| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat treatment method for synthetic quartz glass, by which quartz glass having a low birefringence value and optical homogeneity can be obtained, and to provide the synthetic quartz glass obtained by the method. SOLUTION: In the method, synthetic quartz glass is held at a constant temperature in a range of its strain point or more to its annealing point or below for 20 hours or more and then cooled. By this heat treatment method, the quartz glass which has the low birefringence value to light in the wavelength region of≤400 nm, especially to vacuum ultraviolet light of≤200 nm such as an F<SB>2</SB>excimer laser beam, or the like, and which has optical homogeneity, can be obtained. COPYRIGHT: (C)2004,JPO
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