OPTICAL GLASS, PREFORM, AND OPTICAL ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide optical glass that has excellent transparency-loosing resistance that exhibits both a high refractive index (nd) and logarithm log&eegr; of viscosity &eegr; (dPa s) at a sufficient liquid phase temperature and is capable of easily manufacturing a preform material and optical element by polishing processing, and preform using the same.SOLUTION: Optical glass include: 75.0% or more and 98.0% or less of a BiOcomponent in terms of mass% of oxide; more than 0% and less than 10.0% of a NbOin terms of mass% of oxide; and more than 0% and less than 10.0% of a ZnO component in terms of mass% of oxide.