CaF2 LENS REDUCED IN DOUBLE REFRACTION

摘要

PROBLEM TO BE SOLVED: To improve the double refraction and uniformity of a lens in a preparation method of an optical lens suitable for an optical lithographic device using electronic radiation of a selected wavelength.;SOLUTION: An optical crystal disk has a selected crystal orientation, and the disk is suitable to use for the electromagnetic radiation of the selected wavelength, and the disk has a top face, a bottom face and thickness. The crystal orientation of the optical crystal material is measured in both of the top face and the base face of the disk, and the measured values are compared with the selected crystal orientation. The optical crystal material is trimmed from one or both sides of the surfaces so that the quantity of the optical material having the minimum inclination with the selected crystal orientation may become the maximum.;COPYRIGHT: (C)2005,JPO&NCIPI