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随着天文科学、空间科学及国防事业的发展,大尺寸光学玻璃毛坯的需求日增。为保证制品光学表面的加工精度,保证仪器在长期使用中的成象质量,必须提高光学元件的尺寸稳定性。为此,要求能提供残余应力低、分布均匀的玻璃毛坯。苏联1976年发表的φ6米×0.9米的天文镜制造工艺资料,要求毛坯中心应力双折射低于5毫微米/厘米,边缘值低于20毫微米/厘米;德国肖特
With the development of astronomy, space science and national defense, there is an increasing demand for large-size optical glass blanks. In order to ensure the processing accuracy of the optical surface of the product and to ensure the image quality of the instrument during long-term use, the dimensional stability of the optical element must be improved. For this reason, it is required to provide a glass blank having a low residual stress and a uniform distribution. The φ6 m × 0.9 m astronomical mirror manufacturing process data published by the Soviet Union in 1976 required that the stress birefringence at the center of the blank be less than 5 nm / cm and the edge value be less than 20 nm / cm;