Beam control apparatus for an illumination beam and metrology system comprising an optical system containing such a beam control apparatus

A beam control apparatus for an illumination beam includes an imaging illumination optical unit assembly for imaging an intermediate focus of the illumination beam onto an object field to be illuminated. A control component that influences a beam path of the illumination beam is displaceable in at least one degree of freedom by at least one displacement actuator. A position sensor device of the beam control apparatus detects a position of the intermediate focus. A control device of the beam control apparatus is signal-connected to the position sensor device and the displacement actuator. From an intermediate focus position signal received from the position sensor device, the control device calculates control signals for the displacement actuator and forwards the latter to the displacement actuator for controlling the position of the intermediate focus. This results in a beam control apparatus which makes well-controllable illumination possible together with a simple construction.