| 摘要 |
<p>The invention relates to a projection objective of a microlithographic projection exposure apparatus, which serves to project an image of a mask which can be positioned in an object plane onto a light-sensitive coating which can be positioned in an image plane, wherein the projection objective has an optical axis (OA). To make it possible to use highly refractive crystal materials while at the same time limiting the negative effects of intrinsic birefringence, a projection objective according to one aspect of the invention comprises at least one lens (143, 255, 360, 470) which has at least one curved lens surface and is put together of at least four lens elements (143a-143d, 255a-255d, 360a-360d, 470a-470d) of intrinsically birefringent material which are arranged so that they follow each other in mutually adjacent relationship along the optical axis (OA), wherein the four lens elements are made up of two pairs of lens elements, wherein the two pairs have crystallographic cuts being different from each other, and wherein the lens elements of each pair have the same crystallographic cut and are arranged relative to each other with a rotary offset about the optical axis (OA).</p> |
