| 摘要 |
PROBLEM TO BE SOLVED: To shorten an annealing time for releasing a gradient refractive index and a stress during manufacturing procss such as a molding process without impacting to an optical property of an optical glass element. SOLUTION: A cooling rate of an annealing from a maximum temperature of heating a formed optical glass element is adjusted between 20 deg.C and 50 deg.C per hour. And the maximum temperature of an annealing furnace is kept above a distortion temperature of a nitrate material to be annealed and below an annealing temperature; furthermore a retention time of the maximum temperature is kept from 5 minutes to an hour.
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