Method of manufacturing a glass body having a non-uniform refractive index

A method for manufacturing an elongate light transmissive optical glass body having a central axis and a cylindrical circumference, said elongate body having a non-uniform refractive index which decreases radially between said axis and said circumference, said method comprising the following steps:

• storing grains of at least two substances which yield glass having different refractive indices, in a respective at least two hoppers, said grains having diameters in the range of 0.01 .mu.m to 1 mm,
• mixing said grains in a desired proportion which will provide said non-uniform refractive index by controlled feeding into a common feed line having a pouring spout for pouring the mixed grains therefrom,
• pouring said grains onto a support while rotating said support about a vertical axis of rotation,
• moving said pouring spout radially between said vertical axis and means defining a circumference at a fixed radius from said axis while rotating said support,
• moving said pouring spout vertically relative to said support while rotating said support,
• pouring said grains from said spout during at least one of moving said spout radially and moving said spout vertically, thereby forming a cylindrical granular body having an axis coincident with said axis of rotation, and
• heat fusing the granular body to form said light transmissive cylindrical glass body.