Patent ID: 6989060

Claim:
A method of manufacturing a calcium fluoride crystal, said method comprising: mixing a raw material of calcium fluoride and a scavenger at a predetermined proportion to obtain a first mixture; refining the first mixture in a crucible to remove impurities; and fusing the refined mixture in a crucible to cause growth of calcium fluoride crystal having a transition density in the crystal that is not greater than 1×10 5 /cm 2 , and a dispersion of transition density inside an effective portion of the crystal in a range of ±5×10 4 /cm 2 ; wherein said method includes a baking process before refining the first mixture or a baking process after refining the first mixture but before fusing of the refined mixture or both, wherein said baking process is carried out as a separate process from the refining process and the fusing process, by using a porous baking crucible different from the refining crucible and the fusing crucible.