Abstract: A method of manufacturing glass melt and a method of manufacturing molded glass material by forming glass melt. In the method of manufacturing glass melt, the glass melt containing fluorine is prepared by melting glass raw materials and refining the resulting glass melt. The refining is conducted in a refining vat equipped with a flow inlet through which flows glass melt obtained by heating and melting the glass raw materials, and a flow outlet through which flows glass melt that has been refined, with the level of the glass melt being maintained in such a manner that the flow inlet and flow outlet remain beneath the surface of the glass melt and the glass melt does not contact external air. The method of manufacturing a molded glass material comprises the step of molding the glass melt produced by the above method.

Abstract: A method of manufacturing glass melt and a method of manufacturing molded glass material by forming glass melt. In the method of manufacturing glass melt, the glass melt containing fluorine is prepared by melting glass raw materials and refining the resulting glass melt. The refining is conducted in a refining vat equipped with a flow inlet through which flows glass melt obtained by heating and melting the glass raw materials, and a flow outlet through which flows glass melt that has been refined, with the level of the glass melt being maintained in such a manner that the flow inlet and flow outlet remain beneath the surface of the glass melt and the glass melt does not contact external air. The method of manufacturing a molded glass material comprises the step of molding the glass melt produced by the above method.

Abstract: A method of manufacturing glass melt, a method of manufacturing molded glass materials from glass melt, and a method of manufacturing optical elements. In the method of manufacturing glass melt, glass is melted or glass melt is caused to flow out while monitoring the level of the glass melt in a vessel having a cover over the top thereof; a light beam for monitoring is directed approximately perpendicularly to the glass melt surface from the exterior of the vessel through an opening provided in the cover; and the light beam reflecting off the glass melt surface is caused to exit through the opening and is detected outside the vessel to monitor the level of the glass melt surface. The method of manufacturing a molded glass material comprises the steps of causing glass melt manufactured by the above method to flow out, and molding the glass that flows out. In the method of manufacturing an optical element, a precision press molding preform manufactured by the above method is heated and precision press molded.