Patent ID: 7397535

Claim:
A lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being constructed to impart a cross-sectional pattern to the radiation beam to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; an adjustable aperture, located upstream of the illumination system in the path of the radiation beam, configured to permit propagation of the radiation beam from a radiation source to the illumination system; a beam expander, located upstream of the illumination system in the path of the radiation beam, configured to change the size and divergence of the radiation beam; a detector configured to detect the size and divergence of the radiation beam propagated through the aperture and to provide a feedback signal in dependence thereon; an actuator configured to effect adjustment of the beam expander, or the aperture, or both the beam expander and the aperture, to vary at least one optical characteristic of the radiation beam; and a control device configured to control the actuator in response to the feedback signal from the detector.