| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical glass having a small Abbe number (&ngr;), a small partial dispersion ratio (&thetas;g,F) and enhanced transparency to visible light while having a desired range of a refractive index (n), and to provide a preform and an optical element using the optical glass.SOLUTION: The optical glass comprises, on a mass% basis, a BOcomponent by 5.0% or more and 40.0% or less, a LnOcomponent (where Ln represents at least one element selected from the group consisting of La, Gd, Y and Yb) by 15.0% or more and 60.0% or less in terms of the mass sum, and a NbOcomponent by over 0% and 50.0% or less; and the optical glass has a partial dispersion ratio (&thetas;g,F) satisfying the relationship of (-0.00162×&ngr;d+0.63822)≤(&thetas;g,F)≤(-0.00275×&ngr;d+0.68125) with an Abbe number (&ngr;d) in the range of &ngr;d≤31, and satisfying the relationship of (-0.00162×&ngr;d+0.63822)≤(&thetas;g,F)≤(-0.00162×&ngr;d+0.64622) with the Abbe number in the range of &ngr;d>31. |
