Patent ID: 7884041

Claim:
An optical glass, comprising in mass % SiO 2 more than 5% and 20% or below, B 2 O 3 5% to less than 20%, Y 2 O 3 more than 5% and 35% or below, La 2 O 3 10-50%, ZnO around 5% to less than 25%, and Li 2 O more than 1% and 6% or below, wherein a ratio of SiO 2 /B 2 O 3 is 0.30 to 1.55 and a ratio of Y 2 O 3 /La 2 O 3 is 0.15 to 1.00, wherein the optical glass is substantially free of lead component, arsenic component and fluorine component, wherein the optical glass has a glass transition temperature (Tg) of 620° C. or below, optical constants of a refractive index (nd) within a range from 1.73 to less than 1.80 and an Abbe number (νd) within a range from 43 to 55.