DIFFRACTIVE OPTICAL ELEMENT, METHOD OF FABRICATING THE ELEMENT, ILLUMINATION DEVICE PROVIDED WITH THE ELEMENT, PROJECTION EXPOSURE APPARATUS, EXPOSURE METHOD, OPTICAL HOMOGENIZER, AND METHOD OF FABRICATING THE OPTICAL HOMOGENIZER

摘要

A diffractive optical element efficiently converts an input light beam into an output light beam having a specified cross-sectional shape. The diffractive optical element includes a plurality of partial optical elements. The plurality of partial optical elements convert the input light beam to respective partial light beams, each of which has a shape that does not correspond to the specified cross-sectional shape. The sum of the partial light beams matches the shape of the output light beam (i.e., having the specified cross-sectional shape).