Patent ID: 8691712

Claim:
An optical glass comprising, by mass on oxide basis: SiO 2 more than 1.0% and less than 12.0%, B 2 O 3 8.0 to 35.0%, the ratio of SiO 2 /B 2 O 3 being more than 0 and less than 0.6, and La 2 O 3 25.0 to 50.0%, wherein the product of α and β, where α is an average linear expansion coefficient within -30° C. to +70° C. and β is an optical elasticity constant at the wavelength of 546.1 nm, is not more than 130×10 −12 ° C. −1 ×nm×cm −1 ×Pa −1 , and wherein the ratio of (Ta 2 O 5 +Nb 2 O 5 +WO 3 )/(Gd 2 O 3 +Y 2 O 3 ) is more than 0.05 and less than 1. 30, wherein the glass has optical constants within the rages where the refractive index (nd) is 1. 75 to 2.00 and the Abbe's number (νd) is 35 to 55.