Patent ID: 7572746

Claim:
An optical glass having optical constants of refractive index (nd) within a range from 1.49 to 1.54 and Abbe number (ν d) within a range from 55 to 65 and comprising, in mass %, SiO 2 >65-75% R 2 O (R is at least one selected from the group 15-25% consisting of Li, Na, K and Cs) where Li 2 O 0.1-5.0% Na 2 O 1.0-10.0% K 2 O 12.6-20.0% and Cs 2 O 0-5.0% R′O (R′ is at least one selected from the group 0.5-10% consisting of Mg, Ca, Sr and Ba) where MgO 0-10% and/or CaO 0-10% and/or SrO 0-10% and/or BaO 0-10% B 2 O 3 0-6.0% and/or Al 2 O 3 0-<1.0% and/or TiO 2 0-1.69% and/or ZrO 2 0-2.0% and/or WO 3 0-3.0% and/or Sb 2 O 3 0-2.0% and and comprising no ZnO or F except for an impurity mixed by inevitable mixing.