METHOD FOR ACQUIRING OPTICAL MEMBER, OPTICAL MEMBER AND PROJECTION EXPOSURE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a method for acquiring an optical member by which a part with good transmittance can be acquired from an ingot and to provide an optical member acquired by the method and a projection exposure device which uses the optical member. SOLUTION: The method includes a process of cutting out a sample 2 for measuring the transmittance from a fluoride crystal ingot 1, measuring the sample so as to indirectly measure the transmittance at a plurality of positions in the fluoride crystal ingot 1 and obtaining the transmittance distribution in the fluoride crystal ingot 1, and a process of cutting out a raw material 3 from the part having the transmittance exceeding the referential transmittance in the measured fluoride crystal ingot 1.