Fluorophosphate optical glass

Abstract

A fluorophosphate optical glass having optical constants, i.e. refractive index (nd) of 1.54 to 1.60 and Abbe number (.nu.d) of 68 to 75 and having abnormal partial dispersion represented by a relative partial dispersion of at least 0.537 is provided, which has a chemical composition (% by weight) comprising: ______________________________________ Al(PO.sub.3).sub.3 15-32% Ba(PO.sub.3).sub.2 0-10% Sr(PO.sub.3).sub.2 0-10% Ca(PO.sub.3).sub.2 0-10% Mg(PO.sub.3).sub.2 0-10% sum of metaphosphates 20-32% BaF.sub.2 20-70% SrF.sub.2 5-40% CaF.sub.2 0-15% MgF.sub.2 0-10% AlF.sub.3 0-5% GdF.sub.3 0-5% sum of fluorides 55-75% Gd.sub.2 O.sub.3 5-22% La.sub.2 O.sub.3 0-7% Y.sub.2 O.sub.3 0-10% Yb.sub.2 O.sub.3 0-10% sum of rare earth oxides 5-22% ______________________________________

Dependencies are inferred from the claim text.