There is provided a collector for illumination systems for light having a wavelength .ltoreq.193 nm comprising. The collector includes (a) a first mirror shell adjacent to, and positioned inside of, a second mirror shell around a common axis of rotation, in which the first and second mirror shells are rotationally symmetric, and (b) a component in a region between the first and second mirror shells. The collector is for receiving the light from a light source via an object-side aperture and for illuminating an area in an image-side plane, and the region is not used by the light.