Molding method for producing optical glass element

DETAILED DESCRIPTION An object of the present invention is to produce an optical glass element at a low cost.
Another object of the present invention is to produce an optical glass element having high surface quality and high surface accuracy.
That is, the object of the present invention is to produce an optical glass element having high surface quality and high surface accuracy at a low cost.
Still another object of the present invention is to provide a mold by which optical glass can be molded into the form of an optical glass element having high surface quality and high surface accuracy.
A further object of the present invention is to provide an optical glass element which is molded into a desired shape, which has high surface quality and high surface accuracy, and which is produced at a low cost.
Such objects as described above can be attained by the molding method according to the present invention, in which optical glass is heated and pressed by using a mold coated with a thin film of a noble metal alloy and molded into an optical glass element having a desired shape.
The molding method for producing an optical glass element comprises the steps of (1) preparing a block of optical glass softened by preheating, (2) hot-pressing the softened optical glass block by using a mold coated with a thin film of noble metal alloy to thereby mold the optical glass block in the form of an optical glass element having a desired shape, (3) cooling the optical glass element at a temperature not higher than an annealing temperature of the optical glass under the condition that the optical glass element is held in the mold, and (4) taking out the optical glass element from the mold.
The use of a mold for producing the optical glass element having a high surface quality and high surface accuracy is especially important in molding the optical glass.
It is known that if melted and softened optical glass is molded by a mold, the surface texture of the mold is accurately copied on the surface of the resultant optical glass element