PRODUCTION OF GLASS GOB FOR FORMING OPTICAL ELEMENT

PROBLEM TO BE SOLVED: To efficiently produce a specified weight of glass gobs in a stable state even if the outflow speed of the molten glass from nozzles changes by controlling the slow descending speed of forming dies when the glass gobs are mass produced by using an index table. SOLUTION: The index table is provided with the plural forming dies 1 and the nozzles 2 to supply the molten glass G to the forming sections 1a of the forming dies 1 are arranged in a prescribed positions. The molten glass G flowing down from the nozzle 2 is photographed by a television camera 12 and the outflow speed of the molten glass G is detected from the glass occupying area within the measurement area of its image. At least the timing to start the slow descending from the uppermost position of the forming die 1 or the timing to start the slow descending and the slow descending speed are controlled, by which the weight of the molten glass G substantially supplied to the forming die 1 is prevented from changing even if the outflow rate of the molten glass G changes.