LENS SYSTEM, ESPECIALLY, PROJECTION LENS SYSTEM FOR SEMICONDUCTOR LITHOGRAPHY

摘要

PROBLEM TO BE SOLVED: To provide a lens system where a new error is not made after a lens is exchanged and recombined or which is recombined as a result so that the system can be recycled. SOLUTION: In the case of the lens system having many optical elements the same as lenses mounted in mounts combined with each other by an adjusting ring on a proper condition, especially, the projection lens system for semiconductor lithography, the internal mount of at least one of the optical elements intended to be removed and/or combined later is combined with an external mount by three-point attachment.