LIGHT-CONDUCTING GLASS STRUCTURE HAVING A PERIPHERAL LIGHT-ABSORBENT LAYER

摘要

A transparent glass body having a light-focusing effect and a refractive index decreasing progressively from its centerline outward and containing readily reducible metal oxides in at least the outer peripheral part thereof is caused to contact a gas having a reducing effect thereby to reduce the metal oxides and form a light-absorbent layer of metal colloid in the outer peripheral part.