Patent ID: 6977232

Claim:
An optical glass comprising, as essential components, 25 to 45 mol % of B 2 O 3 , 0.5 to 20 mol % of SiO 2 , 5 to 22 mol % of La 2 O 3 , 2 to 20 mol % of Gd 2 O 3 , 15 to 29 mol % of ZnO, 1 to 10 mol % of Li 2 O and 0.5 to 8 mol % of ZrO 2 , as optional components, 0 to 8 mol % of Ta 2 O 5 , 0 to 8 mol % of WO 3 , 0 to 8 mol % of Nb 2 O 5 , 0 to 8 mol % of Y 2 O 3 , 0 to 8 mol % of Yb 2 O 3 and, as an anti-foaming agent, 0 to 1 mol % of Sb 2 O 3 , the essential components and the optional components having a total content of at least 95 mol %; the optical glass having a B 2 O 3 /SiO 2 molar ratio of from 2 to 5.5 and having an La 2 O 3 and Gd 2 O 3 total content of 12 to 24 mol % and a ZnO and Li 2 O total content of 25 to 30 mol %, the optical glass having a refractive index (nd) of 1.75 to 1.85 and an Abbe's number (vd) of 40 to 55.