Optical glass, preform, and optical element

Abstract

Provided are an optical glass that has optical properties including a medium refractive index and low dispersion and that has good chemical durability and a low specific gravity, and a preform material and an optical element that use the optical glass. The optical glass contains a SiO2 component: 0% or more and less than 30.0%; 8.0% to 30.0% of an Al2O3 component; less than 20.0% of an RO component (where R represents at least one selected from the group consisting of Zn, Mg, Ca, Sr, and Ba) in terms of a mass sum; and 10.0% to 55.0% of an Ln2O3 component (where Ln represents at least one selected from the group consisting of La, Gd, Y, and Lu) in terms of a mass sum. A mass ratio (SiO2+Al2O3)/B2O3 is 0.3 to 10.0, and the optical glass has a refractive index (nd) of 1.58 or more and 1.80 or less and an Abbe number (νd) of 35 or more and 65 or less.

Dependencies are inferred from the claim text.