms (27a, 32a) of the levers (27, 32)
• in which, in a first position, the first connecting area A and the second connecting area B are arranged relative to one another such that the lever bearings (45a, 45b) of the at least two levers (27, 32) and the hinged joints (46a, 46b) which are associated with these levers have approximately parallel rotation axes,
• which lie approximately on one plane in the first position.