Method of manufacturing optical device

A manufacturing method of molding an optical device having an accurate optical surface, comprising the sequential steps of:

• preparing a pre-molded glass preform;
• preparing a die member to mold said glass preform into the optical device;
• transporting said glass preform and said die member to a heating section and heating to a temperature necessary to mold,
• adhering a gaseous mixture of a nonoxidizing gas and a hydrocarbon gas onto the surface of said glass preform, said hydrocarbon gas being present in a concentration 0.5-4 wt. % of said gaseous mixture.
• transporting said glass preform and said die member to a pressing section for press-molding said glass preform into an optical device;
• and
• transporting said die member and said optical device to a cooling section for cooling said optical device to a temperature sufficient to separate said mold member from said optical device.

A manufacturing method of molding an optical device having an accurate optical surface, comprising the steps of:

• preparing a pre-molded glass preform;
• preparing a die member to mold said glass preform into said optical device,
• said die member having at least an upper die and a lower die for molding said optical surface in order to press-mold said glass preform, and said die member being made of a material resistant to oxidation and high temperature, and having a high hardness property;
• simultaneously heating said glass preform and said die member to a temperature necessary to mold;
• inserting said glass preform between said upper die and said lower die;
• and
• press-molding said glass preform between said upper die and said lower die in an operating atmosphere of a PG,41 gaseous mixture of a nonoxidizing gas and a hydrocarbon gas, said hydrocarbon gas being present in a concentration of 0.5 to 4 wt. % of said gaseous mixture.