| 摘要 |
PURPOSE:To make it possible to form an optical element having a high accuracy, by forming an annular protrusion and annular groove adjacent to the outer periphery thereof on the tip end of a drum mold for forming a cavity and separating burrs produced in forming from a material in the cavity. CONSTITUTION:A material 10 for forming an optical element is filled in a cavity of a bottom force 9 formed from a drum mold 13 and a top force 8 is lowered through a pressurizing rod 12 from above until the undersurface (8a) thereof is engaged with the tip end of the above-mentioned drum mold 13 to form an optical element 11 having a given surface formed by the above- mentioned undersurface (8a) and the top surface (9a) of the top force 9. In the forming mold of the above-mentioned construction, an annular groove 14 is formed along the opening brim of the cavity on the tip end of the above- mentioned drum mold 13 and an annular groove 15 is formed along the outer periphery thereof. The thickness at the tip of the above-mentioned annular groove 14 is preferably <=0.5mm. Thereby the excess material 16, e.g. burrs, etc., produced in forming is separated and cast into the above-mentioned annular groove 15 to afford the aimed optical element 11 of high accuracy.
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