Patent ID: 7989377

Claim:
An optical glass comprising as cationic components, by cationic %, 20 to 50% of P 5+ , 0.1 to 20% of Al 3+ , 0.1 to 20% of Mg 2+ , 0 to 20% of Ca 2+ , 0 to 20% of Sr 2+ , 0.1 to 30% of Ba 2+ and 0 to 10% of Y 3+ , and further comprising, as anionic components, F − and O 2− , wherein the ratio of the content of Mg 2+ to the content of Al 3+ , Mg 2+ /Al 3+ , based on cationic %, is 1.2 or less, wherein the total content of P 5+ , Al 3+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Y 3+ and La 3+ is 100%, and wherein the ratio of the content of Ba 2+ to the total content, R 2+ , of Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ , Ba 2+ /R 2+ , based on cationic %, is less than 0.5, the optical glass having a refractive index (nd) of 1.54 to 1.60, an Abbe's number (vd) of 65 to 78, a partial dispersion ratio of 0.530 or more, a specific gravity of 4.0 or less and a viscosity, measured at its liquidus temperature, of 4 dPa·s or more.