Mold for molding optical elements

Abstract

A mold arranged between a pair of heater blocks for molding an optical element comprises a pair of first and second elements each having a molding surface for defining a cavity and an outer surface opposite to the molding surface and in contact with a corresponding heater block, and a ring member for guiding the first and second elements. The rear surface of at least one of the first and second elements has a part which is not in contact with the corresponding heater block. Also, another mold comprises a pair of first and second elements each having a molding surface for defining a cavity and an outer surface opposite to the molding surface, a first ring member for guiding the first and second elements, and a second outer ring member made of a material with a lower thermal conductivity than that of the first ring member. A molding method for optical elements is such that a glass with a viscosity of 10.sup.12 poise or more is fed to a mold with a temperature at or below the glass transition point, heated to a temperature corresponding to the glass viscosity of 10.sup.8 to 10.sup.10 poise and pressed for 3 to 90 seconds. The glass is then cooled at a rate of 1.5.degree. to 2.5.degree. C./sec to a viscosity of 10.sup.10 to 10.sup.11 poise and thereafter at a rate of 0.2.degree. to 1.5.degree. C./sec with the glass pressurized, and removed as an optical element at or below the glass transition point.