Press molding method for an optical element and apparatus therefor

Abstract

Molding is effected while pressing pressure is continuously or stepwise controlled so that at the initial stage in which the temperature distribution of a glass blank is not sufficiently uniformized, molding may be effected with relatively low pressing pessure and in a state in which the whole of the glass blank is uniformly increased in temperature, press molding may be effected with the pressing pressure increased. In a press molding apparatus for an optical element, during press molding, the glass blank is press-molded while the pressing pressure is continuously or stepwise varied so that at a temperature whereat the glass viscosity of the glass blank corresponds to 10.sup.21 -10.sup.11 poise, molding may be started with pressing pressure of 10 kg/cm.sup.2 -100 kg/cm.sup.2, and thereafter in a temperature range in which the glass viscosity x of the central portion of the glass blank corresponds to 10.sup.11 -10.sup.10 poise, pressing pressure in the range of 10.times.(10.sup.11-x)-100+10.times.(10.sup.11-x) kg/cm.sup.2 may be applied, and further at a temperature whereat the glass viscosity corresponds to 10.sup.10 or less, pressing pressure of 100 kg/cm.sup.2 or greater may be applied.

Dependencies are inferred from the claim text.