Wavelength plate unit producing method for e.g. microlithographic projection illumination system, involves forming plates from materials with different refractive indexes, where one of plates causes predominant portion of phase difference

摘要

The method involves arranging plates (1, 2) e.g. lenses, such that the plates are successively irradiated by a light beam to be treated through a wavelength plate unit, so that the plates produce a phase difference in an optical birefringent material. One of the plates is formed from a material e.g. silicon dioxide, with a refractive index, and another plate is formed from another material e.g. calcium difluoride, with another refractive index. The former index is larger than the latter index, where the former plate causes a predominant portion of the phase difference. An independent claim is also included for a microlithographic projection illumination system comprising an illumination system and/or a projection lens.