Abstract: A crystallization method includes the steps of producing a purified article made of a material as crystalloid by mixing with scavenger, melting, and then solidifying the material, inspecting an amount of remaining oxygen contained in the purified article, and melting the purified article selected by the inspecting step, and then growing crystal from the purified article.

Abstract: Disclosed is a method of producing fluoride crystal, wherein the method includes a dehydrating step for dehydrating a raw material of fluoride by heating a crucible being adapted to accommodate a raw material of fluoride therein and having an exhaust mechanism for exhausting an inside gas of the crucible, and a exhausting step for exhausting, in the dehydrating step, an inside gas of the crucible by use of the exhaust mechanism.

Abstract: A method of pressing flowing-down molten glass from the opposite sides thereof by a pair of shaping mold members to thereby manufacture a glass optical part having surfaces corresponding to the shaping surfaces of the mold members is characterized in that a groove forming ring is provided around the shaping surface of at least one of the shaping mold members, a groove is formed in the molten glass by the groove forming ring during the press and the flowing-down molten glass is cut above that portion thereof which is being pressed, thereby obtaining a glass molded article having an ear protruding outwardly of the groove relative to an optical part body portion.

Abstract: Disclosed is a glass molding process using an apparatus for manufacturing a glass preform into a glass molded product. In the process a mold is prepared for pressing the glass preform. The mold consists of a pair of molds having a cavity surface for forming the glass molded product, and a frame mold which is movable against the pair of molds and incorporates a heating source. A next step in the process involves introducing the glass preform, where the pair of molds are opened and the glass preform is placed on the cavity surface. The glass preform then undergoes heating, where the glass preform is moved so as to come near the heating source of the frame mold by closing the mold, thereby heating the glass preform. The glass preform is then pressed by moving the mold to mold a shape of a glass molded product. The resulting glass molded product is then separated from the heating source by moving the frame mold and taken out by opening the mold.

Abstract: A lens is manufactured by preparing a glass material, preparing a molding apparatus for pressmolding the glass material into a lens shape, preheating the glass material or heating the glass material in the molding apparatus to soften the glass material and molding the glass material into the lens shape by the molding apparatus. An engagement portion of the molded lens to a member on which the lens is to be mounted is molded in the molding process simultaneously with the molding of an optically function portion of the lens.

Abstract: Disclosed is a glass blank used in a producing process for molding an optical element by heating a glass material and press molding the glass material in a mold having optical functional surfaces. Employed is the glass blank having the glass surface coated with a reaction preventive layer and a hydrocarbon layer or with the hydrocarbon layer.