GLASS PREFORM COMPOSITION FOR DISTRIBUTED REFRACTIVE INDEX TYPE LENS

摘要

PROBLEM TO BE SOLVED: To provide a glass preform composition for a distributed refractive index type lens which has a low dispersion and affords an aperture angle of 13 degree or more. SOLUTION: By adding La2 O3 and ZnO to the SiO2 -TiO2 -Li2 O-Na2 O-MgO-BaO based glass which does not contain a lead oxide, the composition region for the glass preform for distributed refractive index type lens is obtained, which preform has a desired refractive index and is less prone to be devitrified.