Abstract: A method for performing a tilted focus test includes the steps of providing a target object, providing a projection beam of radiation using a radiation source, providing a reflective device to introduce a projected projection beam of radiation onto the target portion, introducing a first projected projection beam of radiation onto the target object using the reflective device in a first orientation, using a tilting device for tilting the reflective device to a second orientation to provide a second projection beam with a tilt relative to said first projection beam, introducing a second projected projection beam of radiation onto the target object, and determining a lateral shift of the first and second projected projection beams on the target object and determining from said lateral shift a defocus of the target object with respect to the projected projection beam.

Abstract: A lithographic apparatus includes a measurement system including at least one optical component and at least one electrical component. The electrical component is configured to dissipate heat. The optical component is mounted on a first frame of the apparatus, and the electrical component is mounted on a second frame of the apparatus that is thermally and mechanically decoupled from the first frame. An optical coupling is provided between the first frame and the second frame.