In some embodiments, the disclosure provides an optical system, in particular an illumination system or a projection lens of a microlithographic exposure system, having an optical system axis and at least one element group including three birefringent elements each of which includes optically uniaxial material and having an aspheric surface, wherein a first birefringent element of the group has a first orientation of its optical crystal axis, a second birefringent element of the group has a second orientation of its optical crystal axis, wherein the second orientation can be described as emerging from a rotation of the first orientation, the rotation not corresponding to a rotation around the optical system axis by an angle of 90° or an integer multiple thereof, and a third birefringent element of the group has a third orientation of its optical crystal axis, wherein the third orientation can be described as emerging from a rotation of the second orientation, the rotation not corresponding to a rotation around the optical system axis by an angle of 90° or an integer multiple thereof.