Patent ID: 8377835

Claim:
An optical glass comprising, in terms of mass % on the basis of oxides: B 2 O 3 : 10 to 20%, SiO 2 : more than 2 to 12%, ZnO: 5 to 19%, Ta 2 O 5 : 2.5 to 17%, Li 2 O: 0.2 to 3%, ZrO 2 : 0.6 to 4.9%, WO 3 : 1 to 20%, La 2 O 3 : 25 to 50%, Gd 2 O 3 : 0 to 13%, and Y 2 O 3 : 0.2 to 20%, provided that La 2 O 3 +Gd 2 O 3 +Y 2 O 3 is 35 to 60%, wherein the optical glass does not substantially comprise Nb 2 O 5 , and has a refractive index (n d ) of 1.82 to 1.86, an Abbe's number (ν d ) of 37 to 44 and a glass transition point (T g ) of 630° C. or lower.