Objective (1, 601), in particular a projection objective for a microlithography projection apparatus, with first birefringent lenses (L108, L109, L129, L130) and with second birefringent lenses (L101-L107, L110-L128). The first lenses (L108, L109, L129, L130) are distinguished from the second lenses (L101-L107, L110-L128) by the lens material used or by the material orientation. After passing through the first lenses (L108, L109, L129, L130) and the second lenses (L101-L107, L110-L128), outer aperture ray (5, 7) and a principal ray (9) are subject to optical path differences for two mutually orthogonal states of polarization. The difference between these optical path differences is smaller than 25% of the working wavelength. In at least one first lens (L129, L130), the aperture angle of the outer aperture ray (5, 7) is at least 70% of the largest aperture angle occurring for said aperture ray in all of the first lenses (L108, L109, L129, L130) and second lenses (L101-L107, L110-L128). This arrangement has the result that the first lenses (L108, L109, L129, L130) have a combined material volume of no more than 20% of the combined total material volume of the first lenses (L108, L109, L129, L130) and second lenses (L101-L07, L110-L128).