| 摘要 |
PURPOSE:To obtain a distributed index lens having a larger angular aperture and superior chemical durability as compared with a conventional distributed index lens made of an Li-contg. glass compsn. by adopting a specified glass compsn. CONSTITUTION:This glass compsn. for a distributed index lens consists of, by mol., 3-22% Li2O, 0-20% Na2O, 0-20% K2O (Na2O+K2O=3-20%), 0-20% Al2O3, 0-25% B2O3, 2-25% TiO2, 40-62% SiO2, 3-10% ZrO2, 0-20% GeO2 (Al2O3+B2O3+TiO2+SiO2+ZrO2+GeO2=55-70%), 0-20% MgO, 0-15% PbO, 0-10% SnO2, 0-10% Ta2O5 and 0-10% Nb2O5.
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