Anomalous dispersion glass exhibiting the anomalous partially dispersing property in the long wave length region

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 B2O3 45-70 mol.%; Pb0 5-30 mol.%; Na2O 1-15 mol.%; SiO2 0-10 mol.%; Al2O3 5-25 mol.%; one or more of CaO, BaO, MgO and CdO 0-16 mol.%, and one of TiO2, ZrO2, Sb2O3, Wo3 and Tl2O 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.