| 摘要 |
PURPOSE:To readily obtain an optical element, having optical surfaces with excellent surface properties without trapping gases, by placing a molding material having respective top and bottom surfaces formed into nonparallel and flat shapes between the top and bottom forces of a forming metallic mold, heating, pressurizing and molding the molding material. CONSTITUTION:For example, a round bar glass is initially cut into a form perpendicular to the longitudinal direction and then cut at some angle to provide a molding material 16 having respective top and bottom surfaces formed into mutual nonparallel and almost flat shapes. The resultant material 16 is then placed between the top and the bottom forces 11 and 12 of a forming metallic mold consisting of the top force 11 and bottom force 12 having press working surfaces (11a) and (12a) with a high degree of surface accuracy and a drum mold 13 in an annular form and the top force 11 is pressurized with a pressurizing rod 14 to start deformation of the material 16 at the thickest peripheral parts 19 and 20 and then continuously press mold the material gradually to thinner parts. Gases 17 and 17' between the material 16 and the top and the bottom forces 11 and 12 are gradually driven away to the thin-walled parts of the material 16 and discharged to carry out press molding.
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