Projection objective including an optical device

An apparatus, comprising:

• a projection objective, comprising:
• an optical device;
• a controller;
• and
• temperature sensors,
• wherein:
• the optical device comprises an optical element and an electrostrictive actuator;
• the optical element comprises an optically effective surface;
• the optical element is adjacent an intermediate image plane of the apparatus;
• the controller is configured to provide a control voltage to the electrostrictive actuator to deform the electrostrictive actuator;
• the electrostrictive actuator is connected to the optical element to influence a surface shape of the optically effective surface;
• the temperature sensors are configured to measure:
• a) a temperature of the electrostrictive actuator;
• b) a temperature change of the electrostrictive actuator;
• c) a temperature distribution of the electrostrictive actuator;
• d) and/or a temperature distribution of surroundings of the electrostrictive actuator;
• the temperature sensors are configured so that, at least at times when the electrostrictive actuator influences the optically effective surface of the optical element, the temperature sensors determine:
• a) the temperature of the electrostrictive actuator;
• b) the temperature change of the electrostrictive actuator;
• and/or c) a temperature of the surroundings the electrostrictive actuator, thereby taking account of a temperature-dependent influence when the electrostrictive actuator is driven by the control device;
• and
• the apparatus is a projection exposure apparatus.