Patent ID: 8207076

Claim:
An optical glass comprising, in terms of % by mass on the oxide basis: more than 1.0% and less than 12.0% of SiO 2 , from 8.0 to 35.0% of B 2 O 3 , from 25.0 to 50.0% of La 2 O 3 , more than 13% and less than 20% of (ZrO 2 +Nb 2 O 5 ), less than 2.0% of ZnO, 0 to 3.0% of Y 2 O 3 , and 0 to 2.0% of TiO 2 , wherein a (Ta 2 O 5 +Nb 2 O 5 +WO 3 )/(Gd 2 O 3 +Y 2 O 3 ) ratio is more than 0.05 and less than 1.30 in terms of % by mass on the oxide basis, the optical glass has an absolute value of a product (α×β) is not more than 130×10 −12 ° C. −1 ×nm×cm −1 ×Pa −1 , where α is an average coefficient of linear expansion at from −30 to +70° C. and β is a photoelastic constant at a wavelength of 546.1 nm, and the optical glass has optical constants of a refractive index (nd) in the range of from 1.75 to 2.00 and an Abbe's number (vd) in the range of from 35 to 55.