A refractive projection objective for use in microlithography with lenses made
exclusively of one and the same material has an image-side numerical aperture larger
than 0.7. A light bundle defined by the image-side numerical aperture and by the
image field has within the objective a variable light-bundle diameter smaller than
or equal to a maximum light-bundle diameter. In a length interval measured on the
optical axis from the system diaphragm towards the object field and at least equaling
the maximum light-bundle diameter, the variable light-bundle diameter exceeds 85%
of the maximum light-bundle diameter.
