Drive device, optical system and lithography apparatus

A drive device configured to drive a capacitive actuator to actual an optical element of an optical system, the drive device comprising:

• a drive unit coupled to the capacitive actuator via a first node, the drive unit configured to apply a drive voltage to the capacitive actuator to set a position of the capacitive actuator;
• a source controllable by an excitation signal and coupled to the first node to feed a time-dependent AC current signal into the first node so that an AC voltage arises at the capacitive actuator due to a superposition of the drive voltage and an AC voltage corresponding to a product of the AC current signal and an impedance of the capacitive actuator;
• a filter unit connected to an output of the capacitive actuator and configured to filter an output signal of the capacitive actuator;
• and
• a determining unit coupled to an output of the filter unit and configured to determine an impedance behaviour of the capacitive actuator depending on the filtered output signal, the determining unit configured to output the excitation signal to drive the source.