Before glass mold molding was established, lenses were very expensive due to the need for high-precision grinding and polishing techniques. Currently, aspherical lenses are manufactured by glass molding from the viewpoints of cost and mass production.

The glass preform is fed between the upper and lower molds, heated to a temperature at which the glass can be deformed, and pressure is applied to transfer the mold shape (aspherical shape) onto the glass, which is then cooled and the lens is ejected.