| 摘要 |
PURPOSE:To form an optical element while controlling the press pressure continuously or stepwise by press-forming the element with the relatively low pressure at an initial stage where the temp. distribution is not sufficiently uniformized and press-forming the element at the increased pressure when the entire vitreous raw material is uniformly heated. CONSTITUTION:The vitreous raw material 1 preheated to a specified temp. is introduced between the upper and lower dies 2 and 3 heated to a glass forming temp. and opened and placed on the forming surfaces of the dies 2 and 3. The dies 2 and 3 are then closed, an initial press pressure is exerted until the internal temp. of the vitreous raw material 1 to be heated and soaked is heated to a glass forming temp., and the press pressure is then increased to form the material 1 into a desired shape. The formed article is then cooled to a specified temp. while the dies 2 and 3 are closed, and then the dies 2 and 3 are opened to discharge the formed article.
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