A catadioptric projection objective for images an object field onto an image field via imaging radiation. The projection objective includes at least one reflective optical component and a measuring device. The reflective optical component, during the operation of the projection objective, reflects a first part of the imaging radiation and transmits a second part of the imaging radiation. The reflected, first part of the imaging radiation at least partly contributes to the imaging of the object field. The transmitted, second part of the imaging radiation is at least partly fed to a measuring device. This allows a simultaneous exposure of the photosensitive layer at the location of the image field with the imaging radiation and monitoring of the imaging radiation with the aid of the measuring device.