摘要:
This invention provides an anomalous dispersion glass exhibiting an .eta. d value of 1.54-1.71 and an.nu. d value of 55-30, and the anomaly of a partially dispersing property in the long wave length region. The anomalous dispersion glass contains B.sub.2 O.sub.3 45-70 mol.%; Pb0 5-30 mol.%; Na.sub.2 O 1-15 mol.%; SiO.sub.2 0-10 mol.%; Al.sub.2 O.sub.3 5-25 mol.%; one or more of CaO, BaO, MgO and CdO 0-16 mol.%, and one of TiO.sub.2, ZrO.sub.2, Sb.sub.2 O.sub.3, Wo.sub.3 and Tl.sub.2 O 0-3 mol.%. Fluorine may be present in an amount such that the F/O ion ratio in the resulting glass lies in the range of 0-0.35.