| 摘要 |
A glass composition suitable for producing a graded-refractive-index rod lens having an angular aperture of 16-20° without containing lead or thallium and a graded-refractive-index rod lens produced from the composition are provided. The composition is a base glass composition for graded-refractive-index rod lenses, characterized by comprising, in terms of % by mole, 20<=SiO2<=52, 1<=B2O3<=30, 12<=Li2O<=18, 8<=Na2O<=15, 0<=MgO<=15, 0<=SrO<=10, 0<=BaO<=10, 0<=ZnO<=15, 0<=TiO2<=15, 0<=Nb2O5<=5, 0<=Ta2O5<=5, and 3<Bi2O3<=13, provided that 45<=SiO2+B2O3<=65, 9<=MgO+ZnO+TiO2<=25, and 0<=Nb2O5+Ta2O5<=5, and by containing substantially no lead and substantially no thallium.
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