Interferometer that measures aspherical surfaces

Abstract

A method of manufacturing a projection optical system ( ) for projecting a pattern from a reticle to a photosensitive substrate, comprising a surface-shape-measuring step wherein the shape of an optical test surface ( ) of an optical element ( ) which is a component in the projection optical system is measured by causing interference between light from the optical surface ( ) and light from an aspheric reference surface ( ) while the optical test surface ( ) and said reference surface ( ) are held in integral fashion in close mutual proximity. A wavefront-aberration-measuring step is included, wherein the optical element is assembled in the projection optical system and the wavefront aberration of the projection optical system is measured. A surface correction calculation step is also included wherein the amount by which the shape of the optical test surface should be corrected is calculated based on wavefront aberration data obtained at the wavefront-aberration-measuring step and surface shape data obtained from the surface-shape-measuring step. The method also includes a surface shape correction step wherein the shape of the optical test surface is corrected based on calculation performed at the surface correction calculation step. Surface shape measuring interferometer systems and wavefront-aberration-measuring interferometer systems ( J- Q) used in performing the manufacturing method are also disclosed.