Optical glass based on oxides of silicon, boron and lanthanum - having high index of refraction and low dispersion

摘要

Optical glass contains 51-74 mole % of (SiO2 + B2O3 + La2O3). The molar ratio SiO2:La2O3 is 0.33-0.66 (pref. 0.39-0.63, esp. 0.59); B2O3:La2O3 is 0.46-0.86 (pref. 0.50-0.74, esp. 0.59). Glass having high index of refraction (nD=1.84-1.95) and low Abbe number (nu d = 33-43) can be produced on industrial scale at a low cost. The prodn. is facilitated in that the compsn. does not much deviate from the eutectic point so that the fusion temp. is relatively low. The glass does not contain the objectionable thorium oxide (which is often used in commercial glasses having high index of refraction).