Patent ID: 7166163

Claim:
A method of manufacturing an optical member, the method comprising: a crystal growing step of melting a mixture of fluoride powder and a scavenger at a melting temperature of a melting point for a fluoride and above, and then crystallizing a melted fluid and further cooling down an obtained fluoride crystal in a temperature range from 1000° C. to 900° C. by a temperature decreasing rate in a range from 0.1 to 5° C./hr; and a carving step of carving an optical member out of the fluoride crystal obtained in the crystal growing step such that the optical member is made of a fluoride crystal in which a maximum diameter d max of scattering bodies existing internally and a quantity n s of the scattering bodies per 1 cm 3 satisfy a condition represented by the following formula (1): 0< d max 2 ×n s <6.5×10 −4 (cm −1 ) (1).