Patent ID: 7437893

Claim:
A manufacturing method of an optical glass comprising steps of: introducing a glass source material gas, a doped gas, an inflammable gas, a combustion-supporting gas, and an inert gas into a burner for glass synthesis; synthesizing glass particles by making the glass source material gas undergo a hydrolysis reaction or an oxidizing reaction in a flame; and depositing these glass particles onto a starting material; wherein a number of residual bubbles with a diameter of 0.3 mm and more is limited to 0.005/cm 3 or less per unit volume of the optical glass by controlling the temperature of an end face of said burner for glass synthesis during the deposition of said glass particles by regulating the flow velocity of said inflammable gas and said combustion-supporting gas such that the flow velocity of said inflammable gas is less than the flow velocity of said combustion-supporting gas.