| 摘要 |
The optical glass of the present invention has optical constants of a refractive index (nd) within a range from 1.74 to 1.80 and an Abbe number (? d) within a range from 47 to 51, contains, as essential components, SiO<SUB>2</SUB>, B<SUB>2</SUB>O<SUB>3</SUB>. La<SUB>2</SUB>O<SUB>3</SUB>, Gd<SUB>2</SUB>O<SUB>3</SUB>, ZrO<SUB>2</SUB>, Ta<SUB>2</SUB>O<SUB>5</SUB>, ZnO and Li<SUB>2</SUB>O, is substantially free of Pb, As and F, and contains ZrO<SUB>2</SUB> in an amount of 6 mass % or less. The optical glass has ratio of ZnO/(ZrO<SUB>2</SUB> + Ta<SUB>2</SUB>O<SUB>5</SUB>) within a range from 0.45 to 1.5 and glass transition temperature (Tg) within a range from 530 °C to 630 °C. |
