| 摘要 |
A method for making preforms for use in a glass lens molding process and molding lenses is disclosed. A glass rod is formed preferably by dipping a bob into a homogeneous melt of a predetermined optical glass, maintaining the temperature of the homogeneous melt at least the melt temperature and producing a rod of glass from the homogeneous melt, allowing the rod of glass to cool and solidify, and then cutting the rod of glass into predetermined lengths. By withdrawing the bob at a predetermined pull rate the rod of glass can be produced with a predetermined diameter. Using a constant pull rate, the rod of glass will be cylindrical in shape and can be cut into a series of individual cylindrical preforms. The preforms can be inserted into a compression molding apparatus for the forming of a glass optical element therewith. The orientation of the preform is such that the cut planar surfaces of the preform are parallel to the direction of compression of the molding process. The preforms formed by the process exhibit both good surface quality and good internal quality. Orientation of the preform with the cut surfaces parallel to the direction of compression in the final compression molding operation ensures that the optical quality surface of the preform formed by surface tension will be the optical surface of the lens formed therewith and the cut or sawed surfaces of the preform will make up the periphery of the final lens.
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