| 摘要 |
PURPOSE:To provide a method for obtaining a trasparent glass preform free from outer diameter change, in the production of the transparent glass preform by heating a porous glass preform. CONSTITUTION:A porous glass preform is gradually introduced into a heating furnace to be converted to a transparent glass from the end part. As the weight of the generated transparent glass part is increased by gradual proceeding of the conversion to the transparent glass, the temperature of the heater is gradually lowered so as to increase the viscosity of the preform passing through the heater unit. The expansion of the preform is kept constant thereby and the outer diameter of the preform can be kept constant. |
